Discussion
This case demonstrates potential Micra leadless PM induced ventricular fibrillation (VF) arrest in our patient. Despite extensive workup, the etiology of VF arrest in our patient remained unclear. Although local myocardial irritation from implantation of the Micra device as a trigger of VF is possible, it is unlikely given the difference in the morphology of the PVC that initiated VF vs. paced QRS complexes. Other case reports of ventricular arrhythmias following leadless PM device implantation have also been reported 9,10,11. Our case sheds further light on this complication by adding to the existing literature.
Current studies show the Micra leadless PM to have an acceptable safety profile, however reports of peri and post-operative ventricular arrhythmias have been described. Ritter et. al originally described the early performance of Micra and its safety profile in a prospective multisite study; among the cohort of 140 patients undergoing Micra implantation, 3 individuals developed ventricular arrhythmias that were not associated with death, re-operation or hospitalization12. In a retrospective Swiss study evaluating the safety and efficacy of Micra implantation in 92 patients, one patient developed unstable ventricular tachycardia during implantation; two months later, he was hospitalized again with intractable ventricular tachycardia requiring ablation. During the ablation, the VT was mapped to be originating from close to the insertion site of the device13. In contrast, early results from the Micra Post Approval Registry (PAR), an ongoing global prospective observational registry evaluating the safety and efficacy of Micra implantation, show that none of the 1801 patients who underwent the procedure developed ventricular arrhythmias 14.
Different mechanisms for the development of ventricular arrhythmias after Micra implantation have been proposed 9, 11, 12. Amin et. al reported a case of PVC-induced polymorphic ventricular tachycardia resulting in episodes of near-syncope and dizziness in a 74-year-old patient one day after Micra LP implantation. The PVCs were hypothesized to be secondary to local irritation of the right ventricular myocardium at the site of Micra implantation. Similarly, in the Swiss study, the unstable ventricular tachycardia was attributed to a pro-arrhythmic effect of the nitinol fixation tines13. Another report describing polymorphic VT post-Micra implantation hypothesized that local inflammation via cytokine mediated cardiac remodeling likely contributed to VT in their case 15. In contrast, Costa et. al described a case of cardiac arrest within hours following Micra implantation; the ventricular tachyarrhythmia occurred during ventricular pacing and not spontaneously, and pacing-related induction of ventricular fibrillation was considered a possibility11. Importantly, while some of these cases were managed conservatively, others have shown that retrieval of the LP results in resolution of the arrhythmias. In the case described by Amin et. al, the patient subsequently underwent a second Micra implantation with retrieval of the prior to alleviate symptoms9. A report by Olsen et. al describes cardiac arrest due to VF post-Micra implantation that only resolved after removal of the LP 10. Similarly, the case of recurrent hemodynamically unstable ventricular tachycardia from the Swiss study demonstrated that despite management with amiodarone, beta blockers, verapamil, lidocaine, and external defibrillation, the arrhythmia ultimately resolved after surgical explanation of the Micra device13. In contrast to these three reports, the case of polymorphic VT after Micra implantation was managed with intravenous steroids and overdrive pacing, resulting in resolution of repolarization abnormalities 15.
After Micra LP implantation patients can abruptly develop ventricular arrythmias leading to significant morbidity and mortality. Although literature is currently limited to case reports following the initial device performance data, we believe further large studies will help to illustrate this relationship. These adverse events highlight the importance of close monitoring of patients in the postoperative period to minimize complications with timely intervention. We propose that patients undergoing Micra implantation should be closely monitored for ventricular arrythmias in the early post-operative period.