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 ven tricles are known to play important roles as determinants of ventricul ar function, and the purpose of this study was to evaluate their effec ts in a model of heart failure. Methods and Results A dilated cardiomy opathy resulting in congestive heart failure (CHF) was produced in pig s by rapid ventricular pacing at 230 beats per minute for 1 week. Bloo d was rapidly withdrawn from the left ventricular (LV) apex into a pro sthetic ventricle, and the instantaneous effects on the right ventricl e were studied during volume loading and before and after pericardiect omy. The systolic interaction gain between the right and left ventricl es (G(s)) was calculated as the ratio of changes in mean systolic pres sure during isolated systolic LV unloading. Diastolic ventricular inte raction gain (G(d)) was calculated as the ratio of changes in mean dia stolic pressures during LV unloading in the last 150 ms of diastole. W ith the pericardium closed, all interaction gains were significantly i ncreased 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 pi gs) and G(d) from 0.196+/-0.116 to 0.493+/-0.117 mm Hg/mm Hg (normal p igs) and from 0.174+/-0.101 to 0.341+/-0.165 (CHF pigs). When the peri cardium was opened, G(d) was significantly reduced to 0.145+/-0.071 an d 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 H g/mm Hg for normal and CHF pigs, respectively), and both were also sig nificantly increased during volume loading. G(s) was significantly gre ater in CHF versus normal pigs under all conditions, but there were no differences in G(d) between CHF and normal pigs. Conclusions These re sults suggest that dilated cardiomyopathy increases systolic but not d iastolic interactions, that the pericardium increases diastolic but no t systolic ventricular interactions, and that volume loading with and without the pericardium opened increases both systolic and diastolic i nteractions.