Subcutaneous Defibrillator for Primary Prevention in Chronic Kidney Disease Stage 3-5: The Single-Arm STEADIED Study

Prospective data on the subcutaneous implantable cardioverter-defibrillator (S-ICD) in chronic kidney disease (CKD) are lacking. We estimated the rate of appropriate ICD therapy with the S-ICD in CKD stage 3-5 with left ventricular ejection fraction (LVEF) ≤ 35%.

In this single-arm exploratory study, adults with CKD stage 3-5 and a guideline-based primary-prevention indication received an EMBLEM MRI S-ICD at eight Korean centers. The primary endpoint, appropriate ICD therapy, was hypothesized at 18% versus a historical rate of 7.8% (α = 0.05, 80% power, planned N = 77; exact binomial test).

The study was terminated early after 39 patients (51% of target; achieved power ≈61%). Mean LVEF was 27.8% and median eGFR 11.7 mL/min/1.73 m²; 71.8% had CKD stage 5 and 69.2% were on hemodialysis. Over a median follow-up of 361 days, appropriate ICD therapy occurred in 2 patients (5.1%; 95% CI, 1.4-16.9), significantly below the hypothesized 18% (p = 0.036). Inappropriate shocks occurred in 5 patients (12.8%; 95% CI, 5.6-26.7; 8 shocks), a proportion 2.5 times that of appropriate therapy, from external electromagnetic interference (2 patients), multiple counting after automatic SMART Pass deactivation (2), and supraventricular misclassification (1). Three deaths (7.7%) occurred, none device-related or documented as arrhythmic (one undetermined); all hospitalizations were for heart failure, and no systemic device infection occurred.

In this exploratory single-arm study, appropriate ICD therapy was infrequent and exceeded by inappropriate shocks, while non-arrhythmic competing mortality dominated the clinical course. These hypothesis-generating findings support cautious patient selection, verification of filter status during follow-up, and larger comparative studies.

Clinical Research Information Service (CRIS), Republic of Korea; identifier KCT0005596.