Does atrial fibrillation beget ventricular fibrillation in patients with acute myocardial infarction?

Atrial fibrillation (AF) is associated with increased mortality and a higher complication rate postmyocardial infarction (MI), but the exact mechanisms are unknown. We investigated whether AF predisposes to ventricular arrhythmia in postmyocardial infarct patients, thereby accounting for increased mortality.

Five hundred consecutive patients admitted to our coronary care unit with acute MI were monitored for in-hospital arrhythmias. Detailed information was also compiled on past history, co-morbidities, electrolyte disturbances, drug therapies, and ejection fraction. Mortality data were collected for an average of 5.5 years.

The results have shown that the incidence of ventricular fibrillation (VF) is much greater in patients presenting with AF (P=0.03) and multivariate analysis has shown that AF is independently associated with the development of VF. This association occurs principally in patients who are admitted with AF (P=0.01) rather than those who develop it during their admission, although these patients are also at mildly increased risk. The increased incidence of VF does account for increased mortality in the AF patients but does not explain all of their excess risk. There was no association between AF and ventricular tachycardia (VT); P=0.50.

In conclusion, AF on admission to the hospital with acute MI is associated with an increased risk of VF and subsequent mortality.