ICD-Antiarrhythmic Drug and ICD-Pacemaker Interactions

Implantable Cardioverter Defibrillators. Antiarrhythmic drugs and separate bradycardia pacing systems are prescribed commonly in patients with implantable cardioverter defibrillators (ICDs). Adverse effects of antiarrhythmic drugs on ICD function and adverse interactions between ICDs and pacemakers have been documented. The effect of antiarrhythmic drugs on the defibrillation threshold (DFT) in patients has not been well assessed. Most studies have been performed in animal models in which cardiac function was normal and drug doses were supraphysiologic. In addition, most studies have utilized monophasic defibrillation shock waveforms and epicardial lead systems. Despite the lack of clinical data applicable to current defibrillation systems, it appears that chronic amiodarone administration causes a significant DFT increase. In addition, antiarrhythmic drugs can influence antitachycardia pacing and tachycardia sensing. Defibrillation shocks can cause transient failure of pacemaker sensing and pacing, and cause spurious pacemaker reprogramming. Pacemaker function can result in ICD oversensing, leading to inappropriate therapy, or cause ICD undersensing, potentially resulting in failure to deliver therapy during ventricular fibrillation. The susceptibility of an ICD to undersensing appears related to the amplitude of the pacing stimulus artifact recorded by the ICD rate-sensing circuit and to the characteristics of the fibrillation electrogram. Preliminary data suggest that undersensing of ventricular fibrillation by current ICDs is an unlikely event.     

心脏同步化治疗慢性心力衰竭疗效及临床经验总结

目的总结心脏同步化起搏治疗慢性心力衰竭的疗效及临床经验。方法回顾性分析接受再同步化治疗的26例慢性心力衰竭伴心室内传导延迟患者的临床资料,着重分析再同步化治疗的方法和疗效。结果患者均接受心脏再同步化治疗,年龄（57.0±11.6）岁,男22例（84.6%,22/26）,其中再同步化转复除颤器16例（62%,16/26）,非缺血性心肌病22例（85%,22/26）,9例（35%,9/26）有慢性房性心律失常,2例需外科植入左心室心外膜电极。心脏再同步化治疗后QRS波时限由（161±29）ms缩短为（137±15）ms,差异有统计学意义（P≤0.01）;患者心功能均有明显改善,心功能分级比治疗前降低,差异有统计学意义[（1.9±0.9）级vs.（3.2±0.6）级,P≤0.01];射血分数比治疗前提高,差异有统计学意义（34.0%±13.3%vs.24.9%±6.8%,P≤0.01）。6分钟步行距离、血清脑钠肽浓度以及左心室舒张或收缩末内径均有显著改善（P≤0.05）。术后随访（2.5±1.7）年,7例（27%,7/26）死亡,其中2例心源性猝死。结论心脏同步化起搏治疗显著改善慢性心力衰竭患者心功能,逆转心肌重构,减低病死率。     

Depression and severe heart failure: benefits of cardiac resynchronization therapy

Depression and Cardiac Resynchronization Therapy . Background: The relationship between depression and heart failure is neither coincidental nor trivial, since depression is a powerful predictor of re‐hospitalization and mortality. We prospectively studied the prevalence and impact of depression on the clinical outcomes of patients attending for cardiac resynchronization therapy (CRT). We specifically examined whether patients with depression have a different rate of response to CRT and whether CRT has an effect on depressive symptoms. Methods: Sixty‐eight recipients of CRT systems were included. The depressive status was evaluated before implant and after 6 months by a structured diagnostic interview measuring Diagnostic and Statistical Manual of Mental Disorders (DSM‐IV) criteria of major depression and by a self‐report questionnaire (Center for Epidemiological Studies Depression Scale, CES‐D). The CRT response was assessed at 6 months by a clinical composite score. Results: At inclusion, DSM‐IV criteria of major depression were identified in 41% of the population, while using the self‐report questionnaire 65% were observed to have mild to major depressive symptoms (CES‐D ≥ 16). Only 4 patients were taking antidepressants. At 6 months, 75% were considered responders to CRT. Response to CRT did not differ between those with and without depression at baseline. The rate of patients with depression at 6 months was significantly lower in responders to CRT compared with nonresponders. Conclusions: We found a high prevalence of depressive symptoms in patients receiving CRT systems. Patients with depression should not be excluded from CRT, because they demonstrate a similar rate of response than the persons without depression and the responders are less likely to be depressed at 6 months. (J Cardiovasc Electrophysiol, Vol. 23, pp. 631–636, June 2012)     

Evaluation of Antiarrhythmic Drug Efficacy in Patients with an ICD:

There are a number of novel ways in which implantable cardioverter defibrillator (ICD) endpoints can be used in clinical trials to evaluate antiarrhythmic drugs. The advances in ICD technology (storage, retrieval, and accurate interpretation of ICD electrograms) expand the potential to include the use of an ICD endpoint as a clinical surrogate for sudden death. The ICD also provides the necessary safety net to test new drugs. The frequent need for antiarrhythmic drugs in patients already fitted with an ICD (e.g., for atrial fibrillation) necessitates knowledge of the drugs' effect on defibrillator threshold. There are interpretative problems and challenges associated with all types of ICD trials. A particular difficult issue is the degree to which the results of data on antiarrhythmic drug efficacy and safety acquired in the context of an ICD endpoint trial might be extrapolated to patient populations in which the device is not used. These and other challenging issues are discussed, with the goal of enhancing the design and interpretation of clinical trials featuring ICD endpoints.     

Arrhythmias in Hypertrophic Cardiomyopathy

Arrhythmias in Hypertrophic Cardiomyopathy. Arrhythmias, particularly atrial fibrillation and nonsustained ventricular tachycardia, are common in adult patients with hypertrophic cardiomyopathy. Atrial fibrillation has long been thought to herald an ominous prognosis, but this is probably not the case, and in the majority of patients atrial fibrillation can be controlled without accelerated symptomatic deterioration. Uncontrolled observations indicate that low dose amiodarone may be the most useful drug in paroxysmal and chronic atrial fibrillation. The detection of nonsustained ventricular tachycardia on ambulatory electrocardiogram monitoring remains the single most useful indicator of the risk of sudden death in the adult patient, and the treatment of choice is again low dose amiodarone. The mechanism of sudden death, and the mode of action of amiodarone in preventing it, are not known for certain in the majority of patients. The risk of sudden death is higher in children and adolescents, but arrhythmias are less common, and no useful predictive marker of increased risk has been found. The role of invasive electrophysiological studies and the place of the implantable cardioverter-defibrillator in hypertrophic cardiomyopathy have not yet been established.     

Ventricular arrhythmias in congestive heart failure

Despite advances in the treatment of congestive heart failure (CHF), the mortality rate continues to be high. A large number of the deaths are sudden, presumably due to ventricular arrhythmias. Complex ventricular arrhythmias are recorded in as many as 80% of patients with CHF, with nonsustained ventricular tachycardia occurring in 40%. The latter appears to be an independent predictor of mortality. Chronic structural abnormalities responsible for CHF may be the basis for the capability of a ventricle to support life-threatening arrhythmias, which are triggered by premature ventricular contractions. The pathogenesis of arrhythmias is multifactorial. Electrolyte abnormalities, ischemia, catecholamines, inotropic and antiarrhythmic drugs may worsen arrhythmias and increase susceptibility of a ventricle to sustained arrhythmias. Beta-adrenergic blockers and angiotensin-converting enzyme inhibitors have a beneficial effect. The role of various drugs in the pathogenesis and treatment of ventricular arrhythmias is discussed. The efficacy of antiarrhythmic therapy targeted to asymptomatic nonsustained ventricular tachycardia, in order to prevent sudden death, is controversial. Pharmacotherapy guided by electrophysiologic testing is the treatment of choice for patients who have manifest sustained ventricular tachycardia, but patients resuscitated from ventricular fibrillation may require automatic implantable cardioverter defibrillator.     

Implantable Cardioverter Defibrillator Therapy for Life-Threatening Arrhythmias in Young Patients

Objectives: This study examined the indications, efficacy and outcomes of implantable cardioverter defibrillator (ICD) use in the pediatric population. Background: ICDs are first-line therapy for adults resuscitated from sudden cardiac death (SCD) or at high risk for life-threatening ventricular arrhythmias. Use of ICDs in children and young adults is infrequent and there are few data regarding this group. Methods: We abstracted and analyzed data for all patients in whom ICDs were implanted. Results: A total of 38 devices were implanted in 27 patients. Age ranged from 6 to 26 years (mean, 14) and weight ranged from 16 to 124 kg (mean, 47). Diagnoses included long QT syndrome (9), hypertrophic cardiomyopathy [6], repaired congenital heart disease [5];, and idiopathic ventricular tachycardia/fibrillation [4]. Indications comprised resuscitated SCD [15], syncope [9], and life-threatening ventricular arrhythmia [3]. Initial device placement was infraclavicular in 13, abdominal in 13 and intrathoracic in 1. Epicardial leads were used with 5 systems. A single coil lead was used in 17. Seven patients, all previously resuscitated from SCD, experienced 88 appropriate successful discharges. There were 6 inappropriate discharges in 3 patients. Mean time to device replacement was 3.1 years (n = 11). Complications included 2 infected systems, 2 lead dislodgments, 2 lead fractures, 1 post-pericardiotomy syndrome, 1 adverse event with defibrillation threshold (DFT); testing, and 1 patient with psychiatric sequelae. No deaths occurred with implanted ICDs. Conclusions: These data demonstrate that ICDs provide safe and effective therapy in young patients. The indications for ICDs as primary preventive therapy remain uncertain.     

Mortality of heart failure patients after cardiac resynchronization therapy: identification of predictors

Introduction: A direct comparison of survival benefits between cardiac resynchronization therapy‐pacemaker (CRT‐P) and defibrillator (CRT‐D) was not yet performed, leaving clinicians to question whether CRT‐P alone is enough to protect congestive heart failure (CHF) patients from sudden cardiac death and whether CRT‐D should be implanted to all CHF patients indicated for biventricular pacing. This study attempts to make this type of comparison in a large CHF population and seeks to identify predictors of death in patients with different comorbidities. Methods and Results: Study population consisted of 542 consecutive patients who were implanted with either CRT‐P (N = 147) or CRT‐D (N = 395) between 1999 and 2005. Patients' clinical and follow‐up data were entered in a prospective registry and retrieved for analysis. The primary endpoint of this study was all‐cause mortality during follow‐up. Total all‐cause mortality was significantly lower among patients with CRT‐D (18.5% vs. 38.8% of CRT‐P, χ²= 25.11, P < 0.001). Patients with one of three comorbidities—chronic renal failure (OR = 4.885, P = 0.005), diabetes mellitus (OR = 4.130, P = 0.003), and history of atrial fibrillation (OR = 1.473, P = 0.036)—appeared to have higher risk of death, while treatment with beta‐blocker (OR = 0.330, P = 0.002) or CRT‐D device (OR = 0.334, P = 0.003) seemed to be associated with lower mortality. Conclusions: Data from this nonrandomized study indicate that CRT‐D has additional survival benefits over CRT‐P. Given these findings, CRT‐D should be recommended to most CHF patients with indications for biventricular pacing. After CRT implant, chronic renal failure, diabetes mellitus, and history of atrial fibrillation are strong independent predictors of death.     

Dofetilide reduces the frequency of ventricular arrhythmias and implantable cardioverter defibrillator therapies

Dofetilide Reduces VT/VF and ICD Therapies . Background: Patients with an implanted cardioverter defibrillator (ICD) and ventricular arrhythmias leading to ICD therapies have poor clinical outcomes and quality of life. Antiarrhythmic agents and catheter ablation are needed to control these arrhythmias. Dofetilide has only been approved for the treatment of atrial fibrillation. The role of dofetilide in the control of ventricular arrhythmias in patients with an ICD has not been established. Objective: Evaluate the safety and efficacy of dofetilide in a consecutive group of patients with an ICD and recurrent ventricular tachycardia (VT) and/ or ventricular fibrillation (VF) after other antiarrhythmic drugs have failed to suppress these arrhythmias. Methods: We studied 30 patients (age 59 ± 11; 5 women) with symptomatic VT or VF and ICDs for secondary prevention of sudden cardiac death. These patients had an average of 1.8 ± 4.5 episodes of VT/VF per month despite antiarrhymic therapy. Twenty‐one patients (70%) had recurrent appropriate ICD therapies prior to initiation of dofetilide, and 9 (30%) VTs below the programmed detection rate of the ICD. Twenty‐three patients (77%) had coronary artery disease. Mean ejection fraction was 30 ± 14% and 26/30 (87%) had congestive heart failure. All patients had previously failed 2 ± 1 antiarrhythmic drugs including amiodarone (n = 19) and sotalol (n = 10). Results: During the first month of treatment, 25 patients (83%) had complete suppression of VT/VF and of the 21 patients with ICD therapies 16 (76%) had no therapies during the first month of treatment. During a follow‐up period of 32 ± 32 months, dofetilide reduced the monthly episodes of VT/VF from 1.8 ± 4.5 to 1.0 ± 3.5 (P = 0.006). Monthly ICD therapies decreased from 0.9 ± 1.4 to 0.4 ± 1.7 (P = 0.037). In 9 patients that presented with slow VTs under the ICD detection zone, dofetilide reduced monthly VT/VF episodes from 0.7 ± 0.6 to 0.1 ± 0.1 (P = 0.01) and 6 (67%) had no further ICD therapies. Dofetilide was discontinued in 13 patients (43%) after 24 ± 30 months due to failure to control VT/VF (n = 7), placement of a left ventricular assist device (n = 3), catheter ablation (n = 1), heart transplantation (n = 1), and left ventricular restoration surgery (n = 1). There were 7 documented deaths (2 patients died suddenly; 3 patients of progressive heart failure; and 2 of non‐cardiac causes). Conclusions: In patients with an ICD and ventricular arrhythmias, dofetilide decreases the frequency of VT/VF and ICD therapies even when other antiarrhythmic agents, including amiodarone, have previously been ineffective. Recurrences still occur in some patients requiring catheter ablation, mechanical support, or heart transplantation. (J Cardiovasc Electrophysiol, Vol. 23 p. 296‐301, March 2012.)     

Arrhythmia detection by dual-chamber implantable cardioverter defibrillators. A review of current algorithms.

This article reviews the arrhythmia detection criteria currently available in dual-chamber implantable cardioverter defibrillators (ICDs), and describes the implementation and performance of various detection algorithms. Nearly all criteria implemented in single-chamber devices appear to have been included in dual-chamber ICDs. However, two different strategies can be distinguished: the first adds dual-chamber inhibition criteria to a single-chamber detection configuration; the second is a new approach entirely based on a dual-chamber detection scheme. Despite widely available clinical data, an analysis of the implemented detection indexes, arrhythmia characteristics (induced vs spontaneous, minimum duration), device programming (detection rate, programme maintenance and tuning during follow-up), and different storage capabilities among various ICD models, leaves the results of these studies ultimately ambiguous. New algorithms are under study, but only protocols using a single set of arrhythmias and the same programming for all devices may allow relevant comparisons of the performances of detection algorithms. Furthermore, a criterion is required to distinguish reliably between haemodynamically stable and unstable tachycardias, not simply based on rate, but including the underlying cardiac function.     

Intradevice interaction in a dual chamber implantable cardioverter defibrillator preventing ventricular tachyarrhythmia detection

Failure to detect ventricular tachycardia and/or ventricular fibrillation by implantable cardioverter defibrillators (ICDs) is a rare but serious problem. We report a case of failure to detect an episode of induced ventricular tachycardia by a dual chamber ICD, due to abbreviation of ventricular detection window secondary to programmed pacing parameters and a rate-smoothing algorithm. In this patient, the intradevice interaction was corrected by programming rate-smoothing off. This report highlights the potentially lethal consequences of critical timing relationships among the pacing function, arrhythmia detection, and the characteristics of the arrhythmia when using a modern dual chamber ICD. Physicians responsible for patients with ICDs must be aware of such interactions.     

Clinical course and implantable cardioverter defibrillator therapy in postinfarction women with severe left ventricular dysfunction

BACKGROUND: There are limited data regarding implantable cardioverter defibrillator (ICD) therapy in postinfarction women with severe left ventricular dysfunction. The aim of this study was to evaluate the risk of cardiac events and effects of ICD therapy in women as compared to men enrolled in the Multicenter Automatic Defibrillator Implantation Trial II (MADIT II). METHODS AND RESULTS: Among 1,232 patients enrolled in MADIT II, there were 192 (16%) women and 1,040 (84%) men. When compared to men, women had an increased frequency of NYHA class > or =II (70 vs 63%; P = 0.067), hypertension (60% vs 52%; P = 0.047), diabetes (42% vs 34%; P = 0.027), and LBBB (25% vs 17%; P = 0.011), and less frequent CABG surgery (42% vs 60%; P < 0.001). The 2-year cumulative mortality in patients randomized to conventional therapy was not significantly different in women and men (30% and 20%, respectively; P = 0.19). Adjusting for relevant clinical covariates, the hazard ratios for ICD effectiveness were similar in women (0.57; 95% CI = 0.28-1.18; P = 0.132) and men (0.66; 95% CI = 0.48-0.91; P = 0.011). The risk of appropriate ICD therapy for VT/VF was lower in women than in men (hazard ratio = 0.60 for female vs male gender; 95% CI = 0.37-0.98; P = 0.039). CONCLUSIONS: MADIT II women had similar mortality and similar ICD effectiveness when compared to men. MADIT II women with ICDs had a lower risk of arrhythmic events with fewer episodes of ventricular tachycardia than men.     

Devices for the management of ventricular arrhythmias in cardiac failure

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

抗心律失常药在心力衰竭中的临床应用

医疗水平提升使心脏病患者的生存期延长,心力衰竭患病率亦呈上升趋势。心力衰竭患者常见并发心律失常,且发生心脏性猝死(SCD)的风险极高。如何防治心力衰竭,尤其是射血分数降低的心力衰竭(HFrEF)患者的心律失常及SCD,是临床面临的棘手问题。抗心律失常药的不良反应极大地限制了其在心力衰竭并心律失常中的临床应用,且药物防治SCD的作用极为有限。本文从临床角度,简述了近年来有关心力衰竭与心律失常的关联、抗心律失常药在心力衰竭临床应用的最新观点,为临床医师提供参考。     

CRT-D在慢性心力衰竭患者的临床应用

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