Primary Implantable Cardioverter-defibrillator Research Articles

Impact of Baseline Heart Failure Burden on Post-Implantable Cardioverter-Defibrillator Mortality Among Medicare Beneficiaries

This study sought to assess the impact of baseline heart failure (HF) burden on survival with primary implantable cardioverter-defibrillator (ICD) among Medicare recipients. Survival after primary ICD implantation may differ between trial and Medicare populations. Linking data from the CMS (Centers for Medicare and Medicaid Services) ICD registry and the Medicare files (2005 to 2009), we identified primary ICD recipients age ≥66 years with ejection fraction ≤35%. Number of previous HF hospitalizations (prev-HF-hosp) and length of hospitalization prior to implantation were used to define HF burden. Crude all-cause mortality was estimated. Adjusted hazard ratios (HR) were derived from Cox models. Of 66,974 ICD recipients (73% men, 88% white, mean age 75 years), 11,876 died (average follow-up = 1.4 years), with 3-year mortality of 31%. Among patients with no prev-HF-hosp, 3-year mortality was 27% compared with 63% in those with ≥3 prev-HF-hosp (adjusted HR: 1.8). Among patients with same-day implantation, 3-year mortality was 25% compared with 53% in those with >1-week hospitalization days prior to implantation (adjusted HR: 1.9). Mortality at 3-year follow-up among the 31,685 ICD recipients with no prev-HF-hosp and same-day implantation (low HF burden) was similar to that in trials (22%). Nearly one-third of Medicare ICD recipients died within 3 years, reflecting a population with more advanced age and disease than seen in trial populations for primary prevention ICD. Nearly one-half of Medicare recipients had a low HF burden and had a survival similar to trial ICD recipients. Future research is warranted to understand the effectiveness of primary ICD implantation among Medicare beneficiaries with heavy HF burdens.

The implantable defibrillator and return to operation of vehicles study

We sought to characterise driving habits of contemporary implantable cardioverter defibrillator (ICD) patients. We performed a multicentre prospective observational study of consecutive ICD recipients. Non-commercial drivers with a valid licence were eligible. Patient and ICD data were recorded. All patients completed an anonymous questionnaire regarding their driving habits. Among 275 patients, 25 (9.1%) stopped driving permanently after ICD implantation. During a mean follow-up of 26.5 ± 4.5 months, 25.3% of patients received an ICD shock (52.5% appropriate). The median time to first shock was 7.0 (2.5, 17.5) months and was not significantly different between primary and secondary ICD patients. However, shocks (36.5 vs. 21.3%, P = 0.027) and recurrent shock episodes (17.5 vs. 6.2%, P = 0.011) were more common in secondary ICD patients. Physician-recommended driving restrictions were not recalled by 37.9% and not followed by 23.0% of patients. Overall, the mean duration of driving abstinence was 2.2 ± 2.9 and 3.6 ± 5.3 months for primary and secondary patients, respectively. Notably, 36.5% of secondary patients drove within 1 month. Eight patients (3.3%) received a shock while driving, five of which resulted in road traffic accidents. The annual risk of a shock while driving was 1.5%. Patient driving behaviour following ICD implantation is variable, with over one-third not remembering and almost one-quarter not adhering to physician-directed driving restrictions. Over one-third of secondary ICD patients drive within 1 month despite physician recommendations. Further studies are required to establish the optimal duration of driving restriction in ICD recipients.

Applicability of a Risk Score for Prediction of the Long-Term (8-Year) Benefit of the Implantable Cardioverter-Defibrillator

The present study was designed to explore the 8-year survival benefit of a nonresynchronization implantable cardioverter-defibrillator (ICD) according to a simple risk stratification score. There is limited information regarding factors that predict the benefit of primary prevention with an ICD during long-term follow-up. This study used a previously developed risk score including 5 clinical factors (New York Heart Association functional class >II, age >70 years, blood urea nitrogen >26 mg/dl, QRS duration >0.12 s, and atrial fibrillation) to evaluate 8-year ICD survival benefit within risk score categories among 1,191 MADIT-II (Multicenter Automatic Defibrillator Implantation Trial II) patients. Patients with low (0 risk factors, n = 345) and intermediate risk (1 to 2 risk factors, n = 646) demonstrated a significantly higher probability of survival at 8-year follow-up when treated by ICD as compared with non-ICD therapy (75% vs. 58%, p = 0.004; and 47% vs. 31%, p < 0.001, respectively). By contrast, among high-risk patients (3 or more risk factors, n = 200), there was no significant difference in 8-year survival between the ICD and non-ICD subgroups (19% vs. 17%, p = 0.50). Consistently, multivariate analysis showed that ICD therapy was associated with a significant long-term survival benefit among low- and intermediate-risk patients (hazard ratio [HR]: 0.52, p < 0.001, and HR: 0.66, p < 0.001, respectively), whereas treatment with an ICD was not associated with a significant benefit among high-risk patients (HR: 0.84, p = 0.25). These findings suggest that a simple risk score can identify patients who derive significant long-term benefit from primary ICD therapy. High-risk patients with multiple comorbidities composed 17% of the MADIT-II population and did not derive long-term benefit from nonresynchronization device therapy.

The mode of death in implantable cardioverter-defibrillator and cardiac resynchronization therapy with defibrillator patients: Results from routine clinical practice

Although data on the mode of death of implantable cardioverter-defibrillator (ICD) and cardiac resynchronization therapy with defibrillator (CRT-D) patients have been examined in randomized clinical trials, in routine clinical practice data are scarce. To provide reasonable expectations and prognosis for patients and physicians, this study assessed the mode of death in routine clinical practice. To assess the mode of death in ICD/CRT-D recipients in routine clinical practice. All patients who underwent an ICD or CRT-D implantation at the Leiden University Medical Center, the Netherlands, between 1996 and 2010 were included. Patients were divided into primary prevention ICD, secondary prevention ICD, and CRT-D patients. For patients who died during follow-up, the mode of death was retrieved from hospital and general practitioner records and categorized according to a predetermined classification: heart failure death, other cardiac death, sudden death, noncardiac death, and unknown death. A total of 2859 patients were included in the analysis. During a median follow-up of 3.4 years (interquartile range 1.7-5.7 years), 107 (14%) primary prevention ICD, 253 (28%) secondary prevention ICD, and 302 (25%) CRT-D recipients died. The 8-year cumulative incidence of all-cause mortality was 39.9% (95% confidence interval 37.0%-42.9%). Heart failure death and noncardiac death were the most common modes of death for all groups. Sudden death accounted for approximately 7%-8% of all deaths. For all patients, heart failure and noncardiac death are the most common modes of death. The proportion of patients who died suddenly was low and comparable for primary and secondary ICD and CRT-D patients.

Guidelines for implantation of primary prevention defibrillators: Who is listening?

i r a p i m m m a b r w m S t c c Pivotal trials over the past decade have established that implantable cardioverter-defibrillators (ICDs) prevent sudden death and improve overall survival in high-risk groups, identified broadly on the basis of low left ventricular ejection fraction (EF) and heart failure. In 2005, the Center or Medicare & Medicaid Services extended the US national overage determination for ICD implantation to include rimary prevention indications based on the results of these ivotal trials. The Center for Medicare & Medicaid Services estricted coverage for patients with recent myocardial inarctions and newly diagnosed heart failure, since these ere exclusions from the pivotal trials and other studies ailed to demonstrate benefit in these situations. Guidelines rom ACC/AHA/HRS identify specific class I indications or ICD implantation in patients with left ventricular dysunction (ejection fraction 35% and class II/III heart failre; ejection fraction 30% and class I heart failure in schemic cardiomyopathy). Why then are primary prevenion ICDs implanted in only a minority of eligible recipints? Barriers to ICD implantation occur at several levels. The treating physician may not understand the indications for ICD implantation or may believe that implantation is not warranted. The patient may decline to have the implantation, particularly if he or she cannot expect symptomatic improvement from a purely prophylactic device. In some localities, access to an implanting physician may be difficult or cumbersome. Highly publicized generator and lead recalls have probably eroded the enthusiasm of some physicians and patients for prophylactic ICDs. It also has been shown that wide variations exist in ICD utilization, depending on geographical region, practice setting, availability of electrophysiologists, race, and insurance status. Just as puzzling as the failures to refer high-risk patients are the implantations that clearly fall outside of current guidelines. This issue was highlighted by an analysis of the US ICD Registry that found that 23% of the ICD implantations were “non–evidence-based.” Arguably, many of

Predictors of sustained ventricular arrhythmia episodes in patients with primary ICD indication

Implantable cardioverter-defibrillators (ICD) reduce mortality in patients with severely impaired left ventricular function. In randomized studies, female patients are underrepresented and data on ICD therapy is limited. Atrial fibrillation (AF) is a determinant of poor prognosis but has not been consistently evaluated. We evaluated the risk factors for the occurrence of ventricular arrhythmia episodes in patients with primary ICD prophylaxis. Consecutive patients after ICD implantation for primary prophylaxis were followed. During follow-up, detected sustained episodes of ventricular arrhythmia were documented. Multivariate analysis controlled for propensity score was used to evaluate the correlation between gender, history of AF, and the occurrence of ventricular arrhythmia episodes. A total of 400 patients (19.8% female; n = 79) were included. During follow-up, 64 patients (16%) had appropriate ICD therapy episodes. Men (18%) had significantly more often episodes than women (8%; p = 0.025). Patients with a history of AF (102, 25.5%) had significantly more often episodes (30%) compared to patients without a history of AF (11%; p < 0.001). In a multivariate model, only gender (p = 0.02) and history of AF (p < 0.001) were significantly associated predictors of the occurrence of appropriate ICD therapies during follow-up. Based on the propensity score model, the adjusted hazard ratio for male gender was 2.7 (p = 0.02) and 2.6 (p = 0.0004) for history of AF. Male gender and history of AF are independent predictors for the occurrence of sustained ventricular arrhythmia in primary ICD prophylaxis. Further studies need to evaluate whether history of AF in female patients might be an indicator for higher risk of sudden cardiac arrhythmic death.

Predictors of All‐Cause 1‐Year Mortality in Implantable Cardioverter Defibrillator Patients with Chronic Chagas’ Cardiomyopathy

Implantable cardioverter defibrillators (ICDs) have been used in the treatment of either sustained ventricular tachycardia or ventricular fibrillation in patients with Chagas' cardiomyopathy. This study aimed at determining mortality rate and risk factors of all-cause 1-year mortality in primary and secondary ICD patients with Chagas' cardiomyopathy. One hundred and forty-eight Chagas' patients with ICDs were included from the Medtronic ICD Registry Latin America. All patients were followed for 1 year. At implant, mean age was 60.1 ± 9.4 years and 72.9% were male. Mean left ventricular ejection fraction (LVEF) was 40.1 ± 11%. Mean follow-up was 12 ± 7 months. During the follow-up, 15 patients died (10.2%). Patients who died were older (64 ±10.8 years vs 59 ± 9.1; P = 0.04), had more atrial fibrillation (13.3% vs 3.8%; P = 0.02), had lower LVEF (33.4%± 9.8 vs 40.9%± 11.3; P = 0.01), and worse functional class (III/IV 40% vs 21.8%; P = 0.03). The multivariate analysis showed that two independent predictors of all-cause 1-year mortality remained statistically significant: age more than 65 (hazard ratio [HR] = 2.85, 95% confidence interval [CI] 1.77-3.92; P = 0.03) and LVEF less than 30% (HR = 2.68, 95% CI 1.57-3.79; P = 0.04). This analysis showed that patients older than 65 years of age and with LVEF less than 30% were independent predictors of all-cause 1-year mortality in patients with chronic Chagas' cardiomyopathy.

Genetic Polymorphisms as Risk Stratification Tool in Primary Preventive ICD Therapy

More and more implantable cardioverter-defibrillators (ICDs) are implanted as primary prevention of sudden cardiac death (SCD). However, major problem in practice is to identify high-risk patients for SCD. Different methods for noninvasive risk stratification do not have a sufficient positive or negative predictive value. Since current approaches lead to implantation of ICDs in a large number of patients who will never suffer an arrhythmic event and simultaneously patients still die of SCD who currently did not seem eligible for primary preventive ICD implantation, there is a need for additional tools for risk stratification. Epidemiological studies point to a hereditary risk of SCD. Different susceptibility of each person concerning arrhythmogenic events might be explained by genetic polymorphisms. By obtaining an individual “pattern” of polymorphisms of genes encoding for proteins which are important in arrhythmogenesis in one patient, risk stratification in primary prevention of SCD might by improved.

Ventricular gradient and cardiac risk

This editorial refers to ‘QRS-T morphology measured from exercise electrocardiogram as a predictor of cardiac mortality’ by T. Kentta et al. , on page 701. The benefits of the prophylactic clinical use of implantable cardioverter-defibrillators (ICD) have been documented beyond any reasonable doubt by a multitude of prospective clinical trials.1–3 This does not mean that the present ICDs are without limitations and that further technical advances are not needed. Among other challenges, inappropriate shocks, frequent in some patients, not only limit the broader use of the devices but also pose a risk on their own. Also, attempts at initiating ICD prophylaxis shortly after acute myocardial infarction have so far been unsuccessful.4,5 Whether this relates to the implantation procedures, including test shocks, or whether the recently infarcted myocardium is particularly vulnerable to appropriate shocks and/or to other impacts of ICD implants is unknown. Still, the restriction of ICD implantation in patients with ischaemic heart disease to the chronic post-infarction stages is regrettable. High rates of the sudden cardiac deaths, potentially avoidable by ICD interventions, appear shortly after the infarction.6 These are examples of difficulties in ICD prophylaxis that need to be solved by a combination of further technological and clinical advances. Nevertheless, these challenges are not the major problem of ICD prophylaxis. The major unmet clinical need concerns the selection of candidates for primary ICD prevention. It is well known that the reduced left ventricular ejection fraction (LVEF) is not only the present goal standard of risk stratification for these purposes but it is also the only selection criterion that has gained the acceptance by both the clinical community and healthcare providers. Additional selection criteria, such as the prolonged QRS duration on standard resting electrocardiogram (ECG), that have also been occasionally imposed, are mostly seen …

An Overview of Current Strategies of Risk Assessment for Sudden Cardiac Death

Sudden cardiac death (SCD) remains one of the major challenges of contemporary cardiology. Major clinical trials have demonstrated that primary prophylaxis of implantable cardioverter-defibrillators (ICD) is effective in saving lives when applied to patients with a reduced cardiac function. However, absolute mortality reduction with ICD therapy was not so high. Thus, primary ICD prophylaxis would subject a large group of patients to extend life in only a small population (i.e., costly strategy). Although left ventricular ejection fraction (LVEF) is a gold standard in risk stratification for SCD, some of electrocardiographic (ECG) techniques or measurements are also utilized in identifying high-risk groups. Various ECG indices that reflect repolarization, depolarization, or autonomic abnormalities have been used as risk stratification markers. Clinical evidence supports the usefulness of T-wave alternans (TWA), heart rate turbulence (HRT), heart rate variability (HRV), late potentials (LP) by signal-averaged electrocardiography, and so on. However, positive predictive values of these markers are low in identifying patients at risk for SCD. At present, combined assessment of two or three noninvasive markers has been performed in clinical practice to increase predictive accuracy. In this session, we will overview current risk stratification techniques or measurements including standard, alternative, and new ECG markers for preventing SCD.

Long-term implications of cumulative right ventricular pacing among patients with an implantable cardioverter-defibrillator

Limited data regarding the effect of right ventricular pacing (RVP) on long-term survival following implantable cardioverter-defibrillator (ICD) implantation are available. The purpose of this study was to evaluate the effect of RVP on the long-term survival benefit of primary ICD therapy. Mortality data were obtained for all patients enrolled in the Multicenter Automatic Defibrillator Trial-II (MADIT-II) during an extended follow-up period of 8 years. The cumulative percent RVP during the trial was categorized as low (≤ 50% [n = 369]) and high (>50% [n = 198]). The benefit of ICD versus non-ICD therapy (n = 490) was evaluated in the two pacing categories during the early (0-3 years) and late (4-8 years) phases of the extended follow-up period. During the early phase of the extended follow-up period, ICD therapy was associated with similar benefits in the low-RVP and high-RVP subgroups (hazard ratio [HR] = 0.35 and 0.38, respectively, P <.001 for both). In contrast, during the late phase, the long-term survival benefit of the ICD was maintained among patients with low RVP (HR = 0.60, P <.001) and attenuated among those with the high RVP (HR = 0.89, P = .45). An increased risk for late mortality associated with high versus low RVP was evident only among patients without left bundle branch [LBBB] at enrollment (HR = 1.63, P = .002). Among ICD recipients, high RVP is associated with a significant increase in the risk of long-term mortality and with attenuated device efficacy. The deleterious effects of RVP are pronounced mainly in non-LBBB patients, suggesting a possible role for combined cardiac resynchronization-defibrillator therapy in this population.

Long-Term Benefit of Primary Prevention With an Implantable Cardioverter-Defibrillator

Background— The Multicenter Automatic Defibrillator Implantation Trial II (MADIT-II) showed a significant 31 reduction in the risk of death with primary implantable cardioverter-defibrillator (ICD) therapy during a median follow-up of 1.5 years. However, currently there are no data on the long-term efficacy of primary defibrillator therapy. Methods and Results— MADIT-II enrolled 1232 patients with ischemic left ventricular dysfunction who were randomized to ICD and non-ICD medical therapy and were followed up through November 2001. For the present long-term study, we acquired posttrial mortality data through March 2009 for all study participants (median follow-up, 7.6 years). Multivariate Cox proportional hazards regression modeling was performed to calculate the hazard ratio for ICD versus non-ICD therapy during long-term follow-up. At 8 years of follow-up, the cumulative probability of all-cause mortality was 49 among patients treated with an ICD compared with 62 among non-ICD patients ( P &lt;0.001). Multivariate analysis demonstrated that ICD therapy was associated with a significant long-term survival benefit (hazard ratio for 0- through 8-year mortality=0.66 [95 confidence interval, 0.56 to 0.78]; P &lt;0.001). Treatment with an ICD was shown to be associated with a significant reduction in the risk of death during the early phase of the extended follow-up period (0 through 4 years: hazard ratio=0.61 [95 confidence interval, 0.50 to 0.76]; P &lt;0.001) and with continued life-saving benefit during the late phase of follow-up (5 through 8 years: hazard ratio=0.74 [95 confidence interval, 0.57 to 0.96]; P =0.02). Conclusions— Our findings demonstrate a sustained 8-year survival benefit with primary ICD therapy in the MADIT-II population.

Clinical Summaries

Clinical Summaries

Risk Stratification in Post-myocardial Infarction Patients

Despite the implementation of modern therapy for acute myocardial infarction (AMI), the substrate for fatal ventricular tachycardia/fibrillation develops frequently. Primary prevention therapy by implantable cardioverter–defibrillator (ICD) to reduce the risk of sudden cardiac death is recommended in post-MI patients with significant left ventricular (LV) dysfunction. While the benefit of ICD therapy in chronic post-MI patients has been firmly established, the implantation of ICDs in the early post-MI period is not warranted. LV dysfunction has been a major determinant for entry into the primary preventative ICD trials. Currently, numerous risk stratifiers are under investigation in order to improve the efficacy of ICD therapy. More specific selection of patients at risk of preventable cardiac death, based on more than simply ejection fraction, is crucial for the future development of cost-effective prophylactic treatments aimed at closing the gap between scientific evidence and the limited resources of healthcare systems.

Experiences of Driving and Driving Restrictions in Recipients With an Implantable Cardioverter Defibrillator-The Patient Perspective

The implantable cardioverter defibrillator (ICD) is a lifesaving device for treating patients who have experienced (secondary prevention), or are likely to experience (primary prevention), sudden cardiac death due to ventricular arrhythmias. Individuals with an ICD are prohibited from driving for a restricted period after the implantation and after recurrence of a ventricular arrhythmia, which may affect the ICD recipient in daily life. The aim of this study was therefore to describe how ICD recipients perceive driving and the driving restriction. Fourteen men and 6 women, aged 43 to 82 years, with driving restrictions due to both secondary and primary ICD indications, were interviewed. Data were analyzed using phenomenography. The analysis resulted in the main category, the individual's unique relationship to driving, based on the categories: (1) achieving adherence on driving restrictions, (2) emotional influence of driving restriction, and (3) altered views on driving. The information was sometimes conceived as insufficient and unclear, and the willingness to accept the restriction differed. The ICD recipients perceived a loss of independence and changed self-image. Some patients had changed their driving behavior because of uncertainty of their driving abilities or fear of having arrhythmias/shocks while driving. They had different views on their future driving. Handling driving restrictions after ICD implantation and shocks is a complex and delicate issue in clinical practice and should be addressed in a dialogue with the ICD recipient. More individualized and structured information and support should be given according to the ICD recipients' experiences and needs.

Presumed arrhythmic death in consecutive survivors of acute myocardial infarction – implications for primary implantable cardioverter defibrillator implantation

To describe the occurrence of arrhythmic death among survivors of acute myocardial infarction (AMI) and the availability of a primary implantable cardioverter defibrillator (ICD). Consecutive patients who fulfilled the criteria for AMI admitted to the Sahlgrenska University Hospital during 21 months were prospectively followed for 2 years with a focus on echocardiography and mode of death. Among the 471 patients, for whom information on ejection fraction (EF) was available and who survived the first week, 10 patients died between days 7 and 30 - of whom one had an arrhythmic death. Among the 461 survivors on day 30, 34 patients (7.4%) had an EF of 30% or less. Among these, 24 were judged to be available for ICD implantation, of whom one died an arrhythmic death during follow-up. Among the remaining 10 patients who were excluded from ICD indication because of either high age and/or severe comorbidity, two patients died an arrhythmic death. Among the remaining 427 patients who had an EF greater than 30%, six died an arrhythmic death. Thus, 10 patients, with EF assessed, died an arrhythmic death between day 7 and 2 years after AMI, but only one would have received an ICD according to the Multicenter Automatic Defibrillator Implantation Trial II criteria and clinical judgement. Of the 471 consecutive survivors of AMI, 10 (2%) died an arrhythmic death, of whom only one would have received an ICD according to current guidelines and clinical judgement. Predictors of subsequent arrhythmic death after an AMI, useful on a per patient basis, remain an unmet need.

Low Referral Rate for Prophylactic Implantation of Cardioverter‐Defibrillators in a Tertiary Care Medical Center

Implantable cardioverter-defibrillators (ICDs) for primary prevention became standard of care after the publication of the second Multicenter Automatic Defibrillator Implantation Trial (MADIT-II) and Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT). To determine the percentage of patients in a Veterans Affairs medical center appropriately referred for primary prophylaxis ICD and to further categorize the reasons patients are not being referred. Echocardiograms obtained since the release of MADIT-II in 2002 were searched for a left ventricular ejection fraction (LVEF) < or = 35% and < or =30%. We randomly selected 120 patients per year from 2002 to 2006, for a total of 600 patients in each group. Data were reviewed to determine the number of ICD recipients and the reasons patients were not referred. In the LVEF < or = 35% group an ICD was implanted in 28% of 392 eligible patients. Nonreferral (58%) was the most common reason that eligible patients did not receive an ICD. Patients were not referred for ICD because of appropriate contraindications in 26% of cases. Overall mortality was 29% (15% with and 31% without ICD). In the LVEF < or =30% group an ICD was implanted in 33% of 388 eligible patients. Nonreferral (51%) was the most common reason that eligible patients did not receive an ICD. Patients were not referred for ICD because of appropriate contraindications in 24% of cases. Overall mortality was 28% (18% with and 32% without ICD). After the publication of MADIT-II and SCD-HeFT, only 42% of eligible patients with LVEF < or = 35% and 49% of patients with LVEF < or =30% were offered a potentially life-saving ICD between 2002 and 2006 in our medical center, sometimes with considerable delay.

Risk Stratification for Primary Implantation of a Cardioverter-Defibrillator in Patients With Ischemic Left Ventricular Dysfunction

The study was designed to develop a simple risk stratification score for primary therapy with an implantable cardioverter-defibrillator (ICD). Current guidelines recommend primary ICD therapy in patients with a low ejection fraction (EF). However, the benefit of the ICD in the low EF population may not be uniform. Best-subset proportional-hazards regression analysis was used to develop a simple clinical risk score for the end point of all-cause mortality in patients allocated to the conventional therapy arm of MADIT (Multicenter Automatic Defibrillator Implantation Trial)-II after excluding a pre-specified subgroup of very high-risk (VHR) patients (defined by blood urea nitrogen [BUN] >or=50 mg/dl and/or serum creatinine >or=2.5 mg/dl). The benefit of the ICD was then assessed within risk score categories and separately in VHR patients. The selected risk score model comprised 5 clinical factors (New York Heart Association functional class >II, age >70 years, BUN >26 mg/dl, QRS duration >0.12 s, and atrial fibrillation). Crude mortality rates in the conventional group were 8% and 28% in patients with 0 and >or=1 risk factors, respectively, and 43% in VHR patients. Defibrillator therapy was associated with a 49% reduction in the risk of death (p < 0.001) among patients with >or=1 risk factors (n = 786), whereas no ICD benefit was identified in patients with 0 risk factors (n = 345; hazard ratio 0.96; p = 0.91) and in VHR patients (n = 60; hazard ratio 1.00; p > 0.99). Our data suggest a U-shaped pattern for ICD efficacy in the low-EF population, with pronounced benefit in intermediate-risk patients and attenuated efficacy in lower- and higher-risk subsets.

Renal insufficiency predicts the time to first appropriate defibrillator shock

Indications for implantable cardioverter defibrillator (ICD) implantation are expanding, but many primary and secondary ICD trials have excluded patients with advanced renal insufficiency. We investigated the effect of renal function on the incidence and time to first appropriate ICD shock. We analyzed data from all new ICD implantations at a tertiary care center from July 2001 to December 2002. During a mean follow-up time of 445 +/- 285 days, 29 (13%) of 230 patients (age 63 +/- 14 years, 79% men, 77% white, 75% coronary artery disease, left ventricular ejection fraction 0.28 +/- 0.14) received 41 appropriate shocks. Patients were divided into tertiles according to their serum creatinine level. The 1-year incidence of appropriate ICD shock was 3.8%, 10.8%, and 22.7% in the first, second, and third tertiles, respectively (P = .003). Using the same cut off values of serum creatinine, the 1-year incidence of appropriate ICD therapy (shock and antitachycardia pacing) was 8.8%, 20.8%, and 26.3% (P = .02). After correcting for age, sex, race, left ventricular ejection fraction, indication for ICD implantation, and use of beta-blockers in a Cox regression model, serum creatinine was still an independent predictor of the time to first appropriate ICD shock (hazard ratio 6.0 for the third compared with the first tertile, P = .001). Renal insufficiency is a strong predictor of appropriate ICD shocks. Defibrillator therapy should therefore not be withheld based on the presence of this comorbidity. The mechanisms underlying the relationship between renal function and ventricular arrhythmias deserve further investigation.

Implantable Cardioverter‐Defibrillators for Primary Prevention: How Do the Data Pertain to the Aged?

The incidence of sudden cardiac death increases with age and the proportion of the US population in progressively more advanced age strata is dramatically increasing. While several randomized controlled trials support the use of implantable cardioverter-defibrillators (ICDs) to reduce sudden cardiac death, no randomized trials have been done to evaluate whether there is a mortality benefit of ICDs in an elderly population. In the current review, the authors examined six of the major primary prophylaxis ICD trials for evidence pertaining to the elderly. A majority of these trials suggest a mortality benefit in the elderly patients who have met the stringent inclusion and exclusion criteria to be eligible for enrollment. Subset analysis seems to support ICD implantation in a highly select elderly subgroup, but a prospective randomized trial may be warranted.