What symptom might indicate a decline in heart function for patients on trastuzumab and pertuzumab?

Shortness of breath is a significant symptom that may indicate a decline in heart function for patients receiving trastuzumab and pertuzumab, which are used in the treatment of HER2-positive breast cancer. These medications can have cardiotoxic effects, leading to heart dysfunction, particularly left ventricular dysfunction.

When the heart's ability to pump blood effectively declines, patients often experience symptoms such as dyspnea or shortness of breath, especially with exertion or when lying flat. This occurs because the body is not receiving adequate oxygenated blood, leading to pulmonary congestion and other related issues. Monitoring for this symptom is crucial as it can prompt further evaluation of the heart function through echocardiograms or other diagnostic tests, allowing for timely intervention if heart failure or cardiomyopathy develops.

High blood pressure, orthostatic hypotension, and weight gain may be associated with cardiovascular issues or side effects from therapy, but they are not as directly indicative of declining heart function in this context as shortness of breath.