Indications for implantation of a permanent pacemaker in the elderly are generally based on symptoms, the presence of heart disease and the presence of symptomatic bradyarrhythmias. Pacemakers for tachyarrhythmias, cardioversion and defibrillation are also available. Gregoratos reviews current indications for pacemaker use and advances in technology.
Patients more than 70 years of age account for greater than 70 percent of pacemakers implanted, in part. This is due to the physiologic changes that occur with aging, in which the heart's conduction system becomes disordered. Specifically, there is a reduction in P cells and an increase in collagen in the sinoatrial node. The number of conduction cells in the bundle of His and in the bundle branches also decrease. Hemodynamic compromise is more common in the elderly when these physiologic changes cause arrhythmias. The American College of Cardiology/American Heart Association recently issued practice guidelines outlining the indications for permanent pacing (see the accompanying table on guidelines). One of the main tenets is that symptoms need to be correlated with the arrhythmia before pacing is initiated. Many types of pacemakers are available, generally categorized by a three- to five-letter code according to the site of the pacing electrode and the mode of pacing. For a listing of generic pacemaker codes, see the accompanying table on codes.
First-degree atrioventricular (AV) block, thought to be a relatively benign arrhythmia, can be associated with severe symptoms that may benefit from permanent pacing. Specifically, some uncontrolled trials have shown a benefit from pacing in patients with a PR interval greater than 0.3 seconds. Type I second-degree AV block does not usually require permanent pacing because progression to a higher degree AV block is not common. Permanent pacing is known to improve survival in patients with complete heart block, especially if they have had syncope.
Permanent pacing is not needed in a number of conditions, even in patients with advanced AV block. Reversible causes of AV block, such as electrolyte disturbances or Lyme disease, simply require treatment of the underlying cause. In other situations, AV block occurs only sporadically, as with sarcoidosis, but should be treated with pacing because of the known history of disease progression. Implantation is typically easier and of lower cost with single-chamber ventricular demand (VVI) pacemakers, but use of these devices is becoming less common with the advent of dual-chamber demand (DDD) pacemakers. Symptoms of AV block generally resolve after insertion of a DDD pacemaker, although the prognosis is poorer in patients with severe left ventricular dysfunction and coronary heart disease.
Sick sinus syndrome (or sinus node dysfunction) is the most common reason for permanent pacing. For an algorithm describing selection of pacemaker type in these patients, see the accompanying figure. Symptoms are related to the bradyarrhythmias of sick sinus syndrome, and they direct the decision to initiate permanent pacing. VVI mode is typically used in patients with sick sinus syndrome, but recent studies have shown that DDD pacing improves morbidity, mortality and quality of life. Some newer pacemakers allow automatic switching from DDD to VVI, so that episodes of atrial tachycardia are not tracked by the ventricles.
The author concludes that careful assessment of symptoms, analysis of the arrhythmia and selection of appropriate pacemaker type may lead to improved outcomes in some elderly patients.