Antitachycardia pacing for very fast ventricular tachycardia and low-energy shock for ventricular arrhythmias in patients with implantable defibrillators.

Implantable cardioverter-defibrillator therapy in the form of high-energy shock (HES) is associated with adverse effects. This study evaluated an alternative therapy to HES, including antitachycardia pacing (ATP) for very fast ventricular tachycardia (VFVT) and low-energy shock (LES) ≤5 J for ventricular tachycardia (VT) of any cycle length (CL). This multicenter study recruited 602 patients with standard indications for an implantable cardioverter-defibrillator. Programming was standardized into 3 zones: (1) ventricular fibrillation (VF) CL of <200 ms treated with HES; (2) VFVT defined within the VF zone (CL, 200 to 250 ms) treated with 2 ATP bursts, LES, and HES; and (3) fast ventricular tachycardia (CL, 251 to 320 ms) and slow VT (CL, >320 ms) treated with 3 ATP bursts, LES, and HES. The primary end point was ATP and LES efficacy and safety. After a mean follow-up of 19 ± 8 months, 2,815 device activations were recorded in 152 patients. Of 67 VFVT episodes, 34 reverted with combined ATP and LES (success rate 50.7%) with first and second ATPs successful in 36% and 13.8%, respectively. LES was used in 39 fast ventricular tachycardia and 60 slow VT episodes with success rates of 53.8% and 73.3%, respectively. Syncope occurred in 19.4%, 16.2%, and 1% of episodes because of VFVT, VF, and VT CL >250 ms, respectively. In conclusion, tiered ATP and LES therapy terminates >50% of VFVT episodes (CL, 200 to 250 ms), which otherwise would fall within the VF zone and be treated exclusively with HES. LES is efficacious and safe in patients with VT CL >250 ms with extremely low syncope rates. Limitation of ATP to a single burst in VFVT is recommended to minimize syncope.