The pathophysiology of failure in acute right ventricular hypertension: hemodynamic and biochemical correlations.

Acute right ventricular (RV) hypertension and failure occur clinically. In this study we examined the mechanism of RV failure. Adult dogs were studied acutely under anesthesia; dogs were instrumented for measurement of pressures and right coronary artery blood flow. Myocardial blood flow and cardiac output were determined with radionuclide-labeled microspheres, and the presence of ischemia was determined by biochemical analysis of ventricular biopsies. RV hypertension was produced by constricting the pulmonary artery and was increased until RV failure occurred, as evidenced by decreased aortic pressure and cardiac output and increased RV end-diastolic pressure. With increasing RV systolic pressure, RV myocardial blood flow failed to increase in proportion to demand. At the onset of RV failure, there was no reactive hyperemia of right coronary flow compared with control, indicating the absence of further coronary vascular reserve; biochemical analysis demonstrated that the RV free wall was ischemic; the LV free wall was not. Infusion of phenylephrine raised aortic pressure and hence, myocardial perfusion pressure; RV failure reversed as shown by decreased RV end-diastolic pressure and increased cardiac output and RV systolic pressure; reactive hyperemia of right coronary flow was restored and the biochemical indexes of ischemia were reversed, demonstrating that ischemia is the cause of failure in acute RV hypertension.