Floating Clots in the Descending Aorta Associated With the Impella Cardiac Power: Importance of Transoesophageal Echocardiography

Abstract

To the Editor Ventricular septal defect (VSD) is a lethal complication of acute myocardial infarction (AMI) that presents with rapid clinical deterioration due to acute heart failure and cardiogenic shock1. Impella CP (Cardiac Power; Abiomed, Inc., Danvers, MA) support improves the haemodynamic and end-organ function and may improve the surgical outcomes for patients with cardiogenic shock due to VSD after AMI2,3. The incidence of thrombotic complications with Impella has been reported to be 0.7% in the Japanese registry4. However, true incidence of thrombotic complications in patients with Impella CP can be underestimated or underrecognized given extremely high baseline mortality and morbidity of this cohort. Herein, we report a rare case of a massive thrombus floating along the Impella CP device in the descending aorta despite the administration of adequate anticoagulant therapy. In our case report, perioperative transoesophageal echocardiography (TEE) was useful for the designation and optimal management of the treatment strategy. A 68-year-old male (height, 1.68 meters and weight, 45.5 kg) with dyspnea was diagnosed with acute coronary syndrome and transferred to our hospital. His coagulation status on the admission was as follows: international normalized ratio (INR) 1.7, activated partial thromboplastin time (aPTT) 37.8 s, fibrinogen level 396 mg/dL, D-dimer 6.14 mcg/mL, and platelet count 326 × 103/μL. His peak troponin I level was 3,932 ng/mL and he was in a state of shock. He was intubated and an intra-aortic balloon pump (IABP) was placed via his left femoral artery. Emergency coronary angiography revealed a significant stenosis in the left anterior descending artery and left ventriculography confirmed the presence of a VSD. The primary percutaneous coronary intervention was performed using a drug-eluting stent. After the procedure, the IABP was replaced with the Impella CP device via the right femoral artery with a flow rate of 3.0 L/min. Unfractionated heparin was administered to maintain an activated clotting time (ACT) of 152–229 s and aPTT of 76–166 s. Subsequently, aspirin and clopidogrel were administered. On day 2, the patient was transferred to the operating room to undergo surgical VSD repair. His preoperative coagulation status was as follows: INR 1.7, aPTT 166 s, fibrinogen level 252 mg/dL, and platelet count 165 × 103/μL. The anaesthesia induction was uneventful and a TEE probe was inserted, which showed a mobile huge thrombus extending along the distal aortic arch to the distal descending aorta (Figure 1-A and B and supplementary Video 1). The thrombus in the descending aorta extended as far as it could be observed on TEE. The maximum size of the thrombus in the short-axis view of the TEE was 13 mm x 18 mm. Additional TEE findings included a left-to-right shunt in the left ventricle and severe wall motion abnormalities in the anteroseptal to lateral walls. Heparin was administered during the cardiopulmonary bypass (CPB) procedure to maintain the value of ACT > 400 s. VSD closure was performed using the extended sandwich patch technique via right ventriculotomy5. After the procedure, the patient was weaned from CPB, although the Impella CP was still necessary to maintain the haemodynamics. The thrombus in the descending aorta was unaltered after the CPB. In the intensive care unit (ICU), the Impella CP flow rate was maintained at 2.2–3.0 L/min. Heparin was administered as an anticoagulant therapy, targeting an ACT of 180–210 s. Aspirin and clopidogrel were discontinued. His coagulation status on ICU admission was as follows: INR 1.4, aPTT 53 s, fibrinogen level 171 mg/dL, D-dimer 5.64 mcg/mL and platelet count 173 × 103/μL. Two days after the surgery, a computed tomography (CT) scan showed a thrombus formation around the shaft of the Impella CP (Supplementary Figure 1). His first-measured antithrombin III concentration after admission on that day was 62%. As the haemodynamic of the patient stabilised, removal of the Impella CP was planned for 4 days after the initial surgery. Although the intraoperative TEE showed that the thrombus was smaller than that at the time of the initial surgery, it was still present and mobile (Figure 1-C and Supplementary Video 2). The thrombus extended along the distal aortic arch to the distal descending aorta as during the initial surgery. The maximum size of the thrombus in the short-axis view of the TEE was 10 mm x 18 mm. Impella CP was removed after confirming an ACT value >180 s. The femoral artery on the peripheral side of Impella insertion and the bilateral common carotid arteries were compressed until the cerebral oximetry INVOS™ 5100 (Medtronic, Minneapolis, MN, USA) value showed a decrease, while the Impella CP was removed. The TEE revealed a residual mobile thrombus (Figure 1-D and Supplementary Video 3). After removal, the patient was continued on anticoagulant therapy with heparin and was extubated on postoperative day 8. Warfarin, aspirin, and clopidogrel were administered on postoperative day 8. No obvious embolic or neurological complications were observed in the perioperative period. The patient was discharged from the ICU on postoperative day 24. The descending thrombus disappeared on contrast-enhanced CT on postoperative day 57 (Supplementary Figure 2). In our case, intraoperative TEE revealed a rare Impella-associated thrombus. Previous reports suggest that contrast-enhanced CT and angiography are useful in the diagnosis of the thrombus2,6; however, in severe conditions requiring Impella placement, it is difficult to perform these modalities. Thrombosis associated with Impella can cause sudden organ failure leading to an awful outcome7. Contrary to CT and fluoroscopy, TEE can be performed in the operating room or at the bedside. Perioperative TEE is useful in the perioperative management of the Impella to detect and manage thrombotic complications such as the present case. The literature provides minimal guidance on anticoagulation therapy, and the thromboembolic risks associated with the use of Impella CP may be attributable to the complexity and relative lack of evidence-based Impella-related anticoagulation practices8,9. It is possible that the ACT was shortened when unmonitored, although our institutional anticoagulation management do not differ significantly from the manufacturer's recommendations (goal ACT of 160-180 s)8,9. Although the target ACT range was achieved, the patient's low antithrombin III level might have also contributed to this thrombotic complication. The P2Y12 platelet response assay was not conducted in the present case. Along with the preoperative assessment of coagulation status and potential thrombotic status, the P2Y12 platelet response assay could have been performed to confirm the patient's response to clopidogrel. The floating descending thrombus was accidentally detected by TEE on the second day after Impella CP implantation. So far there have been only three case reports describing patients with Impella CP who were diagnosed with aortic thrombosis2,6,10. Ando M et al. reported a case of floating clots in the descending aorta in a patient who was on femoral venoarterial extracorporeal membrane oxygenation (VA-ECMO) with Impella for cardiogenic shock despite adequate anticoagulation10. In the case, systemic anticoagulation with aPTT of 80 s and antiplatelet therapy were administered. However, as in our case, on the second day after Impella placement, the mobile huge thrombus was revealed in the descending aorta on intraoperative TEE. The authors noted that simultaneous support by femoral VA-ECMO and the Impella device can cause thrombus formation in the descending aorta because of blood stasis, even with appropriate anticoagulation therapy. Sophie et al. reported thrombosis associated with Impella CP utilization, although the details of anticoagulation were unknown6. In their case, angiography at the time of Impella removal 3 days after implantation revealed a thrombosis extending on the entire length of the common femoral artery as well as the distal external iliac artery. Mechanical thrombectomy, anticoagulation, and Impella removal are the main treatment options for thrombosis associated with the Impella6,10. Although the clot remained, we removed the Impella, because the patient's haemodynamic condition had improved. Blind catheter removal of a descending aortic thrombus carries a high risk of embolic stroke. Direct surgical removal of descending aortic thrombus is too invasive to the patient. The thrombus in this case was not chronic. Therefore, we decided to remove the Impella device and provide anticoagulation therapy. In the event of an embolism or enlargement of the thrombus, we would have mechanically removed the thrombus. The multidisciplinary team should make decisions about the Impella management strategy based on risks of vascular occlusion, stroke, bleeding, and device-related infection, and the benefits, such as facilitating rehabilitation. Adequate anticoagulation of a patient with an Impella is difficult to determine, lacks consistency across centers, and challenging aspect of critical care8,9,11. Further research is warranted to guide anticoagulation management during Impella placement. In the present case, we experienced a rare case of massive thrombus formation along the Impella CP device in the descending aorta. In patients with Impella CP placement due to cardiogenic shock, thrombus formation in the descending aorta should be kept in mind even with appropriate anticoagulation therapy, and perioperative TEE should be useful for diagnosis and therapeutic decision making. 1Ibanez B, James S, Agewall S, et al. 2017 ESC Guidelines for the management of acute myocardial infarction in patients presenting with ST-segment elevation: The Task Force for the management of acute myocardial infarction in patients presenting with ST-segment elevation of the European Society of Cardiology (ESC). Eur Heart J. 2018;39:119-77.2Saito S, Shibasaki I, Matsuoka T, et al. Impella support as a bridge to heart surgery in patients with cardiogenic shock. Interact Cardiovasc Thorac Surg. 2022;35:ivac088.3Ancona MB, Regazzoli D, Mangieri A, et al. Post-infarct ventricular septal rupture: early Impella implantation to delay surgery and reduce surgical risk. Cardiovasc Interv Ther. 2017;32:381-5.4Ikeda Y, Ako J, Toda K, et al. Short-Term Outcomes of Impella Support in Japanese Patients With Cardiogenic Shock Due to Acute Myocardial Infarction ― Japanese Registry for Percutaneous Ventricular Assist Device (J-PVAD) ―. Circ J. (in press).5Kinoshita T, Asai T, Hachiro K, et al. Extended Sandwich Patch Technique via Right Ventriculotomy for Acute Ventricular Septal Rupture. Ann Thorac Surg. 2022;113(4):1200-07.6Degrauwe S, Iglesias JF, Glauser F, et al. Successful percutaneous mechanical thrombectomy of an Impella CP-related femoral artery thrombosis. Cardiol J. 2021;28(1):185-6.7Yamana F, Domae K, Kawasumi R, et al. Aortic thrombosis with visceral malperfusion during circulatory support with a combination of Impella and extracorporeal membrane oxygenation for postcardiotomy cardiogenic shock. J Artif Organs. Published online January 27, 2023.8Beavers CJ, DiDomenico RJ, Dunn SP, et al. Optimizing anticoagulation for patients receiving Impella support. Pharmacother J Hum Pharmacol Drug Ther. 2021;41:932-42.9Reed BN, DiDomenico RJ, Allender JE, et al. Survey of Anticoagulation Practices with the Impella Percutaneous Ventricular Assist Device at High-Volume Centers. J Intervent Cardiol. 2019;2019:1-6.10Ando M, Garan AR, Axom KM, et al. Floating Clots in the Descending Aorta: A Rare Complication of Femoral Venoarterial Extracorporeal Membrane Oxygenation Combined With Microaxial Pump for Cardiogenic Shock. Circ Heart Fail. 2017;10:e004196.11Succar L, Sulaica EM, Donahue KR, et al. Management of Anticoagulation with Impella® Percutaneous Ventricular Assist Devices and Review of New Literature. J Thromb Thrombolysis. 2019;48:284-91. Supplementary Figure 1. Enhanced computed tomography scan on the postoperative day 2 showing thrombus formation around the shaft of Impella (X). * Thrombus; A, ascending aorta; D, descending aorta. Supplementary Figure 2. An enhanced computed tomography scan on postoperative day 57 showing that the thrombus in the descending aorta had completely disappeared. A, ascending aorta; D, descending aorta. Supplementary Video 1. Intraoperative transoesophageal echocardiography during the ventricular septal defect repair showing a mobile thrombus in the descending aorta. Supplementary Video 2. Intraoperative transoesophageal echocardiography before the removal of Impella CP showing a mobile thrombus in the descending aorta. Supplementary Video 3. Intraoperative transoesophageal echocardiography after the removal of Impella CP showing a mobile thrombus in the descending aorta. All authors have no conflicts of interest to disclose. 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