FURTHER INCREASE IN OXYGEN-UPTAKE DURING EARLY ACTIVE RECOVERY FOLLOWING MAXIMAL EXERCISE IN CHRONIC HEART-FAILURE

Study objective: Some patients with chronic heart failure manifest a f urther increase in oxygen uptake (VO2) after maximal exercise whereas others do not. The purpose of this study was to determine the characte ristics of chronic heart failure patients with further increase in VO2 in early active recovery following maximal exercise. Design: Retrospe ctive analysis of clinical and exercise testing characteristics in pat ients with or without a further increase in Vo(2) during early active recovery. Patients: One hundred forty-two patients with a history of c ongestive heart failure and left ventricular ejection fraction of 45%, or less who performed a symptom-limited graded treadmill exercise tes t. Measurements and results: Expired gases were monitored breath by br eath from rest throughout exercise and during 1 min of active recovery . Patients were defined as having a further increase in VO2 if the ave rage VO2 during the initial 30 s of active recovery was greater than o r equal to VO2 during the final 30 s of graded exercise and the instan taneous VO2 (from the breath-by-breath plot) at 30 s of active recover y was greater than or equal to the instantaneous VO2 at peak exercise. Thirty patients (21%) showed a further increase in VO2 following peak exercise (group 1), and 112 had decreased VO2 at 30 s after peak exer cise (group 2). In group 1, treadmill time was significantly shorter, peak VO2 was significantly lower (16.6+/-3.6 vs 21.6+/-6.4 ml/kg/min), and peak ventilatory equivalent for carbon dioxide (VE/VCO2) was sign ificantly higher than those in group 2. There was no difference in eti ology of heart failure or functional class and medication status. Conc lusion: A further increase in VO2 during early active recovery was ass ociated with poorer exercise tolerance, lower peak VO2, and higher pea k VE/VCO2 in chronic heart failure patients. This sign may be a new fu nctional variable for assessment of chronic heart failure. Further inv estigations are warranted to clarify the mechanisms and clinical impli cations of this phenomenon.