Cost-Effectiveness of a Microvolt T-Wave Alternans Screening Strategy for Implantable Cardioverter-Defibrillator Placement in the MADIT-II–Eligible Population

Improving the Methods for the Economic Evaluation of Medical Devices

Medical devices (MDs) have distinctive features, such as incremental innovation, dynamic pricing, the learning curve and organisational impact, that need to be considered when they are evaluated. This paper investigates how MDs have been assessed in practice, in order to identify methodological gaps that need to be addressed to improve the decision-making process for their adoption. We used the Consolidated Health Economic Evaluation Reporting Standards (CHEERS) checklist supplemented by some additional categories to assess the quality of reporting and consideration of the distinctive features of MDs. Two case studies were considered: transcatheter aortic valve implantation (TAVI) representing an emerging technology and implantable cardioverter defibrillators (ICDs) representing a mature technology. Economic evaluation studies published as journal articles or within Health Technology Assessment reports were identified through a systematic literature review. A total of 19 studies on TAVI and 41 studies on ICDs were analysed. Learning curve was considered in only 16% of studies on TAVI. Incremental innovation was more frequently mentioned in the studies of ICDs, but its impact was considered in only 34% of the cases. Dynamic pricing was the most recognised feature but was empirically tested in less than half of studies of TAVI and only 32% of studies on ICDs. Finally, organisational impact was considered in only one study of ICDs and in almost all studies on TAVI, but none of them estimated its impact. By their very nature, most of the distinctive features of MDs cannot be fully assessed at market entry. However, their potential impact could be modelled, based on the experience with previous MDs, in order to make a preliminary recommendation. Then, well-designed post-market studies could help in reducing uncertainties and make policymakers more confident to achieve conclusive recommendations. © 2017 The Authors. Health Economics published by John Wiley & Sons, Ltd.

Economic evaluations of implantable cardioverter defibrillators: a systematic review

The aim of this paper was to review the cost-effectiveness studies of implantable cardioverter defibrillators (ICD) for primary or secondary prevention of sudden cardiac death (SCD). A systematic review of the literature published in English or Spanish was performed by electronically searching MEDLINE and MEDLINE in process, EMBASE, NHS-EED, and EconLit. Some keywords were implantable cardioverter defibrillator, heart failure, heart arrest, myocardial infarction, arrhythmias, syncope, sudden death. Selection criteria were the following: (1) full economic evaluations published after 1995, model-based studies or alongside clinical trials (2) that explored the cost-effectiveness of ICD with or without associated treatment compared with placebo or best medical treatment, (3) in adult patients for primary or secondary prevention of SCD because of ventricular arrhythmias. Studies that fulfilled these criteria were reviewed and data were extracted by two reviewers. The methodological quality of the studies was assessed and a narrative synthesis was prepared. In total, 24 studies were included: seven studies on secondary prevention and 18 studies on primary prevention. Seven studies were performed in Europe. For secondary prevention, the results showed that the ICD is considered cost-effective in patients with more risk. For primary prevention, the cost-effectiveness of ICD has been widely studied, but uncertainty about its cost-effectiveness remains. The cost-effectiveness ratios vary between studies depending on the patient characteristics, methodology, perspective, and national settings. Among the European studies, the conclusions are varied, where the ICD is considered cost-effective or not dependent on the study.

Implantable cardioverter defibrillators for the treatment of arrhythmias and cardiac resynchronisation therapy for the treatment of heart failure: systematic review and economic evaluation

BACKGROUND

This assessment updates and expands on two previous technology assessments that evaluated implantable cardioverter defibrillators (ICDs) for arrhythmias and cardiac resynchronisation therapy (CRT) for heart failure (HF).

OBJECTIVES

To assess the clinical effectiveness and cost-effectiveness of ICDs in addition to optimal pharmacological therapy (OPT) for people at increased risk of sudden cardiac death (SCD) as a result of ventricular arrhythmias despite receiving OPT; to assess CRT with or without a defibrillator (CRT-D or CRT-P) in addition to OPT for people with HF as a result of left ventricular systolic dysfunction (LVSD) and cardiac dyssynchrony despite receiving OPT; and to assess CRT-D in addition to OPT for people with both conditions.

DATA SOURCES

Electronic resources including MEDLINE, EMBASE and The Cochrane Library were searched from inception to November 2012. Additional studies were sought from reference lists, clinical experts and manufacturers' submissions to the National Institute for Health and Care Excellence.

REVIEW METHODS

Inclusion criteria were applied by two reviewers independently. Data extraction and quality assessment were undertaken by one reviewer and checked by a second. Data were synthesised through narrative review and meta-analyses. For the three populations above, randomised controlled trials (RCTs) comparing (1) ICD with standard therapy, (2) CRT-P or CRT-D with each other or with OPT and (3) CRT-D with OPT, CRT-P or ICD were eligible. Outcomes included mortality, adverse events and quality of life. A previously developed Markov model was adapted to estimate the cost-effectiveness of OPT, ICDs, CRT-P and CRT-D in the three populations by simulating disease progression calculated at 4-weekly cycles over a lifetime horizon.

RESULTS

A total of 4556 references were identified, of which 26 RCTs were included in the review: 13 compared ICD with medical therapy, four compared CRT-P/CRT-D with OPT and nine compared CRT-D with ICD. ICDs reduced all-cause mortality in people at increased risk of SCD, defined in trials as those with previous ventricular arrhythmias/cardiac arrest, myocardial infarction (MI) > 3 weeks previously, non-ischaemic cardiomyopathy (depending on data included) or ischaemic/non-ischaemic HF and left ventricular ejection fraction ≤ 35%. There was no benefit in people scheduled for coronary artery bypass graft. A reduction in SCD but not all-cause mortality was found in people with recent MI. Incremental cost-effectiveness ratios (ICERs) ranged from £14,231 per quality-adjusted life-year (QALY) to £29,756 per QALY for the scenarios modelled. CRT-P and CRT-D reduced mortality and HF hospitalisations, and improved other outcomes, in people with HF as a result of LVSD and cardiac dyssynchrony when compared with OPT. The rate of SCD was lower with CRT-D than with CRT-P but other outcomes were similar. CRT-P and CRT-D compared with OPT produced ICERs of £27,584 per QALY and £27,899 per QALY respectively. The ICER for CRT-D compared with CRT-P was £28,420 per QALY. In people with both conditions, CRT-D reduced the risk of all-cause mortality and HF hospitalisation, and improved other outcomes, compared with ICDs. Complications were more common with CRT-D. Initial management with OPT alone was most cost-effective (ICER £2824 per QALY compared with ICD) when health-related quality of life was kept constant over time. Costs and QALYs for CRT-D and CRT-P were similar. The ICER for CRT-D compared with ICD was £27,195 per QALY and that for CRT-D compared with OPT was £35,193 per QALY.

LIMITATIONS

Limitations of the model include the structural assumptions made about disease progression and treatment provision, the extrapolation of trial survival estimates over time and the assumptions made around parameter values when evidence was not available for specific patient groups.

CONCLUSIONS

In people at risk of SCD as a result of ventricular arrhythmias and in those with HF as a result of LVSD and cardiac dyssynchrony, the interventions modelled produced ICERs of < £30,000 per QALY gained. In people with both conditions, the ICER for CRT-D compared with ICD, but not CRT-D compared with OPT, was < £30,000 per QALY, and the costs and QALYs for CRT-D and CRT-P were similar. A RCT comparing CRT-D and CRT-P in people with HF as a result of LVSD and cardiac dyssynchrony is required, for both those with and those without an ICD indication. A RCT is also needed into the benefits of ICD in non-ischaemic cardiomyopathy in the absence of dyssynchrony.

STUDY REGISTRATION

This study is registered as PROSPERO number CRD42012002062.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Cost-effectiveness of implantable cardioverter-defibrillator in today's world

The implantable cardioverter-defibrillator (ICD) is an example of an effective intervention with high up-front costs and delayed benefits. It has become a proven and well-accepted therapy not only for secondary but also for primary prevention of sudden cardiac death in patients with ischemic and non-ischemic heart disease. In recent years, the international guidelines have extended the indications to the prophylactic ICD, increasing the number of eligible patients and, together, the financial challenges of a widespread implementation. In this article, we review the available economic tools that can help address the ICD cost issue. We think that the awareness of such knowledge may facilitate dialogues between physicians, administrators and policy-makers, and help foster rational decision making.

The cost-effectiveness of primary prophylactic implantable defibrillator therapy in patients with ischaemic or non-ischaemic heart disease: a European analysis

AIMS

It remains unclear whether primary prophylactic implantable cardioverter-defibrillator (ICD) therapy is cost-effective compared with a 'no ICD strategy' in the European health care setting. We performed a cost-effectiveness analysis for a cohort of patients with a left ventricular ejection fraction <40% and ischaemic or non-ischaemic heart disease.

METHODS AND RESULTS

A Markov decision analytic model was used to evaluate long-term survival, quality-adjusted life years (QALYs), and lifetime costs for a cohort of patients with a reduced left ventricular function without previous arrhythmias, managed with a prophylactic ICD. Input data on effectiveness were derived from a meta-analysis of primary prophylactic ICD-only therapy randomized trials, from a prospective cohort study of ICD patients, from a health care utilization survey, and from the literature. Input data on costs were derived from a micro-cost analysis. Data on quality-of-life were derived from the literature. Deterministic and probabilistic sensitivity analysis was performed to assess the uncertainty. Probabilistic sensitivity analysis demonstrated a mean lifetime cost of €50 685 ± €4604 and 6.26 ± 0.64 QALYs for patients in the 'no ICD strategy'. Patients in the 'ICD strategy' accumulated €86 759 ± €3343 and an effectiveness of 7.08 ± 0.71 QALYs yielding an incremental cost-effectiveness ratio of €43 993/QALY gained compared with the 'no ICD strategy'. The probability that ICD therapy is cost-effective was 65% at a willingness-to-pay threshold of €80 000/QALY.

CONCLUSION

Our results suggest that primary prophylactic ICD therapy in patients with a left ventricular ejection fraction <40% and ischaemic or non-ischaemic heart disease is cost-effective in the European setting.

Do Beta-blockers impact microvolt T-wave alternans testing in patients at risk for ventricular arrhythmias? A meta-analysis

INTRODUCTION

Results of microvolt T-wave alternans (MTWA) studies vary and may be influenced by whether beta-blocker therapy was withheld prior to MTWA assessment. We conducted a meta-analysis of the predictive value of MTWA screening for ventricular arrhythmic events in primary prevention patients with left ventricular dysfunction and examined whether results differed depending upon whether beta-blocker use was withheld prior to MTWA testing.

METHODS AND RESULTS

Prospective studies that evaluated whether MTWA predicted ventricular arrhythmic events published between January 1980 and September 2008 were identified. Summary estimates for the predictive value of MTWA were derived with random-effects models. Nine studies involving 3,939 patients were identified. Overall, an abnormal MTWA (positive and indeterminate) test was associated with an almost 2-fold increased risk for arrhythmic events (pooled RR = 1.95, 95% CI: 1.29-2.96; P = 0.002). However, significant heterogeneity across studies was observed (P = 0.024). In the 4 studies in which beta-blocker therapy was not withheld prior to MTWA assessment, an abnormal MTWA test was associated with a 5-fold increased risk for arrhythmic events (pooled RR = 5.39, 95% CI: 2.68-10.84; P < 0.001) and was robust to sensitivity analyses. In contrast, the association was much weaker in those studies where the use of beta-blocker therapy was withheld prior to MTWA testing (pooled RR = 1.40, 95% CI: 1.06-1.84; P = 0.02).

CONCLUSIONS

In primary prevention patients with left ventricular dysfunction, the predictive power of MTWA varied widely, based on whether beta-blocker therapy was withheld prior to its assessment. This observation may explain the inconsistent results of MTWA studies in this population.

Does Medicare Have an Implicit Cost-Effectiveness Threshold?

Background. Despite the huge cost of the program, the Centers for Medicare and Medicaid Services (CMS) has maintained a policy that cost-effectiveness is not considered in national coverage determinations (NCDs). Objective. To assess whether an implicit cost-effectiveness threshold exists and to determine if economic evidence has been considered in previous NCDs. Methods. A literature search was conducted to identify estimates of cost-effectiveness relevant to each NCD from 1999—2007 (n = 103). The economic evaluation that best represented each coverage decision was included in a review of the cost-effectiveness of medical interventions considered in NCDs. Results. Of the 64 coverage decisions determined to have a corresponding cost-effectiveness estimate, 49 were associated with a positive coverage decision and 15 with a noncoverage decision. Of the positive decisions, 20 were associated with an economic evaluation that estimated the intervention to be dominant (costs less and was more effective than the alternative), 12 with an incremental cost-effectiveness ratio (ICER) of less than $50,000, 8 with an ICER greater than $50,000 but less than $100,000, and 9 with an ICER greater than $100,000. Fourteen of the sample of 64 decision memos cited or discussed cost-effectiveness information. Conclusions. CMS is covering a number of interventions that do not appear to be cost-effective, suggesting that resources could be allocated more efficiently. Although the authors identified several instances where cost-effectiveness evidence was cited in NCDs, they found no clear evidence of an implicit threshold.

Healthcare rationing by proxy: cost-effectiveness analysis and the misuse of the $50,000 threshold in the US

The application of cost-effectiveness analysis in healthcare has become commonplace in the US, but the validity of this approach is in jeopardy unless the proverbial $US50,000 per QALY benchmark for determining value for money is updated for the 21st century. While the initial aim of this article was to review the arguments for abandoning the $US50,000 threshold, it quickly turned to questioning whether we should maintain a fixed threshold at all. Our consideration of the relevance of thresholds was framed by two important historical considerations. First, cost-effectiveness analysis was developed for a resource allocation exercise where a threshold would be determined endogenously by maximizing a fixed budget across all possible interventions and not for piecemeal evaluation where a threshold needs to be set exogenously. Second, the foundations of the $US50,000 threshold are highly dubious, so it would be unacceptable merely to adjust for inflation or current clinical practice. Upon consideration of both sides of the argument, we conclude that the arguments for abandoning the concept for maintaining a fixed threshold outweigh those for keeping one. Furthermore, we document a variety of reasons why a threshold needs to vary in the US, including variations across payer, over time, in the true budget impact of interventions and in the measurement of the effectiveness of interventions. We conclude that while a threshold may be needed to interpret the results of a cost-effectiveness analysis, that threshold must vary across payers, populations and even procedures.

Expenditure and value for money: the challenge of implantable cardioverter defibrillators

Many technology-driven interventions entail considerable financial cost, raising affordability issues. The implantable cardioverter defibrillator (ICD) is a case of an effective primary prevention intervention with high initial costs that is capable of delivering long-term population benefits. At first glance, such interventions may provoke diffidence, if not active resistance, due to the financial burdens which inevitably accompany their widespread adoption. In this article, we review the available economic tools that can help address the ICD cost issue. We think awareness of such knowledge may facilitate dialogues between physicians, administrators and policymakers, and help foster rational decision-making.

Microvolt T-wave alternans and the selective use of implantable cardioverter defibrillators for primary prevention: A cost-effectiveness study

Objectives:Implantable cardioverter defibrillators (ICDs) are an effective but expensive treatment for the prevention of sudden cardiac deaths in patients with severe left-ventricular dysfunction. Recent studies suggest that microvolt T-wave alternans (MTWA) predicts mortality and severe arrhythmic events in this population. However, the impact of MTWA on ICD cost-effectiveness is unknown.

Methods:A Markov decision-analysis model evaluated three treatment strategies for primary prevention in patients with severe left-ventricular dysfunction: (i) medical therapy for all; (ii) ICD therapy for all; and (iii) selective ICD therapy based on non-negative (positive or indeterminate) MTWA test results. Incremental cost-effectiveness ratios (ICER) were calculated from the perspective of a third party payer using a 10-year time horizon. Sensitivity analyses examined the robustness of the estimates.

Results:A treatment strategy involving ICD therapy in all patients was associated with an ICER of $121,800/quality-adjusted life-year (QALY) compared with medical therapy, whereas a treatment strategy involving the selective use of ICDs based on MTWA test results was associated with an ICER of $108,900/QALY compared with medical therapy. Sensitivity analyses suggest that, under most scenarios, the selective use of ICDs based on MTWA results does not decrease the ICER to below $100,000/QALY.

Conclusion:MTWA only marginally improves the cost-effectiveness of ICDs for primary prevention in patients with severe left-ventricular dysfunction. There remains a need for improved means to effectively identify which patients will derive the greatest benefit from ICD implantation.

The ABCD (Alternans Before Cardioverter Defibrillator) Trial: strategies using T-wave alternans to improve efficiency of sudden cardiac death prevention

OBJECTIVES

Because risk stratification with electrophysiological study (EPS) improves efficiency but is invasive, we sought to determine whether noninvasive microvolt T-wave alternans (MTWA) testing could identify patients who benefit from implantable cardioverter-defibrillators (ICDs) as well as EPS.

BACKGROUND

Prevention of sudden cardiac death on the basis of left ventricular ejection fraction (LVEF) alone is inefficient, because most ICDs never deliver therapy.

METHODS

The ABCD (Alternans Before Cardioverter Defibrillator) trial is a multicenter prospective study that enrolled patients with ischemic cardiomyopathy (LVEF < or =0.40) and nonsustained ventricular tachycardia. All patients underwent MTWA and EPS. ICDs were mandated if either test was positive.

RESULTS

Of 566 patients followed for a median of 1.9 years, 39 (7.5%) met the primary end point of appropriate ICD discharge or sudden death at 1 year. As hypothesized, primary analysis showed that MTWA achieved 1-year positive (9%) and negative (95%) predictive values that were comparable to EPS (11% and 95%, respectively). In addition, secondary analysis showed that at the pre-specified 1-year end point, event rates were significantly higher in patients with both a positive MTWA-directed strategy (hazard ratio: 2.1, p = 0.03) and a positive EPS-directed strategy (hazard ratio: 2.4, p = 0.007). Moreover, the event rate in patients with both negative MTWA test and EPS was lower than in those with 2 positive tests (2% vs. 12%; p = 0.017).

CONCLUSIONS

The ABCD study is the first trial to use MTWA to guide prophylactic ICD insertion. Risk stratification strategies using noninvasive MTWA versus invasive EPS are comparable at 1 year and complementary when applied in combination. Strategies employing MTWA, EPS, or both might identify subsets of patients least likely to benefit from ICD insertion. (Study to Compare TWA Test and EPS Test for Predicting Patients at Risk for Life-Threatening Heart Rhythms [ABCD Study]; NCT00187291).

T-wave alternans: reviewing the clinical performance, understanding limitations, characterizing methodologies

Accurate recognition of individuals at higher immediate risk of sudden cardiac death (SCD) is still an open question. The fortuitous nature of acute cardiovascular events just does not seem to fit the well-known model of ventricular tachycardia/fibrillation induction in a static arrhythmogenic substrate by a synchronous trigger. On the mechanism of SCD, a dynamical electrical instability would better explain the rarity of the simultaneous association of a correct trigger and an appropriate cardiac substrate. Several studies have been conducted trying to measure this cardiac electrical instability (or any valid surrogate) in an ECG beat stream. Among the current possible candidates we can number QT prolongation, QT dispersion, late potentials, T-wave alternans (TWA), and heart rate turbulence. This article reviews the particular role of TWA in the current cardiac risk stratification scenario. TWA findings are still heterogeneous, ranging from very good to nearly null prognostic performance depending on the clinical population observed and clinical protocol in use. To fill the current gaps in the TWA base of knowledge, practitioners, and researchers should better explore the technical features of the several technologies available for TWA evaluation and pay greater attention to the fact that TWA values are responsive to several factors other than medications. Information about the cellular and subcellular mechanisms of TWA is outside the scope of this article, but the reader is referred to some of the good papers available on this topic whenever this extra information could help the understanding of the concepts and facts covered herein.

A prognostic index relating 24-hour ambulatory blood pressure to cardiac events in ischemic cardiomyopathy following defibrillator implantation

BACKGROUND

We assessed the role of left ventricular ejection fraction and of ambulatory blood pressure monitoring (ABPM) to predict cardiac death and heart failure in patients with defibrillator fulfilling MADIT II criteria. ABPM variables assessed included: mean 24 hours diastolic and systolic blood pressure, mean 24 hours heart rate, and pulse pressure.

METHODS

We studied 105 consecutive patients (age 67 +/- 11), all with a defibrillator and ejection fraction <or= 30%).

RESULTS

At 1-year follow-up, there were 29 events (25%), three cardiac deaths, and 26 hospitalizations for heart failure. Age, creatinine, mean 24 hours diastolic blood pressure, and mean 24 hours systolic blood pressure (but not ejection fraction) were associated with events. A prognostic index (PI) was built by age and ABPM variables, according to the formula (120--age) + (mean 24 hours diastolic blood pressure + mean 24 hours systolic blood pressure). Receiver operating characteristic curves showed the best cutoff for PI = 220 (sensitivity 81%, specificity 71%, positive predictive value 56%, negative predictive value 88%). Cox regression analysis confirmed the significant association between lower PI (< 220) and clinical events (HR 4.8, 95% CI 1.8-12.3, P = 0.0001 for PI). Overall, 12% of patients with high PI values (>or= 220 n = 71) had clinical events at 12-month follow-up, compared with 61% of patients with low PI (< 220 n = 34) (P < 0.0001).

CONCLUSION

The PI built by mean 24 hours diastolic and systolic blood pressure and age could be a simple method to stratify risk of cardiac death and acute heart failure in MADIT II patients, in whom ejection fraction, uniformly depressed, is not predictive.

Clinical and arrhythmic outcomes after implantation of a defibrillator for primary prevention of sudden death in patients with post-myocardial infarction cardiomyopathy: The Survey to Evaluate Arrhythmia Rate in High-risk MI patients (SEARCH-MI)

Aims

To evaluate clinical and arrhythmic outcomes in post-infarction cardiomyopathy patients implanted with a defibrillator (ICD) for primary prevention of sudden death.

Methods and results

The SEARCH-MI registry is a European multi-centre, prospective, observational study enrolling patients after myocardial infarction, chronic left ventricular dysfunction and an ICD implanted for primary prevention of sudden death. Data on 556 patients with at least one recorded follow-up are presented. Survey to Evaluate Arrhythmia Rate in High-risk MI (SEARCH-MI) patients were sicker than those enrolled in MADIT-II with higher New York Heart Association class and left bundle branch block. Total mortality was 10.4%. Close to one-third (30%) of patients experienced episodes of sustained ventricular arrhythmia. One-quarter (23%) received at least one appropriate therapy and 10% inappropriate therapy. Gender (25% males vs. 5% females, P = 0.0009) and history of non-sustained ventricular tachycardia (24% with vs. 18% without P = 0.037) were predictive of appropriate ventricular therapy.

Conclusion

SEARCH-MI represents the current clinical management of post-MI patients with left ventricular dysfunction indicated to defibrillator implant for primary prevention. European routine clinical practice was influenced by landmark trials and guidelines which impacted on the implantation of cardiac resynchronization therapy in over 25% of such patients. Non-sustained ventricular tachycardia identifies subjects with a higher incidence of appropriate ICD therapy.

Impact of Age and Medical Comorbidity on the Effectiveness of Implantable Cardioverter-Defibrillators for Primary Prevention

Background— Although implantable cardioverter-defibrillators (ICDs) reduce mortality in primary prevention patients with left ventricular systolic dysfunction, recent studies have questioned their overall role in clinical practice, especially in older patients and those with major comorbid conditions.

Methods and Results— In a prospective cohort of 965 patients with ischemic and nonischemic cardiomyopathies (ejection fraction ≤35%) and no prior ventricular arrhythmias, we compared long-term mortality in patients who did (n=494 [51%]) and did not receive ICDs over a mean follow-up period of 34�16 months. Using a landmark analysis, multivariable Cox proportional hazards models that included propensity scores for ICD implantation assessed the relationship between ICD therapy and mortality in the entire cohort and by age and the presence of major comorbid conditions. Data from these analyses were then used as inputs in a Markov model to generate incremental cost-effectiveness ratios for ICD therapy. Patients who received ICDs were similar in age and prevalence of most major comorbid conditions, including symptomatic heart failure. After multivariable adjustment, ICD therapy was associated with a 31% lower risk for all-cause mortality (adjusted hazard ratio, 0.69; 95% CI, 0.50 to 0.96; P =0.03). The relationship between ICD therapy and lower all-cause mortality was consistent after stratification by age (<65, 65 to 74, and ≥75), ischemic etiology, ejection fraction (>25% versus ≤25%), and the presence of major comorbid conditions (probability values for all interactions >0.05). Incremental cost-effectiveness ratios for ICD therapy were similar between patients aged ≥75 years and younger patients but rose slightly in those with multiple comorbid conditions.

Conclusions— Routine use of ICDs in primary prevention patients with left ventricular systolic dysfunction was associated with lower all-cause mortality, even among older patients and those with major comorbid conditions. Although their use needs to be individualized, our findings suggest that these groups should not be routinely excluded from ICD treatment.

Predicting the need for an implantable cardioverter defibrillator using cardiac metaiodobenzylguanidine activity together with plasma natriuretic peptide concentration or left ventricular function

Despite widespread use of implantable cardioverter defibrillators (ICDs), their cost and the fact that only a certain group of patients fully benefits from the devices require appropriate risk stratification of patients. This study investigated whether altered cardiac autonomic function is associated with the occurrence of ICD discharge or lethal cardiac events.

METHODS

Fifty-four ICD-treated patients were prospectively followed after assessment of cardiac metaiodobenzylguanidine (MIBG) activity, quantified as the heart-to-mediastinum ratio (HMR), plasma concentration of brain natriuretic peptide (BNP), and left ventricular ejection fraction (LVEF). Patients were divided into 2 groups based on the presence (group A, n = 21) or absence (group B, n = 33) of appropriate ICD discharge during a 15-mo period.

RESULTS

Group A had a significantly lower level of MIBG activity and a higher plasma BNP level than did group B. Univariate analysis revealed BNP level, any medication, and late HMR to be significant predictors, and multivariate analysis showed late HMR to be an independent predictor. An HMR of less than 1.95 with a plasma BNP level of more than 187 pg/mL or an LVEF of less than 50% had significantly increased power to predict ICD shock: positive predictive values, 82% (HMR + BNP) and 58% (HMR + LVEF); negative predictive values, 73% (HMR + BNP) and 77% (HMR + LVEF); sensitivities, 45% (HMR + BNP) and 67% (HMR + LVEF); and specificities, 94% (HMR + BNP) and 70% (HMR + LVEF).

CONCLUSION

When combined with plasma BNP concentration or cardiac function, cardiac MIBG activity is closely related to lethal cardiac events and can be used to identify patients who would benefit most from an ICD.

Sudden Cardiac Death: Epidemiology, Mechanisms, and Therapy

Sudden cardiac death is a major public health problem affecting 500,000 patients annually in the United States alone. The major risk factor for sudden cardiac death is the presence of coronary artery disease, usually in the setting of reduced ejection fraction. Globally, the incidence is expected to rise sharply as the prevalence of coronary artery disease and heart failure continue to increase. However, sudden cardiac death is a heterogeneous condition and may be caused by acute ischemia, structural defects, myocardial scar, and/or genetic mutations. Sudden death may occur even in a grossly normal heart. Beta-blockers can reduce the risk of sudden cardiac death, while implantable cardioverter defibrillators are effective at terminating malignant arrhythmias. Ejection fraction remains the major criterion to stratify patients for defibrillator implantation but this strategy alone is insensitive and nonspecific. Novel clinical, electrophysiologic, and genetic markers have been identified that may increase precision in patient selection for primary prevention therapy. This review discusses the epidemiology, mechanisms, etiologies, therapies, treatment guidelines, and future directions in the management of sudden cardiac death.

Global Cost-effectiveness of Cataract Surgery

OBJECTIVE

To determine the cost-effectiveness of cataract surgery worldwide and to compare it with the cost-effectiveness of comparable medical interventions.

DESIGN

Meta-analysis.

PARTICIPANTS

Approximately 12,000 eyes in the studies selected.

METHODS

Articles were identified by searching the literature using the phrase cataract surgery, in combination with the terms cost, cost-effectiveness, and cost-utility. Terms used for the comparable medical interventions search included epileptic surgery, hip arthroplasty, knee arthroplasty, carpal tunnel surgery, and defibrillator implantation. The search was restricted to the years 1995 through 2006. Cataract surgery costs were converted to 2004 United States dollars (US$). Cost-utility was calculated using: (1) costs discounted at 3% for 12 years with a discounted quality-adjusted life years (QALY) gain of 1.25 years, and (2) costs discounted at 3% for 5 years with a discounted QALY gain of 0.143 years. The Cataract Surgery Affordability Index (CSAI) for each country was calculated by dividing the cost of cataract surgery by the gross national income per capita for the year 2004.

MAIN OUTCOME MEASURES

Cost-utility in 2004 US$/QALY and affordability of cataract surgery relative to the United States.

RESULTS

Cost-utility values for cataract surgery (first eye) varied from $245 to $22,000/QALY in Western countries and from $9 to $1600 in developing countries. In developed countries, the cost-effectiveness of cataract surgery estimated by Choosing Interventions That Are Cost Effective ranged from, in international dollars (I$), I$730 to I$2400/disability-adjusted life years (DALY) averted, and I$90 to I$370/DALY averted in developing countries. The CSAI varied from 17% to 189% in developed countries and 29% to 133% in developing countries compared with the United States. The cost-utility of other comparable medical interventions was: epileptic surgery, $4000 to $20,000/QALY; hip arthroplasty, $2300 to $4800/QALY; knee arthroplasty, $6500 to $12,700/QALY; carpal tunnel surgery, $140 to $280/QALY; and defibrillator implantation, $700 to $23,000/QALY.

CONCLUSIONS

The cost-utility of cataract surgery varies substantially, depending how the benefit is assessed and on the duration of the assumed benefit. Cataract surgery is comparable in terms of cost-effectiveness to hip arthroplasty, is generally more cost-effective than either knee arthroplasty or defibrillator implantation, and is cost-effective when considered in absolute terms. The operation is considerably cheaper in Europe and Canada compared with the United States and is affordable in many developing countries, particularly India.

Usefulness of microvolt T-wave alternans on predicting outcome in patients with ischemic cardiomyopathy with and without defibrillators

Microvolt T-wave alternans (MTWA) was proposed as an effective tool to identify high-risk patients with ischemic cardiomyopathy. However, previous studies suggested that the prognostic utility of MTWA may be limited to only patients with normal QRS duration. It therefore was assessed whether MTWA and QRS duration >120 ms independently predict mortality in patients with ischemic cardiomyopathy and whether the prognostic utility of MTWA differs by QRS duration. A total of 768 consecutive patients with ischemic cardiomyopathy (left ventricular ejection fraction < or =35%) and no history of ventricular arrhythmia were enrolled, of whom 514 (67%) screened MTWA non-negative (positive or indeterminate) and 223 (29%) had a QRS >120 ms on resting electrocardiogram. After multivariable adjustment, a non-negative MTWA test result was associated with a significantly higher risk for all-cause mortality in patients without an implantable cardioverter-defibrillator (ICD) (hazard ratio [HR] 2.27, 95% confidence interval [CI] 1.22 to 4.24, p = 0.01) and for all-cause mortality and appropriate ICD shocks in patients with an ICD (HR 2.42, 95% CI 1.07 to 5.41, p = 0.04). In contrast, a QRS >120 ms was not associated with all-cause mortality and ICD shocks in patients without (HR 0.96, 95% CI 0.52 to 1.75, p = 0.88) or with an ICD (HR 1.25, 95% CI 0.76 to 2.08, p = 0.40). No significant interaction was found between MTWA and QRS >120 ms (non-ICD p = 0.19, ICD p = 0.73). In conclusion, MTWA, but not QRS duration, predicted mortality outcomes in patients with ischemic cardiomyopathy. Moreover, the prognostic utility of MTWA did not appear to differ by QRS duration.

Optimising the dichotomy limit for left ventricular ejection fraction in selecting patients for defibrillator therapy after myocardial infarction

BACKGROUND

The selection of patients for prophylactic implantable cardioverter-defibrilator (ICD) treatment after myocardial infarction (MI) remains controversial.

AIM

To determine the optimum left ventricular ejection fraction (LVEF) dichotomy limit for ICD treatment in patients with a history of MI.

METHODS AND RESULTS

Data from the placebo arms of four randomised trials were pooled to create a cohort of 2828 patients (2206 men, mean (SD) age 65 (11) years) with reduced left ventricular function after MI. The median LVEF was 33% (range 6-40%). LVEF significantly predicted mortality. Each 10% reduction in LVEF <40% conferred a 42% increase in all-cause mortality, a 39% increase in arrhythmic cardiac mortality and a 49% increase in non-arrhythmic cardiac mortality over the 2-year period of follow-up (p<0.001 for all modes of mortality). As the LVEF progressively decreased from < or =40% to < or =10%, the data show a U-shaped relationship between the dichotomy limit for LVEF used and the number of patients who must be treated to prevent one arrhythmic death in 2 years. At an LVEF of 16-20%, more patients are likely to die from arrhythmic than non-arrhythmic cardiac deaths, whereas in those with LVEF < or =10% all deaths were non-arrhythmic. However, the total number of deaths substantially decreased with lower LVEF.

CONCLUSION

A trade-off exists between the sensitivity and positive predictive accuracy across a range of LVEF, and no single dichotomy limit is completely satisfactory. In patients with LVEF < or =10% ICD treatment was not beneficial as all patients in this subgroup died from non-arrhythmic causes. The use of a single dichotomy limit for LVEF alone is not sufficient in selecting patients for ICD treatment in the primary prevention of cardiac arrest.

Predictive value of microvolt T-wave alternans in patients with left ventricular dysfunction

OBJECTIVES

The purpose of this study was to prospectively evaluate the utility of microvolt T-wave alternans (TWA) in predicting arrhythmia-free survival and total mortality in patients with left ventricular (LV) dysfunction.

BACKGROUND

Microvolt TWA has been proposed as a useful tool in identifying patients unlikely to benefit from prophylaxis with implantable cardioverter-defibrillator (ICD) prophylaxis.

METHODS

We evaluated 286 patients with an LV ejection fraction </=35% who underwent TWA and electrophysiologic testing (EPS) owing to nonsustained ventricular tachycardia and/or syncope. Positive and indeterminate TWA results were grouped as non-negative. The primary end point was arrhythmia-free survival; the secondary end point was all-cause mortality.

RESULTS

Patients were followed for a mean of 38 +/- 11 months. There was no significant difference between the TWA-negative (n = 90; 31%) and non-negative (n = 196; 69%) groups with respect to ICD implant rates (54% vs. 64%, respectively; p = 0.95) or etiology of cardiomyopathy (ischemic: 73% vs. 76%; p = 0.71). The Kaplan-Meier curves demonstrated improved arrhythmia-free survival in TWA-negative patients (81% vs. 66% at 2 years; p < 0.001), including in both ischemic (79% vs. 64% at 2 years; p = 0.004) and nonischemic (88% vs. 71% at 2 years; p = 0.015) subgroups. Total mortality was lower in the TWA-negative group (10% vs. 18% at 2 years; p = 0.04). The negative predictive value of TWA for (2-year) total mortality was 90%, and 83% for EPS.

CONCLUSION

Microvolt TWA predicts arrhythmia-free survival among patients with LV dysfunction. However, the event rate in the TWA-negative group suggests that TWA may not be capable of identifying a sufficiently low-risk subset in this population to obviate the need for ICD implantation.

Incremental benefit and cost-effectiveness of high-dose statin therapy in high-risk patients with coronary artery disease

BACKGROUND

Recent clinical trials found that high-dose statin therapy, compared with conventional-dose statin therapy, reduces the risk of cardiovascular events in patients with acute coronary syndromes (ACS) and stable coronary artery disease (CAD). However, the actual benefit and cost-effectiveness of high-dose statin therapy are unknown.

METHODS AND RESULTS

We designed a Markov model to compare daily high-dose with conventional-dose statin therapy for hypothetical 60-year-old cohorts with ACS and stable CAD over patient lifetime. Pooled estimates for major clinical end points (all-cause mortality, myocardial infarction, stroke, rehospitalization, and revascularization) from relevant clinical trials were incorporated. Incremental benefit was quantified as quality-adjusted life-years (QALYs). Threshold analyses determined at what price difference high-dose statins would yield incremental cost-effective ratios below $50,000, $100,000, and $150,000 per QALY gained. In ACS patients, a high-dose versus conventional-dose statin strategy resulted in a gain of 0.35 QALYs. In threshold analyses, a high-dose statin strategy consistently yielded incremental cost-effective ratios below $30,000 per QALY even under conservative model assumptions. In stable CAD patients, a high-dose statin strategy yielded a gain of only 0.10 QALYs and was sensitive to model assumptions about statin efficacy. The daily cost difference between a high- and conventional-dose statin would need to be <$1.70, $2.65, and $3.55 to yield incremental cost-effective ratios below $50,000, $100,000, and $150,000 per QALY.

CONCLUSIONS

High-dose statin therapy is potentially highly effective and cost-effective in patients with ACS. In patients with stable CAD, however, the cost-effectiveness of high-dose statin therapy is highly sensitive to model assumptions about statin efficacy and cost. Use of high-dose statins can be supported on health economic grounds in patients with ACS, but the case is less clear for patients with stable CAD.

Prognostic implication of redefining indeterminate microvolt T-wave alternans studies as abnormal or normal

BACKGROUND

Prior studies involving microvolt T-wave alternans (MTWA) have combined positive and indeterminate studies into a high-risk "nonnegative" category. However, studies examining the prognostic utility of specific reasons for an indeterminate study are limited. The objective of this study was to assess if patients have differences in survival prognosis based on the reasons for an indeterminate MTWA result.

METHODS

We enrolled 768 consecutive patients with ischemic cardiomyopathy (left ventricular ejection fraction < or = 35%) and no prior history of sustained ventricular arrhythmia. Microvolt T-wave alternans studies were classified as positive, negative, or indeterminate. Prespecified multivariable Cox regression analyses, stratified by implantable cardioverter/defibrillator status, were used to determine whether there was heterogeneity in survival prognosis among the individual reasons for an indeterminate study.

RESULTS

We identified 159 (21%) patients with an indeterminate MTWA test. Reasons for indeterminate studies included frequent ectopy (46%), inability to reach adequate heart rate (IHR) (32%), unsustained alternans (9%), and excessive noise (13%). After multivariable adjustment, indeterminate studies due to ectopy/IHR were associated with a significantly higher risk for all-cause (stratified hazard ratio [HR] 4.63, 95% CI 1.32-16.18, P = .02) and arrhythmic mortality (stratified HR 17.57, 95% CI 1.62-190.50, P = .02) but not for nonarrhythmic mortality (stratified HR 1.30, 95% CI 0.27-6.29, P = .75). The prognostic utility of MTWA testing was improved when indeterminate studies were reclassified as abnormal (positive + ectopy/IHR) or normal (negative + unsustained alternans), with only 3% of all studies thereafter remaining inconclusive (noise).

CONCLUSION

Patients with indeterminate MTWA studies exhibit heterogeneity in survival prognosis. Reclassifying indeterminate studies as abnormal or normal improves the predictive power of MTWA.

Effect of bundle branch block on microvolt T-wave alternans and electrophysiologic testing in patients with ischemic cardiomyopathy

BACKGROUND

T-wave alternans (TWA) and electrophysiology study (EPS) are used for risk stratification for sudden death.

OBJECTIVE

The purpose of the study was to determine the effect of bundle branch block or intraventricular conduction delay on TWA and EPS.

METHODS

386 patients with coronary artery disease, nonsustained ventricular tachycardia, and left ventricular ejection fraction < or =40% underwent TWA and EPS, and were followed for 40 +/- 19 months.

RESULTS

Patients with wide QRS were more likely than narrow QRS patients to have nonnegative TWA (77% vs 63%, P <.01) or positive EPS (60% vs 48%, P = .03). Nonnegative TWA predicted the combined endpoint of ventricular tachyarrhythmia or death in narrow QRS (HR = 1.64, P = .04) but not wide QRS patients (HR = 1.04, P = .91). Similarly, positive EPS predicted the combined endpoint in narrow QRS (HR = 2.28, P <.001) but not wide QRS patients (HR = 0.94, P = .84). In multivariate analysis, QRS width and TWA, as well as QRS width and EPS, were independent predictors of events. There was no TWA- or EPS-based difference in arrhythmia-free survival within any specific wide QRS morphology.

CONCLUSION

TWA and EPS are more often abnormal in patients with a wide QRS than in those with a narrow QRS. In patients with narrow QRS, both TWA and EPS stratify patients according to their risk of ventricular tachyarrhythmia or death. However, among patients with a wide QRS, regardless of specific QRS morphology, the risk is high and comparable regardless of TWA or EPS results. Therefore, the only truly low-risk group consists of those patients with negative test results and a narrow QRS.

Predicting Arrhythmia-Free Survival Using Spectral and Modified-Moving Average Analyses of T-Wave Alternans

BACKGROUND

T-wave alternans (TWA) is a promising electrocardiogram (ECG) predictor of sudden cardiac arrest, yet needs specialized recordings for conventional spectral analysis. Modified moving average (MMA) analysis is a new approach that can measure TWA from routine ECGs, thus widening its applicability. However, MMA-TWA has not been calibrated against spectral TWA nor outcome in high risk patients. We hypothesized that spectral and MMA-TWA would both predict arrhythmia-free survival on long-term prospective follow-up.

METHODS AND RESULTS

In 41 patients with left ventricular systolic dysfunction (ejection fraction 31 +/- 13%), we studied TWA simultaneously using spectral and MMA during pacing (< 110 beats/min). MMA amplified TWA over spectral analyses (13.0 +/- 8.28 microV vs 1.96 +/- 5.15 microV, P < 0.001). On 542 +/- 311 days' follow-up, from clinic visits, telephonic interviews, and device interrogations, there were 11 deaths or sustained ventricular arrhythmias ('events'). Positive spectral TWA (>or=1.9 microV) identified patients with from those without events (P = 0.02). Receiver-operating characteristics for MMA-TWA showed that the cutpoint >or= 10.75 microV was optimal for the combined endpoint. Kaplan-Meier analysis using this MMA-TWA cutpoint trended to predict events (P = 0.06), while MMA combined with spectral TWA identified events (P = 0.01).

CONCLUSIONS

MMA amplifies TWA compared to traditional spectral analyses, but both likely reflect similar pathophysiology. Validation in larger populations will enable MMA-TWA to be widely applied to stratify risk for sudden cardiac arrest.

Clinical significance of microvolt T-wave alternans

Several studies have recently proven that primary preventive therapy of sudden arrhythmogenic death is possible in selected patients with congestive heart failure, particularly in the setting of ischemic cardiomyopathy [1, 2]. However, a number needed to treat between 11 and 17 to save one life over three years in these studies indicates that a more accurate identification of high risk patients is desirable in order to avoid unnecessary implants of cardioverter/defibrillators (ICD). Since currently available risk stratification methods have limited predictive accuracy, development of new techniques is important in order to non-invasively assess arrhythmogenic risk in patients prone to sudden death. Microvolt level T-wave alternans (mTWA) has recently been proposed to assess abnormalities in ventricular repolarization favoring the occurrence of reentrant arrhythmias [3, 4]. In 1994, a first clinical study by Rosenbaum and coworkers [5] convincingly demonstrated that mTWA is closely related to arrhythmia induction in the electrophysiology (EP) laboratory as well as to the occurrence of spontaneous ventricular tachyarrhythmias during follow-up [5]. More recently, a number of clinical studies has examined its clinical applicability [4-7]. The present review summarizes currently available clinical data on TWA with a particular focus on risk stratifying patients with congestive heart failure and myocardial infarction.

Sudden cardiac death: epidemiologic and financial worldwide perspective

The term sudden cardiac death (SCD) implies the sudden and unexpected loss of an active, productive member of the community. SCD is typically attributed to lethal ventricular arrhythmias; however, these arrhythmias are impossible to diagnose after the fact. Epidemiologic analyses, therefore, rely on inference of the cause of death. Estimates of the incidence of are SCD variable but it may be as high as 1 per 1,000 per year. The cost of SCD to society is incalculable. Current strategies for preventing SCD rely on risk assessment for cardiology patients and implantation of defibrillators (ICD) in high risk patients. Unfortunately, the absolute number of SCDs that occur in the general (relatively low-risk) population is large compared to the number of SCDs in the high risk population. Therefore, prevention of SCD in high risk populations is unlikely to prevent the majority of SCDs. Cost-effectiveness of ICD implantation for prevention of SCD has been studied; ICDs appear to meet U.S. and European criteria for cost-effectiveness if their benefit extends to at least 7-8 years. However, therapies considered cost-effective may nonetheless be too costly for most worldwide societies. Currently, investigators are focusing on refining risk stratification, partly in hopes of identifying patients for whom ICD implantation will not be useful.

Microvolt T-Wave Alternans Identifies Patients With Ischemic Cardiomyopathy Who Benefit From Implantable Cardioverter-Defibrillator Therapy

OBJECTIVES

This study sought to assess whether implantable cardioverter-defibrillators (ICDs) have different mortality benefits among patients with ischemic cardiomyopathy who screen negative and non-negative (positive and indeterminate) for microvolt T-wave alternans (MTWA).

BACKGROUND

Microvolt T-wave alternans has been proposed as an effective tool for risk stratification. However, no studies have examined whether ICD benefits differ by MTWA group.

METHODS

We developed a prospective cohort of 768 patients with ischemic cardiomyopathy (left ventricular ejection fraction < or =35%) and no prior sustained ventricular arrhythmia, of which 392 (51%) received ICDs. The mean follow-up time was 27 +/- 12 months. Propensity scores for ICD implantation based on the variables most likely to influence defibrillator implantation were developed for each MTWA cohort. Multivariable Cox analyses that controlled for propensity score, demographics, and clinical variables evaluated the degree to which ICDs decreased mortality risk for each MTWA group.

RESULTS

We identified 514 (67%) patients with a non-negative MTWA test result. After multivariable adjustment, ICDs were associated with lower all-cause mortality in MTWA-non-negative patients (hazard ratio [HR] 0.45, 95% confidence interval [CI] 0.27 to 0.76, p = 0.003) but not in MTWA-negative patients (HR 0.85, 95% CI 0.33 to 2.20, p = 0.73) (for interaction, p = 0.04), with the mortality benefit in MTWA-non-negative patients largely mediated through arrhythmic mortality reduction (HR 0.30, 95% CI 0.13 to 0.68, p = 0.004). The number needed to treat with an ICD for 2 years to save 1 life was 9 among MTWA-non-negative patients and 76 among MTWA-negative patients.

CONCLUSIONS

In patients with ischemic cardiomyopathy and no prior history of ventricular arrhythmia, mortality reduction with ICD implantation differs by MTWA status, with implications for risk stratification and health policy.

Utility of microvolt T-wave alternans to predict sudden cardiac death in patients with cardiomyopathy

PURPOSE OF REVIEW

Sudden cardiac death remains a major cause of mortality among patients with cardiomyopathy and implantable cardioverter-defibrillator therapy has been shown to improve survival in these patients. Effective use of prophylactic implantable cardioverter-defibrillator therapy requires accurate risk stratification beyond assessment of ejection fraction, however. Repolarization alternans is a harbinger of ventricular arrhythmias and its measurement from body-surface recordings, also known as microvolt T-wave alternans, is emerging as an effective prognostic tool in these patients based on recent clinical trials.

RECENT FINDINGS

We review the pathogenesis and determinants of repolarization alternans. The current techniques for measuring T-wave alternans from the body surface are compared, including the spectral and modified moving average methods. Recent clinical trials evaluating the prognostic utility of T-wave alternans in patients with ischemic and nonischemic cardiomyopathy and no prior arrhythmic events are summarized. The findings of these studies are discussed in the context of implantable cardioverter-defibrillator prophylaxis. Body-surface T-wave alternans is an evolving technique and its limitations are presented along with approaches to improve its predictive accuracy.

SUMMARY

Risk stratification with T-wave alternans has the potential to guide prophylactic implantable cardioverter-defibrillator therapy in a growing population of patients with cardiomyopathy.