Pacing Affects Cardiovascular Endpoints in Patients With Right Bundle-Branch Block (The PACE-RBBB Trial) (PACE-RBBB)

Pacing Affects Cardiovascular Endpoints in Patients With Right Bundle-Branch Block (The PACE-RBBB Trial)

Pacing Affects Cardiovascular Endpoints in Patients With Right Bundle-Branch Block (The PACE-RBBB Trial)

Heart failure (HF) affects 5 million Americans and is responsible for more health-care expenditure than any other medical diagnosis. Approximately half of all HF patients have electrocardiographic prolongation of the QRS interval and ventricular dyssynchrony, a perturbation of the normal pattern of ventricular contraction that reduces the efficiency of ventricular work. Ventricular dyssynchrony is directly responsible for worsening HF symptomatology in this subset of patients. Resynchronization of ventricular contraction is usually achieved through simultaneous pacing of the left and right ventricles using a biventricular (BiV) pacemaker or implantable cardioverter-defibrillator. Clinical trial evidence supporting the use of BiV pacing in patients with prolonged QRS duration was obtained almost exclusively in patients with a left bundle-branch block (LBBB) electrocardiographic pattern. Recent evidence suggests that resynchronization of ventricular contraction in patients with LBBB can be obtained by univentricular left ventricular pacing with equal or superior clinical benefits compared to BiV pacing. Animal studies suggest that ventricular resynchronization can be obtained in subjects with right bundle-branch block (RBBB) through univentricular right ventricular pacing. No clinical trial evidence exists to support the use of BiV pacing in patients with RBBB. Thousands of patients with symptomatic HF and RBBB currently have univentricular ICDs in place for the prevention of sudden cardiac death. Most of these devices are currently programmed to avoid RV pacing. We aim to determine if ventricular resynchronization delivered through univentricular RV pacing improves symptoms in patients with RBBB and moderate to severe HF who have previously undergone BiV ICD implantation for symptomatic heart failure. We further aim to determine if ventricular resynchronization improves myocardial performance and ventricular geometry as detected by echocardiographic measures and quality of life for patients with HF and RBBB. We hypothesize that RV univentricular pacing delivered with an atrio-ventricular interval that maximizes ventricular synchrony is equivalent to BiV pacing for improvement in cardiac performance, HF symptoms, and positive ventricular remodeling in patients with HF and RBBB.

Period 1: Participants assigned to VVI-40 Participants will then Crossover to Period 2. Period 2: Participants assigned to RV DDD-40 Participants will then Crossover to Period 3. Period 3: Participants assigned to Bi-V DDD-40

Period 1: Participants assigned to VVI-40 Participants will then Crossover to Period 2. Period 2: Participants assigned to Bi-V DDD-40 Participants will then Crossover to Period 3. Period 3: Participants assigned to RV DDD-40

Period 1: Participants assigned to Bi-V DDD-40 Participants will then Crossover to Period 2. Period 2: Participants assigned to VVI-40 Participants will then Crossover to Period 3. Period 3: Participants assigned to RV DDD-40

Period 1: Participants assigned to Bi-V DDD-40 Participants will then Crossover to Period 2. Period 2: Participants assigned to RV DDD-40 Participants will then Crossover to Period 3. Period 3: Participants assigned to VVI-40

Period 1: Participants assigned to RV DDD-40 Participants will then Crossover to Period 2. Period 2: Participants assigned to VVI-40 Participants will then Crossover to Period 3. Period 3: Participants assigned to Bi-V DDD-40

Period 1: Participants assigned to RV DDD-40 Participants will then Crossover to Period 2. Period 2: Participants assigned to Bi-V DDD-40 Participants will then Crossover to Period 3. Period 3: Participants assigned to VVI-40

The Primary Endpoint of the Trial Will be a Comparison of the Proportion of Patients in Each of the Three Treatment Groups Who Demonstrate Positive LV Remodeling, Defined as a Decrease in LV End Systolic Diameter of >5mm.

Comparisons of the derived velocity-time integral calculated on the aortic continuous wave Doppler-spectrogram, RV end-diastolic size, RV EF, mitral and tricuspid regurgitation severity, and estimated RV systolic pressure.

To determine if pacing mode impacts the frequency of ventricular arrhythmias, the incidence of ventricular tachyarrhythmia episodes on device interrogation will be compared between treatment group assignments. An episode will be considered ventricular arrhythmia if it lasts longer than 30 seconds or requires anti-tachycardia pacing or high voltage device therapy for termination.

This is a standardized method for assessing quality of life in patients with heart failure. It asks 21 questions and measures the impact HF has on a subject's life. Each question is rated 0-5. The total score for the 21 items can range from 0 to 105. Higher scores indicate more burden of disease on quality of life.

The New York Heart Association (NYHA) Functional Classification places patients in one of four categories based on how much they are limited during physical activity. Class I means there is no limitation of physical activity and Class IV means a person is unable to carry on any physical activity without discomfort/symptoms of heart failure at rest.

Inclusion Criteria: Cardiomyopathy of either idiopathic or ischemic etiology NYHA class III, or IV symptoms Sinus rhythm QRS complex duration > 130 msec in ≥ 2 surface ECG leads with RBBB PR interval > 150 msec and < 240 msec Prior implantation of dual chamber BiV ICD with apical RV lead location Exclusion Criteria: Myocardial infarction, major surgical procedure, or acute cardiac failure crisis requiring inotropes within 6 months of entry into the study Atrial fibrillation or flutter lasting >12 hours within the last 6 months Sick sinus syndrome, complete heart block, or other arrhythmias requiring pacemaker support Pregnancy Any other known condition other than heart failure that could limit exercise time or survival to < 6 months