Ventricular pacing threshold variations in the young

Ventricular Capture Management (VCM) is a Medtronic Kappa pacemakers (PM) feature that automatically measures pacing threshold through detection of the evoked response after a pacing stimulus. The aim of this study was to evaluate the range of variation of ventricular pacing threshold in pediatric patients with endocardial and epicardial pacing leads. Thirty-one patients (median age 6.5 years) were implanted with a Kappa 901 PM for atrioventricular block or sinus node dysfunction. Congenital heart defects (CHD) were present in 58% of patients. Ventricular leads were epicardial in 52% of patients. VCM was programmed to automatically measure threshold every 2 hours. In a median follow-up of 12 months, 27,110 threshold measurements, 72% of which were successful, have been taken in 94% of patients. Measurement success was 99% in the endocardial leads group (age at implantation 12 +/- 6 years) and 31% in epicardial leads (age 4 +/- 5 years) (P < 0.05). Main reasons for unsuccessful measurements were high heart rate and, in a patient with an endocardial lead, competition with intrinsic rhythm. Undersensing or oversensing of the evoked responses was not detected. In all successful VCM measurements, epicardial pacing and CHD contributed to stability of thresholds (multivariate analysis). Pacing threshold showed specific circadian patterns: higher thresholds were found between 00.00 and 06.00 a.m., but the variation was low, 0.03 +/- 0.01 V. In conclusion, children and young patients show stable ventricular thresholds, especially in presence of CHD, and epicardial leads are at least as stable as endocardial leads. Ventricular pacing threshold showed a circadian variability similar to that described in adults, that does not seem to influence VCM functioning and PM programming.     

右心室起搏比例和不同部位起搏对老年患者心功能的影响

目的：探讨右心室起搏比例和不同部位起搏对老年患者心功能的影响。方法回顾性分析92例植入体内埋藏式双腔心脏起搏器（DDD）的老年患者的临床资料,根据术后1年起搏器程控仪获取的右心室起搏比例,将右心室起搏比例≥50%患者纳入A组,右心室起搏比例＜50%患者纳入B组,比较两组术前和术后1年彩色多普勒心脏超声的变化。同时,将A组分为右室心尖部（RVA）起搏者和右室间隔部（RVS）起搏者进行亚组分析。结果 A组术后1年左房内径（LAD）较术前增大,左室射血分数（LVEF）较术前和B组降低,差异均有统计学意义（t分别=2.43、4.20、6.37,P均＜0.05）;B组术后1年LAD、左室舒张末期内径（LVEDD）、LVEF和术前比较,差异均无统计学意义（t分别=0.73、0.78、1.16,P均＞0.05）。亚组分析结果显示两亚组术前LAD、LVEDD、LVEF比较,差异均无统计学意义（t分别=0.77、0.35、1.32,P均＞0.05）,两组术后LVEDD、LVEF比较,差异均有统计学意义（t分别=2.86、4.62,P均＜0.05）,RVS组术后LAD、LVEDD、LVEF与术前比较,差异均无统计学意义（t分别=1.45、0.14、0.48,P均＞0.05）;而RVA组术后LAD、LVEDD均较术前明显扩大,LVEF较术前明显下降（t分别=2.20、3.13、4.31,P均＜0.05）。结论老年患者中右室间隔部起搏与右室心尖部起搏相比更有利于保持患者心功能的稳定,但同时应尽量减少不必要的右心室起搏。     

Intra- and interatrial conduction delay: implications for cardiac pacing

Atrial conduction disorders are frequent in elderly subjects and/or those with structural heart diseases, mainly mitral valve disease, hyperthrophic cardiomyopathies, and hypertension. The resultant electrophysiological and electromechanical abnormalities are associated with a higher risk of paroxysmal or persistent atrial tachyarrhythmias, either atrial fibrillation, typical or atypical flutter or other forms of atrial tachycardias. Such an association is not fortuitous because intra- and interatrial conduction abnormalities delays disrupt (spatial and temporal dispersion) electrical activation, thus promoting the initiation and perpetuation of reentrant circuits. Preventive therapeutic interventions induce variable, sometimes paradoxical effects as with the proarrhythmic effect of class I antiarrhythmic drugs. Similarly, atrial pacing may promote proarrhythmias or an antiarrhythmic effect according to the pacing site(s) and mode. Multisite atrial pacing was conceived to correct, as much as possible, abnormal activation induced by spontaneous intra- or interatrial conduction disorders or by single site atrial pacing, which are situations responsible for commonly refractory arrhythmias. Atrial electrical resynchronization can also be used to correct mechanical abnormalities like left heart AV dyssynchrony resulting from intraatrial conduction delays.     

Emergency noninvasive external cardiac pacing

Thirty-seven critical emergency department patients underwent attempts at external cardiac pacing over an 11-month period. Indications for pacing were asystole in 16, complete heart block (CHB) in 4, sinus bradycardia in 2, nodal bradycardia in 1, atrial fibrillation with bradycardia in 2, electromechanical dissociation in 1, idioventricular rhythm (IVR) in 10, and torsades de pointes in 1. Eight patients were successfully paced with improvement in their condition. Two were in asystole, two in CHB, three in sinus rhythm or atrial fibrillation with bradycardia, and one in idioventricular rhythm. Mean systolic blood pressure rise with pacing was 95 +/- 50 mm Hg. Six of these patients were ultimately discharged from the hospital. One asystolic patient survived to discharge. Other survivors presented with either CHB or bradycardia. Of the 29 patients who did not respond to pacing, 5 survived to hospital discharge. Surviving nonresponder presenting rhythms were CHB in one patient, sinus or nodal bradycardia in two, IVR in one, and torsades de pointes in one. External cardiac pacemaking appears to be effective in hemodynamically significant bradycardia. It does not appear to be effective in most instances of asystole or IVR resulting from prolonged cardiac arrest. When applied to patients with a responsive myocardium, it may result in significant hemodynamic improvement and may be lifesaving.     

Upgrade of single chamber pacemakers with transvenous leads to dual chamber pacemakers in pediatric and young adult patients

Children with single chamber pacemakers, in adolescence and young adulthood, may be upgraded to dual chamber systems, but there are no published data about indications, timing, and complications. Upgrading was attempted in 18 patients with transvenous pacing leads. A retrospective analysis of all collected data was performed. At initial pacemaker implantation (mean +/- SD, 9.3 +/- 4.1 years), the pacing mode was VVIR (n = 13 patients) and AAI/AAIR (n = 5 patients). After 72 +/- 41 months of follow-up, at the age of 15.5 +/- 5.2 years, upgrade was undertaken because of the patient's age at elective generator replacement (n = 3 patients), ventricular dysfunction (n = 7), syncope/presyncope (n = 3) in patients with VVIR pacing, atrioventricular block (n = 2), and/or drug refractory supraventricular tachyarrhythmias (n = 4) in patients with atrial pacing. In comparison with single chamber pacemaker implantations, the average procedural time and the average fluoroscopy time were not significantly longer. All suitable preexisting leads were incorporated in the new pacing system. Leads were inserted via the ipsilateral subclavian vein in 16 patients. Venous occlusion was found in two patients: in the first the procedure was not performed; in the second, the contralateral vein was used and the old lead was abandoned. There were no procedural complications. During a follow-up of 14 +/- 11 months, ventricular dysfunction worsened in five of seven patients; other patients benefitted symptomatically. In conclusion, pacemaker upgrade is technically challenging but feasible and safe and may be beneficial for some patients.     

Pathological aspects of transcutaneous cardiac pacing

Although electrical energy has the potential to produce myocardial injury, the risk of tissue damage from transcutaneous cardiac pacing is largely unknown. This study reports the anatomical findings of a canine transcutaneous stimulation study. Ten dogs had 100-mA, 20-msec (pulse duration), transcutaneous impulses delivered across the thorax for 30 minutes at a rate of 80 stimuli per minute. Seventy-two hours later the animals were sacrificed, and the heart, lungs, and tissues of the chest wall were examined for pathological changes. Gross and microscopic lesions consistent with electrically induced myocardial damage were found in all hearts examined. These lesions included myocardial pallor and focal myofibril coagulation necrosis in the right ventricular outflow tract and perivascular microinfarcts in the posterior left ventricular myocardium. These lesions were not extensive; less than 5% of the right ventricular free wall and less than 1% of the left ventricular posterior wall were involved. Lesions of this extent would not be expected to cause clinically detectable changes in cardiovascular status. Short-term use of transcutaneous pacing appears to be safe. Determination of the potential for clinically significant injury with long-term use requires further study.     

右心室流入道间隔部和右心室心尖部起搏神经内分泌激素和心功能的变化

目的探讨右心室流入道间隔部(RVIS)和右心室心尖部(RVA)起搏治疗缓慢性心律失常神经内分泌激素和心功能的变化。方法房室全能型起搏器(DDD)治疗患者106例,男86例,女20例,年龄45～86岁,平均(76.4±9.5)岁,随机分为右心室流入道间隔部起搏组(RVIS起搏组)56例,右心室心尖部起搏组(RVA起搏组)50例。两组心房电极均植入右心耳梳状肌内,RVIS起搏组心室电极植入右心室流入道间隔部、RVA起搏组心室电极植入右心室心尖部。分别观察两组在起搏器植入时、起搏3个月和6个月不同时期,血浆肾素活性(PRA)、血管紧张素Ⅱ(AngⅡ)、醛固酮(ALD)、心钠肽(BNP)和去甲肾上腺素(NE)等神经内分泌激素的含量;应用彩色多普勒超声心动图测定:心排血量(CO)、每搏输出量(SV)、射血分数(EF)和左心室舒张末内径(LVDd)。结果 RVA起搏组治疗后,血浆PRA、AngⅡ、ALD、BNP和NE含量增加,而RVIS起搏组则明显下降;RVIS起搏组心功能改善明显:CO、SV和EF值明显增加,LVDd值缩小,RVA起搏组SV、EF值下降,LVDd增加,CO虽然有所增加,但不如RVIS起搏组明显,差异均有统计学意义(P<0.05)。结论 RVIS起搏优于RVA起搏,可明显改善心功能,纠正神经内分泌激素失调,值得临床推广。     

速度向量成像技术评价DDD起搏前后左心室心肌应变与位移

目的探讨速度向量成像(VVI)技术分析DDD起搏前后左心室心肌运动应变和位移变化规律以及该技术的应用价值。方法 23例DDD起搏患者手术前后均采用VVI技术检测心室各节段心肌收缩期纵向运动应变和位移,并比较其在手术前后的差异。结果 23例DDD起搏患者术后侧壁、后间隔、前壁以及下壁多个节段应变和位移显著低于术前,基底段与中间段术后平均应变和位移显著低于术前(P均0.01);整个左心室术后应变和位移亦较术前明显降低(P均0.05)。术前、术后左心室各节段位移从基底段、中间段到心尖段呈依次递减,而应变无这种递减规律。结论 (1)DDD起搏前后左心室心肌运动应变和位移明显不同,术后较术前明显降低;(2)VVI技术能准确地定量评价DDD起搏前后左心室心肌运动应变和位移。     

三维斑点追踪成像技术评估右心双腔间隔起搏对左心室功能的影响

目的 应用三维斑点追踪成像（3D-STI）评估右心双腔间隔起搏对左心室功能的影响。方法 对42例右心双腔间隔起搏患者（起搏器组）和37名健康志愿者（对照组）行3D-STI检查,于心尖四腔切面图像获得左心室总体纵向峰值应变（GLS）、总体周向峰值应变（GCS）、总体径向峰值应变（GRS）、总体面积峰值应变（GAS）及左心室总体拧转（GTw）和左心室整体扭转（GTs）值。比较2组间三维应变参数,并分析GTw、GTs与GLS、GCS、GAS及GRS的相关性。结果 与对照组相比,起搏器组左心室GLS、GCS、GAS、GRS及GTs均明显减低（P均<0.05）;2组间GTw差异无统计学意义（P>0.05）。对照组GTs与GCS和GRS呈正相关（r=0.45、0.40;P均<0.05）,与GAS、GLS无相关性（P均>0.05）;GTw与GLS、GCS、GAS、GRS均无相关（P均>0.05）。起搏器组GTw、GTs与GLS、GCS、GAS、GRS均无相关（P均>0.05）。结论 右心双腔间隔起搏可损害左心室心肌形变能力,致左心室整体收缩功能隐匿性减低。     

Alternate site atrial pacing in the young: conventional echocardiography and tissue Doppler analysis of the effects on atrial function and ventricular filling

BACKGROUND: Although the right atrial appendage (RAA) is typically used for atrial pacing lead implant, recent studies have shown benefits of alternate site atrial pacing (ASAP) in the elderly. However, comparable studies in the young are lacking. METHODS: To investigate effects of ASAP on cardiac function and atrioventricular mechanical interactions in the young, 26 subjects (ages 10 to 23 years) with normal cardiac anatomy, function, and atrioventricular node conduction underwent echocardiography during electrophysiology studies while in sinus rhythm (NSR), and with temporary pacing from high right atrium (HRA), RAA, mid septal right atrium approximating Bachmann's bundle (BB), and left atrium (LA) via the distal coronary sinus (CS). After a paced steady state of 10 minutes, left atrial total and systolic ejection fractions, color-guided mitral inflow, and annular tissue Doppler indices were obtained. Left ventricular ejection fraction and myocardial performance indexes (MPI) were calculated. RESULTS: The total and systolic LA ejection fractions were higher during the NSR compared to all ASAP. Mitral inflow velocities changed significantly with ASAP. The passive/active ventricular filling ratio (E/A) deteriorated from NSR to HRA to BB to CS. There were significant changes in late diastolic tissue Doppler velocities during ASAP compared to NSR. The MPI during ASAP differed from those during the NSR. HRA and Bachmann bundle pacing provided better MPIs than RAA or CS pacing. CONCLUSION: The location of atrial pacing leads has an acute impact on cardiac function and atrioventricular mechanical interaction. Pacing close to sinus node location may be beneficial in the young.     

Electrocardiographic patterns during: pacing the great cardiac and middle cardiac veins

BACKGROUND: The electrocardiogram (ECG) patterns during pacing from the great cardiac vein (GCV) and the middle cardiac vein (MCV) are not well known. METHODS: We recorded 12-lead ECGs during GCV and MCV pacing in 26 patients undergoing implantation of a cardiac resynchronization device. The left ventricular (LV) lead was passed down the GCV (n = 19) or MCV (n = 7) prior to moving it to a lateral or posterolateral vein for permanent implantation. RESULTS AND CONCLUSIONS: Pacing within the GCV resulted in a left bundle branch block (LBBB) morphology with no or minimal R-wave in V(1) in 14 patients and a right bundle branch block (RBBB) pattern (R > S in lead V(1)) in four patients. In one patient, lead V1 during GCV pacing was isoelectric (R = S). A more distal pacing site in the GCV yielded a LBBB pattern in all the patients. All leads placed in the MCV resulted in a LBBB configuration. An ECG pattern with a RBBB pattern was invariably recorded during LV pacing in 125 consecutive outpatients with biventricular pacemakers and LV leads in the posterolatral and lateral coronary veins. Knowledge of the ECG patterns from various pacing sites in the coronary venous system may be helpful for troubleshooting all types of pacing systems, especially those where the coronary venous pacing site is unintentional.     

The acute effect of cardiac pacing mode on endothelial vasodilation: prospective, double-blind, cross-over, comparative clinical study

Background: Compared to atrioventricular sequential pacing, ventricular demand pacing is known to have somewhat more deleterious hemodynamic effects, which probably arise from increased sympathetic tonus and inappropriate baroreceptor activation. Endothelial function is affected by various local and systemic factors including baroreceptor activity. The aim of this study was to explore whether cardiac pacing would have any effect on endothelial functions.
Methods: Twelve patients (six male, mean age: 75 ± 9 years) with previously implanted DDD or VDD cardiac pacemakers were included. All patients had stable atrial rhythms during the study. Patients were randomized to either atrial-based pacing mode (VDD or DDD) or ventricular demand pacing mode (VVI) first, and then cross-over was performed with the other pacing mode. Endothelial function was assessed by brachial artery ultrasonography. Basal diameter of the brachial artery, and both flow-mediated dilation (FMD) and endothelium-independent vasodilation with nitroglycerin were measured 1 hour after each pacing mode.
Results: Compared to atrial-based pacing mode, ventricular demand pacing was associated with a significantly worse FMD both as absolute and percentage values (0.17 ± 0.09 mm vs 0.28 ± 0.11 mm, P = 0.015 and 4.84 ± 2.37 % vs 7.00 ± 2.88 %, P = 0.028, respectively). However, there was no significant difference in nitroglycerin-mediated vasodilation values between the two pacing sessions.
Conclusions: Acute ventricular demand pacing (VVI pacing) is clearly associated with attenuation of FMD in patients with atrial-based pacing systems. The attenuation of endothelial vasodilation might have a role in hemodynamic and clinical deterioration in patients with VVI pacemakers.     

Development of atrial fibrillation in patients with atrioventricular block after atrioventricular synchronized pacing

Many studies have evidenced an increased incidence of AF in patients receiving single chamber ventricular pacing (VVI) when compared with those undergoing an atrial-based system (AAI or DDD). However, the difference in incidence of AF between two atrial-based systems (VDD, DDD) in patients with AV block was still controversial. This study was conducted to compare the development of AF between different modes of pacemakers (VDD and DDD) in patients with symptomatic AV block. A retrospective review was conducted of the detailed records of all consecutive patients who received permanent pacemakers due to symptomatic bradycardia from March 1995 to March 2000. The occurrence of AF was documented when there was presence of AF in the free-run or 12-lead ECG, any ECG strips, or persistent AF on 24-hour Holter ECG during the follow-up. The study included 152 patients (44 women, 108 men; mean age 73). The patients were divided into two groups: VDD (n = 100) and DDD (n = 52). The mean follow-up was 48.9 +/- 22.9 months. The incidence of AF was 7.9%. A higher incidence of AF was noted in the DDD group (15.4%) when compared with the VDD group (4.0%, P = 0.023). The incidence of development of AF in patients with AV block was higher in those receiving DDD cardiac pacing when compared with those who received the VDD system. The authors suggest that VDD pacing may be a better choice than the DDD system for patients with AV block, but without clinical evidence of sinus node dysfunction, and if an atrial lead is required, it should be placed close to the Bachmann's bundle.     

Transthoracic pacing in cardiac asystole

A total of 139 patients had transthoracic pacemakers introduced via a subxiphoid approach for asystole during advanced CPR in the emergency department of a large urban teaching hospital over a calendar year. Two groups were examined retrospectively, A) 34 patients who presented asystolic, and B) 99 patients who presented with ventricular fibrillation that became asystole. Age, sex, and etiologies for cardiac arrest were similar in both groups; there were no survivors. The mean duration of asystole before pacemaker insertion was 4 min (group A) to 7 min (group B). Temporary electrical capture was obtained in six patients from group B, but electrical-mechanical association could not be achieved in any of these patients.     

双腔起搏器房室间期自动搜索功能对右心室起搏比例影响的临床研究

目的比较植入双腔起搏器患者房室（AV）间期自动搜索功能（Search AV）打开与固定长AV间期起搏,对右心室起搏比例的影响。方法入选60例病态窦房结综合征或间歇性Ⅱ度或Ⅲ度AV传导阻滞患者,均安装双腔起搏器。程控首先关闭Search AV功能,固定长AV间期（起搏房室间期220ms,感知房室间期200ms）起搏3个月,后程控打开Search AV 3个月,自身对照,比较其心房起搏比例、心室起搏比例及高频心房事件次数。再根据患者是否1：1房室传导分为2个亚组,自身对照分别比较其心房起搏比例、心室起搏比例及高频心房时间次数。结果58倒患者完成随访,固定长AV间期起搏时比Search AV（＋）自动搜索功能打开时的心室起搏比例、高频心房事件次数都高,分别为（70．5±12．4）％vs（22．4±8．3）％,（86±16）次VS（31±11）次（P=0．007,P=0．006）;而心房起搏比例二者差异无统计学意义。在1：1房室传导组（33例）及非1：1房室传导组（25例）两亚组比较中,均得出相同结果。结论Search AV功能可以减少不必要的右心室起搏,减少高频心房事件。     

European clinical experience with a dual chamber single pass sensing and pacing defibrillation lead

Dual chamber ICDs are increasingly implanted nowadays, mainly to improve discrimination between supraventricular and ventricular arrhythmias but also to maintain AV synchrony in patients with bradycardia. The aim of this study was to investigate a new single pass right ventricular defibrillation lead capable of true bipolar sensing and pacing in the right atrium and integrated bipolar sensing and pacing in the right ventricle. The performance of the lead was evaluated in 57 patients (age 61 +/- 12 years; New York Heart Association 1.9 +/- 0.6, left ventricular ejection fraction 0.38 +/- 0.15) at implant, at prehospital discharge, and during a 1-year follow-up. Sensing and pacing behavior of the lead was evaluated in six different body positions. In four patients, no stable position of the atrial electrode could intraoperatively be found. The intraoperative atrial sensing was 2.3 +/- 1.6 mV and the atrial pacing threshold 0.8 +/- 0.5 V at 0.5 ms. At follow-up, the atrial sensing ranged from 1.5 mV to 2.2 mV and the atrial pacing threshold product from 0.8 to 1.7 V/ms. In 11 patients, an intermittent atrial sensing problem and in 24 patients an atrial pacing dysfunction were observed in at least one body position. In 565 episodes, a sensitivity of 100% and a specificity of 96.5% were found for ventricular arrhythmias. In conclusion, this single pass defibrillation lead performed well as a VDD lead and for dual chamber arrhythmia discrimination. However, loss of atrial capture in 45% of patients preclude its use in patients depending on atrial pacing.     

Comparison of the efficacy of two surgical alternatives for cardiac resynchronization therapy: trans-apical versus epicardial left ventricular pacing

Background: Epicardial pacing lead implantation is the currently preferred surgical alternative for left ventricular (LV) lead placement. For endocardial LV pacing, we developed a fundamentally new surgical method. The trans‐apical lead implantation is a minimally invasive technique that provides access to any LV segments. The aim of this prospective randomized study was to compare the outcome of patients undergoing either trans‐apical endocardial or epicardial LV pacing. Methods: In group I, 11 end‐stage heart failure (HF) patients (mean age 59.7 ± 7.9 years) underwent trans‐apical LV lead implantation. Epicardial LV leads were implanted in 12 end‐stage HF patients (group II; mean age 62.8 ± 7.3 years). Medical therapy was optimized in all patients. The following parameters were compared during an 18‐month follow‐up period: LV ejection fraction (LVEF), LV end‐diastolic diameter (LVEDD), LV end‐systolic diameter, and New York Heart Association (NYHA) functional class. Results: Nine out of 11 patients responded favorably to the treatment in group I (LVEF 39.7 ± 12.5 vs 26.0 ± 7.8%, P < 0.01; LVEDD 70.4 ± 13.6 mm vs 73.7 ± 10.5 mm, P = 0.002; NYHA class 2.2 ± 0.4 vs 3.5 ± 0.4, P < 0.01) and eight out of 12 in group II (LVEF 31.5 ± 11.5 vs 26.4 ± 8.9%, P = < 0.001; NYHA class 2.7 ± 0.4 vs 3.6 ± 0.4, P < 0.05). During the follow‐up period, one patient died in group I and three in group II. There was one intraoperative LV lead dislocation in group I and one early postoperative dislocation in each group. None of the patients developed thromboembolic complications. Conclusions: Our data suggest that trans‐apical endocardial LV lead implantation is an alternative to epicardial LV pacing. PACE 2012; 35:124–130)     

Long-term complication rates in ventricular, single lead VDD, and dual chamber pacing

A higher incidence of pacemaker related complications has been reported in DDD systems as compared to VVI devices. The implantation of single lead VDD pacemakers might reduce the complication rate of physiological pacing in patients with AV block. In a retrospective study, the data records of 1,214 consecutive patients with pacemaker implantation for AV block between 1990 and 2001 (VVI 36.5%, DDD 32.9%, VDD 30.6%) were analyzed. Complications requiring surgical interventions were compared during a follow-up period of 64 +/- 31 months. Operation and fluoroscopic times were longer in DDD pacemaker implantation compared to VDD and VVI devices:58 +/- 23 versus 39 +/- 10 and 37 +/- 13 minutes (P<0.001), 9.2 +/- 5.2 versus 4.1 +/- 2.4 and 3.5 +/- 2.3 minutes, respectively. Differences remained significant after correction for covariates. In a multivariate Cox regression model, the corrected complication hazard of a DDD pacemaker implantation was increased by 3.9 (1.4-11.3) compared to VVI and increased by 2.3 (1.1-4.5) compared to VDD pacing. Higher complication rates in DDD pacing were mainly due to a higher incidence of early reoperation for atrial lead dysfunction, whereas the long-term complication rate was not different from VDD or VVI pacing. Early and long-term complication rates did not differ between VDD and VVI pacemaker systems. In conclusion, operation time and complication rates of physiological pacing are reduced by VDD pacemaker implantation achieving values comparable to VVI pacing. Thus, single lead VDD pacing can be recommended for patients with AV block.     

经左锁骨下静脉插入导管床边紧急心脏临时起搏25例

目的：报告经左锁骨下静脉穿刺插入带引导钢丝的电极导管行右心室起搏２５例经验。方法：经左锁骨下静脉插入导管，在心腔内心电图指引下判断电极到达右心室，将脉宽调至０．５ｍｓ测起搏阈值；将电压调至５Ｖ，频率６０～７０次／分恒定起搏。结果：开始穿刺至起搏成功３～８分钟（平均５．９分钟），起搏时间３～１６天。其中９例术后Ｘ线摄片、５例因植入永久心脏起搏器透视证实电极位于右心室心尖部。起搏期间１例伴急性左心衰竭，经调整电极后起搏良好，未再脱位；１例３束支传导阻滞合并室性逸搏心律患者，术后出现精神症状，经予脑细胞活化剂及多虑平３天后恢复正常；全部患者心电图均为完全性左束支阻滞图形，未出现心脏穿孔、血气胸等并发症，经治疗均痊愈出院。结论：本法创伤小，起搏电流低，患者无痛苦，能较长时间保持有效起搏；无需Ｘ线引导，易于推广急救应用     

Evaluation of the early hemodynamic changes in carotid arteries during ventricular and dual chamber pacing

In spite of a wide choice of pacemakers, there are some problems in making more rational clinical decisions for individual patients since mode selection and programming is usually performed on the basis of a clinical hunch. The aim of this study was to measure the differences in carotid flow in patients with a pacemaker programmed in the dual chamber and in the single chamber pacing modes. Sixty patients with implanted bipolar DDD pacemakers were enrolled in this study. Blood peak systolic velocity (PSV) and end-diastolic velocity (EDV), cross-sectional area, resistive index (RI), and pulsatility index (PI) were measured in the common (CCA), internal (ICA), and external (ECA) carotid arteries before pacemaker implantation and after dual chamber and ventricular pacing at 60 beats/min. PSVs in the left CCA (79.3 +/- 24.9 cm/s) and right CCA (84.1 +/- 18.7) were shown to significantly decrease after VVI pacing (60.1 +/- 16.6 and 62.1 +/- 20.0, respectively). There was also a similar significant decrease in PSV in the left and right ICAs and ECAs. Besides PSV, RI, and PI in the left and right CCAs, ICAs, and ECAs significantly decreased after VVI pacing. There was no similar decrease after DDD pacing. Cross-sectional area and flow volume in the CCA, ICA, and ECA were similar after DDD and VVI pacing and before pacemaker implantation suggesting that cardiac output was similar when the measurements were recorded. Carotid artery PSVs, pulsatility, and RIs were found to be significantly decreased during VVI pacing compared to baseline and DDD pacing. The greater incidence of adverse cerebral outcomes in patients with VVI rather than DDD pacing may be partly due to decreased carotid PSVs.