Pacemaker alternans.
A 52-year-old man was implanted with a Gemini pacemaker for complete heart block which developed suddenly three months after coronary reconstruction and endocardial resection to treat chronic recurrent ventricular tachycardia. Pacemaker alternans, which is a rare phenomenon, occurred two days after pacemaker implantation and then disappeared 24 hours later. The patient was followed for a two-month period during which the pacemaker system functioned normally. Many of the possible mechanisms which may produce pacemaker alternans were explored. Our findings are presented in this report.