Chemoreflex and Baroreflex Sensitivity Hold a Strong Prognostic Value in Chronic Heart Failure

Abstract

Background: Novel treatments targeting in baroreflex sensitivity (BRS) and chemoreflex sensitivity (CRS) heart failure (HF) are grounded on small prognostic studies, partly performed in the pre-beta-blockade era.

Objectives: This study assesses the clinical/prognostic significance of BRS and CRS in a large cohort of patients with chronic HF on modern treatments.

Methods: Outpatients with chronic HF with either reduced (≤40%) or mildly reduced left ventricular ejection fraction (LVEF) (41% to 49%) underwent BRS (SD method) and CRS to hypoxia and hypercapnia (rebreathing technique) assessment and were followed up for a composite endpoint of cardiac death, implantable cardioverter-defibrillator shock, or HF hospitalization.

Results: A total of 425 patients were enrolled (65 ± 12 years of age, LVEF 32% [IQR: 25%-38%], 94% on beta blockers). Patients with decreased BRS (n = 96 of 267, 36%) had lower exercise tolerance and heart rate variability (P < 0.05), whereas those with increased CRS to both hypoxia and hypercapnia (n = 74 of 369, 20%) had higher plasma norepinephrine and central apneas across the 24-hour period (P < 0.01). During a median 50-month follow-up (IQR: 24-94 months), the primary endpoint occurred more often in patients with decreased BRS (log-rank: 11.64; P = 0.001), mainly for increased cardiac deaths/implantable cardioverter-defibrillator shocks, and in those with increased CRS (log-rank: 34.81; P < 0.001), mainly for increased HF hospitalizations. Patients with both abnormal BRS and CRS showed the worst outcome. Reduced BRS (HR: 2.76 [95% CI: 1.36-5.63]; P = 0.005) and increased CRS (HR: 2.91 [95% CI: 1.34-6.31]; P = 0.007) were independently associated with the primary outcome and increased risk stratification when added to standard HF prognosticators (P < 0.05).

Conclusions: In subjects with HF on modern treatment, abnormal BRS and CRS are frequently observed. BRS and CRS elicit autonomic imbalance, exercise limitation, unstable ventilation, and predict adverse outcomes.

Keywords: autonomic nervous system; baroreflex; chemoreflex; heart failure; hospitalization; mortality.