How long can very elderly patients (100 years of age or older) with second-degree heart block live if they choose not to have a pacemaker? In these patients with heart rates of 28-36 beats per minute, why does the pulse pressure tend to be so high (>150 mm Hg)?
—Janet Hussong, RN, MSN, CPNP, Englewood, Ohio
It is impossible to accurately state how long someone will live regardless of his or her heart rate. Nonetheless, a bradycardic rate of 28-36 beats per minute can supply the blood-body distribution only to a certain extent. The pulse pressure is elevated because the body is trying to compensate for the slow heart rate through vasoconstriction, thereby increasing the blood flow distance per beat.
The two types of second-degree heart block are Mobitz type I (Wenckebach) and Mobitz type II, which is generally the more serious of the two. In Mobitz type I, the PR interval is gradually prolonged until a ventricular beat is skipped. With Mobitz type II, the electrical impulses do not reach the ventricles, resulting in a slowed ventricular heart rate. A permanent pacemaker would be indicated in Mobitz type II and in a patient who is symptomatic in Mobitz type I (if the patient consents).
—Debra Kleinschmidt, PhD, PA (117-13)