Current role of device therapy to reduce sudden cardiac death in heart failure

Sudden cardiac death (SCD) continues to be a major contributor to mortality in patients with heart failure (HF) despite recent advances in medical therapy. Device therapy, including the implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy (CRT), serves as an adjunct in reducing HF mortality. Several clinical trials support the prophylactic use of the ICD in reducing mortality in certain HF populations and have established the clinical benefits of CRT in advanced HF. More recently, the Comparison of Medical Therapy Pacing and Defibrillation in Heart Failure trial was the first study to demonstrate a survival benefit of CRT alone or in conjunction with an ICD. This article reviews the most pertinent data regarding the role of device therapy in reducing SCD in HF and addresses future challenges faced by device manufacturers and clinicians.     

Update of implantable cardioverter/defibrillator and cardiac resynchronization therapy in heart failure

PURPOSE OF REVIEW: Heart failure prevalence is reaching epidemic proportion in the United States and is associated with significant morbidity and mortality. A large proportion of the mortality is the result of sudden cardiac death (SCD). Clinical trials have demonstrated the superiority of the implantable cardioverter/defibrillator (ICD) compared with antiarrhythmic drugs for secondary prevention of sudden cardiac death. RECENT FINDINGS: Recently, several clinical trials in primary prevention of sudden cardiac death in both ischemic and nonischemic heart failure have been completed. The 2002 guidelines for implantable cardioverter/defibrillator implantation were recently released as well. Adjunct therapy consisting of antiarrhythmic drugs or radiofrequency ablation is necessary in the subset of patients with implantable cardioverter/defibrillator that have frequent or intractable ventricular arrhythmias. An emerging new therapy in the heart failure population is cardiac resynchronization therapy, which coordinates right and left ventricular pacing in a subset of patients with interventricular conduction delay. SUMMARY: Several randomized clinical trials have demonstrated improvements in heart failure-related symptoms, exercise tolerance, and reversal of ventricular remodeling. Meta-analysis of these trials has also demonstrated mortality benefit. Patient selection, left ventricular pacing site, and optimal device programming are issues that need further investigation. Recent trials have also studied the compatibility between cardiac resynchronization therapy and implantable cardioverter/defibrillator as a single device. Finally, the DAVID trial has raised concerns of conventional right ventricular pacing and the risk of heart failure in a subset of patients.     

心衰患者心源性猝死的一级预防

心衰患者SCD平均发生率约40％。 本文综述SCD发生率、原因、高危病人的识别及药物治疗对SCD的影响。并且概述ICD在SCD一级预防中的重要性。     

植入心律转复除颤器作为心力衰竭患者心脏性猝死的一级预防

心力衰竭是多种心脏疾病发展至晚期的一个严重临床综合征,随着人口老龄化速度的加快、心血管疾病发病率的上升,心脏疾病尤其是心肌梗死的有效治疗使更多的患者得以生存,但随后慢性心力衰竭患者日趋增多。心力衰竭最终死亡原因主要是进行性心力衰竭加重和／或心脏性猝死（SCD）。     

The future of implantable defibrillator and cardiac resynchronization therapy trials

Implantable cardioverter defibrillator (ICD) trials were initially limited to survivors of sudden death. The focus of defibrillator trials in the last decade has been in prophylactic implantation of the device in high risk populations for the prevention of sudden cardiac death. It is the contention in this review that the new focus for implantable defibrillator trials in 2008 and beyond will be on more selective and focused use of this therapy. This could be achieved by selecting ICD patients based on their pathophysiologic and genetic risk. Increasing effort will also be placed on using the device for prevention of spontaneous malignant ventricular tachyarrhythmias and the index clinical sudden death event. Finally, implantable defibrillators will be used in combination in a “hybrid” therapy approach. ICDs will be increasingly combined either with ventricular tachycardia ablation or ventricular fibrillation ablation using catheter techniques. With the addition of cardiac resynchronization therapy in these devices, new clinical trials that use cardiac resynchronization therapy as an early intervention in specific high risk heart failure populations and refinement of the CRT technique to improved optimal results are in progress. Finally, combining ICD devices and regenerative medicine approaches to myocardial replacement therapy are being explored. Dr. Saksena is a consultant and/or investigator for Medtronic Inc., St. Jude Medical Inc., Sanofi Aventis, and Aryx Pharmaceuticals.     

Sudden death prophylaxis in heart failure

Sudden cardiac death (SCD) is the leading cause of mortality in heart failure (HF). Today the implantable cardioverter-defibrillator (ICD) has become a commonplace therapy around the world for patients with both ischemic and non-ischemic cardiomyopathy and an ejection fraction (EF) < or = 35%. However, EF alone does not discriminate between the modes of death from HF (sudden arrhythmic death vs. non-sudden death). Other risk statifiers, such as electrophysiologic study and microvolt T-wave alternans testing, should therefore be used in the appropriate settings to minimize the number of unnecessary device implants. In addition, left ventricular mechanical dyssynchrony has now become recognized as an additional major marker of cardiac mortality. Its assessment should entail echocardiography rather than measurement of the QRS duration. This will allow us to better integrate the ability of cardiac resynchronization therapy (CRT) in enhancing cardiac function with the ability of an ICD in preventing SCD. This review aims to: 1) give a synthesis of the published evidence regarding the value of implantable ICDs and CRT in the primary prophylaxis of SCD in HF; 2) discuss controversial clinical issues in this area; and 3) recommend practical device-based management strategies.     

CRT-D在慢性心力衰竭患者的临床应用

目的 心脏再同步治疗（CRT）可以显著改善慢性心力衰竭（CHF）患者心功能,而植入型心律转复除颤器（ICD）可以有效预防心脏性猝死.具有CRT和ICD功能的CRT-D已开始应用于临床.本文初步总结CRT-D的临床应用.方法 4例药物治疗无效的CHF患者,合并左束支阻滞、左心室舒张末内径增大,而且既往有室性心动过速病史.其中扩张性心肌病3例,缺血性心肌病1例.接受组织多普勒检查证实存在心脏运动不同步后,接受了CRT-D治疗.结果 4例患者均成功植入CRT-D.左心室起搏导线植入到心脏后静脉3例,心脏侧后静脉1例.术中测试除颤能量≤20 J,无并发症发生.术后1周左心室射血分数从0.34增加至0.42。结论 CRT-D植入技术难度大,风险高,但其安全性肯定.鉴于其显著疗效,建议同时满足CRT和ICD适应证的患者应该接受CRT-D治疗.     

Update on implantable cardioverter defibrillator trials

Many randomized trials of implantable cardioverter defibrillator (ICD) therapy versus medical treatment for the prevention of death in survivors of cardiac arrest or in patients at high risk of sudden cardiac death (SCD) have been reported. ICD therapy has been consistently efficacious in preventing SCD. ICD therapy has generally favorably impacted total mortality, but this has depended upon the control group's risk for arrhythmic and nonarrhythmic mortality. In these trials, predictors of sudden or total mortality better than ventricular dysfunction have not emerged. This review summarizes the randomized ICDs trials and the impact ICDs have on SCD prevention.     

Mode of death in advanced heart failure: the Comparison of Medical, Pacing, and Defibrillation Therapies in Heart Failure (COMPANION) trial.

OBJECTIVES: The aim of this study was to evaluate the mode of death in patients with advanced chronic heart failure (HF) and intraventricular conduction delay treated with optimal pharmacologic therapy (OPT) alone or OPT with biventricular pacing to provide cardiac resynchronization therapy (CRT) or CRT + an implantable defibrillator (CRT-D). BACKGROUND: Limited data are available on mode of death in advanced HF. No data have existed on mode of death in these patients who also have an intraventricular conduction delay and are treated with CRT or CRT-D. METHODS: Using prespecified definitions and source materials, seven cardiologists assessed mode of death among the 313 deaths that occurred in the Comparison of Medical, Pacing, and Defibrillation Therapies in Heart Failure (COMPANION) trial. RESULTS: A primary cardiac cause was present in 78% of deaths. Pump failure (44.4%) was the most common mode of death followed by sudden cardiac death (SCD) (26.5%). Compared with OPT, CRT-D significantly reduced the number of cardiac deaths (38%, p = 0.006), whereas CRT alone was associated with a non-significant 14.5% reduction (p = 0.33). Both CRT and CRT-D tended to reduce pump failure deaths (29%, p = 0.11 and 27%, p = 0.14, respectively). The CRT-D significantly reduced SCD (56%, p = 0.02), but CRT alone did not. CONCLUSIONS: Pump failure deaths are the predominant mode of death in patients with advanced HF and are modestly reduced by both CRT and CRT-D. Only CRT-D reduced SCD and thus produced a favorable effect on cardiac mortality.     

心脏性猝死与植入型心脏转复除颤器

心脏性猝死（SCD）是威胁人类生命的一大杀手,植入型心脏转复除颤器（ICD）是其预防治疗的有效手段,成为SCDⅠ级预防和Ⅱ级预防的标准治疗方法。近年来ICD在临床应用取得了不少的发展与进步,本文在此对其进行简述。     

Roles and indications for use of implantable defibrillator and resynchronization therapy in the prevention of sudden cardiac death in heart failure

Implantable devices are indicated in the primary and secondary prevention of potentially life-threatening ventricular tachyarrhythmias in patients with heart failure. Early studies, including the landmark MADIT trials, showed that implantable cardioverter–defibrillator (ICD) and cardiac resynchronization therapy (CRT) devices can play a significant role in aborting and preventing ventricular arrhythmias, respectively, that can cause sudden cardiac death. To this day, there have been a number of randomized controlled trials, with respective substudy analyses, that have attempted to better understand the indications for these interventions in patient care. Here, we summarize the major results of these studies, and we discuss the role of ICD therapy for both ischemic and non-ischemic cardiomyopathy, emerging evidence in support of wearable defibrillators, and the impact of modified ICD programming strategies on patient outcomes. Regarding CRT therapy, the phenomenon of ventricular reverse remodeling is an important prognostic indicator in preventing future ventricular tachyarrhythmia episodes. In summation, we provide an overview of the possible selection criteria that can be used in identifying appropriate patients for ICD and/or CRT therapy, as supported by the data.     

植入型心律转复除颤器在心力衰竭心脏性猝死一级预防中的作用初步观察

目的总结我院应用植入型心律转复除颤器（ICD）进行心力衰竭心脏性猝死（SCD）一级预防的初步经验。方法入选我院近3年因严重心力衰竭植入ICD进行SCD一级预防的患者,术后3个月进行ICD常规随访,以后每6个月随访1次。结果入选患者22例,其中单腔ICD15台,双腔ICD7台。22例患者随访时间3～28个月。记录ICD治疗事件21次,包括12次抗心动过速起搏（ATP）治疗和9次放电,只有1次ATP治疗患者具自觉症状。其中正确治疗（appropriate therapy）11次（52％）包括8次ATP治疗和3次放电,误治疗（inappropriate therapy）10次（48％）。发生误治疗患者均为植入单腔ICD。结论ICD可以安全有效地应用于心力衰竭SCD的一级预防,ICD误治疗事件是值得重视的临床问题,合理的ATP治疗可以提高患者的生活质量。     

Is implantable defibrillator indicated in all patients on cardiac resynchronization therapy?

Implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy (CRT) have been introduced during the recent years to improve survival, decrease hospital readmissions and mortality, and to improve functional status and quality of life for patients with heart failure and left ventricular systolic dysfunction (LVSD). Studies which evaluated the use of CRT or ICD alone or compared CRT with CRT-ICD in patients with heart failure and LVSD are listed in this article. The results obtained are already influencing clinical practice in the US, where it has been estimated that 90% of patients receiving a CRT device now are being implanted with an ICD component. However, it is still today debated whether patients with LVSD and heart failure should be routinely offered a CRT-ICD. In fact, there are some issues that still should be solved before to establish indication for CRT-D in all heart failure patients with an indication for CRT: 1) a non complete agreement among the different societies which wrote recommendations for guidelines (a comparative table is reported); 2) a better identification of implantable patients and an amelioration of utilized devices; 3) economic and ethical ramifications of this therapy. Anyway still now the crucial question is: 'Can resynchronization be done in isolation or must be accompanied by an ICD device?'. To answer to this question we can only express which is, in our opinion, the actual position of many physicians who work in the field of pacing and electrophysiology: 'The lesson to be learned is that we still can not predict surely which patient will die of sudden death. Until a method of identifying the high risk patients can be developed, the safest strategy should be to advise a combined ICD-CRT device for patients with indication for CRT'.     

Wearable cardioverter defibrillator: Bridge or alternative to implantation?

The implantable cardioverter-defibrillator(ICD) is effective to prevent sudden cardiac death(SCD) in selected patients with heart disease known to be at high risk for ventricular arrhythmia. Nevertheless, this invasive and definitive therapy is not indicated in patients with potentially transient or reversible causes of sudden death, or in patients with temporary contraindication for ICD placement. The wearable cardioverter defibrillator(WCD) is increasingly used for SCD prevention both in patients awaiting ICD implantation or with an estimated high risk of ventricular arrhythmia though to be transient. We conducted a review of current clinical uses and benefits of the WCD, and described its technical aspects, limitations and perspectives.     

Early automatic remote detection of combined lead insulation defect and ICD damage

Lead and implantable cardioverter defibrillator (ICD) devicefailure is a severe problem in ICD therapy and may occur withoutpreceding signs of deterioration. Insulation lead failure andsubsequent ICD defect 7 months after ICD implantation for secondaryprevention of sudden cardiac death (SCD) in a 70-year-old malewas automatically detected with the Home Monitoring system.Immediate lead and device replacement was performed. This caseillustrates the benefit of permanent automatic remote monitoringof implanted active devices.     

The role of prophylactic implantable cardioverter defibrillators in heart failure: Recent trials usher in a new era of device therapy

Sudden cardiac death (SCD) manifested as ventricular fibrillation or sustained ventricular tachycardia has been a major focus of cardiovascular research for more than three decades. Although mortality in patients with heart failure (HF) caused by left ventricular systolic dysfunction has declined in recent years through effective pharmacotherapeutic strategies, SCD remains the major cause of death in symptomatic HF, with little improvement by drug therapy. Although it is clear that the implantable cardioverter defibrillator (ICD) is efficacious and should be used to prevent a recurrence of sustained ventricular arrhythmia (secondary prevention) in most patients, the guidelines for prophylactic use of ICDs (primary prevention) are less well defined. The results of recent clinical trials examining the efficacy of prophylactic ICD therapy in HF patients have clarified the role of ICD treatment in this population. This article reviews these trials and summarizes our current approach to the prevention of SCD in HF.     

Epicardial CRT-P- and S-ICD Implantation in a Young Patient with Persistent Left Superior Vena Cava

Persistent left superior vena cava is known to be a challenging anatomic abnormality for transvenous cardiac device implantation. In the a case of a young man presenting with dilative cardiomyopathy with severely impaired left ventricular ejection fraction (LVEF) and second-degree atrioventricular block (AV block), cardiac resynchronization therapy (CRT) with defibrillator (CRT-D) implantation was indicated. A transvenous approach was attempted, but placement of the right ventricular lead was not successful due to anatomic abnormalities. Therefore, epicardial CRT leads were implanted via a left mini-thoracotomy. For primary prevention of sudden death, the patient was also fitted with an additional subcutaneous implantable cardioverter defibrillator (S-ICD). Any cross-talk between the devices was ruled out both intraoperatively and by ergometry prior to discharge. The combination of epicardial CRT-P with S?ICD implantation might be a safe and effective alternative in patients with cardiac anatomic abnormalities.     

Should Primary Prevention ICDs Still Be Placed in Patients with Non-ischemic Cardiomyopathy? A Review of the Evidence

Purpose of Review

Recent evidence has suggested that implantable defibrillator (ICD) in non-ischemic cardiomyopathy (NICM) may not offer mortality benefit in the presence of guideline-directed medical therapy (GDMT) and cardiac resynchronization therapy (CRT).

Recent Findings

Despite significant benefits of GDMT and CRT, current evidence is derived from ICD trials that rely predominantly on reduced left ventricular ejection fraction alone (LVEF). The majority of patients with sudden cardiac death (SCD) have LVEF >?30% indicating that LVEF by itself is an inadequate predictor of SCD. The Danish study to assess the efficacy of ICD in patients with non-ischemic systolic heart failure on mortality (DANISH) highlights the importance of better risk stratifying NICM patients for ICD implantation.

Summary

Assessment of life expectancy, comorbidities, presence of advanced heart failure, etiology of NICM, and the presence of myocardial fibrosis can help risk stratify ICD beyond LVEF. Genetics and biomarkers can be of further assistance in risk stratification.

     

Sex-based differences in cardiac resynchronization therapy and implantable cardioverter defibrillator therapies: effectiveness and use

With the rapid advancements in heart failure device therapy, many physicians now use these devices in everyday clinical practice. However, questions remain regarding the clinical benefit of these therapies in different patient subgroups. Since the majority of patients enrolled in device trials are white men, extrapolating the data to specific patient subpopulations becomes important. Specifically, the question of clinical outcomes in women with implantable device therapy for prevention of sudden cardiac death and management of heart failure is an important clinical issue. In this article, we review the data on survival and clinical outcomes with heart failure device therapy (implantable cardioverter defibrillators [ICDs] and cardiac resynchronization therapy [CRT]) and analyze the results from clinical trials for any differences in outcomes based on gender. Even though women are a significantly under-represented population with regard to clinical investigation and utilization of heart failure devices, they still derive the same morbidity and mortality benefits compared to men. Specifically, ICD devices confer the same rates of sudden cardiac death prevention, and CRT devices improve CHF morbidity and mortality at rates comparable to those found in men. These results support equal use of ICDs and CRT in men and women.     

Wie viele Elektroden braucht der ICD?

In addition to secondary prevention of sudden cardiac death (SCD), the number of cardioverter defibrillator implantations (ICD) for primary prevention is increasing. An indication for primary prevention of SCD is supported by results of the MADIT II, Companion and SCD-HeFT trials. The main risk factor for SCD is the reduced left ventricular function (LVEF < or = 35%). For selecting the appropriate ICD device and the number of leads, several clinical parameters are important. For the primary prevention of SCD a single-lead VVI ICD is usually sufficient. In case of AV conduction delay and symptomatic heart failure with a prolonged QRS duration a biventricular ICD device is preferred in favor of a ventricular resynchronization. The use of a dual-chamber device should be limited to sinus nodal disease and better discrimination capabilities for slow ventricular tachycardias.