[Heart rhythm after conversion of ventricular tachyarrhythmia by internal shock delivery]

The purpose of this retrospective study is the analysis of dysrhythmias following internal cardioversion/defibrillation of ventricular tachycardia (VT) or fibrillation (VF) and to discuss their relevance to the therapy with automatic implantable devices. Therefore, 304 internal conversions of VT/VF during and/or after implantation of automatic defibrillators were evaluated in 51 patients. Significant post-shock arrhythmias (bradycardia, atrial fibrillation, non-sustained VT of > or = 10 cycles) were absent after 89% of internal shocks. Pauses of > 2 s were observed in 2/9 patients without VVI-back-up pacing. The heart rate was > or = 50 bpm in 10/51 patients. Atrial fibrillation occurred in 7 patients. Non-sustained, mostly polymorphic VT consisting of > or = 10 cycles followed 18/304 (6%) internal shocks in 13 patients. The VT rate was > or = 200/min in 17/18 episodes and triggered an inadequate shock once. The incidence of non-sustained VT post-shock was unrelated to shock energy, type, and duration of the converted arrhythmia. In conclusion, automatic implantable devices should provide back-up pacing. Tachycardic rhythms can mislead automatic interpretation of the effect of internal shocks.