Therapy From a Novel Substernal Lead The Acute Extravascular De fi brillation, Pacing, and Electrogram (ASD2) Study

OBJECTIVES The ASD2 (Acute Extravascular De fi brillation, Pacing, and Electrogram) study evaluated the ability to adequately sense, pace, and de fi brillate patients with a novel implantable cardioverter-de fi brillator (ICD) lead implanted in the substernal space. BACKGROUND Subcutaneous ICDs are an alternative to a transvenous de fi brillator system when transvenous implantation is not possible or desired. An alternative extravascular system placing a lead under the sternum has the potential to reduce de fi brillation energy and the ability to deliver pacing therapies. METHODS An investigational lead was inserted into the substernal space via a minimally invasive subxiphoid access, and a cutaneous de fi brillation patch or subcutaneous active can emulator was placed on the left mid-axillary line. Pacing thresholds and extracardiac stimulation were evaluated. Up to 2 episodes of ventricular fi brillation were induced to test de fi brillation ef fi cacy. RESULTS The substernal lead was implanted in 79 patients, with a median (cid:1) SD implantation time of 12.0 (cid:1) 9.0 min. Ventricular pacing was successful in at least 1 vector in 76 of 78 patients (97.4%), and 72 of 78 (92.3%) patients had capture in $ 1 vector with no extracardiac stimulation. A 30-J shock successfully terminated 104 of 128 episodes