Determinants of the relation between systolic pressure and duration of isovolumic relaxation in the right ventricle.

Previous studies have suggested that right ventricular systolic pressure can be predicted from noninvasive estimates of the interval between pulmonary valve closure and tricuspid valve opening. To determine the basis for this relation, phonocardiograms and high fidelity right atrial and ventricular pressures were recorded in 29 patients with a right ventricular systolic pressure ranging from 20 to 149 mm Hg. In 22 patients with normal right atrial pressure (less than or equal to 8 mm Hg), both the time interval and the magnitude of pressure decrease from pulmonary valve closure to tricuspid valve opening were linearly related to systolic pressure (r = 0.89 and 0.96, respectively). Early pulmonary valve closure (decreased "hang-out" time) contributed to the greater magnitude of isovolumic pressure decrease at high systolic pressures, but correction for hang-out time did not eliminate the relation between systolic pressure and the pulmonary valve closure-tricuspid valve opening interval (n = 10). When patients with documented right coronary artery disease were excluded, the time constant for isovolumic pressure decrease also increased as a function of systolic pressure (r = 0.67, p less than 0.01, n = 24), suggesting impaired relaxation at high systolic pressures. However, the mean rate of pressure decrease (mean negative dP/dt) still was greater in patients with a high pressure because of the exponential nature of the isovolumic pressure-time relation.(ABSTRACT TRUNCATED AT 250 WORDS)