EFFECTS OF BETA-RECEPTOR-ANTAGONISTS IN PATIENTS WITH CLINICAL-EVIDENCE OF HEART-FAILURE AFTER MYOCARDIAL-INFARCTION - DOUBLE-BLIND COMPARISON OF METOPROLOL AND XAMOTEROL

Objective-To evaluate whether xamoterol, a partial agonist, would impr ove exercise time more than metoprolol in patients with mild to modera te heart failure after a myocardial infarction. Design-Single-centre d ouble blind randomised parallel group comparison of metoprolol 50-100 mg and xamoterol 100-200 mg twice daily. Patients-210 patients aged 40 -80 years (173 men) with clinical evidence of heart failure early afte r a myocardial infarction. 106 were given metoprolol and 104 xamoterol . Main outcome measures-Exercise test results and performance at three months; the exercise test, quality of life, and clinical assessments at baseline (5-7 days after the infarction) and after 3, 6, and 12 mon ths. Results-Exercise time increased at three months by 22% in the met oprolol group and 29% in the xamoterol group, but with no significant difference between the groups. Patients taking xamoterol showed overal l non-significantly higher mean values of exercise time achieved with higher heart rates at rest and exercise. Improvements in quality of li fe, clinical signs of heart failure, and New York Heart Association fu nctional class were seen in both treatment groups over one year, with minor benefits of xamoterol on breathlessness, peripheral oedema, and functional class. Eighteen patients taking metoprolol and 22 taking xa moterol withdrew from the study during one year, with a low mortality, reinfarction rate, and progress of heart failure in both treatment gr oups. Mean dose from baseline to 3 months was 135 mg metoprolol and 34 7 mg xamoterol. Conclusion-beta(1) Receptor antagonists with or withou t partial agonist activity are safe to use in mild to moderate heart f ailure after a myocardial infarction. Exercise tolerance, quality of l ife, and clinical signs and functional class of heart failure improve, and few patients show deterioration in their condition. Exercise tole rance is no better with xamoterol than metoprolol.