The purpose of this study is to evaluate whether is it safe and effective to continue trastuzumab, pertuzumab, or trastuzumab-emtansine (T-DM1) in patients with early stage HER-2 positive breast cancer who develop mild, minimally symptomatic or asymptomatic systolic left ventricular dysfunction. There will be up to 20 participants enrolled at 腦瞳憫 with a total of 130 at all sites.