Short-Term Hemodynamic and Electrophysiological Effects of Cardiac Resynchronization by Left Ventricular Septal Pacing

BACKGROUND

Cardiac resynchronization therapy (CRT) is usually performed by biventricular (BiV) pacing. Previously, feasibility of transvenous implantation of a lead at the left ventricular (LV) endocardial side of the interventricular septum, referred to as LV septal (LVs) pacing, was demonstrated.

OBJECTIVES

The authors sought to compare the acute electrophysiological and hemodynamic effects of LVs with BiV and His bundle (HB) pacing in CRT patients.

METHODS

Temporary LVs pacing (transaortic approach) alone or in combination with right ventricular (RV) (LVs+RV), BiV, and HB pacing was performed in 27 patients undergoing CRT implantation. Electrophysiological changes were assessed using electrocardiography (QRS duration), vectorcardiography (QRS area), and multielectrode body surface mapping (standard deviation of activation times [SDAT]). Hemodynamic changes were assessed as the first derivative of LV pressure (LVdP/dtmax).

RESULTS

As compared with baseline, LVs pacing resulted in a larger reduction in QRS area (to 73 ± 22 μVs) and SDAT (to 26 ± 7 ms) than BiV (to 93 ± 26 μVs and 31 ± 7 ms; both p < 0.05) and LVs+RV pacing (to 108 ± 37 μVs; p < 0.05; and 29 ± 8 ms; p = 0.05). The increase in LVdP/dtmax was similar during LVs and BiV pacing (17 ± 10% vs. 17 ± 9%, respectively) and larger than during LVs+RV pacing (11 ± 9%; p < 0.05). There were no significant differences between basal, mid-, or apical LVs levels in LVdP/dtmax and SDAT. In a subgroup of 16 patients, changes in QRS area, SDAT, and LVdP/dtmax were comparable between LVs and HB pacing.

CONCLUSIONS

LVs pacing provides short-term hemodynamic improvement and electrical resynchronization that is at least as good as during BiV and possibly HB pacing. These results indicate that LVs pacing may serve as a valuable alternative for CRT.

Atrioventricular dromotropathy: evidence for a distinctive entity in heart failure with prolonged PR interval?

Heart failure (HF) is often accompanied by atrioventricular (AV) conduction disturbance, represented by prolongation of the PR interval on the electrocardiogram. Studies suggest that PR prolongation exists in at least 10% of HF patients, and it seems more prevalent in the presence of prolonged QRS duration. A prolonged PR interval may result in elevated left ventricular (LV) end-diastolic pressure, diastolic mitral regurgitation, and reduced LV pump function. This seems especially the case in patients with heart disease, in whom it is associated with an increased risk for atrial fibrillation, advanced AV heart block, HF, and death. These findings point towards the importance of proper AV coupling in HF patients. A few studies, strongly differing in design, suggest that restoration of AV coupling in patients with PR prolongation by pacing improves cardiac function and clinical outcomes. These observations argue for AV-dromotropathy as a potential target for pacing therapy, but other studies show inconsistent results. Given its potential clinical implications, restoration of AV coupling by pacing warrants further investigation. Additional possible future research goals include assessing different techniques to measure compromised AV coupling, determine the best site(s) of ventricular pacing, and assess a potential influence of diastolic mitral regurgitation in the efficacy of such therapy.

Novel bradycardia pacing strategies

The adverse effects of ventricular dyssynchrony induced by right ventricular (RV) pacing has led to alternative pacing strategies, such as biventricular, His bundle (HBP), LV septal (LVSP) and left bundle branch pacing (LBBP). Given the overlap, LVSP and LBBP are also collectively referred to as left bundle branch area pacing (LBBAP). Although among these alternative pacing sites HBP is theoretically the ideal strategy as it maintains a physiological ventricular activation, its application requires more skills and is associated with the most complications. LBBAP, where the ventricular pacing lead is advanced through the interventricular septum to its left side, creates ventricular activation that is only slightly more dyssynchronous. Preliminary studies have shown that LBBAP is feasible, safe and encounters less limitations than HBP. Further studies are needed to differentiate between LVSP and LBBP with regard to acute functional and long-term clinical outcome.

Pacing therapy for atrioventricular dromotropathy: a combined computational-experimental-clinical study

AIMS

Investigate haemodynamic effects, and their mechanisms, of restoring atrioventricular (AV)-coupling using pacemaker therapy in normal and failing hearts in a combined computational-experimental-clinical study.

METHODS AND RESULTS

Computer simulations were performed in the CircAdapt model of the normal and failing human heart and circulation. Experiments were performed in a porcine model of AV dromotropathy. In a proof-of-principle clinical study, left ventricular (LV) pressure and volume were measured in 22 heart failure (HF) patients (LV ejection fraction <35%) with prolonged PR interval (>230 ms) and narrow or non-left bundle branch block QRS complex. Computer simulations and animal studies in normal hearts showed that restoring of AV-coupling with unchanged ventricular activation sequence significantly increased LV filling, mean arterial pressure, and cardiac output by 10-15%. In computer simulations of failing hearts and in HF patients, reducing PR interval by biventricular (BiV) pacing (patients: from 300 ± 61 to 137 ± 30 ms) resulted in significant increases in LV stroke volume and stroke work (patients: 34 ± 40% and 26 ± 31%, respectively). However, worsening of ventricular dyssynchrony by using right ventricular (RV) pacing abrogated the benefit of restoring AV-coupling. In model simulations, animals and patients, the increase of LV filling and associated improvement of LV pump function coincided with both larger mitral inflow (E- and A-wave area) and reduction of diastolic mitral regurgitation.

CONCLUSION

Restoration of AV-coupling by BiV pacing in normal and failing hearts with prolonged AV conduction leads to considerable haemodynamic improvement. These results indicate that BiV or physiological pacing, but not RV pacing, may improve cardiac function in patients with HF and prolonged PR interval.

Physiology and Practicality of Left Ventricular Septal Pacing

Left ventricular septal pacing (LVSP) and left bundle branch pacing (LBBP) have been introduced to maintain or correct interventricular and intraventricular (dys)synchrony. LVSP is hypothesised to produce a fairly physiological sequence of activation, since in the left ventricle (LV) the working myocardium is activated first at the LV endocardium in the low septal and anterior free-wall regions. Animal studies as well as patient studies have demonstrated that LV function is maintained during LVSP at levels comparable to sinus rhythm with normal conduction. Left ventricular activation is more synchronous during LBBP than LVSP, but LBBP produces a higher level of intraventricular dyssynchrony compared to LVSP. While LVSP is fairly straightforward to perform, targeting the left bundle branch area may be more challenging. Long-term effects of LVSP and LBBP are yet to be determined. This review focuses on the physiology and practicality of LVSP and provides a guide for permanent LVSP implantation.

Left Ventricular Lead Placement Guided by Reduction in QRS Area

Background: Reduction in QRS area after cardiac resynchronization therapy (CRT) is associated with improved long-term clinical outcome. The aim of this study was to investigate whether the reduction in QRS area is associated with hemodynamic improvement by pacing different LV sites and can be used to guide LV lead placement. Methods: Patients with a class Ia/IIa CRT indication were prospectively included from three hospitals. Acute hemodynamic response was assessed as the relative change in maximum rate of rise of left ventricular (LV) pressure (%∆LVdP/dt_max). Change in QRS area (∆QRS area), in QRS duration (∆QRS duration), and %∆LVdP/dt_max were studied in relation to different LV pacing locations within a patient. Results: Data from 52 patients paced at 188 different LV pacing sites were investigated. Lateral LV pacing resulted in a larger %∆LVdP/dt_max than anterior or posterior pacing (p = 0.0007). A similar trend was found for ∆QRS area (p = 0.001) but not for ∆QRS duration (p = 0.23). Pacing from the proximal electrode pair resulted in a larger %∆LVdP/dt_max (p = 0.004), and ∆QRS area (p = 0.003) but not ∆QRS duration (p = 0.77). Within patients, correlation between ∆QRS area and %∆LVdP/dt_max was 0.76 (median, IQR 0.35; 0,89). Conclusion: Within patients, ∆QRS area is associated with %∆LVdP/dt_max at different LV pacing locations. Therefore, QRS area, which is an easily, noninvasively obtainable and objective parameter, may be useful to guide LV lead placement in CRT.

Association of ECG characteristics with clinical and echocardiographic outcome to CRT in a non-LBBB patient population

PURPOSE

Effectiveness of cardiac resynchronization therapy (CRT) in patients without left bundle branch block (non-LBBB) QRS morphology is limited. Additional selection criteria are needed to identify these patients.

METHODS

Seven hundred ninety consecutive patients with non-LBBB morphology, who received a CRT-device in 3 university centers in the Netherlands, were selected. Pre-implantation 12-lead ECGs were evaluated on morphology, duration, and area of the QRS complex, as well as on PR interval, left ventricular activation time (LVAT), and the presence of fragmented QRS (fQRS). Association of these ECG features with the primary endpoint: a combination of left ventricular assist device (LVAD) implantation, cardiac transplantation and all-cause mortality, and secondary endpoint-echocardiographic reduction of left ventricular end-systolic volume (LVESV)-were evaluated.

RESULTS

The primary endpoint occurred more often in non-LBBB patients with with PR interval ≥ 230ms, QRS area < 109μVs, and with fQRS. Multivariable regression analysis showed independent associations of QRS area (HR 2.33 [1.44, 3.77], p = 0.001) and PR interval (HR 2.03 [1.51, 2.74], p < 0.001) only. Mean LVESV reduction was significantly lower in patients with baseline RBBB, QRS duration < 150 ms, PR interval ≥ 230 ms, and in QRS area < 109 μVs. Multivariable regression analyses only showed significant associations between QRS area ≥ 109 μVs (OR 2.00 [1.09, 3.66] p = 0.025) and probability of echocardiographic response to CRT.

CONCLUSIONS

In the heterogeneous non-LBBB patient population, QRS area and PR prolongation rather than traditional QRS duration and morphology are associated to both clinical and echocardiographic outcomes of CRT.

P5682Cardiac resynchronization therapy with a single left ventricular septal pacing electrode: acute hemodynamic and electrophysiological effects

Background

Cardiac resynchronization therapy (CRT) is usually performed with a right (RV) and left ventricular (LV) lead. In a previous patient study, pacing the interventricular septum permanently on the LV endocardial side (LV septum) proved feasible in patients with sinus node dysfunction.

Objective

To investigate the effects of LV septal pacing as compared to conventional biventricular (BiV) pacing with respect to acute hemodynamic and electrophysiological effects in CRT indicated heart failure patients.

Methods

Temporary LV septal pacing (transarterial approach) and pacing in the conventional BiV mode using the implanted leads was performed in 26 patients (QRS duration 163±17 ms, 23 left bundle branch block patients) undergoing CRT implantation. Acute hemodynamic response (relative to baseline AAI pacing) was assessed by LVdP/dtmax. Multi-electrode body-surface mapping, what has been used previously to characterize electrical dyssynchrony in CRT patients, was evaluated using the standard deviation of activation times (SDAT) (figure, right panel).

Results

LV septal pacing resulted in a significant LV dP/dtmax increase, that was comparable to conventional BiV pacing (figure, left panel). Combined RV and LV septal pacing did not provide an additional increase. LV septal pacing resulted in a significantly larger reduction in SDAT than RV plus LV septal pacing and conventional BiV pacing (figure, middle panel).

Conclusions

LV septal pacing results in acute hemodynamic improvement and electrical resynchronization that is at least as good as conventional BiV pacing. These results suggest that LV septal pacing with a single ventricular lead may serve as an alternative to conventional BiV pacing for cardiac resynchronization.

Acknowledgement/Funding

Medtronic is a subsidising party.

P4532PR interval prolongation, still a marker of worse outcome in patients treated with cardiac resynchronization therapy

Background

Patients without left bundle branch block (non-LBBB) generally derive little benefit from CRT. Recently, CRT has been suggested to be beneficial in patients with prolonged PR interval. However in the general HF population, the presence of prolonged PR interval is associated with worse outcome.

Purpose

To evaluate the association of a prolonged PR interval with clinical outcome in CRT-treated LBBB and non-LBBB patients.

Methods

Pre-implantation 12-lead ECGs from 1.245 consecutive CRT patients without atrial fibrillation from 3 implanting centres in the Netherlands were evaluated for the presence of LBBB QRS morphology and PR interval prolongation (≥230ms). The primary endpoint was the combination of left ventricular assist device implantation, cardiac transplantation and all-cause mortality.

Results

Patients with LBBB (n=620) showed a significantly shorter mean PR interval than non-LBBB patients (n=625) (187ms vs 198ms, p<0.001). Prolonged PR interval was found in 12.6% of patients with LBBB and 19.2% of non-LBBB patients (P<0.001). In non-LBBB patients with PR prolongation event rate was significantly higher (54 vs 34%, p<0.001). In LBBB patients there was a non-significant difference (28 vs 20%, p=0.1). Regression analyses (figure 1) showed similar results, with a significantly higher odds of experiencing an event in non-LBBB patients with PR prolongation (HR 2.24 [1.68, 2.99], p<0.001), and a trend to significantly higher odds in LBBB patients with PR prolongation (HR 1.61 [1.02, 2.56], p=0.04)

Figure 1

Conclusion

In HF patients treated with CRT, PR prolongation is negatively associated with long term clinical outcome. The association seems to be stronger in non-LBBB patients than in LBBB patients.

Acknowledgement/Funding

None

Endocardial pacing results in better electrical resynchronization and hemodynamic improvement than epicardial pacing in CRT

Funding Acknowledgements

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): The original study was financially supported by Medtronic (Minneapolis, Minnesota). The investigation of the current abstract is unrelated to the original financial support.

Background

Cardiac resynchronization therapy (CRT) is conventionally applied by means of a transvenous epicardial left ventricular (LV) lead. Studies suggest that endocardial LV pacing may result in better resynchronization and LV function than epicardial LV pacing.

Purpose

To investigate whether endocardial pacing results in better electrical resynchronization and hemodynamic improvement compared to epicardial pacing.

Methods

Patients with an indication for CRT were prospectively included from two hospitals. In all patients, LV pacing was performed endocardially and epicardially in the postero-lateral region. QRS area was calculated from vectorcardiograms that were synthesized from 12-lead ECGs. Acute hemodynamic improvement was assessed as the change in maximum rate of rise of LV-pressure (%ΔLVdP/dtmax). We assessed the effects of endocardial and epicardial LV pacing on the change in QRS area (∆QRS area) and LVdP/dtmax (%ΔLVdP/dtmax).

Results

A total of 16 patients (age 66 ± 11 years, 56% male, 31% ischemic cardiomyopathy, QRS duration 166±18ms, LBBB in 88%) were included. Endocardial pacing resulted in greater ∆QRS area than epicardial pacing (-51 ± 34 µVs vs. -24 ± 37 µVs, p = 0.021, Panel A). In addition, endocardial pacing led to a larger %ΔLVdP/dtmax as compared to epicardial pacing (21 ± 12% vs. 18 ± 9%, p = 0.025, Panel B).

Conclusion

Compared to conventional epicardial LV pacing in CRT, endocardial LV pacing results in better electrical resynchronization and acute hemodynamic improvement.

Reduction in QRS area correlates with hemodynamic response during CRT-device implantation

Funding Acknowledgements

Type of funding sources: None.

Background Previous studies have shown that reduction in QRS area after cardiac resynchronization therapy (CRT) is associated with improved long-term clinical outcome.

Purpose To investigate whether reduction in QRS area is associated with hemodynamic improvement and whether QRS area reduction could be used for CRT optimization, with respect to LV lead position and device programming in individual patients.

Methods A total of 78 patients with indication for CRT were prospectively included in 4 hospitals. QRS area was calculated from vectorcardiograms that were synthesized from 12-lead ECG’s. Acute hemodynamic response was assessed invasively as the maximum rate of percentual left ventricular (LV) pressure (%LVdP/dtmax) rise.  QRS area reduction was studied in relation to LV-lead position (n = 26), proximal versus distal LV lead position (n = 27), and VV-delay (n = 25).

Results Combining all measurements in all patients showed a significant correlation between QRS area reduction and %LVdP/dTmax increase (R = 0.49, P &lt; 0.0001).  Also, when one fixed routine implantation setting was used for each patient (lateral lead position, distal, AV-delay 120-150ms, VV-delay 0ms) this correlation was present (R = 0.45, p &lt; 0.0001, figure panel A). In 21 patients in which at least 3 lead positions were available there was also a significant correlation between QRS area reduction and %LVdP/dtmax increase (average R = 0.69, p &lt; 0.0001, panel B). For VV-delay, 25 other patients as well showed a significant correlation (average R = 0.53, p &lt; 0.0001).

Conclusion Within patients, QRS area reduction is associated with %LVdP/dtmax increase with various LV lead positions and VV-intervals. Therefore, QRS area, which is an easily obtainable and objective parameter, might be a promising tool for optimization of LV lead position and device programming in CRT. Abstract Figure.

P6016His bundle pacing versus biventricular pacing in cardiac resynchronization therapy: acute hemodynamic and electrophysiological effects

Background

Cardiac resynchronization therapy (CRT) is usually performed with a right (RV) and left ventricular (LV) lead. Previous observational studies showed promising results with His bundle pacing (HBP) in patients with left bundle branch block (LBBB) by capturing and recruiting the native His-Purkinje system as an alternative to provide ventricular resynchronization.

Objective

To investigate the effects of HBP as compared to conventional biventricular (BiV) pacing with respect to acute hemodynamic and electrophysiological effects in heart failure patients with LBBB.

Methods

RV apical and BiV pacing, using the implanted leads, and temporary HBP, using an electrophysiology catheter, was performed in 13 patients (QRS duration 168±16 ms) undergoing CRT implantation. Hemodynamic response (relative to baseline AAI pacing) was assessed as change in LVdP/dtmax. Multi-electrode body-surface mapping, what has been used previously to characterize electrical dyssynchrony in CRT patients, was evaluated using the standard deviation of activation times (SDAT) (figure, right panel).

Results

HBP resulted in a significant LV dP/dtmax increase, that was comparable to the increase during BiV pacing and significantly larger than RV pacing (figure, left panel). HBP resulted in a more homogenized electrical activation and larger reduction in SDAT than both conventional BiV pacing and RV pacing (figure, middle panel).

Conclusions

Acute HBP results in hemodynamic improvement and electrical resynchronization that is as good as conventional BiV pacing. These results suggest that HBP may serve as an alternative for conventional BiV pacing in LBBB patients, however prospective studies are needed to prove chronic clinical outcomes.

Acknowledgement/Funding

Medtronic is a subsidising party.

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) &lt;35% and PR interval ≥230 ms, without evident prolonged QRS duration &gt;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&lt;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.