ELECTROPHYSIOLOGIC EFFECTS OF AMLODIPINE VS. DILTIAZEM IN PATIENTS WITH CORONARY-ARTERY DISEASE AND BETA-BLOCKING THERAPY

This study compares the electrophysiologic effects of amlodipine and d iltiazem in patients with coronary artery disease concomitantly treate d with background beta-blocking therapy. Thirty patients were included in an open-label parallel study in two phases. During phase 1, patien ts were screened and placed on maintenance atenolol therapy at 50 or 1 00 mg/day, while phase 2 consisted of right-sided catheterization and randomization of patients to either amlodipine (10 mg IV) or diltiazem (10 mg IV), Following treatment with amlodipine, no significant alter ation in markers of electrophysiological activity was observed. Treatm ent with diltiazem resulted in a significant lengthening of sinus cycl e length (SCL, p < 0.04), AH interval(p < 0.02), and Wenckebach CL (WC L, p < 0.001), and a trend towards an increase in sinus node recovery time (SNRT, p = 0.057). No effects were observed with regard to HV int erval and corrected SNRT. The results of this study indicate that 10 m g intravenous amlodipine has no significant electrophysiological actio n on sinus or AV node function in patients receiving betablocker thera py with atenolol, suggesting that amlodipine can be added to beta-bloc kers to treat patients with myocardial ischemia and/or hypertension wi thout any significant increase in the risk of bradyarrhythmias.