[Anaerobic threshold detected using "V-slope analysis" in chronic chagasic disease]

Anaerobic threshold (AT) as measured by V-slope, is the best parameter of cardiac reserve in patients with heart failure. A reduction of AT reflects linearly a limited cardiopulmonary reserve in patients with heart disease. We measured the anaerobic threshold from 28 patients (18 men; age 47 +/- 6.7 years) classified into four groups: IA (normal ECG, without heart disease; 9 patients); IB (normal ECG, early left ventricular segmental abnormalities; 5 patients); II (abnormal ECG, advanced myocardial damage, no signs of heart failure, 7 patients); and III (abnormal ECG, end-stage, congestive heart failure; 7 patients). The analysis of variance indicated that the anaerobic threshold from patients of group LA was significantly greater than in groups IB, II and III (p = 0.001). Tukeys multiple comparison test showed no significative differences between mean AT in groups IB, II and III. The present study clearly demonstrates that occurrence of initial left ventricular contraction abnormalities is associated with definite reduction of cardiopulmonary reserve, and that this reduction is progressive and parallels the hemodynamic alterations. The most probable cause of this finding in group IB is diastolic dysfunction as clearly shown in echocardiogram.