Strain vs. Left Ventricular Ejection Fraction-based Cardiotoxicity Prevention in Breast Cancer

Inclusion Criteria: * Female aged ≥ 18 years * Pathologically confirmed HER2-positive breast cancer * Adjuvant treatment plan comprises at least 12 cycles of Trastuzumab * Baseline echocardiogram should be performed before starting trastuzumab * Cumulative anthracycline dose ≤ 300mg/m2 * Written informed consent to participate in the study Exclusion Criteria: * History of hypersensitivity or alllergic reaction to the study medication * Metastatic breast cancer * Treatment with angiotensin converting enzyme(ACE) inhibitor , Angiotensin receptor blocker (ARB), beta-blocking agents, or diuretics * Patients with NCI/CTCAE grade ≥ 2 congestive heart failure, myocardial infarction, symptomatic left ventricular systolic dysfunction, heart's valve disease (≥ moderate), arrhythmias (Grade ≥ 3) \< 12 months before enrollment * Pregnancy or breast feeding * Baseline systolic pressure \< 90mmHg * Cumulative anthracycline dose \> 300mg/m2 * Serious concurrent illness