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 Right Bundle Branch Block (RBBB) through atrioventricular (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.
All patients will be implanted with a CRT (Cardiac Resynchronization Therapy) defibrillator with one of the leads positioned on the His bundle to obtain direct His-bundle capture. (There will be a 1-month run-in period where the output voltage will be 3.5 Volts/1 or 2V/1msec according to the group so as to obtain stable threshold).
A single-blinded design will then be employed to investigate the effect of His bundle pacing. Patients will be allocated in random order to six-month treatment periods in each of the following two states (1) 3.5 Volts/1 msec pacing output direct His-bundle pacing, AV delay will be programmed in order to obtain a PR interval of 120-140msec; (2)back up only pacing (pacemaker programmed to VVI 30 bpm or AAI(R-DDD(R) 60bpm). Endpoint measurements will be taken at baseline, 1 month run-in period of 3.5 Volts/1 msec or 2V/1msec pacing output and 6 months post randomization. Treating Physicians will be aware of assignment in order to facilitate routine device follow-up. Echocardiographic and electrocardiographic evaluation will be performed in a blinded manner. Treatment allocation will be blinded to the endpoint assessor and the patient.
Patients entering the study will attend for implantation of a CRT pacemaker device with one lead positioned on the His bundle. This will be performed in Miulli General Hospital (and other participating centres) no later than 2 months after the patient's screening visit.
Before the intervention patients will be randomized to either receive active pacing treatment with 3.5 V/1 msec or back up only pacing (pacemaker programmed to VVI 30 bpm or AAI(R)-DDD(R) 60) for 6 months. All patients will be implanted with an Implantable cardioverter defibrillator (ICD) and an ICD lead in the right ventricle (RV) (either RV apex or RV septum). In all patients a pacing lead will be positioned in the right atrium (typically the right atrial appendage). All patients will have a pacemaker lead positioned on the His bundle to obtain direct His-bundle capture.
After implantation of the device there will be a 1-month run-in period that the device will be programmed to deliver His bundle pacing therapy during this period at 3.5 Volts/1msec or 2V/1msec according to the assignment group.
One month after patients are implanted with their device, patients will either receive active pacing treatment with 3.5 V/1 msec or back up only pacing (pacemaker programmed to VVI 30 bpm or AAI(R)-DDD(R) 60bpm) for 6 months. Treatment allocation will be obtained using an Interactive Web Response System (IWRS) programmed with a randomization schedule provided by the trial statistician. Appropriate blocking will be used.
