Clinical features, myocardial injury and systolic impairment in acute myocarditis.

Objective: Cardiovascular magnetic resonance (CMR) is increasingly used in the diagnosis of myocarditis, with myocardial injury and systolic dysfunction playing key roles in the prognosis of this clinical setting. The clinical determinants of myocardial injury and systolic impairment in acute myocarditis are poorly defined. The aim of the current study is to assess the association of laboratory markers, late gadolinium enhancement (LGE) and left ventricular ejection fraction (LVEF) in patients with acute myocarditis.

Methods: We completed a retrospective cohort study from a tertiary referral centre in London with CMR and acute myocarditis. Cases with cardiomyopathy were excluded. Missing data was imputed for selected clinical variables. We evaluated the association between peak troponin and LGE extent and LVEF. We adjusted the models for age, sex and time to CMR with a sensitivity analysis adjusting for body mass index and cardiovascular risk factors including hypertension, dyslipidaemia, diabetes mellitus and smoking.

Results: 127 patients had abnormal T2-weighted imaging/mapping results with 118 (93%) presenting with chest pain and/or shortness of breath. Left ventricular LGE was identified in 118 (93%) patients and LVEF was 58±11%. The median time from the peak troponin to CMR was 1 day (IQR 0-6 days). The highest tertile of peak troponin was associated with more LGE (incident rate ratio 1.33, 95% CI: 1.07 to 1.64) and a lower LVEF (coefficient -5.3%, 95% CI: -9.5% to -1.1%). Diabetes was also associated with more LGE (incident rate ratio 1.90, 95% CI: 1.37 to 2.61) and lower LVEF (coefficient -8.9%, 95% CI: -14.7% to -1.8%).

Conclusions: Peak troponin is associated with more LGE and a lower LVEF even after accounting for demographics and comorbidities. Myocardial injury and systolic dysfunction play key roles in prognosis and future work incorporating clinical features into a risk prediction model may enable better risk stratification in acute myocarditis.