Right Ventricular Outflow Tract Pacing Research Articles

Bifocal Right Ventricular Resynchronization for the Failing Right Ventricle

The present case illustrates that in patients with right ventricular (RV) failure and right bundle branch block it is possible to resynchronize the RV without further worsening RV or left ventricular (LV) pump function, even in cases with various degrees of atrioventricular block. The acute response to different pacing configurations was analyzed in terms of dP/dt variations. Bifocal RV pacing (His bundle plus RV outflow tract pacing) achieved the best acute results and was chosen for permanent pacing. This pacing configuration was associated to clinical and echocardiographic improvement.

Long‐Term Mechanical Consequences of Permanent Right Ventricular Pacing: Effect of Pacing Site

Long-term right ventricular apical (RVA) pacing has been associated with adverse effects on left ventricular systolic function; however, the comparative effects of right ventricular outflow tract (RVOT) pacing are unknown. Our aim was therefore to examine the long-term effects of septal RVOT versus RVA pacing on left ventricular and atrial structure and function. Fifty-eight patients who were prospectively randomized to long-term pacing either from the right ventricular apex or RVOT septum were studied echocardiographically. Left ventricular (LV) and atrial (LA) volumes were measured. LV 2D strain and tissue velocity images were analyzed to measure 18-segment time-to-peak longitudinal systolic strain and 12-segment time-to-peak systolic tissue velocity. Intra-LV synchrony was assessed by their respective standard deviations. Interventricular mechanical delay was measured as the difference in time-to-onset of systolic flow in the RVOT and LV outflow tract. Septal A' was measured using tissue velocity images. Following 29 ± 10 months pacing, there was a significant difference in LV ejection fraction (P < 0.001), LV end-systolic volume (P = 0.007), and LA volume (P = 0.02) favoring the RVOT-paced group over the RVA-paced patients. RVA-pacing was associated with greater interventricular mechanical dyssynchrony and intra-LV dyssynchrony than RVOT-pacing. Septal A' was adversely affected by intra-LV dyssynchrony (P < 0.05). Long-term RVOT-pacing was associated with superior indices of LV structure and function compared with RVA-pacing, and was associated with less adverse LA remodeling. If pacing cannot be avoided, the RVOT septum may be the preferred site for right ventricular pacing.

Right Ventricular Outflow Tract Pacing Causes Intraventricular Dyssynchrony in Patients With Sick Sinus Syndrome: A Real-Time Three-Dimensional Echocardiographic Study

The optimal right ventricular pacing site remains controversial. The aim of this study was to assess how acute right ventricular outflow tract (RVOT) pacing affects global left ventricular function and intraventricular dyssynchrony of the left ventricle. Thirty-six patients with sick sinus syndrome and intact intrinsic atrioventricular conduction were enrolled. All patients underwent dual-chamber permanent pacemaker implantation, with the atrial lead placed in the right atrial appendage and the right ventricle lead positioned at the septal site of the RVOT. Chamber size, dyssynchrony index, myocardial performance index, and global left ventricular ejection fraction were determined using transthoracic two-dimensional echocardiography, tissue Doppler echocardiography, and real-time three-dimensional echocardiography. RVOT pacing increased the myocardial performance index (0.42 +/- 0.21 with RVOT pacing vs 0.35 +/- 0.21 without RVOT pacing, P = .002) and decreased the global left ventricular ejection fraction on real-time 3-dimensional echocardiography (51.4 +/- 6.2% with RVOT pacing vs 55.9 +/- 7.1% without RVOT pacing, P = .001). Intraventricular dyssynchrony of the left ventricle induced by RVOT pacing was determined by increased septal-to-posterior wall motion delay (69.7 +/- 54.0 ms with RVOT pacing vs 22.8 +/- 22.3 ms without RVOT pacing, P < .0001), increased systolic and diastolic dyssynchrony by tissue Doppler echocardiography, and increased systolic dyssynchrony index when assessed using real-time three-dimensional echocardiography (5.56 +/- 1.74% with RVOT pacing vs 4.05 +/- 1.61% without RVOT pacing, P < .0001). Acute RVOT pacing adversely affects left ventricular function and increases intraventricular dyssynchrony in patients with sick sinus syndrome.

Is Right Ventricular Outflow Tract Pacing Superior to Right Ventricular Apex Pacing in Patients with Normal Cardiac Function?

Whether right ventricular outflow tract (RVOT) pacing is superior to right ventricular apex (RVA) pacing in terms of ventricular synchrony, cardiac function, and remodeling in patients with normal cardiac function is still unknown. Right ventricular outflow tract pacing is superior to RVA pacing in patients with normal cardiac function. A total of 96 consecutive patients with high or third-degree atrial ventricular block were enrolled and randomized into 2 groups: RVOT pacing group (n = 48) and RVA pacing group (n = 48). Tissue Doppler imaging (TDI) and 2D echocardiography were performed to study left ventricular (LV) systolic and diastolic synchrony, LV volumes, and function. There were no significant differences in baseline characteristics between the 2 groups. Left ventricular systolic asynchrony is more severe in the RVA pacing group than in the RVOT pacing group (P < 0.05), while diastolic synchrony is not significantly (NS) different between the 2 groups after pacing. There were no significant differences with respect to the mean myocardial systolic (Sm) and early diastolic velocities (Em), LV ejection fraction, LV end-diastolic and systolic volume in the 2 groups at 12 months of follow-up (all NS). Although RVOT pacing caused more synchronous LV contraction compared with RVA pacing, it had no benefit over RVA pacing in aspect of preventing cardiac remodeling and preserving LV systolic function after 12 months of pacing in patients with normal cardiac function.

Global electrophysiological and hemodynamic assessment of ventricular pacing employing non-contact mapping

Right ventricular (RV) pacing has been associated with abnormal cardiac electrical and mechanical dyssynchrony, resulting in impaired global and regional ventricular pump function. This study aimed to characterize the relative effects of pacing site on left ventricular (LV) activation patterns and associated hemodynamic performances. Acute pacing was performed in anesthetized swine (n=10) instrumented for RV and LV pressure, noncontact mapping (NCM) of endocardial unipolar electrograms, surface ECG, aortic flow, and sonomicrometry. Bipolar endocardial pacing leads were positioned in the right atrial appendage (RAA), RV apex (RVA), and RV outflow tract (RVOT), while bipolar epicardial leads were positioned on the LV-free wall (LVFW) and LV apex (LVA). LVFW and RVA pacing induced the largest increase in intraventricular electrical dyssynchrony (IVED; 32.2+/-10 ms, 21.7+/-4.1 ms, respectively; both p<0.01), whereas pacing from all sites increased QRS and total endocardial LV activation durations (p<0.01). The largest impairment of LV and RV contractility (dP/dtmax) and relaxation (dP/dtmin) was observed during RVA pacing (p= ns). Synchronous electrical activation patterns were observed on NCM during RVOT and LVA pacing. LVFW pacing was the only site that significantly increased tau values as compared to RAA pacing (approximately 25%), whereas LVA pacing elicited only slight increases (approximately 1%). In swine with preserved ventricular conduction, in vivo pacing of the RVOT and LVA was associated with preserved, physiologically similar electrical activation sequences and LV function relative to RAA pacing. In contrast, RVA pacing caused widespread electrical dyssynchrony of the LV and prolonged activation durations, thereby impairing associated cardiac performance. Such insights into alternate site cardiac pacing, which employed the combination of high-resolution electrical mapping with real-time hemodynamic assessments, may further increase acute and long-term benefits in patients requiring permanent pacemaker support.

Acute Changes in Cardiac Synchrony and Output According to RV Pacing Sites in Koreans with Normal Cardiac Function

The synchrony of the pacing heart can be affected by the right ventricular (RV) pacing site and is crucial to cardiac function in pacemaker recipients. We evaluated the acute changes in cardiac synchrony according to the RV pacing sites in normal systolic functioning subjects with normal QRS. We conducted this study with 30 patients with the pacing in the RV apex (RVA), RV septum (RVS), and RV outflow tract (RVOT) in a sequential manner. Transthoracic echocardiography was conducted at rest and during pacing in order to measure interventricular and intraventricular dyssynchrony in all patients. QRS duration (148.1 +/- 12.8 ms) of RVA pacing was significantly shorter than that of RVS pacing (154.4 +/- 14.1 ms, P < 0.01) and RVOT pacing (160.6 +/- 15.7 ms, P < 0.001). We noted no statistically significant difference in cardiac output according to the pacing sites. The interventricular dyssynchrony with M-mode and Doppler echocardiography in RVOT pacing was increased to an insignificant degree as compared with those with RVS pacing or RVA pacing. The intraventricular dyssynchrony with tissue Doppler echocardiography in RVA pacing was reduced significantly as compared with that of RVS pacing or RVOT (RVA = 60.3 +/- 32.7 ms, RVS = 82.1 +/- 33.8 ms, RVOT = 79.1 +/- 33.3 ms; RVA vs RVS = P < 0.05, RVA vs RVOT = P < 0.01, RVS vs RVOT = P = NS). RVA pacing is superior to RVS and RVOT pacing with regard to intraventricular synchrony in normal systolic functioning subjects with normal QRS. Cardiac output at RVA pacing is not inferior to other sites.

Temporary Epicardial Ventricular Stimulation in Patients with Atrial Fibrillation: Acute Effects of Ventricular Pacing Site on Bypass Graft Flows

Data on coronary artery bypass grafts flows in patients with atrial fibrillation (AF) requiring epicardial ventricular pacing is lacking. This study aimed to evaluate the optimal epicardial ventricular pacing site in patients with AF following coronary artery bypass surgery (CABG). In 23 consecutive patients (mean age = 69.2 +/- 1.9 years, gender = 62% male, ejection fraction [EF]= 50.4 +/- 2.1%) monoventricular stimulations (VVI) were tested with a constant pacing rate of 100 bpm. The impact of ventricular pacing on bypass graft flow (transit-time flow probe) and pulsatility index (PI) were measured after lead placement on the mid paraseptal region of the right (RVPS) and the left (LVPS) ventricle, on the right inferior wall (RVIW), and on the right ventricular outflow tract (RVOT). In addition, hemodynamic parameters were measured. Patients served as their own control. Comparison of all tested pacing locations revealed that RVOT stimulation provided the highest bypass grafts flows (59.9 +/- 6.1 mL/min) and PI (2.2 +/- 0.1) when compared with RVPS (51.3 +/- 4.7 mL/min, PI = 2.6 +/- 0.2), RVIW (54.0 +/- 5.1 mL/m; PI = 2.4 +/- 0.2), and LVPS (53.1 +/- 4.5 mL/min; PI = 2.3 +/- 0.1), respectively (p < 0.05). When analyzing patients according to their preoperative LV function (group I = EF > 50%; group II = EF < 50%), higher bypass graft flows were observed with RVOT pacing in patients with lower EF (p = n.s.). Temporary RVOT pacing facilitates optimal bypass graft flows when compared with other ventricular pacing sites and should be the preferred method of temporary pacing in cardiac surgery patients with AF. Especially in patients with low EF following CABG, RVOT pacing may improve myocardial oxygen conditions for the ischemic myocardium and enhance graft patency in the early postoperative period.

Insights into the Effects of Contraction Dyssynchrony on Global Left Ventricular Mechano‐Energetic Function

The effects of dyssynchrony on global left ventricular (LV) mechanics have been well documented; however, its impact on LV energetics has received less attention. To assess the effects of LV contraction dyssynchrony on global LV mechano-energetic function in a pacing-induced acute model of dyssynchrony. Using blood-perfused isolated rabbit heart preparations (n = 11), LV pressure, coronary flow, and arteriovenous oxygen content difference were recorded for isovolumic contractions under right atrial (RA) pacing (control) and simultaneous RA and right ventricular outflow tract (RVOT) pacing (dyssynchrony). LV mechanical function was quantified by the end-systolic pressure-volume relationship (ESPVR). Myocardial oxygen consumption-pressure-volume area (MVO(2)-PVA) relationship quantified LV energetic function. Internal PVA for MVO(2 RVOT) was calculated based on the MVO(2)-PVA relationship for RA pacing. Thus, lost PVA (internal PVA-PVA(RVOT)) represents the mechanical energy not observable at the global level. Compared to RA pacing, RVOT pacing depressed LV mechanics as indicated by a rightward shift of ESPVR (i.e., increase in V(d) from 0.58 +/- 0.10 to 0.67 +/- 0.10 mL, P < 0.05). Despite depressed mechanics, RVOT pacing was associated with greater MVO(2) such that the MVO(2)-PVA relationship intercept was markedly increased from 0.025 +/- 0.003 to 0.029 +/- 0.003 mL*O(2)/beat/100gLV (P < 0.05). Excess MVO(2) (i.e., MVO(2 RVOT)- MVO(2 RA)) significantly correlated with lost PVA (R(2)= 0.54, P < 0.001). A potential mechanism explaining the observed increase in MVO(2) with dyssynchrony may be that the measured PVA at the global level underestimates the internal PVA at the cellular level, which is likely to be the true determinant of MVO(2).

A Prospective Randomized Trial of Defibrillation Thresholds from the Right Ventricular Outflow Tract and the Right Ventricular Apex

Right ventricular outflow tract (RVOT) pacing has been suggested to improve hemodynamics and to help prevent pacing-induced cardiomyopathy. Pacing from the RVOT is feasible and equivalent in terms of sensing and stimulation threshold. However, physicians have been reluctant to use RVOT pacing because of concerns that defibrillation efficacy might be adversely affected. To date, there have been no randomized-controlled trials published comparing the defibrillation threshold in leads implanted in the RVOT and the right ventricular apex (RVA). The purpose of this study was to compare defibrillation thresholds (DFT) in the RVOT and RVA. Ventricular sensing and stimulation thresholds were also compared. This prospective, randomized, multicenter study included 87 patients (70 males, age 69 +/- 11 years). At implantation, the patient's ventricular implantable cardioverter-defibrillator (ICD) lead position was randomized to either the RVOT or RVA. A four-shock Bayesian up-down method was used to determine the DFT. Patients were followed for 3 months postimplant. DFTs were not significantly different in leads implanted in the RVOT (median 8.8 J [6.28, 12.9] vs. 7.9 J [6.20, 12.6], P = 0.65). Threshold and impedance measurements were stable in both RVOT and RVA groups from implant to follow-up. All ICD leads remained stable chronically at the 3-month follow-up. DFTs in leads placed in the RVOT and RVA are comparable. RVOT ICD lead placement is safe and exhibits similar lead stability, threshold, and impedance measurements as the traditional RVA location.

Pressure-volume loop analysis during implantation of biventricular pacemaker/cardiac resynchronization therapy device to optimize right and left ventricular pacing sites

To evaluate the clinical utility of pressure-volume loop analyses during pacemaker/implantable cardioverter defibrillator (ICD) implantations to assess the optimal right ventricular (RV) and/or left ventricular (LV) lead position. 29 patients with heart failure and chronic RV apical pacing were studied. Stroke work (SW), LV ejection fraction (LVEF), cardiac output (CO), and LV dP/dt(max) were assessed using a conductance catheter in the LV during RV apical, RV outflow tract, single-site LV, and biventricular pacing at different left-sided pacing locations. Left ventricular ejection fraction was 34.3 +/- 9.8%. Compared with baseline, RV outflow tract pacing showed a small increase of 4.0 +/- 6.4% in LV dP/dt(max) and no improvement in SW, LVEF, or CO. In the optimal biventricular configuration, SW increased 39 +/- 41%, LVEF increased 22 +/- 13%, CO increased 16 +/- 16%, and LV dP/dt(max) increased 10 +/- 11% (all P < 0.05). In 45% of the patients, the optimal LV lead position was found at a different location as the 'first choice' postero-lateral or lateral target vein. Pressure-volume loop analysis during pacemaker/ICD implantations facilitates to determine the optimal LV pacing site. Patients with chronic RV pacing showed a significant acute improvement in LV function when LV pacing or biventricular pacing is applied.

Right ventricular outflow and apical pacing comparably worsen the echocardioghraphic normal left ventricle

A depressed left ventricular function (LVF) is sometimes observed during right ventricular apical (RVA) pacing, but any prediction of this adverse effect cannot be done. Right ventricular outflow tract (RVOT) pacing is thought to deteriorate LVF less frequently because of a more normal LV activation pattern. This study aims to assess the acute effects of RVA and RVOT pacing on LVF in order to determine the contribution of echocardiography for the selection of the optimum pacing site during pacemaker (PM) implantation. Fourteen patients with a DDD-pacemaker (7 RVA, 7 RVOT) and normal LVF without other cardiac abnormalities were studied. PM dependency, because of sick sinus syndrome with normal atrioventricular and intraventricular conduction, was absent in all, allowing acute programming changes. Wall motion score (WMS), longitudinal LV strain, and tissue Doppler imaging for electromechanical delay were assessed with echocardiography during AAI pacing constituting baseline and DDD pacing. The WMS was normal at baseline (AAI pacing) in all patients and LV dyssynchrony was absent. Acute RVA and RVOT pacing deteriorated WMS, electromechanical delay, and longitudinal LV strain, but no difference of the deterioration between both pacing sites was present and dyssynchrony did not emerge. Both acute RVA and RVOT pacing negatively affect WMS, longitudinal LV strain, and mechanical activation times, without clear differences between both pacing sites. Thus echocardiographic techniques do not facilitate the selection between RVOT and RVA pacing to exclude adverse effects on LVF during PM implantation in patients with a normal LVF.

Similar Degree in Mechanical Left Ventricular Dyssynchrony Between Right Ventricular Outflow Tract and Right Ventricular Apical Pacing: A Strain Doppler Imaging Study

Background and Objectives: Long-term right ventricular (RV) apex pacing has been associated with left ventricular (LV) systolic dysfunction. However, pacing in the RV outflow tract (RVOT) is associated with a narrower QRS duration and may have a more normal LV activation in comparison to RV apical (RVA) pacing. We hypothesized that RVOT pacing is associated with less mechanical dyssynchrony compared to RVA pacing and that it also more closely resembles mechanical activation in normal controls with a narrow QRS. Subjects and Methods: We studied 9 patients with RV pacing, 9 with left bundle branch block (LBBB), and 15 normal controls with a narrow QRS. In the RV pacing group, we paced from the RVA and RVOT. At the end of each pacing train, we obtained echocardiographic images in the apical 4- and 2-chamber views and obtained the following parameters: the compression/expansion crossover point (CEP) for myocardial strain and the time from QRS onset to the CEP in the strain image. The degree of dyssynchrony was evaluated using the dispersion and standard deviation of CEP times in 12 segments of the LV. Results: Significant dyssynchrony was observed in the RVOT pacing group compared to the group with normal QRS. No significant difference was observed in LV mechanical dyssynchrony among the RVOT pacing, RVA pacing, and LBBB groups. Conclusion: RVOT pacing is associated with significant LV dyssynchrony. Although the RVOT has been recommended as an alternative site for pacing, this approach may have adverse effects on long-term LV function. (Korean Circ J 2008;38:590-595)

The Right Ventricular Outflow Tract: The Road to Septal Pacing

Pacing from the right ventricular apex is associated with long-term adverse effects on left ventricular function. This has fuelled interest in alternative pacing sites, especially the septal aspect of the right ventricular outflow tract (RVOT). However, it is a common perception that septal RVOT pacing is difficult to achieve. In this article, we will review the anatomy of the RVOT and discuss the importance of standard radiographic views and the 12-lead electrocardiogram in aiding lead placement. We will also describe a method utilizing a novel stylet shape, whereby a conventional active-fixation, stylet-driven lead can be easily and reliably deployed onto the RVOT septum.

Ventricle Dyssynchrony in Right Ventricle Apex and Right Ventricle Outflow Tract Pacing: Evaluation by Tissue Doppler Imaging

Background : Pacemaker lead implantation at right ventricular apex (RVA) or right ventricular outflow tract (RVOT) have different haemodynamic consecuences, due to ventricular dyssynchrony difference. Tissue Doppler Imaging (TDI) clearly shown ventricle dyssynchrony, this modality is better than convensional echo. This research was performed using TDI to describe ventricle dyssynchrony in RVA and RVOT pacing. Method and Result: Twenty four patients with VVI/VVIR pacemaker inserted at the Catheterization Laboratory National Cardiac Centre Harapan Kita Hospital were evaluated using TDI modality for ventricle dyssynchrony. Subject characteristic consist of 13 men (54,8%) and 11 (45,8%) women, with average of age were 61,38 ± 12,41 years. Base rhythm were Sick Sinus Syndrome/SSS (37,5%) and Total Atrioventricular Block/TAVB (62,5%). The duration of implantation was 24,83 ± 16,88 months, with minimal duration of pacing 1 month and maximal duration 63 months. The average of ventricular ejection fraction was 0,45±0,15. Chi Square analyze have shown that there were no difference dyssynchrony between RVA and RVOT pacing, p=0,408 for inter ventricular delay and p=0,423. for intra ventricular delay. QRS duration after pacing have shown significant difference between the two groups (p=0.01). Conclusion : There were no difference in ventricular dyssynchrony between RVA and RVOT pacing, but QRS duration at the RVOT pacing is significantly shorter than RVA pacing.

Identification of the Right Ventricular Pacing Site for Cardiac Resynchronization Therapy (CRT) Guided by Electroanatomical Mapping (CARTO)

The optimal left ventricle (LV) pacing site for cardiac resynchronization therapy (CRT) has been investigated, but less is known about the optimal site in the right ventricle (RV). The present study examined whether electrical resynchronization guided by electroanatomical mapping (CARTO) results in mechanical resynchronization. The study group included 13 patients indicated for CRT: 10 with nonischemic cardiomyopathy, 2 with ischemic cardiomyopathy and 1 with cardiac sarcoidosis, (mean LV ejection fraction: 32+/-10%). CARTO of the RV septum was performed to identify the site with the most delayed conduction time during LV pacing. Hemodynamic measurements were performed during conventional biventricular pacing with the RV apex and LV (C-BVP) and during biventricular pacing with the most delayed site of the RV (d-RV) and LV (D-BVP). Lead placement at 15 coronary sinus veins was examined in the 13 patients. During pacing from anterolateral veins (n=2), the d-RV was the RV apex (RVA) in 1 patient and the mid-septum in the other. During pacing from lateral veins (n=9), the d-RV comprised the RVA (n=3), the mid-septum (n=5), and the right ventricular outflow tract (RVOT) (n=1). During pacing from the posterolateral veins (n=3), the d-RV was the RVOT in all cases. In 11 of 15 sites, d-RV differed from conventional RVA. Compared with C-BVP, D-BVP produced a significant improvement in LV dp/dt. Furthermore, RV mid-septum and LV pacing markedly increased LV dp/dt and pulse pressure (PP), but RVOT and LV pacing did not. D-BVP vs C-BVP: %LV dp/dt 30+/-20 and 15+/-15%, p<0.05; RV mid-septum and LV pacing vs C-BVP: %LV dp/dt 35+/-20 and 10+/-15%, p<0.02, and vs PP 33+/-20 and 10+/-29 mmHg, p<0.02. For pacing from the LV lateral vein, potential improvement of cardiac performance compared with that by conventional RVA placement may be realized with concomitant pacing from the d-RV (mid-septum).

Upgrading Pacing Generators in the Era of Biventricular Pacing

Since the inception of transvenous pacing, the right ventricular apex (RVA) has been the conventional pacing site. However, it is becoming increasingly evident that this may be deleterious in some patients, particularly those with prior clinical heart failure or evidence of impaired left ventricular function. RVA pacing causes asynchronous patterns of right and left ventricular depolarization and contraction.1–3 This produces abnormal regional myocardial blood flow, changes in cardiac metabolism, and impairs systolic and diastolic function.4,5 Experimental studies have indicated that long-term RVA pacing induces abnormal histologic change with myofibrillary disarray and asymmetrical left ventricular hypertrophy and thinning.6,7 There is mounting clinical evidence that chronic RVA pacing increases the risk of developing heart failure and atrial arrhythmias.8–11 In the DAVID trial, patients in whom RVA pacing predominated (the dual chamber group) were at greater risk of reaching the composite end-point of death and hospitalization for heart failure compared to those with less RVA pacing.8 These patients had significant left ventricular impairment prior to device implant. The situation is less clear where LV function is preserved prior to pacing but even the large-scale pacing studies have shown only a modest benefit as far as dual chamber pacing (compared to RVA pacing) is concerned. As yet, the ideal pacing site remains to be determined. Small-scale studies of right ventricular outflow tract (RVOT) pacing have shown amelioration of the reduction of LV function and prevention of myofibrillary disarray,12 but clinically RVOT pacing has produced inconsistent results. Only atrial (AAI) pacing has shown a consistent survival benefit with less heart failure and atrial fibrillation, reinforcing that ventricular depolarization via the His-Purkinje system is preferable.13 However, it does appear that chronic RVA pacing produces dysynchrony of left ventricular con-

Acute Effects of Dual-chamber Pacing on the Left Ventricular Systolic Function and Relaxation in Patients with Advanced AV Block and Sick Sinus Syndrome

Abnormal activation of the ventricles via right ventricular apical pacing deteriorates cardiac function, which may explain the increased mortality of patients with congestive heart failure receiving permanent pacemakers. We hypothesized that pacing at alternative sites may cause less detrimental effects on the cardiac function. Five symptomatic patients with either advanced AV block (n = 4) or sick sinus syndrome with normal left ventricular (LV) function (n = 1) were studied. During cardiac catheterization, LV pressure was recorded with a high-fidelity catheter-tipped transducer. Baseline rhythms were sinus rhythm or VVI pacing. Sequential VDD pacing with variable AV intervals was performed at the right ventricular apex (RVA), right ventricular septum (RVS), right ventricular outflow tract (RVOT) and coronary sinus (CS). LV systolic function was assessed by calculating dP/dt(max) and LV diastolic function was indexed by calculating the exponential isovolumic relaxation constant (Tau). Percentage changes (mean +/- SE) from baseline to pacing were measured. RVA pacing reduced dP/dt(max) (-0.8 +/- 8.4%) and prolonged Tau (7.0 +/- 5.6%); RVS pacing enhanced dP/dt(max) (20.7 +/- 15.3%) and shortened Tau (-10.4 +/- 9%); RVOT pacing reduced dP/dt(max) (-8.0 +/- 20.0%) and shortened Tau (-6.0 +/- 12.2%); CS pacing reduced dP/dt(max) (-11.7 +/- 13.0%) and prolonged Tau (10.5 +/- 11.9%). Our results demonstrated that different pacing sites have different effects on LV contractility and relaxation in patients with normal LV function. Since pacing at the RVS preferably increased LV dP/dt(max) and shortened Tau, it may be a better alternative than the RVA.

510 Similar degree of mechanical left ventricular dyssynchrony between RV outflow tract and apex pacing for permanent pacemaker site: studied by strain Doppler image

Purpose: The long term right ventricular (RV) apex pacing has been associated with left ventricular (LV) systolic dysfunction. These may be the result of abnormal myocardial shearing forces and stress vectors. However, in RV outflow tract (RVOT) pacing ventricular activation may not be changed from that occurring over the normal His-Purkinje network to that originating from site of the ventricular lead. So we hypothesized that the degree of mechanical LV dyssynchrony in RVOT pacing is less than that in RV apex pacing. Methods: We enrolled 15 controls, 9 patients with RV pacing and 9 patients with LBBB. In RV pacing group, we paced at 2 sites (RV apex and RVOT) with 500 msec for 3 minutes. At the end of each pacing, we had the echocardiographic images in the apical 4 and 2 chamber views. We measured the time from QRS onset to compression/expansion crossover point in the strain image. The degree of dyssynchrony was evaluated by the difference between the longest and shortest parameters. We compared mechanical dyssynchrony in 12 segment of LV among different groups. Results: The degree of mechanical dyssynchrony was similar in RV apical, RVOT pacing and LBBB groups (figure 1). Detailed data are in the table. Conclusion: The RVOT pacing, though it may be recommended as an alternative site, might have an adverse effect on long term LV function.

Factors influencing differences of rva ; rvot pacing hemodynamic effects

It was proved that right ventricular apex pacing (RVAp) deteriorates synchrony of ventricular contraction and decreases cardiac performance. Right ventricular outflow tract pacing (RVOTp) is more favorable pacing option due to better sequence of ventricular activation. The aim of the study was to compare acute hemodynamic effects of RVAp and RVOTp and to find the predictors of differences between those two modes. Methods In 51 patients, during implantation of pacing system, cardiac performance was evaluated at RVA and RVOT pacing modes by means of impedance cardiography (BioZ.com;Cardiodynamics). Indices of contractility: Acceleration Index (ACI), Velocity Index (VI) and Cardiac Index (CI) were determined as well as the LV ejection time (LVET) and pre-ejection period (PEP). The measurements in 3 min periods were collected and averaged, after the adaptation period of 5 min. Results In 65% of pts RVOTp showed to be more favourable than RVAp. The differences of CI after replacement of RVA to RVOTp were dependent on cardiac contractility during RVA pacing (CI: r=−0,48 p<0,001; PEP: r=0,27 p=0,052, LVET: r=−0,34 p=0,02; VI: r=−0,29 p=0,04) and echocardiographic parameters as LVEF (r=−0,36 p=0,02) and LVPWd (r=0,40 p=0,01). The differences did not correlated with RVA paced QRS duration and with change of axis deviation after RVAp to RVOTp change. Multivariate analysis showed that only CI during RVAp was the independent factor influencing RVAp-RVOTp differences of CI. Conclusions RVOT pacing provides significantly higher cardiac performance than standard RVA pacing. The acute positive effect of RVOT vs RVA pacing is more visible in insufficient hearts. RVOTp should be considered as an alternative for patients with impaired cardiac per performance (without current CRT indications).

Commentary on the abstracts for Cardiostim 2005 Pacing and Haemodynamics: Art of Timing Budapest, Hungary, April 6–8, 2005

The Cardiostim team and Prof. Aladar Ronaszeki organised an educational meeting in Budapest from April 6 to 8 entitled “Pacing and Haemodynamics: Art of Timing”. This European congress has been an opportunity to discuss the haemodynamic effects of the various modes of pacing available, and more specifically Cardiac Resynchronisation Therapy (CRT) for heart failure patients. The reader will find below the 101 abstracts selected among the 156 received, printed in three different sections: conventional pacing, CRT, and a small set of abstracts on ablation techniques, which will not receive comment. Many investigations have demonstrated the deleterious effects of right ventricular (RV) apical pacing. Padeletti et al. (for the WHERE study) elegantly show the benefit of preserving spontaneous AV conduction in comparison with RV apical pacing, in DDD paced patients, via PEA measurements. PEA, which has been demonstrated to be closely correlated with LV d P /d t , significantly increases when patients are not RV paced, and decreases when they are RV paced. PEA variations parallel clinical outcomes and echo parameter values. When pacing is necessary, there is still controversy about the optimal RV pacing site. Direct His bundle pacing is feasible and safe (Catanzariti et al.), but requires normal function of the bundle branches and Purkinje system. Implantation is also difficult to perform. Long term reliability of His pacing is unknown. For Kutarski et al., RV outflow tract (RVOT) pacing is preferable to RV apical pacing. But for van Gelder, RV apical pacing is preferred for CRT patients. In our experience, RVOT and RV apical pacing provide similar haemodynamic results on average, but may induce significant individual differences. To help to understand individual requirements, one of the main targets for manufacturers is to propose haemodynamic sensors that could evaluate and guide the benefits of various pacing sites, such as …