Massive pulmonary embolism triggering Takotsubo syndrome initially misdiagnosed as STEMI after knee surgery: a case report and diagnostic pitfall

Background Takotsubo syndrome (TTS) can mimic ST-elevation myocardial infarction (STEMI) on presentation. Pulmonary embolism (PE) is a recognized physical trigger for TTS but the co-occurrence remains uncommon and diagnostically challenging, especially when ST-segment elevation and severe hypoxemia coexist. Case presentation: A 70-year-old woman presented with acute dyspnea and syncope 10 days after arthroscopic meniscal surgery. Initial electrocardiogram (ECG) in a local hospital showed extensive ST-segment elevation (V1–V6, V3R–V5R); she received alteplase for presumed anterior STEMI. Transferred to our intensive care unit (ICU) in shock with hypoxemia, bedside echocardiography showed left ventricular ejection fraction (LVEF) of 40% and low velocity-time integral (VTI) of 12 cm. Emergency coronary angiography (CAG) revealed no obstructive lesions; left ventriculography demonstrated apical akinesia with ballooning, supporting TTS. Given persistent hypoxemia and right-heart strain, CT pulmonary angiography (CTPA) confirmed massive PE. Systemic alteplase was administered per high-risk PE recommendations, alongside intra-aortic balloon pump (IABP) support and heparin. Coagulation was closely titrated (activated partial thromboplastin time [APTT] peaked 93.6 s, fibrinogen nadir 1.45 g/L; corrected with cryoprecipitate). Serial echo documented recovery of LVEF to 50% and rising VTI (to 27.3 cm) with persistent but improving right-heart parameters. She was transitioned to warfarin with low-molecular-weight heparin (LMWH) bridging; international normalized ratio (INR) stabilized around 2.0–2.1 and she was discharged in stable condition. Conclusions In elderly postoperative patients with ST-elevation plus hypoxemia and markedly elevated D-dimer, clinicians should maintain high suspicion for PE-triggered TTS. Rapid integration of CAG/ventriculography, CTPA, serial echocardiography, and dynamic biomarkers can prevent misdiagnosis and optimize therapy (systemic thrombolysis for high-risk PE, tailored hemodynamic support for TTS). This case highlights a diagnostic pitfall and the value of multidisciplinary management.