Right ventricular diastolic pressure-volume relations and regional dimensions during acute alterations in loading conditions.

Acute pharmacologically mediated parallel shifts in the left ventricular diastolic pressure-volume relation may be due to the restraining effect of the pericardium and/or leftward displacement of the interventricular septum. The existence and cause of this phenomenon in the right ventricle has not been studied in animals or in man. Accordingly, we altered right ventricular pressure with intravenous phenylephrine (0.2 to 0.3 mg) and nitroprusside (0.5 to 1.5 micrograms/kg/min) to achieve three disparate peak right ventricular pressures in nine normal subjects after partial autonomic blockade with atropine (1 mg) and propranolol (0.15 mg/kg). Simultaneous high-fidelity right ventricular pressures and biplane cineventriculographic volumes were acquired during the three resultant loading conditions. Right atrial pacing maintained heart rate constant at each pressure level. Peak right ventricular systolic pressure (23 +/- 3 vs 31 +/- 9 vs 45 +/- 6 mm Hg, all p less than .01) and right ventricular end-diastolic...