Further Increase in Oxygen Uptake During Early Active Recovery Following Maximal Exercise in Chronic Heart Failure

Some patients with chronic heart failure manifest a further increase in oxygen uptake ( V˙o2) after maximal exercise whereas others do not. The purpose of this study was to determine the characteristics of chronic heart failure patients with further increase in V˙o2 in early active recovery following maximal exercise. Retrospective analysis of clinical and exercise testing characteristics in patients with or without a further increase in V˙o2 during early active recovery. One hundred forty-two patients with a history of congestive heart failure and left ventricular ejection fraction of 45%, or less who performed a symptom-limited graded treadmill exercise test. Expired gases were monitored breath by breath from rest throughout exercise and during 1 min of active recovery. Patients were defined as having a further increase in V˙o2 if the average V˙o2 during the initial 30 s of active recovery was greater than or equal to V˙o2 during the final 30 s of graded exercise and the instantaneous V˙o2 (from the breath-by-breath plot) at 30 s of active recovery was greater than or equal to the instantaneous V˙o2 at peak exercise. Thirty patients (21%) showed a further increase in V˙o2 following peak exercise (group 1), and 112 had decreased V˙o2 at 30 s after peak exercise (group 2). In group 1, treadmill time was significantly shorter, peak V˙o2 was significantly lower (16.6±3.6 vs 21.6±6.4 mL/kg/min), and peak ventilatory equivalent for carbon dioxide ( V˙E/V˙co2) was significantly higher than those in group 2. There was no difference in etiology of heart failure or functional class and medication status. A further increase in V˙o2 during early active recovery was associated with poorer exercise tolerance, lower peak V˙o2, and higher peak V˙E/V˙co2 in chronic heart failure patients. This sign may be a new functional variable for assessment of chronic heart failure. Further investigations are warranted to clarify the mechanisms and clinical implications of this phenomenon.