Direct Endoscopic Visual Assessment of a Transcatheter Aortic Valve Implantation and Performance in the PhysioHeart, an Isolated Working Heart Platform
Transcatheter aortic valve implantation (TAVI) is an increasingly considered option to treat aortic stenosis in patients with a high operative risk. Valve placement during the procedure is typically guided by angiography and/or echocardiography, whereas these techniques are also used to judge valvular function. More detailed postprocedure visualization may be obtained with 3-dimensional echocardiography or magnetic resonance imaging. These imaging methods appear to be adequate for clinical assessment of TAVI, but direct optical visualization with high temporal and spatial resolution would be advantageous to study the details of this new procedure.
The working heart model as described by Chinchoy et al1 enables direct intracardiac endoscopy,2 which provides unique insights into the form, function, and physiology of the heart. We applied this approach to study the placement and performance of a commercially available Edwards Sapien 26 transcatheter aortic heart valve (Edwards Lifesciences, Inc, Irvine, Calif; Sapien is not available for sale in the United States). The Movie in the online-only Data Supplement shows the procedure and gives additional explanation.
We developed a working isolated pig heart model, the PhysioHeart. Hearts were obtained from the local slaughterhouse and transported to our laboratory by use of conventional cold myocardial protection. Coronary arteries were isolated and perfused with oxygenated whole blood at a constant perfusion pressure (100 mm Hg). The left-sided cardiac chambers pumped a transparent medium in a separate loop to facilitate endoscopic intracardiac visualization. For this purpose, the left atrium was connected to a fluid reservoir with a constant filling pressure of 15 to 20 mm Hg and the aorta to an artificial afterload with adjustable compliance and resistance to achieve physiological conditions. This setup (Figure 1) provides a platform that closely resembles a normal working human heart with a cardiac output of ≈3.5 L/min, normal left ventricular and aortic pressures (120/80 mm Hg and heart rate 85 bpm), and physiological pressure and flow pulses.
Intracardiac images were obtained with an endoscope inserted into the left ventricle via purse-string suture and in the ascending aorta through the afterload system. The scope was connected to a high-resolution (1000×1000 pixels), high-speed (200 frames per second) camera (IDT MotionPro M5, Tallahassee, Fla).
TAVI was performed as described by Walther et al.3 Briefly, a purse-string suture was placed near the apex of the left ventricle. The native aortic valve was passed with a guidewire, and the sheath and valve were inserted. Subsequently, the valve was positioned and placed by balloon expansion during rapid ventricular pacing (Figure 2). After normal hemodynamics were achieved, images from the left ventricle and ascending aorta were recorded to study the anatomic structures and the placement and performance of the valve prosthesis (Movie in the online-only Data Supplement). Normal symmetrical opening-closing behavior and an excellent effective orifice of the prosthesis were observed (Figure 3). Also note the physiological timing and interaction with the mitral valve (Movie in the online-only Data Supplement).
The PhysioHeart provides a unique platform to study placement and performance of cardiac prostheses such as the Sapien valve under controlled physiological conditions. This approach may help to optimize TAVI, for example, by enabling the evaluation of new developments regarding valve anchoring and native leaflet capture. More generally, direct, high-resolution visualization could be valuable for testing and benchmarking of various intracardiac interventions and cardiac devices. In addition, this setup can be used for scientific, training, and educational purposes.
Dr de Weger is a proctor for Edwards Lifesciences regarding the transapical transcatheter heart valve program. The remaining authors report no conflicts.
Sources of Funding
The Sapien valve and implantation catheters were provided by Edwards Lifesciences.
The online-only Data Supplement is available with this article at http://circ.ahajournals.org/cgi/content/full/121/13/e261/DC1.