SmartDelay determined AV optimization: a comparison of AV delay methods used in cardiac resynchronization therapy (SMART-AV): rationale and design.
BACKGROUND
The clinical benefit of cardiac resynchronization therapy (CRT) for patients with moderate-to-severely symptomatic heart failure, left ventricular systolic dysfunction, and ventricular conduction delay is established. However, some patients do not demonstrate clinical improvement following CRT. It is unclear whether systematic optimization of the programmed atrioventricular (AV) delay improves the rate of clinical response.


METHODS
SMART-AV is a randomized, multicenter, double-blinded, three-armed trial that will investigate the effects of optimizing AV delay timing in heart failure patients receiving CRT + defibrillator (CRT-D) therapy. A minimum of 950 patients will be randomized in a 1:1:1 ratio using randomly permuted blocks within each center programmed to either DDD or DDDR with a lower rate of 60. The study will include echocardiographic measurements of volumes and function [e.g., left ventricular end-systolic volume (LVESV)], biochemical measurements of plasma biomarker profiles, and functional measurements (e.g., 6-minute hall walk) in CRT-D patients who are enrolled and randomized to fixed AV delay (i.e., 120 ms), AV delay determined by electrogram-based SmartDelay, or an AV delay determined by echocardiography (i.e., mitral inflow). Patients will be evaluated prior to initiation of CRT, 3 and 6 months post-implant. The primary endpoint is the relative change in LVESV at 6 months between the groups. Patient enrollment commenced in May 2008 and the study is registered at clinicaltrials.gov.


CONCLUSIONS
SMART-AV is a randomized, clinical trial designed to evaluate three different methods of AV delay optimization to determine whether systematic AV optimization is beneficial for patients receiving CRT for 6 months post-implant.
Stein
Kenneth M
KM
Department of Medicine, Maurice & Corinne Greenberg Division of Cardiology, Weill Medical College of Cornell University, New York, New York, USA. kenneth.stein@bsci.com
Ellenbogen
Kenneth A
KA
Gold
Michael R
MR
Lemke
Bernd
B
Lozano
Ignacio Fernández
IF
Mittal
Suneet
S
Spinale
Francis G
FG
Van Eyk
Jennifer E
JE
Waggoner
Alan D
AD
Meyer
Timothy E
TE
D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004311:Double-Blind Method; D004452:Echocardiography; D004554:Electric Countershock; D006333:Heart Failure / Q000628:therapy*; D006801:Humans; D012107:Research Design