Aims Patients with Ebstein’s anomaly of the tricuspid valve (EA) are at risk of tachyarrhythmia, congestive heart failure and sudden cardiac death. We sought to determine the value of cardiovascular magnetic resonance (CMR) for predicting these outcomes.

Methods and Results Seventy-nine consecutive adult patients (aged 37 ± 15 years) with unrepaired EA underwent CMR and were followed prospectively for a median 3.4 (range 0.4–10.9) years for clinical outcomes, namely major adverse cardiovascular events (MACE: sustained ventricular tachycardia/heart failure hospital admission/cardiac transplantation/death) and first-onset atrial tachyarrhythmia (AT).

Univariable CMR predictors of MACE (n = 6) were right ventricular (RV) or left ventricular (LV) ejection fraction (HR 2.06 [95% CI 1.168–3.623], p = 0.012/5% and HR 2.35 [95% CI 1.348–4.082], p = 0.003/5%, respectively), LV stroke volume index (HR 2.82 [95% CI 1.212–7.092], p = 0.028/10mL) and cardiac index (HR 1.71 [95% CI 1.002–1.366], p = 0.037); all remained significant when tested solely for mortality. Prior history of AT (HR 11.16 [95% CI 1.30–95.81], p = 0.028) and NYHA class >2 (HR 7.66 [95% CI 1.54–38.20], p = 0.013) were also predictive of MACE; AT preceded all but one MACE events suggesting its potential role as an early marker of adverse outcome (p = 0.011). Bi-ventricular impairment carried nearly 9 fold increased risk of adverse outcome (HR 8–69 [95% CI 1.57–48.10], p = 0.001).

Univariable predictors for first-onset AT (n = 17; 21.5%) included functional RA volume index (HR 1.03[95% CI 1.01–1.04], p = 0.005), RV ejection fraction (HR 1.55 [95% CI 1.103–2.160], p = 0.011/5%)], RV/LV end diastolic volume ratio (HR 1.55 [95% CI 1.14–2.10], p = 0.005) and apical tricuspid septal leaflet displacement indexed to total LV septal length (HR 1.03 [95% CI 1.00–1.07], p = 0.041); the latter two combined enhanced risk prediction (HR 6.12 [95% CI 1.67–22.56], p = 0.007).

Conclusion CMR derived indices carry prognostic information regarding MACE and first-onset AT amongst adults with unrepaired EA. CMR may be included in the periodic surveillance of these patients.