Sudden cardiac death and implantable cardioverter-defibrillators

Veterans Affairs Palo Alto Health Care System, CA 94304-5588 , USA.
American family physician (Impact Factor: 2.18). 12/2010; 82(11):1357-66.
Source: PubMed


Sudden cardiac death is a major public health problem, affecting 500,000 patients in the United States annually. An implantable cardioverter-defibrillator (ICD) can terminate malignant ventricular arrhythmias and has been shown to improve survival in high-risk populations. Although sudden cardiac death is a heterogeneous condition, left ventricular ejection fraction of 35 percent or less remains the single best factor to stratify patients for prophylactic ICD implantation, and randomized trials have shown mortality benefit in this population. Therefore, in patients with heart disease, assessment of ejection fraction remains the most important step to identify patients at risk of sudden cardiac death who would benefit from ICD implantation. Physician understanding of each patient's ICD type, indication, etiology of heart disease, and cardiovascular status is essential for optimal care. If the ICD was placed for secondary prevention, the circumstances relating to the index event should be explored. Evaluation of defibrillator shocks merits careful assessment of the patient's cardiovascular status. Consultation with a subspecialist and interrogation of the ICD can determine if shocks were appropriate or inappropriate and can facilitate management.

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    • "Despite dramatic improvements of medical technology in the past several decades, implantable cardioverterdefibrillator , catheter ablation and antiarrhythmic drug therapy are not yet reliable for preventing sudden cardiac death and may be a disappointment following the sobering results of clinical trials[1]. Therefore, cardiovascular disease remains the most important cause of sudden death in the world [1]. The majority of such cardiac sudden deaths are caused by ventricular arrhythmias, which were often triggered by abnormal excitations at the single cell level, such as early afterdepolarizations (EADs) [2]. "
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    ABSTRACT: Aim: Early afterdepolarizations (EADs) are classically generated at slow heart rates and suppressed by fast intrinsic heart rates. However, experimental studies suggest EADs may also occur at rapid heart rates as a consequence of tachyarrhythmias. The aim of this study was to investigate the interaction between EAD and rapid reentrant excitation waves and assess its effects with electrocardiogram (ECG). Methods: A 3D human ventricular conduction model was developed by integrating Purkinje fiber network system and anatomically detailed ventricular geometry of the human heart with detailed electrophysiology in the format of mono-domain model. For simulating EADs, both ICaL and IKr equations of the ten Tusscher and Panfilov (TP06) model were modified based on experimental conditions. The standard S1-S2 stimulation protocol was implemented to induce reentrant excitation waves. ECGs were computed from a site 2cm distance from the epi-cardiac surface of the heart. Results: At the cellular level, reduced repolarization reserve by IKr contributed to action potential duration (APD) prolongation (ENDO: 302ms vs. 402ms, MIDDLE: 414ms vs.>1000ms, EPI: 298ms vs. 397ms) and genesis of EADs only in MIDDLE cells. In the 3D model, EADs caused drift of rapid rotors. Multiple focal excitations arising from EADs kept regeneration of reentrant excitation waves by breaking excitation wave fronts. ECGs presented periodic features with stable reentry in control condition, but degenerated into irregular and complex features in EADs condition. These observations were characteristic of the differences between ventricular tachycardia and ventricular fibrillation, which are in good agreement with clinical reports. Conclusion: The MIDDLE cells are prone to genesis of EADs at rapid heart rates, which play an important role in degenerating ventricular tachycardia into ventricular fibrillation.
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    ABSTRACT: The use of implantable cardioverter-defibrillators (ICDs) in pediatric patients has increased substantially over the past 3 decades. We report the case of a 15-year-old boy with congenital heart disease who presented with recurrent inappropriate ICD shocks due to a lead malfunction. Inaccessibility of a magnet to inactivate shock therapy in the pediatric emergency department (PED) resulted in numerous additional inappropriate shocks. Herein, we provide a brief overview of ICD care relevant to the PED. The complexities of these devices and their associated therapies require pediatric emergency physicians caring for these patients to recognize basic ICD functions and troubleshoot malfunctions to provide timely management. In particular, it is essential that PEDs be equipped with magnets and that physicians are trained in their appropriate use.
    Pediatric emergency care 06/2012; 28(6):562-5. DOI:10.1097/PEC.0b013e318258be04 · 1.05 Impact Factor