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Pacemaker therapy effectively treats bradycardia-related symptoms for patients with sinus node dysfunction, advanced atrioventricular (AV) block, and in some instances carotid sinus hypersensitivity.
Conduction disturbance after cardiac surgery is relatively common after coronary artery bypass grafting and valve surgery. Although the natural history of postoperative AV block is variable, the need for a permanent pacemaker (PPM) system is higher in those with preexisting electrocardiogram abnormalities, prolonged bypass time, and repeat procedures.
Bradycardia after cardiac transplantation is usually temporary and far less common with bicaval anastomoses.
In carefully selected heart failure patients, cardiac resynchronization therapy (CRT) has been shown to improve heart failure symptoms, quality of life, and reduce mortality.
Several randomized clinical trials have demonstrated reduced infectious complications following permanent device implantation with empiric periprocedural antibiotic administration.
When coronary sinus anatomy or pacing parameters prohibit transvenous lead placement for CRT, a number of techniques can be used to place epicardial leads. Robotic arm placement may reduce the amount of postoperative pain that patients experience.
Optimal PPM therapy requires selection of appropriate pacemaker type and pacing mode for each patient.
Pacemaker complications can be divided into those associated with the implantation procedure, subsequent infections, loss of lead integrity, and programming-related problems.
Indications for device extraction include systemic infection, arrhythmia or other complications related to retained fragments or leads, and the need for additional vascular access.
Implantable cardioverter-defibrillator therapy is indicated for patients with structural heart disease and life-threatening ventricular arrhythmias or risk factors for sudden death.
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Permanent pacemakers (PPMs) were introduced in the 1950s for use in patients with pathologic conditions of the sinus node, atrioventricular (AV) node, or His–Purkinje system. Since that time they have been refined to allow more complex programming. In addition, periprocedural morbidity has been reduced significantly. As a result, the number of devices implanted has increased steadily, with over 150,000 new pacemakers implanted in the United States each year.1
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Anatomy of the Conduction System
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The sinus node is an oval piece of tissue in the roof of the right atrium that is 10 to 20 mm long and 2 to 3 mm wide. It is less than 1 mm from the epicardial surface between the superior and inferior venae cavae.2,3 Its blood supply is derived from the right coronary artery (RCA) 55 to 60 percent of the time and from the circumflex coronary artery 40 to 45 percent of the time.2
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The atria are anatomically complex structures and differ significantly from each other. The right atrium is heavily trabeculated over the lateral wall and appendage and is characterized by significant heterogeneity, with abrupt changes in muscle fiber orientation over short distances. In contrast, the left atrium is a more uniform structure. Unlike ventricular myocardium, which contains Purkinje fibers, it now is generally accepted that the atria do not contain specialized conduction ...