Inclusion Criteria:  Female patients diagnosed with HER2-positive breast cancer treated in our hospital. Surgical treatment combined with chemotherapy or radiotherapy was completed according to NCCN guidelines, and trastuzumab standard treatment was received for at least half a year.  (3) Cardiac function (including echocardiography or biomarkers) was assessed at least once within 3 months before trastuzumab treatment, and at least once during or after treatment was performed for heart-related tests.  (4) Complete case data.  Exclusion Criteria:  Patients who have not been properly treated with trastuzumab or have been treated for less than half a year; Patients who did not receive cardiac function assessment before trastuzumab treatment, during or after treatment; Patients whose case data were missing or lost to follow-up.