His Bundle Pacing

The investigators aim to prospectively evaluate the efficacy and mechanism of benefit of His-bundle pacing enhanced cardiac resynchronization therapy (His-CRT) vs. cardiac resynchronization therapy (BIV-CRT) in patients with heart failure and right bundle branch block (RBBB).

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, and estimates suggest its prevalence is increasing. Despite the advances in AF ablation strategies, the outcome of ablation procedures in persistent AF is still unsatisfactory. In addition, many patients are not candidates for ablation due to advanced age, comorbidities and previous failed ablation procedures. It is well known that there is no mortality benefit from rhythm versus rate control strategy in AF, therefore the increased number of AV node ablation and pacemaker insertion for patients with symptomatic AF with uncontrolled heart rate. Following AV node ablation, it is understandable that these patients will be paced 100% of the time where the value of physiological pacing will be at its most. The current standard practice is to pace the right ventricle for this cohort of patients unless they have severe LV systolic dysfunction when a biventricular pacing might be recommended. Previous data showed that RV pacing only can lead to deterioration of LV function, worsening of heart failure symptoms and increased mortality. HIS bundle pacing is a novel technique of pacing through placing the pacemaker lead on the junction box between the top and bottom chamber of the heart. This will allow the utilisation of the normal/intrinsic HIS Purkinjie (eclectic cables) to stimulate the ventricles. This can offer a physiological pacing modality and reduce pacing induced cardiomyopathy specially in pacing dependent pacing. The Ablate and Pace HIS Study proposes that the new method of HIS pacing is safe, effective and superior to the existing method of RV pacing in patients with atrial fibrillation who demonstrate signs of heart failure.

Cardiac Resynchronization Therapy (CRT) decreases heart failure hospitalizations and mortality and increases left ventricular Ejection Fraction (EF) in patients with dilated cardiomyopathy, left bundle branch block and QRS duration \>130msec. His bundle pacing has a similar effect in this category of patients. However, CRT is not beneficial in heart failure (HF) patients with narrow QRS. His-bundle pacing delivers physiological ventricular activation and has been shown to improve acute hemodynamic function in patients with heart failure, a prolonged PR interval, and either a narrow QRS or RBBB through AV delay optimization. We observed an acute hemodynamic effect during application of higher pacing output (3.5 Volts/1 msec) in HF patients with dilated or ischemic cardiomyopathy and narrow QRS independently of the paced QRS duration or AV delay shortening. This is a single-center, prospective randomized single-blinded study, recruiting a sub-population of patients with heart failure (dilated or ischemic cardiomyopathy, EF\<50%, narrow QRS (\<110 msec), in optimal medical treatment who have an indication for ICD.

The PROTECT-HF multi-centre randomised controlled trial will compare two different pacing approaches for treating patients with slow heart rates. In it the investigators will compare a long-standing standard approach for pacing; right ventricular pacing, with a new form of pacing, physiological pacing (His and Left bundle area pacing) in 2600 patients. Patients will be allocated at random to receive either right ventricular pacing or physiological pacing. Endpoint measurements will be undertaken at baseline, and at six-monthly intervals post-randomisation. Treatment allocation will be blinded to the endpoint assessor and the patient. Recruitment and pacemaker implantation will be carried out at each participating centre. The primary analysis will be intention to treat. The investigators will also perform an on-treatment analysis. 2048 patients are needed to detect the expected effect size with 85% power. A total of 2600 patients will be recruited to allow for patient drop-out and crossover. 500-patient sub-study will assess within patient, and between groups, echocardiographic changes over a 24-month period to try and improve mechanistic understanding of PICM (Pacing Induced Cardiomyopathy).

Right ventricular pacing causes ventricular dyssynchrony and may be associated with impaired outcome. In the last decade, several approaches for more physiological pacing became available and were implemented in the latest guidelines. However, compared to conventional device implantation, cardiac resynchronization, His bundle pacing and left bundle area pacing remain demanding procedures in the individual case. Goal of the single center observational "Pace conduct" study is to evaluate implantation success, safety and outcome of pacing methods that maintain physiologic ventricular activation.