Background
Exercise oscillatory ventilation (EOV) is a non-invasive parameter that potently predicts outcomes in systolic heart failure (HF). However, mechanistic insights into EOV have been limited by the absence of studies relating EOV to invasive hemodynamic measurements and blood gases performed during exercise.
Methods and Results
56 patients with systolic HF (age 59±2 years [mean±SEM], left ventricular ejection fraction 30±1%) and 19 age-matched controls were studied with incremental cardiopulmonary exercise testing. Fick cardiac outputs, filling pressures, and arterial blood gases were measured at one-minute intervals during exercise. EOV was detected in 45% of HF (HF+EOV) patients and in none of the controls. The HF+EOV group did not differ from the HF patients without EOV (HF-EOV) in age, gender, BMI, LVEF, or etiology of HF. Univariate predictors of the presence of EOV in HF, among measurements performed during exercise, included higher right atrial pressure and pulmonary capillary wedge pressure and lower cardiac index (CI), but not PaCO2 or PaO2. Multivariate logistic regression identified that low exercise CI is the strongest predictor of EOV (odds ratio 1.39, for each 1.0 L/min/m2 decrement in CI, 95% confidence interval 1.14–1.70, P=0.001). Among HF patients with EOV, exercise CI was inversely related to EOV cycle length (R=−0.71) and amplitude (R=−0.60), both P<0.001. EOV cycle length and amplitude decreased proportionate to increases in CI in 11 HF+EOV subjects treated with 12 weeks of sildenafil.
Conclusions
EOV is closely related to reduced CI and elevated filling pressures during exercise and may be an important surrogate for exercise-induced hemodynamic impairment in HF patients.
Clinical Trials Registration
ClinicalTrials.gov number NCT00309790.