Implantable cardioverter-defibrillators (ICD) are well-established treatment options for patients with an increased risk for sudden cardiac death. Because complications are associated with the leads of transvenous devices, the subcutaneous ICD was designed to overcome these complications. PRAETORIAN is the first randomized study to compare the subcutaneous and transvenous ICD.¹

In PRAETORIAN, 849 patients with a Class I or IIa indication for single-chamber ICD therapy according to the prevailing American College of Cardiology, American Heart Association, and European Society of Cardiology guidelines^2-4 were included in 39 centers in Europe and the United States. Due to the inability of the subcutaneous ICD to deliver pacing, patients in anticipated need of bradypacing or antitachycardia pacing were excluded. Patients were randomized to receive either the transvenous or subcutaneous ICD and were followed until a median follow-up of 4 years was reached. Programming of the devices was standardized, whereas all other procedures were performed according to local care. The primary endpoint was the composite of ICD-related complications and inappropriate shocks. The noninferiority margin for the upper boundary of the 95% confidence interval for the hazard ratio was 1.45.

After a median follow-up of 49.1 months, the primary endpoint occurred in 68 patients randomized to the transvenous ICD group versus 68 patients in the subcutaneous ICD group (48-month Kaplan-Meier estimated cumulative incidence were 15.7% and 15.1%, respectively).⁵ The study therefore concluded the subcutaneous ICD to be noninferior to the transvenous ICD with regard to the primary endpoint (hazard ratio 0.99; 95% confidence interval, 0.71-1.39; p = 0.01 for noninferiority). There was no difference in mortality.

Although no difference was seen in the occurrence of the primary endpoint, there were differences between the groups in the occurrence of its various components. There were more patients with a device-related complication in the transvenous group than in the subcutaneous group (44 vs. 31 patients). Lead complications, consisting of pneumothorax, lead perforation, lead repositioning, and lead replacement, occurred more frequently in patients with a transvenous ICD compared to patients with a subcutaneous device (48-month Kaplan-Meier estimated cumulative incidence were 6.6% vs. 1.4%; hazard ratio 0.24; 95% confidence interval, 0.10-0.54; p = 0.001).⁶

Inappropriate shocks, defined as shocks on anything other than ventricular tachycardia or ventricular fibrillation, occurred in 29 patients in the transvenous ICD group (7.3%) and in 41 patients in the subcutaneous ICD group (9.7%). During the course of the trial, a sensing filter designed to reduce inappropriate shocks in the subcutaneous ICD was introduced. This filter showed a 50% reduction of first inappropriate shocks in an earlier study⁷ but was not available in 78% of the patients with a subcutaneous ICD at the moment of their first inappropriate shock. Therefore, the effect of this filter could not be established in this study.

Current recommendations for subcutaneous ICD implantation in U.S. and European guidelines are based on non-randomized studies.^2,3 These studies were performed in a population that mainly consisted of selected patients who were expected to have an increased risk of complications with the transvenous ICD.⁸ In PRAETORIAN, all patients in need of an ICD without pacing indication were included such that the trial population was comparable to the population in other ICD trials with regard to indication, age, and co-morbidities.^9,10 PRAETORIAN is therefore the first trial to show in a general ICD population that the subcutaneous ICD is an equal treatment option in comparison to the transvenous ICD. Because both devices have different risk profiles, and because complications can be experienced differently between patients, the decision in favor of one treatment over the other should be made based on patient-specific needs and preferences.

The current results are based on a median follow-up of 4 years. However, ICD therapy can last much longer, and ICD-related complications increase over time.¹¹ To get more long-term information on the ongoing risk of appropriate and inappropriate therapy, lead complications, and other device-related complications, follow-up of the PRAETORIAN trial is prolonged with 4 years.

PRAETORIAN is an investigator-initiated trial, which was funded by Boston Scientific (Marlborough, MA), the manufacturer of the subcutaneous ICD.

References

1. Olde Nordkamp LR, Knops RE, Bardy GH, et al. Rationale and design of the PRAETORIAN trial: a Prospective, RAndomizEd comparison of subcuTaneOus and tRansvenous ImplANtable cardioverter-defibrillator therapy. Am Heart J 2012;163:753-760.e2.
2. Al-Khatib SM, Stevenson WG, Ackerman MJ, et al. 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death: Executive Summary: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. J Am Coll Cardiol 2018;72:1677-749.
3. Priori SG, Blomström-Lundqvist C. 2015 European Society of Cardiology Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death summarized by co-chairs. Eur Heart J 2015;36:2757-9.
4. Zipes DP, Camm AJ, Borggrefe M, et al. ACC/AHA/ESC 2006 Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death: a report of the American College of Cardiology/American Heart Association Task Force and the European Society of Cardiology Committee for Practice Guidelines (writing committee to develop Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death): developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society. Circulation 2006;114:e385-484.
5. Knops RE, Olde Nordkamp LRA, Delnoy PHM, et al. Subcutaneous or Transvenous Defibrillator Therapy. N Engl J Med 2020;383:526-36.
6. Knops RE. PRAETORIAN: a prospective, randomized comparison of subcutaneous and transvenous implantable cardioverter-defibrillator therapy. Presented at Heart Rhythm Scientific Sessions 2020, May 8, 2020.
7. Theuns DA, Brouwer TF, Jones PW, et al. Prospective blinded evaluation of a novel sensing methodology designed to reduce inappropriate shocks by the subcutaneous implantable cardioverter-defibrillator. Heart Rhythm 2018;15:1515-22.
8. Burke MC, Gold MR, Knight BP, et al. Safety and Efficacy of the Totally Subcutaneous Implantable Defibrillator: 2-Year Results From a Pooled Analysis of the IDE Study and EFFORTLESS Registry. J Am Coll Cardiol 2015;65:1605-15.
9. Healey JS, Hohnloser SH, Glikson M, et al. Cardioverter defibrillator implantation without induction of ventricular fibrillation: a single-blind, non-inferiority, randomised controlled trial (SIMPLE). Lancet 2015;385:785-91.
10. Moss AJ, Schuger C, Beck CA, et al. Reduction in inappropriate therapy and mortality through ICD programming. N Engl J Med 2012;367:2275-83.
11. Ranasinghe I, Parzynski CS, Freeman JV, et al. Long-Term Risk for Device-Related Complications and Reoperations After Implantable Cardioverter-Defibrillator Implantation: An Observational Cohort Study. Ann Intern Med 2016;165:20-9.

Clinical Topics: Arrhythmias and Clinical EP, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias

Keywords: Arrhythmias, Cardiac, Ventricular Fibrillation, Defibrillators, Implantable, American Heart Association, Confidence Intervals, Pneumothorax, Follow-Up Studies, Death, Sudden, Cardiac, Tachycardia, Ventricular, Cardiology, Longitudinal Studies

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