Effect of atenolol and diltiazem on heart period variability in normal persons

• Published in: Journal of the American College of Cardiology Vol. 17; no. 2; pp. 480 - 484
• Main Authors: Cook, James R., Thomas Bigger, J., Kleiger, Robert E., Fleiss, Joseph L., Steinman, Richard C., Rolnitzky, Linda M.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01-02-1991; Elsevier Science
• Subjects: Adult; Antianginal agents. Coronary vasodilator agents; Atenolol - pharmacology; Biological and medical sciences; Cardiovascular system; Diltiazem - pharmacology; Electrocardiography, Ambulatory; Female; Heart - drug effects; Heart - innervation; Humans; Male; Medical sciences; Myocardial Contraction - drug effects; Myocardial Infarction - drug therapy; Parasympathetic Nervous System - drug effects; Pharmacology. Drug treatments; Sympathetic Nervous System - drug effects; Human; Electrocardiography; Cardiac cycle; Calcium antagonist; Beta blocking agent
• ISSN: 0735-1097; 1558-3597
• DOI: 10.1016/S0735-1097(10)80119-6

Several time and frequency domain measures of heart period variability are reduced 1 to 2 weeks after myocardial infarction, and a reduced standard deviation of normal RR intervals over a 24 h period (SDNN) is associated with increased mortality. The predictive accuracy of heart period variability may be reduced by drugs used to treat patients after myocardial infarction. Accordingly, a randomized, three period, placebo-controlled, crossover (Latin square) design was used to determine the effect of atenolol and diltiazem on time and frequency measures of heart period variability calculated from 24 h continuous electrocardiographic recordings during treatment with atenolol, diltiazem and placebo in 18 normal volunteers.
During atenolol treatment, the 24 h average normal RR (NN) interval increased 24% (p < 0.001). The three measures of tonic vagal activity were significantly increased (p < 0.001) during atenolol treatment: percent of successive normal RR intervals >50 ms = 69%, root mean square successive difference of normal RR intervals = 61% and high frequency power in the heart period power spectrum = 84%. Low frequency power also increased 45% (p < 0.01), indicating that this variable also is an indicator of tonic vagal activity over 24 h. Diltiazem had no significant effect on the 24 h average NN interval or on any measure of heart period variability.
The decreased mortality rate after myocardial infarction associated with beta-adrenergic blocker but not calcium channel blocker therapy may be attributed in part to an increase in vagal tone caused by beta-blockers.