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).
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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
23
Pacemaker will be set to a long, fixed AV delay to minimize ventricular pacing
Pacemaker will be set to the AV delay that produces the greatest cardiac output in echocardiography for each patient enrolled.
UCSD Sulpizio Cardiovascular Center
La Jolla, California, United States
Comparison of Change in Echocardiographic Parameters LV Dimension at End-diastole, LV Dimension at End-systole, and Tricuspid Annular Plane Systolic Excursion (cm) From Baseline to Followup, in Optimized AV Delay Versus Long-fixed AV Delay Groups.
Comparison (∆) of change in echocardiographic parameters left ventricular (LV) dimension at end-diastole, left ventricular (LV) dimension at end-systole, and tricuspid annular plane systolic excursion (cm) from baseline to followup, in Optimized AV delay versus Long-fixed AV delay groups. A reduction LV dimension indicates improvement in function, and an increase in tricuspid annular plane excursion represents an improvement in function.
Time frame: 6 months
Comparison of Echocardiographic Parameters Mitral E Wave Velocity (cm/s) and Mitral A Wave Velocity (cm/s) at Baseline and Followup, in Optimized AV Delay Versus Long-fixed AV Delay Group.
Comparison (∆) of echocardiographic parameters mitral E wave velocity (cm/s) and mitral A wave velocity (cm/s) at baseline and followup, in Optimized AV delay versus Long-fixed AV delay group. An increase in mitral E wave velocity and a decrease in mitral A velocity represent an improvement in function.
Time frame: 6 months
Comparison of Change in Echocardiographic Parameter ΔE/A and Mean E/e' Ratio (Unitless) From Baseline to Followup, in Optimized AV Delay Versus Long-fixed AV Delay Groups.
Comparison (Δ) of change in echocardiographic parameter ΔE/A and Mean E/e' ratio (unitless) from baseline to followup, in Optimized AV delay versus Long-fixed AV delay groups. An higher delta E/A and mean E/e' ratio represent improvement in function,
Time frame: 6 months
Comparison of Echocardiographic Parameter Deceleration Time (Msec) at Baseline and Followup, in Optimized AV Delay Versus Long-fixed AV Delay Group.
Comparison (∆) of Echocardiographic Parameter Deceleration time (msec) at Baseline and Followup, in Optimized AV Delay Versus Long-fixed AV Delay Group. A reduction in deceleration time represents an improvement in function.
Time frame: 6 months
Comparison of Change in Echocardiographic Parameters LVED End Diastolic Volume Index, LVES Volume Index, Maximum LA Volume Index, and Minimum LA Volume Index (ml/m2) From Baseline to Follow-up, in Optimized AV Delay Versus Long-fixed AV Delay Groups.
Comparison of change in echocardiographic parameters left ventricular end diastolic (LVED) volume index, left ventricular end systolic (LVES) volume index, maximum left atrial (LA) volume index, and minimum left atrial (LA) volume index (ml/m2) from baseline to follow-up, in Optimized AV delay versus Long-fixed AV delay groups. A reduction in volume indexes represents an improvement in function.
Time frame: 6 months
Comparison of Change in Echocardiographic Parameters Left Ventricular Ejection Fraction and Global Longitudinal Strain (%) From Baseline to Followup, in Optimized AV Delay Versus Long-fixed AV Delay Groups.
Comparison (∆) of Change in Echocardiographic Parameters Left Ventricular Ejection Fraction and Global Longitudinal Strain (%) From Baseline to Followup, in Optimized AV Delay Versus Long-fixed AV Delay Groups. An increase in left ventricular ejection time represents an improvement in function. A more negative global longitudinal strain % represents an improvement in function.
Time frame: 6 months
Comparison of Change in Echocardiographic Parameters Tricuspid Regurgitation (TR) Velocity m/s From Baseline to Followup, in Optimized AV Delay Versus Long-fixed AV Delay Groups.
Comparison (∆) of Change in Echocardiographic Parameters Tricuspid Regurgitation (TR) velocity m/s From Baseline to Followup, in Optimized AV Delay Versus Long-fixed AV Delay Groups. An reduction in tricuspid regurgitation velocity represents an improvement in function.
Time frame: 6 months
Comparison of Change in Echocardiographic Parameters Left Ventricular Mass (gm) From Baseline to Followup, in Optimized AV Delay Versus Long-fixed AV Delay Groups.
Comparison (∆) of Change in Echocardiographic Parameters left ventricular mass (gm) From Baseline to Followup, in Optimized AV Delay Versus Long-fixed AV Delay Groups. A reduction in left ventricular mass represents an improvement in function.
Time frame: 6 months
Comparison of Measured Distance Walked in 6 Minutes in Meters From Baseline and Followup, in Optimized AV Delay Group Versus Long-fixed AV Delay Group.
Comparison (∆) of measured distance walked in 6 minutes in meters from baseline and followup, in Optimized AV delay group versus Long-fixed AV delay group. An increase in distance walked during the 6 minute walk test represents an improvement in function.
Time frame: 6 months
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