This study will examine the clinical feasibility of His pacing in patients with expected high demand for ventricular pacing and no established indication for cardiac resynchronization therapy. Secondarily, examine differences in electrical and mechanical cardiac activation between traditional pacing and His pacing.

After being informed about the study and potential risks, all eligible patients giving written consent will be included. The study is a clinical single-center interventional study. The patients (n = 25) need to have an expected high demand for ventricular pacing and no established class I indication for cardiac resynchronization therapy. They will receive a pacemaker implant with a traditional right ventricular pacing lead and an additional His pacing lead in a basal high septal position at the level of the proximal electrical conduction system (His). An atrial lead is implanted if dual chamber pacing is needed. All leads are connected to a biventricular pacemaker with the His lead in the LV port. Postoperatively, the baseline examinations will include: transthoracic echocardiography, 12-lead ECG with a 3D photography of the chest wall to document ECG electrode location, and a contrast-enhanced cardiac CT scan. The echocardiography and ECG will be performed during traditional right ventricular pacing only and His pacing only. His pacing will be used as the permanent programming of choice if feasible during follow up. The CT scan is used for documenting the final positions of the pacing leads and to create a patient-specific 3D model of the cardiac electrical activation using a software which enables merging of a CT scan and ECG and a CT chest photography. During follow up (1-3 and 12 months), transthoracic echocardiography, 12-lead ECG and 3D chest photography are repeated for assessment of mechanical and electrical function during pacing. The performance of all implanted pacing lead will be evaluated at each follow up visit.

Inclusion Criteria:

• Permanent pacemaker indication with expected high demand of right ventricular pacing (>40%) and left ventricular ejection fraction >40%.

Exclusion Criteria:

• No class I indication for CRT pacemaker (HRS 2018 Pacing Guidelines)
• Hemodynamically unstable patients
• Severely reduced kidney function
• Former serious adverse reactions to contrast media
• Pregnant or lactating
• Severe psychiatric disorder which can compromise compliance with protocol