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.

Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Implantable Devices, Acute Heart Failure, Echocardiography/Ultrasound

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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