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CMR With Late Gadolinium Enhancement in Acute Myocarditis
Study Questions:
What patterns of late gadolinium enhancement (LGE) are seen on cardiac magnetic resonance (CMR) in patients with acute myocarditis, and what are their prognostic implications?
Methods:
The authors analyzed patients with acute myocarditis in an Italian multicenter registry conducted in 10 hospitals. Patients with heart failure, decreased left ventricular ejection fraction (LVEF), hemodynamic instability, or arrhythmia at presentation were excluded, as were patients with obstructive coronary artery disease (CAD). 1.5 Tesla CMR was performed including T2-weighted imaging for edema and imaging for LGE. Clinical follow-up was obtained for a composite primary endpoint of cardiac death, resuscitated cardiac arrest, ventricular assist device, heart transplantation, and appropriate implantable cardioverter-defibrillator (ICD) shock. Heart failure requiring hospitalization was a secondary endpoint.
Results:
A total of 386 patients were included in this analysis (299 males [77%], mean age 35 ± 15 years). All patients had elevated troponin T and nearly all patients reported chest pain (95%) and had electrocardiographic abnormalities (96%). Fever was present in the majority (58%). Nearly all patients underwent coronary angiography (95%), all of which showed no obstructive CAD. The remaining patients were <30 years of age and had a low risk of CAD. Endomyocardial biopsy was abnormal in 18 patients (5%). Myocardial edema was identified in 94% of patients on T2-weighted CMR imaging. Several phenotypes of LGE were seen: 1) subepicardial inferior and lateral (IL) LGE (41%), 2) mid-wall basal anteroseptal (AS) LGE (36%), 3) other areas of LGE (16%), and 4) no LGE (7%). Patients with AS LGE had lower troponin and erythrocyte sedimentation rate (ESR), but higher LV and right ventricular end-diastolic volume than the other groups. Over a median follow-up of 4.3 years, eight events of the composite primary outcome occurred and 21 hospitalizations for heart failure. AS LGE had more frequent major adverse cardiac events (MACE) than IL LGE (6 vs. 0, p < 0.01) and more frequent hospitalization for heart failure (15 vs. 4, p = 0.004). For the combined endpoint of MACE and heart failure hospitalization, AS LGE was associated with an odds ratio of 2.7, p= 0.01.
Conclusions:
AS mid-wall LGE was found in approximately one third of patients with acute myocarditis and was associated with worse prognosis than other CMR patterns.
Perspective:
This study demonstrates a potential role for CMR in the management of acute myocarditis. While several studies have previously demonstrated that LGE is common in acute myocarditis and is associated with adverse prognosis, this study adds to our understanding by showing that not all LGE patterns seen in acute myocarditis are equivalent. While it is uncertain why basal AS LGE is particularly harmful compared to other locations, prior studies have suggested that AS LGE may be more related to human herpes virus 6 infection compared to parvovirus B19 seen more commonly with IL LGE. Differences in viral pathophysiology may contribute to differences in outcome. Alternatively, arrhythmia risk may differ by location. Given the poor yield of viral serologies and endomyocardial biopsy, CMR may have a role in future anti-inflammatory or antimicrobial trials for acute myocarditis.
Keywords: Arrhythmias, Cardiac, Biopsy, Cardiac Imaging Techniques, Chest Pain, Coronary Angiography, Defibrillators, Implantable, Electrocardiography, Edema, Gadolinium, Heart Arrest, Heart Failure, Heart Transplantation, Heart-Assist Devices, Magnetic Resonance Imaging, Myocarditis, Myocardium, Phenotype, Stroke Volume, Troponin, Troponin T
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