Central Cardiac Limit to Aerobic Capacity in Patients With Exertional Pulmonary Venous Hypertension

Abstract

Background— The mechanism of functional limitation in heart failure with preserved ejection fraction remains controversial. We examined the contributions of central cardiac and peripheral mechanisms and hypothesized that the pulmonary vascular response to exercise is an important determinant of aerobic capacity among patients with exertional pulmonary venous hypertension (ePVH). Methods and Results— We compared 31 ePVH patients (peak V O 2 <80% of predicted and peak pulmonary arterial wedge pressure≥20 mm Hg) with 31 age- and sex-matched controls (peak V O 2 >80% predicted) who underwent invasive cardiopulmonary exercise testing for unexplained exertional intolerance. ePVH patients had lower peak cardiac output (73±14% versus 103±18% predicted; P <0.001) compared with controls, related both to impaired chronotropic response (peak heart rate 111±25 beats per minute versus 136±24 beats per minute; P <0.001) and to reduced peak stroke volume index (47±10 mL/min per m 2 versus 54±15 mL/min per m 2 ; P =0.03). Peak systemic O 2 extraction was not different between groups (arterial-mixed venous oxygen content difference: 13.0±2.1 mL/dL versus 13.4±2.4 mL/dL; P =0.46). ePVH patients had higher resting (150±74 versus 106±50 dyne/s per cm −5 ; P =0.009), peak (124±74 dyne/s per cm −5 versus 70±41 dyne/s per cm −5 ; P <0.001), and isoflow pulmonary vascular resistance (124±74 dyne/s per cm −5 versus 91±33 dyne/s per cm −5 at cardiac output≈10.6 L/min; P =0.04). Pulmonary vascular resistance decreased with exercise in all control subjects but increased in 36% (n=11) of ePVH patients. Abnormal pulmonary vascular response was not associated with peak V O 2 . Conclusions— Reduced cardiac output response, rather than impaired peripheral O 2 extraction, constrains oxygen delivery and aerobic capacity in ePVH. Pulmonary vascular dysfunction is common in patients with ePVH at rest and during exercise.