PACEMAKER/ICD PROBLEM OF THE MONTH Postshock AAI pacing associated with asystole despite programming postshock DDD pacing

a c b m v Introduction We describe a case of asystole following an induced implantable cardioverter-defibrillator (ICD) shock, despite having programmed postshock pacing in the DDD mode. The patient, a 41-year-old woman with long QT syndrome 1 and a markedly prolonged corrected QT interval after exercise, whose daughter (the proband) survived an out-ofhospital cardiac arrest, underwent insertion of a dual-chamber ICD. The base rate was programmed to AAI 70 beats/ min with postshock pacing at DDD 70 beats/min. However, despite having programmed postshock DDD pacing, AAI pacing with asystole occurred after the shock. The mechanism for this unexpected and apparently incongruous behavior is explained.