Risk Stratification and Prevention of Sudden Death in Patients with Heart Failure

For almost the past decade, recommendations for the use of implantable cardioverter defibrillators (ICDs) for primary prevention of sudden cardiac death have been based upon the left ventricular ejection fraction (LVEF). Current guidelines recommend an ICD for heart failure patients with LVEF ≤35% and NYHA functional class of II or III; however, because the majority of heart failure patients who qualify for ICD implantation based on these criteria will never have an event requiring ICD therapy over several years of follow-up, additional methods of risk stratification for sudden death are clearly needed. Additionally, most of the nearly 300,000 cardiac arrests that occur each year occur in patients without heart failure or significant left ventricular dysfunction. To improve the identification of patients at risk for sudden death, several criteria other than ejection fraction have been proposed and studied. Markers of autonomic tone, including heart rate turbulence and QT dynamicity, have shown some ability to predict total mortality but not arrhythmic events. Microvolt T-wave alternans testing was initially thought to be highly predictive of life-threatening arrhythmias, but prospective large sub-studies of the MADIT II and SCD-HeFT trials have failed to show a predictive value for T-wave alternans testing. Newer markers for risk are based upon the detection of myocardial fibrosis, which forms the substrate for re-entrant and malignant ventricular tachyarrhythmias. Markers of collagen turnover or quantification of myocardial scar by MRI may hold the best promise for identifying patients at highest risk for sudden cardiac death and may also identify patients at high risk but with an ejection fraction above 35%, who are not currently recommended for ICD implantation.     

Implantable cardioverter defibrillator utilization based on discharge diagnoses from Medicare and managed care patients

INTRODUCTION: Implantable cardioverter defibrillators (ICDs) have become an accepted therapy for patients at high risk of sudden cardiac death. To assess the current utilization of this therapy, we estimated the number of patients at risk of sudden death using an historical claims-based study and compared these results to current ICD usage volumes. METHODS AND RESULTS: Managed care and Medicare databases (claims related to 4.6 million covered U.S. lives during a 12-month period) were analyzed to identify patients who had either a primary or secondary diagnosis of ventricular tachycardia, ventricular fibrillation, ventricular flutter, or cardiac arrest. These patients were further required to have a diagnosis code indicating a previous myocardial infarction or congestive heart failure. Patients who died during the study period or did not have medical insurance were excluded. In the base case scenario, 1,226 patients per million population were identified as potential ICD candidates. Sensitivity analyses reduced that value to a range from 736 to 1,140 ICD candidates per million population. Sensitivity factors considered included acute myocardial infarction, comorbidities, age, secondary ventricular tachycardia/ventricular fibrillation diagnosis, and varying degrees of left ventricular dysfunction. These results contrast with an ICD usage rate of 416 per million population in the United States and lower rates in other countries. CONCLUSION: This study suggests that, based on discharge diagnoses, many patients who could benefit from ICDs are not receiving this therapy. Diverse reasons for this underutilization should be addressed to improve access to, and appropriate use of, this therapy.     

Primary prevention of sudden cardiac death: indications for cardioverter-defibrillator implantation.

Sudden cardiac death accounts for 400,000 to 450,000 deaths annually in Europe and in the United States. In patients with previous life-threatening arrhythmia, several perspective, randomized, controlled studies have demonstrated that implantable cardioverter-defibrillator (ICD) therapy is superior to the best antiarrhythmic therapy in prolonging survival. Furthermore, in a stratified-risk population with coronary artery disease, left ventricular ejection fraction < or = 35%, non-sustained ventricular arrhythmias, and inducible ventricular tachycardia, the ICD supports the class I level of recommendation by the guidelines published in 1998. The American College of Cardiology, American Heart Association, and North American Society of Pacing and Electrophysiology have updated the 1998 guidelines on the implantation of arrhythmia devices including in a class IIa level of recommendation also patients with a previous Q wave myocardial infarction and left ventricular ejection fraction < or = 30%, independently of their arrhythmic risk profile. In the recent years several randomized studies assessed the role of ICD treatment for primary prevention of sudden cardiac death and total mortality reduction in high-risk groups of patients with ischemic and non-ischemic dilated cardiomyopathy, with special reference to those with heart failure and ventricular dysfunction. This article reviews those trials that have resulted in defining indications for ICD, and that will expand its use in the future.     

The implantable cardioverter-defibrillator and hypertrophic cardiomyopathy. Experience at three centers

INTRODUCTION AND OBJECTIVES: Although implantable cardioverter-defibrillators (ICDs) are recommended for high-risk patients with hypertrophic cardiomyopathy (HCM), there is no agreement on their general use. Moreover, little information is available on ICD use in this setting in Spain. Our aims were to describe the characteristics of HCM patients who received ICDs at three hospitals in Spain, and to study indications for device implantation and the results of follow-up in device users. METHODS: We evaluated risk factors for sudden death in HCM patients with ICDs, including family history of sudden death, recurrent syncope, maximum wall thickness > or =30 mm, left ventricular outflow pressure gradient >30 mmHg, abnormal blood pressure response to exercise, and nonsustained ventricular tachycardia. During regular follow-up, appropriate and inappropriate administration of ICD therapy was recorded. RESULTS: Of 726 HCM patients, 45 (6.2%) had an ICD (mean age 43 [20] years). The proportion of patients with ICDs at the three centers studied was highly variable despite patients' clinical characteristics being similar. The indication for implantation was primary prevention in 27 patients and secondary prevention in 18. During follow-up (median 32 months), ICD therapy was administered appropriately in 10 (22.0%) patients (in nine, as secondary prevention and, in one, as primary prevention). The annual appropriate ICD therapy rate was 11.1% for secondary prevention and 1.6% for primary prevention. Two patients received an ICD to treat ventricular fibrillation and eight, to treat sustained ventricular tachycardia. The only significant predictor of appropriate ICD therapy was a history of sustained ventricular tachycardia or ventricular fibrillation (hazard ratio =13.3, P=.014). CONCLUSIONS: The percentage of HCM patients undergoing ICD implantation at Spanish hospitals was highly variable, possibly due to different selection criteria. When used as secondary prevention, ICD therapy was administered appropriately in a high proportion of cases (50% in 3 years).     

The wearable cardioverter-defibrillator vest: Indications and ongoing questions

Multiple clinical trials have demonstrated the efficacy of implantable cardioverter-defibrillators (ICDs) for the prevention of sudden cardiac death (SCD) among specific high-risk populations. However, it remains unclear how to optimally treat those patients who are at elevated risk of cardiac arrest but are not among the presently identified groups proven to benefit from an ICD, are unable to tolerate surgical device implantation, or refuse invasive therapies. The wearable cardioverter-defibrillator (WCD) is an alternative antiarrhythmic device that provides continuous cardiac monitoring and defibrillation capabilities through a noninvasive, electrode-based system. The WCD has been shown to be highly effective at restoration of sinus rhythm in patients with a ventricular tachyarrhythmia, and one randomized trial using the WCD in patients with recent myocardial infarction at elevated risk for arrhythmic death reported a decrease in overall mortality despite no SCD mortality benefit. The current clinical indications for WCD use are varied and continue to evolve as experience with this technology increases.     

Treatment options for patients with coronary artery disease identified as high risk by T-wave alternans testing

Opinion statement Risk stratification for primary prevention of sudden cardiac death (SCD) remains a major challenge in cardiology. The utility of T-wave alternans (TWA) as a marker of risk of life-threatening ventricular tachycardia and fibrillation is supported by two decades of basic and clinical research. Both frequency-and time-domain methods have been developed, validated, and made available in clinical practice. A principal application of TWA testing has been to improve assessment of patients with depressed left ventricular ejection fraction (EF; ≤ 40%) who are considered for implantable cardioverter-defibrillator (ICD) implantation for primary prevention of SCD. TWA has been most useful in identifying patients who are unlikely to benefit from ICD therapy. Although patients with low EF should remain an important focus, the absolute number of SCD events is far greater among post-myocardial infarction patients with relatively preserved EF, even though the incidence of SCD in this population is low. Recent studies suggest that TWA testing is predictive in this population as well. Absolute quantification of TWA rather than binary classification into “normal” or “abnormal” appears to be valuable in more finely stratifying the magnitude of arrhythmic risk. Longitudinal testing may be warranted in certain populations, although the optimum interval remains to be determined. Combining TWA with noninvasive markers of autonomic function, such as heart rate turbulence, may further increase predictive accuracy. Future development will likely expand the role of TWA testing with routine exercise and ambulatory electrocardiographic monitoring to screen lower-risk populations and to guide medical and device-based therapy.     

ICD-Therapie zur Primärprävention des plötzlichen Herztods

ICD therapy represents a major advance in the treatment of patients with severely impaired left ventricular function after myocardial infarction. While an ICD implantation also remains a valuable option late (>5 years) after myocardial infarction, patients early after this event are at a competitive risk of arrhythmogenic and nonarrhythmogenic cardiac death. Prevention of sudden cardiac death in patients early after myocardial infarction, therefore, just converts the mode of death in a significant number of patients from sudden to nonsudden cardiac death (conversion theory). In patients with a left ventricular ejection fraction (LVEF) of ≤30% after myocardial infarction, implantation of the ICD should, therefore, be postponed to at least 30–40 days after the event. It is, however, not clear how the risk of sudden cardiac death should be approached during this post infarction phase. Similarly, it is not clear if patients with a reduced LVEF post infarction and additional specific risks (nonsustained ventricular tachycardia, atrial fibrillation, bundle branch block, etc.) beyond this single criterion may also benefit from ICD implantation and which risk factors may be relevant. In any case, ICD therapy should avoid right ventricular pacing and shock discharges whenever possible.     

Devices for the management of ventricular arrhythmias in cardiac failure

Heart failure is a common clinical syndrome with a high morbidity and mortality. Despite advances in medical treatment, death from dangerous ventricular arrhythmias is frequently implicated. Emerging evidence supports the use of the implantable cardioverter defibrillator for selected patients. This includes secondary prevention indications for patients who have survived life-threatening ventricular arrhythmias. In addition, patients who have not suffered spontaneous sustained ventricular arrhythmias, but who are at high risk for sudden arrhythmic death are starting to be recognized as candidates for ICD therapy. At present the only primary prevention indication with a good evidence base is the presence of inducible ventricular arrhythmias at electrophysiologic testing in patients with prior myocardial infarction, impaired left ventricular systolic function and non-sustained ventricular tachycardia on Holter monitoring. Studies planned or in progress are likely to expand further the role of device therapy in the treatment of patients with cardiac failure.     

Arrhythmogenic Right Ventricular Cardiomyopathy: Risk Stratification and Indications for Defibrillator Therapy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetically determined disease which predisposes to life-threatening ventricular arrhythmias. The main goal of ARVC therapy is prevention of sudden cardiac death (SCD). Implantable cardioverter defibrillator (ICD) is the most effective therapy for interruption of potentially lethal ventricular tachyarrhythmias. Despite its life-saving potential, ICD implantation is associated with a high rate of complications and significant impact on quality of life. Accurate risk stratification is needed to identify individuals who most benefit from the therapy. While there is general agreement that patients with a history of cardiac arrest or hemodynamically unstable ventricular tachycardia are at high risk of SCD and needs an ICD, indications for primary prevention remain a matter of debate. The article reviews the available scientific evidence and guidelines that may help to stratify the arrhythmic risk of ARVC patients and guide ICD implantation. Other therapeutic strategies, either alternative or additional to ICD, will be also addressed.     

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.     

Indications for Implantable Cardioverter-Defibrillator Placement in Ischemic Cardiomyopathy and after Myocardial Infarction

Dramatic reductions in the rate of sudden cardiac death due to use of implantable cardioverter-defibrillators (ICDs) have been well-established in several large randomized clinical trials including patients with left ventricular dysfunction after myocardial infarction. This article reviews the literature regarding ICD utilization in the postinfarction population, with a strong emphasis on recent clinical trials. The most current indications for, and timing of, ICD implantation postinfarction also are summarized.     

An update on implantable cardioverter-defibrillator guidelines

PURPOSE OF REVIEW: This review describes changes in indications for implantable cardioverter-defibrillator (ICD) implantation made in the American College of Cardiology, American Heart Association, and North American Society of Pacing and Electrophysiology 2002 update of the 1998 guideline for the implantation of cardiac pacemakers and antiarrhythmia devices. RECENT FINDINGS: Recent observational and clinical data support changes in the guidelines for ICD implantation to include patients with no structural heart disease and spontaneous ventricular tachycardia not amenable to other treatments; left ventricular ejection fractions of 0.30 or less at least 1 month after myocardial infarction and at least 3 months after coronary revascularization surgery (the Multicenter Automatic Defibrillator Implantation Trial II); syncope of unexplained origin or a family history of unexplained sudden cardiac death in association with typical or atypical right bundle branch block and ST-segment elevations (Brugada syndrome); and syncope in the setting of advanced structural heart disease when thorough invasive and noninvasive investigations have failed to define a cause. SUMMARY: With the completion of multiple important randomized clinical trials, the application of ICD technology continues to evolve. Indications have expanded from secondary to primary prevention. Most importantly, currently available data support the prophylactic use of ICDs in patients with coronary artery disease and poor left ventricular function. Further trial data are awaited to determine if the same benefits for survival and quality of life will be afforded to patients with nonischemic heart diseases and poor left ventricular function.     

Racial disparity in the utilization of implantable-cardioverter defibrillators among patients with prior myocardial infarction and an ejection fraction of <or=35%

Age-adjusted sudden cardiac death rates are highest for black patients compared with other racial groups. The prophylactic implantation of an implantable cardioverter-defibrillator (ICD) provides a significant reduction in sudden cardiac death and overall mortality in patients after myocardial infarctions with significant left ventricular systolic dysfunction. The purpose of this study was to determine whether black patients with left ventricular systolic dysfunction were less likely than white patients to receive ICDs for the primary prevention of sudden cardiac death. Data from the National Registry to Advance Heart Health (ADVANCENT) were analyzed to determine which patients with histories of myocardial infarctions and ejection fractions相似文献   

Prophylactic Implantation of Cardioverter Defibrillators in Idiopathic Nonischemic Cardiomyopathy for the Primary Prevention of Death: A Narrative Review

Implantable cardioverter defibrillator (ICD) therapy reduces sudden cardiac death rates and reduces mortality in patients with ischemic heart disease and low ejection fractions. One‐third of the deaths in patients with nonischemic cardiomyopathy are sudden. However, the efficacy of ICDs in the primary prevention of death in these patients is less clear. The most common cause of mortality in patients treated with ICDs is heart failure progression. ICD shocks can cause direct myocardial injury, fibrosis, inflammation, and adverse psychological outcomes, and these changes may contribute to the ventricular dysfunction in patients who already have a significantly depressed ejection fraction. We have reviewed the published randomized controlled trials and meta‐analysis of prophylactic ICD therapy in the primary prevention of death in patients with nonischemic cardiomyopathy. The individual randomized controlled trials do not report a statistically significant reduction of mortality unless the ICD treatment is added to cardiac resynchronization therapy, but the meta‐analysis did show a significant mortality reduction and favored ICD therapy in these patients. Medical management of many study participants was suboptimal, at least based on current guidelines. The patients with non‐ischemic cardiomyopathy have good outcomes with medical therapy, and ICD therapy in this relatively low‐risk population needs better selection criteria. Copyright © 2010 Wiley Periodicals, Inc.     

植入型心律转复除颤器对慢性心力衰竭心脏性猝死的一级预防

目的评价植入型心律转复除颤器（ICD）在慢性心力衰竭患者心脏性猝死一级预防中的治疗作用。方法对2005年1月至2008年12月符合ICD一级预防标准并植入ICD的患者进行随访。ICD的诊断设置室性心动过速（VT）、心室颤动（VF）两个工作区,治疗设置抗-tk,动过速起搏（ATP）、低能量同步转复（CV）和高能量除颤（DF）。术后患者常规给予抗心律失常药物。每3～6个月随访1次,利用程控仪获取ICD储存资料,了解患者心律失常发作情况以及ICD的诊断和治疗是否准确,及时调整相关参数并处理ICD故障。结果共随访了22例患者,平均随访（12．8±8．6）个月。共有10例患者记录到ICD治疗事件。10例患者ICD记录到持续性VT事件,其中由ATP终止6例,CV终止4例。4例患者有VF事件,均1次DF成功。2例ICD将快速心室率心房颤动（AF）识别为VF并进行放电治疗并转复房颤。结论ICD在慢性心力衰竭患者心脏性猝死一级预防中的治疗效果是肯定的,ICD联合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。     

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.     

Who should receive an implantable cardioverter-defibrillator after myocardial infarction?

Despite a decline in overall cardiovascular mortality, the incidence of sudden cardiac death (SCD) continues to rise. Patients who survive a myocardial infarction (MI) with depressed ejection fraction are at particularly high risk for SCD. The development of implantable cardioverter-defibrillators (ICDs) has revolutionized SCD prevention; however, despite the current fervor for device implantation, many unresolved questions remain about risk stratification in post-MI patients. This review presents the current indications and timing of ICD implantation for primary and secondary prevention of SCD after MI. Several conventional and investigational methods of risk stratification after MI, as well as current controversies regarding device implantation in specific patient populations, are also reviewed.     

The Timing of Implantable Cardioverter-Defibrillator Implantation in Patients with Heart Failure

Patients who survive a myocardial infarction (MI) are at increased risk of sudden death due to fatal ventricular arrhythmias. Implantable cardioverter-defibrillators (ICDs) reduce mortality in appropriately selected patients with heart failure and left ventricular dysfunction, regardless of etiology. Post hoc analyses from landmark trials have evaluated the effect of time (both since MI and duration of nonischemic cardiomyopathy) before ICD implantation on the efficacy of ICD therapy. Time remains a clinically important variable in the decision of if and when to implant an ICD. Future trials should focus on invasive and/or noninvasive risk stratification of patients with ischemic and nonischemic cardiomyopathy for better identification of those who would benefit from early ICD implantation, and those in whom a watch and wait approach is appropriate.     

ICD therapy for the prevention of sudden cardiac death in post-MI patients

Opinion statement Implantable cardioverter-defibrillators (ICDs) are unequivocally the treatment of choice for patients who have already experienced a near-fatal tachyarrhythmic event. Recently, studies have conclusively demonstrated that extending the benefits of ICD therapy to postinfarction patients with resultant left ventricular dysfunction results in dramatic additional lifesaving without the need for complex riskstratification procedures. The landmark Multicenter Automatic Defibrillator Implantation Trial II (MADIT II) shows that patients with reduced left ventricular function (ejection fraction < 30%) 1 month after a myocardial infarction should receive an ICD to prevent sudden cardiac death.     

Optimal Timing of Implantable Cardioverter‐Defibrillator Implantation After Myocardial Infarction: A Decision Analysis

ICD Implant Timing . Background: The optimal timing of implantable cardioverter defibrillator (ICD) placement for the primary prevention of sudden cardiac death after myocardial infarction (MI) remains unknown. Methods and Results: We developed a Markov model to investigate the optimal timing of ICD implantation after MI (no ICD, ICD at 60 days, 6 months, and 1 year) in patients who meet current guidelines. Estimates of arrhythmic death (baseline risk 6%, range 1–20% per year), nonarrhythmic death, and ICD efficacy were based upon MADIT‐II and other contemporary post‐MI clinical trials. We used both deterministic and stochastic modeling processes in our analysis. After 10 years follow‐up, the baseline probability of survival was higher in those treated with ICD implantation versus not (42% vs 30%, P < 0.001). Survival was highest with ICD implantation at 60 days versus 6 months versus 1 year: 42.4%, 42.3%, and 42.0% (P = 0.0028). ICD implantation at 60 days provided a mean incremental survival of 0.28 months and 0.84 months per patient (compared with implantation at 6 months and 1 year). In sensitivity analyses, patients’ competing risk for nonarrhythmic death was the primary determinant of benefit from ICD implantation. Overall, ICD implantation at 60 days resulted in the greatest life expectancy over a wide range of plausible nonarrhythmic and arrhythmic death rates. Conclusions: The benefits of early ICD implantation are modest when compared with delayed implantation at 6 months/1 year. Our results suggest that making sure a patient receives an ICD, when appropriate, may be more important than the timing of the implantation procedure. (J Cardiovasc Electrophysiol, Vol. pp. 791‐798, July 2010)