OBJECTIVES: This study sought to characterize the hemodynamic response to exercise in LVAD-supported patients and identify parameters most strongly associated with peak oxygen consumption (VO2).
BACKGROUND: Despite improved survival for heart failure patients afforded by continuous flow left ventricular assist devices (LVADs), peak exercise capacity remains impaired. Mechanisms underlying this reduced functional capacity remain poorly understood.
METHODS: Patients referred for post-VAD hemodynamic optimization from December 2017 through June 2019 were enrolled. Swan Ganz catheters were inserted and upright incremental bicycle ergometry with respiratory gas analysis was performed. Hemodynamic measurements, mixed venous saturation, and arterial blood pressure were recorded every 3 min during exercise. Linear correlations were performed between peak VO2 (ml/min) and peak Fick cardiac output (CO), peak device flow, the assumed intrinsic CO derived as Fick CO-device flow, peak pressure differential across the LVAD (mean arterial pressure-pulmonary capillary wedge pressure), peak pressure differential across right ventricle (mean pulmonary artery pressure – right atrial pressure) and systemic vascular resistance.
RESULTS: Forty-five patients supported by axial flow pumps (n = 12) and centrifugal flow pumps (n = 33) were studied. There were 34 men and 11 women. Age averaged 60 +/- 10 years. Peak VO2 averaged 10.6 +/- 3.1 ml/kg/min. Fick CO had the greatest correlation with peak VO2 with r = 0.73 (p < 0.0001) followed by intrinsic CO (r = 0.67; p < 0.0001). Multivariate model that best predicted peak VO2 included Fick CO and peak arterial venous oxygen (AVO2) difference.
CONCLUSIONS: LVAD supported patients have severely impaired peak exercise capacity. The peak Fick cardiac output was the best correlate of peak exercise performance.