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

The Fourth Universal Definition of Myocardial Infarction (UDMI) classifies myocardial infarction (MI) into 5 subtypes, of which types 1 and 2 MI are the most common. Modest revision of the UDMI has been proposed recently by a group of experts to reclassify spontaneous coronary artery dissection, coronary embolism, and coronary vasospasm from T2MI to T1MI. However, prior atrial fibrillation (AF) has not been considered yet in this new classification. The aim of the present study was to evaluate the incidence and prognosis of T1MI and T2MI. Retrospective study in patients with acute MI and known AF by enrolling consecutive patients from a large cohort of acute MI patients admitted to a coronary care unit between October 2012 and February 2020. Among 669 patients with MI and previous AF, about two-thirds were diagnosed with T1MI, and the remaining third were diagnosed with T2MI (Fig. 1). AF was the direct cause of MI in 10.3% of our overall population (1.8% of T1MI type C, 5.2% of T2MI type A and 3.3% of T2MI type B). 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 response.