Effects of Chronic Right Ventricular Volume and Pressure Loading on Left Ventricular Performance

The effects of chronic right ventricular (RV) distension on left ventricular (LV) function were assessed in dogs 3 weeks after pressure and volume loading of the RV had been produced by the emplacement of a constricting band around the pulmonary artery and the creation of tricuspid insufficiency. This resulted in ascites, RV hypertrophy and dilatation, an increase in RV end-diastolic pressure (EDP), and a reduction of RV and LV norepinephrine concentrations. Peak LV pressure, wall stress, and dp/dt were measured during isovolumic beats at LVEDP's of 1 to 20 mm Hg, and comparisons at matched EDP's were made among the normal, sham-operated, and RV stressed dogs. Under these circumstances, LV function appeared to be depressed appreciably. The effects of RV volume loading on the pressure-volume curve of the LV in the potassium-arrested heart were assessed in a separate group of dogs. The pressure-volume curve of the LV was shifted so that any given LV volume was associated with a higher LV pressure. Thus, when peak pressure and wall stress were related to LV end-diastolic volume rather than to LVEDP, the relationship did not appear to differ from normal; peak dp/dt and peak V CE , however, remained depressed. This depression may represent a decrease in LV contractility consequent to the chronic RV stress or may reflect alterations in LV geometry. Thus, when the RV is subjected to a chronic flow and pressure load, assessment of LV function may be unreliable when indices of contractility are employed that require measurements of LVEDP.