A cardiac MRI (CMR) is worth a thousand labs. Or, that appears to be the case in myocarditis. Dr. Heidecker et al demonstrated that late gadolinium enhancement (LGE) on CMR is unrelated to cardiac enzymes and inflammatory markers, and more prognostic in myocarditis.
Twenty-four patients were prospectively enrolled (75% male, median age 32, 13% w/ concomitant CAD) at the University of Zurich after being diagnosed with myocarditis. Myocarditis diagnosis was based on clinical features, symptom onset < 10 days, ECG, and elevated high-sensitivity troponin T in the absence of acute obstructive coronary disease.
CMR, high-sensitivity troponin T, creatine kinase (CK), myoglobin, NT-proBNP, and C-Reactive Protein were obtained at presentation and at 3 months follow-up. At 3 months, patients also underwent 48 hour holter monitoring, exercise testing (21/24 patients), and repeat ECG. The patients were monitored for adverse cardiac events (arrhythmias, severe chest pain, or dyspnea) for up to 6 months.
LGE extent (measured as a percentage of LV volume) decreased greater than 20% in 12 (50%), completely resolved in 4 (17%), did not change in 3 (12.5%), and increased greater than 20% in 5 (21%).
Of the 5 patients with an increase in LGE extent, one experienced polymorphic ventricular tachycardia requiring ICD placement. This compares to a larger study that demonstrated 17% of myocarditis patients with LGE at diagnosis experienced an SCD event.
Only CK and myoglobin were related to LGE extent at 3 months, but did not reach statistical significance (P=0.06). Among 21 (88%) patients with normalized serum markers at 3 months, 7 (39%) had resolution of LGE. Male patients were more likely to have a reduction in LGE at 3 month follow-up.
No study is perfect. The limitations include: small, single-center sample size, no patients with prior ICD implantation due to MRI constraints (increasing mean LVEF of included patients), relatively short follow-up period (6 months), and no confirmatory endomyocardial biopsy.
In a heartbeat…
In myocarditis patients with persistent or worsening LGE on CMR may predict arrhythmia better than lab values.