Long-term outcome with the automatic implantable cardioverter-defibrillator

The Selective Late Sodium Current Inhibitor Eleclazine, Unlike Amiodarone, Does Not Alter Defibrillation Threshold or Dominant Frequency of Ventricular Fibrillation

INTRODUCTION

We examined the effects of the selective late INa inhibitor eleclazine on the 50% probability of successful defibrillation (DFT50) before and after administration of amiodarone to determine its suitability for use in patients with implantable cardioverter defibrillators (ICDs).

METHODS AND RESULTS

In 20 anesthetized pigs, transvenous active-fixation cardiac defibrillation leads were fluoroscopically positioned into right ventricular apex through jugular vein. ICDs were implanted subcutaneously. Dominant frequency of ventricular fibrillation was analyzed by fast Fourier transform. The measurements were made before drug administration (control), and at 40 minutes after vehicle, eleclazine (2 mg/kg, i.v., bolus over 15 minutes), or subsequent/single amiodarone administration (10 mg/kg, i.v., bolus over 10 minutes). Eleclazine did not alter DFT50, dominant frequency, heart rate, or mean arterial pressure (MAP). Subsequent amiodarone increased DFT50 (P = 0.006), decreased dominant frequency (P = 0.022), and reduced heart rate (P = 0.031) with no change in MAP. Amiodarone alone increased DFT50 (P = 0.005; NS compared to following eleclazine) and decreased dominant frequency (P = 0.003; NS compared to following eleclazine).

CONCLUSION

Selective late INa inhibition with eleclazine does not alter DFT50 or dominant frequency of ventricular fibrillation when administered alone or in combination with amiodarone. Accordingly, eleclazine would not be anticipated to affect the margin of defibrillation safety in patients with ICDs.

Use of Antiarrhythmic Medications in Medicare Part D Patients With an Implantable Cardioverter-Defibrillator and Ventricular Tachycardia

Ventricular tachycardia (VT) is common in cardiomyopathy patients with an implantable cardioverter-defibrillator. This analysis evaluated antiarrhythmic medication use and change in use over time in patients with VT and structural heart disease. Query of Medicare claims identified patients with an implantable cardioverter-defibrillator and VT. Patients with atrial fibrillation or supraventricular tachycardia were excluded. Two cohorts were created of patients enrolled in Medicare Part D for the 12 months before 2007 and 2012. Patients were identified through a search for antiarrhythmic medication fills with a supply covering January 1 of the cohort year. Adjusted logistic regression modeling evaluated the association between patient characteristics and antiarrhythmic medication use. The 2007 (n = 2,334) and 2012 (n = 3,892) Medicare Part D cohorts had similar demographics: median age 76 years, 64%-67% male, and 87%-89% white. Of the 2007 cohort, 1,380 (59%) patients were on a beta blocker, and 484 (20.7%) were on an antiarrhythmic medication (70% amiodarone and 20% sotalol). Between 2007 and 2012, there was a statistically significant higher use of any antiarrhythmic medication (p = 0.014), beta blockers (p <0.0001), mexiletine (p = 0.005), and ranolazine (p <0.0001), while amiodarone use remained unchanged (p = 0.53). After multivariable adjustment, male gender and renal disease were associated with higher antiarrhythmic medication use. In conclusion, although antiarrhythmic medication and beta blocker use in patients with VT increased over time, <1 in 4 patients were on an antiarrhythmic medication and only 65% of the patients were on a beta blocker.

Management of pace-terminated ventricular arrhythmias

An implantable-cardioverter defibrillator (ICD) can terminate ventricular arrhythmias by delivering a shock or by antitachycardia pacing (ATP). The ATP works by capturing the excitable gap and disrupting re-entrant ventricular arrhythmias. Multiple studies have demonstrated that ATP is successful at terminating ventricular tachycardia (VT). Shocks from the ICD are associated with higher mortality. The data are conflicting about whether appropriate ATP is associated with higher mortality. In a patient with VT that is treated by ATP, the patient's guideline-based heart failure medications should be maximized. The use of VT ablation after appropriate and successful ATP requires additional studies.

Transvascular Implantation of an Implantable Cardioverter-Defibrillator in a Patient Who has Undergone One-and-a-Half Ventricle Repair

Implantable cardioverter-defibrillator (ICD) therapy is acknowledged as a valid treatment method for the effective prevention of sudden cardiac death, which is a major cause of mortality in adult congenital heart disease patients. But ICD implantation by the conventional transvascular approach is not always possible in patients who have undergone palliative surgery due to congenital and structural heart disease. Here, we report a case in which an ICD was transvascularly implanted in an arrhythmogenic right ventricular cardiomyopathy patient who had undergone a one-and-a-half ventricle repair.

Michel Mirowski and the beginning of a new era of fighting sudden arrhythmic death

Prior to the implantable cardioverter-defibrillator (ICD), life-threatening ventricular arrhythmias were treated using anti-arrhythmic drugs. The concept of an implantable defibrillator to prevent sudden arrhythmic death was first published by Michel Mirowski in 1970. Despite critical opinions by leading physicians, Michel Mirowski continued development of his vision. Hallmarks in the development of the ICD include the following: internal-external defibrillator used during surgery on humans in 1971/1972; fully implantable defibrillator tested in canines in 1975; defibrillator successfully implanted in a 57-year-old woman in 1980; second generation devices introduced in 1982; US Food and Drug Administration device approved in 1985. Today it is hard to imagine modern medicine without ICD therapy. This article provides the reader a history of the development of the ICD.

Prevalence, correlates, and temporal trends in antiarrhythmic drug use at discharge after implantable cardioverter defibrillator placement (from the National Cardiovascular Data Registry [NCDR])

Patients with implantable cardioverter defibrillators (ICDs) can require antiarrhythmic drugs to manage arrhythmias and prevent device shocks. We sought to determine the prevalence, clinical correlates, and institutional variation in the use of antiarrhythmic drugs over time after ICD implantation. From the ICD Registry (2006 to 2011), we analyzed the trends in the use of antiarrhythmic agents prescribed at hospital discharge for patients undergoing first-time ICD placement. The patient, provider, and facility level variables associated with antiarrhythmic use were determined using multivariate logistic regression models. A median odds ratio was calculated to assess the hospital-level variation in the use of antiarrhythmic drugs. Of the cohort (n = 500,995), 15% had received an antiarrhythmic drug at discharge. The use of class III agents increased modestly (13.9% to 14.9%, p <0.01). Amiodarone was the most commonly prescribed drug (82%) followed by sotalol (10%). Among the subgroups, the greatest increase in prescribing was for patients who had received a secondary prevention ICD (26% in 2006% and 30% in 2011, p <0.01) or with a history of ventricular tachycardia (23% to 27%, p <0.01). The median odds ratio for antiarrhythmic prescription was 1.45, indicating that 2 randomly selected hospitals would have had a 45% difference in the odds of treating identical patients with an antiarrhythmic drug. In conclusion, antiarrhythmic drug use, particularly class III antiarrhythmic drugs, is common among ICD recipients at hospital discharge and varies by hospital, suggesting an influence from local treatment patterns. The observed hospital variation suggests a role for augmentation of clinical guidelines regarding the use of antiarrhythmic drugs for patients undergoing implantation of an ICD.

Use and long-term outcomes of implantable cardioverter-defibrillators, 1990 to 2009

BACKGROUND

Automated implantable cardioverter-defibrillators (ICDs) have become standard therapy for patients at high risk for sudden cardiac death. Linked data allow examination of trends in use and long-term survival after ICD implantation in an adult population.

METHODS

Linked state-wide person-based data on hospital admissions and deaths from 1980 to 2009 were used to identify incident cases of ICD implantation. Population rates were calculated using census data. Kaplan-Meier techniques were used to describe cumulative survival. Cox regression models were used to determine the factors associated with the outcomes.

RESULTS

Between 1988 and 2009, 1593 devices were implanted in patients in Western Australia, rising from 2 in 1988 to 245 in 2009; standardized population rates rose from 0.8 in 100000 in 1995 to 14.9 in 100000 in 2009. Mean age rose from 52.6 (SD 11.6) to 64.1 (11.4) years. Ventricular tachycardia (23%), cardiomyopathy (18%), and heart failure (16%) were the most frequent principal diagnoses. Ischemic heart disease was present in 49% of patients. Five-year cumulative survival was 0.74 (SE 0.01), and at 10 years, 0.53 (SE 0.03); median survival was 11.3 years. Readmission within a year, older age, heart failure, device complications, and chronic ischemic heart disease were associated with poorer survival.

CONCLUSIONS

Implantable cardioverter-defibrillator use in adults at risk for sudden cardiac death has grown rapidly. Readmission within 12 months of discharge is associated with worse medium and long-term mortality. Survival for most patients younger than 65 years exceeds 10 years and 5 years for those aged ≥75 years.

Predictors of high defibrillation threshold in the modern era

INTRODUCTION

High defibrillation threshold (DFT) is a clinical problem in 1-8% of implantable cardioverter-defibrillator implants. Some clinicians and investigators question whether the benefits of routine DFT testing outweigh the risks. Identification of the predictors of elevated DFT may allow selective application of DFT testing. However, the clinical characteristics of patients with high DFT in the modern era have not been well-defined.

METHODS

All patients who underwent DFT testing in our institution during an 8-year period were reviewed for this retrospective study. High DFT was defined as less than a 10-J safety margin on initial testing. For each case, the two cases preceding and two cases following by the same implanter were selected as controls.

RESULTS

Of the 2,138 patients who underwent DFT testing, 48 (2.2%) met criteria for high DFT. Compared to 192 control patients, patients with high DFT were more likely to be younger (P = 0.004), have nonischemic cardiomyopathy (P = 0.036), have a longer QRS interval (P = 0.026), and have a left ventricular ejection fraction (LVEF) ≤ 0.25 (P = 0.013). On multivariate analysis, only younger age (P = 0.016) and LVEF ≤ 0.25 (P = 0.010) remained statistically significant predictors of elevated DFT.

CONCLUSIONS

High DFT was identified in 2.2% of ICD implants in our institution in recent years. Although younger age and depressed LVEF predicts this problem, elevated DFT occurred in patients of all ages and ejection fractions. Elimination of routine DFT testing appears to be premature given the prevalence and unpredictability of elevated DFT.

Outcome of implantable cardioverter defibrillator therapy for congenital heart disease

BACKGROUND

The use of implantable cardioverter defibrillator (ICD) therapy for congenital heart disease (CHD) has been increasing, but few studies have reported on the efficacy of ICD therapy in Japanese CHD patients.

METHOD

Twelve CHD patients (median age, 35 years) with first ICD implantation were examined. Median follow-up duration was 2.9 years. Demographic information, implant electrical parameters, appropriate and inappropriate discharge data and complications were recorded for all implants from 2003 to 2010.

RESULTS

Implant indication was primary prevention in two patients and secondary prevention in 10. Overall four patients received one or more discharges; three patients (25%) with secondary prevention received nine appropriate discharges. Inappropriate discharge attributed to sinus tachycardia occurred in two patients (16.7%). Only one patient experienced the late complication of skin erosion at the generator implantation site.

CONCLUSIONS

Patients with CHD experienced significant rates of appropriate discharges and lower complications. But given that the indications of ICD implantation were mostly for secondary prevention, the ratio of appropriate shocks might be lower than in previous studies. In the primary prevention patients, the benefit of ICD was not clear because no appropriate discharges were seen during follow up. Although ICD implantation for CHD is beneficial for preventing sudden cardiac death, careful decision making and a large, long-term prospective study is required for the determination of the efficacy of ICD therapy in Japanese patients with CHD.

Secondary prevention in heart failure

Although most recent investigations into sudden cardiac death prevention in heart failure patients have been focused on primary prevention, secondary indications for defibrillators and medical therapy remain vitally important in this complex patient group. Antiarrhythmic therapy is currently used primarily as adjuvant therapy to implantable defibrillators. Secondary prophylaxis defibrillator trials have shown clear benefit in preventing recurrent sudden cardiac death, despite concern over inappropriate shocks and the potential detrimental effects of appropriate shocks. Device programming for secondary prophylaxis can help ameliorate these issues. This article discusses these issues as well as the continued underuse of defibrillators in specific populations.

Predictors of appropriate therapy in patients with implantable cardioverter-defibrillator for primary prevention of sudden cardiac death

The purpose of this study was to evaluate predictors of appropriate therapy in patients with implantable cardioverter-defibrillators (ICD) for primary prevention of sudden cardiac death. A retrospective cohort of 321 patients with systolic heart failure undergoing ICD placement for primary prevention of sudden cardiac death was queried with a mean follow-up period of 2.6 years. Appropriate ICD therapy was defined as therapy delivered for termination of a ventricular tachyarrhythmia. Appropriate ICD therapy was delivered in 142 (44%) of the patients. In a multivariate model, body mass index ≥28.8 kg/m², chronic kidney disease, left ventricular ejection fraction ≤20% and metabolic syndrome were found to be independent predictors of appropriate ICD therapy. Appropriate ICD therapy was associated with higher cardiovascular mortality. These findings show the importance of identification of risk factors, especially metabolic syndrome, in patients following ICD implantation as aggressive treatment of these co-morbidities may decrease appropriate ICD therapy and cardiovascular mortality.

[Stored electrograms to differenciate between adequate and inadequate ICD therapy]

The introduction of implantable cardioverter defibrillators in 1980 by Mirowski et al, offered a new therapeutic device for the treatment of ventrikular tachyarrhythmias. In the beginning it was only possible to evaluate arrhythmic events by analysis of the therapy-counter in combination with clinical symptoms. Even rapid ventricular tachyarrhythmias may not produce significant symptoms prior to ICD shock in more than 50% of patients. On the other hand the ICD device will initiate inappropriate therapy due to sensing error and non sustained tachyarrhythmias in 20-40% of patients. Third generation ICD devices provide sophisticated diagnostic information by stored electrograms. Intracardiac electrograms are recorded by the bipolar tip electrode of the sensing lead, located in the right ventricel (near field) or by the electrodes used for energy delivery (far field). These ECG recordings provide valuable information to evaluate the type of arrhythmia, trigger mechanisms and therapeutic efficacy. The arrhythmia leading to device therapy is judged by cycle length and stability and morphology of the intracardiac signal. A correct arrhythmia classification using electrogram analysis is possible in 92-98% of arrhythmias. Evaluation is limited in 5-10% of patients with bundle branch block or aberand conduction. Inappropriate ICD therapy is caused by atrial fibrillation in more than 50% and by supraventricular tachycardia or sinus tachycardia in about 20%. Sensing of artefacts can be attributed to lead failure in about 17%. The distinction between appropriate and inappropriate therapeutic intervention by the ICD allows the prevention of unnecessary shock delivery and early diagnosis of lead failure. The development of dual chamber systems with enhanced storage capacity and improved algorithms for detection of arrhythmias may further decrease the incidence of inappropriate ICD therapies.

Automatic implantable cardioverter defibrillator pocket infection due to Providencia rettgeri: a case report

Coagulase-negative staphylococci and Staphylococcus aureus are the commonest pathogens involved in infections of pacemaker-defibrillator systems. Among causative Gram-negative bacteria, infections due to Klebsiella, Serratia, Pseudomonas, Acinetobacter and other species have been reported. We report herein a unique case of an automatic implantable cardioverter defibrillator infection due to Providencia rettgeri in a 65-year-old male who was admitted to our service with bacteremia and infection of the generator and subcutaneous array in a recently implanted device.

Predictors of implantable cardioverter defibrillator shocks during the first year

The purpose of this study was to predict implantable cardioverter defibrillator (ICD) shocks using demographic and clinical characteristics in the first year after implantation for secondary prevention of cardiac arrest. A prospective design was used to follow 168 first-time ICD recipients over 12 months. Demographic and clinical data were obtained from medical records at the time of ICD insertion. Implantable cardioverter defibrillator shock data were obtained from ICD interrogation reports at hospital discharge, 3, 6, and 12 months. Logistic regression was used to predict ever receiving an ICD shock using background characteristics. Patients received an ICD for secondary prevention of sudden cardiac arrest, they were 64.1 years old, 89% were white, 77% were male, with a mean (SD) ejection fraction of 33.7% (14.1%). The cumulative percentage of ever receiving an ICD shock was 33.3% over 1 year. Three variables predicted shocks in the first year: history of chronic obstructive pulmonary disease (COPD) (odds ratio [OR], 4.42; 95% confidence interval [CI], 1.2-16.4; P = .03), history of congestive heart failure (OR, 3.55; 95% CI, 1.4-9.3; P = .01), and documented ventricular tachycardia (VT) at the time of ICD implant (OR, 10.05; 95% Cl, 1.8-55.4; P = .01). High levels of anxiety approached significance (OR = 2.82; P = .09). The presence of COPD, congestive heart failure, or VT at ICD implant was a significant predictor of receiving an ICD shock in the first year after ICD implantation. Because ICD shocks are distressing, painful, and associated with greater mortality, healthcare providers should focus attention on prevention of shocks by controlling VT, careful management of HF symptoms, reduction of the use of short acting beta agonist medications in COPD, and perhaps recognizing and treating high levels of anxiety.

Potential proarrhythmic effects of implantable cardioverter-defibrillators

Implantable cardioverter-defibrillator (ICD) interventions have the potential to be proarrhythmogenic. New arrhythmias can occur in the setting of clinically appropriate therapies, as well as during a cardiac rhythm for which therapy is not intended. Cardioversion/defibrillation therapies, antitachycardia pacing, and antibradycardia pacing are potential triggers for the development of new arrhythmias. Newer ICDs allow better recognition and interpretation of the arrhythmias that are induced by delivered therapies. Two cases of ICD-induced proarrhythmias are described. Based on the course of these patients and review of previous reports, proarrhythmic effects of ICD interventions along with prevention and management strategies are discussed.

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.

Clinical usefulness of electrophysiologic study (EPS)-guided risk stratification for life-threatening arrhythmia in patients with heart failure

BACKGROUND

Ventricular tachyarrhythmia is one of the most important factors determining the prognosis of patients with heart failure and sudden death can be observed even during stable therapy controlling clinical heart failure. In this study, the usefulness of electrophysiologic study (EPS) for the prediction of a future arrhythmic event was evaluated in patients with heart failure.

METHODS AND RESULTS

The patient population consisted of 474 patients with a history of clinical heart failure but without an episode of spontaneous sustained ventricular tachycardia or fibrillation (VT/VF). A Holter ECG was performed in all patients, and 177 of the 474 patients underwent EPS because of a recording of nonsustained VT (NSVT, > 5 beats). When sustained VT/VF was inducible in EPS, the patient was assigned to implantation of a defibrillation device. The patients were divided into 3 groups, ie, 1) no NSVT (n = 297), 2) NSVT + no inducible VT/VF (n = 134), and 3) NSVT + inducible VT/VF (n = 43), and were followed-up for > 12 months. All patients were followed-up under standard therapy for heart failure. There were no significant differences in basic clinical characteristics and therapies among the 3 groups. During the follow-up period of 32 +/- 18 months, 56/474 patients suffered a VT/VF episode, ie, 21/297 in no NSVT, 14/134 in NSVT + no inducible VT/VF, and 21/43 in NSVT + inducible VT/VF patients (P = 0.032). All patients were rescued from sudden death among patients with an implanted defibrillator, but 11 patients without a defibrillator died.

CONCLUSION

In patients with heart failure, future arrhythmic events could be predicted by EPS and Holter ECG. EPS-guided risk stratification seems to be useful in managing patients with heart failure.

Clinical Predictors of Appropriate Implantable-Cardioverter Defibrillator Discharge

BACKGROUND

The implantable cardioverter-defibrillator (ICD) is the mainstay of treatment for ventricular tachyarrhythmias due to its impact on mortality. ICD discharges may be appropriate or inappropriate, and identification of patients at risk for ICD discharge is essential. We sought to determine the predictors of appropriate ICD discharge.

METHODS

We analyzed data from 591 ICD recipients (mean age 67.9 +/- 13.0 years; 474 men; mean follow-up 10.9 +/- 13.8 months). The association between ICD discharges and multiple clinical variables, including age, gender, hypertension, diabetes, coronary artery bypass graft (CABG) surgery, syncope, atrial fibrillation (AF), prior coronary intervention, left ventricular ejection fraction (LVEF), left ventricular end diastolic dimension, left ventricular end systolic dimension (LVESD), and ambient drug therapy was examined.

RESULTS

The rates of appropriate or inappropriate discharges, delivered to 155 patients, were 0.49 per follow-up year (F/Y). The median time-to-first appropriate discharge was 3.4 years. Among the discharges delivered, 97(63%) were appropriate and 58(37%) were inappropriate. Risk factors associated with a trend toward earlier appropriate discharges included age </= 65 years, and diuretic and digitalis use. By multiple variable analysis, no history of CABG and an enlarged LVESD were independent predictors of earlier appropriate ICD discharge.

CONCLUSIONS

Patients who did not have CABG revascularization were 2.8-fold more likely than those who underwent CABG, and patients with enlarged LVESD were 2.5-fold more likely than those with normal LVESD to receive appropriate ICD discharges. These patients deserve special vigilance and management in order to prevent the occurrence of ventricular tachyarrhythmias triggering ICD discharges.

Prävention des plötzlichen Herztodes

The problem of sudden cardiac death (SCD) is complex and many questions concerning the pathophysiologic mechanism are still unanswered. At present the only reliable way of recognizing high risk patients is by means of left ventricular dysfunction, measured as LV-EF<or=35%. The positive predictive accuracy for other non-invasive risk markers is too low. So far, antiarrhythmic drugs have failed to successfully prevent SCD. More than 25 years of clinical experience with the implantable defibrillator (ICD) with its continuous technical improvement has made the ICD the most effective weapon against SCD. Its effectiveness has been demonstrated in many prospective trials and the use of the ICD is fully enclosed within the current guidelines for the prevention of SCD. Guidelines do not, however, replace the physician's judgement and experience to correctly evaluate the patient's status. ICD therapy in the primary and secondary prevention of heart failure, which is often accompanied by a high risk of SCD is, however, not justified without guideline-adjusted therapy.

Sudden death secondary to cardiac arrhythmias: mechanisms and treatment strategies

PURPOSE OF REVIEW

This article reviews mechanisms and available therapeutic options for arrhythmias leading to sudden cardiac death in patients with coronary artery disease.

RECENT FINDINGS

Intensive efforts have led to a better understanding of the pathophysiology and various treatments of sudden cardiac death. Antiarrhythmic medications have not demonstrated a survival benefit. Beta-adrenergic blocking agents have been revalidated in recent studies to improve survival and reduce risk of sudden cardiac death in patients with myocardial infarction. Angiotensin-converting enzyme inhibitors and aldosterone antagonists should also be used in these patients. Data from randomized trials demonstrate significant survival benefit with an implantable cardioverter-defibrillator and indications have expanded. Patients with established ischemic cardiomyopathy do not require electrophysiologic studies for induction of tachyarrhythmias based on these trials. One recent trial did not demonstrate mortality reduction with implantable defibrillators in patients with recent myocardial infarction. Devices may not provide survival benefit in patients with advanced New York Heart Association class IV heart failure.

SUMMARY

The incidence of arrhythmia-related sudden death in the general population remains relatively high. Better risk stratification tools are needed to identify high-risk patients in the general population and in those with known coronary disease and to exclude low-risk patients.

Fungal infection of implantable cardioverter-defibrillators: Case series of five patients managed over 22 years

BACKGROUND

With the increasing use of implantable cardioverter-defibrillators (ICDs), device complications are becoming more common. Fungal-related ICD infections have rarely been reported, and little is known about the presentation, prevalence, and treatment options for these morbid infections.

OBJECTIVES

The purpose of this study was to characterize the clinical features, treatment, and outcomes of patients with fungal ICD infections.

METHODS

We performed a retrospective review of ICD procedures performed at a single academic center and identified all ICD-related infections managed between 1983 and 2005.

RESULTS

Among a total of 3,648 ICD-related procedures performed between 1983 and 2005, we identified 47 (1.3%) cases of ICD infections, of which 5 (0.1%) were due to a fungal pathogen. Fungal infections were more likely to be associated with abdominal devices, to have a local rather than systemic infection, and to have a longer duration from the original implant to presentation. All patients were treated with ICD system explantation and antifungal therapy.

CONCLUSION

Fungal infection of ICDs is a rare but serious complication of device implantation that must be treated aggressively with complete hardware explantation and prolonged antifungal therapy. Because most infections are late complications and have indolent onsets, a high level of clinical suspicion is required for early diagnosis.

Effects of Angiotensin Converting Enzyme Inhibitor and Angiotensin II Receptor Blocker on Ventricular Defibrillation Threshold

BACKGROUND

Angiotensin converting enzyme (ACE) inhibitors and Angiotensin II (AII) receptor blockers have previously been shown to be beneficial in treating patients with not only hypertension but also with cardiovascular diseases. Therefore, such drugs may potentially be used in patients with an implantable cardioverter defibrillator (ICD) who show cardiac dysfunctions.

OBJECTIVE

This study aimed to determine effects of short-term administration of the ACE inhibitor (CV-3317) and the AII receptor blocker (CV-11974, an active form of candesartan) on internal defibrillation threshold (DFT) in anesthetized canine hearts.

METHODS

DFTs were evaluated using a "hot can" defibrillation lead system in: (a) seven dogs following three intravenous administrations of 20 cc saline; (b) 11 dogs that received intravenous CV-3317 doses of 1 mg/kg, 10 mg/kg, and 50 mg/kg; and in (c) 10 dogs that were intravenously given 0.1 mg/kg, 1 mg/kg, and 10 mg/kg CV-11974. DFTs were determined using a "down-up down-up" protocol.

RESULTS

Mean DFT delivered energies at baseline and following three consecutive intravenous saline injections were 16.4 +/- 9.3 J, 15.3 +/- 7.5 J, 15.9 +/- 7.1 J, and 15.5 +/- 5.6 J, respectively. Those at baseline and following 1 mg/kg, 10 mg/kg, and 50 mg/kg intravenous CV-3317 were 12.9 +/- 6.4 J, 12.2 +/- 6.4 J, 11.0 +/- 6.6 J, and 11.9 +/- 6.6 J, respectively. Similarly, those at baseline and after 0.1 mg/kg, 1 mg/kg, and 10 mg/kg CV-11974 were 13 +/- 6.6 J, 12.5 +/- 6 J, 12.9 +/- 5.8 J, and 13.2 +/- 6.6 J, respectively. There were no significant differences between DFT at baseline and the others in each treatment group.

CONCLUSIONS

Since an ACE inhibitor and an AII receptor blocker did not alter DFT, such drugs may be useful in ICD patients without a decrease in safety margins.

Impact of the multicenter automatic defibrillator implantation trial on clinical practice

BACKGROUND

The first multicenter automatic defibrillator implantation trial (MADIT-I) was a landmark study that identified a significant reduction in mortality among high-risk patients with ischemic cardiomyopathy treated prophylactically with an implantable cardioverter defibrillator (ICD), yet the direct and indirect impact of this trial on clinical practice is unknown.

METHODS

We performed a retrospective analysis of the 679 patients who underwent primary ICD implantation between 1994 and 2000 at a single academic center. The baseline characteristics of each patient were determined at the time of ICD implantation, and the vital status of all patients was determined as of January 1, 2004.

RESULTS

The number of patients who received an ICD based on the MADIT-I criteria increased from 1.4% in 1994 to 6.1% in 2000. An additional 60 patients were identified that met many but not all of the trial criteria and consisted of patients with a history of a recent revascularization or myocardial infarction, syncope, or an ejection fraction >or=35%. The number of patients who received ICDs in this expanded MADIT-I subset also grew from 5.6% in 1994 to 14.6% in 2000. Mortality during a mean follow-up of 4.7 years was significantly higher in the MADIT-I group than in the expanded MADIT-I, or the remaining primary prevention and secondary prevention subsets.

CONCLUSION

The MADIT-I has not only led to an increase in the number of patients undergoing prophylactic ICD implantation, but in clinical practice it has also been extrapolated to a broader population that has a different degree of risk than originally studied.

IEGM-online based evaluation of implantable cardioverter defibrillator therapy appropriateness

Appropriate and inappropriate therapies of implantable cardioverter defibrillators have a major impact on morbidity and quality of life in ICD recipients. Intracardiac electrograms (IEGMs) stored in the ICD have been shown to be essential for differentiating appropriate and inappropriate ICD therapies. The recently introduced third generation of ICD Home Monitoring offers remotely transmitted IEGMs (IEGM-online). Hence, the appropriateness of ICD therapies might be remotely assessed. Validation of these electrograms is currently being performed in the RIONI study. A total of 210 episodes will be collected by about 40 European clinical centers. The study primarily investigates whether the IEGM-online based evaluation of the appropriateness of the ICD's therapeutic decision following a tachyarrhythmia episode detection is equivalent to the evaluation based on the complete ICD episode holter. The evaluation is independently performed by an expert board of three experienced ICD investigators. The equivalence of the two methods is accepted if the conclusions deviate for less than 10% of all evaluated IEGMs. Secondary endpoints investigate the IEGM-online usefulness in more detail. The conclusion of the study is expected by mid of 2007. RIONI has successfully been started for proving the reliability of IEGM-online. The expected results will significantly influence the efficacy of Home Monitoring based patient management.

The RIONI study rationale and design: validation of the first stored electrograms transmitted via home monitoring in patients with implantable defibrillators

Appropriate and inappropriate therapies of implantable cardioverter defibrillators (ICDs) have a major impact on morbidity and quality of life in ICD recipients. The recently introduced home monitoring of ICD devices is a promising new technique which remotely offers information about the status of the system. Stored intracardiac electrograms (IEGMs), which are essential for correct classification of appropriate and inappropriate ICD discharges, have until now not been available with ICD home monitoring on a day-by-day basis because of limitations of transferable data. We demonstrate the first compressed IEGMs daily transferable via home monitoring (IEGM-online). Validation of these electrograms will be performed in the Reliability of IEGM-Online Interpretation (RIONI) study. A total of 210 episodes of stored IEGMs will be collected by at least 12 European centres. The primary endpoint of this study is to investigate whether the IEGM-online based evaluation of the appropriateness of the ICDs therapeutic decision following episode detection is equivalent to the evaluation based on the complete ICD episode Holter extracted from the IEGM stored. The evaluation is independently done by an expert board of three experienced ICD investigators. The equivalence of the two methods is accepted if the evaluations yield a different conclusion for <10% of all evaluated IEGMs. The conclusion of the study is expected at the beginning of 2007. If RIONI successfully validates IEGMs transmitted via home monitoring, a strong basis for the use of this promising technique will be established.

Clinical significance of the electrophysiologic study (EPS)-guided therapy for the secondary prevention of ventricular tachycardia

BACKGROUND

Although electrophysiologic study (EPS) is one of the most reliable methods for selecting preventive therapy for patients with sustained ventricular tachycardia (VT), VT may recur during EPS-guided effective therapy; therefore, the importance of implantable cardioverter-defibrillator (ICD) has been emphasized. In this study, the prognoses of VT patients were evaluated to clarify the importance of EPS-guided therapy for the secondary prevention of VT.

METHODS AND RESULTS

The study population consisted of 99 consecutive patients with a history of sustained VT, which was inducible in EPS. The VT induction protocol used 1-3 extrastimuli and rapid ventricular pacing at 2 right ventricular sites and included additional isoproterenol infusion. ICD implantation was applied to all patients with an episode of hemodynamically unstable VT, regardless of the result of preventive therapy. For preventive therapy, an antiarrhythmic drug and/or catheter ablation were selected, and they were defined as being effective in the EPS-guided therapy when the induction of VT was completely prevented. When no therapy was effective for prevention, an antiarrhythmic drug was prescribed under ICD implantation. During the follow-up period of 19+/-20 months, VT recurred in 17 of 32 patients (53%) in the ineffective group and in 10 of 67 patients (15%) in the effective group (p=0.0001). The therapies used in the effective group were class I antiarrhythmic drug in 9, class III in 15, and catheter ablation in 35 patients. Between the patients with and without VT recurrence, there were no significant differences in the left ventricular ejection fraction and the maximum number of repetitive ventricular responses that remained in VT induction in EPS.

CONCLUSIONS

Although VT may recur in up to 15% of patients with EPS-guided effective therapy, the recurrence rate was significantly reduced in comparison to that in the ineffective group. EPS-guided therapy may be useful to reduce the clinical recurrence of VT, as well as the action of ICD.

Amiodarone and optic neuropathy: the heart of the matter

Amiodarone is one of the most effective antiarrhythmic drugs currently available. Although a subject of intense controversy, a causal link between amiodarone and optic neuropathy has never been firmly established. Indications for treatment with amiodarone are outlined, and features of the optic neuropathy in patients on amiodarone are compared with those of nonarteritic anterior ischemic optic neuropathy. An approach to patients treated with amiodarone who present with optic neuropathy is outlined, and suggestions for a registry and prospective study of such patients are presented.

Sudden Cardiac Death Unresponsive to Implantable Defibrillator Therapy: An Urgent Target for Clinicians, Industry and Government

A major expansion in utilization of implantable cardioverter-defibrillators (ICDs) is anticipated based on the results of randomized clinical trials (RCT) that demonstrate increased survival in a sizable population of patients with reduced left ventricular function. However, if RCT accurately reflect clinical practice, then a substantial proportion of patients will die suddenly despite ICD implantation. ICD-unresponsive sudden cardiac death (SCD) has been recognized since the initial ICD experience. Yet, despite 25 years of technical advances, the frequency of ICD-unresponsive SCD has not declined. Pooled analysis of RCT indicates a crude rate of ICD-unresponsive SCD of 5%. This may not cause alarm in an average practice, but it comprises about 30% of cardiac deaths. Meta-analyses of RCT show that ICD therapy is associated with a relative risk reduction of SCD of approximately 60%, far less than the greater than 90% efficacy that many expect. The suboptimal performance of ICD therapy accounts for the failure of some RCT to achieve statistically significant effects on survival. The number of patients with ICD-unresponsive SCD is highly correlated with the number of cardiac deaths among control patients as well as ICD recipients. Otherwise, no definite patterns have emerged that clearly distinguish this mode of demise from other modes of cardiac death. Retrospective post-hoc analyses have not revealed distinguishing characteristics of patients with ICD-unresponsive SCD with respect to clinical variables, pre-terminal symptoms or to the setting of the terminal event. Despite advanced storage capabilities of implanted devices, almost no information has become available from RCT regarding the terminal rhythm or the response of the ICD. These observations have implications for clinical management and research. Candidates for ICD implantation based on RCT should be accurately informed about the residual risk of SCD. Investigators seeking to identify populations likely to benefit from ICD therapy based on SCD incidence should recognize that a significant fraction may not respond to ICD therapy. Reducing the incidence of ICD-unresponsive SCD would substantially improve survival and cost-effectiveness related to ICD therapy. Close cooperation between clinicians, investigators and representatives of industry and government is urgently needed to develop strategies to identify patients prone to ICD-unresponsive SCD, to determine its mechanisms and to develop methods of prevention and treatment.

High Incidence of Appropriate and Inappropriate ICD Therapies in Children and Adolescents with Implantable Cardioverter Defibrillator

Appropriate and inappropriate therapies of implantable cardioverter defibrillators have a major impact on morbidity and quality of life in ICD recipients, but have not been systematically studied in children and young adults during long-term follow-up. ICD implantation was performed in 20 patients at the mean age of 16 +/- 6 years, 11 of which had prior surgical repair of a congenital heart defect, 9 patients had other cardiac diseases. Implant indications were aborted sudden cardiac death in six patients, recurrent ventricular tachycardia in 9 patient, and syncope in 5 patients. Epicardial implantation was performed in 6 and transvenous implantation in 14 patients. Incidence, reasons and predictors (age, gender, repaired congenital heart disease, history of supraventricular tachycardia, and epicardial electrode system) of appropriate and inappropriate ICD therapies were analyzed during a mean follow-up period of 51 +/- 31 months range 18-132 months. There were a total 239 ICD therapies in 17 patients (85%) with a therapy rate of 2.8 per patient-years of follow-up. 127 (53%) ICD therapies in 15 (75%) patients were catagorized as appropriate and 112 (47%) therapies in 10 (50%) patients as inappropriate, with a rate of 1.5 appropriate and 1.3 inappropriate ICD therapies per patient-years of follow-up. Time to first appropriate therapy was 16 +/- 18 months. Appropriate therapies were caused by ventricular fibrillation in 29 and ventricular tachycardia in 98 episodes. Termination was successful by antitachycardia pacing in 4 (3%) and by shock therapy in 123 episodes (97%). Time to first inappropriate therapy was 16 +/- 17 months. Inappropriate therapies were caused by supraventricular tachycardia in 77 (69%), T wave oversensing in 19 (17%), and electrode defect in 16 episodes (14%). It caused shocks in 87 (78%) and only antitachycardia pacing in 25 episodes (22%). No clinical variable could be identified as predictor of either appropriate or inappropriate ICD therapies. There is a high rate of ICD therapies in young ICD recipients, the majority of which occur during early follow-up. The rate of inappropriate therapies is as high as 47% and is caused by supraventricular tachycardia and electrode complications in the majority of cases. Prospective trials are required to establish preventative strategies of ICD therapies in this young patient population.

Indications for an implantable cardioverter defibrillator (ICD)

Since the first clinical use of implantable defibrillator in human, the technology and the function of implantable cardioverter-defibrillator (ICD) have been much improved and now, ICD can be implanted within the chest wall. ICD is the most reliable therapy to prevent sudden cardiac death (SCD) in patients with documented VT/VF and the efficacy is most clear in patients with depressed heart function. It is now extended as a tool of the primary prevention of SCD in high risk patients after myocardial infarction. However, such beneficial effect is not applicable to DCM though patients might have depressed heart function. ICD is not free from procedure- or device-related problems which need to be resolved. From unknown causes, VT/VF might recur in an incessant form and an emergency admission is needed. Therefore, even during ICD therapy, patients often require antiarrhythmic drugs or catheter ablation.

Implantable Cardioverter Defibrillator Events in Patients with Asymptomatic Nonsustained Ventricular Tachycardia:

Primary prevention trials have demonstrated that patients with coronary disease, reduced left ventricular function, and nonsustained ventricular tachycardia (NSVT) have improved survival with implantable cardioverter defibrillator (ICD) therapy, presumably secondary to effective termination of life-threatening arrhythmias. However, stored intracardiac electrograms were not always available and specific arrhythmias leading to ICD therapy were not always known. We examined the occurrence of ICD events in 51 consecutive patients who match the described patient profile to determine the frequency of appropriate and inappropriate ICD therapy. ICD detections were noted in 18 (35%) patients during a median follow-up period of 13.1 months. Appropriate therapy for sustained ventricular tachycardia (VT)/ventricular fibrillation (VF) occurred in 11 (22%) patients, with appropriate shocks in 8 (16%) patients and appropriate antitachycardia pacing (ATP) in 4 (8%) patients. The time to first appropriate therapy occurred at a mean of 17 +/- 12 months (median 18 months, range 3-36 months). Inappropriate therapy occurred in 5 (10%) patients with inappropriate shocks in 4 patients and inappropriate ATP in 2 patients. Inappropriate therapy was delivered for supraventricular arrhythmias (SVAs) in 4 patients and for T wave oversensing in 1 patient. The reason for shock therapy was unknown in 1 patient (2%) due to ICD malfunction. The mean arrhythmia rate leading to appropriate therapy for VT/VF was 232 +/- 72 beats/min (range 181-400 beats/min), and the mean rate leading to inappropriate therapy for SVT was 168 +/- 10 beats/min (range 160-180 beats/min). Patients with coronary disease and asymptomatic NSVT commonly receive appropriate defibrillator therapy. These results support the need for ICD implantation for primary prevention, with attention to careful programming of the detection rate to prevent inappropriate therapy.

Significance of External Cardioversion Induced Atrial Tachyarrhythmias

External cardioversion is used to stop VT or VF in emergency. Supraventricular tachyarrhythmias are sometimes noted after cardioversion in patients known to be previously in sinus rhythm. The purpose of the study was to evaluate the significance of supraventricular tachyarrhythmias induced by external cardioversion. The study population consisted of 22 patients who developed supraventricular tachyarrhythmias after transthoracic cardioversion (300 J) delivered to stop a VT or VF induced by electrophysiological study. Defibrillation used monophasic waveform. Supraventricular tachyarrhythmias complicated 6% of cardioversions for VT; before cardioversion, all patients were in sinus rhythm. After cardioversion, three patients developed a paroxysmal reentrant supraventricular tachycardia (PSVT), which was stopped by atrial pacing. The remaining patients developed AF that lasted from 3 minutes to 24 hours (n = 4). One patient remained in AF. AF developed after a sinus pause or bradycardia, which was due to the interruption of VT or VF in nine patients or was noted just when VT or VF stopped (n = 10). The analysis of clinical data indicated that all three patients who presented a PSVT had a history of PSVT. Among patients who developed a sinus pause dependent AF, two had a history of AF. Among ten patients who developed AF at the time of cardioversion, three had a history of AF. During follow-up (1-9 years), no patient without a history of AF developed spontaneous AF, but patients with history of tachycardias had arrhythmia recurrences. The mechanism of cardioversion related tachycardias can be a pause related dispersion of atrial refractoriness or an adrenergic reaction induced by VT or VF, factors that precipitate arrhythmias in patients with history of atrial arrhythmias (one third of patients). In conclusion, supraventricular tachyarrhythmia is relatively frequent after external cardioversion for ventricular tachyarrhythmia, has no prognostic significance in patients without previous history of atrial arrhythmias, but in those with history of tachycardias is associated with a high risk of recurrence.

Analysis of implantable cardioverter defibrillator therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial

INTRODUCTION

The implantable cardioverter defibrillator (ICD) is commonly used to treat patients with documented sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Arrhythmia recurrence rates in these patients are high, but which patients will receive a therapy and the forms of arrhythmia recurrence (VT or VF) are poorly understood.

METHODS AND RESULTS

The therapy delivered by the ICD was examined in 449 patients randomized to ICD therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. Events triggering ICD shocks or antitachycardia pacing (ATP) were reviewed for arrhythmia diagnosis, clinical symptoms, activity at the onset of the arrhythmia, and appropriateness and results of therapy. Both shock and ATP therapies were frequent by 2 years, with 68% of patients receiving some therapy or having an arrhythmic death. An appropriate shock was delivered in 53% of patients, and ATP was delivered in 68% of patients who had ATP activated. The first arrhythmia treated in follow-up was diagnosed as VT (63%), VF (13%), supraventricular tachycardia (18%), unknown arrhythmia (3%), or due to ICD malfunction or inappropriate sensing (3%). Acceleration of an arrhythmia by the ICD occurred in 8% of patients who received any therapy. No physical activity consistently preceded arrhythmias, nor did any single clinical factor predict the symptoms of the arrhythmia.

CONCLUSION

Delivery of ICD therapy in AVID patients was common, primarily due to VT. Inappropriate ICD therapy occurred frequently. Use of ICD therapy as a surrogate endpoint for death in clinical trials should be avoided.

Prospective randomized comparison of two defibrillation safety margins in unipolar, active pectoral defibrillator therapy

Various techniques are used to establish defibrillation efficacy and to evaluate defibrillation safety margins in patients with an ICD. In daily practice a safety margin of 10 J is generally accepted. However, this is based on old clinical data and there are no data on safety margins using current ICD technology with unipolar, active pectoral defibrillators. Therefore, a randomized study was performed to test if the likelihood of successful defibrillation at defibrillation energy requirement (DER) + 5 J and + 10 J is equivalent. Ninety-six patients (86 men; age 61.0 +/- 10.3 years; ejection fraction 0.341 +/- 0.132; coronary artery disease [n = 65], dilated cardiomyopathy [n = 18], other [n = 13]) underwent implantation of an active pectoral ICD system with unidirectional current pathway and a truncated, fixed tilt biphasic shock waveform. The defibrillation energy requirement (DER) was determined with the use of a step-down protocol (delivered energy 15, 10, 8, 6, 4, 3, 2 J). The patients were then randomized to three inductions of ventricular fibrillation at implantation and three at predischarge testing with shock strengths programmed to DER + 5 J at implantation and + 10 J at predischarge testing or vice versa. The mean DER in the total study population was 7.88 +/- 2.96 J. The number of defibrillation attempts was 288 for + 5 J and 288 for + 10 J. The rate of successful defibrillation was 94.1% (DER + 5 J) and 98.9% (DER + 10 J; P < 0.01 for equivalence). Charge times for DER + 5 J were significantly shorter than for DER + 10 J (3.65 +/- 1.14 vs 5.45 +/- 1.47 s; P < 0.001). A defibrillation safety margin of DER + 5 J is associated with a defibrillation probability equal to the standard DER + 10 J. In patients in whom short charge times are critical for avoidance of syncope, a safety margin of DER + 5 J seems clinically safe for programming of the first shock energy.