Evaluation of cardiac function by echocardiography in dogs treated with doxorubicin

Cardiac functions were evaluated by echocardiography in dogs treated with doxorubicin. The dogs were administered 1.5 mg/kg body-weight doxorubicin intravenously at intervals of 3 weeks. Two-dimensional echocardiography of several sections of the heart was taken and fractional shortenings of chordal and papillary muscle levels were measured from M-mode echocardiogram to assess the left ventricular contractile function. And color Doppler and pulse Doppler examinations of mitral flow velocity were performed. Concomitantly, electrocardiogram (ECG) was also examined. The animals with decreased cardiac function were euthanized and the hearts were examined histologically. Fractional shortening was reduced gradually in the dogs treated with doxorubicin. And mitral regurgitation during systolic phase and changes of mitral flow velocity during diastolic phase were also revealed in the dogs with severe reduction of fractional shortening. These changes might indicate the reduction of cardiac functions, both of contractility and diastolic filling functions. ECG abnormalities, which were small changes, revealed only in the dogs that had severe reduction of fractional shortening and mitral regurgitation. In histological examination, myocardial degeneration was observed. And, the degree of myocardial damage might be relative to alteration of fractional shortening. Thus, the result demonstrates that the early alteration of cardiac function induced with doxorubicin can be detected by echocardiography in dogs. The result also indicates that cardiac function predicted by fractional shortening measured from M-mode echocardiogram might be correlated with histological changes of myocardium.