Comparison of Defibrillation Efficacy and Survival Associated With Right Versus Left Pectoral Placement for Implantable Defibrillators

The preferred location for an implantable cardioverter-defibrillator (ICD) generator is the left pectoral region as a result of the shock vector formed by the active can and the lead system. However, a right pectoral site is necessary when left-sided implantation is contraindicated. The Low Energy Safety Study was a prospective, randomized trial conducted to assess chronic defibrillation efficacy in 627 patients, including 37 (5.9%) who received right pectoral implants and 590 (94.1%) who received left pectoral implants. Patients were followed for a mean of 24 ± 13 months. There were no significant differences observed between patients who received left versus right pectoral implants in age, gender, indications, New York Heart Association classification, or ejection fraction. Patients who received a right pectoral implant had higher defibrillation thresholds at implantation (10.6 ± 3.8 J) than those who received a left pectoral implant (8.9 ± 4.2 J, p = 0.01) despite similar shock impedances. The conversion efficacy for spontaneous arrhythmia episodes among patients who received right and left pectoral implants were not significantly different (33 of 33 [100%] vs 255 of 263 [97%], respectively; p = 0.31). In addition, the conversion efficacy for induced ventricular fibrillation episodes were also similar (187 of 188 [99%] on the right vs 2429 of 2475 [98%] on the left, p = 0.18). However, the all-cause mortality rate was higher for patients who received right-sided implants (hazard ratio 1.93, p <0.004). In conclusion, defibrillation thresholds are higher with right pectoral implants compared with left-sided implants, but with a proper energy safety margin, there are no significant differences in spontaneous or induced shock conversion efficacy. However, the near doubling of the mortality rate among patients with right-sided implants needs to be considered when recommending such device therapy.