This research was supported by the DZHK (German Centre for Cardiovascular Research, D.B.), the EKFS (Else-Kr&#246;ner-Fresenius Stiftung, F.H.), and by the BMBF (German Ministry of Education and Research), as well as the BIH-Charit&#233; clinical scientist program funded by the Charit&#233; - Universit&#228;tsmedizin Berlin and the Berlin Institute of Health (F.H.).

<ol>
	<li>Alberti, K. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Harmonizing+the+metabolic+syndrome:+a+joint+interim+statement+of+the+International+Diabetes+Federation+Task+Force+on+Epidemiology+and+Prevention;+National+Heart,+Lung,+and+Blood+Institute;+American+Heart+Association;+World+Heart+Federation;+International+Atherosclerosis+Society;+and+International+Association+for+the+Study+of+Obesity.">Harmonizing the metabolic syndrome: a joint interim statement of the International Diabetes Federation Task Force on Epidemiology and Prevention; National Heart, Lung, and Blood Institute; American Heart Association; World Heart Federation; International Atherosclerosis Society; and International Association for the Study of Obesity.</a> Circulation. 120 (16), 1640-1645 (2009).</li><li>. IDF Consensus Worldwide Definition of the Metabolic Syndrome Available from: <a target="_blank" href="https://www.idf.org/e-library/consensus-statements/60-idfconsensus-worldwide-definitionof-the-metabolic-syndrome.html">https://www.idf.org/e-library/consensus-statements/60-idfconsensus-worldwide-definitionof-the-metabolic-syndrome.html</a> (2006)</li><li>Melenovsky, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Left+atrial+remodeling+and+function+in+advanced+heart+failure+with+preserved+or+reduced+ejection+fraction.">Left atrial remodeling and function in advanced heart failure with preserved or reduced ejection fraction.</a> Circulation: Heart Failure. 8 (2), 295-303 (2015).</li><li>Goette, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EHRA/HRS/APHRS/SOLAECE+expert+consensus+on+atrial+cardiomyopathies:+definition,+characterization,+and+clinical+implication.">EHRA/HRS/APHRS/SOLAECE expert consensus on atrial cardiomyopathies: definition, characterization, and clinical implication.</a> EP Europace. 18 (10), 1455-1490 (2016).</li><li>Schotten, U., Verheule, S., Kirchhof, P., Goette, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pathophysiological+mechanisms+of+atrial+fibrillation:+a+translational+appraisal.">Pathophysiological mechanisms of atrial fibrillation: a translational appraisal.</a> Physiological Reviews. 91 (1), 265-325 (2011).</li><li>Hohendanner, F., DeSantiago, J., Heinzel, F. R., Blatter, L. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dyssynchronous+calcium+removal+in+heart+failure-induced+atrial+remodeling.">Dyssynchronous calcium removal in heart failure-induced atrial remodeling.</a> American Journal of Physiology-Heart and Circulatory Physiology. 311 (6), H1352-H1359 (2016).</li><li>Hohendanner, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inositol-1,4,5-trisphosphate+induced+Ca2++release+and+excitation-contraction+coupling+in+atrial+myocytes+from+normal+and+failing+hearts.">Inositol-1,4,5-trisphosphate induced Ca2+ release and excitation-contraction coupling in atrial myocytes from normal and failing hearts.</a> The Journal of Physiology. 593 (6), 1459-1477 (2015).</li><li>Tada, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+mineralocorticoid+receptor+on+experimental+cerebral+aneurysms+in+rats.">Role of mineralocorticoid receptor on experimental cerebral aneurysms in rats.</a> Hypertension. 54 (3), 552-557 (2009).</li><li>Iwasaki, Y. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atrial+fibrillation+promotion+with+long-term+repetitive+obstructive+sleep+apnea+in+a+rat+model.">Atrial fibrillation promotion with long-term repetitive obstructive sleep apnea in a rat model.</a> Journal of the American College of Cardiology. 64 (19), 2013-2023 (2014).</li><li>Field, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atrial+natriuretic+factor-SV40+T+antigen+transgenes+produce+tumors+and+cardiac+arrhythmias+in+mice.">Atrial natriuretic factor-SV40 T antigen transgenes produce tumors and cardiac arrhythmias in mice.</a> Science. 239 (4843), 1029-1033 (1988).</li><li>Claycomb, W. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HL-1+cells:+a+cardiac+muscle+cell+line+that+contracts+and+retains+phenotypic+characteristics+of+the+adult+cardiomyocyte.">HL-1 cells: a cardiac muscle cell line that contracts and retains phenotypic characteristics of the adult cardiomyocyte.</a> Proceedings of the National Academy of Sciences of the United States of America. 95 (6), 2979-2984 (1998).</li><li>Sartiani, L., Bochet, P., Cerbai, E., Mugelli, A., Fischmeister, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+expression+of+the+hyperpolarization-activated,+non-selective+cation+current+I(f)+in+immortalized+HL-1+cardiomyocytes.">Functional expression of the hyperpolarization-activated, non-selective cation current I(f) in immortalized HL-1 cardiomyocytes.</a> The Journal of Physiology. 545 (Pt 1), 81-92 (2002).</li><li>Louch, W. E., Sheehan, K. A., Wolska, B. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+in+cardiomyocyte+isolation,+culture,+and+gene+transfer.">Methods in cardiomyocyte isolation, culture, and gene transfer.</a> Journal of Molecular and Cellular Cardiology. 51 (3), 288-298 (2011).</li><li>Gunduz, D., Hamm, C. W., Aslam, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+Isolation+of+High+Quality+Cardiomyocytes,+Endothelial+Cells,+and+Fibroblasts+from+an+Adult+Rat+Heart.">Simultaneous Isolation of High Quality Cardiomyocytes, Endothelial Cells, and Fibroblasts from an Adult Rat Heart.</a> Journal of Visualized Experiments. (123), e55601 (2017).</li><li>Li, D., Wu, J., Bai, Y., Zhao, X., Liu, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+culture+of+adult+mouse+cardiomyocytes+for+cell+signaling+and+in+vitro+cardiac+hypertrophy.">Isolation and culture of adult mouse cardiomyocytes for cell signaling and in vitro cardiac hypertrophy.</a> Journal of Visualized Experiments. (87), e51357 (2014).</li><li>Graham, E. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation,+culture,+and+functional+characterization+of+adult+mouse+cardiomyoctyes.">Isolation, culture, and functional characterization of adult mouse cardiomyoctyes.</a> Journal of Visualized Experiments. (79), e50289 (2013).</li><li>Roth, G. M., Bader, D. M., Pfaltzgraff, E. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+physiological+analysis+of+mouse+cardiomyocytes.">Isolation and physiological analysis of mouse cardiomyocytes.</a> Journal of Visualized Experiments. (91), e51109 (2014).</li><li>Thum, T., Borlak, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+cultivation+of+Ca2++tolerant+cardiomyocytes+from+the+adult+rat:+improvements+and+applications.">Isolation and cultivation of Ca2+ tolerant cardiomyocytes from the adult rat: improvements and applications.</a> Xenobiotica. 30 (11), 1063-1077 (2000).</li><li>Egorova, M. V., Afanas'ev, S. A., Popov, S. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simple+method+for+isolation+of+cardiomyocytes+from+adult+rat+heart.">A simple method for isolation of cardiomyocytes from adult rat heart.</a> Bulletin of Experimental Biology and Medicine. 140 (3), 370-373 (2005).</li><li>Kohncke, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+Kv+channel+recordings+in+murine+atrial+and+ventricular+cardiomyocytes.">Isolation and Kv channel recordings in murine atrial and ventricular cardiomyocytes.</a> Journal of Visualized Experiments. (73), e50145 (2013).</li><li>Wagner, E., Brandenburg, S., Kohl, T., Lehnart, S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+tubular+membrane+networks+in+cardiac+myocytes+from+atria+and+ventricles.">Analysis of tubular membrane networks in cardiac myocytes from atria and ventricles.</a> Journal of Visualized Experiments. (92), e51823 (2014).</li><li>Hohendanner, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+mechanisms+of+metabolic+syndrome-related+atrial+decompensation+in+a+rat+model+of+HFpEF.">Cellular mechanisms of metabolic syndrome-related atrial decompensation in a rat model of HFpEF.</a> Journal of Molecular and Cellular Cardiology. 115, 10-19 (2017).</li><li>Seluanov, A., Vaidya, A., Gorbunova, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Establishing+primary+adult+fibroblast+cultures+from+rodents.">Establishing primary adult fibroblast cultures from rodents.</a> Journal of Visualized Experiments. (44), e2033 (2010).</li><li>Bootman, M. D., Higazi, D. R., Coombes, S., Roderick, H. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calcium+signalling+during+excitation-contraction+coupling+in+mammalian+atrial+myocytes.">Calcium signalling during excitation-contraction coupling in mammalian atrial myocytes.</a> Journal of Cell Science. 119 (Pt 19), 3915-3925 (2006).</li><li>Smyrnias, I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+the+T-tubule+system+in+adult+rat+ventricular+and+atrial+myocytes,+and+its+role+in+excitation-contraction+coupling+and+inotropic+stimulation.">Comparison of the T-tubule system in adult rat ventricular and atrial myocytes, and its role in excitation-contraction coupling and inotropic stimulation.</a> Cell Calcium. 47 (3), 210-223 (2010).</li><li>Pritchett, A. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diastolic+dysfunction+and+left+atrial+volume:+a+population-based+study.">Diastolic dysfunction and left atrial volume: a population-based study.</a> Journal of the American College of Cardiology. 45 (1), 87-92 (2005).</li><li>Linz, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cathepsin+A+mediates+susceptibility+to+atrial+tachyarrhythmia+and+impairment+of+atrial+emptying+function+in+Zucker+diabetic+fatty+rats.">Cathepsin A mediates susceptibility to atrial tachyarrhythmia and impairment of atrial emptying function in Zucker diabetic fatty rats.</a> Cardiovascular Research. 110 (3), 371-380 (2016).</li><li>Ackers-Johnson, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Simplified,+Langendorff-Free+Method+for+Concomitant+Isolation+of+Viable+Cardiac+Myocytes+and+Nonmyocytes+From+the+Adult+Mouse+Heart.">A Simplified, Langendorff-Free Method for Concomitant Isolation of Viable Cardiac Myocytes and Nonmyocytes From the Adult Mouse Heart.</a> Circulation Research. 119 (8), 909-920 (2016).</li><li>Ramanathan, T., Skinner, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coronary+blood+flow.">Coronary blood flow.</a> Continuing Education in Anaesthesia Critical Care &amp; Pain. 5 (2), 61-64 (2005).</li><li>Bond, M. D., Van Wart, H. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+the+individual+collagenases+from+Clostridium+histolyticum.">Characterization of the individual collagenases from Clostridium histolyticum.</a> Biochemistry. 23 (13), 3085-3091 (1984).</li><li>Deel, E. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+model+to+study+the+effects+of+matrix+stiffening+on+Ca(2+)+handling+and+myofilament+function+in+isolated+adult+rat+cardiomyocytes.">In vitro model to study the effects of matrix stiffening on Ca(2+) handling and myofilament function in isolated adult rat cardiomyocytes.</a> The Journal of Physiology. 595 (14), 4597-4610 (2017).</li><li>Wuensch, E., Heidrich, H. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=[On+the+Quantitative+Determination+of+Collagenase].">[On the Quantitative Determination of Collagenase].</a> Hoppe-Seyler's Zeitschrift f&#252;r physiologische Chemie. 333, 149-151 (1963).</li><li>Conceicao, G., Heinonen, I., Lourenco, A. P., Duncker, D. J., Falcao-Pires, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+heart+failure+with+preserved+ejection+fraction.">Animal models of heart failure with preserved ejection fraction.</a> Netherlands Heart Journal. 24 (4), 275-286 (2016).</li><li>Horgan, S., Watson, C., Glezeva, N., Baugh, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Murine+models+of+diastolic+dysfunction+and+heart+failure+with+preserved+ejection+fraction.">Murine models of diastolic dysfunction and heart failure with preserved ejection fraction.</a> Journal of Cardiac Failure. 20 (12), 984-995 (2014).</li></ol>

The authors have nothing to disclose.

Here, we first described a protocol for the isolation of single-cell ACMs from a rat model of MetS-related HFpEF that shows marked atrial remodeling22. The procedure is uniquely challenging as excessive fatty tissue can make the surgical preparation, as well as the cannulation of the aorta, increasingly difficult. The troubleshooting guide provided in Table 2 addresses the most common issues of the isolation procedure.
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Problem</td>
			<td>Possible Cause</td>
			<td>Solution</td>
		</tr>
		<tr>
			<td>No flow through butterfly hose</td>
			<td>Improper closure of the aorta with the cannulation knots</td>
			<td>Remove fatty tissue before tightening</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td>Add 3rd cannulation knot with respective indentation</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td>Pull knot with hand for increased force</td>
		</tr>
		<tr>
			<td></td>
			<td>Blocked needle</td>
			<td>Readjust position into the lumen</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td>Unblock by gentle pull with syringe</td>
		</tr>
		<tr>
			<td>Right atrium / coronary sinus not inflated</td>
			<td>Improper closure of the heart base</td>
			<td>Block flow with additional knots</td>
		</tr>
		<tr>
			<td></td>
			<td>Right atrium damaged during preparation</td>
			<td>Close leakage with clips/knots</td>
		</tr>
		<tr>
			<td>Poor digestion / atrium does not soften</td>
			<td>Reduced enzyme activity through wrong temperature</td>
			<td>Adjust temperature to 37 &#176;C</td>
		</tr>
		<tr>
			<td></td>
			<td>Inactive/degraded enzyme</td>
			<td>Replace</td>
		</tr>
		<tr>
			<td></td>
			<td>Old/overly fibrotic atrium</td>
			<td>Increase digestion time (in steps of +50%)</td>
		</tr>
		<tr>
			<td></td>
			<td>Damaged aortic valve</td>
			<td>Shallow penetration during cannulation</td>
		</tr>
		<tr>
			<td>Poor cell yield</td>
			<td>Atrium over-digested</td>
			<td>Decrease digestion time (in steps of +25%)</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td>Reduce intraluminal pressure by lowering the butterfly hose</td>
		</tr>
		<tr>
			<td></td>
			<td>Atrium under-digested</td>
			<td>Increase digestion time (in steps of 25%)</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td>Increase intraluminal pressure by raising the butterfly hose</td>
		</tr>
		<tr>
			<td></td>
			<td>Cell dispersion too aggressive</td>
			<td>Be more gentle</td>
		</tr>
	</tbody>
</table>
Table 2: Troubleshooting guide. This table displays common issues of the isolation procedure and their respective solutions.
In a recent study, we have shown that the ZFS-1 obese rat model exhibits extensive atrial remodeling with an increased atrial size22. An increase in the left atrial size has been recognized as an important prognostic marker for diastolic dysfunction26 and causes a rarefication of the microvascular vessels relative to the tissue. This leads to a decreased distribution of the digestive buffer through the retrograde perfusion of the aorta during the isolation procedure, rendering the single-cell isolation in this model especially challenging. Other hallmark features of atrial remodeling, atrial fibrosis, and increased fibrosis have been shown for ZDF rats&#8212;a rat model for metabolic diabetes and one parent strain of the ZFS1 rats27. Collagen deposits impair the efficacy of the digestive enzymes to liberate the cardiomyocytes from the extracellular matrix and, therefore, require further adjustments of the cell isolation procedure28.
The mechanism by which the pressure device facilitates the improved isolation results in this model of atrial remodeling is most likely related to a localized attenuation of the coronary blood flow of the left atrium. One major component of the coronary blood flow is coronary perfusion pressure, which is defined as the gradient between the coronary artery pressure and the end-diastolic pressure of the respective cavity29. During the described procedure, a blockage of the heart base leads to a global increase in coronary artery pressure and intraluminal pressure throughout the heart. The subsequent puncture of the left atrium facilitates a local, selective drop of intraluminal pressure in the left atrial cavity. Thus, not only a large coronary perfusion pressure gradient is established, but the perfusion volume is also increased by the diverted digestion solution from the congested left ventricle to the left atrium.
In addition, the choice of digestion enzymes is crucial for the ACM isolation: purified enzyme blends of collagenase I and II have been shown to be superior to less targeted and less pure enzymes like collagenases30. This enzyme does not only allow for a higher yield of morphologically and functionally intact cardiomyocytes but also minimizes any clumping of single cells after their isolation31. Purified enzyme blends of collagenases with an additional high dispase or medium thermolysin content are most commonly used for rat cardiomyocyte isolations. While VCMs are best isolated at higher concentrations, the best results of atrial myocytes were acquired with a concentration of 0.195 W&#252;nsch Units/mL using this protocol32.
As the prevalence of MetS-related HFpEF is rising2 and atrial cardiomyopathies leading to atrial remodeling and atrial fibrillation are clinically highly relevant, research in this field is of pivotal interest. Many new animal models for HFpEF are emerging33,34 and atrial remodeling in line with an increased incidence of atrial rhythm disorders are hallmark features of the disease. The described method allows researchers to isolate viable single cardiomyocytes from rat models with atrial remodeling for a further study with an exceptionally high yield and preserved mechanical and electrical function.

MetS describes a cluster of risk factors for diabetes mellitus type-2 and cardiovascular disease and includes an increased arterial blood pressure, dyslipidemia (raised triglycerides and lowered high-density lipoprotein cholesterol), increased fasting glucose, and central obesity1. The worldwide prevalence of MetS is estimated to be 25&#8211;30% and constantly rising2. HFpEF is a heterogenous clinical syndrome often associated with MetS. The cardiac remodeling during HFpEF and its preceding phases (i.e., hypertensive heart disease) is also accompanied by a remodeling of the atria3. Reduced contractile function and structural changes of the left atrium have been associated with increased mortality, atrial fibrillation, and new-onset heart failure4. Atrial remodeling is characterized by changes in the ion channel function, Ca2+ homeostasis, atrial structure, fibroblast activation, and tissue fibrosis5. Left atrial remodeling in MetS-related HFpEF and its underlying pathological mechanisms are still poorly understood and require a further in-depth investigation. Animal models have proven to be a valuable tool and lead to many advances in the field of atrial cardiomyopathies6,7,8,9.
Studies with isolated single-cell cardiomyocytes are frequently used to corroborate and complement in vivo findings. An isolation, and the potential subsequent cell culture, allow for the investigation of signaling pathways, ionic channel currents, and excitation-contraction-coupling. Under physiologic conditions, cardiomyocytes do not proliferate. The fusion between the transcriptional regulatory sequences of an atrial natriuretic factor and a simian virus 40 large T antigen in transgenic mice led to the creation of the first immortalized ACMs, named AT-110. The further development of AT-1 cells gave rise to HL-1 cells, which cannot only be serially passaged but also contract spontaneously11. They do, however, show structural and functional differences compared to freshly isolated cells, such as a less organized ultrastructure, a high occurrence of developing myofibrils11, and a hyperpolarization-activated inward current12. The isolation of ventricular cardiomyocytes (VCM) in rats and mice from a variety of models is well established13,14,15,16,17,18,19. Generally, the excised heart is mounted to a Langendorff apparatus and retrogradely perfused with a Ca2+-free buffer containing digestive enzymes, such as collagenases and proteases. Calcium is then reintroduced in a stepwise manner to the physiological conditions. However, even though protocols dedicated to the isolation of ACMs are available20,21, due to increased fibrosis and pressure-related differences, their usefulness in disease models with atrial remodeling is limited.
In this article, we have implemented a protocol for the isolation of atrial single-cell cardiomyocytes from animals that show atrial remodeling (i.e., in particular for the ZFS1 rat model for MetS-related HFpEF)22. Existing isolation protocols were optimized and complemented by a simple, custom-made device to control and modify the intraluminal pressure of the cardiac cavities, leading to higher yields of morphologically and functionally intact cardiomyocytes. The following protocol provides the researcher with a step-by-step guide, a detailed description of the custom-made equipment, a list of solutions, as well as a comprehensive troubleshooting guide.

<table border="0" cellpadding="0" cellspacing="0" width="935">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">ZSF-1 Obese rat</td>
			<td style="width:292px;">Charles River Laboratories, Inc.</td>
			<td style="width:136px;"></td>
			<td style="width:227px;">21 weeks old</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Fine Iris Scissors</td>
			<td style="width:292px;">Fine Science Tools GmbH</td>
			<td style="width:136px;">14094-11</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Surgical Scissors</td>
			<td style="width:292px;">Fine Science Tools GmbH</td>
			<td style="width:136px;">14001-18</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Micro Dressing Forceps (curved, serrated)</td>
			<td style="width:292px;">Aesculap, Inc.</td>
			<td style="width:136px;">BD312R</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Tissue Forceps (straight, 1 x 2 teeth)</td>
			<td style="width:292px;">Aesculap, Inc.</td>
			<td style="width:136px;">BD537R</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Tying Forceps (angled)</td>
			<td style="width:292px;">Aesculap, Inc.</td>
			<td style="width:136px;">MA624R</td>
			<td></td>
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		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Rodent and Small Animal Guillotine</td>
			<td style="width:292px;">Kent Scientific Corp.</td>
			<td style="width:136px;">DCAP</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Low Cost Induction Chamber 3.0 L</td>
			<td style="width:292px;">Kent Scientific Corp.</td>
			<td style="width:136px;">SOMNO-0730&#160;</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Butterfly Winged Infusion Set 21 G</td>
			<td style="width:292px;">Hospira, Inc.</td>
			<td style="width:136px;">181106101</td>
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		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Abbocath 16 G</td>
			<td style="width:292px;">Hospira, Inc.</td>
			<td>0G7149702</td>
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		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Microlance Hypodermic Needle</td>
			<td style="width:292px;">Becton Dickinson GmbH</td>
			<td style="width:136px;">301300</td>
			<td>modify needle to make cannula</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Braun Original Perfusor Syringe 50 ml</td>
			<td style="width:292px;">B. Braun Melsungen AG</td>
			<td style="width:136px;">8728810F</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Braun Inject Solo Syringe 10 ml</td>
			<td style="width:292px;">B. Braun Melsungen AG</td>
			<td style="width:136px;">2057926</td>
			<td></td>
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		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Beaker 50ml</td>
			<td style="width:292px;">Duran Group (DWK Life Sciences GmbH)</td>
			<td>21 106 17</td>
			<td></td>
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		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Duroplan petri dish (100 x 20 mm)</td>
			<td style="width:292px;">Duran Group (DWK Life Sciences GmbH)</td>
			<td style="width:136px;">21 755 48</td>
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		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Seraflex Suture USP 3/0</td>
			<td style="width:292px;">SERAG-WIESSNER GmbH &#38; Co. KG</td>
			<td style="width:136px;">IC208000</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">VWR disposable Square Weighin Boats 100ml</td>
			<td style="width:292px;">VWR, Inc.</td>
			<td style="width:136px;">10803-148</td>
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		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Styrofoam surface</td>
			<td style="width:292px;"></td>
			<td style="width:136px;"></td>
			<td></td>
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		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Sodium chloride</td>
			<td style="width:292px;">Sigma-Aldrich, Inc.</td>
			<td style="width:136px;">71380</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Potassium chloride</td>
			<td style="width:292px;">Sigma-Aldrich, Inc.</td>
			<td style="width:136px;">P4504</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Potassium phosphate monobasic</td>
			<td style="width:292px;">Sigma-Aldrich, Inc.</td>
			<td style="width:136px;">P5379</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Sodium phosphate dibasic</td>
			<td style="width:292px;">Sigma-Aldrich, Inc.</td>
			<td style="width:136px;">S0876</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Magensium sulfate heptahydrate</td>
			<td style="width:292px;">Sigma-Aldrich, Inc.</td>
			<td style="width:136px;">230391</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Magensium chloride</td>
			<td style="width:292px;">Sigma-Aldrich, Inc.</td>
			<td style="width:136px;">M8266</td>
			<td></td>
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		<tr height="20">
			<td height="20" style="height:20px;width:281px;">HEPES</td>
			<td style="width:292px;">Sigma-Aldrich, Inc.</td>
			<td style="width:136px;">H3375</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Taurine</td>
			<td style="width:292px;">Sigma-Aldrich, Inc.</td>
			<td style="width:136px;">T0625</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Glucose</td>
			<td style="width:292px;">Sigma-Aldrich, Inc.</td>
			<td style="width:136px;">G7528</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">2,3-Butanedione monoxime</td>
			<td style="width:292px;">Sigma-Aldrich, Inc.</td>
			<td style="width:136px;">B0753</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Calcium chloride solution (1 M)</td>
			<td style="width:292px;">Sigma-Aldrich, Inc.</td>
			<td style="width:136px;">21115</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Bovine Serum Albumin</td>
			<td style="width:292px;">Sigma-Aldrich, Inc.</td>
			<td style="width:136px;">A9647</td>
			<td style="width:227px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Liberase</td>
			<td style="width:292px;">Roche (Sigma-Aldrich, Inc.)</td>
			<td style="width:136px;">LIBTM-RO</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Heparin</td>
			<td style="width:292px;">Rotexmedica GmbH</td>
			<td style="width:136px;">3862357</td>
			<td></td>
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		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Forene (Isoflurane)</td>
			<td style="width:292px;">Abbvie Deutschland GmbH &#38; Co. KG</td>
			<td style="width:136px;">10182054</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Laminin from Engelbreth-Holm-Swarm murine sarcoma basement membrane</td>
			<td style="width:292px;">Sigma-Aldrich, Inc.</td>
			<td style="width:136px;">L2020</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">WillCo glass-bottom dish 500&#181;l 0.005mm</td>
			<td style="width:292px;">WillCo Wells B.V.</td>
			<td style="width:136px;">HBST-3522</td>
			<td></td>
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		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Fluo4 AM</td>
			<td style="width:292px;">Invitrogen (Thermo Fisher Scientific, Inc.)</td>
			<td>F14201</td>
			<td>5&#181;M for 20min at RT</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Di-8-ANNEPS</td>
			<td style="width:292px;">Invitrogen (Thermo Fisher Scientific, Inc.)</td>
			<td>D3167</td>
			<td>10&#181;M for 45 min at 37&#176; C&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Mitotracker RED FM</td>
			<td style="width:292px;">Invitrogen (Thermo Fisher Scientific, Inc.)</td>
			<td style="width:136px;">M22425</td>
			<td>20nM for 30 min at 37&#176; C</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Jacketed reaction vessel 500 ml</td>
			<td style="width:292px;">Gebr. Rettberg GmbH</td>
			<td>107024414</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Jacketed reaction vessel 1000 ml</td>
			<td style="width:292px;">Gebr. Rettberg GmbH</td>
			<td>107025414</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Jacketed bubble trap</td>
			<td style="width:292px;">Gebr. Rettberg GmbH</td>
			<td>134720001</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">ED heating immersion circulator</td>
			<td style="width:292px;">Julabo GmbH</td>
			<td>9116000</td>
			<td></td>
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		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Reglo Digital MS-2/6 peristaltic pump</td>
			<td style="width:292px;">Ismatec (Cole-Parmer Gmbh)</td>
			<td style="width:136px;">ISM 831</td>
			<td></td>
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		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Voltcraft Thermometer 302 K/J</td>
			<td style="width:292px;">Conrad Electronic SE</td>
			<td style="width:136px;">030300546</td>
			<td></td>
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		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Tubing</td>
			<td style="width:292px;"></td>
			<td style="width:136px;"></td>
			<td></td>
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		<tr height="20">
			<td height="20" style="height:20px;width:281px;">LSM 700 microscope</td>
			<td style="width:292px;">Carl Zeiss, Inc.</td>
			<td style="width:136px;"></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">ZEN 2.3 imaging software</td>
			<td style="width:292px;">Carl Zeiss, Inc.</td>
			<td style="width:136px;">410135-1011-240&#160;</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">Single channel heater controller TC-324B</td>
			<td style="width:292px;">Warner Instruments, LLC</td>
			<td style="width:136px;">64-2400</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">8 channel perfusion system</td>
			<td style="width:292px;">Warner Instruments, LLC</td>
			<td style="width:136px;">64-0185</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;width:281px;">8 channel Multi-Line In-Line Solution Heaters</td>
			<td style="width:292px;">Warner Instruments, LLC</td>
			<td style="width:136px;">64-0105</td>
			<td></td>
		</tr>
	</tbody>
</table>

isolation of atrial cardiomyocytes from a rat model of metabolic syndrome-related heart failure with preserved ejection fraction

In this article, we describe an optimized, Langendorff-based procedure for the isolation of single-cell atrial cardiomyocytes (ACMs) from a rat model of metabolic syndrome (MetS)-related heart failure with preserved ejection fraction (HFpEF). The prevalence of MetS-related HFpEF is rising, and atrial cardiomyopathies associated with atrial remodeling and atrial fibrillation are clinically highly relevant as atrial remodeling is an independent predictor of mortality. Studies with isolated single-cell cardiomyocytes are frequently used to corroborate and complement in vivo findings. Circulatory vessel rarefication and interstitial tissue fibrosis pose a potentially limiting factor for the successful single-cell isolation of ACMs from animal models of this disease.
We have addressed this issue by employing a device capable of manually regulating the intraluminal pressure of cardiac cavities during the isolation procedure, substantially increasing the yield of morphologically and functionally intact ACMs. The acquired cells can be used in a variety of different experiments, such as cell culture and functional Calcium imaging (i.e., excitation-contraction-coupling).
We provide the researcher with a step-by-step protocol, a list of optimized solutions, thorough instructions to prepare the necessary equipment, and a comprehensive troubleshooting guide. While the initial implementation of the procedure might be rather difficult, a successful adaptation will allow the reader to perform state-of-the-art ACM isolations in a rat model of MetS-related HFpEF for a broad spectrum of experiments.

At 21 weeks of age, 60&#8211;90% of viable ACMs (estimated as described in step 6.1), after the calcium re-adaptation (step 5.4&#8211;5.7), can be isolated from ZSF-1 obese rats by this method (Figure 4A). In rats, ACMs are characterized by a different and more heterogenous phenotype compared to VCMs24,25. Figure 4B shows an individual ACM with preserved membranes and sarcomere structure, both strong indicators of a functionally integral cell.
The acquired ACMs can be processed in a variety of ways. As exemplified in Figure 5, the cells might be loaded with fluorescent dyes used to study morphology and/or function. For instance, di-8-ANEPPS was used to delineate the tubular system in an atrial rat cell (Figure 5A). In another set of experiments, mitochondria-staining far red-fluorescence dye (e.g., mitotracker-Red-FM) is employed to detect cytosolic mitochondria (Figure 5B) in atrial remodeling. As shown in Figure 5C, ACMs isolated with this protocol are also suitable for live-cell Ca2+ imaging and show intact excitation-contraction coupling with a 1 Hz field-stimulation. All images can be used for further analysis using a variety of algorithms available to the researcher6,7 (Figure 5D).
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/57953/57953fig4.jpg" /> 
Figure 4: Respective yield of viable, single-cell AM. (A) This panel shows the yield of an isolation after the re-adaptation of ACMs to 1 mM Ca2+ in NT. (B) This panel shows an isolated, single-cell atrial cardiomyocyte. The sarcomere structure, cell membrane, and nucleus are clearly visible. <a href="https://www.jove.com/files/ftp_upload/57953/57953fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/57953/57953fig5.jpg" /> 
Figure 5: Staining of rat ACMs with fluorescent dyes. (A) This panel shows the staining of a cell membrane and tubular network with the fluorescent dye Di8ANNEPS. (B) This panel shows the staining of mitochondria with the fluorescent dye mitotracker-Red-FM. (C) This panel shows the transversal line scan of a Ca2+-excitation with the fluorescent dye Fluo4-AM over a single cell. The arrows indicate the electrical stimulation, conducted at 1 Hz. (D) This panel shows the longitudenal Ca2+ transients derived from panel C. <a href="https://www.jove.com/files/ftp_upload/57953/57953fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Isolation of Atrial Cardiomyocytes from a Rat Model of Metabolic Syndrome-related Heart Failure with Preserved Ejection Fraction at JoVE.com

Isolation of Atrial Cardiomyocytes from a Rat Model of Metabolic Syndrome-related Heart Failure with Preserved Ejection Fraction

Here, we describe an optimized, Langendorff-based procedure for the isolation of single-cell atrial cardiomyocytes from a rat model of metabolic syndrome-related heart failure with preserved ejection fraction. A manual regulation of intraluminal pressure of cardiac cavities is implemented to yield functionally intact myocytes suitable for excitation-contraction-coupling studies.

In this article, we describe an optimized, Langendorff-based procedure for the isolation of single-cell atrial cardiomyocytes (ACMs) from a rat model of ...

isolation-atrial-cardiomyocytes-from-rat-model-metabolic-syndrome

Nanyang Technological University

Research

JoVE Journal

Medicine

10.0K Views.  Charité University Medicine. Here, we describe an optimized, Langendorff-based procedure for the isolation of single-cell atrial cardiomyocytes from a rat model of metabolic syndrome-related heart failure with preserved ejection fraction. A manual regulation of intraluminal pressure of cardiac cavities is implemented to yield functionally intact myocytes suitable for excitation-contraction-coupling studies.

Video: Isolation of Atrial Cardiomyocytes from a Rat Model of Metabolic Syndrome-related Heart Failure with Preserved Ejection Fraction

Gene Transfer for Ischemic Heart Failure in a Preclinical Model

Various emerging technologies are being developed for patients with heart failure. Well-established preclinical evaluations are necessary to determine their efficacy and safety.
Gene therapy using viral vectors is one of the most promising approaches for treating cardiac diseases. Viral delivery of various different genes by changing the carrier gene has immeasurable therapeutic potential.
In this video, the full process of an animal model of heart failure creation followed by gene transfer is presented using a swine model. First, myocardial infarction is created by occluding the proximal left anterior descending coronary artery. Heart remodeling results in chronic heart failure. Unique to our model is a fairly large scar which truly reflects patients with severe heart failure who require aggressive therapy for positive outcomes. After myocardial infarct creation and development of scar tissue, an intracoronary injection of virus is demonstrated with simultaneous nitroglycerine infusion. Our injection method provides simple and efficient gene transfer with enhanced gene expression. This combination of a myocardial infarct swine model with intracoronary virus delivery has proven to be a consistent and reproducible methodology, which helps not only to test the effect of individual gene, but also compare the efficacy of many genes as therapeutic candidates.

A method of gene transfer for the treatment of ischemic heart failure is described using a swine model of myocardial infarction. Our simple and reproducible method enables us to readily evaluate the efficacy of various gene transfers with a very simple and reproducible way.

Various emerging technologies are being developed for patients with heart failure. Well-established preclinical evaluations are necessary to determine ...

The WATCHMAN Left Atrial Appendage Closure Device for Atrial Fibrillation

Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting an estimated 6 million people in the United States 1. Since AF affects primarily elderly people, its prevalence increases parallel with age. As such, it is expected that 15.9 million Americans will be affected by the year 2050 2. Ischemic stroke occurs in 5% of non-anticoagulated AF patients each year. Current treatments for AF include rate control, rhythm control and prevention of stroke 3.
The American College of Cardiology, American Heart Association, and European Society of Cardiology currently recommended rate control as the first course of therapy for AF 3. Rate control is achieved by administration of pharmacological agents, such as &beta;-blockers, that lower the heart rate until it reaches a less symptomatic state 3. Rhythm control aims to return the heart to its normal sinus rhythm and is typically achieved through administration of antiarrhythmic drugs such as amiodarone, electrical cardioversion or ablation therapy. Rhythm control methods, however, have not been demonstrated to be superior to rate-control methods 4-6. In fact, certain antiarrhythmic drugs have been shown to be associated with higher hospitalization rates, serious adverse effects 3, or even increases in mortality in patients with structural heart defects 7. Thus, treatment with antiarrhythmics is more often used when rate-control drugs are ineffective or contraindicated. Rate-control and antiarrhythmic agents relieve the symptoms of AF, including palpitations, shortness of breath, and fatigue 8, but don't reliably prevent thromboembolic events 6.
Treatment with the anticoagulant drug warfarin significantly reduces the rate of stroke or embolism 9,10. However, because of problems associated with its use, fewer than 50% of patients are treated with it. The therapeutic dose is affected by drug, dietary, and metabolic interactions, and thus requires detailed monitoring. In addition, warfarin has the potential to cause severe, sometimes lethal, bleeding 2. As an alternative, aspirin is commonly prescribed. While aspirin is typically well tolerated, it is far less effective at preventing stroke 10. Other alternatives to warfarin, such as dabigatran 11 or rivaroxaban 12 demonstrate non-inferiority to warfarin with respect to thromboembolic events (in fact, dabigatran given as a high dose of 150 mg twice a day has shown superiority). While these drugs have the advantage of eliminating dietary concerns and eliminating the need for regular blood monitoring, major bleeding and associated complications, while somewhat less so than with warfarin, remain an issue 13-15.
Since 90% of AF-associated strokes result from emboli that arise from the left atrial appendage (LAA) 2, one alternative approach to warfarin therapy has been to exclude the LAA using an implanted device to trap blood clots before they exit. Here, we demonstrate a procedure for implanting the WATCHMAN Left Atrial Appendage Closure Device. A transseptal cannula is inserted through the femoral vein, and under fluoroscopic guidance, inter-atrial septum is crossed. Once access to the left atrium has been achieved, a guidewire is placed in the upper pulmonary vein and the WATCHMAN Access Sheath and dilator are advanced over the wire into the left atrium. The guidewire is removed, and the access sheath is carefully advanced into the distal portion of the LAA over a pigtail catheter. The WATCHMAN Delivery System is prepped, inserted into the access sheath, and slowly advanced. The WATCHMAN device is then deployed into the LAA. The device release criteria are confirmed via fluoroscopy and transesophageal echocardiography (TEE) and the device is released.

The accompanying video describes a procedure for percutaneous placement of the WATCHMAN Left Atrial Appendage (LAA) Device. The WATCHMAN is a nitinol device designed to be permanently implanted at, or slightly distal to, the opening of the left atrial appendage (LAA) to trap blood clots before they exit the LAA, preventing thromboembolic stroke.

Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting an estimated 6 million people in the United States 1. Since AF affects primarily ...

A New Single Chamber Implantable Defibrillator with Atrial Sensing: A Practical Demonstration of Sensing and  Ease of Implantation

Implantable cardioverter-defibrillators (ICDs) terminate ventricular tachycardia (VT) and ventricular fibrillation (VF) with high efficacy and can protect patients from sudden cardiac death (SCD). However, inappropriate shocks may occur if tachycardias are misdiagnosed. Inappropriate shocks are harmful and impair patient quality of life. The risk of inappropriate therapy increases with lower detection rates programmed in the ICD. Single-chamber detection poses greater risks for misdiagnosis when compared with dual-chamber devices that have the benefit of additional atrial information. However, using a dual-chamber device merely for the sake of detection is generally not accepted, since the risks associated with the second electrode may outweigh the benefits of detection. Therefore, BIOTRONIK developed a ventricular lead called the LinoxSMART S DX, which allows for the detection of atrial signals from two electrodes positioned at the atrial part of the ventricular electrode. This device contains two ring electrodes; one that contacts the atrial wall at the junction of the superior vena cava (SVC) and one positioned at the free floating part of the electrode in the atrium. The excellent signal quality can only be achieved by a special filter setting in the ICD (Lumax 540 and 740 VR-T DX, BIOTRONIK). Here, the ease of implantation of the system will be demonstrated.

Dual-chamber implantable cardioverter-defibrillators (ICDs) may improve detection of atrial fibrillation as well as differentiation of tachycardias. However, this advantage is undermined by complications associated with the second electrode, which is required in conventional dual chamber devices. Therefore, BIOTRONIK has developed a new electrode called the LinoxSMART S DX that, when used in conjunction with the Lumax DX ICD, offers dual-chamber detection without the risks associated with the second electrode.

Implantable cardioverter-defibrillators (ICDs) terminate ventricular tachycardia (VT) and ventricular fibrillation (VF) with high efficacy and can protect ...

Method of Isolated Ex Vivo Lung Perfusion in a Rat Model: Lessons Learned from Developing a Rat EVLP Program

The number of acceptable donor lungs available for lung transplantation is severely limited due to poor quality. Ex-Vivo Lung Perfusion (EVLP) has allowed lung transplantation in humans to become more readily available by enabling the ability to assess organs and expand the donor pool. As this technology expands and improves, the ability to potentially evaluate and improve the quality of substandard lungs prior to transplant is a critical need. In order to more rigorously evaluate these approaches, a reproducible animal model needs to be established that would allow for testing of improved techniques and management of the donated lungs as well as to the lung-transplant recipient. In addition, an EVLP animal model of associated pathologies, e.g., ventilation induced lung injury (VILI), would provide a novel method to evaluate treatments for these pathologies. Here, we describe the development of a rat EVLP lung program and refinements to this method that allow for a reproducible model for future expansion. We also describe the application of this EVLP system to model VILI in rat lungs. The goal is to provide the research community with key information and &#8220;pearls of wisdom&#8221;/techniques that arose from trial and error and are critical to establishing an EVLP system that is robust and reproducible.

Method of Isolated Ex Vivo Lung Perfusion in a Rat Model: Lessons Learned from Developing a Rat EVLP Program

Ex-Vivo Lung Perfusion (EVLP) has allowed lung transplantation in humans to become more readily available by enabling the ability to assess organs and expand the donor pool. Here, we describe the development of a rat EVLP program and refinements that allow for a reproducible model for future expansion.

The number of acceptable donor lungs available for lung transplantation is severely limited due to poor quality. Ex-Vivo Lung Perfusion (EVLP) has allowed ...

The Inverted Heart Model for Interstitial Transudate Collection from the Isolated Rat Heart

The present protocol describes a unique approach that enables the collection of cardiac transudate (CT) from the isolated, saline-perfused rat heart. After isolation and retrograde perfusion of the heart according to the Langendorff technique, the heart is inverted into an upside-down position and is mechanically stabilized by a balloon catheter inserted into the left ventricle. Then, a thin latex cap &#8211; previously cast to match the average size of the rat heart &#8211; is placed over the epicardial surface. The outlet of the latex cap is connected to silicon tubing, with the distal opening 10 cm below the base level of the heart, creating slight suction. CT continuously produced on the epicardial surface is collected in ice-cooled vials for further analysis. The rate of CT formation ranged from 17 to 147 &#181;L/min (n = 14) in control and infarcted hearts, which represents 0.1-1% of the coronary venous effluent perfusate. Proteomic analysis and high performance liquid chromatography (HPLC) revealed that the collected CT contains a wide spectrum of proteins and purinergic metabolites.

This protocol describes a method to collect cardiac interstitial fluid from the isolated, perfused rat heart. To physically separate interstitial transudate from coronary venous effluent perfusate, the Langendorff perfused heart is inverted, and the transudate (interstitial fluid) formed on the cardiac surface is collected using a soft latex cap.

The present protocol describes a unique approach that enables the collection of cardiac transudate (CT) from the isolated, saline-perfused rat heart. ...

Isolation and Cultivation of Adult Rat Cardiomyocytes

In an intact heart, adjacent cells influence adult cardiomyocytes. With the method of isolation and cultivation of adult cardiomyocytes, a precise investigation of the behavior of these cells under specific treatments and environments is possible. This manuscript presents a protocol for successful isolation and cultivation of adult rat ventricular cardiomyocytes (ARVC).
The rat is sacrificed by cervical dislocation under deep anesthesia. Then, the heart is extracted and the aorta is uncovered. Subsequently, perfusion on the Langendorff perfusion system with calcium depletion and collagenase treatment is performed. Afterwards, ventricular tissue gets minced, re-circulated, and filtered, followed by three centrifugation steps with gradual addition of CaCl2 until physiological calcium concentration is reached. ARVC are plated on cell culture dishes. After refreshing the cell culture medium, ARVC can be cultivated for up to six days without changing the serum-containing culture medium. Isolation of ARVC is a calcium sensitive process. Small changes in the intracellular calcium concentration cause a decrease in the quality and viability of the isolated cells.
Freshly isolated ARVC are rod shaped. Within the first days of cultivation they lose the rod-shaped morphology and form pseudopodia-like structures (spreading). During this morphological formation ARVC initially degrade their contractile elements followed by a reformation through actin stress fibers and de novo sarcomerogenesis. After one week of cultivation, most ARVC show a widespread appearance with a clearly detectable cross striation. This process is sensitive to intracellular calcium concentration, as treatment with ionomycin attenuates spreading. Key markers in this process of de- and re-differentiation are &#946;-myosin heavy chain (&#946;-MHC), oncostatin M (OSM), and swiprosin-1 (EFHD2). Recent studies have suggested that cardiac re- and de-differentiation occurring under culture conditions mimics features seen in vivo during cardiac remodeling. Therefore, isolation and cultivation of ARVC play a key role in understanding the biology of cardiomyocytes.

Here, we present a protocol for the isolation and cultivation of adult rat ventricular cardiomyocytes (ARVC). Isolated ARVC can be used for short and long-term cultivation. The isolation and cultivation of ARVC can play a key role in developing new treatment regimens for cardiac diseases.

In an intact heart, adjacent cells influence adult cardiomyocytes. With the method of isolation and cultivation of adult cardiomyocytes, a precise ...

Tachycardia-Induced Cardiomyopathy As a Chronic Heart Failure Model in Swine

A stable and reliable model of chronic heart failure is required for many experiments to understand hemodynamics or to test effects of new treatment methods. Here, we present such a model by tachycardia-induced cardiomyopathy, which can be produced by rapid cardiac pacing in swine.
A single pacing lead is introduced transvenously into fully anaesthetized healthy swine, to the apex of the right ventricle, and fixated. Its other end is then tunneled dorsally to the paravertebral region. There, it is connected to an in-house modified heart pacemaker unit that is then implanted in a subcutaneous pocket. 
After 4 - 8 weeks of rapid ventricular pacing at rates of 200 - 240 beats/min, physical examination revealed signs of severe heart failure - tachypnea, spontaneous sinus tachycardia, and fatigue. Echocardiography and X-ray showed dilation of all heart chambers, effusions, and severe systolic dysfunction. These findings correspond well to decompensated dilated cardiomyopathy and are also preserved after the cessation of pacing.
This model of tachycardia-induced cardiomyopathy can be used for studying the pathophysiology of progressive chronic heart failure, especially hemodynamic changes caused by new treatment modalities like mechanical circulatory supports. This methodology is easy to perform and the results are robust and reproducible.

Here, we present a protocol to produce tachycardia-induced cardiomyopathy in swine. This model represents a potent way to study the hemodynamics of progressive chronic heart failure and the effects of applied treatment.

A stable and reliable model of chronic heart failure is required for many experiments to understand hemodynamics or to test effects of new treatment ...

Isolation of Atrial Myocytes from Adult Mice

The electrophysiological properties of atrial myocytes importantly affect overall cardiac function. Alterations in the underlying ionic currents responsible for the action potential can cause pro-arrhythmic substrates that underlie arrhythmias, such as atrial fibrillation, which are highly prevalent in many conditions and disease states. Isolating adult mouse atrial cardiomyocytes for use in patch-clamp experiments has greatly advanced our knowledge and understanding of the cellular electrophysiology in the healthy atrial myocardium and in the setting of atrial pathophysiology. In addition, studies using genetic mouse models have elucidated the role of a vast array of proteins in regulating atrial electrophysiology. Here we provide a detailed protocol for the isolation of cardiomyocytes from the atrial appendages of adult mice using a combination of enzymatic digestion and mechanical dissociation of these tissues. This approach consistently and reliably yields isolated atrial cardiomyocytes that can then be used to characterize cellular electrophysiology by measuring action potentials and ionic currents in patch-clamp experiments under a number of experimental conditions.

This protocol is used to isolate single atrial cardiomyocytes from the adult mouse heart using a chunk digestion approach. This approach is used to isolate right or left atrial myocytes that can be used to characterize atrial myocyte electrophysiology in patch-clamp studies.

The electrophysiological properties of atrial myocytes importantly affect overall cardiac function. Alterations in the underlying ionic currents ...

Establishing a Swine Model of Post-myocardial Infarction Heart Failure for Stem Cell Treatment

Although advances have been achieved in the treatment of heart failure (HF) following myocardial infarction (MI), HF following MI remains one of the major causes of mortality and morbidity around the world. Cell-based therapies for cardiac repair and improvement of left ventricular function after MI have attracted considerable attention. Accordingly, the safety and efficacy of these cell transplantations should be tested in a preclinical large animal model of HF prior to clinical use. Pigs are widely used for cardiovascular disease research due to their similarity to humans in terms of heart size and coronary anatomy. Therefore, we sought to present an effective protocol for the establishment of a porcine chronic HF model using closed-chest coronary balloon occlusion of the left circumflex artery (LCX), followed by rapid ventricular pacing induced with pacemaker implantation. Eight weeks later, the stem cells were administered by intramyocardial injection in the peri-infarct area. Then the infarct size, cell survival, and left ventricular function (including echocardiography, hemodynamic parameters, and electrophysiology) were evaluated. This study helps establish a stable preclinical large animal HF model for stem cell treatment.

We sought to establish a swine model of heart failure induced by left circumflex artery blockage and rapid pacing to test the effect and safety of intramyocardial administration of stem cells for cell-based therapies.

Although advances have been achieved in the treatment of heart failure (HF) following myocardial infarction (MI), HF following MI remains one of the major ...

A Rat Model of Pressure Overload Induced Moderate Remodeling and Systolic Dysfunction as Opposed to Overt Systolic Heart Failure

In response to an injury, such as myocardial infarction, prolonged hypertension or a cardiotoxic agent, the heart initially adapts through the activation of signal transduction pathways, to counteract, in the short-term, for the cardiac myocyte loss and or the increase in wall stress. However, prolonged activation of these pathways becomes detrimental leading to the initiation and propagation of cardiac remodeling leading to changes in left ventricular geometry and increases in left ventricular volumes; a phenotype seen in patients with systolic heart failure (HF). Here, we describe the creation of a rat model of pressure overload induced moderate remodeling and early systolic dysfunction (MOD) by ascending aortic banding (AAB) via a vascular clip with an internal area of 2 mm2. The surgery is performed in 200 g Sprague-Dawley rats. The MOD HF phenotype develops at 8-12 weeks after AAB and is characterized noninvasively by means of echocardiography. Previous work suggests the activation of signal transduction pathways and altered gene expression and post-translational modification of proteins in the MOD HF phenotype that mimic those seen in human systolic HF; therefore, making the MOD HF phenotype a suitable model for translational research to identify and test potential therapeutic anti-remodeling targets in HF. The advantages of the MOD HF phenotype compared to the overt systolic HF phenotype is that it allows for the identification of molecular targets involved in the early remodeling process and the early application of therapeutic interventions. The limitation of the MOD HF phenotype is that it may not mimic the spectrum of diseases leading to systolic HF in human. Moreover, it is a challenging phenotype to create, as the AAB surgery is associated with high mortality and failure rates with only 20% of operated rats developing the desired HF phenotype.

We describe the creation of a rat model of pressure overload induced moderate remodeling and early systolic dysfunction where signal transduction pathways involved in the initiation of the remodeling process are activated. This animal model will aid in identifying molecular targets for applying early therapeutic anti-remodeling strategies for heart failure.

In response to an injury, such as myocardial infarction, prolonged hypertension or a cardiotoxic agent, the heart initially adapts through the activation ...