Design: Prospective, global, single-arm post-approval registry
Population: 787 patients with an attempted extravascular ICD implant, 168 implanters
Primary outcome: Freedom from major system- or procedure-related complications at 1 year
Effect: 89.1% (95% CI 86.3–91.3%); appropriate therapy 7.3%; inappropriate shock 7.1%

The Enlighten post-approval registry followed 787 people in whom 168 implanters attempted an extravascular ICD, with the lead tunnelled into the substernal space. They were mostly young (mean age 49), and a third had a secondary prevention indication.

Substernal lead placement succeeded in 99.2%, and 96.3% remained implanted after defibrillation testing. Freedom from major system- or procedure-related complications at one year was 89.1%. Appropriate therapy occurred in 7.3%, all 61 discrete spontaneous episodes were terminated by shock, and antitachycardia pacing ended about three quarters of monomorphic ventricular tachycardia. Inappropriate shocks occurred in 7.1%, most often from non-cardiac oversensing.

The device offers pacing for ventricular tachycardia without a lead inside the heart, which is the trade-off it aims to settle against transvenous and subcutaneous systems. An inappropriate shock rate of about one in fourteen in the first year is not trivial. This is a single-arm, manufacturer-linked registry without a comparison group.

Consider the extravascular ICD for younger patients where avoiding a transvenous lead matters and pacing for VT is wanted.
Counsel that about one in fourteen had an inappropriate shock in the first year.
Review sensing and programming early, since non-cardiac oversensing caused most inappropriate shocks.
Expect a learning curve: substernal tunnelling is a new skill for most implanting teams.

Why it matters

It is the first large check that the device behaves outside trial centres the way it did inside them.

The statistics, in plain English

The rates are Kaplan–Meier estimates, which account for people followed for less than a full year. Without a control group, the registry can say how the device performs, not whether it beats a transvenous or subcutaneous ICD.