Left ventricular stroke work in mitral regurgitation: an animal experimental study.

BACKGROUND AND AIMS OF THE STUDY: Most studies on mitral regurgitation have focused on evaluating the regurgitant volume. The effects of mitral regurgitation and its associated cardiac workload on left ventricular function and mechanics may be equally important both in assessing the impact of regurgitation as well as in planning and evaluating therapy. The present study was undertaken to investigate the interrelationships of the regurgitant volume, hemodynamics and left ventricular work in an experimental animal model of chronic mitral regurgitation in which the regurgitant volume could be measured directly with electromagnetic flow probes. METHODS: A total of 21 hemodynamic states were studied in six sheep with surgically created mitral regurgitation. Regurgitant flow rates were obtained from electromagnetic flow meters. Left ventricular and atrial pressures were recorded using high-fidelity catheters. Regurgitant jet velocity was recorded by continuous wave Doppler. Left ventricular stroke work and energy losses due to the regurgitation were calculated. RESULTS: There was a close correlation between left ventricular stroke work and both jet energy and left atrial systolic pressure rise (r = 0.81, p = 0.0001 and r = 0.92, p = 0.0001, respectively). A moderate correlation to the regurgitant volume was found (r = 0.52, p = 0.01). CONCLUSIONS: The regurgitant volume itself is only one of the determinants of left ventricular stroke work in mitral regurgitation. Other factors such as left atrial mechanical properties and the regurgitant kinetic jet energy are at least as important for assessing cardiac work in patients with mitral regurgitation.