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The recommendation and subsequent implantation of a pacemaker constitutes a therapeutic prescription with the same long-term responsibility for the periodic assessment of the continued appropriateness of that therapy as with the prescription of any pharmacologic agent. The multiplicity of programmable options available in the modern pacemaker allows the physician to titrate the dose of pacing in a manner similar to the periodic adjustment of the dose of a medication. A prime example is renal failure which commonly requires a decrease in the dose of some medications necessitated by a reduction in renal clearance, this same condition may require an increase in the programmed output of the pacemaker if the patient is prone to hyperkalemia because of associated rises in the capture threshold. This chapter will review multiple aspects and techniques associated with the routine follow-up of the pacing system including biventricular systems. [ABSTRACT FROM AUTHOR]

Cardiac pacing can play an integral role in the management of critically ill patients. This role is not limited to the appropriate implementation of temporary cardiac pacing, but also includes maximizing therapies already available through a patient's previously implanted permanent pacemaker or implantable cardioverter-defibrillator (ICD). Complications related to the implanted device can also lead to a need for management within the critical care setting. Finally, a permanent cardiac device can interact, and at times interfere, with therapies such as intravenous monitoring line placement, and external cardioversion and defibrillation. [ABSTRACT FROM AUTHOR]

Since the initial development of the implantable defibrillator in the 1970s by Michel Mirowski, and commercial introduction in 1985, national surveys and industry analysts have estimated that more than 160,000 implants have been performed in the United States (1). Multicenter randomized trials have demonstrated the effectiveness of the implantable cardioverter-defibrillator (ICD) for reducing mortality in high-risk patient groups (2,3). It has been estimated that more than 700,000 patients are eligible for an ICD in the United States. The newest generation of ICDs are capable of defibrillation of ventricular fibrillation, pace termination of ventricular tachycardia, single or dual chamber pacing, and cardiac resynchronization therapy (CRT) depending on the model. In addition, ICDs now have multiple additional features including extensive programming options, detailed event histories, and real-time telemetry. [ABSTRACT FROM AUTHOR]

Radiographic evaluation is often helpful after placement of pacemakers, implantable cardioverter-defibrillators (ICDs), and devices for cardiac resynchronization therapy (CRT). Important information may be missed if the chest radiograph is reviewed in a cursory fashion for adequacy of lead placement and for a pneumothorax following venous puncture for lead placement. Radiographic inspection of an implantable cardiac device system, whether pacemaker, ICD, or CRT device, should be performed in an organized manner (Table 18.1). Without an orderly approach, essential information may be overlooked. Posteroanterior (PA) and lateral chest radiographs from any patient with a permanent pacemaker or ICD should be obtained and reviewed by the implanting physician or follow-up team. Oblique views do not commonly provide a great deal of additional data for most pacemakers and ICDs but may be helpful for better assessment of left ventricular lead placement in some patients with CRT devices. [ABSTRACT FROM AUTHOR]

Early artificial pacemakers delivered asynchronous pulses at a fixed rate regardless of the intrinsic activity of the heart. As pacemaker technology improved, devices were developed that not only delivered pacing stimuli but also sensed intrinsic cardiac electrical activity. However, the circuitry used to detect small amplitude (1-20 mV) intracardiac electrical signals generated by the atrium and ventricle can also detect signals generated from both internal and external sources (1-3). Internal sources of signals include extracardiac muscle depolarization and other implanted devices such as ICDs and spinal cord stimulators. External sources of signals can arise from a variety of sources and are collectively referred to as electromagnetic interference (EMI). [ABSTRACT FROM AUTHOR]

It is ironic that the first transistorized, wearable pacemaker was designed by Earl Bakken specifically to make open heart surgery in children possible (1). Despite their pediatric origins, however, current heart rhythm control devices and leads are not designed or manufactured for children. Instead, they are designed with adults in mind, with respect to device size and lead length, as well as to the indications that prompt pacemaker implantation in adults. For this reason, the clinician who implants pacemakers in children and who follows such children must adapt the technology to the unique requirements of children. These requirements include the need for small size, but they also include flexibility in programmability, to take into account potentially higher levels of activity, higher natural heart rates, and the wide spectrum of problems encountered with congenital heart disease. [ABSTRACT FROM AUTHOR]

Sudden death caused by cardiac arrest due to ventricular tachycardia or ventricular fibrillation remains a serious health problem worldwide. In the United States alone, cardiovascular disease accounts for over 900,000 deaths annually (1). Of these deaths, 350,000 are due to out-of-hospital cardiac arrest (2), two-thirds of which occur without prior recognition of cardiac disease (1). In the United States, 15-20% of all fatalities and 50% of all cardiac fatalities are sudden. Although sudden death caused by asystole or pulseless electrical activity is not preventable, sudden death caused by a ventricular arrhythmia can be. Prompt treatment to stop the ventricular arrhythmia before it causes death is possible. [ABSTRACT FROM AUTHOR]

Syncope is the abrupt and transient loss of consciousness due to a temporary reduction in cerebral blood flow. It is associated with an absence of postural tone and followed by a rapid and usually complete recovery. Syncope may be both benign or the only warning before an episode causing sudden death (1). Recurrent episodes of syncope may result from a variety of disorders, all of which cause a temporary reduction in cerebral blood flow sufficient to disturb the normal functions of the brain. Neurocardiogenic (vasovagal) syncope is the most common of a group of reflex (neurally mediated) syncopes, characterized by a sudden failure of the autonomic nervous system (ANS) to maintain blood pressure, and occasionally heart rate, at a level sufficient to maintain cerebral perfusion and consciousness (2-4). Syncope accounts for 3.5% of all emergency room visits and 1-6% of all hospital admissions annually in the USA (5). [ABSTRACT FROM AUTHOR]

Atrial fibrillation (AF) occurs frequently in the pacemaker population particularly in those with sinus node dysfunction as the primary indication for cardiac pacing (1-3). Clinical trials have demonstrated that atrial pacing prevents paroxysmal and persistent AF in the general pacemaker population and the greatest benefit is observed in patients with sinus node disease (1-4). Many dual chamber pacemakers now have specific algorithms designed to suppress AF (4,5). In addition, there has been considerable interest in selective atrial pacing sites and prevention of AF (4,5). [ABSTRACT FROM AUTHOR]

Over the past 20 years there have been many groundbreaking advances in the pharmacologic treatment of congestive heart failure. However, there are still many end-stage patients, who despite optimal medical management, still have severe and refractory symptoms, along with an overall poor prognosis (1,2). Cardiac resynchronization therapy (CRT), which is also known as biventricular pacing has been shown to be an effective nonpharmacologic approach that can help many of these patients with advanced heart failure. Since the early pilot studies of CRT in the mid 1990s there has been extensive research in this area. Now we have several published large scale randomized controlled trials that prove CRT not only improves symptoms, but also decreases mortality. Based on these trials, CRT has become the standard of care for selected patients with moderate to severe heart failure. [ABSTRACT FROM AUTHOR]

There are many causes of atrioventricular (AV) block but progressive idiopathic fibrosis of the conduction system related to an aging process of the cardiac skeleton is the most common cause of chronic acquired AV block. Barring congenital AV block, Lyme disease is the most common cause of reversible third-degree AV block in young individuals and it is usually AV nodal. Before implantation of a permanent pacemaker, reversible causes of AV block such as Lyme disease, hypervagotonia, athletic heart, sleep apnea, ischemia, and drug, metabolic, or electrolytic imbalance must be excluded. Table 10.1 outlines the format used in the 2002 American College of Cardiology/American Heart Association/North American Society of Pacing and Electrophysiology (ACC/AHA/NASPE) guidelines for pacemaker implantation (1). The indications for permanent pacing in second- or third- degree AV block unlikely to regress are often straightforward in symptomatic patients but they are more difficult in asymptomatic patients. [ABSTRACT FROM AUTHOR]

Sinus node dysfunction was initially described in the early 1900s, and is the primary indication for pacemaker implantation in industrialized countries. The only effective treatment for symptomatic sinus node dysfunction is cardiac pacing. However, despite the widespread use of pacing therapy for this group of patients, the optimal pacing mode, pacing system and site of ventricular stimulation for sinus node dysfunction remains controversial. The available data for the diagnosis and treatment of sinus node dysfunction are reviewed in this chapter. [ABSTRACT FROM AUTHOR]

The development of the implantable cardioverter-defibrillator (ICD) is primarily the result of pioneering work by Michel Mirowski. First-generation devices consisted of a large generator placed in an abdominal pocket capable only of high-energy shocks. In the 25 years since the first implantation in humans (1), advances in technology have resulted in significantly smaller devices, with sophisticated detection algorithms and tiered therapies. Despite these advances, the primary goal of the ICD continues to be the rapid and effective treatment of ventricular arrhythmias. [ABSTRACT FROM AUTHOR]

Temporary pacing of the heart was first accomplished by Hyman in the early 1930s by a transthoracic approach using a clockwork-driven generator. In the early 1950s Zoll successfully resuscitated an asystolic patient using temporary transcutaneous pacing. Later in that decade, the feasibility of transvenous pacing and transesophageal pacing was demonstrated. Temporary pacing has become the standard method for providing immediate treatment of severe bradycardias and certain tachycardias for the past 20 years. [ABSTRACT FROM AUTHOR]

There is an ever-increasing need to manage complications in this era of implantable antiarrhythmic devices. Infections, sepsis, and the threat of mechanical trauma can necessitate partial or complete removal of an antiarrhythmic system, including device and leads. Such removal comes with the potential risk of significant morbidity and even mortality. The management of device complications has become a subspecialty of cardiology and cardiovascular surgery (1-5). It requires special training to acquire the skills for successful results. [ABSTRACT FROM AUTHOR]

With the publications of the Miracle (1), Miracle ICD (2), COMPANION (3) and CARE-HF (4) trials, biventricular pacing is now an undisputed adjunctive therapy for heart failure, demonstrating an additive symptom and survival benefit over pharmacological therapies alone. Its wider application has been hampered, in part, by the technical challenges of left ventricular lead implantation encountered by the operating physician. (Table 5.1) Inroads to successful LV lead implantation have been achieved through collective sharing of implant experiences (5). New sheath delivery systems, catheters, and guide wires continue to improve LV lead implantation success. It is hoped that this chapter will serve as a useful springboard to improving outcomes with LV lead implantation. [ABSTRACT FROM AUTHOR]

The implantation of devices for the management of both bradyarrhythmias and tachyarrhythmias has come together from divergent clinical pathways. There has, however, been an interesting parallel in the development of their methods of implantation (1). This has largely been driven by the dramatic advances in technology. In 1958, Seymour Furman and J.B. Schwedel passed the first transvenous endocardial electrode for prolonged cardiac pacing (2). Almost simultaneously, Rune Elmqvist and A.K.E. Senning developed a totally implantable pacemaker system with an epigastric pocket and the electrodes connected subcutaneously to the heart (3). These two events simultaneously introduced both the transvenous and epicardial approaches to cardiac pacing. [ABSTRACT FROM AUTHOR]

The method of classifying pacemaker function originated in 1987 as the NASPE/BPEG (North American Society of Pacing and Electrophysiology/ British Pacing and Electrophysiology Group). The classification has subsequently been modified to incorporate rate modulated pacing and multisite pacing (Table 3.1). The first position of the code indicates the cardiac chamber paced, which may include the atrium (A), ventricle (V), both the atrium and ventricle (dual or D), or none (O). The second position represents the cardiac chamber sensed, which may include the atrium (A), ventricle (V), both the atrium and ventricle (dual or D), or none (O). Manufacturers may also designate S for a single chamber that is sensed, or paced, either the atrium or the ventricle. The third position represents the function that the pacemaker performs: triggered (T), inhibited (I), triggered and inhibited (dual or D), or none (O). Triggered refers to pacing in the chamber paced after the sensing of intrinsic activity in the chamber sensed. The sensing and pacing may occur in different chambers. [ABSTRACT FROM AUTHOR]

A cardiac pulse generator is a device having a power source and electronic circuitry that produce output stimuli. Functionally, at its simplest, current sourced by the device's battery travels through a connecting pathway to stimulate the heart and then flows back into the pacemaker to complete the circuit. [ABSTRACT FROM AUTHOR]

The cardiac pacemaker lead is a relatively fragile cable of insulated conductor wire implanted into the hostile environment of the human body. Its function is to interface the power source and sophisticated electronics of the pulse generator with the heart. The pacemaker lead plays a critical role in delivering both the output pulse from the pulse generator to the myocardium and the intracardiac electrogram from the myocardium to the sensing circuit of the pulse generator. [ABSTRACT FROM AUTHOR]