A dynamic heart system to facilitate the development of mitral valve repair techniques

Abstract

Objective: The development of a novel surgical tool or technique for mitral valve repair can be hampered by cost, complexity, and time associated with performing animal trials. A dynamically pressurized model was developed to control pressure and flowrate profiles in intact porcine hearts in order to quantify mitral regurgitation and evaluate the quality of mitral valve repair.

Methods: A pulse duplication system was designed to replicate physiological conditions in explanted hearts. To test the capabilities of this system in measuring varying degrees of mitral regurgitation, the output of eight porcine hearts was measured for two different pressure waveforms before and after induced mitral valve failure. Four hearts were further repaired and tested. Measurements were compared with echocardiographic images.

Results: For all trials, cardiac output decreased as left ventricular pressure was increased. After induction of mitral valve insufficiencies, cardiac output decreased, with a peak regurgitant fraction of 71.8%. Echocardiography clearly showed increases in regurgitant severity from post-valve failure and with increased pressure.

Conclusions: The dynamic heart model consistently and reliably quantifies mitral regurgitation across a range of severities. Advantages include low experimental cost and time associated with each trial, while still allowing for surgical evaluations in an intact heart.

FIGURE 1

The proposed system. Left: photograph of the system in operation. Right: schematic of system components: atrial filling reservoir (1), PD pump (2), pressure catheters (3), centrifugal pump (4), aortic outflow resistance valve (5), and static pressure mode valves (6). Dynamic and static pressure mode pathways are shaded light and dark, respectively.

FIGURE 2

Heart connected to system, showing left ventricle (LV), right ventricle (RV), left atrium (LA), left atrial appendage (LAA), and aorta (AOR).

FIGURE 3

Pump trajectory used to obtain 60 bpm HR, 35 mL PV, and 35% SF.

FIGURE 4

Pressure waveform comparisons: (a) normal and damaged valve with 120 mmHg pLVP; and (b) normal and damaged valve with 150 mmHg pLVP.

FIGURE 5

Color doppler images of left atrium (LA) and left ventricle (LV) during peak systole: (a) normal valve, 120 mmHg pLVP; (b) normal valve, 150 mmHg pLVP; (c) failed valve, 120 mmHg pLVP; and (d) failed valve, 150 mmHg pLVP.

FIGURE 6

Endoscopic images showing states of open and closed mitral valve. (a) normal; (b) damaged (arrow depicts flail leaflet); and (c) repaired. Functional aortic valve is also shown (d).

FIGURE 7

Endoscopic images of repair problems discovered during testing. (a) Loose suture knot revealed during dynamic testing; (b) location where annuloplasty ring has pulled away from the annulus, indicating either incorrect suture placement or a knot that was not tightened properly.