Incidence and Determinants of Implantable Cardioverter-Defibrillator Therapy With Loss of and Impaired Consciousness.

INTRODUCTION Implantable cardioverter-defibrillators (ICDs) are important in the prevention of sudden cardiac death. However, some appropriate ICD therapies may be considered unnecessary, delivered when patients do not experience symptoms of hemodynamic instability such as loss of consciousness. Therefore, we aimed to determine the incidence of appropriate ICD therapy with loss of consciousness and impaired consciousness, as well as the psychological impact following any ICD therapy, in patients with an ICD by investigating patient-reported symptoms.

METHODS In this prospective, single-center study conducted at the University Medical Center Groningen (UMCG), 100 consecutive patients with an ICD for primary or secondary prevention indications who received ICD shock and/or ATP within the previous 6 months completed a questionnaire. The primary outcome was appropriate ICD therapy with loss of consciousness.

RESULTS The patient population consisted of 100 patients, 92 (92.0%) of whom had appropriate therapy. The mean age was 62.7 ± 12.8 years and 21 (21.0%) were female. Loss of consciousness occurred in 40% of patients with appropriate ICD therapy and in 65% of patients with appropriate shocks. Determinants of appropriate ICD therapy with loss of consciousness included the shortest cycle length, ventricular fibrillation, the occurrence of shock, a secondary prevention indication for ICD, the presence of a CRT-D and the fragmentation and width of the QRS complex. The psychological impact of ICD shocks was considerable, with patients without loss of consciousness during ICD shocks suffering significantly more from anxiety than those with loss of consciousness (9 (60.0%) versus 12 (42.9%), p = 0.041).

CONCLUSIONS A considerable number of patients do not experience appropriate ICD therapy with loss of consciousness and thus experience potentially unnecessary therapy while still being at risk of sustaining the consequent psychological impact associated with ICD shocks.