Echocardiographic changes in dogs undergoing chemotherapy protocols with doxorubicin

Background Doxorubicin is a widely used drug in veterinary oncology protocols due to its antineoplastic efficacy and cost-effectiveness. However, its cardiotoxic effects are not well documented, necessitating the development of strategies for its safe use. Objectives This study aimed to assess whether echocardiography can effectively detect and quantify the cardiotoxic effects of doxorubicin, alone or in combination with other chemotherapeutics. Animals This study monitored 33 dogs undergoing different chemotherapy protocols at the Veterinary Hospital of the Federal University of Uberlândia and its affiliated clinics using echocardiography. Methods In this prospective study, examinations were performed at three time points (T0 - before chemotherapy and after each application - to T3) to measure ejection fraction (Teicholz and Simpson methods), fractional shortening (FS), and left ventricular dimensions in diastole and systole. A linear mixed-effects model was used for statistical analysis, considering time, doxorubicin use, the presence of preexisting heart disease, and their interactions. Results Statistically significant reductions in echocardiographic parameters were observed in dogs treated with doxorubicin, either alone or in combination with other chemotherapeutics. These reductions remained within the physiological reference ranges of the species, with no clinical evidence of cardiac dysfunction. Chronic myxomatous degeneration of the mitral valve intensified the cardiotoxic response, as indicated by the estimated marginal means, suggesting the need for close monitoring in such cases. Age also influenced the magnitude of the changes, with adult dogs showing greater susceptibility than older dogs. These findings suggest a cumulative cardiotoxic pattern associated with doxorubicin, which can be detected early through serial echocardiographic monitoring, even when values remain within reference limits. Conclusion and Clinical Importance It was concluded that doxorubicin is safe when used under rigorous cardiovascular monitoring, and routine echocardiographic surveillance is recommended throughout treatment, even in the absence of overt clinical signs of cardiopathy.