A latin american perspective on acute myocarditis: a comparative study of echocardiography and CMR

Abstract Background Endomyocardial biopsy is the gold standard for diagnosing acute myocarditis, but due to its invasiveness, cardiac magnetic resonance (CMR) is widely used for noninvasive tissue characterization. Transthoracic echocardiography (TTE) remains the first-line modality, although its diagnostic performance compared to CMR is not fully established. Few studies include Latin American populations. Purpose To describe the clinical and imaging features of acute myocarditis in a Latin American cohort and assess the diagnostic performance of conventional TTE versus CMR. Methods We retrospectively studied patients ≥18 years with CMR-confirmed acute myocarditis, defined by myocardial edema with or without mid-wall or subepicardial late gadolinium enhancement (LGE). Demographics, clinical presentation, and imaging findings were analyzed. Segmental agreement between TTE and CMR abnormalities was assessed using kappa statistics. Sensitivity, specificity, and chi-square tests were calculated globally and by segment. Significance was set at p < 0.05. Results Among 144 patients (71.5% male; mean age 40.2 ± 14.8 years), prodromal symptoms occurred in 54.2%, mainly fever (27.1%), diarrhea (23.6%), cough (19.4%), and myalgias (18.8%). Chest pain (86.8%), dyspnea (41.0%), and pleuritic pain (38.9%) were the most frequent symptoms at presentation. Presumed etiologies were viral (47.9%), bacterial (4.2%)—notably Streptococcus and Salmonella bacteremia—autoimmune (2.8%), and Chagas disease (1.4%). No cause was identified in 43.1%. Leukocytosis predicted reduced left ventricular ejection fraction (LVEF ≤50%). On TTE, mean LVEF was 51.6 ± 9.6%; 38.9% had reduced function (LVEF ≤50%). Wall motion was normal in 52.8%, and abnormal (global or segmental) in 47.2%. On CMR, 91.7% showed both edema and LGE, with an average of 3.6 ± 2.8 segments affected. Edema alone was present in 8.3%. The inferolateral (61.1%), anterolateral (47.2%), and inferior walls (42.4%) were the most frequently involved. TTE showed limited accuracy for detecting tissue alterations by CMR: sensitivity and specificity were 46.2% and 41.7% for LGE, and 47.1% and 50.0% for edema, respectively. Overall mortality was 2.1%. Mean hospital stay was 4.3 ± 4.8 days. Follow-up TTE showed recovery in most patients (mean LVEF 57.3%). Conclusion In this Latin American cohort, clinical and imaging patterns of acute myocarditis mirrored global trends. CMR commonly showed lateral wall involvement. While TTE demonstrated limited sensitivity for tissue characterization, it remains valuable for initial assessment. Chagas disease, though infrequent, should be considered in endemic regions like Colombia.