Aim of this monocentric prospective longitudinal study is to explore left atrial longitudinal strain imaging trend over time in relation to conventional echocardiographic parameters of LV dysfunction in patients affected by HER2 positive breast cancer; moreover, to investigate the eventual relationship between early changes in left atrial function and the development of Trastuzumab-induced cardiotoxicity. This evidence concerns the gene ERBB2 and breast carcinoma.