Preexisting atrial fibrillation and myocardial infarction: only 10% of infarcts directly linked to atrial fibrillation.

The aim of the study was to evaluate the incidence and prognosis of type 1 myocardial infarction (T1MI) and type 2 MI (T2MI) in patients with acute MI and known atrial fibrillation (AF) to identify MI directly linked to AF. Among the 669 patients, four patients with hyperthyroidism were excluded, and among the remaining 665 patients, about two-thirds were diagnosed with T1MI, and the remaining third were diagnosed with T2MI. AF was the direct cause of MI in 9.8% of our overall population [1.8% of T1MI type C (coronary embolism), 4.9% of T2MI type A and 3.1% of T2MI type B]. Among patients with T2MI, 30-day mortality was lower when the trigger was AF than for the other triggers, for both type 2A (6% vs. 11%) and type 2B (0% vs. 13%). Most cases of AF-related MI are, thus, T2MI, for which therapeutic guidelines are lacking. Given the diverse triggers in T2MI, a specific approach using etiological patterns is needed to properly determine the optimal therapeutic.