Clinical impact of combined assessment of myocardial inflammation and fibrosis using myocardial biopsy in patients with dilated cardiomyopathy: a multicentre, retrospective cohort study.

Background: Among patients with dilated cardiomyopathy (DCM), myocardial inflammation and fibrosis are risk factors for poor clinical outcomes. Here, we investigated the combined prognostic value of these two factors, as evaluated using myocardial biopsy samples.

Methods: This retrospective and multicentre study included patients with DCM-defined as LVEF of ≤45% and left diastolic diameter of >112% of predicted value, without evidence of secondary or ischaemic cardiomyopathy. In myocardial biopsy samples, inflammatory cells were counted using immunohistochemistry, and Masson's Trichrome staining was performed to quantify the myocardial fibrosis as collagen area fraction (CAF). Higher myocardial inflammation was defined as leucocytes of ≥14/mm², including ≤4 monocytes/mm², with CD3 T lymphocytes of≥7/mm². Greater myocardial fibrosis was defined as CAF of>5.9% by the Youden's index. The primary endpoint was cardiac death or left ventricular assist device implantation.

Results: A total of 255 DCM patients were enrolled (average age, 53.1 years; 78% males). Within this cohort, the mean LVEF was 28.0%, mean CAF was 10.7% and median CD3 cell count was 8.3/mm. During the median follow-up period of 2688 days, 46 patients met the primary endpoint. Multivariable Cox proportional hazard analyses revealed that CD3 cell count and CAF were independent determinants of the primary endpoint. Kaplan-Meier analysis showed that patients with both higher myocardial inflammation and greater fibrosis had the worst prognosis (log-rank p<0.001). When myocardial inflammation was graded as one of three degrees: T lymphocytes of <13/mm² (low); 13 of 13.1-23.9/mm² (moderate); and T lymphocytes of ≥24 /mm² (high), patients with moderate inflammation exhibited a superior survival rate when CAF was ≤5.9%, but a worse survival rate when CAF was >5.9%.

Conclusions: Having both biopsy-proven higher myocardial inflammation and greater fibrosis predicted the worst clinical prognosis in patients with DCM.