A cycle of complications: a case report on trastuzumab-induced takotsubo cardiomyopathy causing left ventricular thrombosis complicated by thromboembolic stroke.

Background: Left ventricular thrombus (LVT) formation is an uncommon phenomenon, typically observed in acute cardiac settings and hypercoagulable states. Takotsubo cardiomyopathy (TC) is a reversible condition originally thought to be linked to immense emotional stress. The occurrence of chemotherapy-related cardiotoxicity presenting with TC and LVT formation is a relatively new concept that remains not fully understood. Case summary: We present the case of a 77-year-old woman with Stage IV breast cancer being treated with trastuzumab and capecitabine therapy, who presented to our hospital with symptoms of right-sided weakness, facial droop, and slurred speech. She was admitted for acute left frontal lobe infarction due to an occluded distal left posterior M2 branch of the left middle cerebral artery. As part of thromboembolic stroke work-up, transthoracic echocardiogram (TTE) was obtained, which showed moderately to severely decreased left ventricular systolic function (LVEF 35%) with wall motion abnormalities suggestive of TC and a 0.9 × 1 cm echogenic structure in the LV consistent with LVT. She was started on therapeutic anticoagulation and was discharged on oral warfarin with international normalized ratio (INR) goal of 2-3. Both capecitabine and trastuzumab were held during her hospitalization. Repeat TTE after 2 weeks showed an LVEF of 60% with normal LV systolic function and absence of any LVT. Symptoms-wise her right-sided weakness was improving. She was continued on capecitabine and warfarin for now, and continued to follow-up outpatient with oncology, cardiology and neurology. Discussion: This case highlights TC and LVT as rare but life-threatening complications of trastuzumab-induced cardiotoxicity. We emphasize the importance of early diagnosis to prevent further complications, such as acute thromboembolic stroke, and the necessity of prompt therapeutic interventions to reduce morbidity and mortality. Additionally, we address the multifactorial aetiology of TC and the need for frequent TTE monitoring in patients undergoing trastuzumab therapy to diagnose these complications early.