Electrocardiographic and pathological studies of the heart in experimental guinea pig leukemia

Electrocardiographic tracings were performed on 26 strain 2 guinea pigs in which leukemia was induced by inoculation of L2C leukemic cells. All inoculated animals developed leukemia. In terminal phases of this disease significant electrocardiographic changes were observed in 20 of the 26 animals; in 5 animals the electrocardiograms were normal and in 1 guinea pig the changes were borderline. The most significant changes consisted of the onset of a Q-wave or a T-wave inversion or both. Pathological examination of the heart removed in the terminal phase of the disease revealed infiltration of the endocardium and epicardium and in the capillaries of the myocardium. Such areas of infiltration, when viewed with the electron microscope, revealed the presence of leukemic cells within the lumen of capillaries and in areas immediately surrounding the capillaries. Infiltration of myocardial fibers was not observed. The electrocardiographic changes observed in guinea pig leukemia may be related to the leukemic infiltration of myocardial capillaries and the resulting anoxia.