Responsiveness to diving reflex after acute myocardial infarction. Influence of early beta-adrenoceptor blocker therapy.
We studied the influence of beta-adrenoceptor blockade on heart rate responses to facial immersion in ice-cooled water after acute myocardial infarction. Forty patients with acute myocardial infarction were randomized to the double-blind therapy with metoprolol 200 mg daily or matching placebo. Therapy was started as soon as possible after admission to hospital and continued for 15 days. After this initial period all patients were treated with beta-blockade during the subsequent 6 months. Repeated investigations of heart rate responses to facial immersion in ice-cooled water and 24-hour ECG-recordings were performed on day 15 (while patients were on study therapy), after 6 weeks, 3 and 6 months. Throughout the 6-month period, facial immersion elicited significant heart rate reductions in both treatment groups. No differences were found between the two groups or between different examinations during follow-up. There was no correlation between heart rate response to facial immersion and frequency of ventricular arrhythmia on a 24-hour monitoring. In conclusion, acute administration of metoprolol in myocardial infarction does not influence the bradycardial response to facial immersion either in the early postinfarction phase or during 6 months' follow-up. There is no relation between bradycardial response to face immersion and frequency of ventricular arrhythmias.
D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D000368:Aged; D002986:Clinical Trials as Topic; D003080:Cold Temperature; D004311:Double-Blind Method; D005145:Face; D005500:Follow-Up Studies; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007101:Immersion / Q000503:physiopathology*; D008297:Male; D008790:Metoprolol / Q000627:therapeutic use*; D008875:Middle Aged; D009203:Myocardial Infarction / Q000188:drug therapy / Q000503:physiopathology*; D012018:Reflex
D000319:Adrenergic beta-Antagonists; D008790:Metoprolol