Cardiac Pacemakers

Abstract

The first artificial pacemaker was implanted in Stockholm, Sweden, in 1958, by Elmquist and Senning (1). Today, more than 1 million pacemakers have been implanted worldwide, mostly in older people (2). At least 90,000 of the approximately 115,000 pacemakers implanted in theUnited States in 2004 were implanted in people 60 or older. The median age for males who receive their first pacemaker today is approximately 75 and for females 78. The indications have widened and the number of pacemakers per million inhabitants in the United States who receive their first pacemaker each year increased from approximately 200 in 1985 to more than 400 in 1998 (3). Their impact on symptoms and mortality has been so overwhelming that no randomized trials have been necessary to prove their efficacy. The indications for pacemaker placement include specific electrocardiographic (ECG) abnormalities and symptoms. The latest American College of Cardiology/American Heart Association indications were published in 1998 (4). Roughly 90% are implanted for sinus node dysfunction or atrioventricular (AV) block. Patients with a normal electrical system, such as patients with carotid sinus hypersensitivity or hypertrophic cardiomyopathy, may occasionally be candidates. Dual-site atrial pacing has been used to prevent atrial fibrillation and biventricular pacing may be useful to synchronize contraction of the right and the left ventricles in patients with severe left ventricular dysfunction. This has made implantation of pacemakers technically more challenging and increased the likelihood of lead dislodgment and programming difficulties.