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Effects of therapeutic interventions on minimal cardiac transit times and volume parameters in hypertrophic
1Dept. of Cardiology, Pneumology and Angiology, University of Düsseldorf, F.R.G.
Insights
Hypertrophic cardiomyopathy impairs heart function, particularly atrial ejection, worsening during exercise. Surgical myectomy improves left ventricular function in obstructive cases.
Area of Science:
- Cardiology
- Nuclear Medicine
- Physiology
Background:
- Hypertrophic cardiomyopathy (HCM) encompasses obstructive (HOCM) and non-obstructive (HNCM) forms.
- Diastolic dysfunction and impaired atrial function are key features in HCM.
- Understanding hemodynamic changes during exercise is crucial for HCM management.
Purpose of the Study:
- To investigate cardiac function and hemodynamics in HOCM and HNCM patients at rest and during exercise.
- To assess the impact of impaired atrial ejection on ventricular filling.
- To evaluate the effects of transaortal septal myectomy on cardiac function in HOCM.
Main Methods:
- Simultaneous measurement of pulmonary artery pressure and minimal transit times (MTTs) using indium-113m-EDTA.
- In vivo assessment at rest and during supine exercise.
- Comparison of MTTs between HOCM, HNCM patients, and surgical outcomes.
Main Results:
- At rest, prolonged atrial MTTs indicated impaired atrial ejection, while ventricular MTTs were normal.
- Exercise aggravated atrial MTT prolongation and increased pulmonary artery pressure, suggesting worsened ventricular inflow impairment.
- No significant quantitative differences were found between HOCM and HNCM, highlighting the role of diastolic dysfunction.
- Septal myectomy improved left ventricular MTTs and reduced left atrial/pulmonary MTTs in HOCM patients.
Conclusions:
- Impaired atrial ejection is a significant pathophysiological factor in HCM, irrespective of outflow obstruction.
- Exercise exacerbates diastolic dysfunction and atrial filling problems in HCM.
- Surgical septal myectomy can improve left ventricular function and reduce atrial/pulmonary pressures in HOCM.
Abstract:
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)