Off-Pump Methacrylate Cement Pulmonary Embolectomy

Methacrylate is polymer used as a bone cement in orthopedic procedures that can rarely embolize, resulting in atrial perforation and pulmonary artery occlusion. Retrieval of emboli typically requires cardiopulmonary bypass and deep hypothermic circulatory arrest. In this report, we describe the off-pump removal of a massive left pulmonary artery methacrylate embolus using surface ultrasound localization, partial cross-clamping of the main pulmonary artery, and snaring of the of the left pulmonary venous return. Methacrylate is polymer used as a bone cement in orthopedic procedures that can rarely embolize, resulting in atrial perforation and pulmonary artery occlusion. Retrieval of emboli typically requires cardiopulmonary bypass and deep hypothermic circulatory arrest. In this report, we describe the off-pump removal of a massive left pulmonary artery methacrylate embolus using surface ultrasound localization, partial cross-clamping of the main pulmonary artery, and snaring of the of the left pulmonary venous return. Methacrylate is a polymer commonly used as a bone cement in orthopedic procedures such as kyphoplasty. Prior to hardening, the polymer can travel through the systemic venous return, where it solidifies to become a cardiopulmonary embolus. The frequency of methacrylate cardiopulmonary embolism is unknown, but at least 30 patients have been identified with one third reporting systemic symptoms and at least 1 attributable death.1Krueger A. Bliemel C. Zettl R. Ruchholtz S. Management of pulmonary cement embolism after percutaneous vertebroplasty and kyphoplasty: a systematic review of the literature.Eur Spine J. 2009; 18: 1257-1265Crossref PubMed Scopus (228) Google Scholar The true incidence of methacrylate pulmonary embolism may be much higher, given the vague clinical symptoms and the number of patients with asymptomatic emboli. Large emboli may occlude the pulmonary artery or erode the vessel or atrial wall leading to perforation.2Weininger G. Elefteriades J.A. Intracardiac cement embolism.N Engl J Med. 2021; 385: e49Crossref PubMed Scopus (3) Google Scholar,3Swojanowsky P. Brinkmeier-Theofanopoulou M. Schmitt C. Mehlhorn U. A rare cause of pericardial effusion due to intracardiac cement embolism.Eur Heart J. 2018; 39: 3001Crossref PubMed Scopus (4) Google Scholar Depending on the location of the methacrylate embolus, embolectomy typically requires cardiopulmonary bypass and deep hypothermic circulatory arrest. In the case reported below, by localizing the emboli with surface ultrasound, partial clamping of the pulmonary artery trunk, and snaring of the left pulmonary veins, we were able to perform an off-pump pulmonary embolectomy. A 36-year-old woman with anxiety, herniated disc (L3-L4), and lumbar stenosis (L4-S1) underwent kyphoplasty with polymethylmethacrylate medical cement in 2020 for chronic lower back pain. Postoperatively, she developed progressive dyspnea and chest pain. Physical exam and laboratory workup were unremarkable. Outpatient chest radiography suggested a foreign body and computed tomography arteriogram confirmed the presence of a methacrylate embolus within the left pulmonary artery extending to the basilar trunk of the left lower lobe (Figure 1). Transthoracic echocardiogram revealed a normal right ventricular cavity and systolic function. However, given concern for progression of symptoms and risk for erosion of the vessel, a left pulmonary embolectomy was recommended. Pulmonary embolectomy was performed through a left hemiclamshell incision (partial sternotomy with teeing off through the fourth intercostal space). This approach provided access to the proximal pulmonary artery, the distal left pulmonary artery, and the pulmonary veins. It also provided central access for emergent cardiopulmonary bypass. Intraoperative transesophageal echocardiography (TEE) was used to assess global right ventricular function before and during partial clamping of the pulmonary artery trunk. Additionally, TEE along with surface ultrasound placed on the pulmonary artery were used to confirm the location of the methacrylate embolus and directed proximal clamping (Figure 2). Further vascular isolation was achieved through placement of snares around the left superior and inferior pulmonary veins. The clamp on the pulmonary artery trunk occluded all flow through the left pulmonary artery and partially occluded flow through the right pulmonary artery. The patient tolerated partial clamping of the pulmonary artery trunk and snaring of the pulmonary veins without significant hemodynamic compromise and cardiopulmonary bypass was unnecessary. Right ventricular function was monitored throughout clamping with TEE. A longitudinal incision was made in the intrapericardial left main pulmonary artery. The methacrylate embolism was adherent to the endothelium and peeled off the pulmonary arterial wall in several individual pieces (Figure 3). The morphology of the removed embolus correlated with the images obtained by computed tomography arteriogram, TEE, and surface ultrasound of the left pulmonary artery. The pulmonary artery was closed primarily, and no residual embolus was visualized on TEE. Postoperatively, the patient was extubated in the operating room and was discharged home on postoperative day 4. In follow up, she reported resolution of symptoms and denied any shortness of breath.Figure 3Methacrylate embolus removed piecemeal from the left pulmonary artery.View Large Image Figure ViewerDownload Hi-res image Download (PPT) Methacrylate embolus is a potentially devastating complication of kyphoplasty and other common orthopedic procedures. It is thought to occur when the injected polymer remains too fluid or is injected under too much pressure. Surgery remains the primary treatment and is the only way to ensure complete removal of the emboli. Three to 6 months of systemic anticoagulation is a reported alterative to operative management.1Krueger A. Bliemel C. Zettl R. Ruchholtz S. Management of pulmonary cement embolism after percutaneous vertebroplasty and kyphoplasty: a systematic review of the literature.Eur Spine J. 2009; 18: 1257-1265Crossref PubMed Scopus (228) Google Scholar Anticoagulation can prevent thrombus from forming on the methacrylate emboli. Over several months the methacrylate embolus becomes endothelialized and the risk of thrombus propagation minimized. We did note that the methacrylate in our report appeared incorporated into the endothelium of the vessel wall. However, unless removed, the symptoms associated with the initial embolus are unlikely to resolve, and the vessel remains at risk for perforation through erosion of the wall. Given the dense attachments of the methacrylate embolus to the endothelium of the pulmonary artery, catheter-based removal techniques for such emboli would be at risk for catastrophic perforation. Importantly, TEE and surface echocardiography were instrumental in localizing the proximal extent of the emboli, assessing the patency of the main pulmonary artery, and supporting an off-pump embolectomy. The main pulmonary artery was identified by TEE from the mid-esophageal ascending aorta short axis view at 30 ° omniplane. The probe was rotated left, providing a view of the left pulmonary artery and cement embolism. TEE was also utilized to assess right ventricular function intraoperatively during single lung ventilation, pulmonary artery clamping, and embolectomy. Likewise, surface ultrasound of the pulmonary artery was key in ensuring safe proximal clamping. While intraoperative epiaortic ultrasonography has been described in the identification of plaque within the aorta, identification of a foreign body within the pulmonary artery represents a unique application of surface ultrasound.4Glas K.E. Swaminathan M. Reeves S.T. et al.Guidelines for the performance of a comprehensive intraoperative epiaortic ultrasonographic examination: recommendations of the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists; endorsed by the Society of Thoracic Surgeons.J Am Soc Echocardiogr. 2007; 20: 1227-1235Abstract Full Text Full Text PDF PubMed Scopus (61) Google Scholar Despite this success, it is best practice to maintain exposure for rapid central or peripheral cannulation should the need for emergent bypass arise. In this case, the above imaging techniques ensured the safe performance of partial main pulmonary artery cross clamping and left pulmonary artery embolectomy without the need for cardiopulmonary bypass or deep hypothermic arrest.