Maximization of interventricular conduction time by means of quadripolar leads for cardiac resynchronization therapy

Electrical delays in quadripolar leads with cardiac resynchronization therapy

BACKGROUND

Pacing at sites of late intraventricular activation (QLV) or long interventricular conduction (right ventricle [RV]-left ventricular [LV]) have been associated with improved cardiac resynchronization therapy (CRT) outcomes. Quadripolar leads improve CRT outcomes by allowing for electrical repositioning to optimize pacing sites. However, little is known regarding the effect of such repositioning on electrical delay.

OBJECTIVE

Determine the relationship between different electrical bipoles from a quadripolar lead and measures of electrical delay.

METHODS

Forty-six patients underwent CRT with a quadripolar lead. The RV-LV and QLV intervals were measured for both the proximal and distal bipoles and the difference (Δ) between bipoles for each measure were calculated. Multivariate analyses were performed to identify predictors of electrical delays.

RESULTS

This was a typical CRT population with a mean age of 65 years and ejection fraction of 27%, with left bundle branch block (LBBB) present in 70%. The regression model for ΔQLV was significant (p = .05), with both gender (p = .008) and LBBB status (p = .020) significant predictors. The overall regression model for ΔRV-LV was not significant. ΔQLV and ΔRV-LV were significant among LBBB patients. Among non-LBBB, only ΔRV-LV was significant (mean: 7.2 ms, p = .006). ΔRV-LV versus ΔQLV were strongly correlated in LBBB (R²  = .92) but not non-LBBB (R²  = .06).

CONCLUSION

In LBBB, ΔRV-LV and ΔQLV are closely correlated suggesting that the proximal bipole and thus basal LV pacing sites should be selected when feasible. Greater variation in activation pattern is present in non-LBBB, so pacing sites should be individualized.

Design and rationale of the Impact of MultiPoint pacing in CRT patients with reduced RV-to-LV delay (IMAGE-CRT) study

BACKGROUND

Cardiac resynchronization therapy (CRT) is an established treatment in patients with heart failure and prolonged QRS duration. A biventricular device is implanted to achieve faster activation and more synchronous contraction of the ventricles. Despite the convincing effect of CRT, 30-40% of patients do not respond. We decided to investigate the role of multipoint pacing (MPP) in a selected group of patients with right ventricle (RV)-to-left ventricle (LV) intervals less than 80 ms that do not respond to traditional CRT.

METHODS

We will enrol 248 patients in this patient-blinded, observational, clinical study aiming to investigate if MPP could decrease LV end-systolic volume (ESV) in patients with RV-to-LV interval less than 80 ms. MPP will be activated ON at implant in patients with RV-to-LV delay less than 80 ms and OFF in RV-to-LV at least 80 ms. At follow-up the activation of MPP will be related to CRT response. The primary study endpoint will be the responder rate at 6 months, defined as a decrease in LV ejection fraction, LV end-diastolic volume, LV end-systolic volume (LVESV) at least 15% from baseline. Secondary outcomes include 12 months relative percentage reduction in LVESV and a combined clinical outcome measure of response to CRT defined as the patient being alive, no hospitalization due to heart failure, and experiencing an improvement in New York Heart Association functional class (Composite-Score).

CONCLUSION

Reducing the nonresponder rate continues to be an important goal for CRT.If an increase in reverse remodelling can be achieved by MPP, this study supports the conduct of larger trials investigating the role of MPP on clinical outcomes in selected patients treated, right now, only with traditional CRT.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02713308. Registered on 18 March 2016.