National cohort of suspected myocarditis PreMYO: descriptive analysis of the first 575 cases.

Background/Introduction Myocarditis is a heterogeneous condition with variable clinical presentations, ranging from nonspecific chest pain to heart failure or sudden cardiac death. The Spanish Pre-MYO cohort aims to establish a platform for the study of suspected myocarditis. Purpose/Methods The PreMYO cohort is a nationwide, prospective, observational, multicenter registry (76 hospitals across 17 regions in Spain aimed at characterizing the clinical presentation, management, and outcomes of patients with suspected acute myocarditis and inflammatory cardiomyopathy based on clinical findings. We analyzed data from the first 575 patients enrolled to date. Demographic, clinical, electrocardiographic, biochemical, and imaging variables were assessed. The diagnosis of myocarditis (confirmed, probable and discarded) was obtained through on-site adjudication based on current diagnostic criteria. Results 78.6% of patients with suspected myocarditis were male (mean age: 41.0 ± 18.8 years). The most common clinical presentation was acute chest pain (87.6%), followed by fever (34.7%), exertional dyspnea (17.6%) and asthenia (10.7%), with an acute onset in many cases. A pre-existing autoimmune disease was identified in 5.4% of cases. Troponin I/T elevation was observed in 96.3% of cases. Electrocardiographic abnormalities were present in 63.1% of patients, including T-wave inversion in 22.6%, ST-segment elevation in 48.1%, and ST-segment depression in 28.3%. Cardiac magnetic resonance imaging (CMR) was performed in 484 patients (84.2%), with 73.6% exhibiting late gadolinium enhancement and 67.1% showing signs of myocardial edema. Most patients exhibited preserved left ventricular ejection fraction (LVEF) (77.2%), although segmental contractility abnormalities were present in 27.5% of cases. Heart failure (HF) was observed in 7% of patients, cardiogenic shock in 4.2%, and ventricular dysfunction in 11.6%. The median NT-proBNP level at diagnosis was 570 pg/mL [IQR: 180-2819]. Pericardial involvement was noted in 43.1% of cases. Ventricular arrhythmias were reported in 3.9% of cases, and syncope in 3.0%. Mortality was observed in 2.4% of the cohort, with 64.3% of these cases being related to myocarditis. A confirmed diagnosis of myocarditis was obtained in 407 cases (70.8%) and, among these the most frequently suspected etiology was probable infectious (28.7%), though the cause remained unknown in 65.9%. At hospital discharge, 45.6% of patients received non-steroidal anti-inflammatory drugs (NSAIDs), 41.9% colchicine, and 8.0% corticosteroids. Conclusions Among the first 575 cases in the Pre-MYO cohort, most patients presented with an acute clinical picture and preserved LVEF, with a low prevalence of HF, cardiogenic shock, or severe arrhythmias. More than 40% exhibited pericardial involvement and, in many cases, the etiology of myocarditis remained unidentified. Approximately half of patients are discharged with NSAIDs.