A case of on inappropriate shock from subcutaneous implantable cardioverter defibrillator in a patient with implanted leadless pacemaker

The feasibility and safety of combined leadless pacemaker (LP) and subcutaneous implantable cardioverter defibrillator (S-ICD) therapy still have limited evidence.

We report a case of inappropriate shock as a result of interaction between these two devices, which was corrected by programming of S-ICD.

The 60-year-old male on intensive hemodialysis with ischemic cardiomyopathy and other multiple comorbidities in 2017 underwent S-ICD implantation (Emblem, Boston Scientific Corp, USA) for primary prevention. The MITRACLIP device was also successfully implanted.

The patient (pt) was admitted to our hospital in December 2019 with STEMI. A few days later the pt developed recurrent ventricular tachycardias which were successfully treated by S-ICD shocks. Intravenous amiodarone therapy provokes bradyarhythmias and the temporary pacemaker was inserted.

Next day the LP (Micra VR TCP, Medtronic Inc, USA) was successfully implanted on the right mid ventricular septum.

During preparation for defibrillation testing (DFT) the mode of LP pacing was changed to VOO 90 beat per minute (b/min). Following this programming, the pt experienced 2 DC shocks form S-ICD due to double counting of R and T on S-ICD interrogation, which was previously programmed for VT zone with treatment, starting form 180 b/min. Changing of the vector for R wave sensing on S-ICD restored correct counting of ventricular activity. DFT was successful.

Unfortunately, a week later the pt died after exacerbation of heart failure not responding to resuscitation. On LP interrogation there was a rising of pacing threshold (without loss of capture) during last 3 days with no changes in pacing impedance. On S-ICD interrogation appropriate DC shocks for recurrent episodes of ventricular fibrillation were found.

To conclude, in the era of novel devices, combined function of LP and S-ICD implanted in the same pt have to be well checked and correctly programmed, in terms of preventing inappropriate and potentially dangerous therapy.