Grant: Project Grant

Pacemakers are essential, life-saving devices for patients who develop very slow heart rates. If a patient is completely dependent on the pacemaker without electrical signals of their own, they can develop a weak heart muscle (heart failure). Up to 25% of patients will develop heart failure because they are completely dependent on the pacemaker. Once heart failure develops, patients have a reduced quality of life and they are much more likely to present to the hospital with water in their lungs and have a higher risk of dying. Instead of implanting a regular pacemaker for patients who present with extreme slowing of the heart, we hypothesize that through a new pacing strategy called "Left bundle branch pacing (LBBP)" we can prevent weakening of the heart by recreating the heart's natural electricity. LBBP uses the same simple pacemaker, but the lower (ventricular) wire is placed directly within the muscular wall separating the two ventricles, at a critical electrical region. In our study called "LEFT HF", we will compare two pacing strategies: A) Standard pacing (control group) where the bottom wire is placed in a standard location in the lower right chamber vs B) Left bundle branch pacing (LBBP) (experimental group). All patients presenting with severe electrical slowing ("heart block") requiring an urgent pacemaker will be candidates for the trial as long as their heart function is only mildly weakened at baseline. The patients will have usual follow-up in the pacemaker clinic and will have an ultrasound of the heart at 1, 2, and 3 years after pacemaker implant. We will compare the control and experimental patient groups to see whether LBBP will prevent weakening of the heart muscle, prevent hospitalizations for heart failure, and whether it will prevent death. Due to the expertise required to perform LBBP, only very experienced electrophysiologists across Canada have been selected to participate in the trial.