Prognostic impact of atrio-ventricular conduction abnormalities in non-ischemic cardiomyopathy

<b>Aims</b><br/>To assess the prognostic value of atrioventricular block (AVB) in a contemporary cohort of patients with non-ischemic cardiomyopathy (NICM) studied with cardiac magnetic resonance (CMR), focusing on the potential improvement of risk stratification among patients with late gadolinium enhancement (LGE+).<br/><br/><b>Methods and results<br/></b>Retrospective cohort study at two tertiary care hospitals including 616 NICM patients, with assessment of AVB at ECG and LGE at CMR. The primary arrhythmic endpoint included any appropriate ICD therapy, sustained monomorphic ventricular tachycardia, resuscitated cardiac arrest and sudden death. The secondary heart failure (HF) endpoint included HF hospitalization, heart transplant, left ventricular assist device implant and death due to end stage HF. <br/>First-, second- or third degree AVB was observed in 9% of patients and it was associated with worse clinical profile, including more severe cardiac dysfunction (LVEF 29% vs 37%, p&lt;0.001) and higher prevalence of LGE (63% vs 46%, p=0.02). AVB independently predicted the combined arrhythmic endpoint on top of LGE and LVEF (HR 2.7, p=0.007), and was particularly impactful when present alongside LGE: among LGE+ patients, AVB significantly increased the risk of the primary endpoint (adjusted HR 3.4, p&lt;0.001). <br/>By contrast, AV block was not a significant predictor of the heart failure endpoint at multivariate analysis (p=0.11).<br/><br/><b>Conclusions</b><br/>AVB is a strong and independent predictor of VA and SD in NICM, on top of LGE and LVEF. In addition, AVB has a significant impact on the risk-stratification of LGE+ cases, identifying a small sub-group of patients with extremely high arrhythmic risk.<br/>