LEFT-VENTRICULAR VOLUMES DURING EXERCISE IN NORMAL SUBJECTS AND PATIENTS WITH DILATED CARDIOMYOPATHY ASSESSED BY 1ST-PASS RADIONUCLIDE ANGIOGRAPHY

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 contra ctility, respectively. It remains controversial whether these mechanis ms operate in normal subjects or patients with dilated cardiomyopathy. Ten healthy subjects and 10 patients with idiopathic dilated cardiomy opathy who underwent maximal upright bicycle exercise testing were stu died. First-pass radionuclide angiography was performed at both rest a nd peak exercise using a multicrystal gamma camera. In normal subjects , LV end-systolic volume at peak exercise was smaller than during base line (17 +/- 7 vs 30 +/- 15 ml/m2; p < 0.05), Whereas rapid filling vo lume was greater (52 +/- 16 vs 38 +/- 8 ml/m2; p < 0.01). In patients dilated cardiomyopathy, both end-systolic (108 +/- 34 to 123 +/- 53 ml /m2; p = NS) and rapid filling (24 +/- 6 to 28 +/- 9 ml/m2; p = NS) vo lumes did not change from rest to peak exercise. A significant correla tion was found between the changes in end-systolic volume at peak exer cise 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 simil ar to that during baseline (78 +/- 14 and 85 15 ml/m2, respectively; p = NS), whereas in patients with dilated cardiomyopathy, it was greate r (164 +/- 50 vs 146 +/- 33 ml/m2; p < 0.05). This study shows that du ring exercise, cardiac suction may have a role in the enhancement of e arly diastolic filling in normal subjects, as indicated by a significa nt correlation between the changes in end-systolic volume and peak rap id filling rate, but not in patients with dilated cardiomyopathy. Conv ersely, the Frank-Starling law of the heart operates in patients with dilated cardiomyopathy, as suggested by the increase in LV end-diastol ic volume, but not in normal subjects.