Permanent direct his bundle pacing does not induce ventricular dyssynchrony unlike conventional right ventricular apical pacing. An intrapatient acute comparison study

Physiological cardiac pacing: Current status

Adverse hemodynamics of right ventricular (RV) pacing is a well-known fact. It was believed to be the result of atrio-ventricular (AV) dyssynchrony and sequential pacing of the atrium and ventricle may solve these problems. However, despite maintenance of AV synchrony, the dual chamber pacemakers in different trials have failed to show its superiority over single chamber RV apical pacing in terms of death, progression of heart failure, and atrial fibrillation (AF). As a consequence, investigators searched for alternate pacing sites with a more physiological activation pattern and better hemodynamics. Direct His bundle pacing and Para-Hisian pacing are the most physiological ventricular pacing sites. But, this is technically difficult. Ventricular septal pacing compared to apical pacing results in a shorter electrical activation delay and consequently less mechanical dyssynchrony. But, the study results are heterogeneous. Selective site atria pacing (atrial septal) is useful for patients with atrial conduction disorders in prevention of AF.

Feasibility and Acute Hemodynamic Effect of Left Ventricular Septal Pacing by Transvenous Approach Through the Interventricular Septum

BACKGROUND

Left ventricular septal (LVS) pacing reduces ventricular dyssynchrony and improves cardiac function relative to right ventricular apex (RVA) pacing in animals. We aimed to establish permanent placement of an LVS pacing lead in patients using a transvenous approach through the interventricular septum.

METHODS AND RESULTS

Ten patients with sinus node dysfunction scheduled for dual-chamber pacemaker implantation were prospectively enrolled. A custom pacing lead with extended helix was introduced via the left subclavian vein and, after positioning against the right ventricular septum (RVS) using a preshaped guiding catheter, driven through the interventricular septum to the LVS. The acute hemodynamic effect of RVA, RVS, and LVS pacing was evaluated by invasive LVdP/dtmax measurements. The lead was successfully delivered to the LVS in all patients. Procedure time and fluoroscopy time shortened with experience. QRS duration was shorter during LVS pacing (144 ± 20 ms) than during RVA (172 ± 33 ms; P = 0.02 versus LVS) and RVS pacing (165 ± 17 ms; P = 0.004 versus LVS). RVA and RVS pacing reduced LVdP/dtmax compared with baseline atrial pacing (-7.1 ± 4.1% and -6.9 ± 4.3%, respectively), whereas LVS pacing maintained LVdP/dtmax at baseline level (1.0 ± 4.3%; P = 0.001 versus RVA and RVS). R-wave amplitude and pacing threshold were 12.2 ± 6.7 mV and 0.5 ± 0.2 V at implant and remained stable during 6-month follow-up without lead-related complications.

CONCLUSIONS

Permanent placement of an LVS pacing lead by transvenous approach through the interventricular septum is feasible in patients. LVS pacing preserves acute left ventricular pump function. This new pacing method could serve as an alternative and hemodynamically preferable approach for antibradycardia pacing.

Successful resynchronization by permanent His-bundle pacing in a patient with pacing-induced cardiomyopathy

Right ventricular (RV) pacing has been reported to result in ventricular dyssynchrony, heart failure, and increased mortality. Pacing associated deterioration of left ventricular (LV) systolic function has been termed pacing-induced cardiomyopathy (PICM). While upgrading to biventricular pacing (BiVP) is an effective therapy for PICM, permanent His-bundle pacing (HBP) can be a physiological alternative to BiVP. We present a patient with PICM who responded dramatically to permanent HBP.

Atrioventricular Optimized Direct His Bundle Pacing Improves Acute Hemodynamic Function in Patients With Heart Failure and PR Interval Prolongation Without Left Bundle Branch Block

OBJECTIVES

The purpose of this study was to investigate whether heart failure patients with narrow QRS duration (or right bundle branch block) but with long PR interval gain acute hemodynamic benefit from atrioventricular (AV) optimization. We tested this with biventricular pacing and (to deliver pure AV shortening) direct His bundle pacing.

BACKGROUND

Benefits of pacing for heart failure have previously been indicated by acute hemodynamic studies and verified in outcome studies. A new target for pacing in heart failure may be PR interval prolongation, which is associated with 58% higher mortality regardless of QRS duration.

METHODS

We enrolled 16 consecutive patients with systolic heart failure, PR interval prolongation (mean, 254 ± 62 ms) and narrow QRS duration (n = 13; mean QRS duration: 119 ± 17 ms) or right bundle branch block (n = 3; mean, QRS duration: 156 ± 18 ms). We successfully delivered temporary direct His bundle pacing in 14 patients and temporary biventricular pacing in 14 participants. We performed AV optimization using invasive systolic blood pressure obtaining parabolic responses (mean R²: 0.90 for His, and 0.85 for biventricular pacing).

RESULTS

The mean increment in systolic BP compared with intrinsic ventricular conduction was 4.1 mm Hg (95% confidence interval [CI]: +1.9 to +6.2 mm Hg for His and 4.3 mm Hg [95% CI: +2.0 to +6.5 mm Hg] for biventricular pacing. QRS duration lengthened with biventricular pacing (change = +22 ms [95% CI: +18 to +25 ms]) but not with His pacing (change = +0.5 ms [95% CI: -2.6 to +3.6 ms).

CONCLUSIONS

AV-optimized pacing improves acute hemodynamic function in patients with heart failure and long PR interval without left bundle branch block. That it can be achieved by single-site His pacing shows that its mechanism is AV shortening. The improvement is ∼60% of the effect size previously reported for biventricular pacing in left bundle branch block. Randomized, blinded trials are warranted to test for long-term beneficial effects.

Honing in on optimal ventricular pacing sites: an argument for his bundle pacing

OPINION STATEMENT

Frequent ventricular pacing is often or completely unavoidable in patients with high-grade or complete heart block. Over time, patients with high-burden RV pacing are at risk for developing symptomatic cardiomyopathy due to pacing-induced ventricular dyssynchrony. Growing awareness of this concern has generated interest in alternative pacing sites like the septum and outflow tract, the thinking being that these sites will more closely mimic His-Purkinje-mediated ventricular activation. Numerous studies have met with mixed results likely due to the fact that-to quote Marvin Gaye-there ain't nothing like the real thing. Herein lies the advantage of His bundle pacing (HBP), as it is the only pacing modality capable of physiological ventricular activation. HBP has been demonstrated to be safe and reliable in various forms of AV block with minimal drawbacks, namely modestly higher pacing thresholds when compared with other RV sites. Additionally, HBP is a truly physiologic alternative to biventricular pacing to effect cardiac resynchronization therapy (CRT), a concept supported by small observational and prospective studies. In our view, His bundle pacing should be considered in nearly all patients requiring ventricular pacing.

Chronic right ventricular apical pacing: adverse effects and current therapeutic strategies to minimize them

The permanent cardiac pacemaker is the only effective therapy for patients with symptomatic bradycardia and hundreds of millions are implanted worldwide every year. Despite its undisputed clinical benefits, the last two decades have drawn much attention to the negative effects associated with long-term pacing of the right ventricle (RV). Experimental and clinical studies have shown that RV pacing produces ventricular dyssynchrony, similar to that of left bundle branch block, with consequent detrimental effects on cardiac structure and function, with adverse clinical outcomes such as atrial fibrillation, heart failure and death. Although clinical evidence largely comes from subanalyses of pacemaker and implantable cardiac defibrillator studies, there is strong evidence that patients with reduced left ventricular function are at high risk of suffering from the detrimental effects of long-term RV pacing. Biventricular pacing in cardiac resynchronization therapy devices can prevent ventricular dyssynchrony and has emerged as an attractive option in this patient group with promising results and more clinical studies underway. Moreover, there is evidence that specific pacemaker algorithms that minimize RV pacing can reduce the negative effects of RV stimulation on cardiac function and may also prevent clinical deterioration. The extent of the long-term clinical effects of RV pacing in patients with normal ventricular function and how to prevent this are less clear and subject to future investigation.

The importance of avoiding unnecessary right ventricular pacing in clinical practice

Symptomatic bradycardia is effectively treated with the implantation of a cardiac pacemaker. Although a highly successful therapy, during recent years there has been a focus on the negative effects associated with long-term pacing of the apex of the right ventricle (RV). It has been shown in both experimental and clinical studies that RV pacing leads to ventricular dyssynchrony, similar to that of left bundle branch block, with subsequent detrimental effects on cardiac structure and function, and in some cases adverse clinical outcomes such as atrial fibrillation, heart failure and death. There is substantial evidence that patients with reduced left ventricular function (LVEF) are at particular high risk of suffering the detrimental clinical effects of long-term RV pacing. The evidence is, however, incomplete, coming largely from subanalyses of pacemaker and implantable cardiac defibrillator studies. In this group of patients with reduced LVEF and an expected high amount of RV pacing, biventricular pacing (cardiac resynchronization therapy) devices can prevent the negative effects of RV pacing and reduce ventricular dyssynchrony. Therefore, cardiac resynchronization therapy has emerged as an attractive option with promising results and more clinical studies are underway. Furthermore, specific pacemaker algorithms, which minimize RV pacing, can also reduce the negative effects of RV stimulation on cardiac function and may prevent clinical deterioration.

Permanent His-bundle pacing maintains long-term ventricular synchrony and left ventricular performance, unlike conventional right ventricular apical pacing

AIMS

Right ventricular apical pacing (RVAP) may be deleterious, determining abnormal left ventricular (LV) electrical activation and progressive LV dysfunction. Permanent His-bundle pacing (HBP) has been proposed to prevent this detrimental effect. The aim of our study was to compare the long-term effects of HBP on LV synchrony and systolic performance with those of RVAP in the same group of patients.

METHODS

Our analysis included 26 patients who received both an HBP lead and an RVAP lead, as backup, in our electrophysiology laboratory between 2004 and 2007. After implantation, all devices were programmed to obtain HBP. An intra-patient comparison of the effects of HBP and RVAP on LV dyssynchrony and function was performed at the last available follow-up examination.

RESULTS

After a mean of 34.6 ± 11 months, the pacing modality was temporarily switched to RVAP. During RVAP, LV ejection fraction significantly decreased (50.1 ± 8.8% vs. 57.3 ± 8.5%, P < 0.001), mitral regurgitation significantly increased (22.5 ± 10.9% vs.16.3 ± 12.4%; P = 0.018), and inter-ventricular delay significantly worsened (33.4 ± 19.5 ms vs. 7.1 ± 4.7 ms, P = 0.003) in comparison with HBP. However, the myocardial performance index was not statistically different between the two pacing modalities (P = 0.779). No asynchrony was revealed by tissue Doppler imaging during HBP, while during RVAP the asynchrony index was significantly higher in both the four-chamber (125.8 ± 63.9 ms; P = 0.035 vs. HBP) and two-chamber (126 ± 86.5 ms; P = 0.037 vs. HBP) apical views.

CONCLUSION

His-bundle pacing has long-term positive effects on inter- and intra-ventricular synchrony and ventricular contractile performance in comparison with RVAP. It prevents asynchronous pacing-induced LV ejection fraction depression and mitral regurgitation.

Direct His bundle and paraHisian cardiac pacing

The success rate of direct His bundle pacing (DHBP) and paraHisian pacing has improved remarkably in the last 3-5 years with the advent of dedicated fixation systems that have reduced procedural duration, dislodgement rate, and fluoroscopy time. The methodology of DBHP remains still more complex than paraHisian pacing and is associated with high-pacing thresholds. Thus, DHBP entails greater battery current drain and reduced device longevity. A shift toward paraHisian pacing (which is fusion pacing of myocardium and His bundle) has occurred because its implementation is easier and the electrical parameters are superior to those of DBHP. Currently, an additional safety lead is inserted at the RV apex or outflow tract to prevent asystole, especially in patients with pure DHBP. It is often possible to avoid a safety lead with paraHisian pacing because ventricular pacing is virtually assured on a long-term basis via myocardial capture. DBHP and paraHisian pacing can be achieved in a substantial proportion of patients with varying grades of narrow QRS AV block or after AV junctional ablation and in some patients with the ECG manifestation of bundle branch block caused by an intraHisian lesion. Preliminary observations suggest that DHBP may be useful in some patients requiring cardiac resynchronization if it produces a narrow QRS complex because the site of an intraHisian lesion responsible for left bundle branch block is above the site of DHBP.

Left ventricular performance during para-His pacing in patients with high-grade atrioventricular block: an acute study

AIM

To compare changes in left ventricular (LV) performance and mechanical synchrony between atrial-based pacing with intrinsic conduction (AAI), dual-chamber para-His Pacing (DDD-PHP) and dual-chamber right ventricular septal pacing (DDD-RVS) in patients with high-grade atrioventricular block (AVB).

METHODS AND RESULTS

Patients with high-grade AVB and QRS <120 ms, who had temporary intrinsic atrioventricular (AV) conduction the day after the implantation were included in the study. All patients received a biventricular pacemaker with a para-His lead in the LV port, and a RVS lead in the right ventricular port. Left ventricular three-dimensional echocardiograms, LV outlet tract-velocity time integrals (LVOT-VTI), and LV synchrony with tissue Doppler imaging were recorded during AAI, DDD-PHP, and DDD-RVS. Eleven patients were included. The mean LVOT-VTI was significant lower during DDD-RVS (19.2 ± 5.5 cm) as compared with DDD-PHP (21.4 ± 5.5 cm), P = 0.006 and AAI (21.6 ± 6.8 cm), P = 0.016. The LVEF was higher during AAI than during DDD-PHP (P= 0.02) and DDD-RVS (P< 0.01). The maximal time to peak velocity between basal segments was significant longer with DDD-RVS (95 ± 26 ms) than with AAI (72 ± 30 ms), P = 0.028, whereas no difference was observed between AAI and DDD-PHP (81 ± 42 ms), P = 0.20.

CONCLUSIONS

Acutely, DDD-PHP preserves LV systolic performance and mechanical synchrony as compared with DDD-RVS.

Evolutionary innovations in cardiac pacing

Cardiac pacing has played a significant role in mitigating morbidity and mortality associated with bradyarrhythmias. Throughout the years, advances made in battery reliability, lead performance, and device portability have rapidly expanded the use of cardiac pacemakers in many different disease states. Despite the benefits, there has been growing awareness of the potential deleterious effects of long-term artificial electrical stimulation including the development of ventricular dyssynchrony and atrial fibrillation. Given their association with an increased risk for heart failure and possibly death, several advances aimed at minimizing them have been made in recent years including changes in atrioventricular pacing algorithms, novel pacing mode modifications, and better identification of hemodynamically optimal pacing sites. This article reviews the advances made and the future direction of innovations in cardiac pacing.

His and para-His pacing in AV block: feasibility and electrocardiographic findings

PURPOSE

Right ventricular apical pacing induces a dyssynchronous activation of the left ventricle and is associated with adverse clinical outcome. We aimed to establish permanent His-bundle pacing or para-His pacing in patients with high-grade atrioventricular (AV) block.

METHOD

We included patients with pacemaker indication due to second- or third-degree AV block, left ventricular ejection fraction >0.40, QRS duration <120 ms, and sinus rhythm. All patients received a pacemaker with one atrial lead, one right ventricular mid-septal lead, and one lead in the His bundle or in the para-His position. Pacing from apex was performed temporarily. Patients were followed for 12 months.

RESULTS

Thirty-eight patients were included (mean age, 67 ± 10 years; 30 (79%) male). Mean implantation time was 85 ± 31 min, mean fluoroscopy time was 23 ± 13 min, and mean position attempts of the His bundle lead was 8 ± 5. In four patients, we established direct His-bundle pacing with a mean QRS of 100 ± 19 ms, and in 28 patients, para-His pacing was achieved with a mean QRS of 112 ± 18 ms, and in six patients, neither direct His-bundle pacing or para-His pacing could be achieved. The mean QRS duration was 153 ± 12 ms with mid-septal pacing and 161 ± 15 ms with apical pacing.

CONCLUSION

Stable direct His-bundle pacing or para-His pacing is feasible in 85% of patients with narrow QRS and high-grade AV block and leads to a normal or near-normal ventricular activation pattern.

Future easy and physiological cardiac pacing

The right atrial appendage (RAA) and right ventricular apex (RVA) have been widely considered as conventional sites for typical dual-chamber atrio-ventricular cardiac (DDD) pacing. Unfortunately conventional RAA pacing seems not to be able to prevent atrial fibrillation in DDD pacing for tachycardia-bradycardia syndrome, and the presence of a left bundle branch type of activation induced by RVA pacing can have negative effects. A new technology with active screw-in leads permits a more physiological atrial and right ventricular pacing. In this review, we highlight the positive effects of pacing of these new and easily selected sites. The septal atrial lead permits a shorter and more homogeneous atrial activation, allowing better prevention of paroxysmal atrial fibrillation. The para-Hisian pacing can be achieved in a simpler and more reliable way with respect to biventricular pacing and direct Hisian pacing. We await larger trials to consider this "easy and physiological pacing" as a first approach in patients who need a high frequency of pacing.

Ventricular resynchronization by implementation of direct his bundle pacing in a patient with congenital complete AV block and newly diagnosed cardiomyopathy

Congenital complete atrioventricular block (CCAVB) is usually due to failure of AV nodal conduction with preservation of the His Purkinje system, typically present at birth. While most patients with CCAVB ultimately require pacemaker therapy to restore physiologic heart rates, recent studies have suggested that chronic right ventricular (RV) pacing in patients with CCAVB can have detrimental effects on cardiac structure and function, and may account for a 7-10% incidence of congestive heart failure in these patients. Since the His Purkinje system is preserved in CCAVB, this patient population could be uniquely well served by direct His bundle pacing (DHBP) which would be expected to restore physiologic activation of both ventricles. We present a case of a young woman who presented with RV pacing-induced cardiomyopathy who responded dramatically to DHBP.

Safety and performance of a system specifically designed for selective site pacing

INTRODUCTION

In the right ventricle, selective site pacing (SSP) has been shown to avoid detrimental hemodynamic effects induced by right ventricular apical pacing and, in the right atrium, to prevent the onset of atrial fibrillation and to slow down disease progression. The purpose of our multicenter observational study was to describe the use of a transvenous 4-French catheter-delivered lead for SSP in the clinical practice of a large number of centers.

METHODS

We enrolled 574 patients in whom an implantable device was indicated. In all patients, SSP was achieved by using the Select Secure System™ (Medtronic Inc., Minneapolis, MN, USA).

RESULTS

In 570 patients, the lead was successfully implanted. In 125 patients, atrial SSP was performed: in 75 (60%) the lead was placed in the interatrial septum, in 31 (25%) in the coronary sinus ostium, and in 19 (15%) in the Bachman bundle. Ventricular SSP was undertaken in 138 patients: in 105 (76%) the high septal right ventricular outflow tract (RVOT) position was paced, in seven (5%) the high free-wall RVOT, in 25 (18%) the low septal RVOT, and in one (1%) the low free-wall RVOT. In the remaining 307 patients, the His zone was paced: in 87 (28%) patients, direct His-bundle pacing and in 220 (72%) patients para-hisian pacing was achieved. Adequate pacing parameters and a lead-related complication rate of 2.6% were recorded during a follow-up of 20 ± 10 months.

CONCLUSIONS

Our results demonstrated that many sites, in the right atrium, in the right ventricle, and in His-bundle region, can be paced using the Select Secure System™.

Permanent His-bundle pacing: seeking physiological ventricular pacing

AIMS

Right ventricular apical pacing can have deleterious effects and the His bundle has been widely reported to be an alternative site. This paper presents our experience with permanent His-bundle pacing (HBP).

METHODS AND RESULTS

Patients referred for pacemaker implants (regardless of block type) were screened to determine if temporary HBP corrected conduction dysfunctions (threshold < or =2.5 V for 1 ms) and provided infra-Hisian 1:1 conduction of at least 120 s/m. Of the 182 patients selected, HBP corrected conduction dysfunctions in 133 (73%) patients, 42 (32%) of whom were rejected for the permanent procedure due to high thresholds. His-bundle lead implantation was attempted in the remaining 91 patients and was successful in 59 (65% of all attempts, 44% of all possible cases).

CONCLUSION

In some patients, permanent HBP may be an alternative to right ventricular apical pacing.

The role of speckle tracking strain imaging in cardiac pacing

In recent years, concerns have been raised about possible harmful effects of long-term right ventricular (RV) apical pacing. These detrimental effects may be related to changes in left ventricular (LV) mechanics during RV apical pacing. As a consequence, alternative RV pacing sites have been proposed, and in selected patients an upgrade from RV to biventricular pacing may be considered. Novel two-dimensional (2D) speckle tracking strain imaging allows detailed evaluation of LV mechanics, including LV mechanical dyssynchrony, LV strain and LV torsion. In this review, the role of speckle tracking strain imaging in the evaluation of LV function in patients with RV apical pacing will be reviewed. The effects of RV apical pacing on LV mechanical dyssynchrony, LV strain and LV torsion will be discussed. In addition, the role of speckle tracking strain imaging in the selection of the optimal (alternative) RV pacing site and in the selection of patients who may benefit from an upgrade from RV apical pacing to biventricular pacing will be reviewed.

[Is resynchronization therapy necessary when optimizing right ventricular stimulation?]

Cardiac resynchronization therapy (CRT) using biventricular stimulation is hampered by coronary venous imponderabilities, complex implantation procedures, technical malfunctions and complications as well as disappointing responder rates. Despite its pathophysiological soundness and some initial success, the use of AV sequential pacing for the treatment of heart failure has been abandoned because right ventricular (RV) apical stimulation may be detrimental for cardiac mechanics, may worsen heart failure and may increase mortality. Attempts at avoiding desynchronizing effects and improving hemodynamics by pacing from alternative RV sites have been numerous but not convincing. Whether patients with left ventricular dysfunction or overt heart failure may benefit from pacing the RV outflow tract or septum, from dual site RV or His bundle stimulation instead of left ventricular based resynchronization is the topic of this review.

[His-bundle stimulation and alternative RV stimulation sites]

The increasing evidence that right ventricular (RV) apical stimulation is detrimental for cardiac mechanics and increases the risk of new onset heart failure and mortality promotes strategies to avoid ventricular pacing and - if not applicable due to atrioventricular block - stipulates the search for alternative techniques of pacing the heart from the right ventricle. Despite more than 15 years of clinical research it remains unclear whether pacing from the right ventricular outflow tract or septum, dual site RV stimulation or selective pacing of the His bundle results in hemodynamic and prognostic benefit over the traditional method of apical RV pacing. The article reviews pertinent literature and tries to demonstrate pathophysiological mechanisms.

Acute pacing-induced dyssynchronous activation of the left ventricle creates systolic dyssynchrony with preserved diastolic synchrony

INTRODUCTION

Patients with heart block have conventionally received a pacemaker that stimulates the right ventricular apex (RVA) to restore heart rate control. While RVA pacing has been shown to create systolic dyssynchrony acutely, dyssynchrony can also occur in diastole. The effects of acute RVA pacing on diastolic synchrony have not been investigated. RVA pacing acutely impairs diastolic function by increasing the time constant of relaxation, decreasing the peak lengthening rate and decreasing peak negative dP/dt. We therefore hypothesized that acute RVA pacing would cause diastolic dyssynchrony in addition to creating systolic dyssynchrony.

METHODS AND RESULTS

Fourteen patients (13 +/- 4 years old) with non-preexcited supraventricular tachycardia underwent ablation therapy with subsequent testing to confirm elimination of the tachycardia substrate. Normal cardiac structure and function were then documented on two-dimensional echocardiography and 12-lead electrocardiography prior to enrollment. Tissue Doppler images were collected during normal sinus rhythm (NSR), right atrial appendage pacing (AAI), and VVI-RVA pacing during the postablation waiting interval. Systolic and diastolic dyssynchrony were quantified using cross-correlation analysis of tissue Doppler velocity curves. Systolic dyssynchrony increased 81% during RVA pacing relative to AAI and NSR (P < 0.01). Diastolic synchrony was not affected by the different pacing modes (P = 0.375).

CONCLUSION

Acute dyssynchronous activation of the LV created by RVA pacing resulted in systolic dyssynchrony with preserved diastolic synchrony in pediatric patients following catheter ablation for treatment of supraventricular tachycardia. Our results suggest that systolic and diastolic dyssynchrony are not tightly coupled and may develop through separate mechanisms.