Abstract 14438: Sensitivity of Cardiac Magnetic Resonance in Biopsy-Proven Acute Myocarditis Varies with Clinical Presentation and Necrotic vs Apoptotic Cell Death

Abstract

Introduction: Variation of CMR sensitivity in acute myocarditis is still unclear.

Hypothesis: We assessed the hypothesis that type of cell death might contribute to clinical presentation and sensitivity of CMR.

Methods: We retrospectively evaluated 57 consecutive pts with histological diagnosis of acute myocarditis (≤ 3 months). Combination of T2-weighted (edema), T1-weighted (hyperemia) and late gadolinium enhancement sequences were assessed. Presence of ≥ 2 criteria denoted myocarditis. Apoptosis and necrosis were assessed by in situ ligation of hairpin probes.

Results: Three types of clinical pattern of myocarditis were recognized: 1) Infarct-like pattern, with fever, chest pain, ST segment deflection at ECG and serum Troponin I elevation (n=21, 13 M, mean age 44.7±15.3) (panel A) 2) Cardiomyopathy pattern, with isolated left ventricular dysfunction (n=21, 18 M, mean age 52.5±16.2) 3) Arrhythmic pattern, with isolated cardiac arrhythmias (n=15, 10M, 52.6±9.0). Tissue edema was observed in 81% of pts with pattern 1 (panel B), 28% with pattern 2 and 27% with pattern 3. Hyperemia was positive in 71% of pattern 1, 67% of pattern 2 and 40% of pattern 3. Delayed enhancement was documented in 71% of pattern 1 (panel C), 57% of pattern 2 and 47% of pattern 3. The presence of at least 2 CMR features was observed in 80% of pattern 1, 57% of pattern 2 and 40% of pattern 3. Cell necrosis represented the main mechanism of death in pattern 1 (panel D) compared with pattern 2 and 3 (p<0.05) and correlated with the presence of delayed enhancement at CMR. Conversely, cardiomyocyte apoptosis was significantly higher in pattern 2 compared with pattern 1 and 3 (p<0.001).

Conclusion: Sensitivity of CMR is high for infarct-like myocarditis, low for cardiomyopathy and very low for arrhythmic pattern. A more extensive vascular involvement with cardiomyocyte necrosis in pattern 1 compared with cell apoptosis and conduction tissue damage of pattern 2 and 3, are the most likely explanation.