Electrical characteristics of deep septal vs. left bundle branch (area) pacing

Background/Introduction

Recent studies have described transvenous left bundle branch (LBB) pacing as a new conduction system pacing strategy. However, information on effect of pacing depth within the septum and the additional effect of LBB capture is unknown.

Purpose

To investigate the relation of electrocardographic characteristics with transseptal LV lead implantation depth and LBB capture.

Methods

20 consecutive patients referred for pacemaker implantation were enrolled. The right atrial (RA) lead was positioned according to routine practice. The LV septal pacing lead (Medtronic 3830) was transvenously positioned against the right side of the interventricular septum and advanced in small steps of 1–2mm towards the left side of the septum. At each depth in the septum 12-lead ECG's were recorded during pacing, from which vectorcardiograms (VCG) were calculated. QRS duration and QRS area were measured, the latter being the integral of the QRSarea in X, Y and Z directions. Successful LBB capture was defined as paced right bundle branch block (RBBB) morphology, stable and short stimulus to LV activation time (LVAT; R in V5) and recorded LBB potential.

Differences were compared among pacing conditions using repeated measures ANOVA with Bonferroni multiple comparisons procedure applied to pairwise comparisons. Statistical significance was assumed at p<0.05.

Results

LV septal lead implantation was successful in all patients. Left bundle branch capture was achieved in 10/20 patients (50%). Post-procedural LV pacing threshold, impedance and sensing was 0.7±0.1 V at 0.5 ms pulse width, 658±5 Ω and 13±10 mV, respectively. Compared to intrinsic rhythm, QRS duration was significantly increased by both RV septum (RVS; 124±5 vs. 161±3 ms) and LV septum pacing (LVS; 142±3 ms).

QRS area increased significantly during RVS pacing as compared to intrinsic rhythm but decreased when moving from RVS to LVS to values close to intrinsic rhythm (panel A & B). LVS-pacing derived QRS area was significantly lower in patients with LBB capture (36±6 mV*ms) compared to patients without LBB capture (deep septal pacing; 46±12 mV*ms).

The reduction in QRS area between RVS and LVS pacing coincided with normalization of the QRS vector in the transverse plane (panel C), which is characterized electrocardiographically by predominantly negative-to-positive inversion of the QRS complex in the precordial leads (V1-V3).

Conclusions

Compared to RV septal pacing, LV septal pacing restores ventricular electrical synchrony, as determined by QRS area, and normalizes the activation vector in the transverse plane to a level comparable to intrinsic rhythm. Differences in resynchronization between left bundle branch pacing and deep septal pacing are small.

LBBAP restores ventricular synchrony

Funding Acknowledgement

Type of funding source: None

Change in QRS area by cardiac resynchronization therapy is associated with clinical outcomes and echocardiographic response

Background

Cardiac Resynchronization Therapy (CRT) is the cornerstone of treatment in patients with dyssynchronous heart failure. Recently, baseline QRS area proved to predict outcomes after CRT better than QRS duration and morphology.

Purpose

It was the aim of the study to investigate whether the change in QRS area (ΔQRS area) by CRT-pacing further improves the prediction of CRT outcomes.

Methods

We conducted a retrospective analysis on 1,299 patients, who were included in a CRT-registry from three Dutch University hospitals with both pre- (baseline) and post-implantation 12-lead ECGs. ΔQRS area and ΔQRS duration were defined as the decrease in their respective values after CRT. Optimal cut offs for ΔQRS area and ΔQRS duration by means of Youden indices were found at 62μVs and −11ms, respectively. Primary endpoint was a combination of all-cause mortality, heart transplantation, and left ventricular assist device implantation. Secondary endpoint was the relative reduction in left ventricular end-systolic volume (LVESV), and echocardiographic response being defined as ≥15% LVESV reduction.

Results

The primary endpoint occurred in 408 patients (31%). ΔQRS area was superior to ΔQRS duration for the primary and secondary endpoints. Primary endpoint analysis showed a lower risk in the ΔQRS area ≥62μVs than in the <62μVs group (HR 0.43; 0.33–0.56, p<0.001). In the multivariable analysis, both baseline QRS area and ΔQRS area remained significantly associated with both primary and secondary endpoints. Clinical outcome (left panel of figure) and echocardiographic response (right panel) were significantly worse in patients with baseline QRS area <109μVs (group 3) than in those with QRS area ≥109μVs. Within the latter group, outcomes were significantly better in patients with ΔQRS area ≥62μVs (group 1) as compared to ΔQRS area <62μVs (group 2) (figure). Baseline QRS duration and ΔQRS duration were not independently associated with both clinical outcome and echocardiographic response.

Conclusion

The combination of baseline QRS area and ΔQRS area has a stronger association with CRT response than baseline QRS area alone, and (Δ)QRS duration. These results suggest that especially in patients with a good electrical substrate (large baseline QRS area) it is worthwhile to adjust CRT to achieve the largest decrease in QRS area.

Funding Acknowledgement

Type of funding source: None

Improving atrioventricular coupling in heart failure patients with PR prolongation, the ReachPR Trial

Background

PR prolongation is associated with poor hemodynamic performance and may contribute to heart failure (HF). There is some evidence that in HF patients, normalization of atrioventricular (AV) coupling can attenuate HF.

Purpose

To investigate acute hemodynamic effects of restoration of AV coupling by atrio-biventricular (BiV) pacing in patients with HF and PR prolongation, but without evident ventricular dyssynchrony.

Methods

Nineteen patients underwent BiV pacemaker implantation. An invasive hemodynamic pacing protocol was performed during BiV and right ventricular (RV) pacing with four paced AV delays (100, 75, 50 and 25% of patient's PR interval during baseline AAI pacing). All patients had symptomatic HF, left ventricular ejection fraction (LVEF) <35% and PR interval ≥230 ms, without evident prolonged QRS duration >150 ms or left bundle branch block. Acute hemodynamic response was assessed by invasive left ventricular (LV) stroke work measurements (conductance catheter technique).

Results

At baseline, PR interval was 255±22 ms, QRS duration 122±19 ms and LVEF 29±6%. Reducing AV delay to 50% of patient's intrinsic PR interval by BiV pacing resulted in a median 25% increase (p<0.05) in LV stroke work relative to baseline (figure, left panel). This increase in LV stroke work was mainly determined by an increase in LV stroke volume (figure, right panel). In contrast to BiV pacing, reducing AV delay by RV pacing did not improve LV stroke work (figure, left panel).

Conclusion

In patients with HF and PR prolongation, BiV pacing can be used to improve AV coupling that leads to hemodynamic improvement. These results suggest that BiV pacing may also be beneficial in this subset of HF patients that are currently not indicated for CRT.

ReachPR Trial

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): Abbott funded a part of this study.