The case of the two-timing pacemaker.
A 71-year-old man with a permanent transvenous pacemaker had recent history of lightheadedness and was brought to the hospital emergency room complaining of shortness of breath. His blood pressure was 80/50, pulse rate 148. Administration of a pressor drug restored blood pressure and coincidentally the heart rate returned to 70. His condition was caused by formation of a dendritic spur in the substrate of the programming circuit in his implanted pacemaker, with consequent intermittent doubling of the impulse frequency. Another pacemaker was substituted surgically, and he recovered uneventfully.
D000368:Aged; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects*; D004562:Electrocardiography; D006339:Heart Rate; D006801:Humans; D008297:Male; D012804:Sick Sinus Syndrome / Q000628:therapy