Effects of therapeutic interventions on minimal cardiac transit times and volume parameters in hypertrophic cardiomyopathy

45 patients with hypertrophic obstructive cardiomyopathy (HOCM) and 18 patients with hypertrophic non-obstructive cardiomyopathy (HNCM) underwent simultaneous measurements of pulmonary artery pressure and minimal transit times (MTTs) of an intravenously injected bolus of indium-113m-EDTA through the heart at rest and during exercise in supine position. At rest, rate-corrected left and right ventricular MTTs were in the lower normal range, whereas left atrial and, to a lesser degree, right atrial MTTs were abnormally prolonged, indicative of high ventricular ejection fractions and impaired atrial ejection. During exercise, ventricular MTTs rose slightly but remained within the normal range, which corresponds to a slight fall in ventricular ejection fractions. Atrial MTTs exhibited, in contrast, a substantial further prolongation. Together with an abnormal increase in pulmonary artery pressure in the majority of patients, these findings suggest an aggravation of inflow impairment to both ventricles during exercise. There was no quantitative difference between HOCM and HNCM patients suggesting that impaired atrial ejection due to impaired diastolic function is of major pathophysiological importance irrespective of a possible additional role of left ventricular outflow obstruction in HOCM. The influence of surgical therapy (transaortal septal myectomy) was studied in 12 patients with HOCM. A significant increase in left ventricular MTTs to the upper normal range, indicative of a depression of left ventricular ejection fractions to the lower normal range, and a significant shortening of left atrial and pulmonary MTTs were observed, whereas corresponding changes in the right heart were not significant.(ABSTRACT TRUNCATED AT 250 WORDS)