Outflow Tract Pacing Research Articles

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 …

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).

A30-4 Right ventricle outflow tract and dual site right ventricular pacing &amp; an alternative for conventional right ventricular apex pacing?

A30-4 Right ventricle outflow tract and dual site right ventricular pacing &amp; an alternative for conventional right ventricular apex pacing?

A30-4 Right ventricle outflow tract and dual site right ventricular pacing &amp; an alternative for conventional right ventricular apex pacing?

A30-4 Right ventricle outflow tract and dual site right ventricular pacing &amp; an alternative for conventional right ventricular apex pacing?

Influence of native conduction status on clinical results with right ventricular outflow tract pacing

Influence of native conduction status on clinical results with right ventricular outflow tract pacing

Resynchronization pacing is a useful adjunct to the management of acute heart failure after surgery for congenital heart defects

The acute hemodynamic effect of atrioventricular (AV) and inter/intraventricular (IV) resynchronization accomplished by temporary pacing using multiple epicardial pacing wires was evaluated in 20 children (aged 3.4 months to 14.0 years) after surgery for congenital heart defects fulfilling the following criteria: (1) presence of AV and/or IV conduction delay, and (2) need for inotropic support. AV resynchronization (n = 13) was achieved by AV delay optimization during atrial synchronous right ventricular outflow tract pacing. IV resynchronization (n = 14) was accomplished by atrial synchronous pacing from the right ventricular lateral wall in 7 patients with right bundle branch block and normal AV conduction and by atrial synchronous multisite ventricular pacing in another 7 patients with previously performed AV resynchronization. Compared with baseline values, AV resynchronization resulted in an increase in arterial systolic, mean, and pulse pressures by 7.2 ± 8.3% (p <0.01), 8.6 ± 8.1% (p <0.005), and 6.9 ± 13.5% (p = NS), respectively. IV resynchronization used either alone or added to previously performed AV resynchronization led to a pressure increase of 7.0 ± 4.7%, 5.9 ± 4.7%, and 9.4 ± 7.8%, respectively (p <0.001 for all). The combined effect of AV and IV resynchronization resulted in a systolic, mean, and pulse pressure increase of 10.2 ± 5.0% (range 4.0 to 19.1), 8.6 ± 5.4% (range 0.8 to 14.8), and 15.2 ± 8.5% (range 6.1 to 33.3), respectively (p <0.001 for all). The increase in systolic arterial pressure after IV resynchronization was positively correlated with the initial QRS duration (r = 0.62, p <0.05) and extent of QRS shortening (r = 0.66, p <0.05). In conclusion, resynchronization pacing led to a significant increase in arterial blood pressure and was a useful adjunct to the treatment of acute postoperative heart failure in patients with AV and/or IV conduction delay.

Estimulación permanente del haz de His tras ablación mediante radiofrecuencia del nodo auriculoventricular en pacientes con trastorno de la conducción suprahisiano

The asynchronic contraction of the left ventricle due to left bundle branch block or right ventricular pacing is inferior from a hemodynamic point of view to the synchronic contraction through the conduction system. Several authors have reported some cases of pump failure and deterioration of mitral regurgitation after AV nodal ablation. Alternative sites of pacing such as the right ventricular outflow tract pacing have been proposed in order to avoid these complications. Direct His bundle pacing might be a new alternative for permanent pacing, however, it has not been extensively evaluated in humans yet. Our aim is to prove the feasibility of permanent His pacing in terms of stability, thresholds and pump function. patients without structural heart disease, selected for AV nodal ablation due to uncontrolled paroxysmal atrial fibrillation, or for pacemaker implantation due to supraHis conduction disturbance, with normal conduction system. An active fixation permanent lead was placed in His position using an steering guidewire and a diagnostic catheter as an anatomical reference. We also implanted a lead in the right atrial appendage and both were connected to a DDDR generator. Pacing thresholds and ecocardiographic ventricular function parameters were evaluated (ejection fraction, cavity size, mitral regurgitation). 12 patients met the inclusion criteria. Successful His pacing was achieved in 8 out of 12 cases (66%) with acceptable thresholds at implantation (1.24 +/- 0.13 volts at 0.5 ms) and during follow up at 3 months (1.31 +/- 0.20 volts at 0.5 ms). Neither a significant change in the ecocardiographic parameters not a deterioration in the clinical status caused by ablation or stimulation was evidenced. The His bundle may be the site of choice for long term pacing in patients with AV block and normal infraHis conduction system.

Improved Left Ventricular Relaxation During Short-term Right Ventricular Outflow Tract Compared to Apical Pacing

Pacing-induced asynchrony may deteriorate left ventricular function; however, limited data exists in humans. The aim of our study was to compare left ventricular hemodynamics during short-term atrioventricular sequential pacing from the right ventricular apex and from the outflow tract of the right ventricle. Three 5-min pacing intervals were applied in a random order, at a rate of 15 beats/min above the resting sinus rate. Atrioventricular sequential pacing from the two sites was compared with atrial pacing. During each pacing mode, left ventricular pressure was recorded, and cardiac output was calculated using Doppler echocardiography. Cardiac catheterization laboratory. Twenty patients (18 male, mean age 62 +/- 11 years) without structural heart disease were studied. During atrial pacing, maximum negative first derivative of pressure (dp/dt) was 1,535 +/- 228 mm Hg/s; during pacing from the apex it decreased to 1,221 +/- 294 mm Hg/s (p = 0.0001), but was not significantly different during pacing from the outflow tract (1,431 +/- 435 mm Hg/s, p > 0.05). Isovolumic relaxation time constant (tau) during atrial pacing was 39.7 +/- 11.9 ms; during pacing from the apex, it increased to 47.9 +/- 14.0 (p = 0.001), but was not significantly different during pacing from the outflow tract (42.5 +/- 11.2, p > 0.05). Peak systolic pressure decreased significantly during atrioventricular sequential pacing from either site; however, it did not differ between the two sites. No differences in end-diastolic pressure, maximum positive dp/dt, or cardiac output could be demonstrated. In patients with no structural heart disease, short-term right ventricular outflow tract pacing is associated with more favorable diastolic function, compared to right ventricular apical pacing.

Importance of the site of ventricular tachycardia origin on left ventricular hemodynamics in humans.

Experimental animal data have indicated that the site of ventricular tachycardia origin and, hence, the degree of asynchronous contraction, may influence the hemodynamic tolerance during sustained ventricular tachycardia. However, data in man are scarce. We studied patients with preserved left ventricular function and absence of significant coronary artery disease. Ventricular tachycardia was simulated with rapid pacing (at 120 and 150 beats/min), performed randomly, from the right ventricular apex or the right ventricular outflow tract. Following pacing from one site, it was repeated from the alternate site. Compared to outflow tract pacing, QRS duration was significantly longer during rapid pacing from the apex. Left ventricular pressure was recorded using a micromanometer-tipped catheter. During sinus rhythm, peak systolic pressure was 142 +/- 14 mmHg; at 120 beats/min, it decreased to 109 +/- 12 mmHg during pacing from the apex and to 127 +/- 21 mmHg during pacing from the outflow tract (P = 0.008). This difference diminished at 150 beats/min (101 +/- 16 mmHg vs 112 +/- 16 mmHg, respectively, P = 0.21). During sinus rhythm end-diastolic pressure was 13 +/- 1 mmHg, which did not change significantly during pacing at 120 beats/min. During pacing at 150 beats/min, end-diastolic pressure increased to 21 +/- 3 mmHg during pacing from the apex and to 16 +/- 2 mmHg during pacing from the outflow tract (P = 0.005). Changes in first derivative of pressure and in isovolumic relaxation time constant were comparable during pacing from the two sites. Thus, it seems that tachycardias originating from the right ventricular outflow tract result in more favorable left ventricular hemodynamics, compared to those from the right ventricular apex.

Optimal right ventricular pacing site in chronically implanted patients: A prospective randomized crossover comparison of apical and outflow tract pacing

ObjectivesTo evaluate the long-term functional and hemodynamic effects of right ventricular outflow tract (RVOT) pacing by comparison with right ventricular apical (RVA) pacing.BackgroundAcute studies have suggested that RVOT pacing could significantly improve cardiac performance in comparison with RVA pacing but no data are available in chronically implanted patients.MethodsSixteen patients with chronic atrial tachyarrhythmia and complete AV block were included. Left ventricular ejection fraction (LVEF) was ≥40% in ten and <40% in six. Patients were implanted with a standard DDDR pacemaker connected to two ventricular leads. A screw-in lead was placed at the RVOT and connected to the atrial port. A second lead was positioned at the RVA and connected to the ventricular port. Right ventricular outflow tract and RVA pacing was achieved by programming either the AAIR or the VVIR mode respectively. Four months later patients were randomized so as to undergo either RVOT or RVA pacing for three months according to a blind crossover protocol. Apart from the pacing mode, programming remained unchanged throughout the study. At the end of each period, NYHA class, LVEF, exercise time and maximal oxygen uptake were assessed.ResultsNo significant difference was observed between the two modes for all the parameters analyzed. These identical results were observed in all patients globally, in patients with LVEF ≥40% as in those with LVEF <40%.ConclusionsWithin the limits of this study, no symptomatic improvement or hemodynamic benefit was noted after three months of RVOT pacing, by comparison with RVA pacing.

Comparison of Right Ventricular Outflow Tract and Apical Lead Permanent Pacing on Cardiac Output

Cardiac output was measured in 89 patients using transthoracic continuous-wave echo Doppler comparing right ventricular outflow tract pacing with the right ventricular apex at the time of permanent pacemaker implantation. Overall, cardiac output improved 18.8% (p <0.0001) and cardiac index 21.0% (p <0.0001) with outflow tract placement; patients with a lower baseline cardiac index had a greater percent improvement with outflow tract placement.

Cardiac pacing in patients with dilated cardiomyopathy.

Studies of both the acute and chronic effects of permanent cardiac pacing in patients with dilated cardiomyopathy have produced contradictory results. Similarly, theoretically promising novel pacing techniques such as multisite, His bundle, and right ventricular outflow tract pacing have also yielded mixed results in preliminary studies. In general, at the present time, pacing therapy should be considered investigational for patients with dilated cardiomyopathy who do not have traditional bradycardia indications; nevertheless, pacing therapy may be useful in a small population of patients with dilated cardiomyopathy who have inappropriate timing of left ventricular and left atrial contraction. The beneficial effects of cardiac pacing in some patients with DCM cannot be dismissed out of hand; they must be explained. What is needed is clarification of the best methods to measure any benefits of this therapy: among the options are echocardiographically determined parameters of forward flow and AV valve function, exercise test parameters such as duration and O2 consumption, global and regional ejection fraction, functional classification, quality of life questionnaires, neurohumoral parameters such as plasma atrial natriuretic peptide and catecholamines, and, finally, disease progression and survival.

Multisite pacing for end-stage heart failure: early experience.

Our objective was to improve hemodynamics by synchronous right and left site ventricular pacing in patients with severe congestive heart failure (CHF). Previous studies reported a benefit of dual chamber pacing with a short AV delay in patients with severe CHF. Other works, however, show contradictory results. Deleterious effects due to a desynchronization of right (RV) and left ventricular (LV) contractions have been suggested. This study included eight subjects with widened QRS and end-stage heart failure despite maximal medical therapy, who refused, or were not eligible to undergo heart transplantation, Each patient underwent a baseline, invasive hemodynamic evaluation with insertion of three temporary leads to allow different pacing configurations, including RV apex and outflow tract pacing, and biventricular pacing between the RV outflow tract and LV and RV apex and LV. According to the results of this baseline study, the configuration of preexistent pacemakers was modified or new systems were implanted to allow biventricular pacing, which, in patients with sinus rhythm, was atrial triggered. Biventricular pacing increased the mean cardiac index (CI) by 25% (from a baseline of 1.83 +/- 0.30 L/min per m2, P < 0.006), decreased the mean V wave by 26% (from a baseline of 36 +/- 12 mmHg, P < 0.004), and decreased pulmonary capillary wedge pressure by 17% (from a baseline of 31 +/- 10 mmHg, P < 0.01). Four patients died (1 preoperatively, 1 intraoperatively, 2 within 3 months, and 1 of a noncardiac cause). The four surviving patients have clinically improved from New York Heart Association Functional Class IV to Class II. In these survivors, CI decreased by 15% (P < 0.007) when multisite pacing was turned off during follow-up. In patients with end-stage heart failure, multisite pacing may be associated with a rapid and sustained hemodynamic improvement.

Relation between regional electrical activation time and subepicardial fiber strain in the canine left ventricle

To determine the relation between regional electrical activation time and fiber strain, epicardial electrical activation and deformation were measured in six open-chest dogs at the left ventricular anterior free wall after 15 min of right atrial, left ventricular free wall, left ventricular apex, or right ventricular outflow tract pacing, when end-diastolic pressure was normal or elevated (volume-loading). Regional electrical activation was measured using a 192-electrode brush. Regional subepicardial fiber strain (ef) was measured simultaneously in 16 regions, using optical markers which were attached to the epicardial surface and recorded on video. When relating regional ef during the ejection phase to regional activation time, the best correlation was found when a hemodynamic time reference rather than an electrophysiological one is used. Using the moment of the maximum rate of change of left ventricular pressure as the time reference for electrical activation, regional electrical activation time (t(ea)) and the degree of ef during the ejection phase could be fitted by a linear regression equation ef = a t(ea) + b, in which a = -3.46 +/- 0.73 s-1 an b = -0.28 +/- 0.05. For electrical activation times ranging from -40 to -80 ms, fiber strain was estimated with an accuracy of +/- 0.026 (+/- SE) with this relation. During right atrial pacing, t(ea) and ef were on the average -48 ms and -0.10 respectively. On further investigation, the relation between ef and t(ea) appeared to be influenced by end-diastolic pressure. For normal (1.1 kPa) and elevated end-diastolic pressure (1.8 kPa), the slope of the linear regression line was -3.96 and -2.86 s-1, respectively. Three conclusions may be drawn. Firstly, the time interval between the moment of regional electrical activation and the moment of the maximum rate of change of left ventricular pressure is an index of regional fiber strain. Secondly, it can be concluded from the above equations that electrical asynchrony of more than 30 ms causes non-uniformities in the degree of ef of the order of mean ef during pacing from the right atrium. Finally, differences in fiber strain during asynchronous electrical activation are less pronounced at larger filling pressures.

The time sequence of electrical and mechanical activation during spontaneous beating and ectopic stimulation.

The relation between the sequence of electrical (E) and mechanical (M) activation was studied at the LV anterior wall of open-chest dogs (n = 11). M activation was defined as the onset of epicardial fibre shortening, as measured with a recently developed video technique. E activation was determined with a brush of extracellular electrodes. The delay between activation of basal and apical regions was consistently larger for M activation than for E activation: during spontaneous beating: 20.5 +/- 7.30 ms vs 8.8 +/- 3.31 ms, during right ventricular outflow tract pacing: 50.3 +/- 7.69 ms vs 39.0 +/- 5.31 ms and during left ventricular apex pacing 40.1 +/- 10.03 ms vs 25.4 +/- 9.30 ms, respectively (P less than 0.05 in all cases). The E-M time interval was consistently shorter in early than in late activated regions: 32 +/- 10 vs 41 +/- 8 ms during RV outflow tract pacing (P = 0.09) and 24 +/- 30 vs 40 +/- 24 ms during LV apex pacing (P less than 0.05). Electrical asynchronies larger than 40 ms resulted in decreases of systolic blood pressure and stroke volume. This study shows that the asynchrony of cardiac motion exceeds that of electrical activation because the time interval between electrical activation and onset of fibre shortening is larger the later a particular region is activated. Possible explanations for this phenomenon are discussed.

Effect of electrical activation site on left ventricular performance in ventricular tachycardia patients with coronary heart disease

Some patients with ventricular tachycardia (VT) remain virtually asymptomatic, whereas others have syncope despite similar VT rates. The role of ventricular activation site on left ventricular (LV) function was examined in 10 patients undergoing electrophysiologic evaluation for recurrent ventricular arrhythmias. Radionuclide ventriculograms were acquired to calculate LV volumes and aortic or LV pressure was measured during right atrial and right ventricular (RV) pacing. RV apical pacing resulted in end-diastolic volumes similar to those achieved with right atrial pacing (171 ± 27 vs 175 ± 19 ml), whereas RV outflow tract pacing showed a trend toward lower volumes (168 ± 32 vs 177 ± 33 ml). Comparison between RV apical and RV outflow tract pacing showed that apical activation resulted in higher end-diastolic volumes (216 ± 26 vs 194 ± 22 ml, p = 0.020), end-systolic volumes (175 ± 25 vs 158 ± 20 ml, p = 0.041), stroke volumes (42 ± 4 vs 36 ± 6 ml, p = 0.046), peak rates of LV ejection (309 ± 57 vs 245 ± 40 ml/s, p = 0.034) and peak rates normalized for differences in end-diastolic volume (1.5 ± 0.3 vs 1.3 ± 0.3; p = 0.047) without a significant increase in peak pressures (131 ± 12 vs 127 ± 14 mm Hg, p > 0.30) or ejection fractions (24 ± 5 vs 22 ± 4%, p = 0.187). These changes were accompanied by an increase in LV RV stroke count ratios during RV apical vs RV outflow tract pacing (1.6 ± 0.2 vs 1.2 ± 0.2, p = 0.030), suggesting the development of mitral regurgitation. Temporal Fourier analysis of the radionuclide ventriculograms showed considerable variation in the LV patterns of emptying from different activation sites. It is hypothesized that the altered activation sequence associated with RV apical pacing disrupts papillary muscle function, inducing mitral regurgitation and, as a consequence, results in higher LV volumes and ejection rates than RV outflow tract activation. These site-dependent differences in LV performance suggest that the location of ventricular activation may be an important determinant of the hemodynamic consequences of sustained ventricular tachyarrhythmias.