AV Delay Optimization vs. Intrinsic Conduction in Pacemaker Patients With Long PR Intervals

Study Overview
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Brief Summary
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This is a randomized, prospective clinical trial to determine the effects of two different pacemaker atrioventricular delay (AV delay) settings on heart function in patients with dual chamber pacemakers implanted for symptomatic bradycardia with long PR intervals (delayed conduction between upper and lower chambers of the heart). The study will compare a long, fixed AV delay (standard) with an optimized AV delay for each individual using echocardiography (experimental).

Detailed Description
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Cardiac pacing is the only effective treatment for symptomatic sinus node dysfunction. Most patients with preserved left ventricular function receive dual chamber pacemakers; however, right ventricular pacing can have detrimental effects on left ventricular function due to the abnormal electrical and mechanical activation pattern of the ventricles. Many patients receiving dual chamber pacemakers for symptomatic bradycardia have prolonged intrinsic AV conduction (first degree AV block), and as a result, will receive a significant amount of ventricular pacing if programmed at physiologic AV intervals. As an alternative, many pacemakers can be programmed to minimize ventricular pacing at the expense of allowing longer AV delays. However, these long AV delays may not be physiologic and may also lead to reduced cardiac output. At present the standard of care is either to program the pacemaker at an physiologic natural AV delay of about 160 msec or to program the pacemaker with a long AV delay to minimize ventricular pacing. The main scientific questions being addressed in this study are to evaluate the acute and chronic effects on cardiac output, functional status, sense of well-being, and cardiac remodeling of a long AV delay allowing for intrinsic conduction as compared to an echocardiographically optimized AV delay during dual chamber pacing. Patients enrolled in the trial will complete a run-in period of two weeks prior to randomization in which pacemakers will be programmed with a long-fixed AV delay to allow intrinsic conduction and minimize ventricular pacing (standard). At two weeks, patients will receive a baseline echocardiogram. To determine optimal AV delay, all patients will undergo echocardiographic analysis at varying AV delays. Optimal AV delay will be defined as the AV delay associated with the largest average aortic Doppler velocity time integral (VTI). Then, patients will be randomized to either the short, optimized (experimental) or long, fixed (standard) AV delay groups. To assess functional status and sense of well-being, patients will complete a six minute walk test and Short Form-36 Medical Outcomes Study Questionnaire. Patients return to clinic for another study visit at 6 months and repeat research procedures, including baseline echocardiogram, questionnaire, and 6 minute walk test.

Official Title
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Evaluation of AV Delay Optimization vs. Intrinsic Conduction in Patients With Long PR Intervals Receiving Dual Chamber Pacemakers for Symptomatic Bradycardia

Conditions
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Symptomatic Bradycardia, Atrioventricular Block, Sick Sinus Syndrome, Cardiac Arrhythmia

Intervention / Treatment
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* Device: Long, fixed AV delay
* Device: Short, optimized AV delay


Participation Criteria
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Eligibility Criteria
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Patient population: Individuals with 1st degree atrioventricular (AV) block who have received a dual chamber pacemaker for symptomatic bradycardia. Inclusion Criteria: Patients greater than 18 years of age Patients with symptomatic sinus bradycardia Patients who meet standard indications for dual chamber pacemaker implantation Patients who have 1st degree AV block determined by PR interval > 200ms Exclusion Criteria: Patients with complete or high grade AV block Patients who are unable to complete dual chamber pacemaker implantation for any reason Patients with congestive heart failure determined by a Left Ventricular Ejection Fraction < 45% Patients with persistent atrial fibrillation Sustained premature ventricular contractions (PVCs), premature atrial contractions (PACs), atrial flutter, or other heart conditions that may interfere with echocardiography measurements Patients who are pregnant Patients with Paroxysmal Atrial Fibrillation that have had an episode(s) within 30 days of consent

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Long, fixed AV delay<br>Pacemaker will be set to a long, fixed AV delay to minimize ventricular pacing | Device: Long, fixed AV delay<br>* Pacemaker will be set to a long, fixed AV delay to minimize ventricular pacing<br>|
| Experimental: Short, optimized AV delay<br>Pacemaker will be set to the AV delay that produces the greatest cardiac output in echocardiography for each patient enrolled | Device: Short, optimized AV delay<br>* Pacemaker will be set to the AV delay that produces the greatest cardiac output in echocardiography for each patient enrolled.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in cardiac output determined by echocardiography |  | 6 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in functional status determined by 6 minute walk. | Measure distance walked in 6 minutes in meters. | 6 months | 
| Changes in sense of well being as determined by Short Form - 36 Medical Outcomes Study Questionnaire | Sense of well being score determined by answers to questions on Short Form - 36 questionnaire. | 6 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Atrioventricular delay, AV delay, Pacemaker, Sick Sinus Syndrome, Bradycardia, PR interval, Atrioventricular block, AV block, Echocardiography, Arrhythmia, AV optimization