UPMC Cardiology Chief Presents Findings From National SMART MSP Clinical Trial

The recently completed SMART MSP post-approval study results were presented at the Heart Rhythm Society (HRS) 2021 Scientific Sessions in July.

Samir F. Saba, MD, FACC, FHRS, served as the national principal investigator for this post-approval clinical trial. Sandeep Jain, MD, director of cardiac electrophysiology and the Center for Atrial Fibrillation in the UPMC Heart and Vascular Institute, served as the site principal investigator for UPMC.

The SMART MSP study led by Dr. Saba was designed as a prospective, single-arm, multi-center investigation. The study's objective was to evaluate the effectiveness of the Left Ventricular MuliSite Pacing (LV MSP) feature in cardiac resynchronization therapy defibrillator (CRT-D) devices and confirm its safety in a post-approval study when used in accordance with approved labeling. The Resonate family of CRT-D devices from Boston Scientific, which was used in SMART MSP trial, was granted U.S. Food and Drug Administration (FDA) approval in May 2017. 

CRT-D therapy is beneficial for a majority of heart failure patients, however a third of individuals who have traditional biventricular pacemakers or defibrillators implanted do not respond to the intervention. This group of nonresponders to traditional CRT therapy were the target of this study to assess whether multisite pacing could improve response rates and do so safely.

Study Highlights and Key Findings

The SMART MSP study enrolled 584 participants at 52 centers in the United States. Subjects were eligible for study enrollment if they met CRT indications according to published guidelines and received new Resonate CRT-D devices with an Acuity LV quadripolar lead. 

At the six-month follow-up, 137 participants (25.9%) were deemed to be nonresponders to conventional CRT therapy based on their clinical composite score. Of the 137 nonresponders, 102 participants had LV MSP pacing enabled on their devices and were followed for an additional six months. 

These patients constituted the safety cohort of the trial. Of these patients, 78 had their LV MSP feature turned on and achieved greater than 93% pacing. These 78 patients were evaluated for the effectiveness endpoint. At the 12-month follow-up, approximately half of the nonresponder population – 40 of 78 subjects – showed improved clinical composite scores.

“In essence, the LV MSP approach converted half of the nonresponders to become responders. This rate was far above our initial performance goal of 5% at the outset of the trial,” says Dr. Saba.

In the nonresponder cohort, 20.6% experienced some form of heart failure event during the first six months of the study using traditional CRT. In the second six months, after enabling LV MSP, this group experienced a decreased rate of heart failure events – 10.8%.

Only one complication in the nonresponder cohort was attributable to LV MSP usage, producing a 99% complication free-rate at the end of the study.

Furthermore, the use of LV MSP only marginally affected the estimated battery life of the implanted devices. The mean battery life in devices before LV MSP initiation - at the six-month checkpoint - was estimated to be 8.9 years, plus/minus 2.1 years. Mean battery life assessment at the 12-month study endpoint in the devices using LV MSP was estimated to be 8.1 years, plus/minus 2.2 years.

“This trial showed robust safety and efficacy data for the use of LV MSP in heart failure patients, and that a significant portion of nonresponders to traditional CRT can be converted to responders after using multisite pacing," says Dr. Saba. "More research needs to be conducted to find other patient populations for whom the therapy may benefit, how best to optimize device programming for success, what is the mechanism of benefit from multisite pacing, and what effect using MSP earlier after implantation may have on patient status or response to therapy."

Complete results of the trial will be forthcoming in a peer-reviewed manuscript.

References and Further Reading

Strategic Management to Improve CRT Using Multi-Site Pacing Post-Approval Study (Reference #C1918) (SMARTMSP). ClinicalTrials.gov Identifier: NCT03257436. Principal Investigator: Samir Saba, MD. Sponsor: Boston Scientific Corporation.

Safety and Effectiveness of Multisite Pacing in Initial Non-Responders to Conventional Cardiac Resynchronization Therapy: SMART-MSP Primary Results. Presented by Samir F. Saba, MD on Behalf of the SMART-MSP Investigators. Presentation given at the 2021 HRS Scientific Sessions.

Learn more about Dr. Saba and the UPMC Heart and Vascular Institute.