Mechanical thrombectomy of a clot-in-transit followed by low-dose systemic lysis: a case report of pulmonary embolism and progressive right heart failure

Background Acute pulmonary embolism (PE) is a life-threatening situation. While anticoagulation should be initiated without any delay in all patients with an intermediate or high clinical probability of PE, individual acute phase treatment in patients with intermediate or intermediate-high-risk PE still can be optimized.Case summary An 82-year-old female patient was referred to our emergency department after experiencing syncope and acute onset of shortness of breath. Computed tomography (CT) of the chest showed central and extensive peripheral PE. Echocardiography additionally revealed a massive and highly mobile clot-in-transit located in the right atrium (RA). Given the size and mobility of the clot-in-transit, we chose to perform an off-label mechanical thrombectomy. Due to repeated PE with progressive right ventricular (RV) failure and high peripheral thrombus burden, we decided to perform low-dose systemic lysis. After 24 h, she showed significant clinical improvement and was discharged later with recovered RV function and dimensions.Discussion In that case, acute PE was complicated by the presence of a large clot-in-transit in the RA. Initially, there was no indication for mechanical thrombectomy or systemic lysis for the patient's intermediate to high-risk PE. The risk of embolization of the very large clot-in-transit prompted us to remove the mobile thrombus mechanically. When the repeated PE resulted in an increase in afterload and progressive right heart failure, we decided to perform low-dose systemic lysis. The off-label use of the FlowTriever (R) prevented the impending embolization of the 14 cm long thrombus from the RA into the pulmonary circulation. In this case, lysis also appears to make sense, particularly given the high peripheral thrombus burden.