Left Ventricular volumes during exercise in normal subjects and patients with dilated cardiomyopathy assessed by first-pass radionuclide angiography

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During isotonic exercise, left ventricular (LV) suction and the Frank-Starling law of the heart may have important roles in the enhancement of early LV diastolic filling and in the increase of myocardial contractility, respectively. It remains controversial whether these mechanisms operate in normal subjects or patients with dilated cardiomyopathy. Ten healthy subjects and 10 patients with idiopathic dilated cardiomyopathy who underwent maximal upright bicycle exercise testing were studied. First-pass radionuclide angiography was performed at both rest and peak exercise using a multicrystal gamma camera. In normal subjects, LV end-systolic volume at peak exercise was smaller than during baseline (17 ± 7 vs 30 ± 15 ml/m 2; p < 0.05), whereas rapid filling volume was greater (52 ± 16 vs 38 ± 8 ml/m 2; p < 0.01). In patients with dilated cardiomyopathy, both end-systolic (108 ± 34 to 123 ± 53 ml/m 2; p = NS) and rapid filling (24 ± 6 to 28 ± 9 ml/m 2; p = NS) volumes did not change from rest to peak exercise. A significant correlation was found between the changes in end-systolic volume at peak exercise and in peak rapid filling rate in normal subjects (r = 0.6; p < 0.05), but not in patients with dilated cardiomyopathy (r = 0.3; p = NS). In normal subjects, end-diastolic volume at peak exercise was similar to that during baseline (78 ± 14 and 85 ± 15 ml/m 2, respectively; p = NS), whereas in patients with dilated cardiomyopathy, it was greater (164 ± 50 vs 146 ± 33 ml/m 2; p < 0.05). This study shows that during exercise, cardiac suction may have a role in the enhancement of early diastolic filling in normal subjects, as indicated by a significant correlation between the changes in end-systolic volume and peak rapid filling rate, but not in patients with dilated cardiomyopathy. Conversely, the Frank-Starling law of the heart operates in patients with dilated cardiomyopathy, as suggested by the increase in LV end-diastolic volume, but not in normal subjects.