Studies on acute atrial fibrillation. Epidemiology and clinical effects of digoxin

Abstract

Background: Acute atrial fibrillation is a common cardiac disorder but data on epidemiology and treatment routines are sparse. Treatment routines generally aim to decrease heart rate, to achieve conversion to sinus rhythm and to improve haemodynamics and decrease ischemia. Digoxin is acommon treatment choice but data on its clinical effects are largely missing.Patients and methods: The incidence and treatment routines of acute atrial fibrillation in Gothenburg were studied by retrospective chart review. The effects of i.v digoxin on conversion to sinus rhythm, heart rate, and the ECG changes and the relation between pharmacokinetics and pharmacodynamics were studied in a placebo controlled and randomised multicentre study. Predictors of conversion to sinus rhythm were analysed based on data from the epidemiological study and, since atrial pressures during arrhythmia may predict conversion, theplasma level N-terminal proANF at baseline.Results: 234 consecutive patients were included in the epidemiological and 239 patients in the clinical study.Approximately 85 % of the patients seeked medical attention within 48 hours of arrhythmia onset. The incidenceof acute atrial fibrillation was approximately 0.7 cases/ 100,000inhabitants per year. Twenty-four hours after inclusion 79 % of the patients had converted to sinus rhythm in the epidemiological study, about half of these were spontaneous. In the clinical study the conversion rate was 49 % in the placebo group and 51 % in thedigoxin group (n.s, R.R.: 1.14, 95 % C.I. for RR: 0.87-1.48). Heart rate was effectively lowered by digoxin in patients remaining in atrial fibrillation, and a linear relation between the estimated concentration of digoxin at the effect site and the decrease in heart rate was found. Digoxin induced a significant decrease in theST segment, the T wave amplitude and QTc interval early afteradministration. In regression analyses short arrhythmia duration predicted conversion to sinus rhythm, while plasma levels of N-terminal proANF at baseline did not.Conclusion: Acute atrial fibrillation is common, and the probability of spontaneous conversion to sinus rhythmwithin 24 hours is high. Digoxin did not increase the rate of conversion but lowered heart rate, proportionally toheart rate at inclusion, and induced changes in the ECG early after i.v administration. Arrhythmia duration predicted probability of conversion to sinus rhythm, while plasma levels of N-terminal proANF at baseline did not.