Influence of the pacing rate on the atrioventricular conduction time during aerobic and anaerobic exercise: basic concepts for a dromotropically controlled rate responsive pacemaker

The dromotropic pacemaker concept needs a rate responsive algorithm in which the pacing rate is controlled by the atrioventricular conduction time (AVCT). To develop basic concepts for such a rate responsive algorithm, the influence of the pacing rate on the AVCT was investigated. Seven patients (62 +/- 7.8 years) with sick sinus syndrome and intact atrioventricular conduction underwent two cardiopulmonary exercise tests (CPX) on a treadmill. According to the determination of the anaerobic threshold (AT) and the patients maximum capacity in the first incremental CPX the work rate for two exercise levels below and above the AT were chosen for the second constant workload CPX. The calculation of the optimal pacing rate (HRopt) was based on the oxygen uptake (VO2) during exercise after reaching steady-state conditions. According to the increase of the VO2 from 14.8 +/- 2.3 mL/min per kilogram during aerobic work (38.3 +/- 16.0 W) to 19.4 +/- 4.7 mL/min per kilogram during anaerobic work (80.6 +/- 32.3 W), the HRopt was calculated to be 98.6 +/- 6.9 beats/min and 116.4 +/- 4.7 beats/min. Starting from HRopt, the pacing rate was increased (overpacing) and decreased (underpacing) by about 5 beats/min every minute. At optimal pacing rate the AVCT decreased significantly from 233.0 +/- 30.5 ms during aerobic work and to 226.4 +/- 27.3 ms during anaerobic work (P < 0.05). Whereas overpacing induced a significant prolongation of the AVCT during aerobic work (4.17 +/- 1.78 ms per 10 beats/min) and anaerobic work (3.84 +/- 1.60 ms per 10 beats/min), underpacing yielded a significant shortening of the AVCT by about 4.49 +/- 2.64 ms per 10 beats/min during aerobic work and 4.75 +/- 1.87 ms per 10 beats/min during anaerobic work (P < 0.01). The slopes of the regression lines of the relationship between AVCT and pacing rate were not significantly. different. Based on the reciprocal relationship of heart rate (HR) and AVCT, basic concepts may be established for a dromotropic rate responsive algorithm.     

Documented Symptomatic Bradycardia and Symptom Relief in Patients Receiving Permanent Pacemakers: An Evaluation of the Joint ACC/AHA Pacing Guidelines

Recently, emphasis has been placed on documenting symptomatic bradycardia (DSB) before pacemaker placement can be justified in some patients. This study was designed to judge whether DSB improved the likelihood of symptom relief after pacing in 93 patients who had symptoms prior to pacing. Patients with complete heart block (Group A) had excellent symptomatic relief with or without pre-pacemaker DSB (100% vs 94%, P = NS). Patients with other diagnoses (Group B) also had a high incidence of symptomatic relief after pacing, regardless of whether or not DSB was present pre-implant (28/30 (93%) vs 23/28 (82%) P = NS). When evaluated as a test to predict the response to pacing for Group B patients, spontaneously occurring symptomatic bradycardia was neither highly sensitive (55%) nor highly specific (71%). Moreover, while the ability of a positive test to predict resolution of symptoms after pacing was high (93%), the ability of a negative test to predict a poor outcome after pacing was low (18%). The absence of DSB should not rule out permanent pacing for symptomatic patients in any diagnostic group. Future pacing guidelines should be revised to offer additional detail regarding the influence of symptoms, extent of asymptomatic bradycardia, and results of provocative tests in determining which implants should be classified as definitely indicated.     

AV block and changes in pacing mode during long-term follow-up of 399 consecutive patients with sick sinus syndrome treated with an AAI/AAIR pacemaker

This retrospective study included a large cohort of consecutive patients primarily implanted at Skejby University Hospital with an AAI/AAIR pacemaker because of sick sinus syndrome (SSS) from July 1981 to July 1999. The primary aim of the study was to analyze the risk of developing AV block during long-term follow-up. A secondary aim was to study the incidence and reasons for changes in pacing mode caused by other than AV block. A total of 399 patients (231 women, mean age 71 +/- 13.5 years) were identified. Mean follow-up was 4.6 +/- 3.4 years and occurred at death, reoperation with mode change, pacemaker explant, or end of study. During follow-up, 44 patients had a ventricular lead implanted with a mean delay of 2.8 +/- 3.1 years (range 1 day-10.4 years) after the primary implantation. A total of 30 patients received a ventricular lead because of AV block or AF with bradycardia (annual incidence 1.7%). Another 14 patients received a ventricular lead without having documented AV block or AF with pauses (annual incidence 0.8%). The present observational study documents that in patients with SSS treated with AAI/AAIR pacing, AV block requiring implantation of a ventricular lead occurs at a rate of 1.7% per year. It is considered that AAI/AAIR pacing is safe and reliable as treatment for patients with SSS and normal AV conduction.     

TAVR术后传导阻滞及起搏器植入的预测因子研究进展

主动脉瓣狭窄(AS)是由先天或后天因素所引起的瓣膜结构改变,其发病率随着年龄的增长而增加,在80岁以上人群中患病率可达到10%左右,其中严重主动脉瓣狭窄导致的猝死每年发生率约为 1%[1]。经导管主动瓣膜置换术 (TAVR)是一种安全可行的重度AS微创治疗方法,自2011年FDA首次获批应用于无法进行外科手术治疗的重度AS患者,其适应症不断拓展至中低手术风险人群的治疗。人工瓣膜的置入压迫位于主动脉根部的房室传导系统,导致术后心脏传导异常的发生,永久起搏器的植入(PPMI)是其治疗手段。TAVR术后PPMI与患者预后密切相关。因此,本文对TAVR术后传导功能障碍发生及PPMI进行综述。     

Long-term survival after permanent pacemaker implantation in young adults: 30 year experience

The goal of the present study was to determine the etiology of conduction disease and long-term outcome for young adults who undergo permanent pacemaker implantation. Permanent pacing was performed in 232 patients aged 21-50 years, 135 males and 97 females, from 1965 through 1995. One hundred and twenty-six subjects (54%) had evidence of structural heart disease, while idiopathic conduction disease accounted for 46%. About half (54%) of 106 patients with structural heart disease had surgically induced heart block. Pacing mode at primary implantation was single chamber in 65% and dual chamber in 35%. Follow-up ranged from 12-387 months, with a mean of 104-months. At the last follow-up, 133 of 232 patients (57%) were alive, 40 (17%) had died, 30 (13%) were lost to follow-up, 26 (11%) were transferred elsewhere, and 3 (1%) explanted. Patients with sick sinus syndrome had similar outcomes to those with AV block. There was a sharp decline in survival during the first six months; 7.5% of the sample died within the first year following their first pacemaker operation. After the first year, the decline in survival slowed and 70% of the patients could be expected to survive beyond 20 years. The overall survival of young patients without structural heart disease who received a permanent pacemaker was comparable to an age- and sex-matched control population, while patients with structural heart disease performed significantly worse than the control population.     

Leadless pacemaker implantation in dextrocardia with situs viscerum inversus: A case report and literature review

Leadless pacemaker implantation (LPI) has fewer device complications and reduced chance of infection compared to conventional pacemakers. Dextrocardia with situs viscerum inversus (DC+SVI) is a rare condition, which seldom leads to cardiac complications. However, its presence poses a challenge to operators in cardiac procedures. LPI reports in DC patients are scarce. We report a case of LPI in a DC+SVI patient, followed by a brief but comprehensive literature review.     

Atrial Pacing: Who do We Pace and What do We Expect? Experiences with 100 Atrial Pacemakers

The records of 100 patients with permanent atrial pacemakers implanted over a 7-year period were reviewed to assess the role and results of this mode of pacing. Indications for pacing were sick sinus syndrome in 91, carotid sinus hypersensitivity in 3, and use of an antitachycardia device in 6 patients. The mean follow-up period was 32.9 months. Symptomatic relief was good. Lead dislodgment occurred in 11 patients (usually in the first week). Threshold rises not amenable to reprogramming occurred in three patients and loss of sensing occurred in seven patients but only one required intervention. Overall, 21 patients required reoperation. The type of lead did not influence the need for reoperation that appeared to be related to the experience of the operator. Complete atrioventricular block occurred in three patients, two of whom had carotid sinus hypersensitivity and one had sick sinus syndrome. Chronic atrial fibrillation occurred in five patients, none of whom required revision of the pacemaker system. Atrial pacing is a satisfactory pacing mode in patients with sick sinus syndrome. Provided satisfactory atrioventricular conduction has been shown by incremental atrial pacing to at least 120 beats/min and carotid hypersensitivity is absent, progression to complete atrioventricular block is uncommon. Greater implanting skills are required for good results.     

永久起搏器安置术后致锁骨下静脉血栓形成的护理

回顾分析265例埋藏式起搏器安置术后并发锁骨下静脉血栓形成8例的治疗效果和护理经验。7例4～5d治愈,1例14d治愈,所有患者出院时经超声检查锁骨下静脉血栓消失,临床治愈率100%。护理要点:术后严密观察心电图,了解起搏器是否正常工作;观察意识变化,注意肢体是否有肿胀、疼痛和活动受限,将患肢抬高并制动,溶栓期间观察全身是否有皮下出血等。     

Treatment of sick sinus syndrome in a patient with cardiac lymphoma via chemotherapy without pacemaker implantation: A case report

Successful treatment of the acute phase of bradycardia in patients with cardiac lymphoma via medical therapy alone has not been reported. This case report describes the successful treatment of sick sinus syndrome in an 84‐year‐old man with cardiac lymphoma via chemotherapy without pacemaker implantation.     

Criteria for pacemaker explant in patients without a precise indication for pacemaker implantation

Unnecessary pacemaker implantation may cause significant social and psychological consequences, the inconvenience of periodic office visits, and the expense of pulse generator replacement. Establishing adequate criteria for explantingpacemakers is crucial and has notyet been described. This study presents the results of a study protocol for explanting the pacemaker in patients without a clear indication for pacemaker implantation. Seventy pacemaker users without a clear reason for the implantation were included in the study conducted from August 1986 to November 1998 and were prospectively followed. The investigation consisted of clinical and neurological evaluations, echocardiogram, exercise testing, and tilt table testing. When these tests were negative, the pulse generator energy and stimulation rates were reprogrammed to the lowest values. Periodic Holter monitoring was conducted during follow-up. When asymptomatic for 1 year, patients underwent an electrophysiological evaluation of sinus and atrioventricular junction function and ventricular vulnerability. When the electrophysiological study was negative, pacemaker explantation was performed. Of the 70 patients, 35 had their pacemaker explanted; 3 were excluded due to a positive tilt table test and electrophysiological study, and 3 are waitingfor pacemaker explantation. Mean follow-up after pacemaker explantation was 30.3 months, and all patients remained asymptomatic, exceptfor one patient who died of a noncardiac cause. Critical analysis of pacemaker users without a well-established indication is justified because it may allowpacemaker explant in a significant proportion of these patients, and it may bring considerable social, economic, and psychological benefits.     

病态窦房结综合征伴房室传导延迟AAI与DDD起搏模式右心功能的超声评价

目的探讨AAI与DDD起搏模式下病态窦房结综合征伴房室传导阻滞患者的右心功能。方法 35例病态窦房结综合征伴Ⅰ度房室传导阻滞植入DDD双腔起搏器患者,先用程控仪将起搏器程控为DDD模式,最后程控为AAI模式。超声心动图检测患者2种起搏模式下的各参数变化情况。结果 DDD起搏模式下的RVPEP、RVPEP/RVET、Sm、Tei指数明显高于AAI起搏模式（P〈0.05）,E/Em低于AAI起搏模式（P〈0.05）。结论 AAI起搏模式右心的收缩和舒张功能均优于AV间期优化的DDD起搏模式。     

The Natural History of Sick Sinus Syndrome

A literature review has addressed the two major factors in disease progression in sick sinus syndrome: atrioventricular block and atrial fibrillation. An incidence of atrioventricular block of 8.4 percent in a follow-up period of 34.2 months is considered clinically significant and sufficient to justify use of a ventricular lead in pacemaker management. Atrial fibrillation occurs much more commonly [22.3%] in ventricular pacing than with atrial demand pacing (3.9%) in a 21/2 year observation period. Coincident with the reduction in arrhythmia achieved by atrial demand pacing is a significant reduction in systemic embolism (1.6% vs. 13%]. This is considered largely to be due to the improved rhythm control with AAI pacing but also possibly to the avoidance of retrograde atrioventricular conduction. The benefits of AAI pacing in terms of mortality in sick sinus syndrome have not yet been fully assessed. In the future, DDI pacing is recommended with, in some patients, the addition of another sensor to provide rate responsiveness on exercise.     

Refractory hypertensive emergency associated with complete heart block resolved after permanent pacemaker implantation: A case report

Severe hypertension sometimes improves with treatment of bradycardia but this phenomenon is under‐reported. Here, an elderly gentleman with complete heart block and a hypertensive emergency was refractory to medical therapies and blood pressure only improved following pacemaker implantation. We discuss the possible mechanisms relating to heart rate and artificial pacing.     

Spontaneous regression over a 16-year period of tachyarrhythmias to sick sinus syndrome and complete atrioventricular block in a young patient with Ebstein's anomaly

A 25-year-old man with Ebstein's anomaly showed spontaneous regression of tachyarrhythmias to sick sinus syndrome and complete atrioventricular block over a 16-year period. This is the first clinical report supporting the hypothesis that abnormal cell death might contribute to the disturbance of the heart conduction system in Ebstein's anomaly.     

永久起搏器植入术患者发生深静脉血栓的调查分析

目的通过调查了解永久起搏器植入术患者发生深静脉血栓(DVT)的原因。方法回顾性调查2009年1月—2011年12月收治于同济大学附属第十人民医院永久起搏器植入术的患者425例,分析DVT的发生情况和影响因素。结果永久起搏器植入术患者DVT的发生率为7.53%。多因素分析显示,DVT发生与患者年龄、体质指数(BMI)、吸烟史、术后制动时间、DVT病史和基础疾病有密切相关,具有统计学意义(P0.05)。结论针对永久起搏器植入术患者发生DVT的危险因素,进行早期护理干预,可降低DVT的发生率。     

Clinical significance of preserving spontaneous QRS wave in the therapy of DDD pacing for sick sinus syndrome

The aim of this clinical crossover study was to elucidate the effects of atrioventricular (AV) synchronous pacing on cardiac function in patients with sick sinus syndrome (SSS). Thirty SSS patients, each with dual chamber pacemaker (DDD), were enrolled and divided into two groups based on echocardiographic findings. Group A (n = 16) had hypertensive heart disease (wall thickness 11 approximately 12 mm) or mitral or aortic regurgitation (Grade I or II). Group B (n = 14) had no organic heart disease. Three successive 3-month pacing periods were tested. For the first 3 months, long AV delay that achieved > 80% ventricular sensing was chosen. For the next 3 months, AV delay was abbreviated to achieve > 80% ventricular pacing at an optimal AV interval. For the final 3 months, the first setting was resumed. At the end of each period, M mode echocardiography, pulsed-Doppler study, and measurement of plasma brain natriuretic peptide (BNP) level were conducted. In both groups, echocardiographic parameters were not significantly changed during the evaluation. In group A, plasma BNP level was significantly higher at the end of the short AV delay period than at the long AV delay period (P = 0.009), while in group B it did not differ during each period. AV synchronous pacing (> 80% ventricular pacing) in the SSS patients with a DDD pacemaker implanted could increase the ventricular load, and it is better to preserve the spontaneous QRS with the DDD mode with prolonged AV delay in patients with mild hypertensive or valvular disease.     

Determination of the optimal atrioventricular interval in sick sinus syndrome during DDD pacing

BACKGROUND: Although the AAI pacing mode has been shown to be electromechanically superior to the DDD pacing mode in sick sinus syndrome (SSS), there is evidence suggesting that during AAI pacing the presence of natural ventricular activation pattern is not enough for hemodynamic benefit to occur. Myocardial performance index (MPI) is a simply measurable Doppler-derived index of combined systolic and diastolic myocardial performance. The aim of this study was to investigate whether AAI pacing mode is electromechanically superior to the DDD mode in patients with SSS by using Doppler-derived MPI. METHODS: Thirty-nine SSS patients with dual-chamber pacing devices were evaluated by using Doppler echocardiography in AAI mode and DDD mode. The optimal atrioventricular (AV) interval in DDD mode was determined and atrial stimulus-R interval was measured in AAI mode. The ratio of the atrial stimulus-R interval to the optimal AV interval was defined as relative AV interval (rAVI) and the ratio of MPI in AAI mode to that in DDD mode was defined as relative MPI (rMPI). RESULTS: The rMPI was significantly correlated with atrial stimulus-R interval and rAVI (r = 0.57, P = 0.0002, and r = 0.67, P < 0.0001, respectively). A cutoff point of 1.73 for rAVI provided optimum sensitivity and specificity for rMPI >1 based on the receiver operator curves. CONCLUSIONS: Even though the intrinsic AV conduction is moderately prolonged, some SSS patients with dual-chamber pacing devices benefit from the ventricular pacing with optimal AV interval. MPI is useful to determine the optimal pacing mode in acute experiment.     

Is Chronic Atrial Stimulation a Reliable Method for Single Chamber Pacing in Sick Sinus Syndrome?

To evaluate the feasibility of chronic atrial pacing (AAI) in sick sinus syndrome (SSS), 22 patients (pts) with bradytachycardia syndrome (BTS) and 17 patients with only bradyarrhythmias (BA) were studied on the incidence of supraventricular tachycardias (SVT) and occurring AV block. A scoring system based on symptoms of SVT was developed (grade 0–5). All patients had proven normal AV conduction before PM implantation. In the BTS-group, nine patients (41%) had symptomatic SVT at the end of follow-up (mean 53 months), despite drug therapy. These patients had a high SVT score on entry (mean 3.2). High degree AV block occurred in three patients. Although in the BA-group SVT arose in six patients (35%), there was only one symptomatic patient at the end of follow-up (mean 36 months). In this group, only one patient developed high degree AV block. Atrial stimulation should be considered as a reliable therapy in patients with SSS and low SVT score before PM implantation when normal AV conduction is present.