Name: Author Spotlight: Advancing Cardiac Procedure Testing Prior to Embarking on Large Animal Studies
Uploaded: 2023-08-25T15:00:00
Description: Watch this Scientific Journal Video about Advancing Cardiac Procedure Testing Prior to Embarking on Large Animal Studies at JoVE.com

We would like to thank the lab of Dr. Gordana Vunjak-Novakovic, including Julie Van Hassel, Mohamed Diane, and Panpan Chen, for allowing us to use cardiac waste tissue from their experiments. This work was supported by the Congenital Heart Defect Coalition in Butler, NJ, and the National Institutes of Health in Bethesda, MD (5T32HL007854-27).

All research was performed in compliance with institutional guidelines for the care of animals.
1. Considerations and preparations for the experiment
<ol>
	<li>Utilize a suitable pulse duplicator (PD) for the simulation of cardiac output through the AV. The PD will need to be able to accommodate biological materials and be able to be cleaned.
	<ol>
		<li>Utilize PD settings appropriate for testing the AV: 70 mL displacement volume and 70 beats per minute (5 L/min cardiac out...

Evaluation of Hydrodynamic Properties in Mounted Porcine Aortic Valves

<ol>
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M. O., 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=Comparative+angiotomographic+study+of+swine+vascular+anatomy:+contributions+to+research+and+training+models+in+vascular+and+endovascular+surgery.">Comparative angiotomographic study of swine vascular anatomy: contributions to research and training models in vascular and endovascular surgery.</a> Journal Vascular Brasilerio. 20, 20200086 (2021).</li><li>Ho&#322;da, M. K., Klimek-Piotrowska, W., Koziej, M., Pi&#261;tek, K., Ho&#322;da, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+different+fixation+protocols+on+the+preservation+and+dimensions+of+cardiac+tissue.">Influence of different fixation protocols on the preservation and dimensions of cardiac tissue.</a> Journal of Anatomy. 229 (2), 334-340 (2016).</li><li>Ho&#322;da, M. K., Klimek-Piotrowska, W., Koziej, M., Tyrak, K., Ho&#322;da, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Penetration+of+formaldehyde+based+fixatives+into+heart.">Penetration of formaldehyde based fixatives into heart.</a> Folia Medica Cracoviensia. 57 (4), 63-70 (2017).</li><li>Spampinato, R. 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=Grading+of+aortic+regurgitation+by+cardiovascular+magnetic+resonance+and+pulsed+Doppler+of+the+left+subclavian+artery:+harmonizing+grading+scales+between+imaging+modalities.">Grading of aortic regurgitation by cardiovascular magnetic resonance and pulsed Doppler of the left subclavian artery: harmonizing grading scales between imaging modalities.</a> International Journal of Cardiovascular Imaging. 36 (8), 1517-1526 (2020).</li><li>Capps, S. B., Elkins, R. C., Fronk, D. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Body+surface+area+as+a+predictor+of+aortic+and+pulmonary+valve+diameter.">Body surface area as a predictor of aortic and pulmonary valve diameter.</a> The Journal of Thoracic and Cardiovascular Surgery. 119 (5), 975-982 (2000).</li><li>Baumgartner, 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=Recommendations+on+the+echocardiographic+assessment+of+aortic+valve+stenosis:+a+focused+update+from+the+European+Association+of+Cardiovascular+Imaging+and+the+American+Society+of+Echocardiography.">Recommendations on the echocardiographic assessment of aortic valve stenosis: a focused update from the European Association of Cardiovascular Imaging and the American Society of Echocardiography.</a> European Heart Journal - Cardiovascular Imaging. 18 (3), 254-275 (2017).</li><li>Saisho, 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=An+ex+vivo+evaluation+of+two+different+suture+techniques+for+the+Ozaki+aortic+neocuspidization+procedure.">An ex vivo evaluation of two different suture techniques for the Ozaki aortic neocuspidization procedure.</a> Interactive Cardiovascular and Thoracic Surgery. 33 (4), 518-524 (2021).</li><li>Saisho, 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=Ex+vivo+evaluation+of+the+Ozaki+procedure+in+comparison+with+the+native+aortic+valve+and+prosthetic+valves.">Ex vivo evaluation of the Ozaki procedure in comparison with the native aortic valve and prosthetic valves.</a> Interactive Cardiovascular and Thoracic Surgery. 35 (3), (2022).</li><li>Paulsen, M. J., 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=Comprehensive+ex+vivo+comparison+of+5+clinically+used+conduit+configurations+for+valve-sparing+aortic+root+replacement+using+a+3-dimensional-printed+heart+simulator.">Comprehensive ex vivo comparison of 5 clinically used conduit configurations for valve-sparing aortic root replacement using a 3-dimensional-printed heart simulator.</a> Circulation. 142 (14), 1361-1373 (2020).</li><li>Al-Atassi, 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=Impact+of+aortic+annular+geometry+on+aortic+valve+insufficiency:+Insights+from+a+preclinical,+ex+vivo,+porcine+model.">Impact of aortic annular geometry on aortic valve insufficiency: Insights from a preclinical, ex vivo, porcine model.</a> The Journal of Thoracic and Cardiovascular Surgery. 150 (3), 656-664 (2015).</li><li>Sun, 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+biomimetic+multilayered+polymeric+material+designed+for+heart+valve+repair+and+replacement.">A biomimetic multilayered polymeric material designed for heart valve repair and replacement.</a> Biomaterials. 288, 121756 (2022).</li><li>Waller, B. F., McKay, C., Van Tassel, J., Allen, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Catheter+balloon+valvuloplasty+of+stenotic+porcine+bioprosthetic+valves:+Part+I:+Anatomic+considerations.">Catheter balloon valvuloplasty of stenotic porcine bioprosthetic valves: Part I: Anatomic considerations.</a> Clinical Cardiology. 14 (8), 686-691 (1991).</li><li>Crick, S. J., Sheppard, M. N., Ho, S. Y., Gebstein, L., Anderson, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anatomy+of+the+pig+heart:+comparisons+with+normal+human+cardiac+structure.">Anatomy of the pig heart: comparisons with normal human cardiac structure.</a> Journal of Anatomy. 193, 105-119 (1998).</li></ol>

The method presented here provides a platform for hydrodynamic testing of the AV in order to examine the effect of an experimental procedure or a novel medical device. By mounting the native aortic valve on a pulse duplicator machine, we are able to determine the effect of the experimental procedure on all the hydrodynamic parameters used in the investigation and approval of novel valve prostheses (ISO 5840). This provides an opportunity to fine-tune procedures and prostheses prior to use in a large animal model.
<p ...

Aortic valve disease represents a significant public health burden, particularly aortic stenosis, which affects 9 million people worldwide1. Strategies to address this disease are currently evolving and include aortic valve repair and aortic valve replacement. In the pediatric population especially, there is a significant incentive to repair rather than replace the valve since currently available prostheses are prone to structural valve degeneration (SVD) and are not growth tolerant, requiring reoperation for re-replacement as the patient grows. Even the Ross procedure, which replaces the diseased aortic valve (AV) with the native pulmonary valve (PV), requires a prosthesis or graft in the pulmonary position that is also subject to SVD and often limited growth tolerance2. New approaches to aortic valve disease are being developed, and there is a need for testing in a biologically relevant context prior to application in a large animal model.
We have developed a method for testing a porcine AV that can provide insights into the function of the valve before and after an investigational procedure or application of a novel medical device. By mounting the porcine AV on a commercially available pulse duplicator machine, we are able to compare the hydrodynamic characteristics that are commonly used in the investigation and ultimately approval of valve prostheses, including regurgitation fraction (RF), effective orifice area (EOA), and mean positive pressure difference (PPD)3,4. The intervention can then be fine-tuned in a biologically relevant context before use in a large animal model, thus limiting the number of animals needed to produce a procedure or prosthesis that can be used in humans. The hearts used for this experiment can be obtained from the local abattoir or waste tissue from other experiments, so it is not necessary to sacrifice an animal solely for the purposes of this experiment.
In our work, we used this method to develop a novel patch material for valve repair and replacement. We tested the hydrodynamic function of a variety of patch materials by performing an aortic valve neocuspidization procedure (Ozaki procedure5,6,7) on porcine AVs and testing them in the pulse duplicator before and after the procedure. This enabled us to fine-tune the material based on its hydrodynamic performance. Thus, this method provides a platform for hydrodynamic testing of experimental procedures and novel medical devices for use on the AV prior to application&#160;in a large animal model.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>3D Printer</td>
			<td>Ultimaker</td>
			<td>Ultimaker S5</td>
			<td>Used for printing custom fixtures for hydrodynamic testing</td>
		</tr>
		<tr>
			<td>Crile-Wood Needle Driver</td>
			<td>Emerald Instruments</td>
			<td>2.0638.15</td>
			<td>Used for suturing ventricle</td>
		</tr>
		<tr>
			<td>Debakey Forceps</td>
			<td>Jarit</td>
			<td>320-110</td>
			<td>Used for dissection and sample preparation (can use multiple if working with an assistant)</td>
		</tr>
		<tr>
			<td>Ethanol 200 proof</td>
			<td>Decon Labs Inc.</td>
			<td>DSP-MD.43</td>
			<td>Used for fixed tissue storage</td>
		</tr>
		<tr>
			<td>Formalin 10%</td>
			<td>Epredia</td>
			<td>5701</td>
			<td>Used for tissue fixation</td>
		</tr>
		<tr>
			<td>Gerald Forceps</td>
			<td>Jarit</td>
			<td>285-126</td>
			<td>Used for dissection and sample preparation</td>
		</tr>
		<tr>
			<td>Glass jars</td>
			<td>QAPPDA</td>
			<td>B07QCP54Z3</td>
			<td>Used for tissue storage</td>
		</tr>
		<tr>
			<td>Glutaraldehyde 25%</td>
			<td>Electron Microscopy Sciences</td>
			<td>16400</td>
			<td>Used for tissue fixation</td>
		</tr>
		<tr>
			<td>HEPES 1 M buffer solution</td>
			<td>Fisher</td>
			<td>BP299-100</td>
			<td>Used to make glutaraldehyde 0.6%</td>
		</tr>
		<tr>
			<td>Mayo Scissors</td>
			<td>Jarit</td>
			<td>099-200</td>
			<td>Used for cutting suture</td>
		</tr>
		<tr>
			<td>Metzenbaum Scissors</td>
			<td>Jarit</td>
			<td>099-262</td>
			<td>Used for dissection and sample preparation</td>
		</tr>
		<tr>
			<td>O-ring</td>
			<td>Sterling Seal &#38; Supply Inc.</td>
			<td>AS568-117</td>
			<td>Used as a gasket on the end of the 3D printed fixtures</td>
		</tr>
		<tr>
			<td>Polylactic acid resin</td>
			<td>Ultimaker</td>
			<td>1609</td>
			<td>Used for 3D printing fixtures</td>
		</tr>
		<tr>
			<td>Polyproplene suture</td>
			<td>Covidien</td>
			<td>VP-762-X</td>
			<td>Used for suturing ventricle, tapered needle</td>
		</tr>
		<tr>
			<td>Pulse Duplicator</td>
			<td>BDC Laboratories</td>
			<td>HDTi-6000</td>
			<td>Used for hydrodynamic testing</td>
		</tr>
		<tr>
			<td>Silk ties</td>
			<td>Covidien</td>
			<td>S-193</td>
			<td>Used for ligating coronary arteries</td>
		</tr>
		<tr>
			<td>Tonsil Clamp</td>
			<td>Aesculap</td>
			<td>BH957R</td>
			<td>Used for coronary artery dissection</td>
		</tr>
		<tr>
			<td>Zip ties (6 inch)</td>
			<td>Advanced Cable Ties, Inc.</td>
			<td>AL-06-18-9-C</td>
			<td>Used for securing sample to fixtures, 157.14 mm long (6 inches), 2.5 mm wide</td>
		</tr>
		<tr>
			<td>Zip ties (8 inch)</td>
			<td>GTSE</td>
			<td>GTSE-20025B.1000</td>
			<td>Used for securing sample to fixtures, 203 mm long (8 inches), 2.5 mm wide</td>
		</tr>
	</tbody>
</table>

an ex vivo porcine model for hydrodynamic testing of experimental aortic valve procedures and novel medical devices

The options for testing new cardiac procedures and investigative medical devices prior to use in an animal model are limited. In this study, we present a method for mounting a porcine aortic valve in a pulse duplicator to evaluate its hydrodynamic properties. These properties can then be evaluated before and after the procedure under investigation is performed and/or the investigative medical device is applied. Securing the inflow segment presents some difficulty owing to the lack of circumferential myocardium in the left ventricular outflow tract. This method addresses that issue by securing the inflow segment using the anterior leaflet of the mitral valve and then suturing the left ventricular free wall around the inflow fixture. The outflow segment is secured simply by inserting the fixture into an incision in the superior aspect of the aortic arch. We found that specimens had significantly different hydrodynamic properties before and after tissue fixation. This finding induced us to use fresh specimens in our testing and should be considered when using this method. In our work, we used this method to test novel intracardiac patch materials for use in the valvular position by performing an aortic valve neocuspidization procedure (Ozaki procedure) on the mounted porcine aortic valves. These valves were tested before and after the procedure to assess the change in hydrodynamic properties in comparison to the native valve. Herein, we report a platform for hydrodynamic testing of experimental aortic valve procedures that enables comparison with the native valve and between different devices and techniques used for the procedure under investigation.

Author Spotlight: Advancing Cardiac Procedure Testing Prior to Embarking on Large Animal Studies 

An Ex Vivo Porcine Model for Hydrodynamic Testing of Experimental Aortic Valve Procedures and Novel Medical Devices

Limited options exist for testing new cardiac procedures and investigative medical devices before use in a large animal model. Our protocol provides the opportunity to fine-tune such procedures and devices in a biologically and anatomically relevant context prior to embarking on large animal studies. Other techniques for mounting an aortic valve on a pulse duplicator require inserting or fixing a rigid structure to the aortic valve annulus, thus distorting the valve's hydrodynamic properties.Our protocol offers an innovative way to cannulate the LVOT so that all measured hydrodynamic properties are valid. This method is designed to assess the viability of leaflet substitution materials for use as a valve repair patch or prosthesis. It is a pivotal tool for our future research in which we are developing biomimetic polymeric materials for use as durable valve substitutives with native tissue, like mechanical and hydrodynamic properties.

The representative data collected from the pulse duplicator includes regurgitation fraction (RF), effective orifice area (EOA), and mean positive pressure difference (PPD). The RF and EOA, in particular, are used in the ISO standards for prosthetic valves (ISO 5840) and will be important to collect if prosthetic valve products are under investigation. The PPD offers information regarding how much pressure is required to open the valve and is commonly referenced when discussing prosthetic valve replacement<sup class="xref...

Watch this Scientific Journal Video about Advancing Cardiac Procedure Testing Prior to Embarking on Large Animal Studies at JoVE.com

We present a method for mounting a porcine aortic valve on a pulse duplicator to test its hydrodynamic properties. This method can be used to determine the change in hydrodynamics after the application of an experimental procedure or novel medical device prior to use in a large animal model.

The options for testing new cardiac procedures and investigative medical devices prior to use in an animal model are limited. In this study, we present a ...

an-ex-vivo-porcine-model-for-hydrodynamic-testing-experimental-aortic

Research

JoVE Journal

Bioengineering

Preparation of Left Ventricular Outflow Tract (LVOT) from Porcine Heart for Cannulation 

To begin, collect a fresh porcine cardiac specimen after cardiectomy. Dissect the pulmonary artery off the aorta with Metzenbaum scissors until ventricular tissue is visible. Then, dissect the right and the left coronary arteries, and ligate them using silk ties at their origin from the aortic sinuses without narrowing the sinuses.Transect the coronary arteries distal to the silk ties. Using Metzenbaum scissors, incise the right ventricle between the aorta and the pulmonary artery at the base of the pulmonary valve. Beginning anteriorly, continue the incision circumferentially along the intraventricular septum to remove the right ventricle free wall.Continue the incision posteriorly through the tricuspid valve annulus along the interatrial septum to remove all right atrial tissue. Next, using Metzenbaum scissors, incise the left atrium through the right pulmonary vein ostium parallel to the aorta. Continue this incision towards the anterolateral commissure of the mitral valve.Trim excess left atrium tissue while maintaining the three millimeter cuff of atrial tissue on the aorta and the mitral valve annulus circumferentially. Now, extend the incision onto the left ventricle through the anterolateral commissure of the mitral valve without damaging the anterolateral papillary muscle. Divide the chordae tendineae from the anterolateral papillary muscle to the posterior mitral valve leaflet, preserving attachments to the anterior mitral valve leaflet.Extend the incision to the apex of the heart. Trim excess left ventricle tissue below the papillary muscles, preserving both papillary muscles.

Mounting a Porcine Aortic Valve on a Pulse Duplicator for Testing Hydrodynamic Properties

After preparing the left ventricular outflow tract, or LVOT, trim any excess lymphatic, connective, or pulmonary artery tissue off the aorta. Using Metzenbaum scissors, incise the superior aspect of the aortic arch from the descending aorta to the left subclavian artery. Continue the incision on the superior aspect of the aortic arch from the left subclavian artery to the brachiocephalic trunk.To cannulate the LVOT, insert the fixture into the LVOT under the anterior leaflet of the mitral valve. Wrap the left ventricle free wall around the fixture and trim excess tissue to maintain a tight wrap around the fixture. Next, remove half the thickness of the left ventricle free wall, starting at the interventricular septum.Trim one centimeter of the tissue off the superior corner of the left ventricle free wall wrap. Place the fixture in the LVOT, so the supporting rod attachment hole is one centimeter behind the left ventricle incision. Using one or two six-inch zip ties, fasten the anterior leaflet of the mitral valve to the fixture positioned between the chordae tendineae of the leaflet.Next, using a taper point needle, suture the cuff of the left atrium tissue on the aorta to the mitral valve annulus. Continue the running stitch onto the left ventricle without tearing the tissue. Using Hegar Dilators, measure the diameter of the aortic valve.Then lift the specimen by grasping the aorta to identify the neutral position of the aorta. Insert the pulse duplicator or PD fixture into the aorta, ensuring the rod attachment holes are aligned with the neutral position of the aorta. Verify the specimen's length by inserting the support rods into the attachment holes.Using one or two six-inch zip ties, secure the PD fixture to the aorta. Then using screws provided with the PD set. Secure the support rods in place.Subsequently, secure the LVOT around the PD fixture using one or two eight-inch zip ties. Place the specimen in the PD and start the hydrodynamic testing. The values for hydrodynamic testing of the native aortic valve were within the normal range with a mean regurgitation fraction of 5.74%Hydrodynamic testing values showed no significant differences between formalin and glutaraldehyde fixed samples.After the Ozaki procedure, the values obtained with the control patch material suggested consistent valve replacement outcomes.