Background: Previous autopsy studies demonstrated that patients with nonischaemic dilated cardiomyopathy (DCM) present not only with replacement fibrosis, detectable with late gadolinium enhancement (LGE) at cardiovascular magnetic resonance (CMR), but also with diffuse interstitial fibrosis. Therefore, we investigated the prevalence and prognostic value of interstitial fibrosis in DCM, detected by extracellular volume fraction (ECV) calculation through the CMR T1-mapping.
Methods: A prospective cohort of 89 DCM patients (63 males, age 59±14 years) with left ventricular systolic dysfunction (ejection fraction 41±13%), without (stage B, n=23) or with heart failure (HF) symptoms (stage C, n=66) was enrolled. Patients underwent a thorough biohumoral, clinical, instrumental evaluation, including Holter EKG recording, as well as CMR ECV evaluation from pre- and post-contrast T1 mapping. Thirty healthy subjects (21 males, age 39±17 years) served as controls. The end-point was a composite of cardiovascular death, HF hospitalization, sustained ventricular arrhythmias.
Results: Myocardial ECV was significantly higher in DCM patients (0.31±0.04) than controls (0.26±0.04, p<0.01), correlating with left ventricular ejection fraction (R2=0.13), LGE extent (R2=0.17), Doppler E/E’ (R2=0.17) and ventricular tachycardias (R2=0.21) at Holter recording. Even DCM patients without LGE (n=50) presented a myocardial ECV (0.29±0.05) higher than controls (p=0.01).
During a 24-month median follow-up (IQR 12-42), 12 events occurred (1 cerebrovascular death, 6 appropriate defibrillator interventions, 5 HF hospitalizations. At univariate Cox-regression analysis, clinical (previous duration of cardiomyopathy, diabetes, B-type natriuretic peptides), electrocardiographic (ventricular arrhythmias, average heart rate, low heart rate variability) and CMR parameters (LV dilation/systolic dysfunction, ECV) all resulted predictors. At bivariate Cox analysis with all significant variables, ECV remained a significant predictor of the composite event (p<0.05).
Conclusions: In DCM patients, myocardial interstitium is increased, as compared to healthy subjects, reflecting extracellular matrix remodelling and collagen deposition, with an independent negative prognostic value beyond conventional parameters.
