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Subcutaneous Implantable Cardioverter-Defibrillators

Evidence supporting the efficacy of implantable cardioverter-defibrillators (ICDs) in their ability to correct ventricular fibrillation (VF) is extensive and secure. , The conventional transvenous ICD (TV-ICD) has evolved considerably after being initially somewhat cumbersome and requiring surgical placement of epicardial patches. Abdominally placed generators with long, subcutaneously tracked but nonetheless transvenous leads followed. The major strategic technical advance was the simplified unipolar approach allowing devices to…

Transvenous Implantable Cardioverter-Defibrillator: Clinical Aspects

Implantable cardioverter-defibrillators (ICDs) provide important therapy for patients at high risk for ventricular fibrillation (VF) or life-threatening ventricular tachycardia (VT). This chapter complements Chapter 121 on technical aspects and Chapter 123 on the subcutaneous (S) ICD. Risk Stratification and Indications for Implantable Cardioverter-Defibrillator Therapy ICDs are the preferred treatment for secondary prevention of VT/VF when no reversible cause can be identified. Presently, however, more than 80%…

Implantable Cardioverter-Defibrillators: Technical Aspects

Implantable cardioverter-defibrillators (ICDs) have revolutionized the treatment of malignant ventricular arrhythmias. The basic functions include tachycardia detection and tachycardia termination. The ICD relies on a very complex series of steps, including sensing of myocardial potentials, delivering these signals to the ICD circuit board to be filtered and analyzed, and then delivering life-saving therapies back to the heart. This chapter outlines the technical aspects of these life-saving…

Implantable Pacemakers

The use and sophistication of permanent pacemakers have increased steadily since the first pacemaker was implanted in 1958. Indications for their use have broadened as the technology has advanced, and pacemakers have become a mainstay of therapy. Those involved in arrhythmia management must have a good understanding of this discipline. History of Pacing Since the first epicardial pacing system was implanted in 1958, pacemaker technology has…

Anticoagulation for Thromboembolic Prophylaxis

Indications for Anticoagulation in Atrial Fibrillation Anticoagulation is indicated for thromboembolic prophylaxis in patients with atrial fibrillation (AF) who meet established criteria. For a long time, warfarin was the sole drug for this indication. This agent was identified by Karl Link and colleagues in 1940 when they determined that coumarin or sweet clover could be metabolized by fungi into the anticoagulant dicoumaral. In 1950 Askey and…

Impact of Nontraditional Antiarrhythmic Drugs on Sudden Cardiac Death

Introduction Although mortality from coronary artery disease (CAD) has declined in the United States, sudden cardiac death (SCD; see Chapter 79 ) remains a major clinical problem, with a reported range of 184,000 to 462,000 deaths occurring annually. , Strategies to decrease the incidence of SCD include preventing underlying structural heart disease, screening for hereditary syndromes that predispose to SCD, improving efforts in resuscitation medicine for…

Antiarrhythmic Drugs

Mechanism-Based Approach to Treatment of Arrhythmias Elucidating the Underlying Pathophysiologic Mechanisms of Arrhythmias Antiarrhythmic drugs (AADs) remain an important therapeutic option for the treatment of acute and chronic atrial and ventricular arrhythmias despite recent advances in catheter ablation and surgical therapy. Nevertheless, the efficacy of ion channel–blocking drugs is limited, and many drugs are associated with serious toxicity, including QT interval prolongation and noncardiac toxicities. The…

Ventricular Arrhythmias in Congenital Heart Disease

Acknowledgments We thank Margot M. Bartelings for support and useful comments while preparing the anatomy and embryology part of the manuscript and for her help in making the morphologic photographs, and Ron Slagter for help in preparing the figures. The reported incidence of congenital heart disease (CHD) depends on the number of trivial lesions included. For moderate to severe CHD that will require specialized care, numbers…

Supraventricular Tachycardias in Congenital Heart Disease

Introduction The last 3 decades have seen major improvements in the preoperative, surgical, and longer-term management of children undergoing congenital cardiac surgery, resulting in an ever-expanding population of young adults with congenital heart disease (ACHD). A regional longitudinal analysis in Quebec demonstrated that between 2000 and 2010, the prevalence of all ACHD increased by 57%, and severe ACHD increased by 55%, compared with 11% and 19%,…

Arrhythmias in the Pediatric Population

Unique Aspects of Pediatric Electrophysiology Although the basic principles of cardiac electrophysiology (EP) apply broadly across the age spectrum, several distinctive characteristics of the pediatric population deserve emphasis. These begin at the cellular level, with differences in the action potential and calcium handling by immature myocytes, and extend up to the gross clinical level, with technical challenges during therapeutic interventions in small hearts. All aspects of…

Cancer Therapy–Related Arrhythmias

Introduction The field of hematology and oncology is one the fastest growing and ever-evolving fields in medicine. In the past decade, substantial improvements in the diagnosis, and more importantly, the treatment of various hematologic and oncologic malignances have led to remarkable improvements in both prognosis and overall survivability of the cancer population. In the landscape of improved survivorship, many will experience adverse effects of their life-saving…

Arrhythmia in Neurologic Disease

Electrophysiologists are routinely tasked with the management of arrhythmia in the setting of an underlying acute or chronic neurologic disturbance. The underlying neurologic diagnosis often carries important implications regarding the permanence, rate of progression, and prognosis of the arrhythmic manifestations. In this chapter we will review neurologic disorders that commonly present with arrhythmic manifestations. Neurologic Disorders With Transient Arrhythmia Manifestations Neurogenic Heart Disease Transient electrocardiographic (ECG)…

Ventricular Assist Devices and Cardiac Transplant Recipients

Acknowledgments This work was supported in part by an Agence Nationale de la Recherche (ANR) grant (10-IAHU04-LIRYC). F.D.R. was supported by a Canadian Institutes of Health Research (CIHR) Banting Postdoctoral Fellowship and a Royal College of Physicians and Surgeons of Canada Detweiler Traveling Fellowship. We thank Mr. Jean-Rodolphe Roux (Biosense-Webster) for his assistance with Fig. 111.2 . Brief Overview of Ventricular Assist Devices Heart failure (HF)…

Sleep-Disordered Breathing and Arrhythmias

Obstructive Sleep Apnea Pathophysiology OSA is characterized by the failure of neuromuscular mechanisms governing upper airway patency during sleep, resulting in airway narrowing or collapse. Although apnea can occur in any position, the upper airway is more vulnerable to obstruction in the supine position because of dorsal displacement of the tongue and soft tissues. Upper airway collapse can occur during any stage of sleep, but susceptibility…

Cardiac Sarcoidosis

Introduction Sarcoidosis is an inflammatory disease of unknown etiology, defined histologically with noncaseating granulomas and subsequent tissue scarring. Sarcoidosis most commonly involves the lungs but can be seen in virtually all organ systems, including eyes, skin, liver, lymph nodes, the neurologic system, and the gastrointestinal (GI) system. A minority of cases affect the heart; nevertheless, cardiac disease is an important cause of morbidity and mortality. Inflammation…

Sudden Cardiac Deaths in Athletes, Including Commotio Cordis

Introduction Sudden cardiac death (SCD) in athletes is unusual, but the emotional magnitude is great. Underlying cardiac disease is found in the majority of athletes who die young. Commotio cordis is a cause of SCD unrelated to underlying heart disease. Exercise, and especially extreme exercise, may potentially cause adverse cardiac remodeling, particularly in certain populations. Despite increases in electrocardiogram (ECG) screening, its efficacy in preventing SCD…

Sex Differences in Arrhythmias

Understanding and recognition of sex-based differences, with respect to both normal cardiac electrophysiology and the pathophysiology of arrhythmias, are important for the diagnosis and treatment of heart rhythm disorders in women. There are cellular and clinical electrophysiologic differences that have been identified between men and women. Although genetics and the sex hormones partially explain the morphologic differences in cardiovascular systems, there is limited understanding of the…

Atrioventricular Block

The atrioventricular (AV) node is the only connection between the atria and ventricles in the normal heart. It modulates the AV conduction to provide enough delay between atrial and ventricular conduction to allow for ventricular filling. In addition, its decremental conduction properties limit ventricular rates during atrial arrhythmias, such as atrial flutter (AFL) and atrial fibrillation (AF). The AV node also has the capability to serve…

Postural Orthostatic Tachycardia Syndrome

Since the mid-1980s, there has been a tremendous increase in our knowledge concerning illnesses that result from disturbances in the normal functioning of the autonomic nervous system (ANS). Initially, many of these investigations were principally focused on neurocardiogenic (or vasovagal) syncope, primarily as a consequence of the development of head-upright tilt-table testing as a method for uncovering a predisposition to the condition. During the course of…

Sinus Node Abnormalities

Introduction Although the sinus node has been recognized as the primary cardiac pacemaker for more than a century, our understanding of its complex anatomy, molecular construct, and pacemaking mechanisms remains incomplete. The cell biology of cardiac impulse initiation and propagation in regard to the sinus node are detailed in Chapter 28 . This chapter explores the anatomic and physiologic features of the sinus node, sinus node…