起搏器术后新发房性心律失常的影响因素分析

目的:探讨起搏器术后新发房性心律失常的发生情况及其相关影响因素。方法:选择2006年1月至2007年12月于沈阳军区总医院首次植入永久起搏器的107例患者,男性50例,平均年龄65.0±11.9岁,术前通过追问病史及相关检查均排除房性心律失常(房颤、房扑、房速),术后平均随访3.9年,观察新发房性心律失常情况。按术后是否出现房性心律失常,将患者分为新发房性心律失常组和无房性心律失常组,比较两组患者术前和术后心脏超声结果的变化、心室起搏比例、起搏部位及起搏模式,并通过logistic回归分析起搏器术后发生房性心律失常的影响因素。结果:新发房性心律失常组26例(24.3%),其中房颤17例(15.9%),房扑2例(1.9%),房速7例(6.5%);无房性心律失常组81例。与无房性心律失常组比较,新发房性心律失常组左房内径明显增加(P=0.040)、二尖瓣返流程度较重(P=0.032)及左室射血分数明显下降(P=0.001),心室起搏百分比(VP%)显著升高(P=0.017)。心尖部起搏患者房性心律失常的发生率明显高于间隔部起搏(33.3%vs 16.9%,P<0.05),双腔起搏组患者房性心律失常发生率明显低于单腔起搏器组(18.7%vs 37.5%,P<0.05)。Logistic回归分析显示术后新发房性心律失常的发生与高比例的心室起搏(P=0.006)、VVI(R)起搏模式(P=0.014)及右心室起搏电极导线植于心尖部(P=0.024)显著相关。结论:起搏模式、心室起搏百分比、起搏部位是起搏器术后发生房性心律失常的影响因素。     

New concepts in pacemaker syndrome

After implantation of a permanent pacemaker, patients may experience severe symptoms of dyspnea, palpitations, malaise, and syncope resulting from pacemaker syndrome. Although pacemaker syndrome is most often ascribed to the loss of atrioventricular (A-V) synchrony, more recent data may also implicate left ventricular dysynchrony caused by right ventricular pacing. Previous studies have not shown reductions in mortality or stroke with rate-modulated dual-chamber (DDDR) pacing as compared to ventricular-based (VVI) pacing. The benefits in A-V sequential pacing with the DDDR mode are likely mitigated by the interventricular (V-V) dysynchrony imposed by the high percentage of ventricular pacing commonly seen in the DDDR mode. Programming DDDR pacemakers to encourage intrinsic A-V conduction and reduce right ventricular pacing will likely decrease heart failure and pacemaker syndrome. Studies are currently ongoing to address these questions.     

Occurrence of Torsade de Pointes prior to complete lead connection during pacemaker implantation

Torsade de Pointes (TdP) can be triggered by a pacing spike on the T-wave, due to pacemaker undersensing. However, it is not widely known that this phenomenon can occur even during pacemaker implantation. An 84-year-old woman underwent pacemaker implantation for the treatment of a complete atrioventricular block with dyspnea. During the procedure, immediately following ventricular lead insertion and before torque wrench tightening, TdP was observed. Ventricular pacing was initiated by inserting the lead into the header of the generator; however, sensing remained unstable. T-waves associated with undersensed PVCs and ventricular pacing occurred simultaneously, resulting in a spike on the T-wave and TdP.     

Ventricular Pacing on the Prognosis of Patients with Pacemaker Implantation

Excessive right ventricular apex pacing has significant adverse effects on the cardiac function and hence, it is necessary to clinically optimize pacing parameters and advocate suitable physiological pacing to safeguard the cardiac function after pacemaker implant. Minimizing ventricular pacing is an atrioventricular node priority function, to encourage ventricular self conduction and to reduce unnecessary right ventricular pacing. Minimized ventricular pacing reduces ventricular pacing by encouraging self atrioventricular conduction function and extending the AV interval. This study is a prospective cohort study to evaluate the changes of cardiac function in patients and serum amino-terminal natriuretic peptide (NT-proBNP) before and after pacing, and the risk of atrial fibrillation with different CUM% VP. The study has shown that the cardiac function will deteriorate with an increase in pacing rate.     

Left ventricular dysfunction due to right ventricular stimulation: is biventricular upgrade really necessary?

Left ventricular (LV) dysfunction can occur due to chronic right ventricular apical pacing. Upgrading of the pacemaker to biventricular pacing is an option to reverse LV dysfunction but reprogramming of the atrioventricular (AV) timing can also be favourable. In this case report we describe the effect of AV-time reprogramming in a patient with LV function deterioration that emerged two years after implantation of a dual chamber system for sick sinus syndrome. Echocardiographc studies demonstrated a tremendous improvement in LV function during two years follow-up whereas the percentage of right ventricular pacing diminished dramatically. Careful analysis of the cause of LV deterioration can avoid unnecessary upgrading to biventricular pacing. (Neth Heart J 2010;18:604–5.)     

Right bundle branch block pattern after uncomplicated right ventricular outflow tract pacing in a patient with a left sided superior vena cava and corrected tetralogy of Fallot

Usually an electrocardiogram after right ventricular (RV) pacing should yield left bundle branch block (LBBB) pattern. However, the presence of right bundle branch block (RBBB) pattern after pacemaker implantation should alert the physician to a malposition of lead. We report a case of 18-year-old female who underwent dual chamber pacemaker implantation and had RBBB pattern post implantation. Detailed evaluation revealed an uncomplicated right ventricular outflow tract pacing. The possible causes of this abnormal pattern after an uncomplicated RV pacing are also reviewed.     

Subcutaneous defibrillator use with unipolar pacemakers: Cautiously possible

Implantation of subcutaneous implantable cardioverter-defibrillator in a patient with existing unipolar pacemaker is against manufacturer recommendations. We report the case of a successful subcutaneous implantable cardioverter-defibrillator implantation in a patient with Fontan circulation and concomitant active unipolar pacing and present a summary of recommendations when considering subcutaneous implantable cardioverter-defibrillator implantation with unipolar pacing. Recommendations included: pre-procedure screening, rescreening during implantation and ventricular fibrillation induction, pacemaker programming, and post-procedure investigations.     

The downside of right ventricular apical pacing

The right ventricular (RV) apex has been the standard pacing site since the development of implantable pacemaker technology. Although RV pacing was initially only utilized for the treatment of severe bradyarrhythmias usually due to complete heart block, today the indications for and implantation of RV pacing devices is dramatically larger. Recently, the adverse effects of chronic RV apical pacing have been described including an increased risk of heart failure and death. This review details the detrimental effects of RV apical pacing and their shared hemodynamic pathophysiology. In particular, the role of RV apical pacing induced ventricular dyssynchrony is highlighted with a specific focus on differential outcome based upon QRS morphology at implant.     

边界处电偶联对1D生物起搏器的作用 — 一种仿真研究

现在生物起搏器越来越引起学者们的关注. 本文旨在研究边界处的电偶联对生物起搏器起搏及驱动能力的影响. 首先利用各向异性的反应扩散方程,建立了包含生物起搏器的1D心室组织模型. 基于该模型,仿真了不同边界电偶联对应的起搏器初次起搏时间、特殊位置细胞的动作电位、心电的传导过程等参考项,发现减弱边界处的电偶联对生物起搏器的起搏能力具有一定的增强作用;然而,当电偶联足够小时,起搏器的电兴奋却不能有效传出,导致其驱动心室组织失败. 另外,本文探讨了边界电偶联的大小与起搏器最小尺寸之间的关系,发现电偶联越小,起搏器成功起搏所需的细胞数量越少,但是细胞数量变化并不明显. 因此,仅仅减弱电偶联对生物起搏器有一定的增强作用,但如果生成高效的起搏器,仍需辅助其它措施.     

Selective His-bundle pacing in an adult with atrioventricular canal defect via retrograde His localization

Adult congenital heart disease patients may undergo numerous fluoroscopically guided procedures including pacemaker implantation during their lifetime. One alternative to traditional pacemaker setup which may improve long-term pacing outcomes is His bundle pacing. Given the altered His-bundle location, and given increased radiation exposure over a lifetime, we used 3-dimensional mapping to locate the His and to minimize fluoroscopy for placement of a His-bundle pacemaker system in a 31-year old patient with atrioventricular canal defect and complete heart block with 100% RV pacing and epicardial lead fracture.MethodsAn Octapolar Livewire catheter (Abbott, Minneapolis, USA) was used for mapping and location of the His bundle from a right femoral venous access on the EnSite Precision system 3-dimensional mapping system (Abbott Medical, Abbott Park, IL). The same map was used to guide 3830 lead placement into the posterior-inferior His-bundle position.ResultsSuccessful placement of a His-bundle pacing system with thresholds of 1Volt@0.4ms for both the atrial and ventricular leads with selective His-bundle pacing noted. Ten-month follow-up demonstrated His-bundle capture at 0.75V@0.4ms with stable impedance, sensing and with 100% right ventricular pacing a projected longevity of 12 years total.ConclusionsSuccessful placement of selective His-bundle pacing can be achieved in an adult patient with atrioventricular canal defect using 3-dimensional mapping.     

AAI to DDD pacing mode inappropriate switches in a dual chamber pacemaker due to ventricular blanking period

A 90-year-old woman received a dual chamber pacemaker (PM) for a sick sinus syndrome. The PM was programmed with SafeR AAI-DD pacing mode at 60 bpm. During a standard follow up, some memorized electrograms (EGMs) were found in SafeR diagnostics, with atrial pacing (Ap) not followed by any ventricular sensing/pacing event, due to simultaneous junctional activity falling into ventricular blanking period during Ap and, for this reason, unsensed by the PM. Blanking periods can affect PM functioning if not revealed and adjusted.     

Atrial Pacing to Control Heart Rate and Rhythm in Acute Cardiac Conditions

Increasing the heart rate by a bedside atrial pacing technique was successfully utilized to treat serious cardiac arrhythmia or failure in 13 patients. Nine of these had ventricular arrhythmia refractory to drugs. Seven had evidence of sinus node depression or disease since their sinus pacemaker was below 70 beats per minute under decompensated conditions. In five, coronary artery disease was associated with the bradycardia and in two, digitalis toxicity was related to depression of the intrinsic pacemaker rate. Two patients in the coronary group required implantation of a permanent demand ventricular pacemaker. Hemodynamic studies were performed in seven patients. Only one patient had no increase in cardiac output with pacing rates above his resting rate. The other six patients showed an increase in cardiac output from 22 to 81% at paced rates between 70 and 125/minute. The duration of pacing ranged from one hour to 14 days and averaged five days.     

Atrial pacing, the forgotten pacing mode

In patients with sick sinus syndrome and normal atrioventricular conduction, physiological pacing can be accomplished with either a single chamber atrial pacemaker AAI/R or a dual chamber pacemaker DDD/R. The single chamber device has the advantages of simpler implantation and lower initial costs, while the dual chamber device offers protection in case atrioventricular conduction disturbances develop in the future. When rigorous attention is paid to the pre-implantation selection criteria, the incidence of reported second- or third-degree atrioventricular block varied between 0.4 and 1.8% per annum. Medical practice, however, has shifted to predominant implantation of DDD/R pacemakers in more than 95% of patients with sick sinus syndrome. Recent publications have reported an increase in left atrial diameter, decrease in left ventricular fractional shortening and increased incidence of atrial fibrillation in patients with DDD/R pacing as compared with patients with single chamber atrial devices. These changes were proportional to the percentage of ventricular paced beats. New algorithms in dual chamber devices have been developed in order to minimise ventricular stimulation. These are being evaluated at present. In my opinion there is still a place for atrial pacing in selected patients with sick sinus syndrome with a minimum risk of developing complete atrioventricular block. (Neth Heart J 2008;16(suppl 1): S25-S27.)     

Intermittent Right Ventricular Outflow Tract Capture due to Chronic Right Atrial Lead Dislodgement

A 58 year old male, known case of type 2 diabetes and hypertension, had undergone implantation of a dual chamber pacemaker(DDDR) in 2007 for complaints of recurrent syncope and trifascicular block with a normal ejection fraction andnormal coronaries. His post implantation parameters were normal at that time.He now presented to our pacemaker clinic where his ECG done showed two types o fpaced complexes. The first few complexes were consistent with atrial sensed right ventricular apical pacing with left superior axis. Later complexes showed loss of atrial sensing with pacing from right ventricular outflow tract(inferior axis) with subtle oscillation in it''s axis. On application of magnet, two pacemaker spikes were visible withinterspike interval of 120 ms and paced complexes with inferior axis starting from the first spike suggesting that the atrial lead was responsible for RVOT depolarization. On interrogation of the pacemaker, atrial EGM showed sensed activity from atrium followed by large sensed ventricular complex. Fluoroscopy confirmed that the atrial lead was dislodged and was intermittently prolapsing into the RVOT. Since the patient was asymptomatic, he refused any intervention and subsequentlyhis atrial lead was switched off by telemetry. The above case signifies that asymptomatic lead dislodgement is no talways manifested as loss of capture and even subtle variation of the axis o fthe paced complexes can provide us with a clue that can be confirmed by telemetry of the pacemaker and fluoroscopy.     

Prevention of Hemodynamic Instability in Extra-Cranial Carotid Angioplasty and Stenting Using Temporary Transvenous Cardiac Pacemaker

Hemodynamic instability is a common condition during extra-cranial carotid angioplasty and stenting (CAS). We evaluated the safety and efficacy of prophylactic placement of temporary cardiac pacemaker during extra-cranial CAS for the prevention of hemodynamic instability. For this, forty-seven carotid artery stents were deployed in 41 high-risk patients. Temporary transvenous cardiac pacemakers were inserted before CAS procedure. The pacers were set to capture a heart rate <60 bpm. Clinical symptoms, blood pressure, heart rate, and pacing activation were monitored and data were collected. We found that pacing occurred in 25 carotid lesions during balloon predilatation; pacemakers were activated transiently in 25 patients. The longest pacing continued for 1 day. Among cases with pacemaker activation, 1 patient developed post-procedural symptomatic hypotension that lasted for 4 days. No related complications were observed. It was, therefore, concluded that pacing was technically effective in producing electrical ventricular responses and was hemodynamically effective in 25 carotid lesions which underwent balloon predilatation. The prophylactic use of a temporary transvenous cardiac pacemaker during CAS was rapid and effective in controlling peri-operative hemodynamic instability and preventing stroke and other complications. The prophylactic use of temporary pacemaker is particularly recommended for patients at high risk for developing hemodynamic instability.     

Atrial fibrillation and pacing algorithms

Pacing prevention algorithms have been introduced in order to maximize the benefits of atrial pacing in atrial fibrillation prevention. It has been demonstrated that algorithms actually keep overdrive atrial pacing, reduce atrial premature contractions, and prevent short-long atrial cycle phenomenon, with good patient tolerance. However, clinical studies showed inconsistent benefits on clinical endpoints such as atrial fibrillation burden. Factors which may be responsible for neutral results include an already high atrial pacing percentage in conventional DDDR, non-optimal atrial pacing site and deleterious effects of high percentages of apical ventricular pacing. Atrial antitachycardia pacing (ATP) therapies are effective in treating spontaneous atrial tachyarrhythmias, mainly when delivered early after arrhythmia onset and/or on slower tachycardias. Effective ATP therapies may reduce atrial fibrillation burden, but conflicting evidence does exist as regards this issue, probably because current clinical studies may be underpowered to detect such an efficacy. Wide application of atrial ATP may reduce the need for hospitalizations and electrical cardioversions and favorably impact on quality of life. Consistent monitoring of atrial and ventricular rhythm as well as that of ATP effectiveness may be extremely useful for optimizing device programming and pharmacological therapy.     

Virtual reality 3D echocardiography in the assessment of tricuspid valve function after surgical closure of ventricular septal defect

Background

Chronic right ventricular apical pacing may have detrimental effect on left ventricular function and may promote to heart failure in adult patients with left ventricular dysfunction.

Methods

A group of 99 pediatric patients with previously implanted pacemaker was studied retrospectively. Forty-three patients (21 males) had isolated congenital complete or advanced atrioventricular block. The remaining 56 patients (34 males) had pacing indication in the presence of structural heart disease. Thirty-two of them (21 males) had isolated structural heart disease and the remaining 24 (13 males) had complex congenital heart disease. Patients were followed up for an average of 53 ± 41.4 months with 12-lead electrocardiogram and transthoracic echocardiography. Left ventricular shortening fraction was used as a marker of ventricular function. QRS duration was assessed using leads V₅ or II on standard 12-lead electrocardiogram.

Results

Left ventricular shortening fraction did not change significantly after pacemaker implantation compared to preimplant values overall and in subgroups. In patients with complex congenital heart malformations shortening fraction decreased significantly during the follow up period. (0.45 ± 0.07 vs 0.35 ± 0.06, p = 0.015). The correlation between the change in left ventricular shortening fraction and the mean increase of paced QRS duration was not significant. Six patients developed dilated cardiomyopathy, which was diagnosed 2 months to 9 years after pacemaker implantation.

Conclusion

Chronic right ventricular pacing in pediatric patients with or without structural heart disease does not necessarily result in decline of left ventricular function. In patients with complex congenital heart malformations left ventricular shortening fraction shows significant decrease.     

Reverse RAMP (REVRAMP) pacing: A novel anti tachycardia pacing technique

Anti-tachycardia pacing (ATP) is frequently used to terminate ventricular tachycardia (VT), however it is not always successful and may accelerate VT requiring defibrillation. REVRAMP is a novel concept of ATP that involves delivering pacing at a faster rate than VT, but instead of abruptly terminating pacing after eight beats, pacing is gradually slowed until VT continues or normal rhythm is restored. In a pilot study we show that REVRAMP can restore normal rhythm, and that if REVRAMP is unsuccessful, VT is not accelerated.     

Differences in pacemaker programming between electrophysiology specialists and other physicians

BackgroundAppropriate programming of cardiovascular implantable electronic devices (CIED) is essential to ensure adequate function and avoid harmful effects. In underdeveloped countries, CIED monitoring and programming are often performed by physicians involved in their implantation. However, many of them often do not have sufficient training in CIED programming.ObjectiveWe aimed to assess the differences in pacemaker programming between electrophysiology (EP) specialists and other physicians.MethodsWe retrospectively reviewed changes in pacemaker programming performed by an EP specialist in patients who attended for pacemaker evaluation and reported previous follow-ups by a non-EP specialist.ResultsAmong 58 patients (26 males), 41 patients (71%) had programming errors and required setting modifications. The rate adaptative pacing function (R-mode) was incorrectly deactivated in 9 patients (15%) and improperly activated in 2 patients (3%). Unnecessary ventricular stimulation was detected in 23 patients (40%) with a pacing burden of 60% (32–95%). The lower rate limit was unnecessarily high in 12 patients (21%).Atrial or ventricular pacing output was inappropriate in 15 patients (26%) and was consequently modified (4 patients unnecessarily high, 9 patients below requirements). The auto-adapted pacing output was switched off in 17 of 18 patients (16 due to physician's preference, and 1 due to algorithm inaccuracy). The programmed sensitivity was inaccurate in 2 patients (3%). In 2 patients (3%) switching from DDDR to VVIR mode was required.ConclusionWe found a high prevalence of errors in pacemaker programming by non-EP specialists. An EP specialist should always be responsible for CIED follow-up.     

Effects of different rates of cardiac pacing on rat myocardial energy status

The energy status of mammalian cells is a finely regulated phenomenon. This is especially true in cardiac muscle cells in which energy requirements are high and the system must provide rapid turnover of the adenine nucleotides and instant response to changes in energetic demands. We have examined the acute response of the rat myocardium to ventricular pacing up to 2.5 times the resting heart rate. The purpose of this study was to determine at what level of pacing the normal energy status could be maintained and at what point it was compromised. Myocardial energy charge (EC = (ATP + 0.5 ADP)/(ATP + ADP + AMP)) was maintained at 1, 1.5 and 2 times the resting heart rate but declined significantly at 2.5 times. In contrast, phosphorylation potential (PP = ATP/ADP₁ × Pi) was drastically altered in hearts paced at 1.5, 2 and 2.5 times the resting rate. Tissue lactate increased and glycogen decreased in a linear fashion as pacing rate increased, indicating that the metabolic challenge was proportional to the pacing rate. EC seems to reflect the overall status of the cell and its ability to maintain a dynamic equilibrium. PP may reflect the immediate and necessary driving force for mitochondrial respiration in times of increased demand. These data suggest that the myocardium may meet the increased energy demands of acute ventricular pacing by shifting the molar ratio of ATP to ADP times Pi in favour of driving phosphorylation.