Feasibility of cardiac diffusion-weighted MR imaging in acute myocarditis: a pilot study

Abstract

Purpose: To prospectively determine whether diffusion-weighted cardiac MR imaging (DWI) is feasible and to determine cardiac DWI patterns in patients with acute myocarditis, by comparison with delayed-enhancement (DE) cardiac magnetic resonance (CMR) sequences.Method: Fifty-eight consecutive patients referred for CMR with a clinical presentation suggestive of acute myocarditis were included. Rest MR examinations included DWI, black-blood fat-suppressed T2-weighted, first-pass perfusion, and DE sequences. Abnormal DWI areas were matched to abnormal DE areas. The apparent diffusion coefficient (ADC) was measured in involved areas and compared to remote normal areas.Result: Qualitative assessment of DWI compared with DE images yielded a sensitivity of 92%. DWI patterns were significantly correlated to DE patterns, with focal or multifocal nonsegmental nonsubendocardial hypersignals (DWI, 2.78 ± 0.62 segments vs DE, 3.36 ± 0.63 segments, p = ns), predominantly in an inferolateral location. Qualitative assessment of DWI compared to LGE images yielded a sensitivity of 97% and a specificity of 61%. Segment-by-segment comparison showed a high level of correlation (y = (0.91) x + 0.47, r = 0.9049). The ADC of affected segments vs normal remote myocardium was 74.1 % ± 5.6 %. The absolute ADCs (abnormal DE area 0.00751±0.00042 mm2/s, normal myocardium close to abnormal DE area 0.00824±0.0004 mm2/s, and remote normal myocardium 0.00928±0.00049 mm2/s) and relative ADCs were significantly different between groups (P<0.05) except between abnormal DE area and normal myocardium close to abnormal DE area. Conclusion:Extent of myocardial involvement in myocarditis is larger, using absolute ADC measurements at DWI imaging, than expected at DE enhancement. Moreover, ADC maps should help better understand inflammatory phenomena such as an underestimated extent of lesions by late-enhancement sequences. Hence, this sequence should help better appreciate the real extent of myocardial injury in myocarditis.