CT of In Situ Vascular Stump Thrombosis After Pulmonary Resection for Cancer

Acute Pulmonary Embolism: Evidence, Innovation, and Horizons

PURPOSE OF REVIEW

Pulmonary embolism (PE) is the third most common cause of cardiovascular morbidity and mortality. The goal of this review is to discuss the most up-to-date literature on epidemiology, diagnosis, risk stratification, and management of acute PE.

RECENT FINDINGS

Despite an increase in annual incidence rate of PE in the United States and development of multiple advanced therapies for treatment of acute PE, PE-related mortality is not consistently decreasing across populations. Although multiple risk stratification schemes have been developed, it is still unclear which advanced therapy should be used for the individual patient and optimal timing. Fortunately, multiple randomized clinical trials are underway to answer these questions. Nevertheless, up to 50% of patients have persistent reduced quality of life 6 months after acute PE, termed post-PE syndrome. Despite advances in therapeutic options for management of acute PE, many questions remain unanswered, including optimal risk stratification and management of acute PE.

In Situ Pulmonary Arterial Thrombosis-Literature Review and Clinical Significance of a Distinct Entity

Filling defects identified in the pulmonary arterial tree are commonly presumed to represent an embolic phenomenon originating from thrombi formed in remote veins, particularly lower-extremity deep venous thrombosis (DVT). However, accumulating evidence supports an underappreciated cause for pulmonary arterial thrombosis (PAT), namely, de novo thrombogenesis-where thrombosis arises within the pulmonary arteries in the absence of DVT. Although historically underrecognized, in situ PAT has become of heightened importance with the emergence of SARS-CoV-2 infection. In situ PAT is attributed to endothelial dysfunction, systemic inflammation, and acute lung injury, and has been described in a range of conditions including COVID-19, trauma, acute chest syndrome in sickle cell disease, pulmonary infections, and severe pulmonary arterial hypertension. The distinction between pulmonary embolus and in situ PAT may have important implications regarding management decisions and clinical outcomes. In this review, we summarize the pathophysiology, imaging appearances, and management of in situ PAT in various clinical situations. This understanding will promote optimal tailored treatment strategies for this increasingly recognized entity.

Pulmonary Artery Stump Thrombosis: To Treat or Not to Treat? The Question Is Still Open. Description of a Case and Review of the Literature

Pulmonary artery stump thrombosis (PAST) represents a possible complication after lung surgery. We report the case of a 59-year-old man who presented with dyspnoea about 4 years after right pneumonectomy due to squamous cell lung cancer. A CT-scan showed the presence of pulmonary artery stump thrombosis. Although there was no evidence of pulmonary embolism, given the clinical features and radiological shape of the thrombus, anticoagulation treatment with low-molecular-weight heparin was started with improvement of symptoms. The patient was discharged on anticoagulant treatment and a pulmonary CT-scan performed 4 months later showed an almost complete resolution of the PAST. Pathophysiological mechanisms of PAST are still unknown, although several hypotheses have been proposed. However, the decision to treat PAST with anticoagulants is still controversial. A review of literature will be provided in order to discuss risk factors, possible etiologies and to highlight clinical and radiological characteristics that could suggest to treat this condition, in particular when there is an increased risk of complications.

Venous thromboembolism prophylaxis in thoracic surgery patients: an international survey

OBJECTIVES

Venous thromboembolic events (VTE) after thoracic surgery (TS) can be prevented with mechanical and chemical prophylaxis. Unlike other surgical specialties, TS lacks evidence-based guidelines. In the process of developing these guidelines, an understanding of the current prophylaxis methods practiced internationally is necessary and is described in this article.

METHODS

A 26-item survey was distributed to members of the European Society of Thoracic Surgeons (ESTS), American Association of Thoracic Surgery (AATS), Japanese Association for Chest Surgery (JACS) and Chinese Society for Thoracic and Cardiovascular Surgery (CSTCS) electronically or in person. Participants were asked to report their current prophylaxis selection, timing of initiation and duration of prophylaxis, perceived risk factors and the presence and adherence to institutional VTE guidelines for patients undergoing TS for malignancies.

RESULTS

In total, 1613 surgeons anonymously completed the survey with an overall 36% response rate. Respondents were senior surgeons working in large academic hospitals (≥70%, respectively). More than 83.5% of ESTS, AATS and JACS respondents report formal TS thromboprophylaxis protocols in their institutions, but 53% of CSTCS members report not having such a protocol. The regions varied in the approaches utilized for VTE prophylaxis, the timing of initiation perioperatively and the use and type of extended prophylaxis. Respondents reported that multiple risk factors and sources of information impact their VTE prophylaxis decision-making processes, and these factors vastly diverge regionally.

CONCLUSIONS

There is little agreement internationally on the optimal approach to thromboprophylaxis in the TS population, and guidelines will be helpful and vastly welcomed.

European perspectives in Thoracic Surgery, the ESTS venous thromboembolism (VTE) working group

Venous thromboembolism (VTE), composed of deep vein thrombosis (DVT) and PE is a well-recognized cause for significant perioperative morbidity and mortality. While in orthopedic surgery and general oncology surgery there are well established guidelines regarding VTE prophylaxis, based on carefully conducted high level studies, in thoracic surgery the level of evidence and overall knowledge in the field is still lacking, The European Society of Thoracic Surgeons have established an international working group in 2016, whose task was the define contemporary best practice, coordinate research efforts and eventually define best practice guidelines. This collaboration has matured into a multi-organizational effort, with participation of the American Association for Thoracic Surgery, the International Society on Thrombosis and Haemostasis and Chinese and Japanese thoracic societies. Two major projects (International practice survey and an expert group Delphi process re best practice and VTE risk factors) have been completed so far. For 2018, the working group goals will be to establish VTE prophylaxis guidance in Thoracic Surgery.

Computer tomography for venous thromboembolic disease

Venous thromboembolic disease is composed of two disease entities: pulmonary thromboembolism/pulmonary embolism and deep venous thrombosis. Clinical signs and symptoms of venous thromboembolic disease often are nonspecific and, as a result, the diagnosis may be difficult. If left untreated, pulmonary embolism can lead to a potentially fatal outcome. This article focuses on CT angiography as the diagnostic modality for thromboembolic pulmonary embolism and briefly discusses nonthromboembolic pulmonary embolism.

Late pulmonary artery stump thrombosis with post embolic pulmonary hypertension after pneumonectomy

Ten years after right pneumonectomy for primary lung cancer, a 51 year old man developed a pulmonary artery stump thrombosis which produced microemboli in the remaining lung and, in turn, led to chronic pulmonary hypertension. This case strongly suggests that prolonged postoperative thromboembolic prophylaxis should be considered in patients undergoing right pneumonectomy.

Postpneumonectomy Pulmonary Artery Stump Thrombosis: CT Features and Imaging Follow-up

PURPOSE

To retrospectively evaluate the computed tomographic (CT) features of pulmonary artery stump thrombosis at initial and follow-up CT.

MATERIALS AND METHODS

The study was approved by institutional review board, which waived informed consent, and was HIPPA compliant. All patients who had undergone pneumonectomy and CT from January 2001 to August 2003, as identified with data search system, were included. Eighty-nine patients (49 men, 40 women; mean age, 60 years) were studied. Thrombus identification, categorization (concave or convex), and stump and thrombus measurements were made by two radiologists in consensus. The use of anticoagulation therapy was determined from patients' charts. The t test was used.

RESULTS

Initial CT scans were obtained 34 months +/- 67 (standard deviation) after pneumonectomy; multiple CT scans were obtained in 58 patients during follow-up of 25.1 months +/- 24.8. Eleven (12.4%) of 89 patients had stump thrombi with near equal frequency on either side. Five concave and six convex thrombi were initially identified. Anticoagulation was not commenced for stump thrombosis. The mean length of the right stump (31 mm +/- 10) was greater than that of the left stump (13 mm +/- 7) (P < .01). After a right and left pneumonectomy, there was a significant difference between the length of the stump in patients with (right, 40 mm +/- 14; left, 21 mm +/- 11) and patients without thrombosis (right, 30 mm +/- 9; left, 12 mm +/- 6) (P = .027 and P < .01, respectively). Follow-up CT scans were not available in four cases. CT findings demonstrated a reduction in thrombus size in four patients (one received anticoagulation therapy for concomitant pulmonary embolism). Two patients had stable concave thrombi, one with an initial concave thrombus developed convex thrombus, and one with an initial convex thrombus developed concave thrombus. No thrombi propagated outside of the stump.

CONCLUSION

There is a relationship between stump length and the development of in situ thrombosis. The data suggest a rather benign natural history.

Filling Defect in a Pulmonary Arterial Stump on CT After Pneumonectomy: Radiologic and Clinical Significance

OBJECTIVE

The objectives of our study were to determine the incidence of filling defects in pulmonary arterial stumps on CT after pneumonectomy and to evaluate their radiologic and clinical significance.

MATERIALS AND METHODS

We retrospectively reviewed 401 contrast-enhanced chest CT scans of 147 consecutive patients (male-female ratio, 123:24; mean age, 60 years) who underwent pneumonectomy (right, 60; left, 87) from 1996 to 2002 in our institution. CT findings were analyzed for the presence or absence of a filling defect in the vascular stump and its size, shape, and interval change on follow-up CT. CT findings were also evaluated for the length of the vascular stump and the presence of embolism in the contralateral pulmonary arteries, pneumonia, bronchopleural fistula, and bronchiolitis obliterans with organizing pneumonia. Intrathoracic or stump recurrence was also assessed in patients with lung cancer. The medical records of lung cancer patients were reviewed for the cause of pneumonectomy and stage and cell type of cancer at surgery. Statistical tests were performed to determine the relationship between the filling defect and other radiologic and clinical findings.

RESULTS

A filling defect in the vascular stump was seen on CT scans of 18 patients after pneumonectomy (12%), and all had undergone the surgery for lung cancer. It was more frequently found in the right-sided stump (23.3%) than in the left-sided stump (4.6%) (p = 0.001). The vascular stump was longer in patients with a filling defect (37.2 +/- 6.8 [1 SD] mm) than those without this finding (25.0 +/- 12.5 mm) (p < 0.001). Other radiologic and clinical findings were not significantly related to the presence of the filling defect in the vascular stump.

CONCLUSION

A filling defect in the pulmonary arterial stump seen on CT after pneumonectomy is thought to be an in situ thrombus caused by stasis of blood flow and is not related to pulmonary embolism, tumor recurrence, or other complications after pneumonectomy.

CT angiography of pulmonary embolism: diagnostic criteria and causes of misdiagnosis

Computed tomographic (CT) pulmonary angiography is becoming the standard of care at many institutions for the evaluation of patients with suspected pulmonary embolism. This pathologic condition, whether acute or chronic, causes both partial and complete intraluminal filling defects, which should have a sharp interface with intravascular contrast material. In acute pulmonary embolism that manifests as complete arterial occlusion, the affected artery may be enlarged. Partial filling defects due to acute pulmonary embolism are often centrally located, but when eccentrically located they form acute angles with the vessel wall. Chronic pulmonary embolism can manifest as complete occlusive disease in vessels that are smaller than adjacent patent vessels. Other CT pulmonary angiographic findings in chronic pulmonary embolism include evidence of recanalization, webs or flaps, and partial filling defects that form obtuse angles with the vessel wall. Factors that cause misdiagnosis of pulmonary embolism may be patient related, technical, anatomic, or pathologic. The radiologist needs to determine the quality of a CT pulmonary angiographic study and whether pulmonary embolism is present. If the quality of the study is poor, the radiologist should identify which pulmonary arteries have been rendered indeterminate and whether additional imaging is necessary.