Comparing the Effects of Newer Pacemakers and Their Effects on the Heart and Valve Function in the Short-term.

Conventional pacemakers involve placing a lead through a valve into the bottom right chamber of the heart. Research has shown that this approach is associated with an increased risk of valve dysfunction, mortality, and impairment of cardiac function. Newer pacemakers, such as leadless pacemakers and pacemakers that engage directly with the heart's native conduction system (known as left bundle branch pacemakers), are increasingly being adopted. However, the impact of these newer pacing technologies on cardiac function and the tricuspid valve, as well as how they compare with each other, remains unclear. The investigators aim to study the impact of leadless pacemakers and left bundle branch pacemakers on cardiac function and the tricuspid valve by conducting an acute study in addition to the routine pacemaker implantation procedure for which participants have been referred. Both procedures will be performed during a single session under general anaesthesia. Outcomes from this study will improve understanding of how these pacing technologies affect cardiac and valvular function and how they compare with each other. These findings will help guide decision-making regarding the optimal type of pacemaker to adopt, particularly for patients at greatest risk of developing tricuspid valve dysfunction or impaired cardiac function.

Inclusion Criteria: * All patients aged ≥18 referred for a permanent pacemaker at a single centre (Guys and St. Thomas' NHS Foundation Trust, UK) with high degree AV block, including Mobitz II and complete heart block, or scheduled AV node ablation, and LVEF ≥50%. Exclusion Criteria: * LVEF \