Right Ventricular Outflow Tract Pacing Research Articles

Comparison of the Acute Effects of Different Pacing Sites on Cardiac Synchrony and Contraction Using Speckle-Tracking Echocardiography.

Background: Cardiac pacing in patients with bradyarrhythmia may employ variable pacing sites, which may have different effects on cardiac function. Left bundle branch pacing (LBBP) is a new physiological pacing modality, and the acute outcomes on cardiac mechanical synchrony during LBBP remain uncertain. We evaluated the acute effects of four pacing sites on cardiac synchrony and contraction using speckle-tracking echocardiography, and comparisons among four different pacing sites were rare.Methods: We enrolled 21 patients with atrioventricular block or sick sinus syndrome who each sequentially underwent acute pacing protocols, including right ventricular apical pacing (RVAP), right ventricular outflow tract pacing (RVOP), His bundle pacing (HBP), and left bundle branch pacing (LBBP). Electrocardiograms and echocardiograms were recorded at baseline and during pacing. The interventricular mechanical delay (IVMD), the standard deviation of the times to longitudinal peak strain during 17 segments (PSD), and the Yu index were used to evaluate ventricular mechanical synchrony. Layer-specific strain was computed using two-dimensional speckle tracking technique to provide in-depth details about ventricular synchrony and function.Results: Left ventricular ejection fraction (LVEF) and tricuspid annulus plane systolic excursion (TAPSE) were significantly decreased during RVAP and RVOP but were not significantly different during HBP and LBBP compared with baseline. RVAP and RVOP significantly prolonged QRS duration, whereas HBP and LBBP showed non-significant effects. IVMD and PSD were significantly increased during RVAP but were not significantly different during RVOP, HBP, or LBBP. LBBP resulted in a significant improvement in the IVMD and Yu index compared with RVAP. No significant differences in mechanical synchrony were found between HBP and LBBP.Conclusion: Among these pacing modalities, RVAP has a negative acute impact on cardiac synchrony and contraction. HBP and LBBP best preserve physiological cardiac synchrony and function.

Left bundle branch pacing: efficacy and safety compared to right ventricular outflow tract pacing

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Patients with preserved left ventricular ejection fraction (LVEF) and atrioventricular block (AVB) who are anticipated for high-burden of right ventricular (RV) pacing possess a risk to develop pacing-induced cardiomyopathy and adverse clinical outcomes. Left bundle branch pacing (LBBP) has recently emerged as a mode of conduction system pacing in the quest for physiological pacing. Purpose The aim of our study was to assess LBBP feasibility and safety compared to right ventricular outflow tract pacing (RVOTP). Methods Single centre randomized clinical trial to investigate acute success, feasibility and safety of LBBP versus RVOTP. May to October 2020. Patients with pacemaker indication and preserved LVEF were randomized 1:1 and followed up 3 months. Success was defined in LBBP group as a paced ECG < 120ms or with a 20% length reduction from the basal ECG. Results 120 patients were randomized, 60 in each group, 61% males. The mean age was 77,9 ± 9 years and third-degree AVB was the main pacing indication. The procedure was successful in 95% of the cases in both groups (p = 1). The paced QRS interval was narrower in the LBBP group compared to the RVOT group (99 ± 2 ms vs 113,6 ± 11,7 ms, p < 0,001). Lower fluoroscopy times were achieved in LBBP group (3.1 ± 2.1 min vs 4.3 ± 3.4, p = 0,035) and also longer procedure times in LBBP group (68,9 ± 36,9 min vs 44,3 ± 18,7 min, p < 0,001). No complications were achieved and no difference in ventricular lead dislocation was found between both groups (1.6% vs 1.6%)(p = 1). Conclusions LBBP is feasible, safe and provides a narrower paced QRS compared to RVOTP. LBBP required lower fluoroscopy times but longer procedure times compared to RVOTP. LBBP (n = 60) RVOTP (n = 60) p Age (mean ± SD) 76,7 ± 9 79,7 ± 8 0,067 Male gender 62 (37) 60 (36) 1 Successful procedure 95 (57) 95 (57) 1 Basal left bundle branch block 15 (9) 13 (8) Basal QRS duration (mean ± SD) 112,6 ± 29,6 109,9 ± 25,8 0,59 Pacing QRS duration (min)(mean ± SD) 99 ± 2 139,6 ± 11,7 < 0,001 Procedure time (min) (mean ± SD) 68,9 ± 36,9 44,3 ± 18,7 < 0,001 Fuoroscopy time (min)(mean ± SD) 3.1 ± 2.1 4.3 ± 3.4 0,035 R wave (mV)(mean ± SD) 9,9 ± 5,7 9,9 ± 5 0,98 Right ventricle pacing threshold (V)(mean ± SD) 0,67 ± 0,3 0,58 ± 0,24 0,08 Ventricular lead dislocation 1.6 (1) 1.6 (1) 1

Epicardial adipose tissue modulates arrhythmogenesis in right ventricle outflow tract cardiomyocytes.

Ventricular arrhythmia (VA) frequently occurs in fatty infiltrative cardiomyopathy or epicardial adipose tissue (EAT) abundant hearts. Right ventricular outflow tract (RVOT), commonly covered with EAT, is vital for VA genesis. This study explored whether EAT contributes to RVOT arrhythmogenesis. Conventional microelectrodes and whole-cell patch clamp were used to record electrical activity and ionic currents in rabbit RVOT tissue preparation or isolated single cardiomyocytes with or without (control) connected EAT. Epicardial adipose tissue-connected (N = 6) RVOT had more portions of fibrosis than did control (N = 5) RVOT (160.3 ± 23.2 vs. 91.9 ± 13.4 μm2/mm2, P < 0.05). Epicardial adipose tissue-connected RVOT cardiomyocytes (n = 18) had lower negative resting membrane potential (-68 ± 1 vs. -73 ± 2 mV, P < 0.05); smaller action potential (AP) amplitude (108 ± 4 vs. 135 ± 6 mV, P < 0.005); and longer 90%, 50%, and 20% of AP duration repolarization (361 ± 18 vs. 309 ± 9 ms, P < 0.05; 310 ± 17 vs. 256 ± 13 ms, P < 0.05; and 182 ± 19 vs. 114 ± 24 ms, P < 0.05, respectively) than did control (n = 13) RVOT cardiomyocytes. Moreover, compared with control RVOT cardiomyocytes, EAT-connected RVOT cardiomyocytes had larger transient outward potassium currents, similar delayed rectifier potassium currents, smaller L-type calcium currents, and inward rectifier potassium currents. After ajmaline (10 μM, a sodium channel blocker) superfusion, high VA inducibility was observed through rapid pacing in EAT-connected RVOT but not in control RVOT. Epicardial adipose tissue exerts distinctive electrophysiological effects on RVOT with a propensity towards VA induction, which might play a role in lipotoxicity pathogenesis-related ventricular arrhythmogenesis.

How to Safely Implant a Dual-Chamber Pacemaker for Right Ventricular Outflow Tract Pacing in a Patient with Persistent Left Superior Vena Cava: A Step by Step Guide.

The implementation of advanced endovascular electrophysiological methods in patients with congenital venous anomalies (CVA) remains understudied.1 Patients with CVA have an average life expectancy. At times requiring interventional management of dysrhythmias, CVA can pose a challenge for the placement of implantable pacing devices. Persistent left superior vena cava (PLSVC) is the most common venous congenital anomaly. Herein the author discusses a safe technique of transvenous pacing lead implantation into right ventricular outflow tract (RVOT) and right atrial appendage in a 70-year-old patient with PLSVC.

RVOT Septal Pacing: Short review of History and Technical Requirements for successful implantation

The idea of Right Ventricular Outflow Tract (RVOT) septal pacing is based on the fact that the septal region of the RVOT and mid RV are the first zones of the ventricle to depolarise , suggesting that pacing from these areas on the right side of the septum would achieve as normal a contraction pattern as possible. This mini review describes short history of pacemaker and evolution of concept of physiological pacing like RVOT Pacing and its technical aspects of successful implantation.

Pacing lead is more easily located at RVOT septum in patients with severe tricuspid regurgitation

Objective The optimal right ventricular (RV) pacing site in patients referred for permanent cardiac pacing remains controversial. The present study aims to evaluate at which pacing site the electrode is more easily and steadily located in patients with severe tricuspid regurgitation (TR).Methods and results We prospectively enrolled 50 patients with severe TR for permanent pacemaker implantation and randomly divided them into two groups to receive either RV apex (group A) or RV outflow tract (RVOT) pacing (group B). Time of X-ray exposure for ventricular lead deployment, incidence of intra-procedural dislodgement and post-procedural cTnT level were compared between the two groups. Lead performance and echocardiographic parameters were evaluated during follow-up. Fractional shortening (FS) of both RV body and RVOT were assessed so as to analyse the wall motion of the two RV components. As a result, RV body demonstrated a significantly higher FS than RVOT (36.7 ± 5.0% vs30.0 ± 4.6%, P< 0.01) among all TR cases. Compared with group A, less X-ray time was needed for ventricular lead implantation in group B (114.2 ± 28.9 s vs147.2 ± 55.6 s, P= 0.011) with a lower incidence of intra-procedural dislodgement (4% vs24%, P= 0.042). RVOT pacing was also associated with a lower cTnT level 6 and 24 hours after procedure (P <0.01). Lead performance and echocardiographic parameters during follow-up revealed no difference between RV apex and RVOT pacing.Conclusion In patients with severe TR, the ventricular lead is more easily and steadily located at RVOT septum than at the RV apex with shorter fluoroscopy time, lower incidence of intra-procedural dislodgement and less myocardial injury.

Functional characteristics of left ventricular synchronization via right ventricular outflow-tract pacing detected by two-dimensional strain echocardiography

BackgroundRecently, due to the detrimental effects on the ventricular function associated with right ventricular apical (RVA) pacing, right ventricular septal (RVS) pacing has become the preferred pacing method. However, the term RVS pacing refers to both right ventricular outflow-tract (RVOT) and mid-septal (RVMS) pacing, leading to a misinterpretation of the results of clinical studies. The purpose of this study, therefore, was to elucidate the functional differences of RVA, RVOT, and RVMS pacing in patients with atrioventricular block. MethodsWe compared the QRS duration, global longitudinal strain (GLS), and left ventricular (LV) synchronization parameters at the three pacing sites in 47 patients. The peak systolic strain (PSS) time delay between the earliest and latest segments among the 18 LV segments and standard deviation (SD) of the time to the PSS were also calculated for the 18 LV segments at each pacing site using two-dimensional (2D) strain echocardiography. ResultsRVMS pacing was associated with a significantly shorter QRS duration compared with RVA and RVOT pacing (154.4±21.4 vs 186.5±19.9 and 171.1±21.5ms, P<0.001). In contrast, RVOT pacing revealed a greater GLS (−14.69±4.92 vs −13.12±4.76 and −13.51±4.81%, P<0.001), shorter PSS time delay between the earliest and latest segments (236.0±87.9 vs 271.3±102.9 and 281.9±126.6%, P=0.007), and shorter SD of the time to the PSS (70.8±23.8 vs 82.7±30.8 and 81.5±33.7ms, P=0.002) compared with RVA and RVMS pacing. ConclusionsThese results suggest that the functional characteristics of RVOT pacing may be a more optimal pacing site than RVMS, regardless of the pacing QRS duration, in patients with atrioventricular conduction disorders.

Pacemaker Lead Perforation during Right Ventricular Outflow Tract Pacing -Importance of Heart Rotation at Pacemaker Implantation

A 70 year-old woman underwent a dual-chamber pacemaker implantation for episodes of transient block and syncope. The transitional zone of her ECG was observed between V4 and V5, indicating clockwise rotation. An experienced physician performed the Right Ventricular Outflow Tract (RVOT) pacing using an active fixation lead without any immediate complications. For RVOT pacing, the lead was placed approximately two-thirds of the distance from the apex to the pulmonary valve in the postero-anterior view and pointing towards the septum in the left anterior oblique view. The ECG revealed a narrow QRS (120 msec) and the lead I morphology was minus-plus. Six days post-implant, a pacemaker interrogation revealed ventricular undersensing and loss of capture with high output pacing. Chest computed tomography revealed the left ventricle was displaced to the left and the left-sided angle between the interventricular septum and horizontal axis of the body was reduced to 16°. It confirmed an RV lead perforation through the RVOT, with 1 cm of the lead positioned outside the heart. We performed a surgical repair. Though ECG and x-rays showed septal pacing, we experienced an unusual case of a subacute myocardial perforation caused by an active fixation lead possibly due to heart rotation. The present case report described a patient with a subacute lead perforation and no hemodynamic instability. It is important for the general cardiologist to pay attention to heart rotation. After implantation, symptoms that can suggest a lead perforation, as major signs such as pericardial effusion are not necessarily present. A pacemaker interrogation shows lower impedance, as well as undersensing or failure to capture the involved chamber in suspicious findings.

Inadequacy of fluoroscopy and electrocardiogram in predicting septal position in RVOT pacing – Validation with cardiac computed tomography

BackgroundElectrocardiographic (ECG) and fluoroscopic criteria, which are the only available guides to achieve a true septal position during right ventricular outflow tract (RVOT) pacing, have been infrequently validated. We sought to validate these using cardiac computed tomographic angiography (CTA) to confirm lead position within the RVOT septum. MethodsForty-four patients with permanent pacemaker leads in the RVOT position underwent CTA. Lead positions in RVOT were classified as anterior, free wall, or septal location. Fluoroscopic images were obtained in 4 standard views. ResultsOnly 19 (43%) patients had lead in true septal position within the RVOT in CTA while 25 patients (57%) were found to have an anterior lead location. Mean QRS axis, QRS duration, negative QRS in lead I, and notching in inferior leads were not significantly different between the two groups. The standard fluoroscopic LAO view showed a rightward-directed lead not only in all 19 patients with septal location, but also in 14/25 patients in the anterior location (p=0.22), and thus had a sensitivity of 100% but specificity of only 16% in predicting true septal position. The posteriorly directed lead in left lateral view was more accurate in predicting true septal position with good sensitivity (73.7%) and excellent specificity (80%). ConclusionsThis study, using validation with CTA, showed that conventional ECG criteria and fluoroscopy are inaccurate in differentiating septal from anterior RVOT pacing. The fluoroscopic lateral view, as corroborated by CTA, is more reliable than the LAO view in predicting septal lead placement.

Comparison of left ventricular systolic function and mechanical dyssynchrony using equilibrium radionuclide angiography in patients with right ventricular outflow tract versus right ventricular apical pacing: A prospective single-center study

BackgroundChronic ventricular pacing is known to adversely affect left ventricular (LV) function. Studies comparing right ventricular outflow tract (RVOT) pacing with RV apical (RVA) pacing have shown heterogeneous outcomes. Our aim was to objectively assess LV function and mechanical dyssynchrony in patients with RVOT and RVA pacing using equilibrium radionuclide angiography (ERNA). MethodsFifty-one patients who underwent permanent pacemaker implantation and had normal LV function were prospectively included. Twenty-nine patients had pacemaker lead implanted in the RVOT and 22 at the RVA site. All patients underwent ERNA within 5 days post-pacemaker implantation and follow-up studies at 6 and 12 months. Standard deviation of LV mean phase angle (SD LV mPA) expressed in degrees, which was derived by Fourier first harmonic analysis of phase images, was used to quantify left intraventricular dyssynchrony. ResultsNo significant difference was observed between the two groups with respect to indication (P = .894), Type/mode (P = .985), and percentage of ventricular pacing (P = .352). Paced QRS duration was significantly longer in RVA group than RVOT group (P = .05). There was no statistically significant difference between the RVA and RVOT groups at baseline with respect to LVEF (P = .596) and SD LV mPA (P = .327). Within the RVA group, a significant decline in LVEF was observed over 12-month follow-up (from 57.3% ± 5.32% to 55.6% ± 6.25%; P = .012). In the RVOT group, the change in LVEF was not statistically significant (from 56.7% ± 4.08% to 54.3% ± 6.63%; P = .159). No significant change in SD LV mPA was observed over 12-month follow-up within the RVA group (from 10.5 ± 2.58° to 10.4 ± 3.54°; P = 1.000) as well as in the RVOT group (from 9.7 ± 3.28° to 9.4 ± 2.85°; P = .769). However, between the RVA and RVOT groups, no significant difference was observed at 12-month follow-up in terms of LVEF and dyssynchrony (LVEF P = .488; SD LV mPA P = .296). ConclusionNo significant difference was observed between RVOT and RVA groups with regard to LV function and synchrony over a 12-month follow-up. RVOT pacing offers may lead to better preservation of LV function on longer follow-up.

Acute Effects of Pacing at Different Ventricular Sites on Left Ventricular Rotational Mechanics in a Porcine Model.

The purpose of this study was to examine the acute effects of pacing at different ventricular sites on hemodynamics and left ventricular (LV) rotational mechanics using speckle-tracking echocardiography (STE) in a porcine model. A prospective laboratory investigation. University research laboratory. Yorkshire pigs. In 9 pigs, after midline sternotomy, epicardial pacing was performed from the right ventricular outflow tract (RVOT), right ventricular apex (RVA), and LV free wall. Two-dimensional STE and conductance catheter-derived LV pressure-volume measurements were made to determine the impact of pacing from various sites on LV rotational parameters (twist/untwist) and hemodynamics. RVOT pacing caused the least decrease in end-systolic pressure from baseline (-9.5%), when compared with RVA (-19.1%) and LV (-23.4%). Systolic and diastolic parameters (Emax, Tau) also were different among RVOT (4.7±0.8 mmHg/mL, 32±4 ms), RVA (3.9±0.7 mmHg/mL, 37±6 ms), and LV sites (3.6±0.8 mmHg/mL, 42±7 ms). Similar to the effects of pacing on hemodynamics, RVOT pacing better preserved LV twist (11.1±1.8 v 8.6±1.7, 5.9±0.7 °) and untwisting rate (64.6±8.5 v 56.2±5.3, 48.2±8.5 °/s) when compared with RV apical pacing and LV pacing. Furthermore, prolongation of conduction from LV lateral to anteroseptal at LV base (26.5±3.8 v 13.8±3.3 ms, p<0.05) and LV midpapillary muscle level (35.6±5.6 v 14.1±2.4 ms, p<0.05) was observed with LV pacing compared with RVOT pacing. The present data showed that the LV twist/untwist and cardiac systolic and diastolic function were least affected by RVOT pacing. This finding may be explained by the proximity of this location to the native ventricular conduction system.

Development of mitral and tricuspid regurgitation in right ventricular apex versus right ventricular outflow tract pacing

This study aimed at comparing the development of tricuspid and mitral regurgitation between the right ventricular outflow tract (RVOT) and right ventricular apex (RVA) pacing. We prospectively enrolled 164 patients for permanent pacemaker implantation due to sick sinus syndrome or atrioventricular block and randomly divided them into two equal groups to receive either RVOT or RVA pacing. Patients with heart failure or valvular disease were excluded. The post-procedural echocardiographic evaluations were performed 1year after the pre-procedural echocardiography, and the results were compared with respect to the development of mitral and tricuspid regurgitation and probable changes in the ejection fraction (EF). Age, gender, pacing mode, and baseline cardiac rhythm did not significantly differ between the RVOT and RVA pacing groups. The incidence of mitral regurgitation was significantly higher in the RVA group (p = 0.03), but the incidence of tricuspid regurgitation was similar in both groups. There was a trend toward less tricuspid regurgitation in the RVOT group; however, it was not statistically significant. The mean EF was not significantly different between the study groups. It seems that the incidence of mitral regurgitation in RVA pacing is significantly higher than that in RVOT pacing. The formation of tricuspid regurgitation needs to be discussed in the future. IRCT201103146061N1.

Accuracy of Fluoroscopic and Electrocardiographic Criteria for Pacemaker Lead Implantation by Comparison with Three-Dimensional Echocardiography

Fluoroscopic and electrocardiographic (ECG) criteria for the documentation of pacing lead positioning (apical and alternative sites) have been described, but data regarding their accuracy are lacking. Fifty patients (27 men; mean age, 76 ± 9 years) with permanent right ventricular (RV) pacing leads were included. RV lead position was classified as apical, mid septal, mid RV free wall, RV outflow tract (RVOT) septal, or RVOT free wall. Exact anatomic lead position was documented using three-dimensional (3D) transthoracic echocardiography (TTE). Cohen's κ coefficient was used to assess agreement between fluoroscopic or ECG criteria and 3D TTE. True lead positions were as follows: 15 apical, 24 mid septal, three mid RV free wall, and eight RVOT septal wall; no leads were implanted into the RVOT free wall. Fluoroscopy (κ = 0.56; 95% confidence interval [CI], 0.37-0.76) and electrocardiography (κ = 0.43; 95% CI, 0.25-0.60) had moderate overall agreement with 3D TTE. Fluoroscopy had moderate agreement with 3D TTE for apical (κ = 0.57; 95% CI, 0.32-0.83), mid septal (κ = 0.48; 95% CI, 0.25-0.72), and mid free wall sites (κ = 0.54; 95% CI, 0.08-1.00) and moderate to good agreement for the RVOT septal wall (κ = 0.61; 95% CI, 0.30-0.90). Fluoroscopy misclassified as mid septal six of the 15 RV apical leads. ECG criteria had moderate agreement with 3D TTE for apical positions (κ = 0.55; 95% CI, 0.34-0.77) and RVOT sites (κ = 0.47; 95% CI, 0.21-0.73). Electrocardiography misclassified as apical 10 and as RVOT six of the 24 mid septal leads. Fluoroscopic and ECG criteria are only moderately accurate in discriminating between RV apical, mid septal, mid free wall, and RVOT pacing sites. These data suggest that both fluoroscopy and electrocardiography may not be adequate techniques for the correct documentation of RV pacing lead position for routine clinical practice or research purposes.

Speckle Tracking Imaging in Evaluation of Left Ventricular Mechanics in a Swine Model of Atrioventricular Block during Cardiac Pacing: A Comparison Study with Conventional Right Ventricular Apical Pacing Therapy

The purpose of the study was to evaluate the LV mechanics during various cardiac pacing using 2D speckle tracking echocardiography (STE). In eight open‐chest pigs, cardiac pacing was performed at different sites namely right ventricular (RV) apex, RV outflow tract (RVOT) and left ventricular (LV) lateral as well as biventricular (Bi‐V: RV apex + LV lateral) and triangle (Tri‐V: RV apex + RVOT +LV lateral). Changes in LV synchrony and mechanics (longitudinal shortening and twist) were assessed by STE before and after atrioventricular (A‐V) block induced by chemical ablation. During RV apical and LV lateral pacing, a more dyssynchronous LV contraction was observed together with impairment in LV longitudinal shortening and in LV twist before and after A‐V block as compared to RVOT pacing. RVOT and Tri‐V pacing similarly improved the LV longitudinal shortening and twist and decreased the LV dissynchrony as compared to RV apical and bi‐V pacing after A‐V block. The activation pattern of the LV during RVOT and Tri‐V pacing was more similar to the activation pattern of normal heart than that during RV apical and Bi‐V pacing. LV mechanical dissynchrony, LV strain and LV torsion during different cardiac pacing can be assessed by speckle tracking imaging. Our data suggest that RVOT and Tri‐V pacing may serve as a better cardiac resynchronization therapy.

Right ventricular outflow pacing induces less regional wall motion abnormalities in the left ventricle compared with apical pacing

This study aimed to explore if the right ventricular outflow tract (RVOT) pacing is superior to right ventricular apical (RVA) pacing on the overall left ventricular (LV) function and regional wall motion. Sixty patients with atrio-ventricular (AV) block and normal ejection fraction undergoing dual-chamber pacemaker implantation were randomized to permanent ventricular stimulation either in the RVOT or the RVA. Left ventricular volume, ejection fraction, and LV regional wall motion were assessed by echocardiography. Right ventricular apical pacing had prolonged QRS duration, compared with RVOT pacing (154.1 ± 26.5 vs. 120.9 ± 22.3, P< 0.05). There were also significant differences in LV pre-ejection interval and interventricular mechanical delay (IVMD) at 12-month follow-up between the two groups, but none in the LV volume, left ventricular ejection fraction, and index of systolic synchrony (Ts-SD). During RVA pacing, the average peak systolic velocity (Sm) of 12 LV segments [3.5, 95% confidence interval (CI) 3.2-3.8 cm/s] had a trend of being lower compared with RVOT pacing (3.9, 95% CI 3.5-4.1 cm/s) (P= 0.09). Further analysis showed that the Sm at the inferior wall and posterior-septum wall was significantly decreased during RVA pacing compared with RVOT pacing. There were no significant differences for other LV segments. The RVOT pacing in AV block patients over 1 year may be superior to RVA pacing in terms of regional LV performance, LV global electromechanical delay, and IVMD, although intraventricular dyssynchrony and LV volumes do not differ. Larger trials with clinical endpoints are warranted to conclusively define the advantages of RVOT or RV septal pacing.

Real-time three-dimensional echocardiographic determination of right ventricular outflow tract high septal pacing sites

To investigate the feasibility of determination of right ventricular outflow tract (RVOT) high septal pacing site visualized by real-time three-dimensional echocardiography (RT3DE). The forty subjects with RVOT pacing were analysed. RT3DE determination of RVOT high septal pacing sites was compared with chest X-ray (CXR). RVOT septal pacing sites could be obtained in all patients by RT3DE.When pacing sites were categorized as septal or non-septal, there were good agreements between echocardiography and CXR (kappa = 0.745). However, when RVOT pacing sites were categorized as high septal or non-high septal in identifying the exact anatomic location of pacing sites, there was only mild agreement between echocardiography and CXR (kappa = 0.275). Moreover, when RT3DE was used as the gold standard in identifying the exact anatomic location of RVOT, pacing at the RVOT high septal could only be achieved in 37.5% (n= 15) of patients using RT3DE, but in 65% (n= 26) using CXR, because the RVOT septal pacing lead tip found at high septal by CXR is actually found at low septal or free wall by RT3DE. It is limited to accurately locate RVOT high septal pacing site only by CXR, RT3DE allows to determinate the RVOT high septal pacing sites helpfully.

Upgrading to Biventricular Pacing Guided by Pressure-Volume Loop Analysis During Implantation

cardiac resynchronization therapy (CRT) may improve prognosis in patients with chronic right ventricular (RV) pacing, and optimal lead position can decrease nonresponders. We evaluated the clinical and echocardiographic response to CRT in patients with previous chronic RV pacing, using pressure-volume loop analyses to determine the optimal left ventricular (LV) lead position during implantation. In this single-blinded, randomized, controlled crossover study, 40 patients with chronic RV apical pacing and symptoms of heart failure, decreased LV ejection fraction (LVEF) or dyssynchrony were included. During implantation, stroke work (SW), LVEF, cardiac output, and LV dP/dt(max) were assessed by a conductance catheter. Clinical and echocardiographic response was studied during a 3-month period of RV pacing (RV period, LV lead inactive) and a 3-month period of biventricular pacing (CRT period). At the optimal LV lead position, SW (37 ± 41%), LVEF (16 ± 13%), cardiac output (29 ± 16%), and LV dP/dt(max) increased (11 ± 11%) significantly during biventricular pacing compared to baseline. Additional benefit could be achieved by pressure-volume loop guided selection of the best left-sided pacing location. RV outflow tract pacing did not improve hemodynamics. During follow-up, symptoms improved during CRT, VO(2,max) increased 10% and significant improvements in LVEF, LV volumes, and mitral regurgitation were observed as compared to the RV period. CRT in patients with chronic RV pacing causes significant improvement of both LV function as measured by pressure-volume loops during implantation and clinical and echocardiographic improvement during follow-up. Pressure-volume loops during implantation may facilitate selection of the most optimal pacing site.

Advances in Cardiac Pacing: Beyond the Transvenous Right Ventricular Apical Lead

While for decades right ventricular (RV) apical pacing has been the standard of care for patients requiring pacemaker or defibrillator lead placement, investigators have sought alternatives to achieve more physiologic electrical activation of the heart and reduce long-term pathologic effects of nonphysiologic apical pacing. These investigations have included attempts at identifying superior pacing sites within the right atrium and RV and development of new leads to enhance specificity of sensing and capture. This review focuses on recent advances in alternative sites for pacing and developments in novel pacing technology ranging from intramyocardial electrodes to leadless pacemakers. First, there have been several studies demonstrating potential benefits of site-specific pacing, including His bundle pacing and RV outflow tract pacing in potentially attenuating electromechanical dyssynchrony and long-term functional decline seen with RV apical pacing. Available options for lead placement have been enhanced by development of intramyocardial electrodes that may significantly reduce far-field oversensing and nonchamber specific capture. With development of intramyocardial electrodes, the potential for atrioventricular septal pacing has recently been described, making synchronous activation of both ventricles with a one-lead system possible without crossing the tricuspid valve and offering an alternative to modern cardiac resynchronization therapy (CRT). Finally, recent advances in leadless pacemaker systems using ultrasound or magnetic fields are briefly discussed. The results of these studies suggest that there may be options to the RV apex, made possible by novel lead and pacemaker technology. These advances can potentially aid in reducing long-term negative effects of chronic pacemaker therapy.

Comparison of the Acute Hemodynamic Effect of Right Ventricular Apex, Outflow Tract, and Dual-Site Right Ventricular Pacing

We studied the acute effect of pacing at the right ventricular outflow tract (RVOT), right ventricular apex (RVA) and simultaneous RVA and RVOT-dual-site right ventricular pacing (DuRV) in random order on systolic function using impedance cardiography. Seventy-three patients (46 males), aged 52-89 years (mean 71.4 years) subjected to routine dual chamber pacemaker implantation with symptomatic chronic II or atrioventricular block, were included to the study. DuRV pacing resulted in significantly higher cardiac index (CI) in comparison to RVOT and RVA and CI at RVOT was higher than at RVA pacing (2.46 vs 2.35 vs 2.28; P < 0.001). In patients with ejection fraction >50% significantly higher CI was observed during DuRV pacing when compared to RVOT and RVA pacing and there was no difference of CI between RVOT and RVA pacing (2.53 vs 2.41 vs 2.37; P < 0.001). In patients with ejection fraction <50%, DuRV and RVOT pacing resulted in significantly higher CI in comparison to RVA pacing while no difference in CI was observed between RVOT and DuRV pacing (2.28 vs 2.21 vs 2.09; P < 0.001). Dual-site right ventricular pacing in comparison to RVA pacing improved cardiac systolic function. RVOT appeared to be more advantageous than RVA pacing in patients with impaired, but not in those with preserved left ventricular function. No clear hemodynamic benefit of DuRV in comparison to RVOT pacing in patients with impaired systolic function was observed.

Advantage of Right Ventricular Outflow Tract Pacing on Cardiac Function and Coronary Circulation in Comparison with Right Ventricular Apex Pacing

The purpose of this study was to investigate the acute effect of right ventricular outflow tract (RVOT) pacing and right ventricular apex (RVA) pacing on synchronous ventricular activation and coronary flow dynamics. We enrolled 20 consecutive patients who underwent electrophysiologic study. Echocardiographic study including two-dimensional tissue tracking imaging and Doppler guide wire examination was performed during RVOT pacing and RVA pacing. The improvement of left ventricular radial dyssynchrony (99 ± 12 ms vs. 142 ± 16 ms, P < .001), time-averaged peak velocities of coronary blood flow (54 ± 18 cm/s vs. 47 ± 17 cm/s, P = .007), and coronary microvascular resistance index (2.0 ± 0.8 vs. 2.4 ± 1.1, P = .028) was observed with RVOT pacing compared with RVA pacing. RVOT pacing might provide favorable effects on the left ventricular function and coronary flow dynamics over RVA pacing.