Myocyte apoptosis/necrosis is rare, and myocyte dysfunction is thought to be due to blockade of cardioprotective HER2 signalling and increased oxidative stress.19 20 The European Society of Cardiology (ESC) 2022 cardio-oncology guidelines recommend HER2-targeted therapies should be reviewed (with consideration to interrupting) for LVEF declines of >10% from baseline to <50%, with prompt initiation of heart failure treatments (HFTs), consisting of an ACE inhibitor (ACEi)/angiotensin receptor blocker (ARB) and/or a beta-blocker.21 Here, ERBB2 is linked to heart failure.