Does the initial electrocardiogram identify a distinct phenotype in acute myocarditis?
J Conde Goncalves, L Alves, B Viana, T Branco, E Figueiredo, B Cruz, E Oliveira, M Paiva, M VasconcelosAbstract
Background
The clinical relevance of the initial electrocardiogram (ECG) in acute myocarditis remains incompletely defined. Whether ECG abnormalities reflect a distinct phenotype with more extensive myocardial injury is still uncertain.
Purpose
To compare clinical characteristics, laboratory findings, cardiac magnetic resonance features and outcomes in patients with acute myocarditis according to the presence or absence of electrocardiographic abnormalities at presentation.
Methods
We conducted a retrospective observational study including patients diagnosed with acute myocarditis. Patients were stratified according to the initial electrocardiogram into normal versus abnormal electrocardiogram (including ST-segment elevation, ST-segment depression or other repolarization abnormalities). Continuous variables were compared using the Mann–Whitney U test and categorical variables using chi-square or Fisher’s exact test, as appropriate.
Results
A total of 138 patients were included, of whom 84 (60.9%) presented with electrocardiographic abnormalities. Patients with abnormal electrocardiogram were more frequently male (89.3% vs 68.5%, p=0.002), while age did not differ between groups (p=0.787). Troponin levels were significantly higher in patients with electrocardiographic abnormalities (p<0.001), whereas inflammatory markers (p=0.633) and natriuretic peptides (p=0.888) were similar between groups. On admission cardiac magnetic resonance, myocardial edema (p=0.002) and late gadolinium enhancement (p=0.008) were more frequently observed in patients with abnormal electrocardiogram. Left ventricular ejection fraction was typically preserved and did not differ between groups (p=0.790). Patients with electrocardiographic abnormalities more frequently received anti-inflammatory therapy, including non-steroidal anti-inflammatory drugs (75.0% vs 51.9%, p=0.005) and colchicine (67.9% vs 46.3%, p=0.012). During follow-up, no significant differences were observed regarding persistence of myocardial edema (p=0.655), persistence of late gadolinium enhancement (p=0.083), recurrence of myocarditis (p=0.372) or cardiovascular-related hospitalizations (p=0.419).
Conclusions
In this cohort of patients with acute myocarditis, the presence of ECG abnormalities at presentation identified a phenotype associated with higher myocardial injury, reflected by increased troponin release and a higher prevalence of edema and late gadolinium enhancement on CMR. However, these differences were not associated with impaired ventricular function or worse clinical outcomes during follow-up, supporting the overall favorable prognosis of this condition despite more extensive initial myocardial involvement.