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  • Title: Effect of beta adrenergic receptor blockade on cardiac autonomic tone in patients with chronic stable angina.
    Author: Burger AJ, Kamalesh M, Kumar S, Nesto R.
    Journal: Pacing Clin Electrophysiol; 1996 Apr; 19(4 Pt 1):411-7. PubMed ID: 8848388.
    Abstract:
    Decreased heart rate variability, which may be due to increased sympathetic and decreased parasympathetic activity, has been shown to be predictor of cardiac events after acute myocardial infarction. The present study was undertaken to analyze the effect of beta adrenergic blockade on cardiac autonomic system in patients with chronic stable angina. Nineteen patients (15 males and 4 females, age range 44-74 years) with chronic stable angina were enrolled. After stopping all cardiac medications, patients had two baseline treadmill tests with both reproducible angina and ST depression and a baseline 48-hour ambulatory ECG recording. A long-acting beta-blocker (atenolol or betaxolol) was started and titrated to the maximal tolerated dose. After 1-2 months, a repeat 48-hour ambulatory ECG recording on beta-blocker therapy was obtained. Heart rate variability analysis was performed on the baseline and drug therapy ECG recordings. The average heart rate significantly decreased (P < 0.008), and the mean RR interval significantly increased (P < 0.0001). In the time-domain analysis, the standard deviation, variance, ASDNN5, and SDANN5 were not significantly affected, although the PNN50 increased. In the frequency domain, the total power (P < 0.0001) and the low frequency (P < 0.001) components decreased, while the high frequency spectrum was unchanged. Thus, sympathetic activity significantly declined in patients with chronic stable angina on beta-blocker therapy, while parasympathetic tone demonstrated a heterogenous response.
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