Introduction Left ventricular assist devices (LVADs) have been used as an effective therapeutic option in patients with advanced heart failure either as a bridge to transplantation, as destination therapy or as a bridge to recovery. Most recently it has been shown that the use of continuous-flow LVAD (HeartMate II) improves the rate of survival, quality of life, and functional capacity of patients as compared with the pulsatile-flow LVAD. To date, no study has reported how well HeartMate II can improve organ function and patients' exercise ability. The present project aimed to assess cardiac and exercise performance of patients implanted with continuous-flow LVADs under two conditions: (i) optimal device support, and (ii) reduced device support. These results were compared with those of LVAD explanted (recovered) patients, heart transplant candidates and healthy controls.
Methods Fifty-eight male patients, 18 implanted with a HeartMate II LVAD, 16 LVAD explanted patients and 24 heart transplant candidates (HTx) and 101 healthy controls performed graded cardiopulmonary exercise test with respiratory gas exchange and noninvasive (rebreathing) haemodynamic measurements. Twelve of the 18 LVAD implanted patients performed an additional cardiopulmonary exercise test with reduced LVAD support (pump speed reduced from optimal 9000–9600 revs/min to 6000 revs/min).
Results At lower HeartMate II support, peak exercise cardiac power output was 39% lower (1.42±0.41 vs 2.31±0.50 W; p<0.05), peak cardiac output 30% lower (8.6±2.31 vs 12.2±1.55 l/min; p<0.05), and mean blood pressure 13% lower (74±7 vs 85±12 vs mmHg; p<0.05). Exercise capacity was also diminished with 23% lower peak oxygen consumption (14.1±5.3 vs 18.2±4.5 ml/kg/min; p<0.05) and 18% shorter exercise duration (516±179 vs 628±142 s; p<0.05). Peak cardiac power output was significantly higher in the LVAD explanted than in the HTx and the LVAD implanted patients (HTx: 1.31±0.31 W; implanted: 2.31±0.50 W; explanted: 3.39±0.61 W; p<0.01) as was peak cardiac output (HTx: 8.0±1.5; implanted: 12.2±1.55 explanted, 14.6±2.9 l/min; p<0.01). Peak oxygen consumption was higher in the LVAD explanted than the HTx and the implanted patients (HTx, 12.5±2.5; implanted, 18.2±4.5; explanted, 28.2±5.0 ml/kg/min; p<0.05) as was oxygen consumption at anaerobic threshold (p<0.05). In the explanted cohort, 38% achieved peak cardiac power output and 69% peak oxygen consumption within the ranges of healthy controls.
Conclusion We have shown for the first time that complementary to reported prognostic benefits, non-pulsatile continuous-flow LVAD pumps can confer cardiac functional benefits to patients with end-stage heart failure to derive improved exercise capacity, while those who recovered sufficiently to allow explantation of LVADs can even achieve cardiac and physical functional capacities nearly equivalent to those of healthy controls.
- cardiac power
- exercise performance