PRESSURE AND VOLUME LOADING OF THE RIGHT VENTRICLE HAVE OPPOSITE EFFECTS ON LEFT-VENTRICULAR EJECTION FRACTION

Background Left ventricular ejection fraction has been reported to be depressed in patients with right ventricular volume overload (RVVO) du e to Ebstein's anomaly and uncomplicated atrial septal defect, whereas it is usually preserved in right ventricular pressure overload (RVPO) due to congenital pulmonic stenosis. In the present study, we examine d the hypothesis that the differential timing of active displacement o f the ventricular septum into the left ventricle in RVPO (end systole) and RVVO (end diastole) results in opposite effects of RVPO and RVVO on left ventricular ejection fraction. Methods and Results Ten patient s with severe tricuspid regurgitation after tricuspid valve resection for endocarditis and 10 patients with primary pulmonary hypertension w ere studied as models of isolated RVVO and RVPO, respectively. Left ve ntricular ejection fraction, end-diastolic volume, and regional systol ic shortening were measured with the use of echocardiographic techniqu es in these 20 patients and 10 healthy control subjects. In RVPO, desp ite marked underfilling of the left ventricle relative to the healthy control subjects (end-diastolic volume, 48+/-26 versus 77+/-20 mL; P<. 02), left ventricular ejection fraction was similar to that of the con trol subjects (56+/-5% versus 60+/-4%; P=.07) and only 1 of 10 RVPO pa tients had an ejection fraction of less than 50%. In contrast, in RVVO the left ventricle was volume replete (end-diastolic volume, 84+/-26 versus 77+/-20 mL; P=NS), but left ventricular ejection fraction was s ignificantly depressed (51+/-4% versus 60+/-4%, P<.001) compared with the control subjects, and 4 of 10 RVVO patients had an ejection fracti on of less than 50%. Analysis of systolic fractional shortening along two perpendicular short-axis diameters and the mutually orthogonal lon g axis demonstrated isolated augmentation of fractional shortening in the ventricular septal-to-posterolateral free wall dimension in RVPO ( 47.4+/-13.7% versus 34.2+/-13.1%, P<.05) and isolated depression of fr actional shortening along that same dimension in RVVO (13.7+/-11.8% ve rsus 34.2+/-13.1%, P<.001) compared with the control subjects. Conclus ions End-systolic leftward ventricular septal shift in RVPO results in isolated augmentation of systolic shortening in the septal-to-free wa ll dimension, whereas end-diastolic leftward ventricular septal shift in RVVO results in isolated reduction in systolic shortening in the se ptal-to-free wall dimension. As a result, despite relative underfillin g of the left ventricle in RVPO, resting left ventricular ejection fra ction is preserved, whereas ejection fraction is depressed for the vol ume-replete left ventricle of patients with RVVO.