- C Greyson: San Francisco Department of Veterans Affairs Medical Center, CA, USA. greyson@cardio.ucsf.edu
OBJECTIVE: Acute pulmonary hypertension may cause right ventricular (RV) contractile failure. While it has been assumed that restoration of normal loading conditions after acute pulmonary hypertension is sufficient for complete recovery of RV function, this has not been rigorously examined. The purpose of this study was to test the hypothesis that acute RV pressure overload produces RV contractile dysfunction that persists following restoration of control loading conditions.
METHODS: We subjected 18 autonomically-blocked, chloralose-anesthetized, open-chest pigs to 1 h of pulmonary artery constriction to increase RV systolic pressure from 35 +/- 1 to 55 +/- 1 mmHg, followed by 2 h of measurements after pulmonary artery constriction release. We determined regional RV free wall function from pressure-segment length loops and preload recruitable stroke work relations, and global RV function from stroke work vs. end-diastolic pressure relations.
RESULTS: As expected, RV free wall systolic shortening diminished during pulmonary artery constriction, but the endo/epi blood flow ratio, lactate uptake, and coronary venous pH were not significantly changed. Following release of pulmonary artery constriction, RV systolic and diastolic pressure returned to control values. Nonetheless, contractile dysfunction persisted, with depressed RV free wall systolic shortening (70 +/- 22% of control), RV regional external work (59 +/- 11% of control at control end-diastolic length), and global RV stroke work (56 +/- 14% of control at control end-diastolic pressure). Depressed regional work was due to a parallel, rightward shift of the preload recruitable stroke work relation. Five pigs identically instrumented but not subjected to pulmonary artery constriction showed no significant over 3 h.
CONCLUSIONS: Acute pulmonary hypertension causes RV contractile dysfunction that persists at least 2 h after restoration of control loading conditions. Contractile dysfunction is not attributable to RV ischemia during pressure overload.