Background - In patients with chronic heart failure (CHF) and preserved exercise tolerance, the value of cardiopulmonary exercise testing for risk stratification is not known. Elevated slope of ventilatory response to exercise (V̇E/V̇CO2) predicts poor prognosis in advanced CHF. Derangement of cardiopulmonary reflexes may trigger exercise hyperpnea. We assessed the relationship between cardiopulmonary reflexes and V̇E/V̇CO2 and investigated the prognostic value of V̇E/V̇CO2 in CHF patients with preserved exercise tolerance. Methods and Results - Among 344 consecutive CHF patients, we identified 123 with preserved exercise capacity, defined as a peak oxygen consumption (peak V̇O2) ≥18 mL · kg-1 · min-1 (age 56 years; left ventricular ejection fraction 28%; peak V̇O2 23.5 mL · kg-1 · min-1). Hypoxic and hypercapnic chemosensitivity (n=38), heart rate variability (n=34), baroreflex sensitivity (n=20), and ergoreflex activity (n=20) were also assessed. We identified 40 patients (33%) with high V̇E/V̇CO2 (ie, >34.0). During follow-up (49±22 months, >3 years in all survivors), 34 patients died (3-year survival 81%). High V̇E/V̇CO2 (hazard ratio 4.3, P<0.0001) but not peak V̇O2 (P=0.7) predicted mortality. In patients with high V̇E/V̇CO2, 3-year survival was 57%, compared with 93% in patients with normal V̇E/V̇CO2 (P<0.0001). Patients with high V̇E/V̇CO2 demonstrated impaired reflex control, as evidenced by augmented peripheral (P=0.01) and central (P=0.0006) chemosensitivity, depressed low-frequency component of heart rate variability (P<0.0001) and baroreflex sensitivity (P=0.03), and overactive ergoreceptors (P=0.003) compared with patients with normal V̇E/V̇CO2. Conclusions - In CHF patients with preserved exercise capacity, enhanced ventilatory response to exercise is a simple marker of a widespread derangement of cardiovascular reflex control; it predicts poor prognosis, which peak V̇O2 does not.
- Heart failure