Atrial fibrillation in patients with a dual defibrillator: characteristics of spontaneous and induced episodes and effect of ventricular tachyarrhythmia induction

BACKGROUND: The pattern of FF intervals during atrial fibrillation (AF) has been analyzed in induced and spontaneous AF episodes, after the induction of ventricular fibrillation (VF) and after atrial shock, in order to suggest practical considerations for AF management in patients implanted with antitachycardia devices. METHODS: In 13 patients implanted with a dual-chamber defibrillator, FF intervals were analyzed during two separate induced AF episodes, before and after VF induction over AF, as well as during spontaneous AF episodes and after unsuccessful atrial shocks. The following parameters were considered: mean atrial cycle length (CL), atrial CL stability, and standard deviation of the atrial cycle. RESULTS: The AF pattern had comparable characteristics considering two separate inductions of AF, as well as spontaneous AF episodes. Ventricular tachyarrhythmia induction resulted in a shortening of atrial CL (P < 0.02) and in a less organized AF pattern (P < 0.005). Changes in the FF interval after ineffective shock therapy showed a shortening of AF cycles after shocks with energies far below the defibrillation threshold. CONCLUSIONS: (a) The AF pattern is reproducible in separate inductions of sustained AF and in spontaneous episodes, (b) dynamic changes involving a shortening of the AF cycle and an evolution to a less homogeneous pattern occur after VF induction, revealing a complex interplay between AF and VF, and (c) FF interval analysis after ineffective shock delivery may allow the relationship between delivered shock energy and effective defibrillation energy to be estimated, thereby providing practical suggestions for step-up protocols in atrial cardioversion.     

Multiple episodes of ventricular tachycardia induced by silent coronary vasospasm

We present a 46-year-old patient who suffered from cardiac arrest and subsequently underwent placement of an implantable cardioverter defibrillator (ICD). The patient underwent a cardiac catheterization which revealed no significant coronary artery disease. About 1 year later he experienced appropriated and frequent ICD discharges due to monomorphic ventricular tachycardia (VT) with left bundle branch block morphology. His prodromal symptoms were mild dizziness and lightheadedness with no chest pain. Amiodarone, mexiletine, sotalol and dofetilide as well as ablation of two inducible ventricular tachycardias in the electrophysiology studies were unsuccessful in controlling the arrhythmias and ICD discharges. During the last episode, he experienced a mild burning sensation in his chest and was given nitroglycerin 0.4 mg sublingually, which relived his symptoms and aborted the VT. This led to a second cardiac catheterization to investigate whether the VT was being induced by myocardial ischemia. This second coronary angiogram spontaneously revealed significant coronary vasospasm and simultaneously, the patient’s cardiac rhythm showed short runs of VT with left bundle branch block morphology. Intracoronary nitroglycerine relieved the coronary vasospasm and terminated the arrhythmia. The patient was treated with isosorbide mononitrate and diltiazem. He remained symptom free with no ICD discharges and no VT in ICD interrogations for more than 2 years. Coronary vasospasm may be silent and with no chest pain which creates a difficult clinical situation particularly if it is associated with ventricular tachycardia and sudden cardiac death. The mechanisms of VT in the setting of coronary vasospasm are not known and increased automaticity, focal discharges, functional unidirectional block with reentry, or a combination of these mechanisms may contribute to inducing the VT during the transient ischemia or rarely in the reperfusion phase. It is important to perform provocative tests to diagnose silent coronary vasospasm in unexplained sudden cardiac arrests.     

Increased cycle length variability during ventricular fibrillation: a novel predictor of arrhythmia recurrence

To evaluate the clinical value of cycle length (CL) variability during ventricular fibrillation (VF), 26 patients who underwent implantable cardioverter defibrillator (ICD) implantation were enrolled. In VF induced for defibrillation testing, mean and SD of VFCL, mean successive differences (MSD) of VFCL, and coefficient of variations of the VFCL (CV(FF)) (SD x 100/mean VFCL) were calculated. During the follow-up period of 20 +/- 2 months, ventricular arrhythmias recurred in 13 patients. MSD and CV(FF) were 31 +/- 3(*) ms and 15.6 +/- 1.3(**) in recurrence group (n = 13), and 17 +/- 2 ms and 9.0 +/-1.1 in non-recurrence group (n = 13) ((*)P <.005, (**)P <.001 vs. nonrecurrence group). Relatively good repeatability of mean VFCL, MSD and CV(FF) in each patient was confirmed by the Bland-Altman method. In VF induced by programmed ventricular stimulation before ICD implantation, MSD and CV(FF) in recurrence group were also increased significantly. Kaplan-Meier estimates revealed that MSD >or= 20 ms and CV(FF) >or= 12 predicted higher arrhythmia recurrence (MSD, P =.039; CV(FF), P =.0069 by the log-rank test). By multivariate analysis, CV(FF) >or= 12 was a significant predictor of recurrent arrhythmic events (P =.019). In conclusion, the CL variability of VF, which was evaluated as MSD and CV(FF), is increased in patients with arrhythmia recurrence. These values may reflect the degree of electrical heterogeneity, and appears to be useful indexes of the future arrhythmic events.     

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。     

An external automatic device to detect ventricular fibrillation

An analysis of a micro-processor-based system to detect cardiacarrest rhythms was made in a series of 84 cardiac arrests in78 patients. The ECG was sensed using 2 external ECGjdefibrillatorpads applied to the chest wall. In 5 arrests, the initial rhythmwas continuous electrical pacing in addition to the cardiacarrest and these were not included in the analysis. Of the remaining79 arrests, there were 15 in which the initial rhythm was ventricularfibrillation and 14 were correctly detected by the system (sensitivity93%). In the remaining 64 arrests the initial rhythm was notventricular fibrillation and 62 were correctly identified (specificity97%). A high specificity is required in any device employingautomatic detection of ventricular fibrillation. Continuouselectrocardiographic recordings of the cardiac arrests wereanalysed every 8 to 18 s: of 223 sections showing ventricularfibrillation, 165 were correctly determined by the system, i.e.sensitivity 74%, where the rhythm was not ventricular fibrillation,of the 5002 sections 4953 were correctly detected by the system,i.e. specificity 99%. The percentage accuracy of detection ofventricular fibrillation varied from 25–100% (mean 81%)and for detection of non-ventricular fibrillation from 57–100%(mean 99%) in every 8 to 18 s section of ECG tracing per cardiacarrest episode. Thus the automatic detection of cardiac arrestrhythms is feasible with a high degree of accuracy.     

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.     

Evaluation of the effectiveness of a wearable cardioverter defibrillator detection algorithm

Background

Wearable cardioverter defibrillators (WCDs) provide protection from sudden cardiac death. The efficacy of a WCD detection algorithm has not been reported outside of clinical trial.

Methods

The efficacy of the algorithm was reviewed through a retrospective analysis of appropriate shocks, inappropriate shocks, and arrhythmia detections during a 1-year period.

Results

WCD patients had an appropriate shock rate of 1.58 per 100 patient-months and an inappropriate shock rate of 0.99 per 100 patient-months. Most of the arrhythmia detections in a 3-month period were short in length, with only 2.7% of the detections lasting over 25 seconds, the time at which a shock becomes possible.

Conclusions

By incorporating a patient responsiveness test, as well as features that eliminate or reduce signal interference common to external electrocardiogram electrodes, the WCD detection algorithm has a low risk of inappropriate shocks.     

Ablation of atrial fibrillation in Brugada syndrome patients with an implantable cardioverter defibrillator to prevent inappropriate shocks resulting from rapid atrial fibrillation

Background

Inappropriate shocks resulting from atrial tachyarrhythmias are highly problematic for patients with an implantable cardioverter defibrillator (ICD). We aimed to determine the effectiveness of catheter ablation of atrial fibrillation (AF) in preventing inappropriate shocks due to rapid AF in patients diagnosed with Brugada syndrome (BS) who were implanted with an ICD.

Methods

We performed AF ablation in 5 BS patients with ICDs who experienced inappropriate shocks caused by rapid paroxysmal AF and in a BS patient scheduled to determine an indication of an ICD implantation who frequently experienced rapid AF.

Results

Although 2 patients underwent a 2nd ablation procedure because of AF recurrences, 5 of the 6 patients were finally free from AF after their last procedure during a median follow-up period of 43.2 months. No further inappropriate shocks caused by rapid AF occurred after the 1st ablation session in any of the patients. A patient developed a ventricular fibrillation storm during his electrophysiological study following the ablation procedure, and then was implanted with an ICD.

Conclusions

AF ablation in BS patients may be reasonable to prevent inappropriate ICD shocks resulting from rapid AF. However, ventricular extrastimuli just after the ablation had better be avoided in them.     

埋藏式心脏转复除颤器安置的临床经验

总结非开胸经锁骨下静脉穿刺安置埋藏式心脏转复除颤器 (ICD)的手术方法、除颤阈值 (DFT)测定及ICD工作参数设置等临床经验。 10例患者 ,6例有反复晕厥病史。 2例晕厥时心电图证实为心室颤动 (简称室颤 ) ,体外电除颤成功 ,另 8例心内电生理均诱发出持续性室性心动过速或室颤。其中冠心病 8例 (1例合并Brugada综合征 ) ,扩张性心肌病 1例 ,原发性室颤 1例。 5例术前口服胺碘酮治疗。结果 :全部经锁骨下静脉置入ICD ,术中所有患者成功诱发室颤 ,并一次电击成功。手术时间 92± 2 7min。DFT≤ 2 0J,电击阻抗 4 1.2± 15 .3Ω ,R波高度 16 .3± 6 .6mV ,无手术并发症。结论 :经锁骨下静脉置入ICD方法简单 ,安全可靠 ;术前口服适量胺碘酮对术中诱发室颤无影响。     

特发性心室颤动长期随访的临床与心电图特征

目的 分析特发性心室颤动(室颤)患者的心电图与临床特征,探讨其与预后之间的关系.方法 21例特发性室颤患者,男性10例(47.6%),初次发生症状年龄平均(38.5±19.0)岁,随访分析其临床及体表心电图特征,按照心电图有无J波分为J波阳性组(J+组)和J波阴性组(J-组),比较两组死亡和室颤、晕厥发生的情况.结果 21例特发性室颤的患者中,9例室颤发生于凌晨睡眠时,5例室颤发生于情绪激动时,7例室颤发作无明确诱因.J+组(n=15)中有7例心电图J波合并QRS波切迹,1例合并早期复极.合并QRS波切迹的7例患者室颤发作时间为凌晨睡眠中.平均随访(42.4±39.9)个月后,J+组患者的年平均室颤发作次数明显高于J-组(n=6),分别为(1.3±0.5)次/年和(0.4±0.3)次/年,P＜0.01.J+组死亡2例,J-组死亡1例.多因素回归分析结果显示,特发性室颤患者中J波阳性患者出现室颤复发的危险性高于J波阴性患者(RR 1.9,95%CI 1.1～2.9;P=0.03).结论 报道QRS波切迹的室颤患者有相似的凌晨睡眠时发作特点;J波在特发性室颤患者中的发生率较高,而且预示着具有更高的室颤复发率.J波有望成为特发性室颤预后的预测因子.     

心室颤动初始节律的动态心电图观察

目的 探讨心室颤动(室颤)初始心搏与室性早搏(室早)或室性心动过速(室速)是否同源,为消融室颤提供基础数据。方法 选择室颤高危患者记录动态心电图,比较室颤初始心搏与室早或室速各导联QTS形态的一致性,形态一致者起源点相同,作初步定位。结果 96例患者中,28例检出60例次室颤,55例次发作初始的3～53个心搏为有序的快速室速或扑动样节律,平均周长(185±36.4)ms。12例次自行终止,持续1.2-21.6(6±8.4)s;40例次电击终止;8例未终止死亡。1例次初先室颤,中转为室速,后又转为室颤。室颤自行终止与非自行终止者相比,初始节律的周长差异无显著性[(202±42.6)ms与(182±38.6)ms,P=0.066]。50例次室颤可见与其初始QRS形态一致的单发、成对室早或室速。48例次初始心搏为R-on-T。42例次初始QRS无伪差干扰,起源点呈聚集而非随机分布,18例次对应于右室前乳头肌区,6例次对应于右室流出道,11例次对应于左室前乳头肌区,7例次对应于左室后乳头肌区。9例多次室颤,7例有2-5种QRS形态。22例可见与室颤初始QRS态不同、未触发室颤的室早或室速。结论 室颤与某些室早或室速同源,起源点聚集分布,好发于乳头肌周围,以室早或室速起源为消融靶点有望消除室颤。自行终止的短阵室颤并不少见,及时识别有着生命攸关的临床意义。     

Variation of spectral power immediately prior to spontaneous onset of ventricular tachycardia/ventricular fibrillation in implantable cardioverter defibrillator patients

INTRODUCTION: Short-term heart rate variability (HRV) may change immediately before onset of a ventricular arrhythmia (ONSET). METHODS AND RESULTS: Power spectrum analysis was performed on instantaneous heart rate (IHR; including all beats) and normal heart rate (NHR; excluding ectopics) curves obtained at equally spaced 0.5-second intervals using a cubic spline. The database consisted of 135 sets of 1,024 RR intervals leading to ventricular arrhythmia (VA) and controls from 78 patients. Total periodogram and time course of spectral power were obtained. Ten spectral bands of 0.1-Hz bandwidth (0 to 1 Hz) were analyzed. A simple threshold technique was retrospectively used to predict the onset of a VA. RR intervals that led to VA ONSET had significantly higher total spectral power than controls (P < 0.001 for both NHR and IHR for every band). Spectral power remained constant until 100 seconds before ONSET and then increased significantly in the time window immediately preceding ONSET (P < 0.02 compared with others). Using a simple threshold method, a predictive accuracy of 68%+/-1.4% was obtained with different window sizes. Using specific spectral bands, the predictive accuracy of VA ONSET could be improved to 76% for IHR and 71% for NHR (0.8- to 0.9-Hz band). CONCLUSION: Our results suggest that a sustained higher power increase in NHR and IHR occurs during the course of 12.11+/-.57 minutes, followed by a sudden elevation in spectral power within 100 seconds of ONSET, and may be a precursor to ventricular tachycardia/ventricular fibrillation episodes.     

Initiation of ventricular fibrillation by atrial fibrillation

We report the case of a patient who developed spontaneouslya ventricular fibrillation during atrial fibrillation, 8 minafter a perfusion of isoproterenol was stopped Two mechanismscould explain the ventricular arrhythmia: silent ischaemia anda long-short cycle sequence just before ventricular fibrillation.     

Differences in amiodarone efficacy in relation to ejection fraction and basal rhythm in patients with implantable cardioverter defibrillators

Background

Atrial fibrillation (AF) and ventricular arrhythmias (VAs) are associated with increased morbidity and mortality. However, data are lacking concerning the association of AF and VAs. This study aimed to clarify the association between AF and VAs and to investigate the effect of amiodarone on the incidence of VAs in patients with implantable cardioverter defibrillators (ICDs).

自主研发体外自动除颤器的实验研究

目的 评价自主设计和研制体外自动除颤器(AED)对室性心动过速(室速)/心室颤动(室颤)识别的敏感性、特异性以及除颤效果.方法 应用交流电刺激实验动物诱发室速/室颤,记录并分析AED对窜速/室颤的识别以及除颤放电的整个过程,评价其诊断识别和除颤性能.结果 诱颤96次,除颤145次,记录心电数据167段次,共计103 740 S.室速/室颤的识别准确性为99.5%,敏感性为98.2%,特异性为99.6%.除颤成功率和除颤能量呈正相关,成功除颤的能量阈值为(78.75±35.64)J,电量阈值为(0.11±0.04)C,电压阈值为(1216.67±260.87)V.结论 自主研制的AED具有较高的识别敏感性和特异性,其识别和除颤效果达到或优于国外同类产品.     

埋藏式心脏转复除颤器的长期随访观察

目的分析埋藏式心脏转复除颤器(ICD)治疗恶性室性心律失常的疗效。方法4例患者中共置入6台ICD,通过常规心电图、动态心电图及ICD程控分析仪进行随访,对患者情况及ICD工作情况进行分析,合理调整起搏参数,心律失常药物,及时处理ICD故障。结果6台ICD共检出心律失常事件272次,启动治疗程序64次,其中包括低能量复律和高能量除颤转复室性心动过速和心室颤动19次(占29.7%,19/64),抗心动过速起搏成功治疗室性心动过速35次(占54.7%,35/64),误放电治疗10次(占15.6%,10/64)。误放电原因包括:感知窦性心动过速3次,电磁干扰2次,电极导线绝缘层破损干扰5次。其余208次心律失常事件均在ICD启动诊断识别过程中自行终止,ICD未继续实施治疗程序。结论ICD治疗恶性室性心律失常效果肯定,但应加强随访,警惕误放电。     

置入埋藏式心律转复除颤器的长期随访

目的报道8例埋藏式心脏转复除颤器（1CO）治疗恶性室性心律失常的疗效及随访结果。方法对置入ICD的8例患者进行电话询问和门诊随访,通过常规心电图、动态心电图及ICD存储的资料,对患者病情和ICDT作情况进行分析。结果8台ICD共检出心律失常事件263次,其中202次为短阵非持续性室性心动过速（VT）,自行终止,61次为持续性VT／（室颤）VF,32次为抗心动过速（ATP）终止,21次为低能量电击终止,8次为高能量电击终止,再发恶性室性心律失常全部经ICD成功转复为窦性心率,有效率100％。误放电治疗8次。误放电原因：阵发性心房颤动心室率超过设置的VT频率,ICD发生误识别。结论ICD治疗恶性室性心律失常效果肯定,但应加强随访,警惕误放电。     

Prevention of recurrent ventricular fibrillation by ventricular rate stabilization.

This report describes a post-infarct patient with recurrent ventricular fibrillation in the absence of acute ischaemia, in whom arrhythmia recurrences could be prevented by ventricular rate stabilization of a third-generation cardioverter defibrillator. Review of the literature and clinical implications are discussed.     

Cardioversor desfibrilhador implantável subcutâneo – experiência de um centro

BackgroundImplantable cardioverter‐defibrillators (ICDs) are important tools in the prevention of sudden death, but implantation requires transvenous access, which is associated with complications. Subcutaneous implantable cardioverter‐defibrillators (S‐ICDs) may prevent some of these complications.AimTo evaluate the therapeutics and complications associated with S‐ICD systems.MethodsS‐ICD implantation was planned in 23 patients, for whom the indications were vascular access problems, increased risk of infection or young patients with long predicted follow‐up. The population consisted of four patients with ischemic heart disease, three of them on hemodialysis (two with subclavian vein thrombosis), five with left ventricular noncompaction, four with Brugada syndrome, three with arrhythmogenic right ventricular cardiomyopathy, one with transposition of the great vessels, two with dilated cardiomyopathy and four with hypertrophic cardiomyopathy.ResultsS‐ICDs were implanted in 21 patients, two having failed to fulfil the initial screening criteria. Mean implantation time was 77 minutes, with no complications. Defibrillation tests were performed, and in one patient the generator had to be repositioned to obtain an acceptable threshold.In a mean follow‐up of 14 months, 10 patients had S‐ICD shocks, which were appropriate in half of them; one developed infection, one needed early replacement due to loss of telemetry and one patient died of noncardiac cause.ConclusionsS‐ICD implantation can be performed by cardiologists with a high success rate. Initial experience appears favorable, but further studies are needed with longer follow‐up times to assess the safety and efficacy of this strategy compared to conventional devices.