 Initial studies showed beneficial effect of the use of carvedilol for the prevention of chemotherapy-induced cardiomyopathy. This study has the objective to evaluate the effectiveness of carvedilol for the prevention of chemotherapy-induced cardiomyopathy. Will be selected 200 patients referred for chemotherapy that includes anthracyclines for breast cancer.These patients will be randomized to carvedilol or placebo and will have periodic assessment of cardiac function with echocardiography and biomarkers until complete chemotherapy and 24 months later. 