Relationship of myocardial fibrosis to left ventricular and mitochondrial function in nonischemic dilated cardiomyopathy--a comparison of focal and interstitial fibrosis.

Background: Mitochondrial damage is associated with histologic myocardial fibrosis. Late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) can be used to identify focal fibrosis. We examined whether myocardial fibrosis on CMR and collagen volume fraction (CVF) from biopsies correlated with left ventricular (LV) and mitochondrial function in patients with nonischemic dilated cardiomyopathy (DCM).

Methods And Results: Fifty-nine DCM patients underwent CMR, cardiac catheterization, and endomyocardial biopsy. Minimum first derivative of LV pressure (LVdP/dt(min)) was measured as an index of LV relaxation. Mitochondrial RNA expression was also analyzed. For quantitative analysis of myocardial fibrosis, percentage LGE (%LGE) and CVF were calculated. Patients were divided into 2 groups on the basis of the presence (LGE group; n = 27) or absence (non-LGE group; n = 32) of LGE. Mean CVF and absolute value of LVdP/dt(min) were significantly higher and lower, respectively, in the LGE group than in the non-LGE group. Multivariate analysis revealed that %LGE was an independent determinant of LVdP/dt(min). The abundance of mitochondrial enzyme mRNA was significantly lower in the LGE group.

Conclusions: Noninvasive CMR imaging is more useful in predicting diastolic dysfunction than invasive histologic assessments. In addition, it might indicate mitochondrial dysfunction in DCM.