Thromboembolism related to heparin-induced thrombocytopenia during Impella support after cardiac surgery for free wall rupture: a case report

Introduction

Left ventricular free wall rupture (LVFWR) after acute myocardial infarction is a severe complication that frequently progresses to cardiac tamponade or circulatory collapse and has an extremely poor prognosis (1,2). Survival requires rapid diagnosis, prompt surgical repair, and mechanical circulatory support devices, which are considered indispensable for perioperative management (1,2). Recently, the Impella device (Abiomed, Danvers, MA, USA) has been increasingly used for left ventricular unloading and cardiac output support, even after cardiac surgery (3,4). However, its use carries risks such as bleeding or thromboembolism; therefore, careful monitoring and management are essential (3-5).

We report the case of a patient with LVFWR after acute myocardial infarction who underwent surgical repair, received postoperative Impella support, and subsequently developed thromboembolism, likely related to the presence of heparin-induced thrombocytopenia (HIT) antibodies. We present this article in accordance with the CARE reporting checklist (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-262/rc).

Case presentation

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

A 72-year-old man presented with chest pain and was transported to Bell-Land General Hospital by ambulance. Acute myocardial infarction was suspected, and percutaneous coronary intervention was scheduled. During preparation in the catheterization room, the patient developed cardiac arrest. Cardiopulmonary resuscitation was immediately initiated, and extracorporeal membrane oxygenation (ECMO) with intra-aortic balloon pumping (IABP) was performed.

After the return of spontaneous circulation, coronary angiography revealed occlusion of the left circumflex artery (Figure 1). Echocardiography revealed pericardial effusion, and emergency pericardial drainage was performed in the catheterization room.

Figure 1 Coronary angiography demonstrated total occlusion of the left circumflex artery (blue arrow).

The patient was transferred to the operating room. After median sternotomy, cardiopulmonary bypass was initiated using ascending aortic and bicaval venous cannulation. Laceration and pulsatile bleeding were observed in the circumflex artery territory (Figure 2). After aortic cross-clamping and cardioplegic arrest, the rupture site was repaired by sandwiching the defect between felt strips.

Figure 2 Laceration in the circumflex artery territory was revealed (blue arrow).

After declamping, left ventricular function was severely impaired, and weaning from cardiopulmonary bypass was impossible. Therefore, ECMO support was reinitiated.

Due to the ongoing bleeding tendency, Impella was not initially chosen; instead, the continuous use of the IABP was prioritized. On postoperative day (POD) 1, after controlling for bleeding, the IABP was upgraded to Impella CP via the right femoral artery, aiming for left ventricular unloading.

The purge solution for the Impella device consisted of 5% dextrose in water with heparin at a concentration of 25 U/mL. Additionally, systemic heparin was administered according to our institutional protocol, maintaining an activated clotting time of approximately 180 to 200 seconds. Circulatory function gradually improved, and ECMO was successfully discontinued on POD 3.

Impella support was maintained, and ventricular recovery was confirmed on POD 9; therefore, removal of the device was planned. The Impella CP was surgically explanted in the catheterization room. Firstly, the right femoral artery was exposed and the distal portion was clamped. Secondly, the Impella device was removed under fluoroscopic guidance. However, the femoral arterial blood flow markedly decreased thereafter. Thromboembolism was suspected, and angiography revealed no flow beyond the terminal aorta (Figure 3). Aortography at the level of the celiac artery revealed that the other major abdominal branches were intact. Bilateral thromboembolectomy using Fogarty catheters was performed, and the large thrombi were retrieved (Figure 4). No thromboembolism was detected in the bilateral distal femoral arteries. Angiography confirmed the restoration of bilateral iliac artery flow (Figure 5). Subsequent latex immunoturbidimetric assays confirmed HIT antibodies, indicating that the thromboembolism was strongly associated with HIT.

Figure 3 Aortic angiography showed no flow beyond the terminal aorta.

Figure 4 Photograph of the retrieved thrombus, shown in fragmented form.

Figure 5 Angiography demonstrated restored bilateral iliac artery flow.

Patient’s family perspective

The patient’s family expressed gratitude for the life-saving surgical intervention and the intensive care provided.

Discussion

The key lesson from this case is that clinical diagnosis of HIT after cardiac surgery with Impella support is extremely difficult. Therefore, HIT should be suspected at all times, and rapid antibody assays should be utilized to allow early detection and timely intervention. These diagnostic challenges are more apparent in patients with LVFWR, a condition with a very poor prognosis in which perioperative circulatory support is often essential for survival. LVFWR is a severe mechanical complication of acute myocardial infarction, with a perioperative mortality rate of approximately 35% (1,2). The most common cause of death is low-output syndrome, and re-rupture occurs in approximately 7.1% of cases (1). Thus, perioperative ECMO, IABP, or Impella support is frequently required for hemodynamic stabilization (1,2).

Impella is effective for unloading the left ventricle and securing cardiac output, with reported benefits including reduced inotrope use and prevention of post-cardiotomy shock (3,6). However, device-related complications such as bleeding and thromboembolism are well-documented (3-5). Therefore, perioperative Impella management requires meticulous attention to achieve a fragile balance between bleeding and thrombosis (4).

HIT is an immune-mediated response to heparin. It causes thrombocytopenia but paradoxically leads to thromboembolism as the main clinical problem (7). Its diagnosis involves the 4Ts score and antibody testing (7,8). However, in patients on Impella, platelet counts commonly decrease, and heparin use is prolonged (9,10). This results in high 4Ts scores, making clinical scoring unreliable (9,10). Therefore, antibody testing is important to exclude HIT in these cases.

In our case, diagnosing and recognizing HIT was also challenging. Firstly, platelet concentrate transfusions were administered almost daily because of postoperative hemorrhagic tendency. Secondly, platelet consumption due to ECMO and continuous hemodiafiltration also affected the platelet count. Therefore, the platelet count fluctuated markedly between approximately 5.2×10⁹/L and 10.8×10⁹/L during Impella CP support, whereas the preoperative value was 18.8×10⁹/L. According to the 4Ts scoring system, in severe postoperative cases such as ours requiring circulatory support, thrombocytopenia and prolonged heparin exposure usually contribute to a moderate score (at least four). Additionally, clinical signs of thromboembolism, such as stroke or renal failure, were likely masked by sedation, anesthesia, and continuous hemodiafiltration. These factors made the diagnosis of HIT even more difficult.

Enzyme-linked immunosorbent and latex immunoturbidimetric assays are rapid, sensitive, and useful for screening, and a negative result can almost exclude HIT (7,9). The serotonin release assay has high specificity and is the diagnostic gold standard. However, it is expensive, technically demanding, and unavailable in most laboratories (7,9).

In clinical settings, a positive rapid test result should be treated as diagnostic, and management should be initiated immediately (4,7,10,11). If HIT is suspected, heparin must be stopped immediately, and the anticoagulant should be switched to argatroban or bivalirudin (4,7,10). For patients on Impella, switching the purge solution to a bicarbonate-based fluid has also been suggested (4,10).

In our case, thromboembolism in the terminal aorta might have been caused by a thrombus formed along the Impella shaft. Shaft thrombosis can occur in the mixed-flow region created by the interaction between the Impella and ECMO (12). Additionally, the tip of the inserter sheath was positioned at the right common iliac artery. Pulling the Impella CP device might have scraped off the thrombus adhering to the shaft, which subsequently accumulated and obstructed the terminal aorta.

From this case, we learned that the prevention and early detection of Impella-associated thromboembolism should be prioritized. Firstly, it is important to recognize that several possible mechanisms can contribute to Impella-related thromboembolism, including HIT and thrombus formation along the Impella shaft within the mixed-flow interaction zone between the Impella and ECMO. Based on these mechanisms, early imaging evaluations such as ultrasonography, contrast-enhanced computed tomography, or angiography, as well as laboratory assessments of HIT, could be considered.

Regarding the removal of the Impella device, the procedure should be performed in an angiography room. If thrombus is detected prior to removal, the Impella catheter should be pulled out as little as possible to prevent scraping off thrombus attached to Impella. Balloon occlusion of the contralateral common iliac artery may also be useful to prevent thromboembolism in the contralateral leg. The Impella device and introducer sheath should then be removed simultaneously while the distal femoral artery is clamped and the puncture site is opened to flush out any thrombus.

If HIT is diagnosed, anticoagulation therapy should be switched from heparin to argatroban or bivalirudin, and the Impella purge solution should be replaced with a bicarbonate-based fluid.

Conclusions

We encountered a case of thromboembolism strongly related to HIT antibodies following Impella support after surgical repair of an LVFWR.

In patients on Impella during early postoperative cardiac surgery, the diagnosis of HIT is especially difficult. Clinicians should maintain a high index of suspicion for Impella-associated thromboembolism and have a thorough understanding of its possible mechanisms. With such knowledge and awareness, appropriate diagnostic investigations and preventive measures can be implemented.

Acknowledgments

We would like to thank Editage (http://www.editage.com) for editing and reviewing this manuscript for English language.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://acr.amegroups.com/article/view/10.21037/acr-2025-262/rc

Peer Review File: Available at https://acr.amegroups.com/article/view/10.21037/acr-2025-262/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://acr.amegroups.com/article/view/10.21037/acr-2025-262/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for the publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Matteucci M, Kowalewski M, De Bonis M, et al. Surgical Treatment of Post-Infarction Left Ventricular Free-Wall Rupture: A Multicenter Study. Ann Thorac Surg 2021;112:1186-92. [Crossref] [PubMed]
2. Matteucci M, Fina D, Jiritano F, et al. Treatment strategies for post-infarction left ventricular free-wall rupture. Eur Heart J Acute Cardiovasc Care 2019;8:379-87. [Crossref] [PubMed]
3. Saito S, Okubo S, Matsuoka T, et al. Impella - Current issues and future expectations for the percutaneous, microaxial flow left ventricular assist device. J Cardiol 2024;83:228-35. [Crossref] [PubMed]
4. Vandenbriele C, Arachchillage DJ, Frederiks P, et al. Anticoagulation for Percutaneous Ventricular Assist Device-Supported Cardiogenic Shock: JACC Review Topic of the Week. J Am Coll Cardiol 2022;79:1949-62. [Crossref] [PubMed]
5. Ikeda 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 2023;87:588-97. [Crossref] [PubMed]
6. Pieri M, D'Andria Ursoleo J, Nardelli P, et al. Temporary mechanical circulatory support with Impella in cardiac surgery: A systematic review. Int J Cardiol 2024;396:131418. [Crossref] [PubMed]
7. Ahmed I, Majeed A, Powell R. Heparin induced thrombocytopenia: diagnosis and management update. Postgrad Med J 2007;83:575-82. [Crossref] [PubMed]
8. Lo GK, Juhl D, Warkentin TE, et al. Evaluation of pretest clinical score (4 T's) for the diagnosis of heparin-induced thrombocytopenia in two clinical settings. J Thromb Haemost 2006;4:759-65. [Crossref] [PubMed]
9. Seto AH, Kern MJ. Thrombocytopenia with Impella: Not a HIT. Catheter Cardiovasc Interv 2023; Epub ahead of print. [Crossref]
10. Sugimura Y, Bauer S, Immohr MB, et al. Heparin-Induced Thrombocytopenia under Mechanical Circulatory Support by Large Impella for Acute Cardiogenic Shock. J Cardiovasc Dev Dis 2021;8:161. [Crossref] [PubMed]
11. Van Edom CJ, Gramegna M, Baldetti L, et al. Management of Bleeding and Hemolysis During Percutaneous Microaxial Flow Pump Support: A Practical Approach. JACC Cardiovasc Interv 2023;16:1707-20. [Crossref] [PubMed]
12. Kishimoto S, Hiraoka A, Chikazawa G, et al. A case of fatal acute saddle embolism of the terminal aorta after long-term support using Impella CP. J Artif Organs 2025;28:622-6. [Crossref] [PubMed]