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Active versus borderline myocarditis: clinicopathological correlates and prognostic implications
A Angelini1, M Crosato, G M Boffa
1Department of Pathology, University of Padua Medical School, Padua, Italy.
Insights
Active (AM) versus borderline (BM) myocarditis shows distinct clinical and pathological features. Borderline myocarditis may represent a chronic inflammatory process, with viral genome absence predicting a better prognosis.
Area of Science:
- Cardiology
- Pathology
- Infectious Diseases
Background:
- Myocarditis, inflammation of the heart muscle, is classified histologically.
- Distinguishing between active (AM) and borderline (BM) myocarditis may offer prognostic insights.
Purpose of the Study:
- To compare active (AM) and borderline (BM) myocarditis.
- To determine if pathological differences correlate with clinical, hemodynamic characteristics, and prognosis.
Main Methods:
- Retrospective review of 42 patients diagnosed with myocarditis via endomyocardial biopsy (EMB).
- Analysis included immunohistochemistry and polymerase chain reaction (PCR) for viral genomes.
- Clinicopathological correlations were assessed.
Main Results:
- Active myocarditis (AM) showed less left bundle branch block and smaller left ventricular volumes compared to borderline myocarditis (BM).
- BM cases had a longer interval to EMB and less intense inflammatory infiltrates.
- Viral genomes were detected in 40% of AM and 25% of BM cases; absence of viral genome predicted better outcomes.
Conclusions:
- Borderline myocarditis (BM) may represent a chronic inflammatory condition leading to left ventricular dilatation.
- "Chronic myocarditis" may be a more fitting term for BM.
- Absence of myocyte necrosis does not guarantee a favorable prognosis, but absence of viral detection does.
Objective:
To compare active (AM) with borderline (BM) myocarditis to verify whether the pathological distinction between the two forms may help to identify patients with different clinical and haemodynamic characteristics and to aid prognosis.
Materials:
Myocarditis was diagnosed in 56 patients on endomyocardial biopsy (EMB) within one year from clinical onset of the disease between 1991 and 1998. Fourteen patients were excluded because of a lack of adequate and complete information. EMBs and clinical records of the 42 remaining patients were reviewed. Immunohistochemistry on bioptic samples was regularly performed. Polymerase chain reaction (PCR) for a panel of viruses was performed in 23 patients (55%). Clinicopathological correlations were calculated.
Results:
The histological diagnosis was AM in 26 patients (62%) and BM in 16 (38%). Significant differences were found in the following parameters: presence of left bundle branch block on ECG (AM 2 (8%) v BM 5 (31%), p = 0.05); left ventricular volume on echocardiogram (mean (SD) AM 90 (42) ml/m(2) v BM 128 (50) ml/m(2), p = 0.002); mass to volume ratio (AM 1.0 (0) v BM 0.8 (0.1), p = 0.03); time interval between clinical onset of the disease and EMB (AM 40 (55) v BM 90 (93) days, p = 0.04); and degree of inflammatory infiltrates, scored on a scale of 0 to 3 (AM 1.65 (0.8) v BM 0.85 (0.3), p = 0.004). In 6 of 15 patients (40%) with AM and in 2 of 8 (25%) with BM, a viral genome was detected by PCR (NS). At follow up, no differences in death or heart transplantation were detected between the two forms (AM 4 patients (15%) v BM 2 patients (12.5%)). Three of eight PCR positive patients (37.5%) and 1 of 15 virus negative patients (7%) died or underwent heart transplantation.
Conclusions:
BM seems to encompass inflammatory forms with a less aggressive inflammatory infiltrate evolving towards left ventricular dilatation. The term "chronic myocarditis" seems to be more appropriate. The absence of myocyte necrosis does not predict a more favourable prognosis, whereas the absence of a viral genome seems to predict it.