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SmartCRT™ Technology

A customizable approach to improved CRT response

About SmartCRT™ Technology

The control needed for every patient is here

SmartCRT is Boston Scientific’s approach to personalize cardiac resynchronization therapy (CRT) by providing physicians with smart solutions to optimize where, when, and how to pace to obtain CRT Response in most patients.

On this page:

Where to pace

ACUITY™ X4 Quadripolar LV Leads

Reach the site of latest activation

With the industry’s smallest lead tip and a variety of shapes, ACUITY X4 is the only family of quadripolar leads designed to optimize basal pacing, which is shown to lead to improved patient outcomes.1-3

  • Fast delivery
  • 99.1% stability
  • Options to lessen Phrenic Nerve Stimulation (PNS)
  • Low thresholds
  • Multiple electrode configurations
  • More proximal pacing options
  • Less time under fluoroscopy
ACUITY X4 Quadripolar LV Leads.


Quickly provides pertinent measurements of 17 vectors options based on clinically relevant tests including right ventricular septal and left ventricular septal (RVS-LVS) delay and phrenic nerve stimulation (PNS).

  • Longer RVS-LVS delay is associated with 30% reduction of risk of heart failure hospitalization or death4
  • RVS-LVS Delay test is automated and takes <1 minute to help choose the best cathode

When to pace

SmartDelay™ AV

Maximize global contractility

Fast and automatic, the SmartDelay algorithm recommends personalized atrioventricular (AV) delays to maximize each patient’s hemodynamic response to CRT.

  • Sensed and paced AV delay
  • Bi-ventricular (Bi-V) or left ventricular (LV) only

How to pace

MultiSite Pacing

Options to maximize response

More options for those who have not responded to single-site pacing. Tailor CRT therapy to your patient’s needs without lead repositioning.

  • MultiSite Pacing - 216 vector combinations
  • SmartVector - Vector recommendations in less than five seconds
  • SmartOffset - Automated timing recommendations

Clinical data

Graph showing a 51% conversion rate of non-responders at 6 months to responders at 12 months

SMART-MSP clinical trial

The SMART-MSP clinical trial exceeded both its endpoints:

  • Safety Endpoint: The MultiSite Pacing (MSP) feature-related complication-free rate at 180 days post MSP on is 99%
  • Effectiveness Endpoint: 51% of the non-responders at 6 months converted to responders at 12 months⁶

View the full SMART-MSP clinical trial

Graph showing lower LVPCT on proximal electrodes compared to distal electrode (0.9V vs. 1.3V) with 258 Spiral S leads
Graph showing lower LVPCT on proximal electrodes compared to distal electrode (0.9V vs. 1.3V) with 225 Spiral L leads

NAVIGATE X4 clinical trial

  • Prospective, single-arm, non-randomized, multicenter clinical trial
  • Enrollment of 791 patients in 88 US centers
  • N=520 (either Spiral L or S) / n = 218 (Straight lead)
  • Primary endpoint: 6-month LV lead-related complication rates, left ventricular pacing capture thresholds (LVPCT) at 3 months
  • Three lead options – thus, greater opportunity for non-apical pacing
  • LVPCT on Spiral leads were lower on proximal electrodes compared to distal electrode (0.9V vs 1.3V)
  • Physicians selected proximal electrode vector in most patients
  • Implant success = 97%
  • Low acute and chronic complication rates
  • 99.1% dislodgement complication free rate
  • 8% phrenic nerve stimulation (PNS) observation rate
  • Proximal electrodes have lower PNS rate (5%) than distal electrode (15%)
  • 0.4% re-intervention rate for PNS⁵

View the full NAVIGATE X4 clinical trial

Graph of SMART-AV Clinical Trial in 2010 showing SmartDelay was non-inferior to fixed AV and echo

SMART-AV clinical trial 2010

Overall results showed SmartDelay was non-inferior to fixed AV and Echo. 1014 patients evaluated at 3 and 6 months.


No difference in improvement in left ventricular and end-systolic volume at 6 months was observed between the SmartDelay and echocardiography arms (P=0.52) or the SmartDelay and fixed arms (P=0.66).⁷

View the full SMART-AV clinical trial 2010

Graph showing the NAVIGATE X4 study comparing LVPCT with the best electrode on spiral.
Chart showing clinical sub-study of SMART-AV showing in patients with long RV-LV, SmartDelay resulted in a significant improvement in LVESV (-43.6 vs. -18.9)

SMART-AV clinical sub-study 2017

  • 82% response rate achieved in patients with long RV-LV delay and SmartDelay
  • 419 patient SMART-AV sub-study

  • With long RV-LV delay, SmartDelay resulted in a significant improvement in LVESV (-43.6 vs. -18)

  • 82% response rate or a 4-fold increase in response over fixed AV timing was achieved in patients with long RV-LV delay who were programmed using SmartDelay⁸

Physician perspective on device longevity

Products that feature SmartCRT

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SmartCRT resources

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1. ACUITY™X4 Physician’s Lead Manual: 359160-002 EN US 2015-07

2. ATTAIN™PERFORMA™4298 Technical Manual: M948374A001. ATTAIN™PERFORMA™STRAIGHT 4398 Technical Manual: M948374A001. ATTAIN™PERFORMA™S 4598 Technical Manual: M950705A001. 

3. Quartet™User’s Manual 100042495

4. Gold M. et al. The Role RV-LV Delay to Predict Time to First Heart Failure Hospitalization and Mortality with Cardiac Resynchronization Therapy. ESC 2014.

5. Mittal S et al. Performance of Anatomically Designed Quadripolar Left Ventricular Leads: Results from the NAVIGATE X4 Clinical Trial. J Cardiovasc Electrophysiol. 2016;27:1199-1205. 

6. Saba S, et al. Safety and Effectiveness of Multi-Site Pacing in Initial Non-Responders to Conventional Cardiac Resynchronization Therapy. LBCT presented at: 2021 Heart Rhythm Society; July 2021; Boston, MA.

7. Ellenbogen, K., Gold, M., et al. Primary Results from the SMART-AV Trial: A Randomized Trial Comparing Empiric, Echocardiographic Guided and Algorithmic AV Delay Programming in Cardiac Resynchronization Therapy (CRT). Circulation 2010;122:2660-68.

8. Gold, M., et al. The Effect of Interventricular Delay on AV Optimization for Cardiac Resynchronization Therapy. AHA 2017.

Indications, safety, and warnings