Left ventricular pump function in right ventricular overload.

To clarify how left ventricular pumping action is altered in cor pulmonale, an experimental study was performed using canine heart preparations in which the effects on left ventricular performance of right ventricular overload, with and without depressed systolic function, were investigated. For this purpose, two methods using excised perfused hearts (n = 16) and in vivo hearts (n = 6) were employed, and in the latter condition, pulmonary artery constriction (n = 7), femoral arterial-venous (A-V) shunt (n = 3) and right coronary artery occlusion (n = 6) were induced. Left ventricular systolic function was assessed by the relationship between left ventricular isovolumic developed pressure and left ventricular volume in excised heart, and by ejection fraction with 2 dimensional echocardiogram in the vivo condition, taking into account preload and afterload changes. From the excised heart preparation, it was shown that left ventricular developed pressure significantly decreases when right and left ventricular diastolic pressure increases greatly. On the other hand, in vivo right ventricular overload due to pulmonary constriction and A-V shunt, the left ventricular ejection fraction increased following afterload reduction. When we compare the left ventricular ejection fraction in pulmonary constriction with that in right coronary occlusion, in which reduction of left ventricular diastolic area from the control was similar, the latter was significantly decreased despite afterload reduction. These results suggest that right ventricular overload does not necessarily induce left ventricular systolic dysfunction unless left ventricular end-diastolic pressure, as well as that of the right ventricle, increases definitely and simultaneously.(ABSTRACT TRUNCATED AT 250 WORDS)