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.