Permanent parahisian pacing

Right Ventricular Apical permanent pacing could have negative hemodynamic effects. A physiologic pacing modality should preserve a correct atrio-ventricular and interventricular synchronization. This can be obtained through biventricular pacing, left ventricular pacing, or from alternative right ventricular pacing sites. Direct His Bundle Pacing (DHBP) was documented as reliable and effective for preventing the desynchronization and negative effects of right ventricular apical pacing. It is, however, a complex method that requires longer average implant times, cannot be carried out on all patients and presents high pacing thresholds. On the contrary, the parahisian pacing, with simpler feasibility and reliability criteria, seems to guarantee an early invasion of the His-Purkinje conduction system, with a physiological ventricular activation, very similar to the one that can be obtained with direct His bundle pacing. We present our experience on 68 patients who underwent a permanent right ventricular pacing in hisian/parahisian region, for advanced AV block and narrow QRS. In the first 17 patients we performed a double-blind randomized controlled study, with two 6-months cross-over periods in parahisian and apical pacing, documenting a significant improvement of NYHA class, exercise tolerance, quality of life score, mitral and tricuspidal regurgitation degree, and interventricular mechanical delay. In the subsequent 51 patients, in a mean follow of 21 months/patient, the pacing threshold remained stable (0.7+/-0.5 V implant; 0.9+/-0.7 V follow-up; p=0.08). The ejection fraction maintained medium-long term stable values, confirming the fact that the parahisian pacing can prevent deterioration of the left ventricular function. Parahisian pacing, therefore, has proven to be a reliable method, easy to apply and effective in preventing the negative effects induced by non-physiological right ventricular apical pacing.     

Normalisation of the ECG in a patient with right bundle branch block by cardiac pacing

Right ventricular apical pacing (RVA) appears to have potential deleterious effects on myocardial systolic and diastolic left ventricular function, especially in patients with intact AV conduction. Therefore, new pacing sites in the right ventricle are being explored to overcome these detrimental effects. Alternative pacing sites in the right ventricle are the right ventricular outflow tract (RVOT) and the right ventricular septum (RVS). In this case report, we demonstrate an exceptional form of ventricular fusion, namely normalisation of the QRS complex in a patient with pre-existing right bundle branch block by RVS pacing. To our knowledge, this is the first report in the literature where right ventricular pacing could restore a complete RBBB to a normal QRS complex by stimulating distally from the anatomical position of the RBBB, due to fusion between artificial right ventricular stimulation and intrinsic conduction over the left bundle of the specific His-Purkinje system.     

Left ventricle pacing challenges in cardiac resynchronization therapy systems

Left ventricle (LV) pacing can be considered peculiar due to its different lead/tissue interface (epicardial pacing) and the small vein wedging lead locations with less reliable lead stability. The current technologies available for LV capture automatic confirmation adopt the evoked response (ER), as well as “LV pace to right ventricular (RV) sense” algorithms. The occurrence of anodal RV capture is today completely solved by the use of bipolar LV leads, while intriguing data are recently published regarding the unintentional LV anodal capture beside the cathodal one, which may enlarge the front wave of cardiac resynchronization therapy (CRT) delivery. The LV threshold behavior over time leading to ineffective CRT issues (subthreshold stimulation or concealed loss of capture), the extracardiac capture with phrenic nerve stimulation (PNS), the flexible electronic cathode reprogramming and the inadequate CRT delivery related to inadequate AV and VV pace timing (and its management by LV “dromotropic pace-conditioning”) are discussed.Moreover, recently, His bundle pacing (HBP) and left bundle branch pacing (LBBP) have shown growing interest to prevent pacing-induced cardiomyopathy as well as for direct intentional CRT.The purpose of the present review is to explore these new challenges regarding LV pacing starting from old concepts.     

QRS alternans during right ventricular pacing while ablating a concealed left sided accessory pathway

A 16-year-old boy was referred for an electrophysiological study for documented regular narrow complex tachycardia. A diagnosis of a concealed left lateral accessory pathway was made with an eccentric atrial activation sequence both during tachycardia and right ventricular (RV) pacing. The pathway was mapped at the left posterior mitral vestibule during RV pacing, performed through the distal tip of the His bundle catheter pushed into right ventricular outflow tract. An unusual response to ventricular stimulation with alternation of QRS complex width and morphology was noted. The possible mechanisms are hereby discussed.     

Selective left bundle branch pacing for pediatric complete heart block

Traditionally Right Ventricle has been the preferred site of pacing for the management of symptomatic brady-arrhythmias. The deleterious effect of chronic RV pacing has been shown by several studies. This has generated interest into a novel pacing strategy called physiological pacing wherein the His bundle or the left bundle is paced directly with 4.1 F pacing lead. Herewith we are reporting a case of congenital complete heart block in a 13-year-old child for whom selective left bundle branch pacing was done. This physiological pacing will ensure a synchronized contraction of the ventricles thereby avoiding the deleterious effect of RV pacing.     

Selective His-bundle pacing in an adult with atrioventricular canal defect via retrograde His localization

Adult congenital heart disease patients may undergo numerous fluoroscopically guided procedures including pacemaker implantation during their lifetime. One alternative to traditional pacemaker setup which may improve long-term pacing outcomes is His bundle pacing. Given the altered His-bundle location, and given increased radiation exposure over a lifetime, we used 3-dimensional mapping to locate the His and to minimize fluoroscopy for placement of a His-bundle pacemaker system in a 31-year old patient with atrioventricular canal defect and complete heart block with 100% RV pacing and epicardial lead fracture.MethodsAn Octapolar Livewire catheter (Abbott, Minneapolis, USA) was used for mapping and location of the His bundle from a right femoral venous access on the EnSite Precision system 3-dimensional mapping system (Abbott Medical, Abbott Park, IL). The same map was used to guide 3830 lead placement into the posterior-inferior His-bundle position.ResultsSuccessful placement of a His-bundle pacing system with thresholds of 1Volt@0.4ms for both the atrial and ventricular leads with selective His-bundle pacing noted. Ten-month follow-up demonstrated His-bundle capture at 0.75V@0.4ms with stable impedance, sensing and with 100% right ventricular pacing a projected longevity of 12 years total.ConclusionsSuccessful placement of selective His-bundle pacing can be achieved in an adult patient with atrioventricular canal defect using 3-dimensional mapping.     

Atrial pacing, the forgotten pacing mode

In patients with sick sinus syndrome and normal atrioventricular conduction, physiological pacing can be accomplished with either a single chamber atrial pacemaker AAI/R or a dual chamber pacemaker DDD/R. The single chamber device has the advantages of simpler implantation and lower initial costs, while the dual chamber device offers protection in case atrioventricular conduction disturbances develop in the future. When rigorous attention is paid to the pre-implantation selection criteria, the incidence of reported second- or third-degree atrioventricular block varied between 0.4 and 1.8% per annum. Medical practice, however, has shifted to predominant implantation of DDD/R pacemakers in more than 95% of patients with sick sinus syndrome. Recent publications have reported an increase in left atrial diameter, decrease in left ventricular fractional shortening and increased incidence of atrial fibrillation in patients with DDD/R pacing as compared with patients with single chamber atrial devices. These changes were proportional to the percentage of ventricular paced beats. New algorithms in dual chamber devices have been developed in order to minimise ventricular stimulation. These are being evaluated at present. In my opinion there is still a place for atrial pacing in selected patients with sick sinus syndrome with a minimum risk of developing complete atrioventricular block. (Neth Heart J 2008;16(suppl 1): S25-S27.)     

Effects of ectopic pacing on repolarization of the chicken left ventricle

Effects of ectopic pacing on left ventricular repolarization were studied in six anesthetized open-chest chickens. In each animal, unipolar electrograms were acquired from as many as 98 sites with 14 plunge needles (seven transmural locations between epicardium and endocardium in each needle). Activation-recovery intervals (ARIs), corrected to the cycle length, were used for estimating repolarization. At baseline, the nonuniform ARI distribution in the left ventricle resulted in the apicobasal differences being greater than the transmural gradient. Nonuniform ARI prolongation caused by ectopic pacing resulted in decreasing the transmural repolarization gradient and increasing the differences in the apex-to-base direction. The basal, but not apical transmural differences contributed to the total left ventricular transmural gradient. The total left ventricular apicobasal gradient was contributed by the apicobasal differences in mid-myocardial and subendocardial layers more than in subepicardial ones. Thus, in in situ chicken hearts, the transmural and apicobasal ARI gradients exist within the left ventricle with the shortest ARIs in the basal subepicardium and the longest ARIs in the subendocardium of the apical and middle parts of the left ventricle. Apicobasal compared to transmural heterogeneity of local repolarization properties contributes more to the total left ventricular repolarization gradient.     

The downside of right ventricular apical pacing

The right ventricular (RV) apex has been the standard pacing site since the development of implantable pacemaker technology. Although RV pacing was initially only utilized for the treatment of severe bradyarrhythmias usually due to complete heart block, today the indications for and implantation of RV pacing devices is dramatically larger. Recently, the adverse effects of chronic RV apical pacing have been described including an increased risk of heart failure and death. This review details the detrimental effects of RV apical pacing and their shared hemodynamic pathophysiology. In particular, the role of RV apical pacing induced ventricular dyssynchrony is highlighted with a specific focus on differential outcome based upon QRS morphology at implant.     

Transvenous implantation of a ventricular pacing lead in a patient with an artificial tricuspid valve prosthesis

The preference for treatment of symptomatic bradycardia is transvenous right ventricular pacing combined with atrial synchronisation if applicable. In the case of congenital anomalies where no conduit is present between the peripheral veins and the right ventricle, it is not possible to place the ventricular pacing lead in the right ventricle. Also the presence of an artificial valve in the tricuspid position excludes placement of an endocardial right ventricular pacing lead. Since the introduction of biventricular pacing, new guiding catheters and leads used as a transvenous route for left ventricular pacing are available. We report implantation of a ventricular pacing lead in the great cardiac vein for permanent ventricular pacing in a patient with a tricuspid valve prosthesis.     

Biventricular mechanical asynchrony predicts hemodynamic effect of uni- and biventricular pacing

We tested whether biventricular resynchronization explains contractile function changes with univentricular and biventricular pacing in heart failure patients with varying magnitudes of baseline biventricular asynchrony. Thirty patients (New York Hospital Association class > or = III, QRS duration > or =120 ms) were tested. Contractile function was measured by left ventricular maximum first derivative of pressure over time (dP/dtmax). Biventricular mechanical asynchrony was quantified by the normalized pressure-pressure (NPP) loop area formed by the cross-plot of right and left intraventricular pressure curves from each cardiac cycle. Any ventricular pacing increased dP/dtmax if it decreased baseline NPP loop area and almost always worsened dP/dtmax and asynchrony when baseline NPP loop area <0.3. The quantitative relationship between dP/dtmax and NPP loop area change depended on ventricular pacing site and timing relative to intrinsic activation. For similar NPP loop decreases, dP/dtmax increased 16% more with left and biventricular pacing compared with right ventricular pacing. In conclusion, right, left, or biventricular pacing can improve contractile function only in patients having sufficient baseline biventricular asynchrony. However, biventricular resynchronization is only one of the improvement mechanisms.     

Transesophageal left ventricular posterior wall potential in heart failure patients with biventricular pacing.

INTRODUCTION: Biventricular (BV) pacing is an established therapy for heart failure (HF) patients with intraventricular conduction delay, but not all patients improved clinically. We investigated the interventricular delay (IVD) by means of the transesophageal left ventricular posterior wall potential (LVPWP). MATERIALS AND METHODS, AND RESULTS: A total of 18 HF patients (age 62+/-9 years; 15 males) with NYHA class 3.1+/-0.3, LV ejection fraction 22+/-7%, left bundle branch block and a QRS duration (QRSD) of 171+/-27 ms were analyzed using transesophageal LVPWP before implantation of a BV pacing device. The median follow up was 14+/-14 months. In 14 responders, IVD was 81+/-25 ms with a QRSD/IVD ratio of 2.2+/-0.3 with reclassification of NYHA class 3.1+/-0.3 to 2.0+/-0.5 (p<0.001) and an increase in LV ejection fraction from 22+/-7% to 36+/-11% (p=0.001) during long-term BV pacing. In four non-responders, transesophageal IVD was significantly smaller at 30+/-11 ms (p=0.001). CONCLUSION: Transesophageal IVD may be a useful method to detect responders to BV pacing. Transesophageal LVPWP may be a simple and useful technique to detect clinical responders to BV pacing in HF patients.     

起搏器术后新发房性心律失常的影响因素分析

目的:探讨起搏器术后新发房性心律失常的发生情况及其相关影响因素。方法:选择2006年1月至2007年12月于沈阳军区总医院首次植入永久起搏器的107例患者,男性50例,平均年龄65.0±11.9岁,术前通过追问病史及相关检查均排除房性心律失常(房颤、房扑、房速),术后平均随访3.9年,观察新发房性心律失常情况。按术后是否出现房性心律失常,将患者分为新发房性心律失常组和无房性心律失常组,比较两组患者术前和术后心脏超声结果的变化、心室起搏比例、起搏部位及起搏模式,并通过logistic回归分析起搏器术后发生房性心律失常的影响因素。结果:新发房性心律失常组26例(24.3%),其中房颤17例(15.9%),房扑2例(1.9%),房速7例(6.5%);无房性心律失常组81例。与无房性心律失常组比较,新发房性心律失常组左房内径明显增加(P=0.040)、二尖瓣返流程度较重(P=0.032)及左室射血分数明显下降(P=0.001),心室起搏百分比(VP%)显著升高(P=0.017)。心尖部起搏患者房性心律失常的发生率明显高于间隔部起搏(33.3%vs 16.9%,P<0.05),双腔起搏组患者房性心律失常发生率明显低于单腔起搏器组(18.7%vs 37.5%,P<0.05)。Logistic回归分析显示术后新发房性心律失常的发生与高比例的心室起搏(P=0.006)、VVI(R)起搏模式(P=0.014)及右心室起搏电极导线植于心尖部(P=0.024)显著相关。结论:起搏模式、心室起搏百分比、起搏部位是起搏器术后发生房性心律失常的影响因素。     

心室不同部位起搏对正常犬和扩张型心肌病心力衰竭犬模型在体心肌跨室壁复极离散的影响

实验以正常犬和扩张型心肌病心力衰竭犬(dilated cardiomyopathy congestive heart failure,DCM-CHF)模型为对象、以心肌跨室壁复极离散的相关参数为指标,研究左心室心外膜起搏、双心室起搏(模拟临床上心室再同步治疗的方法)后的心肌电生理特性变化。实验以快速右心室起搏的方法制备DCM-CHF犬模型;正常犬和DCM-CHF犬均经射频消融希氏束制备三度房室传导阻滞模型;采用同步记录犬体表心电图和内膜下、中层、外膜下三层心肌单相动作电位(monophasic action potentials,MAP)的方法,测定不同部位起搏时的QT间期、Tpeak-Tend(Tp-Te)间期和三层心肌的单相动作电位时程(MAP duration,MAPD)、跨室壁复极离散度(transmural dispersion of repolaization,TDR)。结果显示:在正常犬,左室心外膜与双心室起搏后三层心肌的MAPD均延长,同时TDR增大(左室心外膜起搏47.16 ms、双心室起搏37.54 ms、右室心内膜起搏26.75 ms,P<0.001),体表心电图Tp-Te间期的变化与之平行;在DCM-CHF犬较正常犬已表现出中层心肌MAPD延长(276.30 ms vs 257.35 ms,P<0.0001)和TDR(33.8 ms vs 27.58 ms,P=0.002)增大的基础上,左室心外膜参与起搏后仍进一步使三层心肌的MAPD延长和TDR增大。研究结果提示,左室心外膜起搏和双心室起搏后使内膜下、中层     

Electrocardiographic patterns in biventricular pacing delivered by second-generation cardiac resynchronization devices

Background

With increasing use of cardiac resynchronization therapy (CRT), treating physicians should be familiar with different electrocardiographic (ECG) patterns of left ventricular (LV) lead and biventricular (BiV) pacing. However, there are a few publications on ECG patterns during BiV pacing.

Acute Impact of Pacing at Different Cardiac Sites on Left Ventricular Rotation and Twist in Dogs

Objectives

We evaluated the acute impact of different cardiac pacing sites on two-dimensional speckle-tracking echocardiography (STE) derived left ventricular (LV) rotation and twist in healthy dogs.

Methods

Twelve dogs were used in this study. The steerable pacing electrodes were positioned into right heart through the superior or inferior vena cava, into LV through aorta across the aortic valve. The steerable pacing electrodes were positioned individually in the right atrium (RA), right ventricular apex (RVA), RV outflow tract (RVOT), His bundle (HB), LV apex (LVA) and LV high septum (LVS), individual pacing mode was applied at 10 minutes interval for at least 5 minutes from each position under fluoroscopy and ultrasound guidance and at stabilized hemodynamic conditions. LV short-axis images at the apical and basal levels were obtained during sinus rhythm and pacing. Offline STE analysis was performed. Rotation, twist, time to peak rotation (TPR), time to peak twist (TPT), and apical-basal rotation delay (rotational synchronization index, RSI) values were compared at various conditions. LV pressure was monitored simultaneously.

Results

Anesthetic death occurred in 1 dog, and another dog was excluded because of bad imaging quality. Data from 10 dogs were analyzed. RVA, RVOT, HB, LVA, LVS, RARV (RA+RVA) pacing resulted in significantly reduced apical and basal rotation and twist, significantly prolonged apical TPR, TPT and RSI compared to pre-pacing and RA pacing (all P<0.05). The apical and basal rotation and twist values were significantly higher during HB pacing than during pacing at ventricular sites (all P<0.05, except basal rotation at RVA pacing). The apical TPR during HB pacing was significantly shorter than during RVOT and RVA pacing (both P<0.05). The LV end systolic pressure (LVESP) was significantly lower during ventricular pacing than during pre-pacing and RA pacing.

Conclusions

Our results show that RA and HB pacing results in less acute reduction on LV twist, rotation and LVESP compared to ventricular pacing.     

Right bundle branch block pattern during right ventricular permanent pacing: Is it safe or not?

The present case report describes a patient with dual chamber pacemaker whose surface ECG demonstrated paced right bundle branch block pattern suggesting a malpositioned ventricular lead in the left ventricle. However, diagnostic work-up revealed that the lead was appropriately located in the right ventricular apex. Diagnostic maneuvers and clues for differentiating safe right bundle branch block pattern during permanent pacing are thoroughly revisited and discussed within the article.     

Left ventricular pacing in patients with congestive heart failure

Cardiac resynchronisation therapy (CRT) using biventricular (BIV) pacing has proved its effectiveness to correct myocardial asynchrony and improve clinical status of patients with severe congestive heart failure (CHF) and widened QRS. Despite a different effect on left ventricular electrical dispersion, left univentricular (LV) pacing is able to achieve the same mechanical synchronisation as BIV pacing in experimental studies and in humans. This results in clinical benefits of LV pacing at mid-term follow-up, with significant improvement in functional class, quality of life and exercise tolerance at the same extent as those observed with BIV stimulation in non randomised studies. Furthermore these benefits are obtained at lesser costs and with conventional dual-chamber devices. However, LV pacing has to be compared to BIV pacing in randomised trials before being definitely considered as a cost-effective alternative to BIV pacing.     

Pitfalls and Nuances of Parahisian pacing: A revisit through an interesting case

Parahisian pacing (PHP) is a useful maneuver during electrophysiology study of supraventricular tachycardia (SVT) especially when the tachycardia is non-sustained. Various responses during PHP can differentiate between the routes of VA conduction (VAC). In a case of WPW syndrome with orthodromic re-entrant tachycardia, we encountered various responses which one must be cognizant about to avoid erroneous conclusions. Along with para-hisian capture and only ventricular capture, simultaneous atrial capture (SAC) and pure His capture were also noted. Moreover, during pure-His capture underlying distal antegrade right bundle branch block (RBBB) was encountered making it an intriguing case.     

Right bundle branch block pattern after uncomplicated right ventricular outflow tract pacing in a patient with a left sided superior vena cava and corrected tetralogy of Fallot

Usually an electrocardiogram after right ventricular (RV) pacing should yield left bundle branch block (LBBB) pattern. However, the presence of right bundle branch block (RBBB) pattern after pacemaker implantation should alert the physician to a malposition of lead. We report a case of 18-year-old female who underwent dual chamber pacemaker implantation and had RBBB pattern post implantation. Detailed evaluation revealed an uncomplicated right ventricular outflow tract pacing. The possible causes of this abnormal pattern after an uncomplicated RV pacing are also reviewed.