Abstract
Thirty-three patients with pure mitral stenosis were studied by radiocardiography and cardiac catheterization to assess changes in blood flow and the distribution of circulating blood. Radiocardiograms were analyzed by Kuwahara's model using an analog computer. The volumes of the right heart, lung, left heart and the rest of the whole circulatory system were obtained, as well as the cardiac output and the circulating blood volume (BV). Stroke index (SI) showed a tendency to decrease with diminished mitral valve area (MVA). In the presence of atrial fibrillation SI was 28% smaller than that of patients with sinus rhythm. The contribution of atrial contraction to the flow was inferred to be larger than in the normal hemodynamic state. A rough linear correlation was found between mean right heart volume (RHV) and mean pulmonary arterial pressure (PAm) (r=+0.69). The relationship between RHV and MVA was smaller than 1 cm2. Increase in mean left heart volume (LHV) was found but was not so prominent as that in RHV. The ratio of RHV to LHV showed a good linear correlation with PAm (r=+0.81). Significant increase in pulmonary blood volume (PBV) was found. Multiple regression analysis revealed that in the group with lower pulmonary arteriolar resistance (PAR < 250 dynes·sec·cm-5) the major determinants of PBV were BV and mean intravascular pressure (Pi). In the group with higher PAR (PAR⩾250) determinants were BV and PAR, while Pi was not important. These findings suggest a decreased distensibility of the pulmonary vascular bed in patients with pulmonary hypertension. The present study revealed that severe mitral stenosis with pulmonary hypertension is associated with decreased pulmonary vascular distensibility, and that the sustained pressure load on the right ventricle leads to dilatation of the right chambers of the heart and to right ventricular failure.
