Pseudo-elevation of conduction system pacing threshold through parallel connection of an intracardiac electrogram recording system

Parallel connection of an electrophysiology recording system (EP system) to equipment for conduction system pacing (CSP) has been widely used for fine monitoring of intracardiac electrograms and pacing evaluation. We experienced a case showing unexpected pacing threshold exacerbation under specific conditions when the EP system was connected in parallel. We evaluated the underlying mechanism using an ex vivo model. An ex vivo pacing and intracardiac electrogram monitoring model was generated using an oscilloscope, pacing system analyzer (PSA), EP system, and simulated heart. The discrepancy between expected output at the PSA and the actual measured output value at the simulated heart was measured under various conditions and using various combinations of pacing equipment. Parallel connection of the EP system was associated with reduced electrical output from the PSA as recorded at the simulated heart. The unexpected adverse effects were particularly noticeable when using an RMC-5000 EP system with the pacing function on. The trouble is completely resolved by simply turning off the pacing function of the system. There is a possibility that the EP system might increase the pacing threshold in CSP when the PSA and EP system is are deployed in parallel. The issue may provoke pseudo failure of CSP due to the high pacing threshold. When the RMC-5000 is used for conduction system pacing in parallel with a PSA for the pacing test, the pacing function of RMC-5000 should be turned off.     

Hemodynamic monitoring and pacing with one catheter: a pilot study

Attempts to incorporate the monitoring of central pressures and pacing into one catheter have heretofore been unsuccessful. Recently, a new catheter for monitoring central hemodynamic pressures, which has a right ventricular port (Chandler pacing port), has been devised, which has been reported to allow for simultaneous acquisition of hemodynamic data and reliable pacemaker function as well. To assess the reliability of this catheter, we studied ten consecutive Swan-Ganz catheterizations utilizing this new catheter system. In all instances, hemodynamic monitoring was established without difficulty. In three instances, because of right heart enlargement, fluoroscopy was necessary to position the pacing probe at the right ventricular apex. In all ten instances, a threshold of less than 2.5 mV was obtained. Isolated PVCs and nonsustained ventricular tachycardia were common during insertion. After initial placement, the threshold for sensing and pacing was assessed every 6 hr. Malfunction occurred in three patients. In all, repositioning was accomplished without marked difficulty; in one it required fluoroscopy. In three instances, the Swan-Ganz pacing catheter system malfunctioned. These data are similar to data utilizing other modalities of temporary pacing and suggest that this catheter may be capable of providing hemodynamic monitoring and pacing from a single percutaneous procedure.     

Further observations on entrainment of atrial flutter in the dog

To determine whether the first postpacing interval after entrainment was affected by recording and pacing sites, overdrive atrial pacing was undertaken in 13 episodes of atrial flutter with a mean flutter cycle length (FCL) of 140 +/- 8 msec induced in seven dogs. Atrial flutter was induced by means of an anatomic obstacle. Seven recording sites, four in the right atrium and three in the left atrium, and three pacing sites, two in the right atrium and one in the left atrium, were selected. After entrainment from the right atrium at pacing cycle lengths that were 94% of the FCL, the first postpacing interval was not significantly different from the intrinsic FCL at each recording site, but it tended to be shorter than the FCL at the recording sites near pacing sites. For entrainment from the left atrium, the first postpacing interval was longer than the FCL at recording sites in the left atrium (p less than 0.001), but it was not different from the FCL at recording sites in the right atrium. These results are due to differences in placement of recording and pacing electrodes relative to the reentrant circuit. Also we observed that activation sequences involving three appropriately selected recording sites were always identical when paced from two different pacing sites at a single constant pacing cycle length. This new phenomenon may best be explained by postulating reentry as the mechanism for atrial flutter.     

Cardiac trans-esophageal pacing: significance of systemic damping of artifacts from stimulating impulses for ECG trace recordings recorded from a pacing trans-esophageal electrode. III

Utilization of diagnostic abilities of the cardiac trans-esophageal pacing is related to necessity of obtaining the readable and stable ecg tracing from a pacing electrode. For that reason to evaluate the value of an electronic artifact suppression circuit of a pacing impulse from oesophageal ecg recording authors compared quality of obtained recordings using a new method with a traditional one. Trans-esophageal cardiac pacemaker SP-5 made by OBR, Temed, Zabrze was used. Atria and ventricles were stimulated using a constant pacing cycle length and a single programmable impulse. In 58 persons ecg transoesophageal recordings were compared during atrial pacing, and in 45 during ventricular one. Quality of obtained ecg recordings was estimated using 4-degree scale of which first three degrees comprised recordings the esophageal pacing electrode by a traditional method were unfit for diagnostic interpretation. As opposed to the pacing electrode allowed to obtain recordings with quality of which was suitable for diagnostic interpretation in all patients. Obtained results indicate on, thanks to the new recording circuit, existence of conditions to substantial extension of diagnostic abilities of transoesophageal cardiac pacing.     

Progress in cardiac pacing

This review summarizes recent scientific developments in ambulatory monitoring and its legal implications in appropriately selected patients. It also considers how new cardiac pacing devices can be used in the clinical monitoring of atrial fibrillation, sleep apnea and, in transplant patients, heart failure and transplant rejection. In addition, the system of accreditation for cardiac pacing services in Spain is outlined, with a focus on process development and quality indicators. Finally, the scientific articles on cardiac pacing that made the greatest impact in 2007 are summarized.     

Vasovagal syncope: management with atrioventricular sequential pacing and beta-blockade

A case of vasovagal syncope in an otherwise healthy 74-year-old woman is described. Attempts to prevent symptoms with ventricular and atrioventricular sequential temporary pacing (documented by continuous monitoring of heart rate and intra-arterial recording of blood pressure during spontaneous episodes) proved inadequate. However, the addition of a beta-blocker to permanent DDD pacing was clinically successful in markedly diminishing symptoms. The mechanisms of action of this treatment modality is discussed.     

Clinical assessment of a new method for pacing pulse detection using a hybrid circuit in digital Holter monitoring

Holter monitoring is widely used for the detection of arrhythmia and ischemic episodes. Traditionally, analog amplitude-modulated Holter devices have been used for detecting arrhythmia, but they produce signal distortion due to contour effects and phase distortion caused by the tape recorders. A digital Holter device without these disadvantages has been developed and can reproduce clinically accurate electrocardiographic waveforms useful for assessment of arrhythmia and ST segments. However, their reliability is questionable when detecting pacing pulses in pacemaker patients. Because electrocardiographic signals are digitized based on sampling rate, pacing pulses are occasionally missed. Therefore, the FM-300 was developed, a new device for detecting pacing pulses on digital recordings that has both digital and analog circuits in one system and indicates pacing pulse timing with arrows. This device can automatically detect and recognize pacing pulses from various artifacts and pacing modalities, making it easy to identify pacing pulses on digitally recorded electrocardiograms. The FM-300 is useful in the diagnosis and assessment of pacemaker function and has improved the reliability of pulse detection in digital Holter monitoring.     

A new system for ambulatory pulmonary artery pressure recording.

OBJECTIVE--To develop a complete system for the measurement, recording, and analysis of ambulatory pulmonary artery pressure. DESIGN--The new system consists of a pulmonary artery catheter, an ambulatory recorder, and a desktop computer. Pulmonary artery pressure is measured by a micromanometer tipped catheter with an in vivo calibration system to allow correction for zero drift. This catheter is plugged into a small battery powered recorder. The recorder has two input channels, one for pressure and one for an event marker. The pressure wave is sampled 32 times/s, processed by an in built computer, compressed, and stored in semi-conductor memory. On completion of a recording, data is transferred from the ambulatory recorder through a serial data link to an Acorn Archimedes desktop computer on which further data processing, statistical analysis, graphics, and printouts can be obtained. RESULTS--The system has been used in 18 patients, with technically successful recording in 14, less than 15 minutes of data loss in three, and 12 hours of data loss in one. CONCLUSIONS--A new system for ambulatory pulmonary artery monitoring has been developed and used clinically with success. It may provide new perspectives on the pathophysiology of disease as it applies to everyday life.     

A new single catheter technique for simultaneous measurement of action potential duration and refractory period in vivo

In vivo correlations of action potential duration measured by a monophasic action potential catheter and effective refractory period measured by a separate pacing catheter have been poor, probably because of the known variability of both action potential duration and effective refractory period between different ventricular sites. In this study, a new quadripolar contact electrode catheter designed for simultaneous pacing and monophasic action potential recording at closely adjacent sites (2 mm separation between recording electrodes and pacing electrodes) was tested in five closed chest dogs and four patients. Dog studies: Pacing thresholds were extremely low, ranging from 0.02 to 0.25 mA (mean +/- SD 0.099 +/- 0.051, n = 36) and were stable over time (less than 20% increase during 1 h of continuous pacing). Because of the close proximity of pacing and recording electrodes, the pacing artifact nearly coincided with the monophasic action potential upstroke. Because of the low pacing threshold, however, pacing artifacts were small (33 +/- 17% of the monophasic action potential amplitude at twice diastolic threshold strength) and did not affect the duration or configuration of the simultaneously recorded monophasic action potential. The short stimulus response time and the undisturbed monophasic action potential signal fidelity during pacing allowed precise simultaneous measurements of action potential duration and effective refractory period at the same endocardial site.(ABSTRACT TRUNCATED AT 250 WORDS)     

Coronary pacing during percutaneous transluminal coronary angioplasty

To avoid venous puncture, a new concept for standby cardiac pacing during percutaneous transluminal coronary angioplasty (PTCA) and diagnostic cardiac catheterization was developed. It uses an arterial guidewire as a unipolar pacing electrode with the second electrode attached to the skin. The system was tested in 25 coronary arteries of 22 patients undergoing PTCA and in the left ventricles of 10 patients undergoing diagnostic cardiac catheterization. Coronary pacing via the guidewire used for directing the balloon catheter was possible in all patients and in 24 of the 25 coronary arteries attempted. Maximum duration of pacing was 8 min. Threshold currents ranged from 1 to 15 mA (mean 5.7). Left ventricular pacing via the same wires or standard wires used for introduction of diagnostic or guiding catheters was possible in all patients and was maintained for up to 10 min. Threshold currents ranged from 1 to 7 mA (mean 3.9). Neither method for pacing produced adverse effects during these short applications. The setup for coronary pacing also allowed recording of an intracoronary electrocardiogram during PTCA. The presented system provides backup for the rare event of sustained bradycardia during PTCA or diagnostic cardiac catheterization. If applied cautiously, it may safely and reliably replace the standby of a conventional transvenous pacing catheter.     

A fourth criterion for transient entrainment: the electrogram equivalent of progressive fusion

Prior data pertaining to transient entrainment and associated phenomena have been best explained by pacing capture of a reentrant circuit. On this basis, we hypothesized that rapid pacing from a single site of two different constant pacing rates could constantly capture an appropriately selected bipolar electrogram recording site from one direction with a constant stimulus-to-electrogram interval during pacing at one rate, yet be constantly captured from another direction with a different constant stimulus-to-electrogram interval when pacing at a different constant pacing rate. To test this hypothesis, we studied a group of patients, each with a representative tachycardia (ventricular tachycardia, circus-movement tachycardia involving an atrioventricular bypass pathway, atrial tachycardia, and atrial flutter). For each tachycardia, pacing was performed from a single site for at least two different constant rates faster than the spontaneous rate of the tachycardia. We observed in these patients that a local bipolar recording site was constantly captured from different directions at two different pacing rates without interrupting the tachycardia at pacing termination. The evidence that the same site was captured from a different direction at two different pacing rates was supported by demonstrating a change in conduction time to that site associated with a change in the bipolar electrogram morphology at that site when comparing pacing at each rate. The mean conduction time (stimulus-to-recording site electrogram interval) was 319 +/- 69 msec while pacing at a mean cycle length of 265 +/- 50 msec, yet only 81 +/- 38 msec while pacing at a second mean cycle length of 233 +/- 51 msec, a mean change in conduction time of 238 +/- 56 msec. Remarkably, the faster pacing rate resulted in a shorter conduction time. The fact that the same electrode recording site was activated from different directions without interruption of the spontaneous tachycardia at pacing termination is difficult to explain on any mechanistic basis other than reentry. Also, these changes in conduction time and electrogram morphology occurred in parallel with the demonstration of progressive fusion beats on the electrocardiogram, the latter being an established criterion for transient entrainment.(ABSTRACT TRUNCATED AT 400 WORDS)     

The Bravo™ pH capsule system

Limitations of existing pH recording methodology have been the impetus for the emergence of new technologies focused on improving ambulatory pH monitoring. The Bravo pH capsule system (Bravo, Medtronic, Shoreview, MN) is one of the recent advances that utilize a wireless system to improve patient compliance and extend the period of monitoring. These changes could potentially improve diagnostic accuracy along with patient acceptance. Given this fact, the following review will evaluate the potential benefits that wireless pH monitoring may have over conventional catheter based pH monitoring based on the available data. In addition, we will also focus on the technical aspects related to its safety, tolerability and diagnostic accuracy.     

河南省焦作市居民户碘盐监测质量评价

目的了解国家新的碘盐监测方案下发后,影响焦作市各县市区居民户碘盐监测的因素,评价碘盐监测系统以及监测质量。方法采取问卷了解专业人员对碘盐监测的认知情况,从抽样、现场、实验室和数据录入上报4个环节评价监测质量;盐碘含量均按照国标GB/T13025.7-1999中直接滴定法定量测定。结果问卷没有专业人员能够全部正确回答,问题回答正确率在96.30%-11.1%之间;＂缺乏经费支持＂和＂专业人员少＂等是影响居民户碘盐监测工作开展的因素;50%的县市区入户核实真实采样率达100%;80.00%的县市区抽样记录表填写完整、按时上报;录入上报正确率99.69%;碘盐监测软件存在系统不稳定、操作不方便等诸多问题和弊端;40%县市区实验室样品检验符合率在70%以上,检测技术较好、真实性较高。结论新的碘盐监测方案仍需要进行系统的培训;需要不断加强对碘盐监测的督导检查,理顺居民户监测的各个环节;加强专业防治队伍建设和经费投入,保证监测工作的可持续性;监测方案需要进一步修订,监测软件在人性化设计、使用功能方面需要进一步修改完善。     

Guidelines for pacemaker follow-up in Canada: a consensus statement of the Canadian Working Group on Cardiac Pacing

A survey on Canadian pacing practices conducted in 1997 revealed a widespread desire for national guidelines on pacemaker follow-up. The present guidelines for pacemaker follow-up are a consensus statement of the Canadian Working Group on Cardiac Pacing. Direct patient follow-up rather than transtelephonic monitoring is desirable. Patients should be assessed at a minimum of within 72 h of implantation, at two to 12 weeks and at six months following implantation, and annually thereafter. More frequent assessments may be required for some patients. This depends on associated cardiovascular problems and specific devices. A typical follow-up visit should include a targeted cardiovascular assessment, interrogation of the pacing system, review of telemetered data, assessment of the underlying rhythm, assessment of pacing and sensing thresholds, and appropriate reprogramming of pacing parameters to optimize device function and longevity.     

A new system for ambulatory pulmonary artery pressure recording

Objective—To develop a complete system for the measurement, recording, and analysis of ambulatory pulmonary artery pressure.Design—The new system consists of a pulmonary artery catheter, an ambulatory recorder, and a desktop computer. Pulmonary artery pressure is measured by a micromanometer tipped catheter with an in vivo calibration system to allow correction for zero drift. This catheter is plugged into a small battery powered recorder. The recorder has two input channels, one for pressure and one for an event marker. The pressure wave is sampled 32 times/s, processed by an in built computer, compressed, and stored in semiconductor memory. On completion of a recording, data is transferred from the ambulatory recorder through a serial data link to an Acorn Archimedes desktop computer on which further data processing, statistical analysis, graphics, and printouts can be obtained.Results—The system has been used in 18 patients, with technically successful recording in 14, less than 15 minutes of data loss in three, and 12 hours of data loss in one.Conclusions—A new system for ambulatory pulmonary artery monitoring has been developed and used clinically with success. It may provide new perspectives on the pathophysiology of disease as it applies to everyday life.     

心脏起搏系统阻抗体表检测方法的探讨

起搏阻抗反映了起搏器、起搏电极和心肌组织组成的起搏系统的连接状况。本文探讨了心脏起搏系统阻抗的体表检测方法,从体表起搏心电信号中分离并提取起搏脉冲波形,计算起搏系统阻抗。此方法已用于我们所研制的起搏心电监护系统,并在临床上进行了实测验证。将起搏系统阻抗和起搏心电图联系起来分析,有助于判断起搏系统故障的原因。     

Interesting electrophysiological phenomenon during positioning of the lead deep inside the septum

Left bundle branch pacing (LBBP) is a developing physiological pacing technique. Wu et al. proposed that direct LBB capture could be confirmed by recording retrograde His potential (Po_ReHis) and mapping of the left conduction system potential. The transventricular‐septal electrophysiological phenomena deserve further study. Here, we used a continuous uninterrupted pacing technique to confirm the LBB capture by dynamically observing changes in Po_ReHis and stimulus to left ventricular activation time.     

A feasible approach for direct his-bundle pacing using a new steerable catheter to facilitate precise lead placement

INTRODUCTION: Much clinical evidence has shown that right ventricular (RV) apical pacing is detrimental to left ventricular function. Preservation of the use of the His-Purkinje (H-P) system may be ideal in heart block that is restricted to the AV node, but may be of no benefit when H-P disease exists. AIM: To investigate the feasibility of direct His-bundle pacing (DHBP) using a new system consisting of a steerable catheter and a new 4.1 F screw-in lead. METHOD: Between May and December 2004, 26 patients (19 male, mean age: 77 +/- 5 years) with a standard pacemaker (PM) indication and preserved His-bundle conduction were enrolled and DHBP was attempted. RESULTS: DHBP was achieved in 24 patients (92%); two patients were paced in the His area, but the paced QRS morphology and duration were different from the native QRS. The mean time for lead positioning was 19 +/- 17 minutes, the mean fluoroscopy time was 11 +/- 8 minutes, and the total procedure time (skin-to-skin including positioning of a quadripolar diagnostic catheter for His recording) was 75 +/- 18 minutes. In DHBP pacing, the acute pacing threshold was 2.3 +/- 1.0 V at a pulse duration of 0.5 msec, and the sensed potentials were 2.9 +/- 2.0 mV. At a 3-month follow-up examination, the same QRS duration and morphology recorded on implantation were observed in all patients. The pacing threshold was 2.8 +/- 1.4 V, and sensed potentials were 2.5 +/- 1.8 mV; the sensing configuration was changed from bipolar to unipolar in 6 patients to resolve undersensing issues. No major complications were observed. CONCLUSIONS: This feasibility study shows that DHBP can be accomplished with a new system consisting of a steerable catheter and an active fixation lead in 92% of the patients in whom it was attempted.     

A new paradigm for physiologic ventricular pacing

Clinical trials in patients with pacemakers for sinus node dysfunction or atrioventricular block (AVB) and implantable cardioverter-defibrillators provide increasing evidence showing that desynchronization of ventricular electrical activation and contraction, induced by conventional right ventricular apex (RVA) pacing, is a serious threat for long-term cardiac morbidity and mortality. The risk of heart failure is increased even in hearts with initially normal pump function and in case of part-time ventricular pacing. These epidemiologic data fit with knowledge from decades of pathophysiological research, indicating that right ventricular (RV) pacing creates abnormal contraction, reduced pump function, hypertrophy, and ultrastructural abnormalities. This paper presents a new paradigm that aims to tailor ventricular pacing to the individual patient to achieve a way of pacing that is as physiologic as possible. In patients without AVB and no intraventricular conduction abnormalities, ventricular pacing should be avoided as much as possible, using atrial-based pacing. In patients with AVB, alternate single-site RV or left ventricular pacing or biventricular pacing may be superior to RVA pacing. Efforts to optimize the pacing mode or site should be greater in patients with a longer expected duration of pacing, poorer cardiac function, and larger mechanical asynchrony. Awareness of the problem of desynchronization should also lead to more regular monitoring of cardiac pump function and mechanical asynchrony in any patient with ventricular pacing.     

A new paradigm for physiologic ventricular pacing.

Clinical trials in patients with pacemakers for sinus node dysfunction or atrioventricular block (AVB) and implantable cardioverter-defibrillators provide increasing evidence showing that desynchronization of ventricular electrical activation and contraction, induced by conventional right ventricular apex (RVA) pacing, is a serious threat for long-term cardiac morbidity and mortality. The risk of heart failure is increased even in hearts with initially normal pump function and in case of part-time ventricular pacing. These epidemiologic data fit with knowledge from decades of pathophysiological research, indicating that right ventricular (RV) pacing creates abnormal contraction, reduced pump function, hypertrophy, and ultrastructural abnormalities. This paper presents a new paradigm that aims to tailor ventricular pacing to the individual patient to achieve a way of pacing that is as physiologic as possible. In patients without AVB and no intraventricular conduction abnormalities, ventricular pacing should be avoided as much as possible, using atrial-based pacing. In patients with AVB, alternate single-site RV or left ventricular pacing or biventricular pacing may be superior to RVA pacing. Efforts to optimize the pacing mode or site should be greater in patients with a longer expected duration of pacing, poorer cardiac function, and larger mechanical asynchrony. Awareness of the problem of desynchronization should also lead to more regular monitoring of cardiac pump function and mechanical asynchrony in any patient with ventricular pacing.