Changes of the intramyocardial electrogram after orthotopic heart transplantation.

Heart transplantation, including conventional immunosuppression, has allowed the use of the surface electrocardiogram to detect allograft rejection. With the use of cyclosporine this parameter is no longer sensitive, but voltage of the intramyocardial electrogram has correlated repeatedly with rejection. From July 1983 through February 1986, 98 patients had heart transplantation; 13 of those patients had a telemetry pacemaker simultaneously implanted. In previous studies, daytime dependent variabilities of the sum voltage of the surface electrocardiogram were reported. Therefore intramyocardial electrogram was measured at 7, 10, 13, 16, and 20 hours. In addition, the influence of exercise on intramyocardial electrogram voltage was studied in all patients. Analysis of the diurnal intramyocardial electrogram revealed substantial atrial and ventricular variability of both voltage measurements (p less than 0.05). Also, intramyocardial electrogram voltage was influenced by exercise, as demonstrated by a significant decrease after physical work at 25 W (-8%) and 50 W (-12%); p less than 0.05. Therefore we conclude that a high variability of intramyocardial electrogram may be found diurnally and on exercise testing after heart transplantation in humans. If intramyocardial electrogram is used to detect rejection, it should be applied at comparable hours and with the patients in a controlled resting state.