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 further increase in oxygen uptake (V̇O₂) 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 V̇O₂ in early active recovery following maximal exercise. Design: Retrospective analysis of clinical and exercise testing characteristics in patients with or without a further increase in V̇O₂ during early active recovery. Patients: 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. Measurements and results: 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 V̇O₂ if the average V̇O₂ during the initial 30 s of active recovery was greater than or equal to V̇O₂ during the final 30 s of graded exercise and the instantaneous V̇O₂ (from the breath-by-breath plot) at 30 s of active recovery was greater than or equal to the instantaneous V̇O₂ at peak exercise. Thirty patients (21%) showed a further increase in V̇O₂ following peak exercise (group 1), and 112 had decreased V̇O₂ at 30 s after peak exercise (group 2). In group 1, treadmill time was significantly shorter, peak V̇O₂ was significantly lower (16.6±3.6 vs 21.6±6.4 mL/kg/min), and peak ventilatory equivalent for carbon dioxide (V̇E/V̇CO₂) was significantly higher than those in group 2. There was no difference in etiology of heart failure or functional class and medication status. Conclusion: A further increase in V̇O₂ during early active recovery was associated with poorer exercise tolerance, lower peak V̇O₂, and higher peak V̇E/V̇CO₂ 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.