Pulmonary embolism with coexistent incidental pulmonary cement embolism post vertebroplasty

Abstract

A 46-year-old woman presented with sudden onset of shortness of breath and pleuritic chest pain. A CT pulmonary angiogram identified a 5 cm cement pulmonary embolus within the right main pulmonary artery with a surrounding thrombus. She had undergone an L4 vertebroplasty 3 years prior to presentation for a benign lytic lesion. Cement embolus is a known complication of cement vertebroplasty with incidence rates of approximately 0.9%. Management is usually conservative and associated morbidity and mortality rates are low. It is not known whether a previous cement embolus could provide a nidus for thrombus formation.

Background

Pulmonary cement embolus is a known complication of cement vertebroplasty and has an incident rate of approximately 0.9%.¹ We present an unusual combination of cement pulmonary embolus and subsequent pulmonary embolism. The case raises the possibility that a cement embolism could act as a nidus for thrombus formation.

Case presentation

A 46-year-old woman was admitted to the emergency department with a 2-day history of shortness of breath, pleuritic chest pain and three syncopal episodes. On arrival she was tachycardic (138 beats per minute), with oxygen saturations of 96% on 2 L nasal cannulae and a normal blood pressure (120/87 mm Hg). The patient had a medical history of asthma, right nephrectomy for a polycystic kidney and breast cancer for which she underwent a wide local excision 6 years before with adjuvant chemotherapy and was currently taking tamoxifen. She also underwent a vertebroplasty in 2015 to treat an L4 benign lytic lesion.

Investigations

ECG indicated right ventricular (RV) strain, and blood tests showed an elevated D-dimer (3590 ng/mL) and troponin of 118 µg/L. Chest radiograph at presentation showed hyperdense material projected over the left mediastinum (figure 1). A CT pulmonary angiogram (figures 2 and 3) demonstrated bilateral obstructive filling defects extending bilaterally from the main pulmonary artery in keeping with a saddle embolus. Alongside the acute pulmonary embolus, a 5 cm hyperdensity was identified in the left pulmonary artery consistent with the likely cement embolus. Echocardiogram showed RV strain and dilatation.

Figure 1.

Chest radiograph showing hyperdense opacity in the left hilum.

Figure 2.

Bone-phase CT pulmonary angiogram showing a 5 cm cement pulmonary embolus.

Figure 3.

CT pulmonary angiogram contrast phase showing bilateral pulmonary emboli.

Treatment

She was given treatment-dose subcutaneous low-molecular-weight heparin and monitored in the coronary care unit. She was subsequently started on lifelong oral anticoagulation with a direct oral anticoagulation. Tamoxifen was stopped due to theoretical venous thromboembolism risk, and staging CT abdomen and pelvis (CTAP) showed no signs of metastatic disease.

Outcome and follow-up

At follow-up with the respiratory department in May 2018, she continued to be symptomatic with breathlessness. She was referred for elective investigation under the pulmonary hypertension service but no evidence of pulmonary hypertension was found on right heart catheterisation or echocardiogram. A repeat CTAP revealed that the cement embolus remained unchanged with a subtle residual web within the right pulmonary artery but no significant residual thrombus. She remains under local respiratory follow-up with annual echocardiograms to monitor for signs of pulmonary hypertension.

Discussion

Cement embolisation is a known complication of both vertebroplasty and kyphoplasty procedures with incidence rates of 0.9% and 0.4%, respectively.¹ Polymethylmethacrylate (PMMA) quickly polymerises once injected but can leak into the thoracic venous system via the basivertebral veins into the vertebral venous plexus² and then migrate to distant sites, including the vasculature of the lung. The lack of valves in the vertebral venous plexus could perhaps permit the migration of a substantial piece of cement.³ Alternatively, small fragments may aggregate distally and harden to form a larger deposit in the lung vessels. Viscosity is an important factor, and it is postulated that a lower viscosity cement may have a higher risk of embolism⁴ and facilitate migration and formation in more distant sites such as the pulmonary arteries.

Patients typically present with symptoms weeks or months after the procedure.⁵ This is an unusual case as the patient presented 3 years post vertebroplasty with symptoms secondary to a large pulmonary embolus. The cement embolus was not identified at the time of the procedure and the patient was asymptomatic preceding the subsequent pulmonary embolus. There are several factors which may suggest that the cement embolism may not have influenced the formation of the pulmonary embolus; however, the evidence is currently unclear.

It is possible that the cement embolus could have acted as a nidus for the formation of the pulmonary embolus; however, after 3 years, we would expect a degree of endothelialisation of the embolus.⁶ There is a reported case of symptomatic pulmonary embolism 5 years post vertebroplasty, concluding that PMMA migration triggered the formation of an intra-atrial thrombus, which later partially dislodged to the pulmonary vasculature.⁷ However, there is lack of consensus in the literature, with one study advocating that the irregular nano-polymer surface of PMMA increases platelet adhesion and thrombus formation,⁸ whereas an in vitro study suggested no increased thrombotic risk.⁹ Furthermore, the subsequent pulmonary embolism was bilateral as opposed to the initial cement pulmonary embolus which occupied the right main pulmonary artery.

There is no standardised screening process for asymptomatic patients following vertebroplasty. There has been suggestion that post-vertebroplasty chest radiograph screening may help to identify cement embolism; however, this is not a routine practice.¹⁰ In cases of symptomatic cement pulmonary embolism, evidence from case reports suggests that therapeutic anticoagulation may be indicated.¹¹ It is important to be aware of cement emboli as a potential complication both in the immediate postoperative period and in the long term.

Learning points.

• Cement pulmonary embolism is an unusual but potentially serious complication of vertebroplasty.

• Routine chest X-ray post vertebroplasty may be helpful for early detection but may not alter management.

• More cases and research are needed to know whether cement emboli increase risk of thromboembolic complications in the long term.