KINETICS OF OXYGEN-CONSUMPTION DURING AND AFTER EXERCISE IN PATIENTS WITH DILATED CARDIOMYOPATHY - NEW MARKERS OF EXERCISE INTOLERANCE WITHCLINICAL IMPLICATIONS

Objectives. This study analyzed the kinetics of oxygen consumption dur ing and after a maximal cardiopulmonary exercise test in patients with dilated cardiomyopathy. The prognostic information derived from index es of recovery was also studied. Background. Previous studies have exa mined the kinetics of oxygen consumption during a short recovery perio d in a limited number of patients. To our knowledge, no study has exam ined the prognostic information derived from indexes of recovery. Meth ods. We studied 153 patients and 55 control subjects, We calculated th e ratio between total oxygen consumption during exercise and recovery, the half-recovery time of peak oxygen consumption, the time constant of recovery, the recovery time and the ratio between duration of exerc ise and recovery time. Results. Recovery of oxygen consumption was sig nificantly delayed in patients, and this delay was related to the degr ee of exercise intolerance. After a median follow-up period of 439 day s, for the total study group, percent of predicted peak oxygen consump tion (p = 0.003) and ejection fraction (p = 0.03) were independent pre dictors of survival. In a subgroup of patients with moderate exercise intolerance (percent peak oxygen consumption >40%), the ratio between total oxygen consumption during exercise and recovery (p = 0.013) and the ejection fraction (p = 0.013) were independent predictors of survi val. Conclusions. The kinetics of oxygen consumption during recovery w as delayed in patients with dilated cardiomyopathy. Although indexes o f recovery were not prognostic markers in the total study group, the r atio between total oxygen consumption during exercise and recovery was an independent prognostic marker in patients with moderate exercise i ntolerance.