The aims are to compare Direct His Bundle Pacing (DHBP) with biventricular pacing (BiV) in terms of electrical resynchronization using electrocardiographic imaging (ECGI) and also in terms of acute hemodynamical effect using finger plethysmography and conduction velocimetry. The study will be a randomized crossover design with acute measurements.

By recruiting native conducting tissue to relay electrical activation of the ventricles via the Purkinje fibre network, DHBP may potentially achieve greater electrical resynchronization and hemodynamic benefit compared to BiV where the electrical activation wavefronts propagate from two discrete pacing sites. Electrical synchrony achieved by these pacing modes have however never been compared. Furthermore, the acute hemodynamic effect of DHBP has been compared to BiV only in a small single study to date. The aims are to compare DHBP with BiV in terms of electrical resynchronization using electrocardiographic imaging (ECGI) and also in terms of acute hemodynamical effect using finger plethysmography and conduction velocimetry. The primary endpoint will be left ventricular activation time, with secondary endpoints including various electrical (right ventricular activation time, total ventricular activation time etc) and hemodynamic parameters (systolic pressure, cardiac output, cardiac contractility). It is expected that DHBP offers shorter left ventricular activation time (i.e. better synchrony) and hemodynamic benefit compared to BiV.

Inclusion Criteria:

• Treatment of heart failure with a standard indication for CRT (NYHA III-IV, LVEF < 35% and QRS > 130ms; or LVEF< 40% and requirement for frequent ventricular pacing, irrespective of baseline QRS duration) and optimal medical treatment.

  • Permanent atrial fibrillation (allowing connection of the DHBP lead to the atrial port).
  • Patients implanted with 1) a CRT pacemaker or CRT defibrillator 2) a His lead with selective or non-selective DHBP, connected to the atrial port of the generator 3) a functional right ventricular lead and 4) a functional coronary sinus lead.
  • DHBP with selective or non-selective His capture

Exclusion Criteria:

• Age <18 years
• Pregnancy
• Inability to undergo CT or an MRI (e.g. due to severe claustrophobia)
• Inability or refusal to sign the patient informed consent form.