BACKGROUNDThe subcutaneous implantable cardioverter-defibrillator (ICD) was designed to avoid complications related to the transvenous ICD lead by using an entirely extrathoracic placement. Evidence comparing these systems has been based primarily on observational studies.
METHODSWe conducted a noninferiority trial in which patients with an indication for an ICD but no indication for pacing were assigned to receive a subcutaneous ICD or transvenous ICD. The primary end point was the composite of device-related complications and inappropriate shocks; the noninferiority margin for the upper boundary of the 95% confidence interval for the hazard ratio (subcutaneous ICD vs. transvenous ICD) was 1.45. A superiority analysis was prespecified if noninferiority was established. Secondary end points included death and appropriate shocks.
RESULTSA total of 849 patients (426 in the subcutaneous ICD group and 423 in the transvenous ICD group) were included in the analyses. At a median follow-up of 49.1 months, a primary end-point event occurred in 68 patients in the subcutaneous ICD group and in 68 patients in the transvenous ICD group (48-month Kaplan-Meier estimated cumulative incidence, 15.1% and 15.7%, respectively; hazard ratio, 0.99; 95% confidence interval [CI], 0.71 to 1.39; P = 0.01 for noninferiority; P = 0.95 for superiority). Device-related complications occurred in 31 patients in the subcutaneous ICD group and in 44 in the transvenous ICD group (hazard ratio, 0.69; 95% CI, 0.44 to 1.09); inappropriate shocks occurred in 41 and 29 patients, respectively (hazard ratio, 1.43; 95% CI, 0.89 to 2.30). Death occurred in 83 patients in the subcutaneous ICD group and in 68 in the transvenous ICD group (hazard ratio, 1.23; 95% CI, 0.89 to 1.70); appropriate shocks occurred in 83 and 57 patients, respectively (hazard ratio, 1.52; 95% CI, 1.08 to 2.12).
CONCLUSIONSIn patients with an indication for an ICD but no indication for pacing, the subcutaneous ICD was noninferior to the transvenous ICD with respect to devicerelated complications and inappropriate shocks. (Funded by Boston Scientific; PRAETORIAN ClinicalTrials.gov number, NCT01296022.
Three patients from different centers with pacemaker or ICD leads endocardially implanted in the left ventricle are described. All leads, two ventricular pacing leads and one ICD lead, were inserted through a patent foramen ovale or an atrial septum defect. The diagnosis was made 9 months, 14 months, and 16 years, respectively, after implantation. All patients had right bundle branch block configuration during ventricular pacing. Chest X ray was suggestive of a left-sided positioned lead except in the ICD patient. Diagnosis was confirmed with echocardiography in all patients. One patient with a ventricular pacing lead presented with a transient ischemic attack at 1-month postimplantation. During surgical repair of the atrial septum defect 14 months later, the lead was extracted and thrombus was attached to the lead despite therapy with aspirin. The other patients were asymptomatic without anticoagulation (9 months and 16 years after implant). No thrombus was present on the ICD lead at the time of the cardiac transplantation in one patient. We reviewed 27 patients with permanent leads described in the literature. Ten patients experienced thromboembolic complications, including three of ten patients on antiplatelet therapy. The lead was removed in six patients, anticoagulation with warfarin was effective for secondary prevention in the four remaining patients. In the asymptomatic patients, the lead was removed in five patients. In the remaining patients, 1 patient was on warfarin, 2 were on antiplatelet therapy, and in 3 patients the medication was unknown. After malposition was diagnosed, three additional patients were treated with warfarin. In conclusion, if timely removal of a malpositioned lead in the left ventricle is not preformed, lifelong anticoagulation with warfarin can be recommended as the first choice therapy and lead extraction reserved in case of failure or during concomitant surgery.
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