Quantification of Diffuse Myocardial Fibrosis and its Association with Myocardial Dysfunction in Congenital Heart Disease
OBJECTIVES: The etiology of ventricular dysfunction in adult congenital heart disease (ACHD) is not well understood. Diffuse fibrosis is a likely common final pathway and is quantifiable using magnetic resonance imaging (MRI).
METHODS: ACHD patients (N=50) were studied with cardiac MRI to quantify systemic ventricular volume and function, and diffuse fibrosis. The fibrosis index for a single mid-ventricular plane of the systemic ventricle was quantified by measuring T1 values for blood pool and myocardium before and after administration of gadolinium (0.15 mmol/kg), then adjusted for hematocrit.
RESULTS: Results were compared to healthy volunteers (normal controls, N=14) and patients with acquired heart failure (positive controls, N=4). Patients studied (age 37±12 years, 40% female) included 11 with a systemic right ventricle (RV), 17 with tetralogy of Fallot, 10 with cyanosis and 12 with other lesions. The fibrosis index was significantly elevated in ACHD patients compared to normal controls (31.9±4.9% vs. 24.8±2.0%, p=0.001). Values were highest in systemic RV patients (35.0±5.8%, p<0.001) and cyanotic patients (33.7±5.6%, p<0.001). The fibrosis index correlated with end-diastolic volume index (r=0.60, p<0.001) and ventricular ejection fraction (r=-0.53, p<0.001), but not with age, nor oxygen saturation in cyanotic patients. Late gadolinium enhancement did not account for the differences seen.
CONCLUSIONS: ACHD patients have evidence of diffuse, extracellular matrix remodeling, similar to patients with acquired heart failure. The fibrosis index may facilitate studies on the mechanisms and treatment of myocardial fibrosis and heart failure in these patients.
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