Right Ventricular Apex Pacing Research Articles

Comparison of novel ventricular pacing strategies using an electro-mechanical simulation platform.

Focus of pacemaker therapy is shifting from right ventricular (RV) apex pacing (RVAP) and biventricular pacing (BiVP) to conduction system pacing. Direct comparison between the different pacing modalities and their consequences to cardiac pump function is difficult, due to the practical implications and confounding variables. Computational modelling and simulation provide the opportunity to compare electrical, mechanical, and haemodynamic consequences in the same virtual heart. Using the same single cardiac geometry, electrical activation maps following the different pacing strategies were calculated using an Eikonal model on a three-dimensional geometry, which were then used as input for a lumped mechanical and haemodynamic model (CircAdapt). We then compared simulated strain, regional myocardial work, and haemodynamic function for each pacing strategy. Selective His-bundle pacing (HBP) best replicated physiological electrical activation and led to the most homogeneous mechanical behaviour. Selective left bundle branch (LBB) pacing led to good left ventricular (LV) function but significantly increased RV load. RV activation times were reduced in non-selective LBB pacing (nsLBBP), reducing RV load but increasing heterogeneity in LV contraction. LV septal pacing led to a slower LV and more heterogeneous LV activation than nsLBBP, while RV activation was similar. BiVP led to a synchronous LV-RV, but resulted in a heterogeneous contraction. RVAP led to the slowest and most heterogeneous contraction. Haemodynamic differences were small compared to differences in local wall behaviour. Using a computational modelling framework, we investigated the mechanical and haemodynamic outcome of the prevailing pacing strategies in hearts with normal electrical and mechanical function. For this class of patients, nsLBBP was the best compromise between LV and RV function if HBP is not possible.

Optimizing diastolic filling by pacing in nonobstructive hypertrophic cardiomyopathy

Treatment options for symptomatic patients with nonobstructive hypertrophic cardiomyopathy (nHCM) are limited. The purpose of this study was to determine the effect of sequential atrioventricular (AV) pacing, from different right ventricular (RV) sites with varying AV delays, on the diastolic function and functional capacity of patients with nHCM. Twenty-one patients with symptomatic nHCM and normal left ventricular (LV) systolic function were prospectively enrolled. Inclusion criteria included PR interval >150 ms, E/e' ≥15, and an indication for implantable cardioverter-defibrillator (ICD) implantation. Doppler echocardiographic study was performed during dual-chamber pacing at various AV intervals. Pacing was performed at 3 RV sites: RV apex (RVA), RV midseptum (RVS), and RV outflow tract (RVO). The site and sensed AV delay (SAVD) at which optimal diastolic filling occurred were chosen based on diastolic filling period and E/e'. During ICD implantation, the RV lead was implanted at the site identified by the pacing study. Devices were programmed in DDD mode at the optimal SAVD. During follow-up, diastolic function and functional capacity were assessed. Among the 21 patients (age 47.8 ± 7.7 years; 81.0% male), baseline E/A and E/e' were 2.4 ± 0.6 and 17.2 ± 2.2, respectively. There was an improvement in diastolic function (E/e') in 18 patients (responders) when pacing from the RVA (12.9 ± 3.4; P <.001) than from the RVS (16.6 ± 2.3) and RVO (16.9 ± 2.2). Among responders, optimal diastolic filling occurred at SAVD of 130-160 ms with RVA pacing. Nonresponders had longer duration of symptoms (P = .006), lower LV ejection fraction (P = .037), and higher late gadolinium enhancement burden (P <.001). During 13.5 ± 1.5 months of follow-up, there was an improvement (Δ) in diastolic function (E/e' -4.1 ± 0.5), functional capacity (New York Heart Association functional class -1.5 ± 0.3), and reduction in N-terminal pro-brain natriuretic peptide level (-55.6 ± 12.3 pg/mL) compared to baseline. Pacing at an optimized AV delay from the RVA improves diastolic function and functional capacity in a subset of patients with nHCM.

PO-05-110 MULTI-CONTACT LEAD TO FACILITATE LEFT BUNDLE BRANCH PACING

Left bundle branch pacing (LBBP) has emerged as a preferred physiological pacing approach, however it is constrained by difficult implantation techniques and inconsistent LBB capture. Therefore, to facilitate LBBP and to improve implantation success, a novel pacing lead specifically for cardiac conduction system pacing that addresses these limitations is necessary. Develop a multi-contact lead (MCL) to facilitate pacing the conduction system at low threshold. A novel lead with five contacts at the distal end was designed and prototyped with fine silver wire wrapped around a central stainless-steel shaft. Insulation was removed from the silver wire with an Ultraviolet laser. The contacts were spaced apart from each other at distances ranging from 0.2 mm to 1.0 mm. The MCLs were tested on five isolated, perfused adult canine hearts. The right ventricular (RV) septum was exposed by opening the RV and leads were inserted from the RV septum to near the left ventricular (LV) septal surface. A standard clinical lead (Medtronic 3830) was also implanted from the RV septal surface. RV apex pacing was performed with a pair of pacing wires. Pacing thresholds for LBB capture were determined and QRS duration was measured from the pseudo-ECG recorded in perfusion bath. LBB capture was achieved for the standard lead and all combinations of MCL. LBB capture threshold was lower for the lowest combination of contacts on MCL compared to the standard 3830 lead values (0.68 ± 0.3 V vs. 1.63 ± 0.7 V, respectively, P < 0.01, Fig A). LBB capture was verified by comparing the shortest MCL QRS duration in each study with sinus rhythm and right ventricular pacing QRS durations (63.8 ± 9.6, 56.4 ± 5.9, and 106.8 ± 16.7 ms, respectively, Fig B). The novel MCL has the potential to facilitate the physiologic pacing process of LBBP. MCL enables a narrowly paced QRS complex and a low pacing capture threshold with a high success rate.

Ventricular anatomical complexity and sex differences impact predictions from electrophysiological computational models.

The aim of this work was to analyze the influence of sex hormones and anatomical details (trabeculations and false tendons) on the electrophysiology of healthy human hearts. Additionally, sex- and anatomy-dependent effects of ventricular tachycardia (VT) inducibility are presented. To this end, four anatomically normal, human, biventricular geometries (two male, two female), with identifiable trabeculations, were obtained from high-resolution, ex-vivo MRI and represented by detailed and smoothed geometrical models (with and without the trabeculations). Additionally one model was augmented by a scar. The electrophysiology finite element model (FEM) simulations were carried out, using O'Hara-Rudy human myocyte model with sex phenotypes of Yang and Clancy. A systematic comparison between detailed vs smooth anatomies, male vs female normal hearts was carried out. The heart with a myocardial infarction was subjected to a programmed stimulus protocol to identify the effects of sex and anatomical detail on ventricular tachycardia inducibility. All female hearts presented QT-interval prolongation however the prolongation interval in comparison to the male phenotypes was anatomy-dependent and was not correlated to the size of the heart. Detailed geometries showed QRS fractionation and increased T-wave magnitude in comparison to the corresponding smoothed geometries. A variety of sustained VTs were obtained in the detailed and smoothed male geometries at different pacing locations, which provide evidence of the geometry-dependent differences regarding the prediction of the locations of reentry channels. In the female phenotype, sustained VTs were induced in both detailed and smooth geometries with RV apex pacing, however no consistent reentry channels were identified. Anatomical and physiological cardiac features play an important role defining risk in cardiac disease. These are often excluded from cardiac electrophysiology simulations. The assumption that the cardiac endocardium is smooth may produce inaccurate predictions towards the location of reentry channels in in-silico tachycardia inducibility studies.

Reversal of pacing-induced cardiomyopathy after left bundle branch area pacing: a case report

BackgroundConventional right ventricular apex (RVa) pacing increases the risk of pacing-induced cardiomyopathy (PICM), especially in elderly patients with a higher ventricular pacing burden. Left bundle branch area pacing (LBBAP) has been suggested as an alternative to conventional RVa pacing. However, there is a lack of evidence that LBBAP may reverse PICM. We report a case of a reversal of PICM after LBBAP.Case presentationAn 81-year-old woman with a history of complete atrioventricular block and baseline QRS duration of 142 ms received permanent pacemaker implantation with dual pacing. The ventricular lead was placed at the apical direction and paced QRS duration was 146 ms. After 8 months, the patient visited with acute heart failure. The patient’s ventricular pacing burden was > 99%, and echocardiography found severe depression of left ventricular ejection fraction (LVEF, 30%), left ventricular dyssynchrony, and global hypokinesia. Despite 3 months of optimal medical management of heart failure, there was minimal improvement in LVEF (35%) and ventricular dyssynchrony persisted. The patient's presentation was consistent with PICM. LBBAP was performed with a stylet-driven lead and a delivery sheath (Biotronik Selectra 3D, Biotronik, Berlin, Germany). The lead was placed at the area of the left bundle branch trunk and non-selective LBBAP was achieved with a left ventricular activation time of 71 ms, paced QRS duration of 110 ms, and bipolar stimulation to QRS end of 136 ms. After a month, echocardiography found improved LVEF (53%) and N-terminal Pro-B-Type natriuretic peptide was decreased from 1011 to 645 pg/mL. The patient was relieved from dyspnea.ConclusionsWe report a case that PICM was resolved after LBBAP. LBBAP could be a rescue therapy for PICM induced by conventional RVa pacing.

Influence of non-apical permanent pacing on left ventricular systolic impairment

Abstract Funding Acknowledgements Type of funding sources: None. Background Right ventricular apical (RVA) pacing deleterious effects on left ventricular ejection fraction (LVEF) had been demonstrated. Non-apical pacing, such as right ventricular mid-septal (RVMS) and His Bundle pacing, appear as practical alternatives. Our purpose is to evaluate the effect of alternate sites of right ventricular (RV) pacing on left ventricular (LV) function and hemodynamics in patients with bradyarrhythmias. Methods We observed 118 patients (age 58±27 years, 64% men) with AV block III, who underwent permanent dual chamber pacemaker implantation. To 72 patients RV lead has implanted the middle area of RV septum (RVMS) and 46 patients’ RV lead has been implanted traditionally to the right ventricular apex (RVA). Color tissue velocity imaging was performed to analyze time to peak systolic velocity (Ts) in a 12 segment model of the LV for each pacing site. Measurements included standard deviation of time to peak systolic velocity (SD-Ts) for all segments, the maximal difference in Ts between any 2/6 basal (Ts-B), any 2/6 mid segments (Ts-M) and maximal Ts difference between any 2/12 segments (Ts-12). Stroke volume was estimated using Doppler velocity time integral (TVI) in the left ventricular outflow tract (LVOT). QRS width for each site was recorded. Measurements were observed by transthoracic echocardiography and electrocardiography before and 12 months after implantation. Results Ts-12 was significantly higher with RVA - pacing (107 ms, p=0.003) compared to RVMS - pacing (81 ms) sites. SD-Ts were significantly higher with RVA - pacing (38.5 ms, p=0.01) than RVMS - pacing (28.7 ms). QRS duration was the longest for RVA - pacing (157 ms) while significantly shorter RVMS - pacing (115 ms, p&amp;lt;0.001). LVOT VTI was significantly higher for RVMS - pacing than for RVA (p=0.0014) pacing. Conclusions Right ventricular mid-septal pacing may reduce electro-mechanical dyssynchrony compared to RVA pacing and RVMS – pacing to effect better LV function and hemodynamics than RVA pacing in patients with permanent pacemaker implantation.

Evaluation of electrophysiological characteristics and ventricular synchrony: An intrapatient-controlled study during His-Purkinje conduction system pacingversus right ventricular pacing.

Objectives to BackgroundTo compare electromechanical ventricular synchrony when pacing from different sites, including right ventricular apex pacing (RVAP), right ventricular septum pacing (RVSP), His bundle pacing (HBP), left bundle branch pacing (LBBP), and RVSP during unipolar pacing from the ring electrode of LBBP lead (RVSPring) in each patient and evaluate the correlations between electrophysiological characteristics and ventricular synchrony.MethodsTwenty patients with complete atrioventricular block indicated for dual‐chamber pacemaker implantation were included in the study. Unipolar pacing at different sites, including RVAP, RVSP, HBP, LBBP, and RVSPring, was successively performed in each patient. The pacing characteristics and echocardiogram parameters were collected and compared among intrinsic rhythm and pacing at different sites.ResultsSimilar to HBP (114.84 ± 18.67 ms), narrower paced QRSd was found in LBBP (116.15 ± 11.60 ms) as compared to RVSPring (135.11 ± 13.68 ms), RVSP (141.65 ± 14.26 ms), and RVAP (160.15 ± 19.35 ms) (p < .001). LBBP showed comparable pacing parameters to RVAP or RVSP and was significantly better than HBP, with maintained cardiac function. TS‐12‐SD was significantly improved in LBBP (41.80 ± 20.97 ms) than RVAP (69.70 ± 32.42 ms, p = .003) and RVSP (63.30.56 ± 32.53 ms, p = .018) but similar to HBP (51.50 ± 25.67 ms, p = .283) or RVSPring (57.80 ± 25.65 ms, p = .198). Among these pacing strategies, negative values of interventricular mechanical delay (IVMD) were only identified in LBBP (−19.25 ± 18.43 ms), significantly different from RVAP (35.00 ± 30.72 ms), RVSP (22.85 ± 22.05 ms), HBP (5.20 ± 18.64 ms), and RVSPring (16.00 ± 26.76 ms (all p < .05). Using Pearson's analysis, Sti‐LVAT was positively correlated with QRS duration, IVMD, TS‐12‐SD, LVEDV, and LVESV, while a negative relationship could be observed for left ventricular ejection fraction.ConclusionsHis‐Purkinje conduction system pacing (HPCSP) achieved better electrical and mechanical synchrony than conventional RV pacing. For interventricular synchrony, only LBBP initiated earlier LV activation than RV, in accordance with the right bundle branch block (RBBB) pattern of paced QRS during LBBP. Sti‐LVAT might be a good parameter correlating with LV systolic function and mechanical synchrony.

Initial clinical experience of left bundle branch pacing after transcatheter aortic valve implantation

Objective: To investigate the efficacy and safety of left bundle branch pacing(LBBP) in patients after transcatheter aortic valve implantation (TAVI). Methods: This is a retrospective study. A total of 35 patients underwent TAVI and received pacemaker implantation from January 2018 to December 2020 in Beijing Fuwai Hospital were enrolled. Patients were divided into LBBP group (n=12) and right ventricular apex pacing (RVAP) group (n=23) according to the pacing position. The success rate of operation in LBBP group was calculated, and the occurrence of complications were observed, and the parameters of pacemaker were measured on the 3rd day and 1, 3 and 6 months after operation. The N-terminal pro-B-type natriuretic peptide (NT-proBNP), echocardiographic and ECG indexes were compared between the two groups on the 3rd day and 1, 3, and 6 months after pacemaker implantation. Result: A total of 35 patients were included, The age was (76.4±7.7) years, including 19 males (54.3%). The procedure time ((86.58±17.10)min vs. (68.74±9.18)min, P<0.001) and fluoroscopy duration ((20.08±4.44)min vs. (17.00±2.26)min, P<0.001) were significantly longer in LBBP group compared with RVAP group. The operation success rate of LBBP group was 11/12. There was no serious operation related complications such as pneumothorax, hemothorax, electrode dislocation, infection, and lower limb bleeding. The patients were followed up for 7.43 (5.21, 9.84) months. The programmed parameters of pacemaker were in the ideal range and stable during follow-up. At 3 and 6 months after operation, the left ventricular ejection fraction in LBBP group was higher than that in RVAP Group (at 3 months: (60.75±2.89)% vs. (57.35±3.33)%, P=0.004; at 6 months: (63.17±3.33)% vs. (56.17±3.97)%, P<0.001), NT-proBNP values was lower in LBBP group than that in RVAP Group (at 3 months: 822 (607, 1 150)ng/L vs. 1 052 (902, 1 536)ng/L, P=0.006; at 6 months: 440 (330,679)ng/L vs. 783 (588, 1 023)ng/L, P=0.001). At 1, 3 and 6 months after operation, the QRS duration was shorter in LBBP group than that in RVAP group (1 month: 99 (97, 107)ms vs. 126(124, 130)ms, P<0.001; 3 months: 98(96, 105)ms vs. 129(128, 133)ms, P<0.001; 6 months: 96(94, 104)ms vs. 130(128, 132)ms, P<0.001). Conclusions: For patients with permanent pacemaker indications after TAVI, LBBP is feasible, safe and reliable. It could improve the cardiac function in the short term, the long-term effect of LBBP needs to be further observed.

Abstract 11164: Better Electromechanical Synchrony During Left Bundle Branch Pacing and His Bundle Pacing as Compared to Right Ventricular Pacing in Atrioventricular Block

Objectives: To compare electromechanical ventricular synchrony when pacing from different sites including right ventricular apex pacing (RVAP), right ventricular septum pacing (RVSP), His Bundle pacing (HBP), left bundle branch pacing (LBBP) and RVSP during unipolar pacing from the ring electrode of LBBP lead (RVSP ring ) in each patient during implantation. Methods: Twenty patients with complete atrioventricular block (AVB) indicated for dual-chamber pacemaker implantation were included. Unipolar pacing at different sites including RVAP,RVSP,HBP,LBBP and RVSP ring were successively performed in each patient while pacing characteristics and echocardiogram parameters were collected and compared. Results: Similar to HBP, narrower paced QRSd was found in LBBP as compared to RVSP ring , RVSP and RVAP(p&lt;0.001). LBBP showed comparable pacing parameters to RVAP or RVSP and were significantly better than HBP, with maintained cardiac function. For ventricular mechanical synchrony, TS-12-SD was significantly improved in LBBP(27.00±21.53ms) than RVAP(54.05±34.21ms, p=0.004) and RVSP(47.56±33.26ms, p=0.029) but similar to HBP or RVSP ring . Among these pacing strategies, negative values of interventricular mechanical delay(IVMD) were only identified in LBBP(-20.16±18.47ms), significantly different from RVAP(33.68±30.98ms), RVSP (21.68±22.02ms), HBP (4.74±19.04ms) and RVSP ring (14.56±26.76ms(all p&lt;0.001). Using Pearson’s analysis, Sti-LVAT was found to be positively corelated with QRS, IVMD, TS-12-SD, LVEDV and LVESV while a negative relationship could be observed for LVEF. Conclusions: Similar to HBP, LBBP achieved better electrical and mechanical left ventricular synchrony than conventional RV pacing. For interventricular synchrony, only LBBP initiated earlier LV activation than RV among these pacing strategies, in consistent with the RBBB pattern of paced QRS during LBBP.

Upgrade of cardiac resynchronization therapy by utilizing additional His-bundle pacing in a patient with lamin A/C cardiomyopathy: an autopsy case report.

Abstract Background A number of heart failure patients (HF) do not fully benefit from cardiac resynchronization therapy (CRT). Although His bundle pacing (HBP) have been developed as an alternative strategy, its role for treating advanced cardiomyopathy remains unclear. Case summary We previously reported a patient with lamin A/C cardiomyopathy (Eur Heart J Case Rep. 2020; 4:1-9). He had turned non-response to conventional biventricular pacing (BVP), and an upgrade to CRT combining para-His bundle pacing (HBP) and left ventricular (LV) pacing had markedly improved his HF status. In the present report, we assessed the autopsy and histological findings of this patient. A histological examination of both the LV and right ventricular (RV) apex pacing regions exhibited extensive scarring. Although a distinct conduction system was not identified in the alternative para-HBP region, the RV endocardium had more viable myocytes in this region. Discussion In patients with advanced cardiomyopathy accompanied by extensive fibrosis, RV apex pacing, delivered from scar tissue, can render conventional BVP ineffective. Additionally, HBP alone can not provide adequate resynchronization under the presence of diffuse injury of the His-Purkinje system. In these circumstances, combined para-HB and LV pacing may facilitate electrical and mechanical resynchronization of the ventricles and may be attributed to favourable CRT response in advanced HF, even if para-HBP fails to directly capture the conduction system.

Reversion of cardiac memory during left bundle branch pacing

Cardiac memory (CM) is identified as an altered T wave when normal ventricular activation resumes after an abnormal myocardial activation period. We present a case who initially underwent temporary right ventricular apex (RVA) pacing for one week which induced typical pseudo-primary T wave changes. The T wave inversion was observed after the end of RVA pacing when left bundle branch pacing (LBBP) was initiated, and the abnormal T waves gradually return to almost normal repolarization during LBBP 40 days later.

Differential pacing from two sites to diagnose risk of ventricular arrhythmia and death.

QRS abnormalities may not be apparent in sinus rhythm in electrically stable cardiomyopathy patients who can have quiescent but highly arrhythmogenic substrate. Here, we test the hypothesis that differential changes in QRS construction during right-ventricular apex pacing (RVP) as opposed to atrial pacing (AP) will identify latent substrate for ventricular arrhythmias (VA) and death. Forty patients with cardiomyopathy free of VA underwent baseline 114-electrode body-surface electrocardiogram during AP (100beats per minute [bpm]) and RVP (100 and 120bpm). The filtered-averaged QRS at each electrode was deconstructed into individual intra-QRS and post-QRS ventricular myopotentials (VMP ). The primary outcome was VA or death. Prognostic accuracy of VMP was validated using V1 to V6 leads in another prospective cohort of 44-cardiomyopathy patients. Twenty-six patients were eligible for initial analysis. After 5±2 years of follow-up, eight (31%) patients had VA (VAPos ) while rest were uneventful (VANeg ). During AP100 , VAPos patients expressed more VMP than VANeg patients (16±1vs 12±1, P=0.02). RVP100 and RVP120 in VAPos patients introduced an additional 5.5±0.5 and 6.0±0.5 VMP (P<0.0001vs AP100 ). The relative change with RVP120 versus AP100 in VANeg patients exceeded VAPos patients by 1.2±0.5 VMP (P=0.03). Increment in VMP count of<8 in lead-V5 with RVP120 compared to AP100 best predicted VA (area under curve 0.81, P=0.01). In the validation cohort, primary outcome occurred in 13 (33%) patients. Native QRS features and AP100 alone failed to predict primary outcome. Patients with increment in VMP count of<8 in lead-V5 with RVP120 versus AP100 had 7.9-fold increased risk of primary outcome (95% confidence interval 1.01, 61.61; P=0.049). Cardiomyopathy patients at risk of VA or death perturb the QRS less than low-risk patients with differential pacing. This functional response may be useful to identify arrhythmogenic substrate.

Effect of ventricular pacing lead position on tricuspid regurgitation: A randomized prospective trial

Pacing lead-related tricuspid regurgitation (TR), a recognized complication of ventricular pacing lead implantation, may be affected by lead position or diameter. This study sought to determine the effect of ventricular pacing lead position and diameter on pacing lead-related TR. A randomized prospective trial compared pacing leads in the right ventricular apex (RVA), right ventricular septum (RVS), or left ventricle via the coronary sinus (LV-CS) in a 1:1:1 fashion. Patients undergoing implantable cardioverter-defibrillator lead implantation in the RVA (RVA-ICD) were enrolled in a comparison group. Patients with preexisting moderate or greater TR were excluded. Prospective clinical evaluation, transthoracic echocardiograms, and device interrogation occurred 24 hours and 12 months after device implantation. Sixty-three patients undergoing pacemaker implantation were randomized to RVA, RVS, or LV-CS pacing, and 48 RVA-ICD patients were enrolled as a comparison group. At 12 months, 6patients (6.4%) developed moderate or greater TR. Moderate or greater TR was not significantly different between groups if analyzed by intention to treat (RVA 5.9%, RVS 10.0%, LV-CS 6.7%, and RVA-ICD 4.8%) or if analyzed by final lead location (RVA 4.8%, RVS 10.5%, LV-CS 8.3%, and RVA-ICD 5.1%). Ventricular lead-related complications occurred in 3 patients with right ventricular leads (3.2%) and 2 patients with LV-CS leads (11.1%) (P = .184). Neither pacing lead position nor diameter appears to affect TR development significantly. LV-CS leads failed to achieve a statistically significant reduction in TR as compared with right ventricular leads.

Deleterious acute and chronic effects of bradycardic right ventricular apex pacing: consequences for arrhythmic outcome.

In the chronic complete atrioventricular (AV) block dog (CAVB) model, both bradycardia and altered ventricular activation due to the uncontrolled idioventricular rhythm contribute to ventricular remodeling and the enhanced susceptibility to Torsade de Pointes (TdP) arrhythmias. We investigated the effect of permanent bradycardic right ventricular apex (RVA) pacing on mechanical and electrical remodeling and TdP. In 23 anesthetized dogs, serial experiments were performed at sinus rhythm (SR), acutely after AV block (AAVB) and 3weeks of remodeling CAVB at a fixed pacing rate of 60/min. ECG, and left (LV) and right ventricular (RV) monophasic action potentials durations (MAPD) were recorded; activation time (AT) and activation recovery interval (ARI) were determined from ten distinct LV electrograms; interventricular mechanical delay (IVMD) and time-to-peak strain (TTP) of the LV septal and lateral wall (ΔTTP: lateral wall minus septal wall) were obtained echocardiographically. Dofetilide (25μg/kg/5min) was infused to study TdP inducibility. In baseline AAVB, in comparison to SR, RVA bradypacing acutely increased QT interval, LV, and RVMAPD. Echocardiographic IVMD and ΔTTP were initially increased, which was partially corrected after 3weeks of RVA pacing (IVMD: 22±13 vs. 42±11 vs. 31±6ms; ΔTTP: -2±47 vs. -114±38 vs. -36±22ms). QT interval (362±23 vs. 373±29ms), LVMAPD (245±18 vs. 253±22ms), RVMAPD (226±26 vs. 238±31ms), and mean LV-ARI (268±5 vs. 267±6ms) were not significantly changed after 3weeks of RVA pacing. During AAVB, dofetilide increased mean LV-ARI (381±11ms) with largest increases in the later activated basal areas (slope AT-ARI: +0.96). In contrast with acute RVA pacing, 3week pacing increased TdP inducibility (0/13 vs. 11/21) and mean LV-ARI (484±18ms), while the slope of AT-ARI responded differently on dofetilide (-2.37), with larger APD increases in the early region. The latter was supported at the molecular level: reduced RNA expressions of three repolarization-related ion channel genes in early (KCNQ1, KCNH2, and KCNJ2) versus two in late regions (KNCQ1 and KCNJ2). In conclusion, bradycardic RVA pacing acutely induced LV intra- and interventricular mechanical dyssynchrony, which was partially reversed after 3weeks of pacing (remodeling). The latter occurred without apparent baseline electrical effects. However, dofetilide clearly unmasked (region-specific) arrhythmic consequences of remodeling.

Restoration of ventricular septal hypoperfusion by cardiac resynchronization therapy in patients with permanent right ventricular pacing

BackgroundPacing from the right ventricular apex (RVA) is associated with cardiac dysfunction and shows electrophysiological features similar to left bundle branch block in which left ventricular (LV) mechanical dyssynchrony impairs septal coronary artery perfusion. MethodsA total of 62 non-ischemic patients with an implanted pacemaker at the RVA with a pacing rate of >95% were studied. LV septal coronary perfusion as indicated by the LV septal perfusion index was measured by electrocardiography (ECG)-gated single-photon emission computed tomography for all patients at baseline and for patients who were upgraded to CRT at 6months after CRT. Relationships among LV septal perfusion index, QRS duration, and LV ejection fraction were analyzed. ResultsAmong the patients with permanent RVA pacing, 28 of 62 (45%) had impaired septal perfusion (i.e., septal perfusion index <0.9). The LV septal perfusion index was significantly correlated with both QRS duration (r=−0.763, p<0.001) and LV ejection fraction (r=0.462, p=0.001). Eleven patients were upgraded to CRT. CRT significantly improved the LV septal perfusion index from 0.63 (SD=0.13) to 0.89 (SD=0.19) (p<0.001)and cardiac function: LV end-systolic volume from 102.3mL (SD=70.0) to 179.7mL (SD=118.4) (p=0.002) and LV ejection fraction from 22.5 (SD=8.9%) to 38.4% (SD=13.9%) (p=0.001). ConclusionsNearly half of the non-ischemic patients with permanent RVA pacing presenting with prolonged QRS duration and LV dysfunction developed LV septal hypoperfusion. Both septal perfusion and LV function improved in patients who were upgraded to CRT.

96-34: Importance and Difference of Variability of Paced QRS Duration Caused by Right Ventricular Apex Pacing and Septal Pacing in Patients with Atrioventricular Block

Purpose: The variability of paced QRS duration (pQRSd) is sometimes recognized in the clinical situation. The aim of this study was to evaluate the importance of pQRSd and to assess effects of right ventricular septal (RVS) pacing compared with right ventricular apex (RVA) pacing in patients with atrioventricular block (AVB). Method: 181 consecutive new patients with a RV electrode due to high-degree AVB during the period from January 2004 to December 2013 were studied retrospectively. They were observed regularly at pacemaker (PM) clinic during at least 1 year. The sites of RVS were decided by chest X-ray and QRS morphology in II lead of the 12-lead electrocardiogram (ECG) as high septum (HS), mid septum (MS), and low septum (LS). Result: Mean age was 75.1 years and 99 were men. Mean follow-up was 5.2 years and 130 patients had a complete AVB. 77 patients received RVA pacing and 104 received RVS pacing. 153 patients had more than 50% as the percentage of ventricular pacing (%VP). In all patients, the mean pQRSd at PM implanting was 151ms and the mean pQRSd during follow-up period was 155ms. Although there was no significant difference between the intrinsic QRS duration in patients with RVA pacing and that in patients with RVS pacing, the mean pQRSd caused by RVS pacing was significantly narrower than that caused by RVA pacing and the difference had been recognized through an observation period (153ms vs. 159ms, p = 0.029). It needed 4.4 years to get the longest pQRSd on the average (8–4088 days). In patients with more than 50% as %VP, although there was no significant difference of pQRSd among sites in RVS, the rate of change of pQRSd (%pQRSd) caused by HS pacing was higher than that caused by MS and LS pacing (5.06% vs. 2.38%, p = 0.02). Similarly, %pQRSd caused by HS pacing tended to be higher than that caused by RVA pacing, MS and LS pacing (p = 0.059). In patients with ≧50% as %VP, there was no difference in probability of heart failure (HF) hospitalization between patients with RVS pacing and patients with RVA pacing. Furthermore there was no significant difference of the prognosis between patients with ≧150ms as pQRSd and with <150ms, but in patients with left ventricular (LV) dysfunction with LV ejection fraction (EF) less than 40% the probability of HF hospitalization in patients with ≧150ms as pQRSd was significantly worse than that in patients with <150ms (p = 0.04). Moreover, patients with LV dysfunction and prolonged pQRSd, that means %pQRSd was more than 0%, had significantly high provability of HF hospitalization (p = 0.03). On the other hand, each of LV dysfunction and PH affected HF hospitalization regardless of pacing site (p = 0.03 and p = 0.02), although antiarrhythmic agents did not bring any influence prognosis. Conclusion: Each of pacing sites in RV or pQRSd did not any affect on prognosis in patients with AVB. The pQRSd and %pQRSd are important in patients with LV dysfunction, so HS should not be selected in patients with LV dysfunction because HS pacing brings high %pQRSd. And pQRSd changes for a long term, so that it should be observed carefully.

Study of left ventricular diastolic function in patients with DDD pacemaker implantation for sick sinus syndrome during atrioventricular conduction and right ventricular apex pacing mode

Objective To analyze the left ventricular (LV) diastolic function parameters of patients with sick sinus syndrome (SSS) and DDD pacemaker implantation during atrioventricular conduction (AVC) and right ventricular apex pacing (RVAP) mode. Methods Forty-six consecutive patients with SSS who had undergone DDD pacemaker implantation were studied. Fifty volunteers were selected as control group.Changing from AVC to RVAP mode, the acute effect on echocardiographic left ventricular diastolic function parameters, including mitral inflow PW parameters, mitral annulus tissue Doppler imaging parameters, left atrial volume index, and LV/apical/basal untwist parameters were measured. And all subjects were classified into normal diastolic function or three degrees of LV diastolic dysfunction. Results Compared with control group, both AVC and RVAP mode of patients with DDD pacemaker implantation resulted in the worsening of LV diastolic function as shown by (1) prolonged deceleration time of E wave, decreased descending slope of E wave, as well as decreased early diastolic velocity at the septal mitral annulus, (2) the decrease of LV/basal/apical untwist velocity, (3) the increase in the degree of diastolic dysfunction. Conclusions In patients with DDD pacemaker implantation, both AVC and RVAP mode are associated with the deterioration of LV diastolic function, which is particularly obvious in RVAP mode. Key words: Echocardiography; Cardiac pacemaker, artificial; Ventricular function, left

Study of left ventricular function in patients with DDD pacemaker implantation during atrioventricular conduction and right ventricular apex pacing mode

Objective To compare the left ventricular function parameters of patients with sick sinus syndrome (SSS) and DDD pacemaker implantation during atrioventricular conduction (AVC) and right ventricular apex pacing (RVAP) mode. Methods Forty-six consecutive patients with SSS who had undergone DDD pacemaker implantation were studied. Fifty volunteers were included as control group. Changing from AVC to RVAP mode, the acute effect on echocardiographic parameters, including LVEF, parameters of aortic/pulmonary artery pulse wave Doppler, and parameters of left ventricular twist by speckle tracking imaging were measured respectively. Pacemaker implantation duration and cumulative ventricular pacing proportion (Cum%VP) were recorded. The relationships of pacemaker parameter and above left ventricular function parameters were analyzed. Results Compared with control group, values of peak rotation in LV apex and LV twist were significantly lower during AVC and RVAP mode. The value of peak rotation in LV base showed no significant difference between three groups.Apical-basal rotation delay during RVAP was significantly longer than those during AVC and in control group respectively (P<0.05). LVEF during RVAP decreased statistically (P<0.05), but showed no difference during AVC, compared with the control group. The peak LV twist related positively with LVEF, and negatively with Cum% VP. Conclusions RVA pacing decreases left ventricular function, which is independent of asynchrony contraction patterns caused by pacing. LVEF, apical rotation and LV twist are more sensitive to demonstrate the LV dysfunction in patients with pacemaker implantation. LV twist related negatively with Cum% VP. Key words: Echocardiography; Sick sinus syndrome; Cardiac pacing, artificial; Ventricular function, left; Twist

Assessment of QT and JT Intervals in Patients With Left Bundle Branch Block.

BackgroundProlongation of the QT interval is considered a risk factor for cardiac adverse events and mortality. Left bundle branch block (LBBB) lengthens the QT interval. The corrected QT interval (QTc) is most likely overestimated because its prolongation is caused by increases in depolarization duration and not in repolarization.ObjectivesIn this study, we aimed to apply corrected JT interval (JTc) as an appropriate measure of ventricular repolarization for predicting QTc in a formula.Patients and MethodsThe study population consisted of 101 patients with sinus rhythm (SR) and narrow QRS complexes (< 120 milliseconds). All patients underwent electrophysiology studies or ablation. A diagnostic catheter was positioned in the right ventricular apex (RVA) to induce LBBB at two different cycle lengths (CLs; 600 and 700 mv). The intrinsic QRS complex, QT time, and JT time were measured during SR and subsequent RVA pacing. The JTc was derived simply by subtracting the QRS duration from the QTc.ResultsStimulation from the RVA increased the QTc from 456.20 ± 38.63 ms to 530.67 ± 47.73 ms at a CL of 600 (P < 0.0001) and to 502.32 ± 47.26 ms at 700 CL (P < 0.0001). JTc showed no significant changes with stimulation from the RVA (102.97 ± 11.35 ms vs. 103.59 ± 10.67 ms, P = 0.24). There was no significant correlation between JTc and QRS complex duration. A significant correlation was seen between QRS and QTc at both CLs. The ROC curve indicated that sensitivity of 80% and specificity of 67% were obtained with JTc duration of 92.6 ms.ConclusionsRight ventricular pacing increases the QT interval without increasing the JT interval. Our results confirm that JTc, as an index of repolarization, is independent of ventricular depolarization. Therefore, it can be applied for predicting QTc in patients with LBBB.

The Effect of Right Ventricular Apical and Nonapical Pacing on the Short- and Long-Term Changes in Left Ventricular Ejection Fraction: A Systematic Review and Meta-Analysis of Randomized-Controlled Trials.

The right ventricular apex (RVA) is the traditional lead site for chronic pacing but in some patients may cause impaired left ventricular (LV) systolic function over time. Comparisons with right ventricular nonapical (RVNA) pacing sites have generated inconsistent results and recent meta-analyses have demonstrated unclear benefit due to heterogeneity across studies. A systematic search for randomized controlled trials that compared LV ejection fraction (LVEF) outcomes between RVNA and RVA pacing was performed up to October 2014. Twenty-four studies (n = 1,628 patients) met the inclusion criteria. To avoid between study heterogeneity two homogenous groups were created; group 1 where studies reported a difference (in favor of RVNA pacing) and group 2 where studies reported no difference between pacing sites. For group 1, weighted mean difference between RVNA and RVA pacing in terms of LVEF at follow-up was 5.40% (95% confidence interval [CI]: 3.94-6.87), related in part to group one's RVA arm demonstrating a significant reduction (mean loss -3.31%; 95% CI: -6.19 to -0.43) in LVEF between study baseline and end of follow-up. Neither of these finding were seen in group 2. Weighted regression modeling demonstrated that inclusion of poor baseline LVEF (<40%) in combination with greater than 12 months follow-up was three times more common in group 1 compared to group 2 (weighted relative risk 2.82; 95% CI: 1.03-7.72; P = 0.043). In patients requiring chronic right ventricular pacing where there is inclusion of impaired baseline LVEF (<40%), RVA pacing is associated with deterioration in LV function relative to RVNA pacing.