Abstract 2185: Ventilatory Efficiency Correlates with Exercise Pulmonary Hemodynamics in Chronic Heart Failure due to LV Systolic Dysfunction
Introduction: Ventilatory efficiency (VE/VCO2) is a prognostic marker in heart failure (HF). The relationship between VE/VCO2 and cardiovascular function in systolic HF remains unclear. We used cardiopulmonary exercise testing with continuous hemodynamic monitoring to clarify the relationship between VE/VCO2 and rest and exercise hemodynamics in patients with HF due to LV systolic dysfunction.
Methods: Breath-by-breath ventilation, pulmonary gas exchange, and right heart hemodynamics were measured during incremental cycle ergometry in 15 subjects (62±11 years old, 14 male, 53% ischemic HF, LVEF 0.28±0.05) with NYHA class II-IV HF at baseline and after 12 weeks. Ventilatory efficiency was determined by linear regression of VE versus VCO2 throughout exercise with R2>0.95 in all cases. Pearson correlation and paired Student’s t-test (for baseline versus 12 week testing) were used for analysis.
Results: Baseline VE/VCO2 was 40.6±10.5. Higher VE/VCO2 (reduced ventilatory efficiency) trended with higher resting mean pulmonary arterial (PA) pressure (r=0.49, p=0.06) and had a positive correlation with exercise PA pressure (r=0.57, p=0.03). Although pulmonary vascular resistance (PVR) at rest was not significantly related to VE/VCO2 (r=0.30, p=0.28), exercise PVR correlated with VE/VCO2 (r=0.62, p=0.01). There was no significant correlation between VE/VCO2 and rest (r=0.29) or exercise (r=0.27) pulmonary capillary wedge pressure; rest (r=−0.15) or exercise (r=−0.27) cardiac index; and rest (r=−0.17) or exercise (r=0.05) right atrial pressure. At 12 weeks, repeat exercise testing revealed no significant change in VE/VCO2 relative to baseline (41.4±15.4, p=0.70) or in any other measured hemodynamic parameters at rest or exercise.
Conclusions: VE/VCO2 can be measured reproducibly in HF patients with LV systolic dysfunction. Impaired ventilatory efficiency is associated with higher exercise PA pressure and PVR, and is not related to rest or exercise ventricular filling pressures in this small patient cohort. In systolic HF, ventilatory efficiency may be intrinsically related to dynamic changes in pulmonary vasomotor tone occurring with exercise.