Introduction Diffusion Tensor Cardiovascular Magnetic Resonance (DT-CMR) assesses myocardial microstructure in vivo, providing information on myocyte and sheetlet organisation. Dilated cardiomyopathy (DCM) patients exhibit impaired sheetlet mobility. Approximately 1/3 DCM patients recover (R-DCM), exhibiting improved left ventricular (LV) size and ejection fraction (EF). However, there has been no study of microstructural recovery in R-DCM.

Methods DT-CMR was performed in 12 DCM, 12 R-DCM, and 12 control subjects. R-DCM patients had normal indexed LV size and EF. A STEAM-EPI sequence with b=150 and b=600 at 3 T was used. LV cardiomyocyte orientation (helix angle, HA), sheetlet orientation (secondary eigenvector angulation, E2A), EF and peak radial strain were calculated. The Mann-Whitney test was used for statistical analysis.

Results Groups were age and sex matched. In R-DCM, median [IQR] EF at baseline was 27[13]% and current EF was 64[7]%. The EF was 33[16]% in DCM, and 66[4]% in controls. Median [IQR] diastolic E2A in R-DCM was 25[9]°, similar to DCM (19[11]°, p=0.11) and controls (20[14]° p=0.24). However, systolic E2A in R-DCM was 59[14]°, significantly greater than DCM (35[17]° (p<0.0001), but lower than controls (65[8]°, p=0.01). E2A mobility was 35[10]° in R-DCM, greater than DCM (9.6[16]°, p<0.0001), but less than controls (46[10]°, p=0.001). Peak radial strain was 0.42 [0.14] in R-DCM, more than DCM, (0.18 [0.17], p=0.002), but less than controls (0.55 [0.17], p=0.009).

Conclusion Despite normal LV size and EF, R-DCM patients have persistent microstructural abnormalities. Sheetlet mobility may offer a role in disease monitoring and assessment of recovery.