Residual fibrosis affects a long-term result of left ventricular volume reduction surgery for dilated cardiomyopathy in a rat experimental study?

OBJECTIVES: The aim of this study is to evaluate the relationship between left ventricular (LV) wall property and the results of LV volume reduction surgery (LVR) to treat dilated cardiomyopathy (DCM) in an experimental model. METHODS: DCM was introduced in 18 Lewis rats by autoimmunization with cardiac myosin. Among them, 12 rats underwent LVR and the rest were served as controls. They were subjected to echocardiography and cardiac catheterization for dimensional and functional measurements. The animals were sacrificed 4 weeks after surgery, and the fraction of myocardial fibrosis was calculated in 4 divided parts of the LV wall. RESULTS: Percent fibrosis varied widely from 4.7 to 45.2%. LV volume reduction surgery improved cardiac function immediately after surgery in all rats (Emax, 0.28+/-0.14 to 0.48+/-0.18 mmHg/microl; LV end-diastolic pressure, 21.0+/-6.1 to 13.3+/-5.1 mmHg, P<0.05, respectively). Four weeks later, 6 hearts remained in good shape with smaller LV end-diastolic dimension (Dd) than baseline values (LV Dd, 9.7+/-0.6mm; fractional area change (FAC), 40.3+/-8.4%) and the other 6 had more redilation in diameter and more deterioration in function than baseline values (LV Dd, 10.9+/-0.6mm; FAC, 25.8+/-6.9%; P<0.05, respectively). Percent fibrosis in the septum differed 11.1+/-3.4 vs. 27.8+/-2.8% between the two groups (P<0.01). There was a significant correlation between the ratio of LV redilatation after surgery and percent fibrosis in the septum (r=0.951, P<0.01). CONCLUSIONS: Although the initial benefit of LVR was confirmed, the long-term result was affected by the amount of residual fibrosis. This information suggests that surgical site selection is important to achieve a good result of LV restoration surgery for DCM.