The question of whether repeated transcatheter leadless pacemaker implantation and retrieval leads to an increased incidence of tricuspid valve regurgitation (TR) or other valvular dysfunction compared to initial implantation is complex, and the current scientific understanding is still evolving.

Here's a breakdown of what the literature suggests:

Initial Implantation and Valvular Dysfunction:

• Leadless vs. Conventional: While conventional transvenous pacemakers are known to cause or worsen TR due to the leads interfering with valve leaflets, leadless pacemakers (LPs) were theoretically designed to avoid this by not having transvalvular leads.
• Initial LP Implantation and TR: Despite the theoretical advantage, studies have shown that even initial LP implantation can be associated with new or worsening TR in a significant percentage of patients. Some studies report an increase in TR in 43% of patients at 12 months, with similar rates to those seen with dual-chamber transvenous pacemakers.¹
   
• Mechanisms of TR with LPs:
  • Mechanical Interference: LPs, particularly if implanted in a more septal position, can still interfere with the tricuspid valve leaflets, chordae tendineae, or papillary muscles.² This can lead to impaired leaflet mobility and insufficient coaptation, resulting in TR.
     
  • Delivery System Injury: The large delivery system used for LP implantation can directly injure the valve or subvalvular apparatus, especially if multiple attempts are needed for device deployment or recapture.
  • RV Pacing-Induced Dyssynchrony: Right ventricular (RV) pacing, whether from a leadless or conventional device, can lead to ventricular dyssynchrony, which can in turn contribute to TR and other valvular dysfunction.

Impact of Retrieval on Valvular Dysfunction:

• Fibrous Encapsulation: Over time, leadless pacemakers can become integrated into the myocardial tissue through fibrous encapsulation.³ This integration can make retrieval more challenging.
   
• Removal Risks: While specialized tools and techniques have been developed for LP removal, there are still potential complications.⁴ Damage to the tricuspid valve or subvalvular apparatus during retrieval is a known, though uncommon, risk. Case reports exist of severe TR necessitating surgical intervention after LP removal due to complications like leaflet flail or papillary muscle avulsion.
   
• Limited Data on Repeated Procedures: The long-term data specifically on the impact of repeated LP implantation and retrieval on valvular dysfunction is still somewhat limited. Most studies focus on initial implantation complications or single retrieval events.
• Lead Dwell Time and Extraction Risks: Studies on conventional lead extraction suggest that longer lead implant durations are associated with an increased risk of tricuspid valve injury and acute TR increase.⁵ This suggests that repeated procedures over years, which would involve longer dwell times for devices, could theoretically increase the cumulative risk of valvular damage during removal.
   

Conclusion:

While leadless pacemakers aim to mitigate lead-related complications, they are not entirely free from the risk of tricuspid valve dysfunction, even upon initial implantation.⁶ The concern for repeated transcatheter implantation and retrieval exacerbating TR or causing other valvular damage is a valid scientific question. The potential for fibrous encapsulation over two years and the mechanical stresses of removal could theoretically increase the risk of valvular injury compared to a single, initial implantation. However, more extensive and long-term studies are needed to definitively quantify the cumulative incidence and severity of valvular dysfunction with repeated LP procedures.