Abstract 14309: Beta Blocker Cessation Does Not Restore Chronotropic Response in Patients With Advanced Heart Failure
Background: Chronotropic incompetence (CI) is defined as inability to reach 80% of maximally predicted heart rate (MPHR) or 80% of HR reserve (% HRR = [Peak - Resting HR / Achieved Peak HR - Resting HR] × 100) during exercise. Rate responsive pacing therapy for CI is under investigation to improve exercise capacity in heart failure (HF), but uncertainty persists as to whether CI in HF is due to Beta (β)-blockade.
Methods: Nineteen patients with systolic CHF (LVEF 23+/- 8%) on β-blocker therapy > 3 months underwent cardiopulmonary exercise tolerance testing (CPETT) under 2 conditions in random sequence: (1) 3 hours after β-blocker ingestion [On BB] and (2) after a 27 hour ‘washout’ period [Off BB]. Norepinephrine (NE) levels were drawn at rest and at peak exercise. β1-response to NE was calculated via the chronotropic responsiveness index (CRI)=change in HR per unit of NE: (Peak -Baseline HR)/ (log[Peak-Baseline NE]).
Results: Mean age was 49.4+/-12.3. Average Carvedilol equivalent dose was ∼30mg daily. Peak HR on/off β-blockers was 79.1+/-11.0% and 70.3+/-12.3% of the MPHR (p=0.02). HRR was 58.0+/-17% on and 61.7+/-18% off BB (p=0.49). For the Off and On-BB conditions, the Respiratory Exchange Ratio was 1.05+/-0.06 and 1.05+/-0.10 (p=1.00), confirming maximal effort in both conditions, the pVO2 was 16.6+/-3.34 and 15.9+/-3.31 (p=0.52), and the CRI was 19.7+/-1.48 and 18.1+/-1.90 (p=0.79).
Conclusion: Acute β-blocker cessation does not restore chronotropic response in advanced HF nor alter the HR response to endogenous NE. β-blockers should be continued in patients with HF in whom rate-responsive pacing is contemplated, as they are not the underlying cause of CI and prolong survival.
- © 2011 by American Heart Association, Inc.