P406
Potential local inflammation in individuals implanted with a leadless pacemaker systems: an experimental in vitro study

Background: Leadless pacemaker technology is a promising upcoming field in clinical rhythmology. Currently, there are two different available products. Currently, the most commonly used system in the clinical setting is the Micra system (Medtronic).

According to the companies, the devices are usually expecting to remain floating within the right ventricle, while fixation to the myocardium is achieved by the use of tines.

In both devices, an unexpected ingrowth/encapsulation within the wall of the right ventricle was reported, which could be found during autopsies in some patients that witnessed non pacemaker associated death.

Even though technical parameters of these pacemakers remained stable during follow-ups, the occurrence of a complete encapsulation was not expected and the processes of endothelialisation remained unclear. We hypothesized that a local inflammatory response might be the cause of these findings and could eventually be measurable.

The aim of our study was to investigate the effect of the Micra system and its material composition on the immune system and whether inflammatory processes take place in vitro.

Methods: For this purpose, whole Micra pacemakers were incubated in 9 ml heparin plasma from 25 healthy volunteers for 48 h at 37°C and 5% CO2. Furthermore, 0.5 g gold, steel, titanium and tungsten wires were incubated in 9 ml heparin plasma for 48h at 37°C and 5% CO2 as well (n=10).

To detect eventual inflammatory processes, the cytokines of systemic inflammation interleukin- (IL) 1β, IL-6, and tumor necrosis factor alpha (TNF-α), the chemokine IL-8 were measured using enzyme-linked immunosorbent assay (ELISA). Additionally, the level of transforming growth factor beta 1 (TGF-β1) and vascular endothelial growth factor (VEGF) were analysed.

Results: ELISA analyses showed that the whole Micra system leads to a significant increase of the inflammatory cytokine IL-6 which correlates with the data gained by the incubation of whole blood with the different wires. In particular, 0.5 g of tungsten showed a significant rise of IL-6 which was also found for IL-1β and IL-8. The other wires only had a marginal effect on the different cytokines and chemokines, although gold also slightly increased the level of IL-1β.

Conclusions: The in vitro study of the Micra system showed that the material composition of Micra led to an onset of inflammatory processes in whole blood through the increase of IL-6, IL-1β and IL-8. Consequently, through these findings one may speculate that the composition of Micra pacemaker may have an inflammatory effect on patients with Micra implants.