We would like to thank the Helmsley foundation for providing ultrasound equipment to perform our experiments. This work was supported by NIA R01 053585 grant.

All procedures were performed in accordance with protocols approved by the University of Louisville Institutional Animal Care and Use Committee (IACUC-approved protocol 18223) and the NIH Guide for the Care and Use of Laboratory Animals11.
1. Animals
<ol>
	<li>Use 4-month-old female Fisher 344 rats (BW~150-180 g) for the study.</li>
</ol>
2. Ultrasound Imaging before IR surgery
<ol>
	<li>Anesthetize the rat with isoflurane - induction chamber at 5% with 1.5&#8211;2.0 L/min O2 flow followed by 1.5&#8211;2.0% with 1.5&#8211;2.0 L/min O2 flow. This anesthesia is maintained throughout the experiment, during the resting and stress stages.</li>
	<li>Place the animal in a supine position and shave the thorax. Maintain the body temperature at 37-38 &#176;C using the built-in warming platform. Monitor the heart rate using the software. 
	NOTE: Proper anesthesia is crucial for maintaining the heart rate at normal physiological rates (between 295-350 beats/min).</li>
	<li>Apply ophthalmic vet ointment to prevent the dryness of eyes prior to the imaging.</li>
	<li>Perform echocardiography using 13&#8211;24 MHz linear probe (e.g., MS250) (Figure 1A).</li>
	<li>Place the animal in the supine position on the heated platform. Ensure that the anesthesia is controlled via the nose cone. Then position the probe to obtain the parasternal short axis view (PSAX) using the rail system (Figure 1B).</li>
	<li>Moving the probe in the rostral direction from the PSAX, locate the pulmonary artery (Figure 1B).</li>
	<li>Move the probe slightly in the direction caudal from the pulmonary artery to view the LAD and store the image. 
	NOTE: The LAD is difficult to find without Color Doppler, so B-Mode images of the LAD are not always possible.</li>
	<li>When individual differences make it difficult to locate the LAD coronary artery, follow the technique mentioned below:
	<ol>
		<li>Move the probe lateral to the pulmonary artery.</li>
		<li>Angle the platform so that the animal is inclined, inverted, or slightly towards the right side so that the left ventricle is more readily visible with the probe.</li>
	</ol>
	</li>
	<li>Once the image in B Mode is captured or cine-stored, click the Color Doppler on the touch screen (Figure 1C). Visualize the coronary artery (white arrow indicates LAD) in the short axis (Figure 1C). The red color, as seen in real time, is indicative of the direction of the flow (i.e., blood flow is towards the probe).</li>
	<li>After visualizing LAD on a color-Doppler mode, change the mode to the pulse wave (PW)-mode. Look for the presence of a yellow-indicator line on the coronary artery (Figure 2A).</li>
	<li>Place the yellow PW-line in the middle of the coronary artery. Ensure that the angle is parallel to the direction of the flow. 
	NOTE: Velocity of the flow is highly dependent on the angle of the PW line, so be sure to match the angle of the on-screen probe with the angle of the LAD. Use the touch screen to adjust the angle; PW angle should be less than 60&#176;.</li>
	<li>Use cine store to capture the velocity of the resting LAD coronary flow at the peak diastole as wave forms (Figure 2B).</li>
	<li>After obtaining of resting LAD flow velocity, measure the maximum flow velocity of LAD during the stress to calculate CFR. To measure the maximum flow velocity during the stress, infuse Dobutamine at a dose of 20 &#181;g/kg/min via tail vein8 (Figure 2C). 
	NOTE: Dobutamine infusion should not be more than 8 min. Use an infusion pump and set the diameter of the infusion pump to 14.43 for BD 10 mL syringe.
	<ol>
		<li>Use 25-G infusion butterfly set for the tail vein cannulation. To place the infusion needle, place a small strip of gauze around the base of the rat&#8217;s tail, then grab with hemostats and twist the tourniquet to apply pressure and cause the vein to enlarge.</li>
		<li>Place the needle while directly connected to Dobutamine syringe. 
		NOTE: Take extra care not to accidentally introduce drug when drawing up blood to ensure proper placement of the needle in the tail vein. Also, be sure to avoid introducing an air bubble into the vein, as an embolism may be fatal to the animal.</li>
		<li>Once the needle is placed, stabilize it with a glue and a piece of surgical tape, securing the infusion line to the tail.</li>
		<li>Remove the hemostats and tourniquet to recover the flow.</li>
		<li>Place Dobutamine syringe in the infusion pump and set it to inject 20 &#181;g/kg/min.</li>
		<li>During Dobutamine infusion, carefully monitor the LAD peak and heart rate. Periodically record LAD PW peaks in the Doppler mode, especially whenever it increases in response to Dobutamine. 
		NOTE: The stress challenge induced by Dobutamine causes the heart to work harder; this often results in the movement of the heart and the LAD. Be prepared to move the animal, the probe, or both in order to keep the LAD in view.</li>
		<li>After LAD peaks and heart rate have plateaued during the challenge, stop the Dobutamine infusion, remove the tail vein infusion set and remove the animal from the platform. Allow the animal to recover in its home cage.</li>
	</ol>
	</li>
	<li>Select Peak Vel tool to obtain the peak diastolic velocities from the images shown in Figure 2B and C.</li>
	<li>Calculate the CFR index as the ratio of the LAD stress (Dobutamine) peak diastolic flow velocity to the resting LAD peak diastolic flow velocity (Figure 2A).</li>
</ol>
3. Ischemia Reperfusion Injury
<ol>
	<li>Anesthetize rat with isoflurane - induction chamber at 5% with 1.5&#8211;2.0 L/min O2 flow followed by 1.5&#8211;2.0% with 1.5&#8211;2.0 L/min O2 flow.</li>
	<li>Confirm the depth of anesthesia by the lack of the pedal withdrawal reflex. Use ophthalmic vet ointment on the eyes to prevent dryness. Maintain the proper body temperature of 37-38 &#176;C using a heating pad or an animal temperature controller.</li>
	<li>Administer pre-surgical Meloxicam, 5 mg/kg intramuscularly, 15 min before the surgery, followed by 2 mL subcutaneous bolus of 0.9% saline to prevent dehydration during the surgery. Sterile gloves and instruments were used, and aseptic techniques were employed. Using the fiber-optic light source, intubate rat using 18-gauge IV catheter and connect to the ventilator.</li>
	<li>Ligate LAD using 8-0 monofilament suture through 15 mm opening at the 5th intercostal space. Tie a plain knot and leave for 30 min. Visually confirm ischemia in all rats via discoloration of the heart surface12. Release the ligature after 30 min and verify reperfusion by the reddening of the previously discolored area of heart muscle for 1-2 min12.</li>
	<li>Close the rib cage using 4-0 absorbable suture with an interrupted suture pattern, then close the skin using 5-0 non-absorbable silk suture with continuous suture pattern.</li>
	<li>Remove the animal from anesthesia. Allow the animal to recover in the home cage.&#160;5mg/kg Meloxicam was injected intramuscular in every 24 hours before euthanizing the animal (72hours after surgery).</li>
</ol>
4. Ultrasound imaging after IR surgery
<ol>
	<li>72 h after IR surgery, measure the coronary flow and CFR again. Compare the measurements to before IR measurements. Repeat steps 2.1 to 2.15 as described above.</li>
</ol>

<ol>
	<li>Eltzschig, H. K., Eckle, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ischemia+and+reperfusion--from+mechanism+to+translation.">Ischemia and reperfusion--from mechanism to translation.</a> Nature medicine. 17 (11), 1391-1401 (2011).</li><li>French, C. J., Zaman, A. K., Sobel, B. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Failure+of+erythropoietin+to+render+jeopardized+ischemic+myocardium+amenable+to+incremental+salvage+by+early+reperfusion.">Failure of erythropoietin to render jeopardized ischemic myocardium amenable to incremental salvage by early reperfusion.</a> Coronary Artery Disease. 20 (4), 295-299 (2009).</li><li>Marzilli, M., Mariani, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ischemia-reperfusion+and+microvascular+dysfunction:+implications+for+salvage+of+jeopardized+myocardium+and+reduction+of+infarct+size.">Ischemia-reperfusion and microvascular dysfunction: implications for salvage of jeopardized myocardium and reduction of infarct size.</a> Italian Heart Journal. 2 Suppl 3, (2001).</li><li>Prasad, A., Gersh, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Management+of+microvascular+dysfunction+and+reperfusion+injury.">Management of microvascular dysfunction and reperfusion injury.</a> Heart (British Cardiac Society). 91 (12), 1530-1532 (2005).</li><li>Ishihara, 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=Impaired+coronary+flow+reserve+immediately+after+coronary+angioplasty+in+patients+with+acute+myocardial+infarction.">Impaired coronary flow reserve immediately after coronary angioplasty in patients with acute myocardial infarction.</a> British heart journal. 69 (4), 288-292 (1993).</li><li>Camici, P. G., d&#39;Amati, G., Rimoldi, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coronary+microvascular+dysfunction:+mechanisms+and+functional+assessment.">Coronary microvascular dysfunction: mechanisms and functional assessment.</a> Nature Reviews Cardiology. 12 (1), 48-62 (2015).</li><li>Chung, K. S., Nguyen, P. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-invasive+measures+of+coronary+microcirculation:+Taking+the+long+road+to+the+clinic.">Non-invasive measures of coronary microcirculation: Taking the long road to the clinic.</a> Journal of Nuclear Cardiology. , (2017).</li><li>Kelm, N. Q., 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=Adipose-derived+cells+improve+left+ventricular+diastolic+function+and+increase+microvascular+perfusion+in+advanced+age.">Adipose-derived cells improve left ventricular diastolic function and increase microvascular perfusion in advanced age.</a> PLoS One. 13 (8), e0202934 (2018).</li><li>Pan, 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=Late+recovery+of+coronary+flow+reserve+in+patients+successfully+treated+with+a+percutaneous+procedure.">Late recovery of coronary flow reserve in patients successfully treated with a percutaneous procedure.</a> Revista Espa&#241;ola de Cardiolog&#237;a. 56 (5), 459-464 (2003).</li><li>Samim, A., Nugent, L., Mehta, P. K., Shufelt, C., Bairey Merz, C. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Treatment+of+angina+and+microvascular+coronary+dysfunction.">Treatment of angina and microvascular coronary dysfunction.</a> Current treatment options in cardiovascular medicine. 12 (4), 355-364 (2010).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Guide for the Care and Use of Laboratory Animals. , (2011).</li><li>Ciuffreda, M. 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=Rat+experimental+model+of+myocardial+ischemia/reperfusion+injury:+an+ethical+approach+to+set+up+the+analgesic+management+of+acute+post-surgical+pain.">Rat experimental model of myocardial ischemia/reperfusion injury: an ethical approach to set up the analgesic management of acute post-surgical pain.</a> PloS one. 9 (4), (2014).</li><li>van de Hoef, T. P., Siebes, M., Spaan, J. A. E., Piek, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fundamentals+in+clinical+coronary+physiology:+why+coronary+flow+is+more+important+than+coronary+pressure.">Fundamentals in clinical coronary physiology: why coronary flow is more important than coronary pressure.</a> European Heart Journal. 36 (47), 3312-3319 (2015).</li><li>Naya, 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=Preserved+coronary+flow+reserve+effectively+excludes+high-risk+coronary+artery+disease+on+angiography.">Preserved coronary flow reserve effectively excludes high-risk coronary artery disease on angiography.</a> Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 55 (2), 248-255 (2014).</li><li>Cortigiani, 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=Diagnostic+and+prognostic+value+of+Doppler+echocardiographic+coronary+flow+reserve+in+the+left+anterior+descending+artery.">Diagnostic and prognostic value of Doppler echocardiographic coronary flow reserve in the left anterior descending artery.</a> Heart (British Cardiac Society). 97 (21), 1758 (2011).</li><li>Kawata, T., 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=Prognostic+value+of+coronary+flow+reserve+assessed+by+transthoracic+Doppler+echocardiography+on+long-term+outcome+in+asymptomatic+patients+with+type+2+diabetes+without+overt+coronary+artery+disease.">Prognostic value of coronary flow reserve assessed by transthoracic Doppler echocardiography on long-term outcome in asymptomatic patients with type 2 diabetes without overt coronary artery disease.</a> Cardiovascular diabetology. 12, 121-121 (2013).</li></ol>

The authors have nothing to disclose

The major findings from the present study are that IR increases the resting LAD coronary artery velocity and impairs CFR, even in the absence of any residual angiographic stenosis.
Understanding the coronary physiology is an essential part of the clinical decision-making for cardiologists to treat coronary artery disease. CFR is one of the important functional parameters in understanding the pathophysiology of coronary microcirculation7,13</...

Myocardial ischemia reperfusion (IR) is a condition where blood supply is restricted to the heart followed by the restoration of perfusion and simultaneous reoxygenation1. Occlusion of coronary arteries can be caused by an embolus or cholesterol plaque rupture, which results in a severe imbalance of metabolic supply and demand, causing tissue hypoxia. Salvage of jeopardized myocardium, improve left ventricular function, and enhance survival in patients with acute myocardial infarction have been observed by the reperfusion therapy. However, after recanalization of the coronary artery, functional abnormalities of small coronary vessels may occur2,3,4,5. A significant proportion of patients, perhaps as many as 40%, do not regain microvascular and myocardial perfusion despite the restoration of coronary flow. Visualization and evaluation of the coronary microvasculature can be difficult in vivo, but there are a number of invasive and noninvasive techniques that can be used to assess parameters directly depending on the coronary microvascular function6,7. Also, the endothelial function can be assessed at the level of the coronary circulation via the CFR5.
Transthoracic Doppler echocardiography is a noninvasive tool which allows us to study coronary artery flow velocity and CFR5. CFR represents the ratio of maximal coronary blood flow to the resting coronary blood flow8. During the stress challenge, a normal heart increases coronary blood flow up to four times above the resting value. Cardiovascular risk increases when CFR is diminished9. Ishihara et al showed that the CFR was severely impaired immediately after the coronary angioplasty5. In the absence of coronary artery stenosis, CFR decreases during the coronary microvascular dysfunction and is present in about half of the patients with stable coronary artery disease10.
The overall goal of this method is noninvasive visualization of left anterior descending coronary artery (LAD) function in rats via echocardiography, which may be used to calculate CFR. This offers an important assessment tool for diagnosing microvascular dysfunction and evaluating potential therapeutic treatments.

<table>
	<tbody>
		<tr>
			<td>10 mL syringe</td>
			<td>BD Syringe</td>
			<td>302995</td>
			<td></td>
		</tr>
		<tr>
			<td>250S 13&#8211;24 MHz linear probe</td>
			<td>FUJIFILM VisualSonics Inc</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dobutamine hydrochloride</td>
			<td>Sigma</td>
			<td>D0676-10mg</td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>RRC</td>
			<td>27376</td>
			<td></td>
		</tr>
		<tr>
			<td>Legato 100 Syringe pump</td>
			<td>KD Scientific</td>
			<td>788100</td>
			<td></td>
		</tr>
		<tr>
			<td>Vevo 3100</td>
			<td>FUJIFILM VisualSonics Inc</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Winged infusion set, 27G x 1/2&#34;,</td>
			<td>Medline.com</td>
			<td>TMOSV27ELZ</td>
			<td></td>
		</tr>
	</tbody>
</table>

evaluation of coronary flow reserve after myocardial ischemia reperfusion in rats

Coronary artery disease is the leading cause of death worldwide. After an acute myocardial infarction, early and successful myocardial intervention via recanalization of the coronary artery is the most effective strategy for reducing the size of ischemic myocardium. The coronary microvasculature cannot be visualized and imaged&#160;in vivo, but there are several invasive and noninvasive techniques that can be used to assess parameters which depend directly on coronary microvascular function. The endothelial function after ischemia reperfusion can be assessed also at the level of the coronary circulation via the coronary flow reserve (CFR).&#160;In this study, peak velocity of left anterior descending (LAD) coronary arteries was measured in rats in vivo via Transthoracic Doppler Echocardiography during resting and stress challenge (induced by Dobutamine). A normal heart can increase its coronary blood flow up to four times above the resting values during stress induction. Following ischemia reperfusion, we found a significantly diminished CFR, which can be used as a marker of coronary microvascular dysfunction. CFR has opened a window on the importance of microvascular dysfunction and has been shown to predict cardiovascular risk independent of whether the severe obstructive disease is present.

For this study, we used 12 female Fisher 344 rats. We performed a stress test with Dobutamine and measured LAD coronary artery velocity before and 72 hours after the IR surgery. Before the IR surgery, resting LAD coronary artery velocity was measured as 423 &#177; 59 mm/s, which was increased after Dobutamine infusion (1005 &#177; 77mm/s) (Figure 3A). After 72 h of ischemia reperfusion, resting LAD coronary artery velocity was significantly higher compared to...

Watch this Scientific Journal Video about Evaluation of Coronary Flow Reserve After Myocardial Ischemia Reperfusion in Rats at JoVE.com

Evaluation of Coronary Flow Reserve After Myocardial Ischemia Reperfusion in Rats

Coronary flow reserve (CFR), is defined as the ratio of maximal coronary blood flow to the resting coronary blood flow. We present a protocol for evaluating CFR in rats via ultrasound, which offers the opportunity to predict cardiovascular risk factors in the absence of obstructive coronary disease.

Coronary artery disease is the leading cause of death worldwide. After an acute myocardial infarction, early and successful myocardial intervention via ...

evaluation-coronary-flow-reserve-after-myocardial-ischemia

Research

JoVE Journal

Medicine

7.8K Views.  University of Louisville. Coronary flow reserve (CFR), is defined as the ratio of maximal coronary blood flow to the resting coronary blood flow. We present a protocol for evaluating CFR in rats via ultrasound, which offers the opportunity to predict cardiovascular risk factors in the absence of obstructive coronary disease.

Video: Evaluation of Coronary Flow Reserve After Myocardial Ischemia Reperfusion in Rats

A Murine Closed-chest Model of Myocardial Ischemia and Reperfusion

Surgical trauma by thoracotomy in open-chest models of coronary ligation induces an immune response which modifies different mechanisms involved in ischemia and reperfusion. Immune response includes cytokine expression and release or secretion of endogenous ligands of innate immune receptors. Activation of innate immunity can potentially modulate infarct size. We have modified an existing murine closed-chest model using hanging weights which could be useful for studying myocardial pre- and postconditioning and the role of innate immunity in myocardial ischemia and reperfusion. This model allows animals to recover from surgical trauma before onset of myocardial ischemia.
Volatile anesthetics have been intensely studied and their preconditioning effect for the ischemic heart is well known. However, this protective effect precludes its use in open chest models of coronary artery ligation. Thus, another advantage could be the use of the well controllable volatile anesthetics for instrumentation in a chronic closed-chest model, since their preconditioning effect lasts up to 72 hours. Chronic heart diseases with intermittent ischemia and multiple hit models are other possible applications of this model.
For the chronic closed-chest model, intubated and ventilated mice undergo a lateral blunt thoracotomy via the 4th intercostal space. Following identification of the left anterior descending a ligature is passed underneath the vessel and both suture ends are threaded through an occluder. Then, both suture ends are passed through the chest wall, knotted to form a loop and left in the subcutaneous tissue. After chest closure and recovery for 5 days, mice are anesthetized again, chest skin is reopened and hanging weights are hooked up to the loop under ECG control.
At the end of the ischemia/reperfusion protocol, hearts can be stained with TTC for infarct size assessment or undergo perfusion fixation to allow morphometric studies in addition to histology and immunohistochemistry.

Surgical trauma induces an inflammatory response. Cytokines and endogenous ligands are known to modulate myocardial infarct size following ischemia and reperfusion. We present a modified closed-chest model of murine ischemia and reperfusion using hanging weights to minimize effects of thoracotomy.

Surgical trauma by thoracotomy in open-chest models of coronary ligation induces an immune response which modifies different mechanisms involved in ...

A Murine Model of Myocardial Ischemia-reperfusion Injury through Ligation of the Left Anterior Descending Artery

Acute or chronic myocardial infarction (MI) are cardiovascular events resulting in high morbidity and mortality. Establishing the pathological mechanisms at work during MI and developing effective therapeutic approaches requires methodology to reproducibly simulate the clinical incidence and reflect the pathophysiological changes associated with MI. Here, we describe a surgical method to induce MI in mouse models that can be used for short-term ischemia-reperfusion (I/R) injury as well as permanent ligation. The major advantage of this method is to facilitate location of the left anterior descending artery (LAD) to allow for accurate ligation of this artery to induce ischemia in the left ventricle of the mouse heart. Accurate positioning of the ligature on the LAD increases reproducibility of infarct size and thus produces more reliable results. Greater precision in placement of the ligature will improve the standard surgical approaches to simulate MI in mice, thus reducing the number of experimental animals necessary for statistically relevant studies and improving our understanding of the mechanisms producing cardiac dysfunction following MI. This mouse model of MI is also useful for the preclinical testing of treatments targeting myocardial damage following MI.

We introduce a surgical method to induce experimental ischemia/reperfusion (I/R) injury to simulate myocardial infarction (MI) in mouse models that allows for more clarity in positioning of the ligation on the left anterior descending artery (LAD) to increase the reproducibility of MI experiments in mice.

Acute or chronic myocardial infarction (MI) are cardiovascular events resulting in high morbidity and mortality. Establishing the pathological mechanisms ...

Ultrasound Based Assessment of Coronary Artery Flow and Coronary Flow Reserve Using the Pressure Overload Model in Mice

Transthoracic Doppler echocardiography (TTDE) is a clinically useful, noninvasive tool for studying coronary artery flow velocity and coronary flow reserve (CFR) in humans. Reduced CFR is accompanied by marked intramyocardial and pericoronary fibrosis and is used as an indication of the severity of dysfunction. This study explores, step-by-step, the real-time changes measured in the coronary flow velocity, CFR and systolic to diastolic peak velocity (S/D) ratio in the setting of an aortic banding model in mice. By using a Doppler transthoracic imaging technique that yields reproducible and reliable data, the method assesses changes in flow in the septal coronary artery (SCA), for a period of over two weeks in mice, that previously either underwent aortic banding or thoracotomy. 
During imaging, hyperemia in all mice was induced by isoflurane, an anesthetic that increased coronary flow velocity when compared with resting flow. All images were acquired by a single imager. Two ratios, (1) CFR, the ratio between hyperemic and baseline flow velocities, and (2) systolic (S) to diastolic (D) flow were determined, using a proprietary software and by two independent observers. Importantly, the observed changes in coronary flow preceded LV dysfunction as evidenced by normal LV mass and fractional shortening (FS). 
The method was benchmarked against the current gold standard of coronary assessment, histopathology. The latter technique showed clear pathologic changes in the coronary artery in the form of peri-coronary fibrosis that correlated to the flow changes as assessed by echocardiography. 
The study underscores the value of using a non-invasive technique to monitor coronary circulation in mouse hearts. The method minimizes redundant use of research animals and demonstrates that advanced ultrasound-based indices, such as CFR and S/D ratios, can serve as viable diagnostic tools in a variety of investigational protocols including drug studies and the study of genetically modified strains.

Coronary flow reserve (CFR) is useful for assessment of myocardial oxygen demand and evaluation of cardiovascular risk. This study establishes a step-by-step transthoracic Doppler echocardiographic (TTDE) method for longitudinal monitoring of the changes in CFR, as measured from coronary artery in mice, under the experimental pressure overload of aortic banding.

Transthoracic Doppler echocardiography (TTDE) is a clinically useful, noninvasive tool for studying coronary artery flow velocity and coronary flow ...

Confirmation of Myocardial Ischemia and Reperfusion Injury in Mice Using Surface Pad Electrocardiography

Many animal models have been established for the study of myocardial remodeling and heart failure due to its status as the number one cause of mortality worldwide. In humans, a pathologic occlusion forms in a coronary artery and reperfusion of that occluded artery is considered essential to maintain viability of the myocardium at risk. Although essential for myocardial recovery, reperfusion of the ischemic myocardium creates its own tissue injury. The physiologic response and healing of an ischemia/reperfusion injury is different from a chronic occlusion injury. Myocardial ischemia/reperfusion injury is gaining recognition as a clinically relevant model for myocardial infarction studies. For this reason, parallel animal models of ischemia/reperfusion are vital in advancing the knowledge base regarding myocardial injury. Typically, ischemia of the mouse heart after left anterior descending (LAD) coronary artery occlusion is confirmed by visible pallor of the myocardium below the occlusion (ligature). However, this offers only a subjective way of confirming correct or consistent ligature placement, as there are multiple major arteries that could cause pallor in different myocardial regions. A method of recording electrocardiographic changes to assess correct ligature placement and resultant ischemia as well as reperfusion, to supplement observed myocardial pallor, would help yield consistent infarct sizes in mouse models. In turn, this would help decrease the number of mice used. Additionally, electrocardiographic changes can continue to be recorded non-invasively in a time-dependent fashion after the surgery. This article will demonstrate a method of electrocardiographically confirming myocardial ischemia and reperfusion in real time.

During murine myocardial ischemia/reperfusion surgery, correct placement of the occluding ligature is typically confirmed by visible observation of myocardial pallor. Herein, a method of electrocardiographically confirming ischemia and reperfusion, to supplement observed myocardial pallor, is demonstrated in male C57Bl/6 mice.

Many animal models have been established for the study of myocardial remodeling and heart failure due to its status as the number one cause of mortality ...

Delayed Intramyocardial Delivery of Stem Cells after Ischemia Reperfusion Injury in a Murine Model

There is significant interest in the use of stem cells (SCs) for the recovery of cardiac function in individuals with myocardial injuries. Most commonly, cardiac stem cell therapy is studied by delivering SCs concurrently with the induction of myocardial injury. However, this approach presents two significant limitations: the early hostile pro-inflammatory ischemic environment may affect the survival of transplanted SCs, and it does not represent the subacute infarction scenario where SCs will likely be used. Here we describe a two-part series of surgical procedures for the induction of ischemia-reperfusion injury and delivery of mesenchymal stem cells (MSCs). This method of stem cell administration may allow for the longer viability and retention around damaged tissue by circumventing the initial immune response. A model of ischemia reperfusion injury was induced in mice accompanied by the delivery of mesenchymal stem cells (3.0 x 105), stably expressing the reporter gene firefly luciferase under the constitutively expressed CMV promoter, intramyocardially 7 days later. The animals were imaged via ultrasound and bioluminescent imaging for confirmation of injury and injection of cells, respectively. Importantly, there was no added complication rate when performing this two-procedure approach for SC delivery. This method of stem cell administration, collectively with the utilization of state-of-the-art reporter genes, may allow for the in vivo study of viability and retention of transplanted SCs in a situation of chronic ischemia commonly seen clinically, while also circumventing the initial pro-inflammatory response. In summary, we established a protocol for the delayed delivery of stem cells into the myocardium, which can be used as a potential new approach in promoting regeneration of the damaged tissue.

Stems cells are continuously investigated as potential treatments for individuals with myocardial damage, however, their decreased viability and retention within injured tissue can impact their long-term efficacy. In this manuscript we describe an alternative method for stem cell delivery in a murine model of ischemia reperfusion injury.

There is significant interest in the use of stem cells (SCs) for the recovery of cardiac function in individuals with myocardial injuries. Most commonly, ...

Post-Myocardial Infarction Heart Failure in Closed-chest Coronary Occlusion/Reperfusion Model in G&#246;ttingen Minipigs and Landrace Pigs

The development of heart failure is the most powerful predictor of long-term mortality in patients surviving acute myocardial infarction (MI). There is an unmet clinical need for prevention and therapy of post-myocardial infarction heart failure (post-MI HF). Clinically relevant pig models of post-MI HF are prerequisites for final proof-of-concept studies before entering into clinical trials in drug and medical device development.
Here we aimed to characterize a closed-chest porcine model of post-MI HF in adult G&#246;ttingen minipigs with long-term follow-up including serial cardiac magnetic resonance imaging (CMRI) and to compare it with the commonly used Landrace pig model.
MI was induced by intraluminal balloon occlusion of the left anterior descending coronary artery for 120 min in G&#246;ttingen minipigs and for 90 min in Landrace pigs, followed by reperfusion. CMRI was performed to assess cardiac morphology and function at baseline in both breeds and at 3 and 6 months in G&#246;ttingen minipigs and at 2 months in Landrace pigs, respectively.
Scar sizes were comparable in the two breeds, but MI resulted in a significant decrease of left ventricular ejection fraction (LVEF) only in G&#246;ttingen minipigs, while Landrace pigs did not show a reduction of LVEF. Right ventricular (RV) ejection fraction increased in both breeds despite the negligible RV scar sizes. In contrast to the significant increase of left ventricular end-diastolic (LVED) mass in Landrace pigs at 2 months, G&#246;ttingen minipigs showed a slight increase in LVED mass only at 6 months.
In summary, this is the first characterization of post-MI HF in G&#246;ttingen minipigs in comparison to Landrace pigs, showing that the G&#246;ttingen minipig model reflects post-MI HF parameters comparable to the human pathology. We conclude that the G&#246;ttingen minipig model is superior to the Landrace pig model to study the development of post-MI HF.

The overall goal of the current study is to present the techniques of induction of myocardial infarction (MI) and post-myocardial infarction heart failure (post-MI HF) in closed-chest, adult G&#246;ttingen minipigs and the characterization of post-MI HF model in G&#246;ttingen minipigs as compared to Landrace pigs.

The development of heart failure is the most powerful predictor of long-term mortality in patients surviving acute myocardial infarction (MI). There is an ...

Rodent Heart and Brain Tissue Preparation for Digital Macro Photography after Ischemia-reperfusion

Macro photography is applicable for imaging various tissue samples at high magnification to perform qualitative and quantitative analyses. Tissue preparation and subsequent image capture are steps performed immediately after the ischemia-reperfusion (IR) experiment and must be performed in a timely manner and with appropriate care. For the evaluation of IR-induced damage in the heart and brain, this paper describes 2,3,5-triphenyl-2H-tetrazolium chloride (TTC)-based staining followed by macro photography. Scientific macro photography requires controlled lighting and an appropriate imaging setup. The standardized methodology ensures high-quality, detailed digital images even if a combination of an inexpensive up-to-date digital camera and macro lens is used. Proper techniques and potential mistakes in sample preparation and image acquisition are discussed, and examples of the influence of correct and incorrect setups on image quality are provided. Specific tips are provided on how to avoid common mistakes, such as overstaining, improper sample storage, and suboptimal lighting conditions. This paper shows the appropriate methodology for rat heart and brain tissue slicing and staining and provides guidelines for establishing lighting and camera setups and photography techniques for high-resolution image acquisition.

Presented here is a protocol for the standardized methodology of rodent tissue preparation after the ischemia-reperfusion experiment and guidelines for establishing lighting and camera setups for high-resolution image acquisition. This method is applicable to all experimental small-animal organ photography.

Macro photography is applicable for imaging various tissue samples at high magnification to perform qualitative and quantitative analyses. Tissue ...

Induction of Myocardial Infarction and Myocardial Ischemia-Reperfusion Injury in Mice

Acute myocardial infarction is a common cardiovascular disease with high mortality. Myocardial reperfusion injury can counteract the beneficial effects of heart reflow and induce secondary myocardial injury. A simple and reproducible model of myocardial infarction and myocardial ischemia-reperfusion injury is a good tool for researchers. Here, a customizable method to create a myocardial infarction (MI) model and MIRI by precision ligation of the left anterior descending coronary artery (LAD) through micromanipulation is described. Accurate and reproducible ligature positioning of the LAD helps obtain consistent results for heart injury. ST-segment changes can help to identify model accuracy. The serum level of cardiac troponin T (cTnT) is used to assess the myocardial injury, cardiac ultrasound is employed to evaluate the myocardial systolic function, and Evans-Blue/triphenyl tetrazolium chloride staining is used to measure infarct size. In general, this protocol reduces procedure duration, ensures controllable infarct size, and improves mouse survival.

Here we describe a simple and reproducible method that can induce myocardial infarction or myocardial ischemia-reperfusion injury in mice by precision ligation of the left anterior descending coronary artery through micromanipulation.

Acute myocardial infarction is a common cardiovascular disease with high mortality. Myocardial reperfusion injury can counteract the beneficial effects of ...

Improved Rodent Model of Myocardial Ischemia and Reperfusion Injury

Myocardial ischemia and reperfusion injury (MIRI), induced by coronary heart disease (CHD), causes damage to the cardiomyocytes. Furthermore, evidence suggests that thrombolytic therapy or primary percutaneous coronary intervention (PPCI) does not prevent reperfusion injury. There is still no ideal animal model for MIRI. This study aims to improve the MIRI model in rats to make surgery easier and more feasible. A unique method for establishing MIRI is developed by using a soft tube during a key step of the ischemic period. To explore this method, thirty rats were randomly divided into three groups: sham group (n = 10); experimental model group (n = 10); and existing model group (n = 10). Findings of triphenyltetrazolium chloride staining, electrocardiography, and percent survival are compared to determine the accuracies and survival rates of the operations. Based on the study results, it has been concluded that the improved surgery method is associated with a higher survival rate, elevated ST-T segment, and larger infarct size, which is expected to mimic the pathology of MIRI better.

Myocardial ischemia-reperfusion model of rat heart is improved by using a self-made retractor, polyvinyl chloride tube, and a unique knotting method. Electrocardiogram, triphenyltetrazolium chloride and histological staining, and percent survival analysis results showed that the improved model group has higher success and survival rates than the already existing model group.

Myocardial ischemia and reperfusion injury (MIRI), induced by coronary heart disease (CHD), causes damage to the cardiomyocytes. Furthermore, evidence ...

Left Anterior Descending Coronary Artery Ligation for Ischemia-Reperfusion Research: Model Improvement via Technical Modifications and Quality Control

Coronary heart disease is the leading cause of death globally. Complete cessation of blood flow in coronary arteries causes ST-segment elevation myocardial infarction (STEMI), resulting in cardiogenic shock and fatal arrhythmia, which are associated with high mortality. Primary coronary intervention (PCI) for recanalizing the coronary artery significantly improves the outcomes of STEMI, but advancements made in shortening the door-to-balloon time have failed to reduce in-hospital mortality, suggesting that additional therapeutic strategies are required. Left anterior descending coronary artery (LAD) ligation in rats is an animal model for acute myocardial IR research that is comparable to the clinical scenario in which rapid coronary recanalization through PCI is used for STEMI; however, PCI-induced STEMI is a technically challenging and complicated operation associated with high mortality and great variation in infarction size. We identified the ideal position for LAD ligation, created a gadget to control a snare loop, and supported a modified surgical maneuver, thereby reducing tissue damage, to establish a reliable and reproducible acute myocardial ischemia-reperfusion (IR) research protocol for rats. This is a non-survival surgery. We also propose a method for validating the quality of study results, which is a critical step for determining the accuracy of subsequent biochemical analyses.

Herein, we present a protocol focusing on the quality control of the left anterior descending coronary artery ligation by technically modifying the traditional procedure in rats for acute myocardial ischemia-reperfusion research.