Pressure-volume relationship in isolated working heart with crystalloid perfusate in swine and imaging the valve motion

Objective: It is widely accepted that both valve and cardiac functions are closely correlated. In order to investigate the relationship between the valve and cardiac functions, we developed a model of an isolated working heart with crystalloid perfusate in swine. We investigated the feasibility of this model to evaluate the precise left ventricular function using the pressure-volume relationship and metabolic measurement. Another objective was as a trial for the imaging and analysis of valvular interventions with a high-speed digital camera on this model. Methods: Six isolated working hearts were subjected in the pressure-volume study, and additional three hearts were used in the valve imaging study. Measurement of the pressure-volume relationship was undertaken in situ before the heart was removed, and on the working heart mode during the initial 30 min as the baseline, and at every 60 min. Lactate levels were measured at every stage in the working heart mode. Mitral valve interventions were performed in three hearts, and valve motions were observed by a high-speed digital camera via the left ventricle. Results: The end-systolic elastance maintained a baseline level (5.17±2.25) until 180 min and decreased at 240 min (3.97±1.97, NS) and 300 min (2.85±1.29, P<0.01) of the working heart mode as compared with baseline. The Tau maintained a constant level until 180 min and increased at 240 min (62.2±13.3, NS) and 300 min (85.5±43.4, P<0.05) as compared with baseline (50.3±13.6). The slope of the end-diastolic pressure-volume relationship gradually increased with no significance until 180 min and increased significantly (0.147±0.066, P<0.01 vs 0.067±0.041 at baseline). Lactate increased accumulatively. The total heart energy was reduced from the initial phase of the working heart mode. The valves were well captured by the high-speed digital camera. Conclusions: The systolic and diastolic functions of an isolated heart were preserved at an acceptable level for 180 min. The practical reliability of the swine working heart model was demonstrated. This model will be used reliably for the investigation of the interaction of valve and cardiac functions.