SmartDelay Determined AV Optimization: A Comparison to Other AV Delay Methods Used in Cardiac Resynchronization Therapy - SMART-AV
The goal of the trial was to compare optimization of atrioventricular (AV) delay by echocardiography versus an electrocardiogram (ECG)-based algorithm (SmartDelay) versus a fixed interval of 120 ms among patients who received cardiac resynchronization therapy (CRT).
Optimization of the AV delay with an ECG-based algorithm will improve outcomes.
- NYHA class III or IV
- LVEF ≤35%
- QRS ≥120 msec
- Sinus rhythm at the time of CRT implant
Number of screened applicants: 1,060
Number of enrollees: 980
Duration of follow-up: 6 months
Mean patient age: 66 years
Percentage female: 29%
Ejection fraction: 25%
NYHA class: II-4%, III-92%, IV-4%
- Complete heart block or unable to tolerate pacing at VVI-40 for up to 14 days
- Previous CRT
- LVESV at 6 months
- LVEDV at 6 months
- Six-minute walk distance
- NYHA class
- Quality of life
Patients who met criteria for CRT were eligible to participate: New York Heart Association (NYHA) class III or IV despite optimal medical therapy, left ventricular ejection fraction (LVEF) ≤35%, and QRS duration ≥120 ms. One to 14 days after CRT implant (VVI-40-RV), patients were programmed to DDD(R) 60 and randomized to optimization of AV delay by echocardiography (n = 323) versus an ECG-based algorithm (n = 332) versus a fixed delay of 120 ms (n = 325).
At baseline, the use of angiotensin-converting enzyme inhibitors/angiotensin-receptor blockers was 87%, beta-blockers 92%, and spironolactone 32%.
Overall, 980 patients were randomized. In the ECG-based algorithm group, the mean age was 66 years, 29% were women, mean ejection fraction was 25%, mean QRS duration was 152 ms, and proportion with ischemic cardiomyopathy was 57%.
The median change in LV end-systolic volume (LVESV) at 6 months was -19 ml for the echo group, -21 ml for the ECG-based algorithm group, and -15 ml for the fixed delay group (p = 0.52 for ECG vs. echo and p = 0.66 for ECG vs. fixed delay). Female patients tended to respond more favorably to echo and ECG optimization of AV delay compared with fixed delay.
The median change in LV end-diastolic volume (LVEDV) at 6 months was -16 ml for the echo group, -13 ml for the ECG-based algorithm group, and -12 ml for the fixed delay group (p = NS between all groups).
The median change in LVEF was 6%, 6%, and 5.1%, respectively. Six-minute walk, quality of life, and NYHA classification were also similar between groups. There was no difference in heart failure-related adverse events between groups.
Among patients who undergo CRT for symptomatic heart failure, optimization of AV delay with the use of echocardiography or an ECG-based algorithm did not improve LV geometry or other outcomes at 6 months compared with a fixed delay of 120 ms. At the present time, a fixed AV delay remains the recommended approach to optimization of CRT. The possible benefit observed among women would need to be prospectively tested.
Ellenbogen KA, Gold MR, Meyer TE, et al. Primary Results From the SmartDelay Determined AV Optimization: A Comparison to Other AV Delay Methods Used in Cardiac Resynchronization Therapy (SMART-AV) Trial: A Randomized Trial Comparing Empirical, Echocardiography-Guided, and Algorithmic Atrioventricular Delay Programming in Cardiac Resynchronization Therapy. Circulation 2010;Nov 15:[Epub ahead of print].
Presented by Dr. Kenneth Ellenbogen at the American Heart Association Scientific Sessions, Chicago, IL, November 15, 2010.
Keywords: Follow-Up Studies, Ventricular Function, Left, Quality of Life, Cardiomyopathies, Dichlorodiphenyldichloroethane, Heart Failure, Stroke Volume, Electrocardiography, Cardiac Resynchronization Therapy, Echocardiography
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