Life-threatening Ventricular Arrhythmias in Cardiac Sarcoidosis with Implantable Devices: Incidence and Predictors in a UK Cohort.

BACKGROUND: In cardiac sarcoidosis (CS), life-threatening ventricular arrhythmias (VAs) are a major determinant of sudden cardiac death risk. The burden of device-detected sustained VA in UK patients with CS, particularly across guideline-based implantable cardioverter-defibrillator (ICD) indication categories, remains incompletely characterised. METHODS: Consecutive patients with CS who received a cardiac implantable electronic device (CIED) at a UK tertiary centre between 2006 and 2024 were analysed. Patients were stratified at device implantation according to the 2014 Heart Rhythm Society ICD indication category (Class I, Class IIa, or Neither). The primary endpoint was sustained VA, defined as appropriate device therapy, resuscitated cardiac arrest with documented ventricular tachycardia (VT) or ventricular fibrillation (VF), or symptomatic sustained VT lasting ≥30 seconds. Clinical, echocardiographic, cardiac magnetic resonance, and positron emission tomography variables were evaluated as predictors of VA. RESULTS: Among 275 patients (Class I, n=114; Class IIa, n=91; Neither, n=70), 5-year Kaplan-Meier VA incidence was 46.1% in Class I, 19.3% in Class IIa, and 18.7% in the Neither group. Crude 5-year VA incidence was 35.1% (40/114), 16.5% (15/91), and 12.9% (9/70), respectively (p<0.001). On multivariable Cox analysis, baseline sustained VT and lower LVEF were independently associated with incident VA. LGE extent was associated with VA on univariable but not multivariable analysis. CONCLUSIONS: VA risk was highest in patients meeting Class I ICD indications but remained clinically meaningful among those without Class I indications. These findings support continued rhythm surveillance and longitudinal risk reassessment in CS.