Electrocardiographic monitoring of cardiac transplants in mice

In the murine cardiac model for vascularised transplantation graft function may be monitored by direct palpation, electrocardiography, and graft histology. To assess the merits of these methods, and to measure ischaemic damage, isografts and allografts were examined at regular intervals from 0 to 60 days after grafting. Heart transplants were vascularised from the abdominal great vessels, using microsurgical techniques, with ischaemic times of less than 60 min. Isografts showed no decrease in heart rate over 60 days, as measured by palpation and electrocardiography, but the voltage of the ventricular complex fell progressively over the first 28 days after grafting then remained stable for more than 60 days. The voltage drop was associated with atrophy of myocardial tissue. Allografts in recipients treated with rabbit antimouse antilymphocyte serum were maintained for more than 60 days with little change in palpation rate or recorded heart rate but with significant falls in ventricular complex voltage, reflecting myocardial atrophy and fibrosis. Untreated allografts were rejected in 10-14 days and showed a rapid fall in palpated heart rate, measured heart rate, and ventricular complex voltage. Thus, in this study, palpation of the heart graft gave an accurate measure of the pulse rate and correlated with electrical activity in acutely rejecting grafts, but in long surviving grafts measurement of ventricular complex voltage showed myocardial damage that was not detectable by direct palpation.