Evaluation of subcutaneous implantable cardioverter-defibrillator performance in patients with ion channelopathies from the EFFORTLESS cohort and comparison with a meta-analysis of transvenous ICD outcomes

Figure 1. Diagnoses in the EFFORTLESS channelopathy and non-channelopathy cohorts. ARVD = arrhythmogenic right ventricular dysplasia; CAD = coronary artery disease; CPVT = catecholaminergic polymorphic ventricular tachycardia; DCM = dilated cardiomyopathy; HCM = hypertrophic cardiomyopathy; iVF = idiopathic ventricular fibrillation; MI = myocardial infarction.

Figure 2. Inappropriate shocks in channelopathy and non-channelopathy patients. A: Burden and etiology of inappropriate shocks in the 2 groups. (Subcategories do not sum to the “All Cause” total because some patients had inappropriate shocks in more than 1 category.) “Rate > Shock Zone” = supraventricular tachycardia (SVT) with a heart rate > shock zone cutoff. “Rhythm Discrimination” = SVT with a heart rate in the conditional zone. B: Incidence of inappropriate shocks with dual- and single-zone programming (by patients). VF = ventricular fibrillation; VT = ventricular tachycardia.

Figure 3. Small-amplitude electrocardiograms resulting in T-wave oversensing. A: Brugada patient with heart rate at 180 beats per minute (bpm). B: Long QT syndrome patient with heart rate at 160 bpm. The QRS amplitude is small, resulting in T-wave oversensing with increase in QRS:T-wave ratio post shock and correct QRS sensing.

Figure 4. Proposed strategy to avoid inappropriate shocks in channelopathy patients. Ideally, >1 vector should be identified to allow more programming options if T-wave oversensing occurs.