Right Ventricular Pacing Sites Research Articles

Zero or near-zero x-ray pacemaker implantation in paediatric patients. dream or reality?

Abstract Funding Acknowledgements Type of funding sources: None. Background/Introduction Transvenous implantation of pacemaker is performed with fluoroscopy for leads’ insertion and implantation in the heart. This implies radiation exposure for patients and operators. Fluoroscopy allows a two-dimensional view of lead movements, and sometimes it is difficult to implant lead in the complex heart anatomy, or in alternative right ventricular (RV) pacing sites, that often requires higher radiation doses. These alternative pacing sites may prevent pacing-induced ventricular dysfunction. They are his bundle pacing area (HBP), ventricular septum close to the conduction system area (VS), RV outflow tract (RVOT). The use of three-dimensional-electroanatomic mapping system (3D-EAM) may reduce fluoroscopy and guide lead implantation. Published median fluoroscopy data for similar procedure are: 6 mGy (1), 13 mGy and 231 microGy/m2 (2). Purpose of this study is to seek out if a 3D-EAM-guided transvenous implantation into RV alternative sites pacing in paediatric patients can be accomplished with zero or near-zero X-rays. Methods Retrospective analysis of children and adolescents with congenital or acquired (idiopathic) complete atrioventricular block (CAVB) without other congenital heart defects who underwent 3D-EAM-guided pacing in alternative RV sites. The implant procedure was divided in 4 steps: 1-contrast venography; 2- 3D mapping: with a steerable catheter (femoral vein), the 3D-EAM acquired geometric reconstruction of the right heart and a pacing map identified RV sites with narrower paced QRS; 3-axillary vein puncture; 4-lead and pacemaker implantation: 3D-EAM guided stylet-directed screw-in lead implantation toward desired RV sites. Data are reported as median (25th-75th centiles). Results 54 CAVB patients (42 females), underwent 3D EAM-guided pacing (27 VVIR, 27 DDD) at age 11.5 (7.7-14) years, weight 42 (26-54) kg. Pacing sites were: 10 HBP, 4 RVOT, 40 VS (Figure 1). Procedure time was 170 (143-193) min, total fluoroscopy exposure and that of the 4 steps are reported in Table 1. The lowest exposures were: 0.2 mGy, 8 microGy/m2 (VVIR) and 0.6 mGy, 15 microGy/m2 (DDD). Paced QRS was 115 (100-120) ms. Conclusions 3D-EAM-guided alternative RV pacing sites was accomplished with very low fluoroscopic exposure, close to zero in some cases. Therefore, with 3D-EAM we can significantly reduce radiological doses also in difficult pacing procedures in paediatric patients, thus reducing radiological risks and preserving ventricular function. The dream is becoming reality.

PO-05-082 ANTITACHYCARDIA PACING IS MORE EFFECTIVE WHEN DELIVERED TO THE LEFT BUNDLE BRANCH COMPARED TO THE RIGHT VENTRICLE IN A CANINE ISCHEMIC VENTRICULAR TACHYCARDIA MODEL

Implantable cardioverter-defibrillators (ICDs) can terminate ventricular tachycardia (VT) with Antitachycardia pacing (ATP) delivered to a right ventricular (RV) pacing lead, thereby avoiding painful and damaging high-energy shocks. However, ATP efficacy is limited for fast VT, and ATP can accelerate VT or convert VT to ventricular fibrillation (VF). Physiological pacing delivered to the left bundle branch (LBB) has emerged as a clinically relevant target to minimize ventricular dyssynchrony and pacing-induced heart failure. ATP efficacy and safety delivered to the LBB are yet to be investigated. Evaluate the therapeutic efficacy and safety of ATP delivered to an LBB lead compared to ATP delivered to a conventional RV lead. In 6 anesthetized dogs, pacing leads from two ICDs (CobaltTM XT DR, Medtronic, Inc) were implanted at the RV apex (6947 Sprint Quattro SecureTM, Medtronic, Inc) and the LBB (3830 SelectSecureTM, Medtronic, Inc). A lateral thoracotomy procedure was performed, and a two-hour lateral anterior descending artery ischemia-reperfusion injury was caused. The thoracotomy was closed and on post-infarct day 4, dogs were anesthetized, and sustained VT episodes were induced by programmed electrical stimulation. ATP (up to 5 trains of 8 pulses at approximately 88% of the VT cycle length) was delivered to either the LBB or RV pacing site in a randomized fashion. The success rate of ATP in terminating the VT episodes and the rate of VT acceleration and degeneration into VF from both pacing locations were evaluated. In our canine ischemic VT model, VT was induced 80 times, with a mean VT cycle length of 178±35 ms. ATP was delivered and tested for each episode. For ATP delivered to the RV, the success rate for terminating VT was 54%. The success rate for terminating VT for ATP delivered to the LBB was 73% (Fig. A, p < 0.05). ATP resulted in VT acceleration for 10% and 5% of ATP attempts delivered to the RV and LV, respectively (Fig. B, p = Not Significant, NS). Degeneration to VF occurred for 5% of all ATP attempts delivered to the RV, and there was no such incident for ATP delivered to the LBB (Fig. B). Higher efficacy and lower incidence of VT acceleration were observed with ATP delivered to LBB compared to ATP delivered to the RV in this canine ischemic VT model. Improved performance of ATP delivered to LBB compared to RV provides additional incentive for expanded use of LBB leads for pacing and therapy delivery.

Novel non-invasive ECG imaging method based on the 12-lead ECG for reconstruction of ventricular activation: A proof-of-concept study.

Current non-invasive electrocardiographic imaging (ECGi) methods are often based on complex body surface potential mapping, limiting the clinical applicability. The aim of this pilot study was to evaluate the ability of a novel non-invasive ECGi method, based on the standard 12-lead ECG, to localize initial site of ventricular activation in right ventricular (RV) paced patients. Validation of the method was performed by comparing the ECGi reconstructed earliest site of activation against the true RV pacing site determined from cardiac computed tomography (CT). This was a retrospective study using data from 34 patients, previously implanted with a dual chamber pacemaker due to advanced atrioventricular block. True RV lead position was determined from analysis of a post-implant cardiac CT scan. The ECGi method was based on an inverse-ECG algorithm applying electrophysiological rules. The algorithm integrated information from an RV paced 12-lead ECG together with a CT-derived patient-specific heart-thorax geometric model to reconstruct a 3D electrical ventricular activation map. The mean geodesic localization error (LE) between the ECGi reconstructed initial site of activation and the RV lead insertion site determined from CT was 13.9 ± 5.6 mm. The mean RV endocardial surface area was 146.0 ± 30.0 cm2 and the mean circular LE area was 7.0 ± 5.2 cm2 resulting in a relative LE of 5.0 ± 4.0%. We demonstrated a novel non-invasive ECGi method, based on the 12-lead ECG, that accurately localized the RV pacing site in relation to the ventricular anatomy.

Influence of the right ventricular septum/free-wall boundary (hinge) on differentiation of the ventricular lead implantation site

BackgroundThe prognosis associated with right ventricular (RV) free-wall pacing is worse than that of septal pacing. Identification of the pacing site using a 12‑lead electrocardiogram (ECG) is controversial and may be influenced by ECG changes within the same septal or free-wall area. The relationship between the diagnostic capabilities of ECG and pacing sites has previously been qualitatively evaluated. However, in this study, this relationship was analyzed quantitatively, and accurate evaluation of the pacing site was determined using computed tomography (CT). MethodsOf 779 consecutive outpatients, 65 who underwent pacemaker implantation and thoracic CT were prospectively included and classified into the following groups according to the lead tip position: free-wall, septal, or septum/free-wall boundary (hinge) group. The hinge was used as an anatomical marker, and the distance from the hinge to the lead tip was measured. Under RV pacing, a 12‑lead ECG was obtained. ECG findings were evaluated using three criteria (including lead I, II, and aVL and precordial leads V5 and V6) previously reported to be useful in differentiating pacing sites. ResultsThe lead tips were anchored at the free-wall in 10 patients, the septal wall in 19 patients, and the hinge in 32 patients. Paced QRS duration correlated with the distance from the hinge to the lead tip for the free-wall and septum (r = 0.47 and − 0.68, respectively). Estimation of the lead tip implantation site using the ECG algorithm was useful; however, the algorithm's accuracy decreased around the hinge. ConclusionsECG is useful in differentiating pacing sites but is less accurate around the hinge, which may be the reason that the identification of the RV pacing site using ECG remains controversial.

Retrograde penetration pacing into the conduction system as an alternative approach of his-bundle pacing

BackgroundThe optimal right ventricular (RV) pacing site during pacemaker implantation is still unclear due to left ventricular (LV) dyssynchrony by traditional RV pacing. His-bundle (HIS) pacing has achieved narrow QRS and maintained LV synchrony but high failure rate. RV septal pacing occasionally has QRS waveform with wide and narrow component in the early and late phase, respectively, and maintains LV synchrony, reflecting the normal conduction system. We aimed to define this QRS waveform as retrograde penetration pacing into the conduction system (RPP-CS) and compared its effect on LV synchrony as an alternative approach of HIS pacing. Methods and ResultsWe enrolled 42 patients with atrio ventricular block (AVB) or bradycardia atrial fibrillation (AF) requiring pacemaker implantation (RPP-CS, n = 27; no RPP-CS, n = 15). Baseline characteristics were similar between the groups. RPP-CS was observed in 96% and 26% of the RV septum and apex area, respectively. RPP-CS had a significantly shorter QRS width (p < 0.001). The frequency of maintaining LV synchrony was significantly higher in RPP-CS (67% vs. 20%, p = 0.003). The QRS interval's optimal cut-off value during RPP-CS was 132 ms for prediction of LV synchrony (sensitivity 83%, specificity 89%, positive predictive value 94%, and negative predictive value 73%). During RPP-CS, shorter QRS intervals (QRS ≤ 132 ms) had better postoperative LV ejection fraction than longer intervals (p < 0.001). ConclusionsRPP-CS, especially with short QRS intervals (≤132 ms), had a high frequency of LV synchrony, maintained postoperative cardiac function, and may be an adequate first-line RV pacing site strategy for AVB or bradycardia AF as an alternative approach of HIS pacing.

Ventricular activation pattern assessment during right ventricular pacing: Ultra‐high‐frequency ECG study

Right ventricular (RV) pacing causes delayed activation of remote ventricular segments. We used the ultra-high-frequency ECG (UHF-ECG) to describe ventricular depolarization when pacing different RV locations. In 51 patients, temporary pacing was performed at the RV septum (mSp); further subclassified as right ventricular inflow tract (RVIT) and right ventricular outflow tract (RVOT) for septal inflow and outflow positions (below or above the plane of His bundle in right anterior oblique), apex, anterior lateral wall, and at the basal RV septum with nonselective His bundle or RBB capture (nsHBorRBBp). The timings of UHF-ECG electrical activations were quantified as left ventricular lateral wall delay (LVLWd; V8 activation delay)and RV lateral wall delay (RVLWd; V1 activation delay). The LVLWd was shortest for nsHBorRBBp (11 ms [95% confidence interval = 5-17]), followed by the RVIT (19 ms [11-26]) and the RVOT (33 ms [27-40]; p < .01 between all of them), although the QRSd for the latter two were the same (153 ms (148-158) vs. 153 ms (148-158); p = .99). RV apical capture not only had a longer LVLWd (34 ms (26-43) compared to mSp (27 ms (20-34), p < .05), but its RVLWd (17 ms (9-25) was also the longest compared to other RV pacing sites (mean values for nsHBorRBBp, mSp, anteriorand lateral wall captures being below 6 ms), p < .001 compared to each of them. RVIT pacing produces better ventricular synchrony compared to other RV pacing locations with myocardial capture. However, UHF-ECG ventricular dysynchrony seen during RVIT pacing is increased compared to concomitant capture of basal septal myocytes and His bundle or proximal right bundle branch.

Ventricular Dyssynchrony based on echocardiographic variables and exercise tolerance After right ventricular pacing: Impact of alternative septal lead locations.

We investigated the impact of alternative locations of right ventricular (RV) pacing on left ventricular function and its relation to exercise capacity. Fifty patients who received a single lead pacemaker were divided according to RV pacing site into group 1 "high septum" (n=15), group 2 "mid-septum" (n=25), and group 3 "low septum" (n=10) using a documented fluoroscopic method. Dyssynchrony parameters were obtained using different echocardiographic parameters. Their exercise tolerance was evaluated after 6months of pacemaker implantation using 6minutes walk test (6 MWT). We found a lesser degree of dyssynchrony in mid-location and high location compared with low location pacing (radial dyssynchrony: P<.001; maximum temporal difference: P<.01; inter-ventricular mechanical delay: P<.05, standard deviation of time-to-peak strain by tissue Doppler: P<.05). Sm was significantly increased 6months following pacemaker implantation in group 1 and group 2 in contrast to group 3 patients (P<.05). Importantly, E/e' increased significantly (P<.001) in patients with low septal location pacing. Furthermore, 6 MWT distance was significantly improved (P<.001) in favor of groups 1 and 2. Importantly, the intra-ventricular dyssynchrony with speckle tracking was considerably less in group 1 and 2 patients. Tps-SL≤120ms was the optimal value to predict improvement in functional capacity following high to mid-septal pacing locations. There was significant improvement of functional capacity after RV pacing in high and mid-septal locations compared with low septal location. This was associated with a lesser degree of dyssynchrony in favor with mid- to high septal location.

Adverse Consequences of Right Ventricular Apical Pacing and Novel Strategies to Optimize Left Ventricular Systolic and Diastolic Function.

Several studies have focused on the deleterious consequences of Right Ventricular Apical (RVA) pacing on Left Ventricular (LV) function, mediated by pacing-induced ventricular dyssyn-chrony. Therapeutic strategies to reduce the detrimental consequences of RVA pacing have been pro-posed, that includes upgrading of RVA pacing to Cardiac Resynchronization Therapy (CRT), alterna-tive Right Ventricular (RV) pacing sites, minimal ventricular pacing strategies, as well as atrial-based pacing. In developing countries, single chamber RV pacing still constitutes a majority of cases of permanent pacing, and assessment of the optimal RV pacing site is of paramount importance. In chronically-paced patients, it is crucial to maintain as close and normal LV physiological function as possible, by minimizing ventricular dyssynchrony, reducing the chances for heart failure and other complications to develop. This review provides an analysis of the deleterious immediate and long-term consequences of RVA pacing, and the most recent available evidence regarding improvements in pacing options and strategies to optimize LV diastolic and systolic function. Furthermore, the place of advanced echocardiography in the identification of patients with pacing-induced LV dysfunction, the potential role of a new predictor of LV dysfunction in RV-paced subjects, and the long- term out-comes of patients with RV septal pacing will be explored

Acute right ventricular resynchronization improves haemodynamics in children after surgical repair of tetralogy of Fallot.

Right bundle branch block is associated with right ventricular (RV) electromechanical dyssynchrony, which may contribute to acute haemodynamic impairment after repair of tetralogy of Fallot (ToF). We sought to evaluate the effects of RV resynchronization on haemodynamics and tissue oxygenation during the first 24 h after surgery. Arterial pressures, cardiac output, and tissue oxygenation were measured in 28 consecutive patients (median age 10.1 months) during baseline sinus rhythm with right bundle branch block and after RV resynchronization by atrial-triggered RV free wall pacing in complete fusion with spontaneous activation. Studied variables were compared in a crossover design in four 5-min intervals (baseline rhythm and stimulation, 2x each). Resynchronization reduced the QRS complex duration from median 110 to 70 ms (P < 0.001), increased significantly median arterial systolic, mean and pulse pressure, cardiac index, left ventricular maximum +dP/dT and decreased central venous pressure (P < 0.001 for all). Both cerebral and renal oxygenation improved (P < 0.001). Eleven of the 28 patients showed a clinically highly significant resynchronization effect defined as an increase in arterial pulse pressure of ≥ 10%. The q-RV interval (expressed as % of QRS duration) at the RV pacing site during baseline rhythm was the only predictor of resynchronization effect. RV resynchronization carried short-term improvement of haemodynamics in children early after surgery for ToF and might be a useful non-pharmacologic adjunct to the management of haemodynamically compromised patients. Resynchronization effect was maximized when pacing from area of the latest RV activation.

Effect of Right Ventricular Pacing on Right Ventricular Mechanics and Tricuspid Regurgitation in Patients With High-Grade Atrioventricular Block and Sinus Rhythm (from the Protection of Left Ventricular Function During Right Ventricular Pacing Study)

Right ventricular (RV) pacing has been linked with lead-induced tricuspid regurgitation (TR), left ventricular (LV) dysfunction, and dyssynchrony, but the effect of pacing on RV function is unclear. We sought to investigate the effect of pacing on RV synchrony, RV function, and TR, and their association with LV function. In this substudy of the PROTECT-PACE (Protection of left ventricular function during right ventricular pacing) study of the effects of RV pacing in patients with preserved ejection fraction, 145 patients (76 RV apex and 69 non-RV apex pacing) had measurable RV parameters. We assessed tricuspid annular plane systolic excursion (TAPSE), time difference between peak TAPSE and peak mitral annular plane systolic excursion (TM-APSE-dif), global LV longitudinal strain, E/e', TR vena contracta, and TR peak gradient. Echocardiography was performed just after implantation and at 2 years. TR parameters significantly worsened after 2 years, but pacing site was not associated with changes in RV and TR parameters. No temporal change in TAPSE and TM-APSE-dif was observed overall, but worsening of TM-APSE-dif was associated with worsening TAPSE. Global longitudinal strain and E/e' both deteriorated over 2 years; these changes were significantly associated. In a multivariate regression, worsening global longitudinal strain and worsening TM-APSE-dif were significantly associated with deterioration of TAPSE. Furthermore, increased E/e' and its deterioration were associated with worsening TR vena contracta and TR peak gradient, respectively. Decreased TAPSE was also associated with deterioration of TR vena contracta. In conclusion, RV pacing appears to worsen TR, an effect which might be caused by elevated LV filling pressure due to LV dysfunction. In this study, RV pacing did not affect RV function during 2-year follow-up, but such an effect might occur if RV dyssynchrony or LV dysfunction occurred after pacing. The effect of RV pacing site on RV and TR mechanics was minor.

The paced electrocardiogram cannot be used to identify left and right ventricular pacing sites in cardiac resynchronization therapy: validation by cardiac computed tomography.

Paced electrocardiogram characteristics to confirm left ventricular (LV) and right ventricular (RV) pacing sites in cardiac resynchronization therapy (CRT) have not been validated with accurate knowledge of pacing lead positions. We aimed to evaluate the ability of the paced QRS morphology to differentiate between various LV and RV lead positions using cardiac computed tomography (CT) as the reference for LV and RV pacing site. Ninety-seven CRT patients were included. The QRS morphology was evaluated during forced LV-only and RV-only pacing. Pacing lead positions were assessed in a standard LV 16-segment model and a simplistic RV 6-segment model using cardiac CT. Ten patients with LV lead displacement or a LV pacing site outside the non-apical free wall were excluded from the analysis of the LV paced QRS complex. Pacing within the LV free wall was associated with a superior and a right-axis deviation (P = 0.02 and 0.04, respectively). Pacing from basal LV segments mainly produced a late (V5 or later) precordial QRS transition as compared with mid-LV pacing (P = 0.001). No significant associations were found between RV pacing site and QRS axis or precordial transition. Different QRS morphologies were observed during single-chamber pacing from identical LV or RV myocardial segments. Weak associations exist between LV and RV pacing sites and the paced QRS axis. None of the paced QRS characteristics can be used to reliably confirm specific LV and RV pacing sites in CRT patients.

EFFECT OF PACEMAKER SITE ON B-TYPE NATRIURETIC PEPTIDE LEVELS AND LEFT VENTRICULAR FUNCTION

There is increasing evidence that conventional right ventricular (RV) apical pacing may have detrimental effects on cardiac structure and left ventricular (LV) function. This study investigated the contribution of RV pacing sites to the cardiac function, comparing plasma B-type natriuretic peptide (

Capturing the His‐Purkinje System is Not Possible from Conventional Right Ventricular Apical and Nonapical Pacing Sites

Direct His bundle capture may negate ventricular electrical dyssynchrony induced by right ventricular (RV) apical pacing. We sought to evaluate if direct His bundle pacing is possible with conventional pacemaker lead implantation at various sites in the RV. Consecutive patients underwent RV pacing using standard implantable active fixation pacing leads in a random order in the RV outflow tract, middle RV, and RV apex at stimulation threshold and at increasing voltages of 2.5, 5, 7.5, and 10 volts (V). At each location, QRS width and morphology on 12-lead electrocardiograph (ECG) were compared in sinus and paced rhythm at the different voltages. Twelve patients underwent a total of 2,160 paced QRS measurements. Progressive increases in stimulation voltage did not change QRS morphology or duration regardless of site of pacing (RV outflow tract, middle RV, and RV apex) in any of the 12 ECG leads. In addition, apart from the stimulation threshold between the RV outflow tract and RV apex, there was no statistically significant difference in QRS duration between the three pacing sites. In patients with a baseline normal QRS duration, none of the three conventional RV pacing sites were able to produce QRS narrowing and capture the His-Purkinje system. Furthermore, based on paced QRS duration as an indirect surrogate of electrical LV dyssynchrony, there was no clear advantage of one pacing site over another.

Impact of interlead distance on immediate and mid-term response to cardiac resynchronization therapy

Objectives. It is currently recommended that the left ventricular (LV) lead be placed at the posterolateral or lateral wall of heart during cardiac resynchronization therapy (CRT). The aim of our study is to evaluate the influence of interlead distance on immediate and mid-term response to CRT with altered right ventricular (RV) pacing site. Design. A total of 35 consecutive patients underwent CRT for standard indications. RV pacing site was altered from RV outflow tract (RVOT) to RV apex (RVA) in the course of implantation, permitting assessment of a “poorer response” and a “better response” site based on intraprocedural aortic velocity time integral (aVTI). LV–RV interlead distances were compared between these sites during operation. We also made a comparison of the interlead distances between responders and non-responders 6 months after CRT. Results. In the process of CRT implantation, the better response site showed significantly larger interlead distance (16.5 ± 4.4 cm vs.12.4 ± 5.6 cm, p = 0.001) as well as its vertical component (9.8 ± 4.8 cm vs. 4.3 ± 2.8 mm, p = 0.001) on lateral fluoroscopy view as compared with the poorer response site. Furthermore, RVA proved more likely to be the “better response” site than RVOT (91% vs. 9%, p = 0.001). At 6-month -up, responders demonstrated larger direct interlead distance (18.1 ± 4.5 cm vs. 14.8 ± 3.5 cm, p = 0.011) and horizontal interlead distance (14.1 ± 6.6 cm vs. 8.3 ± 6.1 cm, p = 0.004) on the lateral radiograph in comparison with non-responders with great significance. Conclusions. Larger interlead distance on lateral fluoroscopy view is associated with more favorable immediate and mid-term response to CRT. Use of these findings may help to maximize the benefit derived from CRT.

Long‐Term Effect of Septal or Apical Pacing on Left and Right Ventricular Function after Permanent Pacemaker Implantation

Right ventricular (RV) pacing is associated with left ventricular (LV) dysfunction. However, the effects of RV pacing at different sites on both LV and RV function have rarely been studied before. We want to determine whether different RV pacing sites differentially affect LV and RV deformation by using speckle tracking echocardiography (STE). The subjects were 73 patients who had undergone dual-chamber permanent pacemaker implantation and did not have structural heart diseases. LV and RV global longitudinal strains (GLS) were measured using STE to determine subtle changes in LV function. Twenty-three patients without pacing after pacemaker implantation served as controls; 14 and 36 patients showed apical and septal pacing, respectively. There were no significant intergroup demographic differences. LV biplane ejection fractions in the septal- and apical-pacing groups were significantly lower than those in the controls. The GLS LV values were similar between the control and septal-pacing groups, but they were lower in the apical-pacing group. Multivariate analysis revealed that cumulative pacing loads and apical pacing were independent factors associated with lower GLS LV values. The GLS RV values were similar between the control and apical-pacing groups; however, they were lower in the septal-pacing group. We concluded that patients with septal pacing have significantly higher GLS LV and more modest decreases in GLS RV values than patients with apical pacing. Thus, septal pacing may be not necessarily preferable in patients without significant heart disease undergoing dual-chamber permanent pacemaker implantation.

His-Purkinje System Capture is not Possible From Conventional Right Ventricular Apical and non-Apical Pacing Sites

Introduction: Direct His bundle capture may allow physiological activation of the heart and negate the adverse electrical dyssynchrony induced by right ventricular (RV) apical pacing. Our aim was to investigate if direct His bundle pacing was possible from conventional RV pacing sites.

Right Ventricular Pacing, Mechanical Dyssynchrony, and Heart Failure

Cardiac pacing is a common treatment option for patients with sick sinus syndrome or atrioventricular block, with the ventricular pacing lead often secured in the convenient right ventricular (RV) apical location. While RV pacing reduces symptoms and limitations associated with heart block, it may have detrimental effects on cardiac structure and function, leading to heart failure (HF) in some patients. RV pacing creates electrical dyssynchrony similar to a left-bundle branch block, with conduction occurring cell-by-cell rather than through the His-Purkinje network. Studies have shown that impairment of myocardial metabolism, structure, and function related to RV pacing occurs regionally (most prominently near the pacing site) and globally, within the left ventricle. Strategies being studied to prevent or treat pacing-induced intraventricular mechanical dyssynchrony and HF include: initial biventricular rather than RV pacing in selected patients, programming to avoid or minimize RV pacing, use of alternate (non-apical) RV pacing sites, echocardiographic screening for development of pacing-induced dyssynchrony and HF, and upgrade to biventricular pacing.

Abstract 9430: Right Ventricular Apical and Free Wall Pacing, but Not Ventricular Septal Pacing Leads to Left Ventricular Reverse Rotation

Background: Although left ventricular (LV) twisting has been recognized to play an important role in LV function, the impact of right ventricular (RV) pacing on LV twisting including rotational abnormality has not been fully understood. We investigated the influence of the pacing site on the rotational abnormality in patients underwent pacemaker implantation. Methods and Results: We evaluated 21 patients who underwent permanent pacemaker implantation for sick sinus syndrome or atrioventricular block (age 79 years) with preserved systolic function. According to RV pacing site, we divided our patients into septal pacing group (n=10) and non-septal (free wall or apex) pacing group (n=11). Rotation in the apical LV was evaluated using speckle tracking image in echocardiogram and the clockwise rotation of the apical wall or/and the counterclockwise rotation of the basal wall were defined as reverse rotation. We assessed LV rotational abnormality, under own beats or/and RV pacing rhythm. Results: During own beats, only one patient (1/21= 5%) with incomplete right branch block and atrial flutter demonstrated reverse rotation. In contrast, during RV pacing rhythm, 9 patients (9/21=43%) exhibited reverse rotation, in whom there were 8 patients in non-septal pacing group and 1 patient in septal pacing group. Reverse rotation was observed more in non-septal pacing group than in septal pacing group. Conclusions: RV apical or free wall pacing could induce the reverse rotation of the LV wall while RV septal pacing preserved LV rotation.

Right ventricular lead positioning does not influence the benefits of cardiac resynchronization therapy in patients with heart failure and atrial fibrillation

Little is known about the optimal right ventricular (RV) pacing site in cardiac resynchronization therapy (CRT). This study compares bi-ventricular pacing at the left ventricular (LV) free wall combined with two different RV stimulation sites: RV outflow tract (RVOT+LV) vs. RV-apex (RVA+LV). Thirty-three patients (32 males) with chronic heart failure, NYHA class III-IV, optimal drug therapy, QRS-duration ≥150 ms, and chronic atrial fibrillation (AF) received CRT with two different RV leads, in the apex (RVA) or outflow tract (RVOT), together with an LV lead, all connected to a bi-ventricular pacemaker. Randomization to pacing in RVOT+LV or RVA+LV was made 1 month after implantation and cross-over to the alternate pacing configuration occurred after 3 months. The median age of patients was 69 ± 10 years, the mean QRS was 179 ± 23 ms, and 58% of patients had ischaemic heart disease. Seven patients had pacemaker rhythm at inclusion and 60% were treated with atrioventricular-junctional ablation before randomization. In the RVA+LV and RVOT+LV pacing modes, 67 and 63% (nonsignificant) responded symptomatically with a decrease of at least 10 points in the Minnesota Living with Heart Failure score. The secondary end-points (6-min walk test, peak oxygen uptake, N-Terminal fragment of B-type Natriuretic Peptide, and left ventricular ejection fraction) showed significant improvement between baseline and CRT, but not between RVOT+LV and RVA+LV. In this randomized controlled study, the exact RV pacing site, either apex or outflow tract, did not influence the benefits of CRT in a group of patients with chronic heart failure and AF. ClinicalTrials.gov ID: NCT00457834.

Alternate Site Right Ventricular Pacing: Defining Template Scoring

Prolonged right ventricular (RV) apical pacing produces dysynchronous ventricular contraction, which may result in left ventricular (LV) dysfunction, whereas septal pacing sites might reflect a more synchronous LV activation. This study examined a method of evaluating alternate RV pacing sites using a template scoring system based on measuring the angle of lead attachment in the 40° left anterior oblique (LAO) fluoroscopic view and its effect on altering the loop of lead in the RV. Twenty-three consecutive patients for RV pacing were enrolled. Conventional active fixation leads were positioned in either the RV outflow tract (RVOT) or mid RV using a stylet designed for septal placement (Model 4140, St. Jude Medical, St. Paul, MN, USA). Using LAO cine fluoroscopy, a generous loop of lead was inserted into the RV chamber and the change in angle of attachment determined. Successful positioning of pacing leads at the RVOT septum (18 patients) and mid-RV septum (five patients) was achieved. With introduction of more lead into the RV chamber, the angle of attachment in the LAO projection altered over a range of 6°-32° for all patients with a mean of 14.6 ± 6.6°. In 87% of patients, the range was predominantly within the same template score with only minor overlap into another zone. This study shows that the angle of lead attachment in the RV is altered by introducing more lead, but in most cases, the template score remains the same. Further studies are required to determine the accuracy and efficacy of the templates.