These studies seek an alternative method with myocardial biopsy for rejection diagnosis. A pacemaker (Biotronik model Logos) was implanted into 16 patients to detect intramyocardial voltage. The recordings were classified in two groups according to results of myocardial biopsy. The results of the biopsy were classified according to the recommendations of the International Society for Heart and Lung Transplantation: namely, Group I: rejection < 2 (52 recordings) and Group II: rejection > or = 2 (9 recordings). The sensitive parameter for rejection detection was Tslew, which was deduced from the paced intracardial potential in the monopolar mode. The results were significant in both groups; the medium value of Tslew in group I was 96.7%, and the value for group II was 87.13% (P=.022). The sensitivity value in our patient group for detection of treatedable rejection was 78%; the negative predictive value was 95%. In conclusion the method is useful for rejection detection, but is necessary to make several recordings for the same patients during the first month post transplant, to obtain an individual baseline value.