This work was supported by a grant of the Romanian Ministry of Education and Research, CNCS - UEFISCDI, project number PN-III-P1-1.1-TE-2019-0370, within PNCDI III.

Procedures involving animal subjects were approved by the Ethics Committee of the University of Medicine, Pharmacy, Science and Technology &#34;George Emil Palade&#34; of T&#226;rgu Mure&#537;, by the Romanian National Sanitary Veterinary and Food Safety Authority and complied with the International Council for Laboratory Animal Science guidelines (Directive 2010/63/EU).
1. Transesophageal atrial burst pacing protocol
<ol>
	<li>Randomize adult male Wistar rats (200-400 g of bodyweight) into two groups: STIM and SHAM.</li>
	<li>Anesthetize the animals.
	<ol>
		<li>For induction, use 2.5% isoflurane, 4 L/min, 99.5% O2.</li>
		<li>For maintenance, use a mixture of ketamine/medetomidine (75.0/0.5 mg/kg) administered intraperitoneally.</li>
		<li>Check the depth of the anesthesia by testing the corneal reflex (5% glucose solution) and the nociceptive withdrawal reflex (toe pinch). Monitor the respiratory rate (a fall of 50% is acceptable during anesthesia; normal rate is between 70-120 breaths/minute) and the body temperature using a rectal thermometer (normal temperature is between 96.5 - 99.5 &#176;F or 35.9 - 37.5 &#176;C). 
		NOTE: Continue the procedure only after the effectiveness of anesthesia is confirmed. Monitor the depth of anesthesia periodically throughout the protocol. Repeat the intraperitoneal ketamine/medetomidine injection when needed.</li>
		<li>Apply an ophthalmic ointment to both eyes to prevent corneal damage.</li>
	</ol>
	</li>
	<li>Lay the animal in supine position and place it on a heating pad to maintain body temperature at ~37 &#176;C.</li>
	<li>Attach the three surface ECG electrodes to the rat limbs in a lead II configuration (Figure 1A).
	<ol>
		<li>Place the negative electrode on the right forelimb.</li>
		<li>Place the positive electrode on the left hindlimb.</li>
		<li>Place the grounding electrode on the left forelimb.</li>
		<li>Secure the electrodes into position using thin elastic bracelet string cords.</li>
	</ol>
	</li>
	<li>Turn on the surface ECG recording and perform continuous ECG recording throughout the procedure (Figure 1B) using a commercial or a locally developed acquisition program10.</li>
	<li>For electrical stimulation, use a 5-6 F quadripolar catheter connected to a microcontroller-based cardiac pacemaker10.</li>
	<li>Once the animal is anesthetized, insert the catheter through the oral cavity, into the esophagus. Measure the distance between the upper incisors and the heart (assessed by palpation) to approximate the depth at which the catheter should be inserted into the esophagus. 
	CAUTION: Be careful not to force the catheter as there is a risk of esophageal perforation.</li>
	<li>Confirm the correct position of the stimulation catheter at the level of the atria as follows.
	<ol>
		<li>Apply electrical stimulation at a frequency of 400 stimuli/minute (stimulus duration 6 ms).</li>
		<li>Check whether the ECG tracing shows constant capture of the atria (i.e., each electrical stimulus is followed by a narrow QRS complex) (Figure 2).</li>
	</ol>
	</li>
	<li>Determine the diastolic threshold&#8212;i.e., the lowest voltage required to obtain atrial capture (generally, between 10 V and 20 V). 
	NOTE: Perform the following for the animals in the STIM group.</li>
	<li>Once the correct position of the catheter is determined, set the stimulator to a frequency of 4,000 stimuli/minute (stimulus duration 6 ms), at a voltage 3 V above the diastolic threshold (Figure 3).</li>
	<li>Apply to each animal 15 successive cycles of stimulation, 20 s each, with a free interval of 5 min between cycles11. Depending on the study objectives, repeat the protocol for each rat for 10 days, at a rate of 5 days/week, at the same time on each day.</li>
	<li>Check the effectiveness of the stimulation as follows.
	<ol>
		<li>Identify the sinus node recovery time (SNRT), which appears at the end of the rapid pacing as a time interval that is longer than the cycle length recorded during sinus rhythm (Figure 4A) and represents the interval of time required for resumption of sinus rhythm after overdrive suppression ends. 
		NOTE: Overdrive suppression represents the inhibition of sinus node activity by electrically stimulating the heart at a rate higher than the intrinsic rhythm.</li>
		<li>Identify the occurrence of the AF episode, which is defined here as the presence of three or more consecutive irregular, supraventricular beats (i.e., irregular ventricular response with narrow QRS complexes), with P-waves absent or replaced by small, distorted &#34;f&#34; waves (Figure 4B).</li>
	</ol>
	</li>
	<li>If the AF episode does not end spontaneously by the time the next stimulation cycle should be performed (i.e., by the end of the five free minutes between cycles), do not apply the next stimulation.
	<ol>
		<li>Wait for another 5 min. If the AF episode still continues after those 10 min, end the protocol for that day. 
		NOTE: If evaluation of the severity of electrically-induced AF is desired, longer ECG monitoring can be performed.</li>
	</ol>
	</li>
	<li>If severe bradycardia or asystole occurs at the end of the stimulation (i.e., due to electrical stimulation of the vagus nerve), end the protocol. If the electrical activity does not return to normal rapidly, perform external cardiac massage and administer atropine sulfate (0.05 mg/kg) intraperitoneally.</li>
	<li>At the end of the procedure, reverse the anesthesia with atipamezole (1 mg/kg) administered intraperitoneally. House the rats individually in clean cages with supplemental heat and observe periodically until they are fully recovered. No other specific animal care is required at the end of the protocol.</li>
	<li>Analyze the surface ECG tracings and determine the following.
	<ol>
		<li>The inducibility of AF which is expressed in percentage (i.e., [number of stimulation cycles followed by AF episodes / total number of stimulation cycles applied] x 100).</li>
		<li>The duration of each AF episode.</li>
		<li>The presence of &#39;persistent&#39; (i.e., &#62;10 min) AF episodes. 
		NOTE: Perform the following for the animals in the SHAM group.</li>
	</ol>
	</li>
	<li>For the rats in the SHAM group, follow steps 1.1 to 1.7 as described above, without applying any electrical stimulation.</li>
	<li>Maintain the catheter into position for 80 min (i.e., the time required for completing the protocol in STIM rats) without applying any electrical stimulation, while continuously recording the surface ECG.</li>
	<li>At the end of the procedure, reverse the anesthesia with atipamezole (1 mg/kg). No other specific animal care is required at the end of the protocol.</li>
	<li>Analyze the surface ECG tracings and determine the parameters described in step 1.16.</li>
</ol>

<ol>
	<li>Kornej, J., B&#246;rschel, C. S., Benjamin, E. J., Schnabel, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Epidemiology+of+atrial+fibrillation+in+the+21st+century:+Novel+methods+and+new+insights.">Epidemiology of atrial fibrillation in the 21st century: Novel methods and new insights.</a> Circulation Research. 127 (1), 4-20 (2020).</li><li>Hindricks, 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=2020+ESC+Guidelines+for+the+diagnosis+and+management+of+atrial+fibrillation+developed+in+collaboration+with+the+European+Association+for+Cardio-Thoracic+Surgery+(EACTS):+The+Task+Force+for+the+diagnosis+and+management+of+atrial+fibrillation+of+the+European+Society+of+Cardiology+(ESC).">2020 ESC Guidelines for the diagnosis and management of atrial fibrillation developed in collaboration with the European Association for Cardio-Thoracic Surgery (EACTS): The Task Force for the diagnosis and management of atrial fibrillation of the European Society of Cardiology (ESC).</a> European Heart Journal. 42 (5), 373 (2021).</li><li>Veenhuyzen, G. D., Simpson, C. S., Abdollah, H. <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.">Atrial fibrillation.</a> Canadian Medical Association Journal. 171 (7), 755-760 (2004).</li><li>Lau, D. H., 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+arrhythmia+in+ageing+spontaneously+hypertensive+rats:+unraveling+the+substrate+in+hypertension+and+ageing.">Atrial arrhythmia in ageing spontaneously hypertensive rats: unraveling the substrate in hypertension and ageing.</a> PloS One. 8 (8), 72416 (2013).</li><li>Scridon, 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=Unprovoked+atrial+tachyarrhythmias+in+aging+spontaneously+hypertensive+rats:+The+role+of+the+autonomic+nervous+system.">Unprovoked atrial tachyarrhythmias in aging spontaneously hypertensive rats: The role of the autonomic nervous system.</a> American Journal of Physiology-Heart and Circulatory Physiology. 303 (3), 386-392 (2012).</li><li>Haugan, K., Lam, H. R., Knudsen, C. B., Petersen, J. S. <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+in+rats+induced+by+rapid+transesophageal+atrial+pacing+during+brief+episodes+of+asphyxia:+a+new+in+vivo+model.">Atrial fibrillation in rats induced by rapid transesophageal atrial pacing during brief episodes of asphyxia: a new in vivo model.</a> Journal of Cardiovascular Pharmacology. 44 (1), 125-135 (2004).</li><li>Sugiyama, A., Takahara, A., Honsho, S., Nakamura, Y., Hashimoto, K. <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+in+vivo+atrial+fibrillation+model+of+rat+induced+by+transesophageal+atrial+burst+pacing.">A simple in vivo atrial fibrillation model of rat induced by transesophageal atrial burst pacing.</a> Journal of Pharmacological Sciences. 98 (3), 315-318 (2005).</li><li>Scridon, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dissociation+between+animal+and+clinical+studies.+where+do+we+go+wrong.">Dissociation between animal and clinical studies. where do we go wrong.</a> Romanian Journal of Cardiology. 31 (3), 497-500 (2021).</li><li>Mulla, W., 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=Rapid+atrial+pacing+promotes+atrial+fibrillation+substrate+in+unanesthetized+instrumented+rats.">Rapid atrial pacing promotes atrial fibrillation substrate in unanesthetized instrumented rats.</a> Frontiers in Physiology. 10, 1218 (2019).</li><li>Scridon, 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=Spontaneous+atrial+fibrillation+after+long-term+transesophageal+atrial+burst+pacing+in+rats.+Technical+and+procedural+approach+to+a+new+in+vivo+atrial+fibrillation+model.">Spontaneous atrial fibrillation after long-term transesophageal atrial burst pacing in rats. Technical and procedural approach to a new in vivo atrial fibrillation model.</a> Romanian Journal of Laboratory Medicine. 26 (1), 105-112 (2018).</li><li>Halatiu, V. B., 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=Chronic+exposure+to+high+doses+of+bisphenol+A+exhibits+significant+atrial+proarrhythmic+effects+in+healthy+adult+rats.">Chronic exposure to high doses of bisphenol A exhibits significant atrial proarrhythmic effects in healthy adult rats.</a> Romanian Journal of Cardiology. 31 (3), 587-595 (2021).</li><li>Zaciragi&#263;, A., Nakas-i&#263;indi&#263;, E., Hadzovi&#263;, A., Avdagi&#263;, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Average+values+of+electrocardiograph+parameters+in+healthy,+adult+Wistar+rats.">Average values of electrocardiograph parameters in healthy, adult Wistar rats.</a> Medical Archives. 58 (5), 268-270 (2004).</li><li>Cheshire, W. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermoregulatory+disorders+and+illness+related+to+heat+and+cold+stress.">Thermoregulatory disorders and illness related to heat and cold stress.</a> Autonomic Neuroscience: Basic and Clinical. 196, 91-104 (2016).</li><li>&#536;erban, R. C., Scridon, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Data+linking+diabetes+mellitus+and+atrial+fibrillation-how+strong+is+the+evidence?+From+epidemiology+and+pathophysiology+to+therapeutic+implications.">Data linking diabetes mellitus and atrial fibrillation-how strong is the evidence? From epidemiology and pathophysiology to therapeutic implications.</a> Canadian Journal of Cardiology. 34 (11), 1492-1502 (2018).</li><li>Nishida, K., Michael, G., Dobrev, D., Nattel, S. <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+for+atrial+fibrillation:+clinical+insights+and+scientific+opportunities.">Animal models for atrial fibrillation: clinical insights and scientific opportunities.</a> Europace. 12 (2), 160-172 (2010).</li><li>Qiu, H., 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=DL-3-n-Butylphthalide+reduces+atrial+fibrillation+susceptibility+by+inhibiting+atrial+structural+remodeling+in+rats+with+heart+failure.">DL-3-n-Butylphthalide reduces atrial fibrillation susceptibility by inhibiting atrial structural remodeling in rats with heart failure.</a> Naunyn-Schmiedeberg's Archives of Pharmacology. 391 (3), 323-334 (2018).</li></ol>

The authors have no conflicts of interest.

The present paper describes an experimental protocol of long-term transesophageal atrial burst pacing for rapid and efficient induction of AF in rats, suitable for both acute and long-term AF studies. The 10-day stimulation protocol described herein has been successfully used to develop a 'secondary spontaneous AF model' (i.e., a model in which, following a period of AF induction by electrical stimulation, AF develops spontaneously)10. However, the duration of the protocol can vary depending on th...

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia encountered in clinical practice and its incidence and prevalence continue to increase dramatically worldwide1. This arrhythmia affects up to 4% of the world population according to recent studies2. However, given that paroxysmal AF can be asymptomatic and may therefore escape detection, the true prevalence of AF is likely to be much higher than that presented in the literature.
The pathophysiology of AF has been intensely studied. Nevertheless, the underlying mechanisms of this complex arrhythmia remain incompletely elucidated and this reflects in the limited therapeutic options, with questionable efficacy. Animal studies have brought important insights into our understanding regarding AF pathophysiology and therapeutic management. Reentry, one of the main mechanisms involved in AF pathogenesis3, requires a certain mass of myocardial tissue in order to occur. Thus, large animals have generally been preferred in AF studies, whereas, due to the small size of their atria, rodents have long been considered &#39;resistant&#39; to AF. However, the use of large animals is hampered mostly by handling difficulties. Meanwhile, although spontaneous AF has been shown to occur in rats4, long-term follow-up (up to 50 weeks) is required for the arrhythmia to occur in those models5. Models that ensure rapid AF occurrence in small rodents have also been developed. Most often, those models use acute electrical stimulation, often in the presence of other favoring conditions, such as concomitant parasympathetic stimulation or asphyxia, to artificially induce AF6,7. Although efficient, such models do not allow the evaluation of critical AF-related features, such as the progressive electrical, structural, autonomic, or molecular remodeling of the atria, nor the effects of conventional or non-conventional antiarrhythmic drugs on the atrial substrate or on the risk of ventricular pro-arrhythmia8,9.
The present work describes an experimental protocol of long-term transesophageal atrial burst pacing for rapid and efficient induction of AF in rats. The protocol is suitable for both acute and long-term studies and can be successfully used in rats with healthy or remodeled hearts, in the presence of a wide variety of risk factors, allowing the study of AF pathophysiology, identification of novel therapeutic targets, and evaluation of novel prophylactic and/or therapeutic strategies.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Antisedan (Atipamezole Hydrochloride) 5mg / mL, solution for injection</td>
			<td>Orion Corporation</td>
			<td>06043/4004</td>
			<td>for Rats use 1 mg / kg</td>
		</tr>
		<tr>
			<td>Dormitor (Medetomidine Hydrochloride) 1 mg / mL, solution for injection</td>
			<td>Orion Corporation</td>
			<td>06043/4003</td>
			<td>for Rats use 0.5 mg / kg</td>
		</tr>
		<tr>
			<td>E-Z Anesthesia Single Animal System</td>
			<td>E-Z Systems Inc</td>
			<td>EZ-SA800</td>
			<td>Allows the manipulation of one animal at a time</td>
		</tr>
		<tr>
			<td>Isoflurane 99.9%, 100 mL</td>
			<td>Rompharm Company</td>
			<td>N01AB06</td>
			<td></td>
		</tr>
		<tr>
			<td>Ketamine 10%, 25 mL</td>
			<td></td>
			<td></td>
			<td>for Rats use 75 mg / kg</td>
		</tr>
		<tr>
			<td>Microcontroller-based cardiac pacemaker for small animals</td>
			<td></td>
			<td></td>
			<td>Developed in our laboratory (See Reference number 10 in the manuscript)</td>
		</tr>
		<tr>
			<td>Surface ECG recording system</td>
			<td></td>
			<td></td>
			<td>Developed in our laboratory (See Reference number 10 in the manuscript)</td>
		</tr>
	</tbody>
</table>

transesophageal atrial burst pacing for atrial fibrillation induction in rats

Animal studies have brought important insights into our understanding regarding atrial fibrillation (AF) pathophysiology and therapeutic management. Reentry, one of the main mechanisms involved in AF pathogenesis, requires a certain mass of myocardial tissue in order to occur. Due to the small size of the atria, rodents have long been considered 'resistant' to AF. Although spontaneous AF has been shown to occur in rats, long-term follow-up (up to 50 weeks) is required for the arrhythmia to occur in those models. The present work describes an experimental protocol of transesophageal atrial burst pacing for rapid and efficient induction of AF in rats. The protocol can be successfully used in rats with healthy or remodeled hearts, in the presence of a wide variety of risk factors, allowing the study of AF pathophysiology, identification of novel therapeutic targets, and evaluation of novel prophylactic and/or therapeutic strategies.

In a proof-of-concept study, 22 adult male Wistar rats (200-400 g) were randomly assigned into two groups: STIM (n = 15) and SHAM (n = 7). All animals were housed individually in polycarbonate cages, in a climate-controlled room (21-22 &#176;C), having free access to water and dry food throughout the study. The transesophageal stimulation protocol described above was applied to all animals for 10 days, 5 days per week. All animals underwent the same protocol, except that the rats in the SHAM group did not receive active ...

Watch this Scientific Journal Video about Transesophageal Atrial Burst Pacing for Atrial Fibrillation Induction in Rats at JoVE.com

Transesophageal Atrial Burst Pacing for Atrial Fibrillation Induction in Rats

The present work describes an experimental protocol of transesophageal atrial burst pacing for efficient induction of atrial fibrillation (AF) in rats. The protocol can be used in rats with healthy or remodeled hearts, allowing the study of AF pathophysiology, identification of novel therapeutic targets, and evaluation of new therapeutic strategies.

Animal studies have brought important insights into our understanding regarding atrial fibrillation (AF) pathophysiology and therapeutic management. ...

transesophageal-atrial-burst-pacing-for-atrial-fibrillation-induction

Research

JoVE Journal

Medicine

3.0K Views.  University of Medicine, Pharmacy, Science and Technology “George Emil Palade” of Târgu Mureș. The present work describes an experimental protocol of transesophageal atrial burst pacing for efficient induction of atrial fibrillation (AF) in rats. The protocol can be used in rats with healthy or remodeled hearts, allowing the study of AF pathophysiology, identification of novel therapeutic targets, and evaluation of new therapeutic strategies.

Video: Transesophageal Atrial Burst Pacing for Atrial Fibrillation Induction in Rats

High-Resolution Endocardial and Epicardial Optical Mapping in a Sheep Model of Stretch-Induced Atrial Fibrillation

Atrial fibrillation (AF) is a complex cardiac arrhythmia with high morbidity and mortality.1,2 It is the most common sustained cardiac rhythm disturbance seen in clinical practice and its prevalence is expected to increase in the coming years.3 Increased intra-atrial pressure and dilatation have been long recognized to lead to AF,1,4 which highlights the relevance of using animal models and stretch to study AF dynamics. Understanding the mechanisms underlying AF requires visualization of the cardiac electrical waves with high spatial and temporal resolution. While high-temporal resolution can be achieved by conventional electrical mapping traditionally used in human electrophysiological studies, the small number of intra-atrial electrodes that can be used simultaneously limits the spatial resolution and precludes any detailed tracking of the electrical waves during the arrhythmia. The introduction of optical mapping in the early 90's enabled wide-field characterization of fibrillatory activity together with sub-millimeter spatial resolution in animal models5,6 and led to the identification of rapidly spinning electrical wave patterns (rotors) as the sources of the fibrillatory activity that may occur in the ventricles or the atria.7-9 Using combined time- and frequency-domain analyses of optical mapping it is possible to demonstrate discrete sites of high frequency periodic activity during AF, along with frequency gradients between left and right atrium. The region with fastest rotors activates at the highest frequency and drives the overall arrhythmia.10,11 The waves emanating from such rotor interact with either functional or anatomic obstacles in their path, resulting in the phenomenon of fibrillatory conduction.12 Mapping the endocardial surface of the posterior left atrium (PLA) allows the tracking of AF wave dynamics in the region with the highest rotor frequency. Importantly, the PLA is the region where intracavitary catheter-based ablative procedures are most successful terminating AF in patients,13 which underscores the relevance of studying AF dynamics from the interior of the left atrium. Here we describe a sheep model of acute stretch-induced AF, which resembles some of the characteristics of human paroxysmal AF. Epicardial mapping on the left atrium is complemented with endocardial mapping of the PLA using a dual-channel rigid borescope c-mounted to a CCD camera, which represents the most direct approach to visualize the patterns of activation in the most relevant region for AF maintenance.

This report provides a detailed description of the methodology and results of simultaneous endocardial and epicardial optical mapping of electrical excitation in the intact left atrium of a Langendorff-perfused sheep heart during stretch-induced atrial fibrillation.

 Atrial fibrillation (AF) is a complex cardiac arrhythmia with high morbidity and mortality.1,2 It is the most common sustained cardiac rhythm disturbance ...

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 ...

Catheter Ablation in Combination With Left Atrial Appendage Closure for Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, affecting millions of individuals worldwide 1-3. The rapid, irregular, and disordered electrical activity in the atria gives rise to palpitations, fatigue, dyspnea, chest pain and dizziness with or without syncope 4, 5. Patients with AF have a five-fold higher risk of stroke 6.
Oral anticoagulation (OAC) with warfarin is commonly used for stroke prevention in patients with AF and has been shown to reduce the risk of stroke by 64% 7. Warfarin therapy has several major disadvantages, however, including bleeding, non-tolerance, interactions with other medications and foods, non-compliance and a narrow therapeutic range 8-11. These issues, together with poor appreciation of the risk-benefit ratio, unawareness of guidelines, or absence of an OAC monitoring outpatient clinic may explain why only 30-60% of patients with AF are prescribed this drug 8.
The problems associated with warfarin, combined with the limited efficacy and/or serious side effects associated with other medications used for AF 12,13, highlight the need for effective non-pharmacological approaches to treatment. One such approach is catheter ablation (CA), a procedure in which a radiofrequency electrical current is applied to regions of the heart to create small ablation lesions that electrically isolate potential AF triggers 4. CA is a well-established treatment for AF symptoms 14, 15, that may also decrease the risk of stroke. Recent data showed a significant decrease in the relative risk of stroke and transient ischemic attack events among patients who underwent ablation compared with those undergoing antiarrhythmic drug therapy 16.
Since the left atrial appendage (LAA) is the source of thrombi in more than 90% of patients with non-valvular atrial fibrillation 17, another approach to stroke prevention is to physically block clots from exiting the LAA. One method for occluding the LAA is via percutaneous placement of the WATCHMAN LAA closure device. The WATCHMAN device resembles a small parachute. It consists of a nitinol frame covered by fabric polyethyl terephthalate that prevents emboli, but not blood, from exiting during the healing process. Fixation anchors around the perimeter secure the device in the LAA (Figure 1). To date, the WATCHMAN is the only implanted percutaneous device for which a randomized clinical trial has been reported. In this study, implantation of the WATCHMAN was found to be at least as effective as warfarin in preventing stroke (all-causes) and death (all-causes) 18. This device received the Conformit&eacute; Europ&eacute;enne (CE) mark for use in the European Union for warfarin eligible patients and in those who have a contraindication to anticoagulation therapy 19.
Given the proven effectiveness of CA to alleviate AF symptoms and the promising data with regard to reduction of thromboembolic events with both CA and WATCHMAN implantation, combining the two procedures is hoped to further reduce the incidence of stroke in high-risk patients while simultaneously relieving symptoms. The combined procedure may eventually enable patients to undergo implantation of the WATCHMAN device without subsequent warfarin treatment, since the CA procedure itself reduces thromboembolic events. This would present an avenue of treatment previously unavailable to patients ineligible for warfarin treatment because of recurrent bleeding 20 or other warfarin-associated problems.
The combined procedure is performed under general anesthesia with biplane fluoroscopy and TEE guidance. Catheter ablation is followed by implantation of the WATCHMAN LAA closure device. Data from a non-randomized trial with 10 patients demonstrates that this procedure can be safely performed in patients with a CHADS2 score of greater than 1 21. Further studies to examine the effectiveness of the combined procedure in reducing symptoms from AF and associated stroke are therefore warranted.

Catheter ablation is combined with placement of the WATCHMAN Left Atrial Appendage Closure Device to prevent ischemic stroke in a patient with non-valvular atrial fibrillation.

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, affecting millions of individuals worldwide 1-3. The rapid, irregular, and ...

Robotic Ablation of Atrial Fibrillation

Background: Pulmonary vein isolation (PVI) is an established treatment for atrial fibrillation (AF). During PVI an electrical conduction block between pulmonary vein (PV) and left atrium (LA) is created. This conduction block prevents AF, which is triggered by irregular electric activity originating from the PV. However, transmural atrial lesions are required which can be challenging. Re-conduction and AF recurrence occur in 20 - 40% of the cases. Robotic catheter systems aim to improve catheter steerability. Here, a procedure with a new remote catheter system (RCS), is presented. Objective of this article is to show feasibility of robotic AF ablation with a novel system. Materials and Methods: After interatrial trans-septal puncture is performed using a long sheath and needle under fluoroscopic guidance. The needle is removed and a guide wire is placed in the left superior PV. Then an ablation catheter is positioned in the LA, using the sheath and wire as guide to the LA. LA angiography is performed over the sheath. A circular mapping catheter is positioned via the long sheath into the LA and a three-dimensional (3-D) anatomical reconstruction of the LA is performed. The handle of the ablation catheter is positioned in the robotic arm of the Amigo system and the ablation procedure begins. During the ablation procedure, the operator manipulates the ablation catheter via the robotic arm with the use of a remote control. The ablation is performed by creating point-by-point lesions around the left and right PV ostia. Contact force is measured at the catheter tip to provide feedback of catheter-tissue contact. Conduction block is confirmed by recording the PV potentials on the circular mapping catheter and by pacing maneuvers. The operator stays out of the radiationfield during ablation. Conclusion: The novel catheter system allows ablation with high stability on low operator fluoroscopy exposure.

Pulmonary vein isolation (PVI) with an ablation catheter is a curative treatment for atrial fibrillation (AF). Robotic catheter systems aim to improve catheter steerability. Here, a procedure with a new robotic catheter system is presented. The goal of the procedure is electrical block between pulmonary vein and left atrium.

Background: Pulmonary vein isolation (PVI) is an established treatment for atrial fibrillation (AF). During PVI an electrical conduction block between ...

Left Atrial Stenosis Induced Pulmonary Venous Arterialization and Group 2 Pulmonary Hypertension in Rat

The mechanism of mitral stenosis-induced pulmonary venous arterialization and group 2 pulmonary hypertension (PH) is unclear. There is no rodent model of group 2 PH, due to mitral stenosis (MS), to facilitate the investigation of disease mechanisms and potential therapeutic strategies. We present a novel rat model of pulmonary venous congestion-induced pulmonary venous arterialization and group 2 PH caused by left atrial stenosis (LAS). LAS is achieved by constricting the left atrium using a half-closed titanium clip. After the LAS surgery, a rat model with a transmitral inflow velocity greater than or equal to 2.0 m/s on echocardiography gradually develops pulmonary venous arterialization and group 2 PH over an 8- to 10-week period. In this protocol, we provide the step-by-step procedure of how to perform the LAS surgery. The presented LAS rat model mimics MS in humans and is useful for studying the underlying molecular mechanism of pulmonary venous arterialization and for the preclinical evaluation of therapies for group 2 PH.

Left atrial stenosis (LAS) is a novel surgical technique used for studying group 2 pulmonary hypertension (PH) and mechanisms underlying pulmonary venous arterialization. Here, we present a protocol to constrict the left atrium using a titanium clip to cause pulmonary venous arterialization and moderate PH in a rat.

The mechanism of mitral stenosis-induced pulmonary venous arterialization and group 2 pulmonary hypertension (PH) is unclear. There is no rodent model of ...

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 ...

Cooling or Warming the Esophagus to Reduce Esophageal Injury During Left Atrial Ablation in the Treatment of Atrial Fibrillation

Ablation of the left atrium using either radiofrequency (RF) or cryothermal energy is an effective treatment for atrial fibrillation (AF) and is the most frequent type of cardiac ablation procedure performed. Although generally safe, collateral injury to surrounding structures, particularly the esophagus, remains a concern. Cooling or warming the esophagus to counteract the heat from RF ablation, or the cold from cryoablation, is a method that is used to reduce thermal esophageal injury, and there are increasing data to support this approach. This protocol describes the use of a commercially available esophageal temperature management device to cool or warm the esophagus to reduce esophageal injury during left atrial ablation. The temperature management device is powered by standard water-blanket heat exchangers, and is shaped like a standard orogastric tube placed for gastric suctioning and decompression. Water circulates through the device in a closed-loop circuit, transferring heat across the silicone walls of the device, through the esophageal wall. Placement of the device is analogous to the placement of a typical orogastric tube, and temperature is adjusted via the external heat-exchanger console.

The goal of this protocol is to describe the use of esophageal temperature modulation to counteract esophageal thermal injury from left atrial ablation for the treatment of atrial fibrillation.

Ablation of the left atrium using either radiofrequency (RF) or cryothermal energy is an effective treatment for atrial fibrillation (AF) and is the most ...

Echocardiographic Evaluation of Atrial Communications before Transcatheter Closure

Transthoracic (TTE) and transesophageal echocardiography (TEE) is the standard imaging method for atrial septal defect (ASD) and patent foramen ovale (PFO) detection, for patient selection for transcatheter ASD/PFO closure,&#160;for intraoperative guidance and for long-term follow-up. The size, shape, location and the number of the atrial communications schould be determined. The accuracy of PFO detection can be improved by using agitated saline together with maneuvers to transiently increase the right atrial (RA) pressure. The appearance of microbubbles in the left atrium (LA) within 3 cardiac cycles after opacification of the RA is considered positive for the presence of an intracardiac shunt. Three dimensional TEE identifies further septal fenestrations and describes the dynamic morphology of ASD/PFO and atrial septal aneurysm. Follow-up evaluations with TTE is recommended at 1, 6, and 12 months after the procedure, with a subsequent evaluation every year. Previous studies showed an increased incidence of atrial arrhythmias early after device closure. Speckle tracking analysis may help to understand functional left atrial remodeling following percutaneous closure and its impact on atrial arrhythmias.

Transthoracic (TTE) and transesophageal (TEE) echocardiography represent the basic imaging tools for interatrial septum examination. Three dimensional (3D) TEE provides incremental information in the assessment of the interatrial septum. Further advanced echocardiography techniques using speckle tracking echocardiography are applied for sensitive volumetric and functional assessment of the heart chambers.&#160;

Transthoracic (TTE) and transesophageal echocardiography (TEE) is the standard imaging method for atrial septal defect (ASD) and patent foramen ovale ...

Modifications of the Langendorff Method for Simultaneous Isolation of Atrial and Ventricular Myocytes from Adult Mice

A single cardiomyocyte is a vital tool in the cellular and subcellular level studies of cardiac biology and diseases as a fundamental unit of contraction and electrical activity. Hence, isolating viable, high-quality cardiomyocytes from the heart is the initial and most crucial experimental step. Comparing the various protocols for isolating the cardiomyocytes of adult mice, the Langendorff retrograde perfusion is the most successful and reproducible method reported in the literature, especially for isolating ventricular myocytes. However, isolating quality atrial myocytes from the perfused heart remains challenging, and few successful isolation reports are available. Solving this complicated problem is extremely important because apart from ventricular disease, atrial disease accounts for a large part of heart diseases. Therefore, further investigations on the cellular level to reveal the mechanisms are warranted. In this paper, a protocol based on the Langendorff retrograde perfusion method is introduced and some modifications in the depth of aorta cannulation and the steps that may affect the digestion process to isolate atrial and ventricular myocytes were simultaneously made. Moreover, the isolated cardiomyocytes are confirmed to be amenable to patch clamp investigation.

This protocol describes modifications of the Langendorff method including the depth of aorta cannulation for simultaneous Isolation of atrial and ventricular myocytes from adult mice.

A single cardiomyocyte is a vital tool in the cellular and subcellular level studies of cardiac biology and diseases as a fundamental unit of contraction ...

Sterile Pericarditis in Aachener Minipigs As a Model for Atrial Myopathy and Atrial Fibrillation

Atrial fibrillation (AF) is the most common arrhythmia caused by structural remodeling of the atria, also called atrial myopathy. Current therapies only target the electrical abnormalities and not the underlying atrial myopathy. For the development of novel therapies, a reproducible large animal model of atrial myopathy is necessary. This paper presents a model of sterile pericarditis-induced atrial myopathy in Aachener minipigs. Sterile pericarditis was induced by spraying sterile talcum and leaving a layer of sterile gauze over the atrial epicardial surface. This led to inflammation and fibrosis, two crucial components of the pathophysiology of atrial myopathy, making the atria susceptible to the induction of AF. Two pacemaker electrodes were positioned epicardially on each atrium and connected to two pacemakers from different manufacturers. This strategy allowed for repeated non-invasive atrial programmed stimulation to determine the inducibility of AF at specified time points after surgery. Different protocols to test AF inducibility were used. The advantages of this model are its clinical relevance, with AF inducibility and the rapid induction of inflammation and fibrosis-both present in atrial myopathy-and its reproducibility. The model will be useful in the development of novel therapies targeting atrial myopathy and AF.

We describe a sterile pericarditis model in minipigs to study atrial myopathy and atrial fibrillation (AF). We present surgical and anesthetic techniques, strategies for vascular access, and a protocol to study the inducibility of AF.

Atrial fibrillation (AF) is the most common arrhythmia caused by structural remodeling of the atria, also called atrial myopathy. Current therapies only ...