The objective of this paper is to propose a conceptual tool for consideration by medical professionals and cardiologists, based on the concept of prudential judgment or Aristotelian phronesis to confront the problems of cardiotoxicity resulting from cancer treatments. We start by analyzing the case of a young female patient who received two types of therapies: the first with anthracyclines (adriamycin), which produces type I damage, as stated in the consensus of 2014; and the second treatment, one month later, with trastuzumab, an agent that produces type II damage not dependent on dose. In this case, the patient manifested acute cardiac insufficiency, with a decrease of LVEF to 28% on the echocardiogram and to 27% on magnetic resonance imaging. Reports have indicated that treatment with beta blockers and the suspension or decrease of the dose limits damage, but during preclinical stages. Awareness and early attention to subclinical damage have thus become extremely relevant to substantiate treatments based not only on clinical evidence but also on the ability of medical professionals to rely on prudential judgment--which moves away from the medical practices that are developed on a daily basis in order to influence and reduce the cases of irreversible heart failure known as cardiotoxicity.