Differential effects of adrenergic antagonists (Carvedilol vs Metoprolol) on parasympathetic and sympathetic activity: a comparison of clinical results
Abstract:
Overview
Background. Cardiovascular autonomic neuropathy (CAN) is recognized as a significant health risk, correlating
with risk of heart disease, silent myocardial ischemia or sudden cardiac death. Beta-blockers are often prescribed
to minimize risk.
Objectives. In this second of two articles, the effects on parasympathetic and sympathetic activity of the alpha/
beta-adrenergic blocker, Carvedilol, are compared with those of the selective beta-adrenergic blocker, Metoprolol.
Methods: Retrospective, serial autonomic nervous system test data from 147 type 2 diabetes mellitus patients
from eight ambulatory clinics were analyzed. Patients were grouped according to whether a beta-blocker was
(1) introduced, (2) discontinued or (3) continued without adjustment. Group 3 served as the control.
Results. Introducing Carvedilol or Metoprolol decreased heart rate and blood pressure, and discontinuing them
had the opposite effect. Parasympathetic activity increased with introducing Carvedilol. Sympathetic activity
increased more after discontinuing Carvedilol, suggesting better sympathetic suppression. With ongoing treatment,
resting parasympathetic activity decreased with Metoprolol but increased with Carvedilol.
Conclusion. Carvedilol has a more profound effect on sympathovagal balance than Metoprolol. While both suppress
sympathetic activity, only Carvedilol increases parasympathetic activity. Increased parasympathetic activity
may underlie the lower mortality risk with Carvedilol.
Keywords
Beta-blocker, Cardiovascular autonomic neuropathy, Heart rate variability, Patient outcomes, Respiratory analysis, Sympathovagal imbalance
Article:
Article Information:
Disclosure
Financial support: None.
Correspondence
Dr. Joe Colombo 240 South Eighth Street Philadelphia, PA, USA 19107 joe@ans-hrv.com