Follow-up Imaging for Myocarditis with Reduced Ejection Fraction
Cardiac MRI (CMR) should be performed at 3-6 months after diagnosis to assess resolution of inflammation and myocardial edema, with echocardiography used for serial monitoring of left ventricular function during this period. 1
Initial Follow-up Imaging Strategy
Cardiac MRI Timing and Indications
CMR is the gold standard for follow-up assessment and should be performed to evaluate resolution of inflammation (T2-weighted imaging for edema) and assess for persistent late gadolinium enhancement (LGE), which indicates myocardial scar and potential arrhythmia substrate 1
For patients with reduced LVEF at diagnosis, repeat CMR at 3 months minimum before considering return to full activities, as this timeframe allows assessment of functional recovery and resolution of active inflammation 1
Recent evidence from COVID-19 vaccine-associated myocarditis suggests that follow-up CMR at approximately 3 months shows improvement in LGE in all patients, though persistence is common (80% still had some LGE), indicating the need for continued monitoring 2
Echocardiography for Serial Monitoring
Transthoracic echocardiography should be performed serially to monitor left ventricular systolic function, assess for development of complications (thrombi, pericardial effusion), and evaluate secondary valvular regurgitation 3, 4
The European Society of Cardiology recommends reassessment of myocardial structure and function using non-invasive imaging in patients presenting with worsening heart failure symptoms or experiencing any other important cardiovascular event 1
Echocardiography is particularly useful for monitoring significant changes in wall motion during the disease course, even though it has limited ability to directly visualize inflammation compared to CMR 3, 4
Criteria for Return to Normal Function
Prerequisites Before Discontinuing Close Monitoring
For patients with reduced LVEF at diagnosis, all of the following must be met before considering resolution 1:
- Minimum 3 months without symptoms
- LV systolic function returned to normal range (LVEF >50%)
- Resolution of inflammation or edema by CMR imaging (T2 signal) or serum biomarkers
- Absence of clinically relevant arrhythmias on ambulatory ECG monitoring and exercise testing
Long-term Imaging Surveillance
Even after LVEF normalization, continued medical therapy should be maintained, as withdrawal of guideline-directed medical therapy (GDMT) in patients with recovered dilated cardiomyopathy led to heart failure events in nearly 50% within 6 months 1
Annual echocardiography is reasonable for stable patients to monitor for late deterioration, particularly given that larger biventricular volumes and ischemic LGE patterns at diagnosis predict worse functional outcomes 5
Follow-up CMR at 6-12 months after the acute episode should be considered to better understand long-term cardiac risks, especially given the persistence of LGE in most patients at 3-month follow-up 2
Prognostic Imaging Features
Favorable Prognostic Indicators on CMR
- Higher biventricular systolic function at diagnosis predicts better functional class and higher LVEF at follow-up 5
- Greater LGE extent at diagnosis paradoxically had a protective effect in one study, though this requires validation 5
- Normal CMR in patients with suspected myocarditis indicates good long-term prognosis, independent of clinical and other findings 1
Adverse Prognostic Indicators
- Larger biventricular volumes at diagnosis predict worse functional class and LV systolic dysfunction at follow-up 5
- CMR-based features of dilated cardiomyopathy and ischemic LGE pattern at diagnosis are predictors of worse outcomes 5
- Persistent LGE at 4 weeks after onset indicates adverse prognosis 1
Common Pitfalls and Caveats
Do not rely solely on echocardiography for follow-up assessment, as it cannot accurately differentiate myocardial edema from wall hypertrophy and may appear completely normal in less severe forms of myocarditis 4
Do not discontinue GDMT even if LVEF normalizes, unless there is a clearly defined reversible cause (e.g., tachycardia-mediated cardiomyopathy), as recurrence rates are high 1, 6
Speckle tracking echocardiography can detect subtle dysfunction even when LVEF appears preserved, with global longitudinal strain often remaining abnormal despite improvement in circumferential strain during follow-up 7
Improvement in LVEF can occur even with ongoing histological inflammation, so functional improvement does not necessarily indicate complete resolution of myocarditis 8