Research Progress in the Effect of His-Purkinje Conduction System Pacing on Cardiac Function / 中山大学学报(医学科学版)

Cardiac pacing is an effective treatment for cardiac pacing and conduction dysfunction and severe heart failure. However， the conventional right ventricular pacing may increase the incidences of heart failure and atrial fibrillation， and biventricular pacing has a relatively high non-response rate. As a new technique of physiological pacing， a number of studies in recent years have been conducted to show the stability of pacing parameters and good cardiac synchronization of his-purkinje system pacing. This article reviews the current status of research and progress in the effects of his-purkinje conduction system pacing on cardiac function， so as to provide a theoretical basis for promoting the development of this technology.

Mejoría clínica, hemodinámica y de marcadores bioquímicos tras estimulación ventricular desde el área de la rama izquierda / Clinical, hemodynamic and biochemical improvement related to left bundle branch area pacing

Resumen Introducción: La estimulación ventricular derecha puede provocar insuficiencia cardiaca y disfunción ventricular. La estimulación en el área de la rama izquierda (ERI) permite capturar el sistema His-Purkinje. La ERI se ha estudiado en la estimulación ventricular y en la terapia de resincronización cardiaca. La evolución de los péptidos natriuréticos (NT-proBNP) asociada a la ERI no ha sido estudiada hasta el momento. Métodos: Se incluyeron pacientes consecutivos remitidos para implante de marcapasos o terapia de resincronización cardiaca. El implante del electrodo de ERI se realizó siguiendo la técnica descrita por Huang et al. Los pacientes eran sometidos a ecocardiograma y determinación de NT-proBNP antes y cuatro semanas después del procedimiento. Resultados: Se analizaron 50 pacientes con implante exitoso y seguimiento completo. No hubo diferencias significativas entre los umbrales medidos durante el procedimiento y los obtenidos al cabo de 12 semanas. La ERI logró una reducción significativa de la anchura del complejo QRS (148 ± 21 vs. 107 ± 11 ms; p = 0.029). La ERI logró una reducción significativa de la clasificación funcional en el conjunto de la muestra y una reducción significativa de NT-proBNP (2,888.2 ± 510 vs. 1,181 ± 130 pg/ml; p = 0.04). En pacientes con fracción de eyección del ventrículo izquierdo (FEVI) < 50% y asincronía se logró un incremento significativo de la FEVI con la ERI (40.2 ± 7 vs. 55.2 ± 7%; p < 0.001). Conclusiones: La ERI es factible en la mayoría de pacientes y se asocia con una reducción de la duración del complejo QRS. La ERI no condiciona un efecto deletéreo sobre la FEVI a corto-medio plazo; además, en aquellos pacientes con FEVI deprimida y asincronía ventricular permite incrementar la FEVI.

Abstract Background: Right ventricular pacing is associated with risk of heart failure and left ventricular dysfunction. Left bundle branch area pacing (LBBP) has emerged as an alternative method for delivering physiological pacing. The effect of LBBP on N-terminal pro-brain natriuretic peptide (NT-proBNP) has not been investigated. Method: Finally, 50 patients referred for pacemaker implantation were included. LBBP was performed as described previously by Huang et al. Transthoracic echocardiogram and NT-proBNP were performed before and four weeks after the procedure. Results: 50 patients were analyzed. There were not differences between ventricular thresholds during the procedure and 3 months later, LBBP significantly reduced QRS complex duration (148 ± 21 vs. 107 ± 11 ms; p = 0.029). LBBP significantly improved NYHA functional class and reduced NT-proBNP concentration (2888.2 ± 510 vs. 1181 ± 130 pg/ml; p = 0.04). In patients showing left ventricular ejection fraction (LVEF) < 50% and ventricular desynchrony LBBP showed a significant LVEF increase (40.2 ± 7 vs. 55.2 ± 7%; p < 0.001). Conclusions: LBBP was feasible and safe in most of patients. LBBP was associated with reduction in QRS width and with increase in LVEF in patients with ventricular desynchrony, while in patients with normal LVEF it remained unchanged during follow-up.

Efficacy of Cardiac Resynchronization Therapy Using Automated Dynamic Optimization and Left Ventricular-only Pacing

BACKGROUND: Although device-based optimization has been developed to overcome the limitations of conventional optimization methods in cardiac resynchronization therapy (CRT), few real-world data supports the results of clinical trials that showed the efficacy of automatic optimization algorithms. We investigated whether CRT using the adaptive CRT algorithm is comparable to non-adaptive biventricular (BiV) pacing optimized with electrocardiogram or echocardiography-based methods. METHODS: Consecutive 155 CRT patients were categorized into 3 groups according to the optimization methods: non-adaptive BiV (n = 129), adaptive BiV (n = 11), and adaptive left ventricular (LV) pacing (n = 15) groups. Additionally, a subgroup of patients (n = 59) with normal PR interval and left bundle branch block (LBBB) was selected from the non-adaptive BiV group. The primary outcomes included cardiac death, heart transplantation, LV assist device implantation, and heart failure admission. Secondary outcomes were electromechanical reverse remodeling and responder rates at 6 months after CRT. RESULTS: During a median 27.5-month follow-up, there was no significant difference in primary outcomes among the 3 groups. However, there was a trend toward better outcomes in the adaptive LV group compared to the other groups. In a more rigorous comparisons among the patients with normal PR interval and LBBB, similar patterns were still observed. CONCLUSION: In our first Asian-Pacific real-world data, automated dynamic CRT optimization showed comparable efficacy to conventional methods regarding clinical outcomes and electromechanical remodeling.

Prevalence and Clinical Predictors of Right Ventricular Dysfunction in Patients with Chronic Right Ventricular Pacing

BACKGROUND AND OBJECTIVES: Numerous clinical studies have demonstrated chronic right ventricular (RV) pacing induced left ventricular (LV) dyssynchrony and LV systolic dysfunction in patients with permanent pacemaker. However, only a limited number of studies have focused on RV dysfunction. We sought to determine the prevalence and identify the clinical predictors of RV dysfunction in patients with chronic RV pacing. SUBJECTS AND METHODS: We enrolled 72 patients (mean age 72.7±11.1 years, men 36.1%) who underwent permanent pacemaker implantation without RV dysfunction in baseline examination. Baseline clinical characteristics, laboratory data, echocardiographic parameters and pacing profiles were assessed. Follow up 2-dimentional echocardiography was used to identify the presence of RV dysfunction. RESULTS: We divided patients based on the criteria of either presence or absence of RV dysfunction, where RV dysfunction is defined as decreased tricuspid annulus systolic velocity (<11 cm/sec) in tissue Doppler image. Sixteen patients (22.2%) in our study showed meaningful RV dysfunction. Patients with RV dysfunction had lower LV ejection fraction (57.5±10.8% versus 64.6±9.1%, p<0.05) and higher B-type natriuretic peptide (BNP) levels (700.3±152.9 pg/mL versus 329.4±332.4 pg/mL, p<0.05) compared to patients without RV dysfunction. Implantation of VVI type pacemaker was associated with presence of RV dysfunction (81.3% versus 33.3%, p<0.05). Higher cumulative ratio of total RV pacing was associated with increased tendency for RV dysfunction. No statistically significant correlation was observed between the groups (70.7±13.2% in RV dysfunction group, 61.7±38.3% in non-RV dysfunction group, p=0.094). CONCLUSION: In this study, meaningful proportion of patients showed chronic RV pacing induced RV dysfunction. RV dysfunction was associated with lower LV systolic function, higher BNP level and VVI type pacemaker.

Feasibility and Safety of Ventricular Pacing Through Coronary Sinus Comparing with Traditional Right Ventricular Pacing / 昆明医科大学学报

Objective To study the feasibility and safety of coronary sinus (CS) ventricular pacing comparing with traditional right ventricular (RV) pacing in ordinary pacing treatment.Methods Sixty-one patients with an indication of pacemaker implantation were randomized into traditional RV pacing group and CS ventricular pacing group.The success rate,complications,preoperative and postoperative QRS wave duration and pacemaker parameters were compared between the two groups.Results (1) The instant success rate in traditional RV pacing and the CS pacing groups were 100％ and 68.97％ (P＜0.01);the surgical success rate was significantly higher by using left ventricular electrode than the ventricle tined electrode in CS pacing group (85.71％ and 25％,P＜0.05).There was no significant difference in the incidence of complications between the two groups (P＞0.05);(2) The increase of QRS complex width at postoperative 1 month in CS pacing group is significantly less than the RV pacing group (P＜0.05);(3) Although the pacing threshold and electrode impedance during operation,postoperative 1 month and 3 months in CS pacing group were higher than RV pacing group (P＜0.05),the CS pacing was effective.Conclusion The CS ventricular pacing is as safe and effective as traditional RV pacing,and is more consistent with physiological ventricular activation sequence.Using left ventricular electrode can significantly improve the success rate of CS ventricular pacing.

Tratamiento del síncope neuralmente mediado con marcapasos: utilidad del sensor de asa cerrada / Neurally mediated syncope treatment with pacemakers: Utility of closed-loop sensor

El síncope vasovagal es una entidad frecuente, de difícil manejo, con alta tasa de recurrencia aun con manejo médico. Se ha estudiado la estimulación cardiaca en pacientes con respuesta cardioinhibitoria en la mesa basculante con resultados contradictorios. Los estudios iniciales mostraron buenos resultados, que no lograron reproducirse cuando se introdujo el diseño doble ciego. La mayoría de estos estudios se realizaron con marcapasos con sensores convencionales. Las guías actuales de dispositivos indican la terapia de estimulación cardiaca en síncope vasovagal con respuesta cardioinhibitoria como una alternativa ante la no respuesta al tratamiento convencional. Existe evidencia reciente que indica que los marcapasos con sensores de asa cerrada (CLS, del inglés closed-loop sensor) muestran mejores resultados que los sensores convencionales; estos estudios, aunque con población pequeña, reportan reducciones de la frecuencia de síncopes y presíncopes. Este tipo de dispositivos actúan en etapas más tempranas de la cascada de eventos fisiopatológicos del síncope vasovagal, detectando cambios en la impedancia ventricular antes de la caída de la frecuencia cardiaca, lo cual permite intervenir en forma precoz con estimulación para evitar el síncope.

The vasovagal syncope is a frequent entity of difficult management with a high rate of recurrence despite medical management. Cardiac pacing has been studied in patients with cardioinhibitory response on tilt table with inconsistent results. Initial studies showed beneficial results were achieved, but they could be reproduced when the double-blind design was introduced. Most of these studies were performed with conventional pacemaker sensors. Device current guidelines indicate pacing therapy in vasovagal syncope with cardioinhibitory response as an alternative to non-response to conventional therapy. There is recent evidence that pacemakers with closed-loop sensors (CLS) show better results than conventional sensors; these studies, although limited to small groups of population, show reductions in the frequency of syncopes and presyncopes. These devices work in earlier stages of the cascade of pathophysiological events of the vasovagal syncope, detecting changes in ventricular impedance before the fall in heart rate, thus allowing early intervention as stimulation to prevent syncope.

Electrocardiograma de superficie en pacientes con dispositivos de estimulación cardíaca / Surface electrocardiogram in patients with cardiac pacing devices

Con el paso del tiempo el número de pacientes portadores de dispositivos de estimulación cardíaca (marcapasos, resincronizadores y desfibriladores) ha aumentado de manera exponencial y ha llevado a que médicos de todas las especialidades tengan mayor exposición a los electrocardiogramas. Conocer el funcionamiento de estos dispositivos es, por tanto, necesario para comprender los cambios que se producen en el electrocardiograma de superficie, identificar los hallazgos normales y reconocer las distintas manifestaciones de la disfunción de estos dispositivos. En este artículo se revisan, de manera clara y concreta, conceptos básicos de diseño, funcionamiento y programación de los dispositivos de estimulación cardíaca, de modo que el lector desarrolle un esquema para la evaluación electrocardiográfica de estos.

Over the last decades, the number of patients with cardiac stimulation devices (including pacemakers, resynchronization devices and automatic implantable cardiac defibrillators) has increased exponentially, exposing an ever increasing number of health professionals from different areas of medicine to their electrocardiograms. Thorough knowledge of proper device function is crucial to understanding electrocardiographic changes induced by cardiac stimulation, identifying normal findings, and recognizing the different manifestations of device malfunction. In this article, basic concepts on device design, programming and proper function will be discussed, allowing the reader to develop an organized step wise approach to interpret the electrocardiogram of patients with cardiac stimulation devices.

Impact of paced QRS duration on heart function in patients with right ventricular apical pacing / 实用医学杂志

Objective To investigate the impact of paced QRS duration (pQRSd) on heart function in patients with right ventricular apical pacing. Methods Seventy-six patients with Ⅲ° atrioventricular block received pacemaker treatment were enrolled and randomized into group A (pQRSd 0.05). At 24 months after implanting, LAD、LVEDD、LVESD of group B increased significantly compared with those of group A [LAD,( 44.5 ± 6.2) mm vs (41.6 ± 5.1) mm, LVEDD, (52.7 ± 9.3) mm vs (48.2 ± 7.5) mm, LVESD, (37.5 ± 5.6) mm vs (33.8 ± 4.9)mm, each P 0.05)between two groups during 24-month follow-up. Conclusion The prolonged paced QRS duration has a detrimental effect on long-term cardiac function during RVA pacing in patients with Ⅲ°atrioventricular block.

Unexpected and fatal hemodynamic collapse during transapical transcatheter aortic valve implantation: A case report / 대한마취과학회지

Although transcatheter aortic valve implantation (TAVI) is generally accepted as an alternative or promising treatment option for patients with decompensated cardiovascular disease in an inoperable or high-risk condition, severe hypotension and/or arrhythmia associated with rapid ventricular pacing still poses a challenge to many clinicians. This report describes a 79-year-old patient who experienced fatal hemodynamic collapse, which suddenly developed after a rapid ventricular pacing in spite of pre-administration of vasopressor. The procedure and anesthesia were uneventful until the first rapid ventricular pacing was applied. Following rapid ventricular pacing, his cardiovascular state was severely compromised and could not be recovered. Despite early initiation of extracorporeal membrane oxygenation device and supportive care, he died from heart failure on post-procedure day four.

Controlled transient respiratory arrest along with rapid right ventricular pacing for improving balloon stability during balloon valvuloplasty in pediatric patients with congenital aortic stenosis - A retrospective case series analysis.

Rapid right ventricular pacing is safe, effective, and established method to provide balloon stability during balloon aortic valvuloplasty (BAV). Controlled transient respiratory arrest at this point of time may further reduce left ventricular stroke volume, providing an additional benefit to maintain balloon stability. Two groups were studied. Among the 10 patients, five had rapid pacing alone (Group A), while the other five were provided with cessation of positive pressure breathing as well (Group B). The outcomes of BAV in the two groups of patients were studied. One patient in Group A had failed balloon dilatation even after the fourth attempt, while in Group B there were no failures. The peak systolic gradient reduction was higher in Group B (70.05% in comparison to 52.16% of group A). In Group A, five subjects developed aortic regurgitation (grade 2 in four and grade 3 in one, while no grade 3 aortic regurgitation developed in any patient in Group B). Controlled transient respiratory arrest along with rapid ventricular pacing may be effective in maintaining balloon stability and improve the outcome of BAV.

The Use of Rapid Ventricular Pacing to Facilitate Stent Graft Deployment in the Distal Aortic Arch / 대한흉부외과학회지

Systemic hypotension has been traditionally used to facilitate deployment of thoracic stent grafts. Decreasing blood pressure with vasodilating agents further increases cardiac output and, consequently, the cardiac output-mediated windsock effect during deployment. Use of rapid ventricular pacing reduces the windsock effect during stent graft deployment and allows the graft to appose to the aortic wall under zero cardiac output, thus minimizing aortic wall shear stress. In this case we report the use of transvenous rapid ventricular pacing, a safe and reproducible technique to allow precise deployment of a Valiant Captivia stent graft in the distal thoracic arch for a saccular thoracic aneurysm.

Estabilización del balón mediante estimulación cardíaca en la valvuloplastía aórtica / Balloon stabilization by means of cardiac stimulation during aortic valvuloplasty

Objetivo: Evaluar la estimulación ventricular rápida en la Valvuloplastía Aórtica Percutánea como estrategia para obtener estabilidad del balón. Material y métodos: En septiembre de 2004 se inició un protocolo prospectivo. Tres enfermos masculinos consecutivos con estenosis valvular aórtica significativa fueron tratados con este método. Las edades fueron 13, 6 y 5 años. En todos se colocó un electrodo bipolar en el ventrículo derecho. Durante el procedimiento se registró la presión arterial sistémica con un catéter en la aorta descendente. La estimulación ventricular se inició a una frecuencia de 150 por minuto y se aumentó hasta obtener un descenso del 50% en la presión arterial sistémica y entonces el balón se infló para realizar la valvuloplastía aórtica. La estimulación se suspendió hasta que el balón fue completamente desinflado. Resultados: Los gradientes transvalvulares antes de la valvuloplastía fueron 90 y 110 mmHg. Las presiones en aorta fueron de 90, 110 y 55 mmHg. Se obtuvo una reducción del 50% de la presión sistémica con 170, 250 y 220 por minuto de estimulación. La duración de la estimulación rápida en los tres casos fue de 15 segundos. Se logró estabilización del balón sin movimientos en los dos casos. Los gradientes obtenidos después de la valvuloplastía fueron 23, 28 y 15 mmHg. No hubo modificación en el grado de insuficiencia aórtica después del procedimiento. En el primero se mantuvo grado I y en el segundo y tercer casos, no se observó regurgitación en el aortograma. Conclusiones: La estimulación cardíaca rápida estabiliza el balón durante la valvuloplastía, es segura, efectiva y puede disminuir la incidencia de insuficiencia aórtica.

Objective: To evaluate rapid ventricular pacing in balloon aortic valvuloplasty, an initial strategy to achieve balloon stability. Material and methods: From September to December 2004, a prospective protocol was started: three male consecutive patients with aortic valve stenosis were treated by this strategy. Age of the patients were 13, 6 and 5 years old. All had a bipoplar pacing catheter placed in the right ventricle. Invasive systemic pressures were documented with a catheter in the descending aorta. Rapid ventricular pacing was initiated at the rate of 150 per minute and increased to a rate required to achieve a drop in systemic pressure by 50%. The balloon was inflated only after the pacing rate was reached and the blood pressure dropped. Pacing was continued until the balloon was completely deflated. Results: The systolic gradients across the aortic valve before balloon dilatation were 90, 110 and 55 mmHg. The systolic pressures in aorta were 90 and 110 mmHg. The pacing rate to drop the pressure by 50% were 170, 250 and 220 per minute. The pacing time was 15 seconds in all patients. Balloon stability at time of inflation was achieved in all cases with no balloon movement. The post-ballooning gradients were 23, 28 and 15 mmHg. Angiogram performed post balloon dilatation showed no change compared with the pre-balloning angiogram in aorta: trivial aortic incompetence in the first case and none in the second and third cases. Conclusions: Rapid ventricular pacing to stabilise the balloon during balloon aortic valvuloplasty seems to be safe and effective and may decrease the incidence of aortic incompetence.

Initial results with left ventricular pacemaker lead implantation using a 2187 left ventricular pacing lead / 中国介入心脏病学杂志

Objective The aim was to investigate the manupulation and the localization of LV Lead, and to evaluate LV Lead usefulness in biventricular pacing.Methods 9 Patients with enlarged left ventricle, chronic heart failure, CLBBB and refractory to chemical therapy were selected in this study, including 8 males and 1 female. Coronary sinus venography was performed by injecting contrast medium retrogradely at coronary sinus ostium in 7 cases or antegradely into left coronary artery in 2 cases. LV lead was introduced to CS and localized at targeting vein of LV through a "peel away" guiding sheath, which was placed in CS via left subclavian vein route. Results Coronary sinus and its tributaris were clearly visualized by both antegrate cardiac venography and retrograte cardiac venography. 2187 leads were implanted into targeting veins through "peel away" guiding sheaths in 6 cases and directly introduced in 2 cases, while in other case the lead was inserted into coronary sinus directly after a failed procedure via a "peel away" guiding sheath. The leads were placed in great cardiac vein in 1 case, lateral LV vein in 2 cases, left posterior LV vein in 2 case and left posterolateral veins in 4 cases. The acute pacing and sensing thresholds measuered during the implanting procedure were in normal limits. 2187 leads were still fully functional without dislocalization during follow up of average 253 days. Conclusion CS and its tributaries can be clearly shown by antegrate and retrograte venographies. The introduction of 2187 left ventricular pacing is easily performed directly or through a preformed "peel away" guiding sheath. LV epicardium pacing by 2187 LV lead implanted through CS is feasible and reliable.

VDD Pacemaker in an Unipolar Lead for Clinical Practice / 中国实用内科杂志

Objective To inquire into the forward clinical results of ventricular pacing, dual-chamber sensing, atrial-triggered, and ventricular-inhibited (VDD) Pacemaker in an unipolar lead.Methods 16 patients with the pacemaker were studied from 1993 to 2002, including 12 male patients and 4 female patients at 49 to 75 years old (average age 64 4 7 8 years old). They were in normal sinus rhythmia with complete or high degree atrial-ventricular block. Lead electrode was inserted through subclavian venous access, and the pacemaker was implanted in the same side as the electrode.Results All patients were followed up from 1 to 112 months (average 68 8 6 3 months) after pacemaker implantation. Their heart functions were improved, symptoms disappeared, life quality remarkably improved. Atrial sensing of VDD was good. One patient was died from coronary heart disease with heart failure by following up for 42 months, but the rest were healthy. Conclusions VDD pacemaker implantation was simple, easy to perform if its indication was appropriate. It could alleviate patients symptom and its therapy was effective. We should think highly of using VDD pacemaker, especially at poor region.

Improvement of minimizing ventricular pacing in dual chamber pacemaker / 中国实用内科杂志

The data from clinical studies have shown that conventional dual chamber pacing results in high percentages of right ventricular apical pacing,which causes electromechanical desynchronization and has been linked to an increased risk of heart failure and atrial fibrillation.Nowadays,we can use some special algorithms to minimize ventricular pacing,promote atrioventricular conduction and improve hemodynamics in patients with pacemakers.This review summarizes the genesis,some algorithms and clinical studies about minimizing ventricular pacing.

Change of Coronary Flow Reserve in the Dogs: Influence of Atrial and Ventricular Pacing, Ventricular Preload and Afterload

BACKGROUNG AND OBJECTIVES: The aim of this study was to analyze the influence of changes in ventricular preload and afterload, atrial and ventricular pacing on the coronary flow reserve (CFR). METHOD: Five open chest anesthetized dogs were studied in five sequential stages:baseline, saline solution volume loading (293.8+/-29.2 ml for 10 min), atrial and ventricular pacing (120, 140, and 160 bpm), and aortic clamp. Coronary blood flow (CBF) was measured with electro-magnetic flowmeter. CFR was defined as the ratio of hyperemic CBF (hCBF) to resting CBF (rCBF). Hyperemia was induced by IV adenosine infusion (1 mg/kg/min). RESULTS: 1)After volume loading wtih saline solution, CFR significantly decreased (p<0.05) because rCBF was increased while hCBF remained unchanged. 2)Atrial pacing produced increase in rCBF but did not change hCBF. Consequently CFR singificantly reduced when heart rate (HR) increased from sinus rhythm to 120, 140, and 160 bpm (p<0.01). 3)Ventricular pacing produced decrease in hCBF but did not change rCBF. Consequently CFR significantly reduced as HR increased from sinus rhythm to 120 (p<0.05) , 140 (p<0.01), and 160 (p<0.01) bpm. 4)After aortic clamp, CFR significantly decreased (p<0.01) because rCBF increased while hCBF remained unchanged. CONCLUSION: We found that CFR is dependent on the changes in volume loading, HR, and ventricular afterload that may commonly occur in clinical situations.

Clinical Investigation of P Wave Amplitude and Atrial Synchronous Ventricular Pacing in Different Body Position and Physical Activity with a Single-Pass Lead VDD Pacing

BACKGROUND: Single pass lead VDD pacing preserves atrioventricular synchrony with a single lead system which incorporates floating atrial electrodes. The objectives of this study were to measure whether different body postures and physical activities cause significant changes of the atrial electrogram amplitudes and to evaluate the effectiveness of its atrial sensing, ventricular sensing and pacing. METHOD: Prospective study was done in 7 patients with high degree AV block and normal sinus node function in whom a single lead VDD pacing system was implanted. The P wave amplitude was been measured in different condition during follow-up period. RESULTS: 1) During follow-up period, the P wave amplitude showed variation with changes in posture and respiration, but there was no consistent increase or decrease in amplitude. The lowest P wave amplitude was above the minimal atrial sensing value of 0.2 mV. 2) The percentage of atrial synchronous ventricular pacing recorded in Holter ECG and during Treadmill exercise test was more than 99%. 3) Atrial oversensing or VA cross sensing were not observed in any of the patients. CONCLUSIONS: Despite floating atrial electrode, the single pass lead VDD pacing maintains reliable atrial sensing and ventricular pacing in different body position and physical activity, so it may offer an excellent alternative in patients with high grade AV block and intact sinus node function.

Clinical Investigation of P Wave Amplitude and Atrial Synchronous Ventricular Pacing in Different Body Position and Physical Activity with a Single-Pass Lead VDD Pacing

BACKGROUND: Single pass lead VDD pacing preserves atrioventricular synchrony with a single lead system which incorporates floating atrial electrodes. The objectives of this study were to measure whether different body postures and physical activities cause significant changes of the atrial electrogram amplitudes and to evaluate the effectiveness of its atrial sensing, ventricular sensing and pacing. METHOD: Prospective study was done in 7 patients with high degree AV block and normal sinus node function in whom a single lead VDD pacing system was implanted. The P wave amplitude was been measured in different condition during follow-up period. RESULTS: 1) During follow-up period, the P wave amplitude showed variation with changes in posture and respiration, but there was no consistent increase or decrease in amplitude. The lowest P wave amplitude was above the minimal atrial sensing value of 0.2 mV. 2) The percentage of atrial synchronous ventricular pacing recorded in Holter ECG and during Treadmill exercise test was more than 99%. 3) Atrial oversensing or VA cross sensing were not observed in any of the patients. CONCLUSIONS: Despite floating atrial electrode, the single pass lead VDD pacing maintains reliable atrial sensing and ventricular pacing in different body position and physical activity, so it may offer an excellent alternative in patients with high grade AV block and intact sinus node function.

Hemodynamic Responses to Different Ventricular Pacing Sites and Pacing Rates in Dog

BACKGROUND: The hemodynamic effects of an episode of ventricular tachycardia (VT) may vary from mild decrease in blood pressure to sustained hypotension, collapse, and death. Little is known about the factors responsible for these diverse effects. Ventricular function, vasomotor tone, and tachycardia cycle length could be major determinants of variable hemodynamic responses to VT. The site of origin was found to be a factor affecting pulse pressure even in an isolated ventricular premature contraction. However, the role of origin site in hemodynamics of VT is not yet elucidated. The purposes of this study were to evaluate the effects of VT origin site and VT cycle length to their hemodynamic changes. And we also have assessed the role of cardiac autonomic receptor activation in hemodynamic recovery during and immediate after VT. METHODS: In 18 open chest dogs anesthetized with chloralose, bipolar ventricular pacing (VP) was performed using sutured epicardial electrodes at 3 different sites ; left ventricular apex (LVA), right ventricular outflow tract (RVOT), and right ventricular apex (RVA). At each site, VP was repeated for 60 seconds at 3 different rates; 1.75X, 2X, and 2.25X of baseline heart rate (BHR). Mean arterial pressure (MAP), mean left atrial pressure (MLAP) and mean pulmonary artery pressure (MPAP) were monitored during VP. deltaMAP was defined as the difference between the baseline MAP and lowest MAP during VP. deltaMLAP was defined as the difference between highest MLAP during VP and baseline MLAP. Cardiac vagal and beta-adrenoreceptor blockades were achieved by intravenous bolus administration of propranolol (1 mg/kg and then 1 mg/kg/hr) and atropine (0.5 mg/kg and then 0.5 mg/kg/hr). After cardiac autonomic blockade, VP was repeated at 2X of baseline heart rate for 60 seconds at each site. RESULTS: Baseline MAP, MLAP, and MPAP were 101+/-8.1 mmHg, 0.3+/-0.41 mmHg, and 10+/-2.4 mmHg, respectively. At the same pacing site of VP, MAP was decreased significantly with VP and deltaMAP was increased significantly as VP cycle length shortened (all P<0.001). At the same pacing cycle length of VP, deltaMAP was significantly greater at RVA or RVOT than LVA: LVA vs RVOT ; all P<0.001 at 3 different rates, LVA vs RVA ; P<0.05 (1.75X & 2X of BHR), P<0.001 (2.25X of BHR). But there was no significant difference in deltaMAP between RVA and RVOT. At the same pacing site of VP, MLAP and deltaMLAP were increased significantly as VP cycle length shortened (all P<0.01), but at the same cycle length of VP, there was no significant differences in deltaMLAP at 3 different VP sites. Ventricular pacing after autonomic blockade induced a greater increase in deltaMAP and deltaMLAP compared to controls (all P<0.01 at 3 pacing sites). And cardiac autonomic blockade also resulted in significant blunting of recovery of MAP during VP compared to controls. CONCLUSION: Above results showed that pacing cycle length plays a major role in determining the hemodynamic outcomes during ventricular pacing, and that the site of origin could be an independent factor of ventricular tachycardia hemodynamics. And also modulation of tone of the adrenergic nervous system is essentially required for the hemodynamic recovery during ventricular tachycardia.

Alterations in Myocardial Perfusion and Regional Wall Motion in Patients with Permanent Pacemaker

BACKGROUND: The effect of right ventricular pacing on myocardial perfusion and regional wall motion is not well known, although some studies have suggested that it may be adverse. We investigated the effects of right ventricular pacing on myocardial perfusion and regional wall motion in patients with permanent pacemakers. METHOD: Thirty patients receiving permanent pacemakers for complete heart block or sick sinus syndrome were included in this study. All the patients showed normal coronary angiograms. Myocardial scintigraphy and two-dimensional echocardiography were performed to assess myocardial perfusion and to evaluate regional wall motion and global function of the left ventricle (LV). RESULTS: 1) Mean age was 66.2+/-8.2 (41-84) years, and the male-to-female ratio was 1 : 1.7 (11 male, 19 female). Indications for permanent pacemaker implantation were complete atrioventricular (AV) block in 21 patients and sick sinus syndrome in 9. The selected pacing modes were VVI in 14 patients, DDD in 8, VDD in 6, and AAI in 2. LV ejection fraction estimated by 2-dimensional echocardiography was 62.7+/-5.8 (53-86)%. 2) Perfusion defects were noted in 26 (87%) patients including 25 (89%) out of 28 patients with ventricular pacing modes such as VVI, DDD, and VDD, and 1 (50%) out of 2 patients with AAI mode. Locations of perfusion defects were septal in 19 (63%) patients, inferior in 17 (57%), apical in 16 (53%), lateral in 3 (10%), and anterior in 2 (7%). Extent of maximal perfusion defects was 17.0+/-9.5 (0-44)%. 3) Regional wall motion abnormalities were noted mainly over the apical region of the LV in 26 (93%) of 28 patients with ventricular pacing. However, LV ejection fraction did not differ significantly before and early after implantation of the pacemaker (62.7+/-5.8% vs. 61.0+/-5.8%, p-0.313). CONCLUSIONS: Right ventricular apical pacing frequently caused myocardial perfusion defects and regional wall motion abnormalities. These might be due to abnormal ventricular activation and abnormal interventricular septal motion. The long-term effects of these abnormalities remain to be determined, and the pacing technique to minimize these adverse effects should be developed.