This study was aimed at investigating how the heart adapts to upright exercise in the presence of aortic incompetence. Previous experience has generally been accumulated with supine exercise, which may make some difference. Left ventricular volume has also frequently been estimated by techniques that were inadequate for detection of rapid changes in left ventricular loading conditions and function, especially at maximal exercise. In this study 12 patients (average age of 36 years) with severe chronic aortic Incompetence were studied using two-dimensional echocardiography to obtain left ventricular volume measurements on a beat by beat basis at rest and at the peak of maximal upright bicycle exercise (increasing workload by 25 W every 3 min). Color Doppler images were obtained to monitor aortic regurgitation during exercise. A cardiopulmonary exercise test was also performed 2 days later. In the supine position left ventricular end-diastolic and end-systolic diameters were 65 ± 6 and 43 ± 4 mm, respectively, fractional shortening was 34 ± 3%, the mean values of end-diastolic and end-systolic volume index were 112 ± 28, 46 ± 11 ml/m2 with biplane ejection fraction of 58 ± 4%. In the upright position these values decreased to 99 ± 22 and 40 ± 10 ml/m2 respectively with ejection fraction of: 59 ± 6%. The exercise time was 12.7 ± 3 min. At peak exercise end-diastolic volume index decreased significantly to 81 ± 15 ml/m2 reflecting the reduction of regurgitant volume, while a mild decrease in end-systolic volume index to 37 ± 9 ml/m2 was noted. At peak exercise ejection fraction slightly decreased to 57 ± 6%. Heart rate and systolic blood pressure increased from 77 ± 9 b/min and 145 ± 13 mmHg to 149 ± 14 b/min and 193 ± 28 mmHg respectively at peak exercise. The mean values of oxygen consumption were 26 ± 6 ml/Kg/min at peak and 18 ± 5 ml/Kg/min at the anaerobic threshold. These values reflect a preserved exercise functional capacity. In chronic aortic incompetence the decrease in end-diastolic volume index determines a mild reduction in ejection fraction at peak exercise, probably because of an impairment of the Frank-Starling mechanism. Enhanced heart rate and afterload reduction appear to be the major mechanisms for increasing cardiac output during maximal upright dynamic exercise.
|Number of pages||6|
|Publication status||Published - 1996|
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Radiology Nuclear Medicine and imaging