Arrhythmia detection by dual-chamber implantable cardioverter defibrillators. A review of current algorithms.

This article reviews the arrhythmia detection criteria currently available in dual-chamber implantable cardioverter defibrillators (ICDs), and describes the implementation and performance of various detection algorithms. Nearly all criteria implemented in single-chamber devices appear to have been included in dual-chamber ICDs. However, two different strategies can be distinguished: the first adds dual-chamber inhibition criteria to a single-chamber detection configuration; the second is a new approach entirely based on a dual-chamber detection scheme. Despite widely available clinical data, an analysis of the implemented detection indexes, arrhythmia characteristics (induced vs spontaneous, minimum duration), device programming (detection rate, programme maintenance and tuning during follow-up), and different storage capabilities among various ICD models, leaves the results of these studies ultimately ambiguous. New algorithms are under study, but only protocols using a single set of arrhythmias and the same programming for all devices may allow relevant comparisons of the performances of detection algorithms. Furthermore, a criterion is required to distinguish reliably between haemodynamically stable and unstable tachycardias, not simply based on rate, but including the underlying cardiac function.     

An unusual resolution of T-wave oversensing in an implantable cardioverter defibrillator in a child with long QT syndrome

T-wave oversensing poses a clinical challenge often resulting in inappropriate therapies and shocks. T-wave oversensing can often be resolved by certain programmable adjustments while accepting a small risk of undersensing ventricular fibrillation. The following case depicts a girl with LQT whose transvenous defibrillator repeatedly demonstrated T-wave oversensing despite optimizing various programmable features and a separate pace/sense lead. Utilization of an LV epicardial pace/sense lead with stable R-waves affirmed an unusual resolution of T-wave oversensing and avoidance of inappropriate shocks.     

Implantable cardioverter defibrillator: charge saver, not syncope saver!

In patients with an implantable cardioverter defibrillator, empirical antitachycardia pacing/burst pacing (ATP) is associated with a significantly decreased rate of appropriate shocks. The use of ATP as first-line therapy in ventricular tachycardia promotes less pain and better quality of life because the number of shocks is reduced. Additionally, battery longevity is substantially increased with this strategy. Based on this, device manufacturers have developed new algorithms to optimize the use of ATP and shocks in patients with an implantable cardioverter defibrillator. The present report describes a case in which the use of one of these new algorithms was associated with a significant delay in tachycardia termination and, consequently, led to syncope.     

植入型心律转复除颤器治疗恶性室性心律失常的疗效评价

目的评价单中心40例植入型心律转复除颤器(ICD)治疗恶性室性心律失常的疗效及安全性。方法40例恶性室性心律失常包括室性心动过速(室速)或心室颤动(室颤)患者接受ICD治疗,男性35例,女性5例,平均年龄(49±15)岁,成功随访35例,应用体外程控仪获得ICD储存资料并结合临床随访资料进行分析。结果40例患者均成功植入ICD;35例患者平均随访25个月,其中26例患者共记录室速和室颤事件763阵,ICD成功除颤224阵(成功率99．1％),抗心动过速起搏1次成功终止室速375阵(成功率71．8％),低能量同步转复22阵(成功率100％);2例患者因窦性心动过速和心房颤动伴快速心室反应发生误放电4次。术后大多数患者联合应用抗心律失常药物。至随访期末,死亡4例,3例死于顽固性心力衰竭,1例死于肺栓塞。结论ICD联合应用抗心律失常药物能有效治疗恶性室性心律失常,预防心脏性猝死。     

Defibrillation testing at the time of implantation of cardioverter defibrillator in the clinical practice: a nation-wide survey.

AIMS: Despite an effective defibrillation testing (DT) is considered mandatory to be consistent with the rules of good clinical practice, some physicians are concerned about the risk of complications related to the induction test, and in real world clinical practice, several implant procedures are performed without any induction test. We conducted a systematic nation-wide retrospective survey in order to determine the DT rate and its complications. METHODS AND RESULTS: An ad hoc questionnaire was sent to all 343 Italian implanting centres and the data from the 229 (67%) centres that answered were analysed. During the year 2005, a total of 7857 patients underwent a first implantation of cardioverter defibrillator (ICD), 38% of which with cardiac resynchronization therapy (CRT). Of these, 2356 (30%) were implanted without any induction test. In 35 (15%) centres, the induction test was performed in < 25% of the patients, whereas in 136 (59%) centres, it was performed in > 75% of the patients. At multivariable analysis, performed in a subset of 1206 patients from 107 centres, CRT device (OR = 1.82) and primary prevention (OR = 1.47) were independent predictors of the decision to not perform DT. However, altogether, the clinical variables accounted only for 35% of the total variance, whereas the remaining 65% was probably unrelated to clinical factors. There was a total of 22 (0.4%) life-threatening complications as a consequence of the induction test: 4 deaths (0.07%), 8 cardiopulmonary arrests requiring resuscitation manoeuvres (0.15%), 6 cardiogenic shocks (0.11%), 3 strokes (0.05%), and 1 pulmonary embolism (0.02%). CONCLUSION: In real world practice, DT is not performed in a substantial number of patients, most of these in the absence of legitimate reasons. The clinical impact of DT vs. no DT remains unclear until the not negligible complication rate is compared against the long-term potential benefit.     

Cross-talk in a dual-chamber defibrillator presenting as pacemaker alternans

This case report highlights the occurrence of pacemaker alternans in a dual-chamber defibrillator. Pacemaker alternans occurs secondary to cross-talk. The sensing algorithm and basic timing cycles are reviewed.     

Cardiac arrhythmias: Implantation of a unipolar cardioverter/defibrillator system under local anaesthesia

OBJECTIVE: To evaluate prospectively the safety and feasibility of theimplantation of cardioverter/defibrillator systems under localanaesthesia. Conventionally, cardioverter/ defibrillator systemsare implanted under general anaesthesia. With the developmentof single-lead trans venous unipolar cardioverter/defibrillatorsystems for sub-pectoral implantation a pacemaker-like approachfor device implantation appears applicable. METHODS: Implantation of a single-lead transvenous unipolar cardioverter/defibrillatorunder local anaesthesia with sedation for defibrillation thresholdtesting was performed in 37 consecutive patients. The presentingarrhythmia was ventricular fibrillation in 13 patients, andmonomorphic ventricular tachycardia in 24 patients. A 1% lidocainesolution was used for local anaesthesia, and midazolam was appliedfor sedation to perform defibrillation threshold testing. Arterialblood pressure, arterial oxygen saturation and heart rate weremonitored throughout the procedure. The patient's toleranceof the implantation procedure was evaluated with a standardizedquestionnaire. RESULTS: The unipolar transvenous cardioverter/defibrillator system wasimplanted successfully in all patients under local anaesthesia.During defibrillation threshold testing, sufficient sedationwas achieved with 1·2±3·7 mg midazolam.For determination of the defibrillation threshold 5·9±1·4episodes of ventricular fibrillation were induced. The meandefibrillation threshold was 13·1±5·5 J,and the mean duration of the implantation procedure was 68±30mm. Mean heart rate, mean arterial blood pressure and arterialoxygen saturation were not significantly different before andafter defibrillation thresh old testing. Twenty-six patients(70%) were symptom-free throughout the implantation procedure;most of the remaining patients reported minor symptoms. Therewere no complications, and patients were discharged 2·2±0·7days after implantation. In 12 patients, post-implant testingof the implantable cardioverter/defibrillators was performedsuccessfully, without sedation, 2·8±1·4days after as an outpatient procedure. CONCLUSION: Single-lead unipolar transvenous implantable cardioverter/defibrillatorsystems can be safely implanted under local anaesthesia withmild sedation for defibrillation threshold testing. The procedureis well tolerated     

植入型心律转复除颤器电风暴的临床随访和治疗

目的本文观察植入犁心律转复除颤器（ICD）植入后电风暴的发生率、临床特征、临床治疗。方法回顾性分析了51例接受ICD治疗的病人,随访2～85个月,其中9例病人出现ICD电风暴,比较ICD电风暴组和无ICD电风暴组的年龄、病因左心室射血分数（LVEF）、心功能分级、临床特征、临床治疗方案。结果有电风暴的患者与无电风暴患者相比年龄更大,差异有统计学意义[（69±14）岁对（61±8）岁];心功能分级（2．7±0．7对2．1±0．6,P〈0．05）差异有统计学意义;两组LVEF（0．38±n09对0．48±0．04,P〈0．05）差异有统计学意义。在本文中导致ICD电风暴的主要因素是心功能的减退。结论有电风暴的病人比没有电风暴的病人年龄更大,心功能更差,LVEF更低。心力衰竭的加重和焦虑导致的交感神经兴奋是电风暴发生主要的原因。抗心律失常药物胺碘酮和美托洛尔是预防和治疗电风暴的主要手段。射频消融可作药物治疗无效后减少电风暴的主要于段。     

埋藏式心脏转复除颤器植入后电风暴的临床观察

目的探讨应用埋藏式心脏转复除颤器(ICD)后出现电风暴现象的一般规律及诊治经验。方法总结1996年8月至2008年6月间96例ICD植入患者术后电风暴的发生率、发生原因及治疗方法 ,并比较单次电风暴患者与多次电风暴患者在年龄、随访时间、首次电风暴发生时间及左室射血分数(LVEF)等方面的指标。结果随访时间中位数为12个月,有12例(12.5%)发生了电风暴,首次电风暴事件距离ICD植入术后的中位数为31天。相对于单次电风暴患者而言,发生多次电风暴患者的LVEF较低。结论 ICD患者植入术后,电风暴的发生率为12.5%,多次发生电风暴的患者具有低LVEF的特点。     

具有埋藏式心脏转复除颤器植入适应证患者的调查与随访

目的调查符合植入埋藏式心脏转复除颤器(ICD)适应证患者的基础病因、临床特征、治疗选择及预后。方法入选本院符合ICD适应证的152例患者,收集其基本资料及相关病史,记录入院期间检查结果及治疗情况,并对死亡率和恶性室性心律失常发生率进行随访。结果符合ICD适应证患者以缺血性心脏病最多;ICD心脏性猝死一级预防适应证患者明显多于二级预防适应证患者(118 vs 34);二级预防适应证患者植入ICD的比例明显多于一级预防适应证患者[44.1%(15/34)vs 9.3%(11/118)];随访结束发现植入ICD/CRT-D患者的全因死亡率要明显低于未植入ICD/CRT-D患者[0%vs 17.5%(20/114)](P<0.05)。结论 ICD/CRT-D能减低ICD适应证患者的全因死亡率,然而临床上ICD作为心脏性猝死预防的实际应用要远远低于其指征范围。     

Implantable cardioverter defibrillator following acute myocardial infarction: the '48-hour' and '40-day' rule

Until recently, randomized studies of implantable cardioverterdefibrillator (ICD) have only included patients with a remotehistory of myocardial infarction (MI). Two studies evaluatedthe use of ICDs early following MI, the DINAMIT and BEST+ICDstudies, but failed to demonstrate significant reduction inmortality. Current guidelines therefore recommend deferringICD implantation for at least 40 days following MI. This articlehighlights the limitations of these two studies and reviewsthe application of the ‘40-day’ rule to patientswith acute MI.     

Cardiac transplantation in a patient with emotionally triggered implantable cardioverter defibrillator storms

The implantable cardioverter defibrillator (ICD) may be responsible for psychological disorders especially among patients experiencing multiple shocks. An associated hyperadrenergic state (e.g., anger, anxiety) may trigger malignant ventricular arrhythmias repeatedly treated by ICD shocks, entertaining a “vicious circle” often difficult to interrupt. Despite aggressive cardiac and psychological therapeutic efforts, this condition may be refractory, finally leading to heart transplantation, as described in this case report.     

Hospital readmission after transvenous cardioverter/defibrillator implantation; a single centre study.

AIMS: Hospital readmission after implantation of cardioverter/defibrillators has a major impact on quality of life and cost-effectiveness in defibrillator patients. Rehospitalization has not been studied in large patient populations with modern transvenous defibrillation systems. METHODS AND RESULTS: We report on incidence, reasons, time in follow-up, duration and predictors of hospital readmission in 180 patients after transvenous implantation of a cardioverter/defibrillator during a follow-up period of 25+/-18 months. There were 156 readmissions in 79 patients with a 0.87 readmission rate per patient during the time followed, a 0.46 readmission rate per patient-year of follow-up and a 0.38 readmission rate per patient-year of follow-up for cardiac reasons. The majority of readmissions was caused by multiple appropriate shock interventions (26%), battery depletion (19%) and lead- and device-related complications (14%). The time to first hospital readmission was 12+/-9 months for arrhythmia-related and 20+/-16 months for other cardiac-related reasons (P<0.05), and could not be predicted by clinical variables, respectively. The duration of rehospitalization was 14+/-15 days for cardiac-related reasons and 12+/-17 days for arrhythmia-related reasons. Age >60 years was an independent predictor of rehospitalization time per patient-year of follow-up for both cardiac-related (P<0.005) and arrhythmia-related reasons (P<0.05). CONCLUSION: The rate of hospital readmission per patient-year of follow-up is as high as 0.46 after implantation of a modern cardioverter/defibrillator. Rehospitalization time in such patients is significantly longer in the patient cohort >60 years. The majority of readmissions is caused by multiple appropriate shock treatments. Further studies are needed to systematically investigate strategies for the prevention of rehospitalization in modern ICD therapy.     

单中心植入埋藏式心脏转复除颤器患者的随访

目的了解本中心植入埋藏式心脏转复除颤器(ICD)/双室同步起搏+除颤器(CRT-D)患者的临床特征,并进行长期随访以期了解其患者的预后和转归。方法对57例植入ICD/CRT-D的患者,其中一级预防23例,二级预防34例,收集其基本资料及相关病史,记录入院期间检查结果及治疗情况,并对其死亡率和恶性室性心律失常发生率进行随访。结果一级预防恶性心律失常发生率低于二级预防(21.7%vs 43.8%),所有患者无心律失常死亡,治疗成功率近100%。结论 ICD/CRT-D能减低患者恶性心律失常死亡。     

Impaired detection of ventricular tachyarrhythmias by a rate-smoothing algorithm in dual-chamber implantable defibrillators: intradevice interactions

INTRODUCTION: Rate smoothing is an algorithm initially designed to prevent rapid changes in pacemaker rates. In this study, we sought to determine the potential of the rate-smoothing mechanism in preventing detection of ventricular tachyarrhythmias. METHODS AND RESULTS: Clinical testing of rate smoothing was performed at the time of defibrillator arrhythmia induction in 16 patients with implantable defibrillators during 65 episodes of ventricular tachyarrhythmias. We also performed simulator-based testing to assess detection of ventricular tachycardia between 170 and 220 beats/min with systematic sequential change of rate-smoothing percent, AV delay, and maximal rate. During clinical testing of 54 ventricular fibrillation/polymorphic ventricular tachyarrhythmia episodes, there were no cases of nondetection and 3 episodes (5%) of minimally delayed detection. Of 10 monomorphic ventricular tachyarrhythmias, 6 had either delayed (2 cases) or absent (4 cases) detection. During simulator testing, complex interrelationships were demonstrated in AV delay, upper rate, and rate-smoothing percent in determining the severity of the effect on detection. Generally, long AV delay, higher upper rate, and smaller (more aggressive) rate smoothing were associated with increased risk of ventricular tachyarrhythmia underdetection. Importantly, use of parameters that impaired detection was always accompanied by a programmer warning message. CONCLUSION: Rate smoothing may result in delay or failure of ventricular tachycardia detection. It is important to consider warning messages when programming rate smoothing and to test for appropriate detection when rate smoothing is used despite warning messages.     

植入型心律转复除颤器不适当识别和治疗的发生率及常见原因

目的 植入型心律转复除颤器（ICD）是恶性室性心律失常患者惟一有效的治疗措施。不适当识别和治疗是ICD最常见的并发症，也是导致ICD患者再住院最主要的原因。本文旨在评价本中心的ICD患者不适当识别和治疗的发生率及常见原因。方法 入选2000年1月至2005年12月在本中心因室性心律失常植入ICD并能定期随访的50例患者。根据患者心律失常特点和心功能情况程控ICD的各项参数，定期随访，询问ICD中所有信息，打印、存盘并对储存的腔内电图进行逐条分析，以确定ICD诊断是否准确以及治疗是否有效，判断有无ICD不适当识别和治疗。结果 38例患者在随访期间发生了心律失常事件，ICD共记录到491次室性心动过速（VT）或心室颤动（VF）事件（VT383次，VF108次），其中有11例（22％）发生过≥1次的不适当识别和治疗事件。14．3％（55／383）的VT事件为不适当识别，并导致了78次抗心动过速起搏（ATP）治疗和9次电击治疗。VF不适当识别的发生率为26．9％（28／108），并导致了56次不适当电击事件。结论 植入新一代ICD患者中，不适当识别和治疗发生率仍较高。不适当识别和治疗最常见的原因是心房颤动（房颤）伴快速心室率，占50％以上；其次是由于电磁干扰或肌电干扰所致。     

The pacemaker and implantable cardioverter defibrillator recall issue - a Canadian perspective

In 2005, an unprecedented number of recalls were issued on pacemakers and implantable cardioverter defibrillators. While recalls in the cardiac rhythm device industry are not new, the sheer magnitude of potentially affected patients in 2005 led to a great deal of concern, frustration, and even anger. Physicians have, in many instances, been uncertain when (or if) to recommend device replacement in an environment where the magnitude of the risk and the potential consequences of device failure have not been well defined in a timely way. Doctors and patients are now calling for reform of postmarket analysis and reporting mechanisms. The present article provides a uniquely Canadian perspective on this international issue. Potential solutions include the development of a set of realistic and common expectations, a restoration of confidence in postmarket analysis and reporting mechanisms, increased data transparency, and an increased role for patient and physician groups.     

Diagnostic performance of a dual-chamber cardioverter defibrillator programmed with nominal settings: a European prospective study

INTRODUCTION: Despite technologic developments, accurate discrimination of ventricular tachyarrhythmia from rapid rhythms of nonventricular origin remains a challenge. We sought to examine the sensitivity and specificity of a dual-chamber arrhythmia detection algorithm, the PARAD algorithm, incorporated in a dual-chamber implantable cardioverter defibrillator, the Defender (ELA Medical). METHODS AND RESULTS: All detailed tachycardia episodes (i.e., with stored atrial and ventricular channel markers and electrograms) retrieved from the Holter memory of the device were analyzed from 95 patients (86 men and 9 women; age 62 +/- 12 years) implanted with the Defender with the algorithm programmed at nominal settings. Over a follow-up of 15 +/- 8 months, 559 detailed sustained tachycardia episodes detected in the tachycardia zone were gathered in 62 patients. Of the 300 ventricular tachycardia (VT) episodes, 298 were appropriately classified as VT by the algorithm. Of the 259 supraventricular tachycardia (SVT) episodes, 231 were appropriately classified as SVT. In 8 patients, 28 episodes of SVT were misclassified as VT: 25 atrial fibrillation episodes (6 patients), 2 sinus tachycardia (1 patient), and 1 atrial tachycardia. Calculated sensitivity and specificity were 99.3% and 89.2% on a per episode basis and 99.8% (95% confidence interval: 97.8 to 100) and 91.6% (95% confidence interval: 86.0 to 97.3) on a per patient basis, respectively. CONCLUSION: In this selected population of patients, the PARAD algorithm was safe and reliable for detection of a wide spectrum of tachyarrhythmias. Its specificity was high, particularly with respect to sinus tachycardia detection, but it must be improved with respect to detection of atrial fibrillation.     

家庭监护系统在植入心律转复除颤器患者随访中的应用价值

目的 了解家庭监护系统在植入心律转复除颤器（ICD）患者随访中的应用价值.方法 纳入2010年6月～2012年6月置入带有家庭监护系统（HM）的ICD患者30例,通过HM网站收集的患者各项测试参数及黄色和红色报警记录,分析心律失常事件监测和治疗的准确性和及时性,并与门诊随访结果进行比较.结果 随访334～1078（637.83±217.134）天,累计9例患者报告室性心律失常事件发生,1例患者曾出现误识别及误放电治疗.HM系统反应时间随事件严重程度逐渐缩短.同时,与门诊随访相比,HM系统在网络通畅的前提下,可以做到全覆盖随访.共收到黄色报警258次,红色报警5次,通过与患者及时进行电话联系,及时治疗,减少并避免ICD事件再次发生.30例患者中报告死亡3例,均为非心源性死亡.结论 通过HM系统使用,可以对ICD置入患者的恶性心律失常事件进行有效监控,避免ICD事件的再次发生和治疗,提高ICD使用安全性.     

Reduction of ventricular tachyarrhythmia by treatment of atrial fibrillation in ICD patients with dual-chamber implantable cardioverter/defibrillators capable of atrial therapy delivery: the REVERT-AF Study.

AIMS: The purpose of this prospective, randomized, multicentre study was to investigate whether the incidence of ventricular tachyarrhythmia can be reduced in standard implantable cardioverter/defibrillator (ICD) patients by implanting a dual-chamber ICD capable of atrial therapy delivery. METHODS AND RESULTS: A Jewel AF or GEM III AT ICD (Medtronic Inc., Minneapolis, MN, USA) was implanted in 122 patients (62.3 +/- 10.5 years; 84.4% male; coronary artery disease 71.3%; left ventricular ejection fraction 39.7 +/- 13.6%; secondary ICD indication 91%). Overall, 31.2% of the patients had paroxysmal atrial fibrillation (AF)/atrial tachycardia (AT) before ICD implantation (n = 38). Implantable cardioverter/defibrillator therapies for AT/AF were activated and de-activated every 3 months in a cross-over study design. The mean follow-up was 18.5 +/- 7.7 months (6.29 +/- 2.2 cross-over/patient). Overall, there were 684 episodes of ventricular tachyarrhythmias in 48.4% of patients (n = 59). In 33.6% of patients (n = 41), 532 supraventricular tachyarrhythmias occurred. Activation of ICD therapies for AT/AF did not result in a reduction of ventricular tachyarrhythmias (P = 0.92). Patients with monomorphic ventricular tachycardias (mVTs) as index arrhythmia for ICD implantation or inducible mVTs in the electrophysiological study had the highest probability of recurrences of ventricular tachyarrhythmias. CONCLUSION: For patients with standard indications for ICD therapy and no indication for cardiac pacing, a dual-chamber ICD capable of atrial tachyarrhythmia treatment offers no benefit concerning a reduction of ventricular tachyarrhythmias.