Intracardiac conduction time as a predictor of cardiac resynchronization therapy response: Results of the BIO|SELECT pilot study

Cardiac resynchronization therapy guided by interventricular conduction delay: How to choose between biventricular pacing or conduction system pacing

BACKGROUND

Biventricular pacing (BIV) is the gold standard for cardiac resynchronization therapy (CRT). Thirty percent of patients do not respond to CRT. Conduction system pacing (CSP) represents a viable alternative. Interventricular conduction delay (IVCD), as electrical desynchrony marker, is a CRT response predictor. The aim of this study was to determine the incidence of CRT responders by selecting the best approach between BIV and CPS based on intraoperative IVCD measurement in patients with HFrEF and LBBB.

METHODS

Ninety-six patients were randomly assigned in a 1:1 ratio to either a standard BIV group(control group, CG) or a group where the CRT approach was determined based on IVCD evaluation(study group, SG). If the right ventricular sensed electrogram (RVs)-left ventricular sensed electrogram (LVs) interval was ≥100 ms, the lead was left in its original position; otherwise, the LV lead was removed, and CSP was performed instead. Clinical, EKG, and echocardiographic features have been assessed pre- and 6 months post-implant. Echocardiographic and clinical responder were evaluated.

RESULTS

Thirty-seven percent of patients in the SG underwent CSP, as the operative algorithm. The incidence of CRT responders was significantly higher in the SG (echocardiographic criterion: 92.5% vs. 69.8%, p:.009; clinical criterion 87.5% vs. 62.8%, p:.014). The SG showed a significantly greater difference in EF between pre- and post-implant as well as reduced end-diastolic and systolic volumes. Univariate and multivariate regression analysis indicated that enrollment in the SG was the only factor associated with CRT response.

CONCLUSION

Intraoperative assessment of IVCD could help determine the optimal CRT approach between BIV and CSP, leading to a significant improvement in the rate of CRT responders.

Biventricular or Conduction System Pacing for Cardiac Resynchronization Therapy: A Strategy for Cardiac Resynchronization Based on a Hybrid Approach

BACKGROUND

Cardiac resynchronization therapy (CRT) is usually performed with biventricular pacing (BiVP), but recently, conduction system pacing (CSP) has been proposed as an alternative in case of BiVP failure. The aim of this study is to define an algorithm to choose between BiVP and CSP resynchronization using the interventricular conduction delays (IVCD) as a guide.

METHODS

Consecutive patients from January 2018 to December 2020 with an indication for CRT were prospectively enrolled in the study group (delays-guided resynchronization group, DRG). A treatment algorithm based on IVCD was used to decide whether to leave the left ventricular (LV) lead to perform BiVP or pull it out and perform CSP. Outcomes from the DRG group were compared to a historical cohort of CRT patients who underwent CRT procedures between January 2016 and December 2017 (resynchronization standard guide group, SRG). The primary endpoint was a composite of cardiovascular mortality, heart failure (HF) hospitalization, or HF event at 1 year after the date of intervention.

RESULTS

The study population consisted of 292 patients, of which 160 (54.8%) were in the DRG and 132 (45.2%) in the SRG. In the DRG, 41 of 160 patients underwent CSP based on the treatment algorithm (25.6%). The primary endpoint was significantly higher in the SRG (48/132, 36.4%) compared to the DRG (35/160, 21.8%) (hazard ratio (HR): 1.72; 95% confidence interval (CI): 1.12-2.65; p = 0.013).

CONCLUSIONS

A treatment algorithm based on IVCD shifted one patient out of every four from BiVP to CSP, with consequent reduction in the primary endpoint after implantation. Therefore, its application could be useful to determine whether to perform BiVP or CSP.

Association of interventricular activation delay with clinical outcomes in cardiac resynchronization therapy

BACKGROUND

Pacing at sites of longest interventricular delay has been associated with greater reverse remodeling in cardiac resynchronization therapy (CRT). However, the effects of pacing at such sites on clinical outcomes is less well studied.

OBJECTIVE

The purpose of this study was to assess the association between interventricular delay and clinical outcomes in CRT patients implanted with quadripolar left ventricular (LV) leads.

METHODS

RALLY-X4 was a registry study of the Acuity X4 quadripolar LV leads. Interventricular delay was measured during unpaced basal rhythm from the right ventricular (RV) lead to the LV lead electrode (E1 to E4) chosen for CRT pacing. Patients were stratified by median RV-LV delay (80 ms) into short and long delay groups; they also were analyzed by multivariable modeling. The primary composite outcome measure was all-cause mortality and heart failure hospitalization (HFH) at 18 months.

RESULTS

A total of 581 patients had complete RV-LV delay data. Mean LV ejection fraction was 27%, and 73% had typical left bundle branch block. Predictors of long RV-LV delay included female sex, left bundle branch block, and QRS duration >150 ms. Survival free of the primary outcome at 18-month follow-up was 87% in the long activation delay group compared with 77% in the short delay group (P = .0042). Multivariate analysis showed that RV-LV delay was an independent predictor of survival free of HFH (P = .028).

CONCLUSION

Among CRT patients with quadripolar LV pacing leads, longer baseline interventricular activation delay was significantly associated with the composite endpoint of all-cause mortality and HFH.