ISOLATED SYSTOLIC AND DIASTOLIC VENTRICULAR INTERACTIONS IN PACING-INDUCED DILATED CARDIOMYOPATHY AND EFFECTS OF VOLUME LOADING AND PERICARDIUM

Background Interactions between the closely coupled right and left ventricles are known to play important roles as determinants of ventricular function, and the purpose of this study was to evaluate their effects in a model of heart failure. Methods and Results A dilated cardiomyopathy resulting in congestive heart failure (CHF) was produced in pigs by rapid ventricular pacing at 230 beats per minute for 1 week. Blood was rapidly withdrawn from the left ventricular (LV) apex into a prosthetic ventricle, and the instantaneous effects on the right ventricle were studied during volume loading and before and after pericardiectomy. The systolic interaction gain between the right and left ventricles (G(s)) was calculated as the ratio of changes in mean systolic pressure during isolated systolic LV unloading. Diastolic ventricular interaction gain (G(d)) was calculated as the ratio of changes in mean diastolic pressures during LV unloading in the last 150 ms of diastole. With the pericardium closed, all interaction gains were significantly increased during volume loading from a right ventricular end-diastolic pressure of 3 to 9 mm Hg: G(s) from 0.045+/-0.014 to 0.063+/-0.020 mm Hg/mm Hg (normal pigs) and from 0.077+/-0.040 to 0.103+/-0.019 (CHF pigs) and G(d) from 0.196+/-0.116 to 0.493+/-0.117 mm Hg/mm Hg (normal pigs) and from 0.174+/-0.101 to 0.341+/-0.165 (CHF pigs). When the pericardium was opened, G(d) was significantly reduced to 0.145+/-0.071 and 0.129+/-0.026 mm Hg/mm Hg (normal and CHF pigs, respectively), but G(s) showed no significant change (0.067+/-0.027 and 0.109+/-0.012 mm Hg/mm Hg for normal and CHF pigs, respectively), and both were also significantly increased during volume loading. G(s) was significantly greater in CHF versus normal pigs under all conditions, but there were no differences in G(d) between CHF and normal pigs. Conclusions These results suggest that dilated cardiomyopathy increases systolic but not diastolic interactions, that the pericardium increases diastolic but not systolic ventricular interactions, and that volume loading with and without the pericardium opened increases both systolic and diastolic interactions.