Regional heterogeneity of function in nonischemic dilated cardiomyopathy.

OBJECTIVE: To quantify regional three-dimensional (3D) motion and myocardial strain using magnetic resonance (MR) tissue tagging in patients with non-ischemic dilated cardiomyopathy (DCM).
METHODS: MR grid tagged images were obtained in multiple short- and long-axis planes in thirteen DCM patients. Regional 3D displacements and strains were calculated with the aid of a finite element model. Five of the patients were also imaged after LV volume reduction by partial left ventriculectomy (PLV), combined with mitral and tricuspid valve repair.
RESULTS: DCM patients showed consistent, marked regional heterogeneity. Systolic lengthening occurred in the septum in both circumferential (%S(C) -5+/-7%) and longitudinal (%S(L) -2+/-5%) shortening components (negative values indicating lengthening). In contrast, the lateral wall showed relatively normal systolic shortening (%S(C) 12+/-6% and %S(L) 6+/-5%, P<0.001 lateral vs. septal walls). A geometric estimate of regional stress was correlated with shortening on a regional basis, but could not account for the differences in shortening between regions. In the five patients imaged post-PLV, septal function recovered (%S(C) 9+/-5%,%S(L) 6+/-5%, P<0.02 pre vs. post) with normalization of wall stress, whereas lateral wall shortening was reduced (%S(C) 7+/-6%,%S(L) 3+/-3%, P<0.02 pre vs. post) around the site of surgical resection.
CONCLUSIONS: A consistent pattern of regional heterogeneity of myocardial strain was seen in all patients. Reduced function may be related to increased wall stress, since recovery of septal function is possible after PLV. However, simple geometric stress determinants are not sufficient to explain the functional heterogeneity observed.