Skin biopsies could reveal why breast cancer drugs harm the heart

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Female * Age greater than 18 years * Willing to participate in protocol procedures with signed informed consent * Assessment of LVEE via echocardiogram, cardiac MRI, or MUGA Subjects in the cardiotoxicity group (TOX) must meet the following criteria: * History of HER2 positive breast cancer (stage I-IV) * Prior/current treatment with anthracycline based chemotherapy followed by anti-HER2 directed therapy or anti-HER2 directed therapy alone * Assessment of LVEF at baseline prior to initiation of anthracycline or anti-HER2 therapy and during anti-HER2 therapy via echocardiogram, cardiac MRI, or MUGA * Prior confirmed diagnosis of cardiotoxicity associated with anti-HER2 based therapy, defined as a decrease in LVEF \> 10% from baseline to \< 53% with symptoms of heart failure (NYHA class II-IV). Subjects in the no cardiotoxicity group (NO-TOX) must meet the following criteria: * History of HER2 positive breast cancer (stage I-IV) * Completion of planned anthracycline and anti-HER2 therapy, or anti-HER2 therapy alone * No symptoms of heart failure (NYHA class II-IV) during and at the end of anthracycline and anti-HER2 therapy * Assessment of LVEF at baseline prior to innitiation of anthracycline or anti-HER2 therapy and during anti-HER2 therapy via echocardiogram, cardiac MRI, or MUGA * Normal LVEF \>53% at each assessment during and at the end of trastuzumab therapy. * Maximum absolute decrease in LVEF \<5% from baseline during and at the end of trastuzumab therapy. * LVEF assessment performed at baseline and at least two time points during trastuzumab therapy. Exclusion Criteria: * Unwilling or unable to give skin biopsies * Contraindications to punch biopsy including but not limited to bleeding diathesis, as determined by the investigator. * Known pre-existing CV disease prior to initiation of breast cancer therapy as determined by the investigator, including * Obstructive coronary artery disease (stenosis \>70%) * Arrhythmia - paroxysmal or persistent atrial arrhythmias, sustained ventricular tachycardia (\>30 seconds), ventricular fibrillation, or cardiac arrest * Cardiomyopathy (EF \<53%) * Heart failure (NYHA class II-IV) * Valvular heart disease with equal to or greater than moderate stenosis or regurgitation