Hemodynamic studies before and after instrumental mitral commissurotomy. A reappraisal of the pathophysiology of mitral stenosis and the efficacy of mitral valvotomy.

Abstract

Hemodynamic studies including simultaneous right heart, transseptal left heart, and retrograde left heart catheterizations were done on 35 patients before and at least 6 months after instrumental mitral commissurotomy to evaluate the efficacy of this type of surgery and to enhance our understanding of the pathophysiology of mitral stenosis. Although surgery produced a significant increase in calculated mitral valve area, the degree of improvement varied markedly. The younger patients had the greater increase in mitral valve area. The change in cardiac index and pulmonary vascular resistance correlated well with the change in mitral valve area. Only those patients whose mitral valve area increased over 1.0 cm 2 had a significant increase in cardiac index and a fall in pulmonary vascular resistance. The data indicate that the reduced cardiac index and elevated pulmonary vascular resistance in patients with mitral stenosis are related to the mitral valve obstruction and are at least in part reversible and that the elevated pulmonary vascular resistance during mild exercise is related to elevated left atrial pressure. An almost universal fall in left atrial and pulmonary artery pressures followed surgery, but this apparent improvement did not necessarily correlate with an increase in mitral valve area. A significant increase in exercise left ventricular end-diastolic pressure in patients who had the greatest increase in mitral valve area raises the question as to the status of the left ventricle in patients with mitral stenosis. Decreased left ventricular compliance is offered as a possible explanation for this observation. The concomitant existence of mild or moderate preoperative aortic insufficiency in eight of the patients and the development of significant mitral insufficiency in seven of the 35 patients following surgery did not alter the surgical results significantly. Whether the poorer results in patients with atrial fibrillation were a result of age or the arrhythmia could not be determined.