Inappropriate discharge of an implantable cardioverter defibrillator during atrial flutter and intermittent ventricular antibradycardia pacing

Short-long-short sequence caused by ventricular safety pacing inducing ventricular tachycardia in a patient with a dual-chamber implantable cardioverter defibrillator

Ventricular safety pacing (VSP) is an algorithm used to prevent crosstalk inhibition and ventricular capture during the vulnerable period. We report a 78-year-old man with implantable dual-chamber defibrillator, in whom clusters of ventricular tachycardias (VTs) were provoked by the VSP. During rapid DDDR pacing, the delivery of the VSP after every other atrial-paced beat resulted in short-long-short ventricular sequences and induced VTs. An atrial-based lower rate timing, long atrioventricular pacing interval, and automatic gain control also accounted for this arrhythmogenic ventricular sequence. The VSP and the subsequent VT were eliminated by decreasing the pacing rate.

Myopotential sensing by a dual chamber implantable cardioverter defibrillator: two case reports

INTRODUCTION

Inappropriate discharges and/or improper inhibition of bradycardia pacing due to oversensing of extraneous signals in implantable cardioverter defibrillators (ICDs) have been described. With one exception, no previous report involving an intact lead system has cited myopotential oversensing as the cause.

METHODS AND RESULTS

Two case reports of myopotential oversensing by a dual chamber ICD system are reported. In the first patient suffering from chronic pulmonary obstructive disease, intermittent myopotential sensing during labored respiration resulted in episodic inhibition of bradycardia pacing. In the second patient, oversensing of sustained myopotentials generated during strenuous isometric activity resulted in an inappropriate ICD discharge. For both, the ICD system consisted of a CPI model 1810 Ventak AV used in conjunction with a model 0125 Endotak lead, incorporating integrated bipolar sensing.

CONCLUSION

Although modern ICDs have proven to be highly effective in detecting and terminating malignant tachyarrhythmias, the opportunity for improving their detection specificity remains.