A new approach to in situ left ventricular volume clamping in dogs

Major contributing factors modulating left ventricular (LV) diastolic behavior are active relaxation of myocardium and volume change during filling, the interaction of which complicates analysis of diastolic pressure-volume relationship, especially in early diastole. To separate the effect of active relaxation and filling, a method was introduced [E. L. Yellin, M. Hori, C. Yoran, E. H. Sonnenblick, S. Gabbay, R. W. M. Frater, Am. J. Physiol. 250 (Heart Circ. Physiol. 19): H620-H629, 1986] to interrupt mitral inflow and keep LV volume constant throughout diastole. Their preparation requires replacing the mitral valve with an artificial valve using cardiopulmonary bypass, which might cause significant change in cardiac performance or produce detrimental systemic effects. We developed a new volume-clamping method that preserves the native mitral valve and apparatus intact and avoids cardiopulmonary bypass. A modified Bjork-Shiley prosthetic valve (20 mm orifice diam) in a special mounting ring was placed above the native mitral valve through the left atrium and secured from outside the heart. This prosthetic valve was controlled by a cable connected to solenoids outside the dog, triggered by the electrocardiogram or other physiological signal. We compared our method (n = 7) with that of Yellin et al. (n = 2) in nine random source dogs. In our method, no end-diastolic pressure gradient or regurgitant pressure wave was observed, and the prosthetic valve did not disturb movement of the native mitral valve. When the prosthetic valve was forced to a closed position at end systole, LV volume, measured with a conductance catheter, was maintained at or near end-systolic volume throughout diastole.(ABSTRACT TRUNCATED AT 250 WORDS)