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.     

Permanent HIS bundle Pacing Feasibility in Routine Clinical Practice: Experience from an Indian Center

There is a paucity of experience regarding His bundle pacing (HBP) at laboratories initially attempting the procedure, especially in the Indian scenario. Patient who underwent HBP were selected for pacing therapy or in lieu of cardiac resynchronization therapy (CRT) at a single center. Among 22 patients attempted, 19 patients underwent successful implant, achieving selective HBP in 14 patients. There was a significant improvement in left ventricular ejection fraction (LVEF) (49.3 ± 9.3 vs. 36.7 ± 9.2) in the LV dysfunction subgroup (n = 6). Over a follow-up of 15 ± 6.5 months, thresholds were stable in all except one patient, and there was no requirement of lead revision. In summary, we found that HBP is a feasible option for achieving physiological pacing.     

三极起搏法及其在经食管心房起搏术中的应用价值

为克服现行经食管心房起搏术中常见缺点,作者试用三极起搏法。实验表明:就降低起搏阈值、减小脉冲幅度而沦,三极起搏法显著低于常规二极起搏法;以减轻受检者痛苦,保持起搏稳定为目的,三极起搏法中双正极法明显优于双负极法。双正极法还有图形整洁、起搏P波清晰、方法尤为简便等优点,在经食管心房起搏检查中有其一定的实用价值。     

A feasible approach for direct his-bundle pacing using a new steerable catheter to facilitate precise lead placement

INTRODUCTION: Much clinical evidence has shown that right ventricular (RV) apical pacing is detrimental to left ventricular function. Preservation of the use of the His-Purkinje (H-P) system may be ideal in heart block that is restricted to the AV node, but may be of no benefit when H-P disease exists. AIM: To investigate the feasibility of direct His-bundle pacing (DHBP) using a new system consisting of a steerable catheter and a new 4.1 F screw-in lead. METHOD: Between May and December 2004, 26 patients (19 male, mean age: 77 +/- 5 years) with a standard pacemaker (PM) indication and preserved His-bundle conduction were enrolled and DHBP was attempted. RESULTS: DHBP was achieved in 24 patients (92%); two patients were paced in the His area, but the paced QRS morphology and duration were different from the native QRS. The mean time for lead positioning was 19 +/- 17 minutes, the mean fluoroscopy time was 11 +/- 8 minutes, and the total procedure time (skin-to-skin including positioning of a quadripolar diagnostic catheter for His recording) was 75 +/- 18 minutes. In DHBP pacing, the acute pacing threshold was 2.3 +/- 1.0 V at a pulse duration of 0.5 msec, and the sensed potentials were 2.9 +/- 2.0 mV. At a 3-month follow-up examination, the same QRS duration and morphology recorded on implantation were observed in all patients. The pacing threshold was 2.8 +/- 1.4 V, and sensed potentials were 2.5 +/- 1.8 mV; the sensing configuration was changed from bipolar to unipolar in 6 patients to resolve undersensing issues. No major complications were observed. CONCLUSIONS: This feasibility study shows that DHBP can be accomplished with a new system consisting of a steerable catheter and an active fixation lead in 92% of the patients in whom it was attempted.     

Mortality and Incidence of Atrial Fibrillation in Paced Patients

Mortality and AF Incidence in Paced Patients. This review presents and discusses available data from randomized controlled trials on the prognosis of pacemaker patients, especially the incidences of atrial fibrillation (AF) and death, the impact of pacing mode selection, and the impact of AF on prognosis. The incidence of AF is several times higher in paced patients than in the nonpaced population. The annual incidences of AF and chronic AF are at least 5% and 3%, respectively, after pacemaker implantation. Mean lifetime cumulative incidences of AF and chronic AF can be estimated at approximately 30% to 40% and 20%, respectively. The most important predictors of AF are brady‐tachy syndrome, sick sinus syndrome, and selection of VVI(R) pacing mode. The expected lifespan in paced patients is shorter than in the age‐matched nonpaced population. One of the factors decreasing lifespan in paced patients most likely is the high incidence and prevalence of AF. In patients with sick sinus syndrome, VVI pacing significantly increases AF and mortality compared with AAI pacing. In a mixed population of patients with bradycardia, DDD(R) pacing causes AF less often than does VVI(R) pacing. Survival does not differ between these pacing modes within the first 3.5 years after pacemaker implantation. At the present time, AAI(R) should be the preferred pacing mode in patients with sick sinus syndrome, and DDD(R) should be used for other patients without chronic AF for prevention of AF. It is not clear whether prevention of AF will improve survival of paced patients.     

The Atrial Pacing Peri-ablation for Paroxysmal Atrial Fibrillation (PA3) Study: rationale and study design.

The Canadian Atrial Pacing Peri-Ablation for Paroxysmal Atrial Fibrillation Study tested the hypotheses that atrial pacing prevents paroxysmal atrial fibrillation (PAF) in patients without symptomatic bradycardia and that DDDR pacing is more likely to prevent PAF following total atrioventricular (AV) node ablation compared to VDD pacing. Patients with PAF who were refractory to or intolerant of antiarrhythmic drug therapy received a Medtronic Thera DR pacemaker 3 months prior to a planned total AV node ablation. Patients were randomized to atrial pacing or no pacing therapy. The time to first recurrence of sustained PAF was the primary study outcome event. Following AV node ablation, patients were randomized to the DDDR or VDD mode in a crossover study design. Patients were followed in each mode for 6 months. The time course of PAF recurrence was compared for each pacing mode.     

希浦系统起搏操作和临床分析:单中心经验

目的总结北京大学第一医院前50例希浦系统起搏病例,为初期开展此项技术提供临床借鉴。方法回顾性分析2019年4-12月本中心同一术者团队行希浦系统起搏操作的前50例患者资料及手术和随访情况。按起搏部位分为希氏束起搏(HBP)组、左束支区域起搏(LBBP)组、室间隔内起搏(IVSP)组,比较各组间的手术操作、起搏结果和参数随访情况。结果按患者手术先后顺序每10例患者一组,共分为5组。随着手术例数的增加,希浦系统起搏的成功率从前10例的50%上升至最后10例的90%,而手术时间显著缩短[(152.7±55.1)min比(89.8±37.7)min,P=0.037],完成20例手术后,成功率稳定在80%以上较好的水平。按照最终起搏的结果,IVSP组15例、HBP组10例、LBBP组25例。左心室激动时间(LVAT),HBP组[(79.4±8.2)ms比(96.0±19.2)ms,P=0.012]和LBBP组[(81.5±13.5)ms比(96.0±19.2)ms,P=0.013]均显著短于IVSP组,差异均有统计学意义;而HBP组和LBBP组[(79.4±8.2)ms比(81.5±13.5)ms,P=0.928]比较,差异无统计学意义。起搏QRS波时限,HBP组[(106.4±19.9)ms比(138.8±18.9)ms,P<0.001]和LBBP组[(118.9±12.3)ms比(138.8±18.9)ms,P<0.001]均显著短于IVSP组,差异均有统计学意义;LBBP组较HBP组延长[(118.9±12.3)ms比(106.4±19.9)ms,P=0.030],差异有统计学意义。但HBP组的起搏阈值显著高于IVSP组[(1.4±0.5)V比(0.6±0.3)V,P<0.001]和LBBP组[(1.4±0.5)V比(0.7±0.2)V,P=0.019],差异均有统计学意义。感知R波则HBP组显著低于IVSP组[(5.7±2.1)mV比(10.2±5.3)mV,P=0.009]和LBBP组[(5.7±2.1)mV比(9.6±2.2)mV,P<0.001]。而LBBP组和IVSP组各项起搏参数均无差异。各组随访期间,起搏阈值和感知R波均无明显变化。手术操作中我们采用了影像法辅助希氏束及左束支区域的解剖定位。结论本中心回顾分析显示,第20~50例的手术操作,可以较熟练掌握希浦系统起搏技术。LBBP可作为初期开展希浦系统起搏的首选。影像解剖定位法可简化手术流程,避免对希氏束和传导束的损伤。     

心脏不同部位起搏的临床研究进展

永久性心脏起搏已成为症状性心动过缓、充血性心力衰竭等患者的有效治疗方法,基于最大程度恢复心脏正常激动和传导顺序的原则,生理性起搏成为近年来心脏起搏研究的热点。关于起搏部位的研究也有很多新的进展,现综合近年来心脏起搏部位临床研究的结果,对心脏不同部位起搏的临床进展作一综述。     

Atrial synchronous left ventricular only pacing with VDD pacemaker system – A cost effective alternative to conventional cardiac resynchronization therapy

Introduction

Atrial synchronous left ventricular (LV) only pacing using two leads and VDD pacemaker could be a cost effective alternative to conventional cardiac resynchronization therapy (CRT).

Methods

We implanted right atrial (RA) and LV leads with VDD pulse generator (LV only pacing) in five carefully screened heart failure patients who could not afford conventional CRT. All had NYHA class III/IV symptoms despite maximal guideline directed medical therapy. The sensed atrioventricular delay was programmed to pre-excite the LV and achieve fusion beat. Response to treatment was assessed at 6 months.

Results

Four patients were males. The mean age was 58 ± 12 years. At follow up, there was improvement in electrocardiographic, and echocardiographic parameters: Mean QRS duration decreased from 174 ± 17 msec to 128 ± 10.9 msec (p = 0.009), LV end-diastolic diameter decreased from 73.2 ± 12 mm to 65.8 ± 9.6 mm (p = 0.026), LV end-systolic diameter decreased from 65 ± 12 mm to 54 ± 10 mm (p = 0.020). There was a trend towards reduction of LV end-systolic and end-diastolic volumes. LV ejection fraction improved from 25 ± 6% to 34 ± 6% (p = 0.013) and left atrial dimension reduced from 44 ± 4 mm to 39 ± 5 mm (p = 0.045). All patients improved clinically.

Conclusion

RA-LV pacing using VDD pacemaker is a safe and effective technique of CRT. This may be a cost effective alternative to conventional CRT for patients in developing countries.     

Electrophysiological characteristics and possible mechanism of bipolar pacing in left bundle branch pacing

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Pacing for sinus node disease: A therapeutic rationale

Symptomatic sinus node disease is a common indication for permanent pacemaker implantation. Single-chamber ventricular (VVI) pacing, single-chamber atrial (AAI) stimulation, and dual-chamber (DDD or DDI) systems are used to a varying extent at different implanting centers. Hemodynamic and clinical studies relevant to the choice of pacing mode in these patients are reviewed. The data currently available strongly support the use of pacing systems providing atrial stimulation. The choice between single-chamber atrial or dual-chamber pacing can be based on the relative importance assigned to a number of factors: Hemodynamic aspects, the risk of ventricular lead problems, cost, and complexity aspects favor AAI pacing, whereas patients with a substantial risk of developing atrioventricular block should receive a DDD or DDI unit.     

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.     

Sustained improvement in exercise tolerance following physiological cardiac pacing

Fifty-three patients have received ‘physiological’pacemakers,37 with atrioventricular (AV) block having atrial synchronousunits (VAT or VDD) implanted and the remaining 16 patients withboth AV block and sick sinus syndrome having ‘universal’(DDD) pacemakers. Effort tolerance was assessed by serial bicycleergometry and in 16 patients direct comparisons between ventricularpacing and atrial synchronous pacing could be made acutely.Physiological pacemakers were found to increase maximum efforttolerance by 43% compared to pre-pacing values (P<0.01).The increase was sustained over a mean of 33 months post pacing.The atrial synchronous mode increased maximum effort toleranceby 34% acutely compared to ventricular inhibited pacing. Dualchambered ‘physiological’ pacemakers represent asignificant therapeutic advance over standard ventricular inhibitedpacemakers.     

Atrial fibrillation: profit from cardiac pacing?

Summary The impact of cardiac pacing on the prevention of atrial fibrillation is under scientific investigation. Several prospective randomised clinical trials have reported that atrial-based physiologic AAI(R)- or DDD(R)-pacing is associated with a lower incidence of paroxysmal and permanent atrial fibrillation than single-chamber ventricular pacing in patients with a conventional pacemaker indication. However, it is still uncertain whether atrial pacing itself has independent antiarrhythmic properties. In contrast, right ventricular pacing is considered to promote atrial fibrillation, even in preserved AV synchrony during dual-chamber pacing. The electrical secondary prevention of atrial fibrillation is mainly based on variations of the atrial pacing site and sophisticated preventive pacing algorithms incorporated in the pacemaker software. Dual-site right atrial and biatrial pacing were reported to exhibit modest to no benefit for the prevention of atrial fibrillation, whereas septal pacing and specific preventive pacing algorithms have been demonstrated to reduce the incidence of atrial fibrillation in a number of clinical trials. However, the role of septal pacing and preventive pacing algorithms still has to be clarified since, overall, study results have been inconsistent so far. One of the main goals of future investigations should be the identification of responder groups of preventive pacing concepts. In clinical practice, the efficacy of pacing algorithms and septal pacing has to be determined in the individual case. These options should be taken into account in patients with symptomatic bradycardia as the indication for cardiac pacing and, in addition, symptomatic atrial fibrillation.

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