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SmartDelay Determined AV Optimization: A Comparison to Other AV Delay Methods Used in Cardiac Resynchronization Therapy - SMART-AV
Description:
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).
Hypothesis:
Optimization of the AV delay with an ECG-based algorithm will improve outcomes.
Study Design
- Randomized
- Parallel
Patient Populations:
- 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%
Exclusions:
- Complete heart block or unable to tolerate pacing at VVI-40 for up to 14 days
- Previous CRT
Primary Endpoints:
- LVESV at 6 months
Secondary Endpoints:
- LVEDV at 6 months
- LVEF
- Six-minute walk distance
- NYHA class
- Quality of life
Drug/Procedures Used:
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).
Concomitant Medications:
At baseline, the use of angiotensin-converting enzyme inhibitors/angiotensin-receptor blockers was 87%, beta-blockers 92%, and spironolactone 32%.
Principal Findings:
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.
Interpretation:
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.
References:
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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