Acute myocarditis with autoimmune features: one-year follow-up with CMR

In this prospective study on patients with acute myocarditis (AM), we aimed to describe the new concept of AMAF (AM with autoimmune features) similar to the previously described interstitial pneumonia with autoimmune features (IPAF). IPAF has recently emerged as a new entity, and IPAF patients appear to have fewer episodes of exacerbation and better survival than patients with idiopathic pulmonary fibrosis. Consecutive patients with infarct-like CMR-confirmed AM were classified AMAF if their serologic status measured from blood sampled at presentation was positive (antinuclear antibodies (ANA) ≥ 1:320), but without meeting established classification criteria for connective tissue disease (CTD). The myocardial tissue abnormalities and their progression were assessed on cardiac magnetic resonance (CMR) within 7 days following symptom onset and at 1 year according to their seropositivity. Among the 64 AM patients included, seven presented AMAF (11%). At baseline CMR, patients with AMAF had half as much late gadolinium enhancement (LGE) as seronegative AM patients (4.41% (1.47-4.41) of myocardial volume versus 8.82% (5.88-14.71), p = 0.01, respectively). At 1-year of follow-up, persistent myocardial scarring was less frequent in AMAF patients (n = 2 (28.6%) than seronegative AM patients (n = 38 (66.7%) (p = 0.021). AMAF, diagnosed as seropositive AM without a specific autoimmune disease, is not rare and is associated with less extensive LGE in the acute phase. In addition, AMAF patients had more favorable outcomes on 12-month CMR. Prospective studies are needed to address the clinical significance of this new concept and its long-term cardiovascular impact.