EFFICACY OF ANTICOAGULANT THERAPY IN PREVENTING EMBOLISM RELATED TO DC ELECTRICAL CONVERSION OF ATRIAL FIBRILLATION

Among 437 patients in whom electrical conversion of atrial arrhythmia was attempted 228 were on long-term anticoagulant therapy and 209 were not given anticoagulants. Thirteen (3 per cent) had an embolic episode, 2 of the 186 patients in the anticoagulant group and 11 of the 162 patients in the comparative group whose arrhythmias were converted. This difference is statistically significant at the 5 per cent level (p = 0.012). Three of 11 patients with a history of embolic episodes, whose arrhythmia was converted without anticoagulants, had a new episode after conversion, compared to none of the 55 patients with previous episodes who were receiving anticoagulant therapy. We attach importance to the significant difference in embolic episodes between the two groups even if the patients were not allocated at random, perhaps even greater importance, because the difference in composition of the two groups produced a bias against the anticoagulant group. For example, patients with a history of previous embolic episodes and those with rheumatic valvular disease were considerably over-represented in this group. In both of these categories an increased risk of embolism is present. Our results lead to the conclusion that prophylactic anticoagulant therapy is clearly indicated before and after attempts to convert atrial fibrillation in patients with a history of previous embolic episodes. In our opinion such prophylaxis should preferably be given in connection with attempts at conversion in all cases. © 1969.