[Predictors for need of antibradycardia and antitachycardia pacing after ICD implantation : Implications for the subcutaneous ICD].

Background: Little is known about the incidence and risk factors for progression to pacemaker dependency or the need for cardiac resynchronization in typical patients with an implanted defibrillator with regard to an alternative implantation of a subcutaneous ICD (S-ICD).

Study Design And Methods: After retrospective analysis of 291 patients with first implantation of a transvenous single chamber ICD (VVI-ICD) from 2010-2016 and excluding those with an indication for pacemaker or lack of follow-up data, 121 patients were included and investigated with regard to the following endpoints: need for pacemaker stimulation, upgrade for cardiac resynchronization (CRT), and secondary occurrence and effectiveness of antitachycardia pacing (ATP). We compared the results with those of fundamental S‑ICD studies and tried to determine risk factors on the basis of medical history and pre-implant data.

Results: The study population and the rate of endpoints were significantly different to those of fundamental S‑ICD studies. Within a 2.2-year follow-up, 14.9 % of the patients developed a need for pacemaker stimulation and 0.8 % the need for cardiac resynchronization. Excluding patients who at implantation were already at high risk for pacemaker dependency, 7.4 % remained with a reached endpoint. We identified atrial fibrillation and bundle-branch-block as risk factors. All episodes of ventricular tachycardia (VT) could be terminated by ATP in 9.9 % of the patients. They more often had ischemic heart disease and a secondary prophylactic indication for an ICD.

Conclusion: The low rate of conversions from S‑ICD to a transvenous ICD in case of pacemaker-dependency as stated in fundamental S‑ICD studies should not be transferred to other typical collectives of ICD recipients. The latter group is at significantly higher risk for developing pacemaker-dependency.