Relationship between peak cardiac pumping capability and selected exercise‐derived prognostic indicators in patients treated with left ventricular assist devices

Abstract

Exercise-derived variables have been used in the assessment of functional capacity and prognosis in patients with chronic heart failure. The aim of this study was to assess the relationship between cardiac pumping capability represented by peak cardiac power output and peak oxygen consumption, anaerobic threshold, ventilatory efficiency slope, and peak circulatory power in patients undergoing the 'Harefield Protocol'. Haemodynamic and gas exchange measurements were undertaken during a graded treadmill exercise test. They were performed on 54 patients-18 implanted with left ventricular assist devices (LVADs), 16 explanted (recovered), and 20 moderate-to-severe heart failure patients. Peak oxygen consumption was only highly correlated with peak cardiac power output in explanted LVAD (r = 0.85, P< 0.01), but not in implanted LVAD and heart failure patients (r = 0.55 and 0.53, P< 0.05). The anaerobic threshold was only modestly correlated with peak cardiac power output in heart failure and explanted (r = 0.46 and 0.54, P< 0.05) and weakly in implanted LVAD patients (r = 0.37, P< 0.05). Peak cardiac power output was well correlated with peak circulatory power in LVAD explanted and implanted (r = 0.82, P< 0.01; r = 0.63, P< 0.01) but not in heart failure patients (r = 0.31, P> 0.05). Ventilatory efficiency slope was only moderately correlated with peak cardiac power output in LVAD-explanted patients (r = -0.52, P< 0.05). Exercise-derived prognostic indicators demonstrate limited capacity in reflecting cardiac pumping capability in patients treated with LVADs and should therefore be used with caution in interpretation of cardiac organ function.