Usefulness of a multiparametric evaluation including global longitudinal strain for an early diagnosis of acute myocarditis.

Cardiac magnetic resonance imaging (CMRI) represents the main imaging modality for diagnosing acute myocarditis. However, its limited availability could entail missing or delayed diagnosis. A reduction of left ventricular global longitudinal strain (LV GLS) by speckle tracking echocardiography (STE) correlates with amount of oedema in acute myocarditis and here may be early detected. Aim was to evaluate the diagnostic and prognostic role of 3-layers LV GLS in patients with acute myocarditis. Out of 122 patients with suspected acute myocarditis, a total of 86 consecutive patients with CMRI-confirmed acute myocarditis admitted in two Italian institutions were retrospectively screened. Exclusion criteria were met in 29 patients because of poor acoustic window or missing data. A total of 57 patients were then included. Clinical characteristics, laboratory examinations, transthoracic echocardiography data and STE parameters were collected early after hospitalization. In the study population, mean age was 38.8 ± 15.6 years, the prevalence of male gender was 90%. On admission, 22 patients (39%) had fever (body temperature > 37.5 °), mean white blood cell (WBC) count was 10.9 ± 1.7/10^3 and overall LV ejection fraction was 50.1% ± 11.2. An epicardial LV GLS < 18% was present in 74% of patients, and a model including at least one of LV GLS < 18% (absolute value), fever and WBC > 10.0/10^3 was able to identify all patients with CMRI-diagnosed acute myocarditis. An epicardial LV GLS < 15.3% (absolute value) at baseline significantly predicted the lack of myocarditis resolution during follow-up (AUC 0.76, 95% CI 0.58-0.93, p = 0.02). A multiparametric model including epicardial LV GLS, fever and elevated WBC count on admission could be useful for early diagnosing an acute myocarditis, especially when CMRI is not promptly available. Baseline epicardial LV GLS may also identify patients with less-likely myocarditis resolution.