T wave over sensing causing inappropriate shock and ventricular fibrillation in a subcutaneous ICD recipient

Document Type

Conference Proceeding

Publication Date


Publication Title

J Interv Card Electrophysiol


Background: T wave over sensing (TWOS) is a known phenomenon with trans-venous and subcutaneous ICDsystems and various algorithms exist to mitigate TWOS. Objective: To describe importance of proper lead positioning in a subcutaneous ICD system and harmful results of inappropriate shocks Methods: N/A Results: A 73 year old male with hypertension, preserved left ventricularfunction, idiopathic pulmonary fbrosis and obesity (BMI 34.2) was transferred to our institution for multiple ICDshocks (13) over a period of 2 hours on amiodarone and procainamide infusions Patient has previously underwent asubcutaneous ICD implantation (2-incision technique) for sustained monomorphic VT (SMVT) programmed with primary vector for sensing. ICD interrogation showed multiple appropriate shocks for SMVT (Figure A) and inappropriate shocks for TWOS with one of the shock on Twave resulting in sustained ventricular fbrillation with successful termination by shock (Figure B). CXR showed signifcant displacement of ICD lead into the left lateral chest wall (Figure C). EP study revealed a spontaneous SMVT which was not inducible with programmed electrical stimulation and a HV interval of 82 ms. Subcutaneous ICDwas extracted and a trans-venous dual chamber ICD was implanted. Patient has remained arrhythmia free on beta-blocker therapy. Conclusion: Inappropriate shocks insubcutaneous ICD recipients could be due to lead malpositioning thus calling for strict attention to details during lead implantation and need for post implant imaging surveillance. Inappropriate shock on T wave can lead to life threatening arrhythmias [Image Presented].





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