Effect of cardiac resynchronization therapy on the incidence of ventricular arrhythmias in patients with an implantable cardioverter-defibrillator.

BACKGROUND: Cardiac resynchronization therapy (CRT) reduces mortality in selected patients with heart failure. However, this result may not be entirely related to the beneficial hemodynamic effects of CRT. OBJECTIVES: The purpose of this study was to assess retrospectively the effect of CRT on the incidence of appropriate therapy in patients with an implantable cardioverter-defibrillator (ICD). METHODS: Sixty-five patients (48 men and 17 women; mean age 58 +/- 13 years) with an ICD (31 biventricular, 34 dual-chamber) were included in the study. Clinical, ECG, and ICD stored data and electrograms were collected. RESULTS: Biventricular and dual-chamber ICDs were implanted in 31 and 34 patients, respectively, who had either ischemic (n = 36) or dilated cardiomyopathy (n = 29). Thirty-two (49%) patients received > or =1 appropriate ICD therapy during follow-up of 11 +/- 8 months. Thirty-five percent and 62% of patients with biventricular (n = 11) and dual-chamber ICDs (n = 21), respectively, received appropriate ICD therapy during the follow-up period (odds ratio = 0.340, P = .048). Stratifying the patients according to underlying heart disease and ejection fraction resulted in an adjusted odds ratio = 0.239 (P = .029). Comparing the rate of > or =1 appropriate ICD therapy between the two groups by Kaplan-Meier analysis and the log rank test resulted in P = .027. CONCLUSION: In this retrospective analysis, biventricular pacing was associated with a decreased incidence of sustained ventricular arrhythmias requiring ICD therapy. The antiarrhythmic effect of biventricular pacing could contribute to the reduction in mortality reported in recent large-scale clinical trials on CRT. However, further prospective studies are warranted to clarify this issue.     

Initial clinical experience with cardiac resynchronization therapy utilizing a magnetic navigation system

Introduction: The placement of left ventricular (LV) leads during cardiac resynchronization therapy (CRT) involves many technical difficulties. These difficulties increase procedural times and decrease procedural success rates. Methods and Results: A total of 50 patients with severe cardiomyopathy (mean LV ejection fraction was 21 ± 6%) and a wide QRS underwent CRT implantation. Magnetic navigation (Stereotaxis, Inc.) was used to position a magnet‐tipped 0.014″ guidewire (Cronus? guidewire) within the coronary sinus (CS) vasculature. LV leads were placed in a lateral CS branch, either using a standard CS delivery sheath or using a “bare‐wire” approach without a CS delivery sheath. The mean total procedure time was 98.1 ± 29.1 minutes with a mean fluoroscopy time of 22.7 ± 15.1 minutes. The mean LV lead positioning time was 10.4 ± 7.6 minutes. The use of a delivery sheath was associated with longer procedure times 98 ± 32 minutes vs 80 ± 18 minutes (P = 0.029), fluoroscopy times 23 ± 15 minutes vs 13 ± 4 minutes (P = 0.0007) and LV lead positioning times 10 ± 6 minutes vs 4 ± 2 minutes (P = 0.015) when compared to a “bare‐wire” approach. When compared with 52 nonmagnetic‐assisted control CRT cases, magnetic navigation reduced total LV lead positioning times (10.4 ± 7.6 minutes vs 18.6 ± 18.9 minutes; P = 0.005). If more than one CS branch vessel was tested, magnetic navigation was associated with significantly shorter times for LV lead placement (16.2 ± 7.7 minutes vs 36.4 ± 23.4 minutes; P = 0.004). Conclusions: Magnetic navigation is a safe, feasible, and efficient tool for lateral LV lead placement during CRT. Magnetic navigation during CRT allows for control of the tip direction of the Cronus? 0.014″ guidewire using either a standard CS delivery sheath or “bare‐wire” approach. Although there are some important limitations to the 0.014″ Cronus? magnetic navigation can decrease LV lead placement times compared with nonmagnetic‐assisted control CRT cases, particularly if multiple CS branches are to be tested.     

Predictors of appropriate defibrillator therapy among patients with an implantable defibrillator that delivers cardiac resynchronization therapy

INTRODUCTION: The purpose of this study was to determine predictors of appropriate implantable defibrillator (ICD) therapy among patients with heart failure who are treated with a cardiac resynchronization therapy-defibrillator (CRT-D). METHODS AND RESULTS: Patients enrolled in the Ventak CHF/Contak CD study were treated with a CRT-D device and were required to have NYHA class II-IV CHF, QRS duration > or = 120 msec, and a class I or II indication for an ICD. The study database was retrospectively analyzed during the 6-month postimplant period to identify predictors of appropriate ICD therapy. Five hundred and one of the 581 patients enrolled in the trial had successful device implantation and were included in this analysis. Patients were mostly male (83%), 66 +/- 11 years old, and had coronary artery disease (69%), a mean left ventricular ejection fraction (EF) = 0.22 +/- 0.07, and NYHA class II (33%), III (58%), or IV (9%) CHF symptoms. During 6 months of follow-up, 73 of 501 (14%) patients received an appropriate ICD therapy. Two independent predictors of appropriate therapy were identified: a history of a spontaneous, sustained ventricular arrhythmia (HR = 2.05; 95% CI = 1.31-3.20; P = 0.002) and NYHA class IV CHF (HR = 1.81; 95% CI = 1.10-2.96; P = 0.019). When patients with NYHA class II were excluded from analysis, a history of a sustained ventricular arrhythmia and the presence of NYHA class IV CHF symptoms remained as independent predictors of appropriate ICD therapy. CONCLUSIONS: In a select population of advanced heart failure patients receiving a CRT-D, NYHA class IV CHF was a powerful independent predictor of appropriate ICD therapy. Approximately one-quarter of the patients with NYHA class IV CHF who received a CRT-D device received an appropriate ICD therapy within 3 months after implant. Additional studies are needed to confirm an association between class IV CHF symptoms and an increased frequency of ICD shocks.     

Interlead difference between T-peak to T-end intervals in resynchronization patients with an implantable cardioverter-defibrillator

Background

The effectiveness of cardiac resynchronization therapy (CRT) in preventing sudden cardiac death is controversial. Epicardial left ventricular pacing reverses the direction of activation of the left ventricular wall from the epicardium to the endocardium. We evaluated whether the interlead difference between T-peak to T-end (Tp-e) intervals determined by a 187-channel repolarization interval-difference mapping electrocardiograph (187-ch RIDM-ECG) is related to the occurrence of ventricular tachyarrhythmia requiring implantable cardioverter-defibrillator (ICD) therapy in heart failure patients receiving CRT with a defibrillator (CRT-D).

Methods and Results

Repolarization interval-difference mapping electrocardiograph (187-channel) was performed on 61 patients who received CRT-D. Twenty-one patients experienced appropriate ICD therapy. The interlead difference between corrected recovery time intervals was not significantly different between patients with and without appropriate ICD therapy (98 ± 24 milliseconds versus 88 ± 24 milliseconds). The interlead difference between corrected Tp-e intervals was significantly higher in patients with appropriate ICD therapy than in those without (88 ± 22 milliseconds versus 59 ± 23 milliseconds, P < .001).

Conclusion

The interlead difference between corrected Tp-e intervals determined by 187-ch RIDM-ECG may be related to appropriate ICD therapy in heart failure patients receiving CRT-D.     

Recent clinical experience with the automatic implantable cardioverter-defibrillator

The automatic implantable cardioverter-defibrillator is an electronic device designed to monitor the heart continuously, identify ventricular tachycardias and ventricular fibrillation, and terminate the life-threatening arrhythmias with an internal countershock. This device has been proved to be safe and effective, and its use has led to a significant decrease of arrhythmic mortality in the implantees.     

左室主动固定电极在心脏再同步治疗中的初步应用

目的初步探讨左室主动固定电极在心脏再同步治疗(CRT)中的应用价值。方法选取5例符合心脏再同步治疗适应证的心力衰竭(心衰)患者,在常规CRT植入技术基础上,左室电极选用美敦力主动固定电极Attain Star Fix4195,到位后伸展伞叶将其固定至目标血管位置,测试参数并检测有无膈肌刺激,随访观察有无膈肌刺激、脱位、阈值明显增高及心功能改善情况。结果 5例心衰患者全部手术成功。靶目标血管分别为心侧静脉2例,心后侧静脉1例,心中静脉2例。起搏阈值为(1.3±0.7)V,R波幅度(7.9±2.9)mV。术后1周超声心动图与术前比较:左室舒张末内径(LVDd)由(7.43±0.87)cm下降为(7.15±0.76)cm,左室射血分数(LVEF)由(28.8±2.8)%上升为(36.0±4.0)%,肺动脉压(PAPs)由(51.0±20.6)mm Hg下降为(24.6±2.6)mm Hg,二尖瓣反流均有不同程度减轻。术后6～16个月随访:NYHA分级4例患者由Ⅲ级下降为Ⅱ级,1例患者由Ⅳ级下降为Ⅲ级,均无脱位和膈肌刺激出现。结论 CRT采用左室主动固定电极安全性好,降低脱位和膈肌刺激风险,增加手术成功率。     

The future of implantable defibrillator and cardiac resynchronization therapy trials

Implantable cardioverter defibrillator (ICD) trials were initially limited to survivors of sudden death. The focus of defibrillator trials in the last decade has been in prophylactic implantation of the device in high risk populations for the prevention of sudden cardiac death. It is the contention in this review that the new focus for implantable defibrillator trials in 2008 and beyond will be on more selective and focused use of this therapy. This could be achieved by selecting ICD patients based on their pathophysiologic and genetic risk. Increasing effort will also be placed on using the device for prevention of spontaneous malignant ventricular tachyarrhythmias and the index clinical sudden death event. Finally, implantable defibrillators will be used in combination in a “hybrid” therapy approach. ICDs will be increasingly combined either with ventricular tachycardia ablation or ventricular fibrillation ablation using catheter techniques. With the addition of cardiac resynchronization therapy in these devices, new clinical trials that use cardiac resynchronization therapy as an early intervention in specific high risk heart failure populations and refinement of the CRT technique to improved optimal results are in progress. Finally, combining ICD devices and regenerative medicine approaches to myocardial replacement therapy are being explored. Dr. Saksena is a consultant and/or investigator for Medtronic Inc., St. Jude Medical Inc., Sanofi Aventis, and Aryx Pharmaceuticals.     

CRT plus ICD in congestive heart failure. Use of cardiac resynchronization therapy and an implantable cardioverter-defibrillator in heart failure patients with abnormal left ventricular dysfunction

Cardiac resynchronization therapy (CRT) significantly improves functional status, exercise duration, left ventricular (LV) ejection fraction, death from progressive congestive heart failure (CHF), and hospitalization for CHF in patients with moderate-to-severe CHF, an abnormal LV ejection fraction, and a QRS duration on the electrocardiogram of 120 msec or more. In these patients, CRT reduces all-cause mortality, though not significantly. However, CRT plus. an implantable cardioverter-defibrillator (ICD) significantly reduces all-cause mortality. Compared with placebo, ICD therapy significantly reduced all-cause mortality by 33% in patients with class II or III CHF, an abnormal LV ejection fraction, and a QRS duration on the electrocardiogram of 120 msec or more.     

Initial experience with cardiac resynchronization therapy for ventricular dysfunction in young patients with surgically operated congenital heart disease

Data regarding cardiac resynchronization therapy (CRT) in pediatric patients are limited. The first reported use of CRT in a young patient with congenital heart disease showed promising early results with improvement in New York Heart Association classification, aerobic capacity, and ventricular contractility 1 month after implant. Other reports have shown acute benefits of CRT in young patients with postoperative right bundle branch block after surgery for congenital heart defects. To date, however, there are no published data regarding CRT for the long-term management of systemic ventricular dysfunction in the young with associated congenital heart disease. This report describes our initial experience with CRT in these patients.     

Unresolved issues in implantable cardioverter-defibrillator therapy

Over the last 15 years, a series of well-designed randomized clinical trials has clearly demonstrated that implantable cardioverter-defibrillator (ICD) therapy reduces mortality in select high-risk populations. Despite the widespread acceptance of ICD therapy, many questions related to its optimal use remain. This article discusses several key issues now confronting clinicians.