Abstract 16579: Oxygen Uptake Kinetics Are Closely Related to Right Ventricular-Pulmonary Vascular Function During Exercise in Heart Failure
Introduction The ability to augment oxygen uptake (VO2) upon initiation of exercise is blunted in patients with heart failure and reduced left ventricular ejection fraction (HFrEF). Delayed O2 kinetics are closely linked to functional capacity and prognosis and may be more relevant than peak VO2 to symptoms elicited during activities of daily living. However, the relative contribution of right ventricular (RV)-pulmonary vascular function versus LV-systemic function to delayed VO2 kinetics in HFrEF is unknown.
Methods and Results 25 patients with symptomatic HFrEF (age 62±2 years, mean LV ejection fraction (LVEF) 31±1%, 88% male, 52% ischemic etiology) underwent cycle ergometry cardiopulmonary exercise testing with hemodynamic monitoring performed throughout exercise, and radionuclide ventriculography performed at rest and at peak exercise. VO2 kinetics were quantified by mean response time (MRT), which is the time needed to reach 63% of steady-state VO2 (Figure, top panel). MRT was inversely related to resting and exercise RVEF (R=-0.59, and R=-0.65, P≤0.005 for both, respectively). Among the hemodynamic variables measured during standardized submaximum exercise (30 Watts), MRT was most closely associated with mean pulmonary arterial pressure (mPAP, Figure, bottom panel), and was also associated with right atrial pressure (R=0.46, P=0.02) and pulmonary capillary wedge pressure (R=0.61, P=0.001). In multivariate regression adjusting for age, gender and resting LVEF, MRT remained inversely associated with resting RVEF (β= -0.93, P=0.024) and directly associated with mPAP at 30W (β=2.08, P<0.001).
Conclusion In patients with HFrEF, VO2 kinetics during submaximal exercise are closely related to RV-pulmonary vascular unit function and likely reflect impaired pulmonary perfusion. Given the challenges with assessing RV-PV performance during exercise, O2 kinetics may represent and important surrogate for RV-PV unit function during exercise.
- © 2011 by American Heart Association, Inc.