UNSTABLE ANGINA - EFFECT OF BETA-BLOCKERS ATENOLOL AND METOPROLOL ON HEART-RATE-VARIABILITY

It was previously suggested that lipophilic beta-blockers due to their centrally-mediated action could enhance vagal activity to a greater d egree than hydrophilic ones. In order to test the hypothesis an open c omparative randomized trial was conducted on 75 patients (65 with unst able angina and 10 with non-Q-wave myocardial infarction); Shortterm ( 512 RR intervals) heart rate variability was assessed at rest in supin e position at admission and after 1 week of regular use of hydrophilic atenolol (n=40) or lipophilic metoprolol (n=35). Dose of beta-blocker s was titrated to suppress myocardial ischemia and to decrease heart r ate below 60 bpm. Dose of metoprolol was 282,1+/-136,9, of atenolol -1 48,1+/-70,3 mg/day. Administration of both beta-blockers for 1 week wa s associated with slowing of heart rate and increase of low (0,04-0,15 Hz), high (0,15-0,40 Hz), total (0,003-0,40 Hz) frequency powers, are a of scatterplots and augmentation of vagal activity (as evidenced by decreases of LF/HF ratio and low frequency power in normalized units). Thus metoprolol and atenolol exerted similar action on parameters of heart rate variability.