INTERFERENCE OF IMPLANTED PACEMAKER AND CARDIOVERTER-DEFIBRILLATOR, LEADING TO REPETITIVE ICD SHOCKS AND NON-EFFECTIVE PACING THROUGH PM WITH ASYSTOLY AFTER SHOCKS

Theory: In patients with pacemaker (PM) and cardioverter-defibrillator (ICD) implanted later, an interference of both devices can occur.
Case study: 73 year old man with implanted PM (Jan 2005, St. Jude Medical – SJM Verity ADx XL SR VVI,R due to atrial fibrillation with complete AV block) received ICD SJM Atlas+ VR in Jan 2006 for syncope, nonsustained ventricular tachycardia and inducible malign arrhythmia (contralateral implantation). PM programmed for antibradycardia pacing and ICD programmed for antitachycardia therapy only.
Patient admitted to regional hospital in Jun 2006 for repetitive syncope and ICD shocks. Transferred to our center for arrhythmic storm suspicion. ECG shows pacing in frequency of 87ppm (AutoCapture and Sensor set to ON) and couples of stimuli (first one noneffective and second one back-up pace, 4.5 V 0.4 ms, intermit. noneffective). Pacing threshold of PM was 4.5V 0.4ms. Marker channel of ICD shows occurring of doublecounting of first stimulus and following sensed QRS after 125ms. After 25s the criterion for detection of ventricular fibrillation (VF) was fulfilled and shock emitted. After ICD shock the pacing threshold of PM increases temporarily leading to 7s asystoly due to non-effective pacing. ICD was inhibited by PM stimuli. During 11 days before admission the detection of VF occurred 42times causing 24 shocks. The situation was resolved by programming PM being permanently inhibited (VVI, 30ppm, output 0.75V at 0.05ms, sensitivity 0.5mV) and programming ICD for antibradycardia pacing with sufficient output.
Conclusion: In patients (pts) with coexisting PM and ICD, activity of both is risky since possible interference. In case of ICD implantation in pts with PM, it is feasible to consider PM explantation despite of underusing full PM longevity and saving of ICD generator in PM dependent pts. MSMT-MSM 0021622402