• Interventional Techniques & Devices Clinical Trials
• Heart Failure

For heart failure patients who are undergoing cardiac resynchronization therapy (CRT), echocardiographic- or ECG-based optimized AV delay does not improve upon standard programming approaches, according to new findings from the SmartDelay Determined AV Optimization: A Comparison to Other AV Delay Methods Used in Cardiac Resynchronization Therapy (SMART-AV) trial.

When added to optimal medical therapy, CRT has the potential to reduce heart failure hospitalizations, improve quality of life, and prolong survival in patients with heart failure and prolonged QRS duration. Achieving the full benefits of CRT, however, may depend on programming the optimal AV delay. To date, techniques for AV optimization have varied across major CRT trials, including Cardiac Resynchronization-Heart Failure (CARE-HF) and Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure (COMPANION). No consensus approach has emerged to date.

The SMART-AV trial was designed to compare current options for AV optimization, including the investigational ECG-based SmartDelay device algorithm, which calculates AV delay based on left ventricular (LV) lead location, intraventricular timing, and sensed and paced AV intervals. The trial included 980 patients with New York Heart Association (NYHA) class III or IV heart failure, reduced ejection fraction (EF ≤35%), and prolonged QRS duration (≥120 ms) who were indicated for a CRT device. All patients were also receiving optimal pharmacological therapy. Those with complete heart block, a history of CRT use, or an inability to tolerate pacing at VVI-40-RV for up to 14 days were excluded from the study.

Patients were randomly assigned to AV delay that was optimized with SmartDelay (n=332), echocardiography-optimized AV delay (n=323), or a fixed empirical AV delay of 120 ms (n=326). The primary endpoint was LV end-systolic volume (LVESV) at 6 months. Secondary endpoints included structural outcomes, such as EF and LV end-diastolic volume, as well as functional outcomes, including 6-minute-walk distance, NYHA class, and quality of life.

Kenneth A. Ellenbogen, MD, Virginia Commonwealth University School of Medicine and Medical College of Virginia Hospitals, Richmond, Virginia, USA, presented the results of SMART-AV.

At 6 months, the SmartDelay algorithm provided a median LVESV reduction of 21 mL, which was comparable with the median reductions of 19 mL in the echocardiography group (p=0.52) and 15 mL in the fixed-delay group (p=0.66). Secondary structural and functional endpoints were also similar across the three study groups.

In a post hoc subgroup analysis, the primary efficacy findings were consistent across several subgroups, defined by heart failure etiology (ischemic vs nonischemic), percentage of atrial pacing (≥30% vs <30%), QRS width (≥150 ms vs <150 ms), and left bundle branch block (present or absent). When evaluated by gender, however, women responded better to the SmartDelay algorithm than to fixed AV delay (interaction p=0.02). By comparison, no differences were seen between the SmartDelay and echocardiography groups in women or across any study groups in men.

Given the SMART-AV findings, AV optimization is not warranted for routine use in heart failure patients who receive CRT, Dr. Ellenbogen said. However, AV optimization may have a future role in the treatment of selected heart failure patients, such as the 30% of patients who do not respond initially to standard CRT.

The SMART-AV findings were also published simultaneously online in Circulation. Ellenbogen KA et al. Circulation 2010.

• © 2010 MD Conference Express