3 Incidence and predictors of sudden cardiac death in dilated cardiomyopathy with improved ejection fraction

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Introduction Many patients with dilated cardiomyopathy (DCM) undergo improvement in left ventricular ejection fraction (LVEF). Although DCM with improved LVEF (DCMimpEF) is associated with favourable clinical outcomes, cases of sudden cardiac death (SCD) have been reported in this population. Myocardial fibrosis, detected by late gadolinium enhancement (LGE) on cardiovascular magnetic resonance (CMR) is associated with SCD in patients with DCM with impaired systolic function, including those with mildly reduced LVEF; whether this association exists in patients with DCMimpEF has not been specifically evaluated. We sought to identify the incidence and determinants of SCD events in patients with DCMimpEF. Methods This was a prospective observational cohort study of patients with DCM referred for a CMR. Inclusion criterion was a confirmed diagnosis of DCM with a previously recorded LVEF <40% that had subsequently improved to LVEF ≥40% on the study enrolment CMR. Patients underwent long-term clinical follow up. The primary endpoint was a composite of SCD or aborted SCD (aSCD). aSCD was defined as either an appropriate ICD shock for a ventricular arrhythmia, or a non-fatal episode of ventricular fibrillation (VF) or spontaneous sustained ventricular tachycardia (VT) causing hemodynamic compromise and requiring cardioversion. All potential arrhythmic events were reviewed by a panel of experienced cardiologists, including a cardiologist with expertise in implantable cardiac devices. Adjudicators were blinded to clinical and CMR data. Cumulative incidence curves were fitted using Kaplan-Meier method and compared using log-rank test. The association between patient characteristics and the primary endpoint was examined using univariable Cox proportional hazard modelling. Results The study cohort comprised 141 patients with DCMimpEF (63.8% male, median age 56 years [interquartile range 44–64], median improved LVEF at enrolment 48% [44–52]). Most patients were NYHA class 1 or 2 (87%). A high proportion were treated with ACE inhibitors or angiotensin receptor blockers (88%) and beta blockers (75%); a modest proportion were treated with mineralocorticoid receptor antagonists (36%). Late gadolinium enhancement was present in 49/141 patients (35%). Over a median follow up of 7.8 years, 7 patients (5%) experienced SCD events. This included 3 patients who survived resuscitated VF/VT cardiac arrests and 4 patients who had appropriate ICD shocks for VT/VF. The presence of LGE on CMR was associated with a higher cumulative incidence of SCD/aSCD (log rank p=0.03, figure 1). No other variables were associated with SCD/aSCD in patients with DCMimpEF. Conclusions Despite improved cardiac function and low symptom burden, a small proportion of patients with DCMimpEF remain at risk of SCD. The presence of LGE does not preclude LVEF improvement but does render patients with DCMimpEF at higher risk of incident SCD events. These data support long-term clinical follow up of patients with DCM beyond the point of LVEF improvement. Our findings lend further support for the use of CMR for arrhythmic risk stratification in DCM and call into question the continued reliance on LVEF to determine ICD candidacy in this population. Conflict of Interest Nil

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