USEFULNESS OF HEART-RATE-VARIABILITY IN PREDICTING DRUG EFFICACY (METOPROLOL VS DILTIAZEM) IN PATIENTS WITH STABLE ANGINA-PECTORIS

We investigated whether analysis of heart rate (HR) variability may be used to predict the efficacy of drug treatment of myocardial ischemia . In a double-blind, crossover study, 28 patients with stable angina p ectoris, proven coronary artery disease, and myocardial ischemia durin g Holter monitoring received metoprolol controlled-release 200 mg once daily and diltiazem 60 mg 4 times daily. After a placebo run-in phase and after each treatment period, 72-hour Holter recordings were obtai ned for HR variability and ST-segment analysis. At baseline, the total duration of myocardial ischemia was 11.4 +/- 13.9 minutes (mean +/- S D per 24 hours), and the total number of episodes was 2.2 +/- 2.3. Met oprolol significantly reduced the total duration of ischemia by -8.7 m inutes (95% CI -14.5 to -2.8) and the total number of episodes by -1.9 (-2.9 to -0.8) in patients with a low SD of normal-to-normal interval s at baseline (SDNN), using the median value of 50 ms as a cut-off val ue. In contrast, significant treatment effects were not observed in pa tients with a high SDNN at baseline. Similar results were obtained usi ng baseline total power or low-frequency power, but not when using bas eline heart rate. Diltiazem reduced the total duration of ischemia by -4.9 minutes (-9.7 to -0.1), but not the number of episodes. Moreover, in contrast to metoprolol, efficacy of diltiazem was not related to b aseline HR variability. In conclusion, patients with reduced HR variab ility at baseline responded to treatment with metoprolol. This differe ntial pattern was not observed with diltiazem. Our results, therefore, suggest that analysis of HR variability may be useful in selecting pa tients who will benefit from treatment with beta blockers.