Venous thromboembolism: additional diagnostic value and radiation dose of pelvic CT venography in patients with suspected pulmonary embolism

Noninvasive and invasive imaging of lower-extremity acute and chronic venous thrombotic disease

The spectrum of venous thromboembolic (VTE) disease encompasses both acute deep venous thrombosis (DVT) and chronic postthrombotic changes (CPC). A large percentage of acute DVT patients experience recurrent VTE despite adequate anticoagulation, and may progress to CPC. Further, the role of iliocaval venous obstruction (ICVO) in lower-extremity VTE has been increasingly recognized in recent years. Imaging continues to play an important role in both acute and chronic venous disease. Venous duplex ultrasound remains the gold standard for diagnosing acute VTE. However, imaging of CPC is more complex and may involve computed tomography, magnetic resonance, contrast-enhanced ultrasound, or intravascular ultrasound. In this narrative review, we aim to discuss the full spectrum of venous disease imaging for both acute and chronic venous thrombotic disease.

Pulmonary embolism with aortic saddle embolism: a rare presentation

We present an uncommon case report of simultaneous pulmonary embolism and aortic saddle embolism. This patient had risk factors for thromboembolic events that included recent surgery for tibia fracture and immobilisation. She underwent emergency bilateral pulmonary artery catheter-directed thrombolysis, followed by bilateral transfemoral embolectomy. The potential benefit of thrombolysis was weighed against the risk of haemorrhage during the surgery after thrombolysis. Treatment guidelines are not well established for such a condition. This case report illustrates our experience and challenges faced in treating this condition.

Impact of CT venography added to CT pulmonary angiography for the detection of deep venous thrombosis and relevant incidental CT findings

OBJECTIVES

To assess the additional diagnostic value of CT venography (CTV) simultaneously performed with CT pulmonary angiography (CTPA) in the context of thromboembolic disease for the detection of deep venous thrombosis (DVT) and other relevant incidental CT findings.

MATERIALS AND METHODS

Retrospectively and consecutively, we included all patients referred to our emergency department within the last 24 months for suspected pulmonary embolism (PE) who underwent CTPA combined with CTV. Two radiologists blinded to clinical information and results independently analysed CTV images in the context of DVT of the lower extremities and other, unsuspected abdominal/pelvic findings. These latter were classified as relevant with therapeutic consequences or irrelevant. One radiologist reviewed patient clinical records. Inter-observer agreement for DVT detection was calculated.

RESULTS

Of 696 patients, 119 had PE (17.1%) and 54 had DVT (7.8%), 16 (2.3%) of them without concomitant PE. Inter-observer agreement between the two readers was substantial (kappa = 0.78). CTV examinations led to diagnosis of relevant incidental abdominal/pelvic findings in 40 (5.7%) patients, including 11 with new malignant tumours, and 8 with progressive metastatic disease. The evaluated clinical and biological risk factors were not significantly associated with the presence of relevant incidental findings. CTV changed therapeutic management in 29 patients (4.3%): 15 had DVTs without PE, and 14 had abdominal/pelvic findings with therapeutic consequences.

CONCLUSION

CTV simultaneously performed with CTPA offers limited incremental value for detecting DVT. It may reveal other relevant findings leading to therapeutic changes, but the low rate does not justify screening patients with suspected PE.

Evaluation of incidence and clinical significance of obturator hook sign as a marker of chronic iliofemoral venous outflow obstruction in computed tomography venography

OBJECTIVE

The aim of this paper was to describe the obturator hook sign (OHS), a distinctive dilated angled vein similar to a hook, by computed tomography venography (CTV). It is identified mainly on direct CTV (DCTV) as opposed to indirect CTV (ICTV), evidencing obturator vein engorgement as a marker of hemodynamically significant collateralization and representing an indirect sign for chronic iliac vein outflow obstruction.

METHODS

All CTV studies of lower limbs performed from January 2014 to August 2018 in Galway University Hospital and the Galway Clinic were retrospectively reviewed. Data were analyzed using SPSS software (version 25.0; IBM Corp, Armonk, NY).

RESULTS

In total, 531 CTV studies were reviewed, of which 122 (23%) were performed for acute deep venous thrombosis, 183 (35%) for follow-up after iliac stenting, and 109 (21%) for etiologic study of chronic venous disease. For the purpose of analysis for the presence of OHS, only first-time CTV studies were included in patients who were never submitted to venous intervention (n = 296), of which 40 were DCTV (14%) and 256 were ICTV (86%). Two groups were defined according to whether OHS was present, and significant predictors were identified: female sex (P = .038), younger age (P < .0001), DCTV (P < .0001), nonthrombotic iliac vein lesion (P < .001), past history of iliofemoral deep venous thrombosis (P < .0001), and dilated pelvic veins (P < .0001). OHS was significantly more common in chronic occlusions compared with chronic stenosis or acute occlusion (P < .0001). Findings from DCTV and ICTV were compared with results from ascending venography as the "gold standard," and the sign proved to have high specificity and positive predictive value (100% for both tests), whereas sensitivity and negative predictive value were low for both DCTV (65% [95% confidence interval (CI), 43%-84%] and 11% [95% CI, 7%-18%], respectively) and ICTV (8% [95% CI, 4%-14%] and 6% [95% CI, 9%-20%], respectively). From analysis of the remaining CTVs, particularly follow-up after iliac stenting, an interesting fact was recognized: successful venous stenting was associated with OHS disappearance, and stent occlusion was also sometimes associated with OHS reappearance or appearance de novo.

CONCLUSIONS

The identification of hemodynamically significant lesions in patients with clinically significant chronic venous disease is the aim of any form of imaging. In this study, we have depicted a previously undescribed sign that is straightforward to identify, particularly in DCTV, immediately pointing us toward hemodynamically significant chronic iliac venous outflow obstruction diagnosis. It is too early to call it pathognomonic, but perhaps comparative analysis involving data from additional centers could lead to this conclusion.

Magnetic resonance angiography imaging of pulmonary embolism using agents with blood pool properties as an alternative to computed tomography to avoid radiation exposure

PURPOSE

To evaluate the feasibility and accuracy of a combined magnetic resonance angiography (MRA) - magnetic resonance venography (MRV) protocol using contrast agents with blood pool properties, gadofosveset trisodium and gadobenate dimeglumine, in the evaluation of pulmonary embolus (PE) and deep venous thrombosis (DVT) as compared to the standard clinical reference imaging modalities; computed tomography pulmonary angiography (CTPA) and color-coded Duplex ultrasound (DUS).

MATERIALS AND METHODS

This prospective clinical study recruited patients presenting to the emergency department with clinical suspicion for PE and scheduled for a clinically indicated CTPA. We performed both MRA of the chest for the evaluation of PE as well as MRV of the pelvis and thighs to evaluate for DVT using a single contrast injection. MRA-MRV data was compared to the clinical reference standard CTPA and DUS, respectively.

RESULTS

A total of 40 patients were recruited. The results on a per-patient basis comparing MRA to CTPA for pulmonary embolus yielded 100% sensitivity and 97% specificity. There was a small subset of patients that underwent clinical DUS to evaluate for DVT, which demonstrated a sensitivity and specificity of 100% for MRV.

CONCLUSIONS

This single-center, preliminary study using contrast agents with blood pool properties to perform a relatively rapid combined MRA-MRV exam to image for PE and above knee DVT shows potential as an alternative imaging choice to CTPA. Further large-scale, multicentre studies are warranted.

Diagnosis of Deep Venous Thrombosis and Pulmonary Embolism: New Imaging Tools and Modalities

Imaging continues to be the modality of choice for the diagnosis of venous thromboembolic disease, particularly when incorporated into diagnostic algorithms. Improvement in imaging techniques as well as new imaging modalities and processing methods have improved diagnostic accuracy and additionally are being leveraged in prognostication and decision making for choice of intervention. In this article, we review the role of imaging in diagnosis and prognostication of venous thromboembolism. We also discuss emerging imaging approaches that may in the near future find clinical usefulness in improving diagnosis and prognostication as well as differentiating disease phenotypes.

Imaging of acute pulmonary embolism: an update

Imaging plays an important role in the evaluation and management of acute pulmonary embolism (PE). Computed tomography (CT) pulmonary angiography (CTPA) is the current standard of care and provides accurate diagnosis with rapid turnaround time. CT also provides information on other potential causes of acute chest pain. With dual-energy CT, lung perfusion abnormalities can also be detected and quantified. Chest radiograph has limited utility, occasionally showing findings of PE or infarction, but is useful in evaluating other potential causes of chest pain. Ventilation-perfusion (VQ) scan demonstrates ventilation-perfusion mismatches in these patients, with several classification schemes, typically ranging from normal to high. Magnetic resonance imaging (MRI) also provides accurate diagnosis, but is available in only specialized centers and requires higher levels of expertise. Catheter pulmonary angiography is no longer used for diagnosis and is used only for interventional management. Echocardiography is used for risk stratification of these patients. In this article, we review the role of imaging in the evaluation of acute PE.

Usefulness of a Low Tube Voltage: Knowledge-Based Iterative Model Reconstruction Algorithm for Computed Tomography Venography

OBJECTIVES

The objective of this study was to evaluate the use of 80-kVp scans with knowledge-based iterative model reconstruction (IMR) for computed tomography venography (CTV).

METHODS

This prospective study received institutional review board approval; a previous informed consent was obtained from all participants. We enrolled 30 patients with suspected deep venous thrombosis or pulmonary embolism who were to undergo 80-kVp CTV studies. The images were reconstructed with filtered back projection (FBP), hybrid iterative reconstruction (HIR), and IMR. The venous attenuation, image noise, and contrast-to-noise ratio at the iliac, femoral, and popliteal veins were compared on FBP, HIR, and IMR images. We performed qualitative image analysis (image noise, image contrast, image sharpness, streak artifacts, and overall image quality) of the 3 reconstruction methods and measured their reconstruction times.

RESULTS

There was no significant difference in venous attenuation among the 3 reconstruction methods (P > 0.05). On IMR images, the image noise was lowest at all 3 venous locations, and the contrast-to-noise ratio was highest. Qualitative evaluation scores were also highest for IMR images. The reconstruction time for FBP, HIR, and IMR imaging was 25.4 ± 1.9 seconds, 43.3 ± 3.3 seconds, and 78.7 ± 6.0 seconds, respectively.

CONCLUSIONS

At clinically acceptable reconstruction times, 80-kVp CTV using the IMR technique yielded better qualitative and quantitative image quality than HIR and FBP.

Management of Venous Thromboembolisms: Part I. The Consensus for Deep Vein Thrombosis

Deep vein thrombosis (DVT) is a potentially catastrophic condition because thrombosis, left untreated, can result in detrimental pulmonary embolism. Yet in the absence of thrombosis, anticoagulation increases the risk of bleeding. In the existing literature, knowledge about the epidemiology of DVT is primarily based on investigations among Caucasian populations. There has been little information available about the epidemiology of DVT in Taiwan, and it is generally believed that DVT is less common in Asian patients than in Caucasian patients. However, DVT is a multifactorial disease that represents the interaction between genetic and environmental factors, and the majority of patients with incident DVT have either inherited thrombophilia or acquired risk factors. Furthermore, DVT is often overlooked. Although symptomatic DVT commonly presents with lower extremity pain, swelling and tenderness, diagnosing DVT is a clinical challenge for physicians. Such a diagnosis of DVT requires a timely systematic assessment, including the use of the Wells score and a D-dimer test to exclude low-risk patients, and imaging modalities to confirm DVT. Compression ultrasound with high sensitivity and specificity is the front-line imaging modality in the diagnostic process for patients with suspected DVT in addition to conventional invasive contrast venography. Most patients require anticoagulation therapy, which typically consists of parenteral heparin bridged to a vitamin K antagonist, with variable duration. The development of non-vitamin K oral anticoagulants has revolutionized the landscape of venous thromboembolism treatment, with 4 agents available,including rivaroxaban, dabigatran, apixaban, and edoxaban. Presently, all 4 drugs have finished their large phase III clinical trial programs and come to the clinical uses in North America and Europe. It is encouraging to note that the published data to date regarding Asian patients indicates that such new therapies are safe and efficacious. Ultimately, our efforts to improve outcomes in patients with DVT rely on the awareness in the scientific and medical community regarding the importance of DVT.

KEY WORDS

Combination therapy; Hypertension; α1-blocker.

Combined Direct and Indirect CT Venography (Combined CTV) in Detecting Lower Extremity Deep Vein Thrombosis

This study aimed to evaluate the diagnostic accuracy of combined direct and indirect CT venography (combined CTV) in the detection of lower extremity deep vein thrombosis (LEDVT). The institutional review board approved the study protocol, and patients or qualifying family members provided informed consent. A total of 96 consecutive patients undergoing combined CTV were prospectively enrolled. A combined examination with digital subtraction angiography (DSA) plus duplex ultrasonography (US) was used as the criterion standard. Three observers were blinded to clinical, DSA, and US results, and they independently analyzed all combined CTV datasets. Interobserver agreement was expressed in terms of the Cohen k value for categorical variables. Accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of combined CTV in the detection of LEDVT were determined by using patient- and location-based evaluations. Of the 96 patients, DSA plus US revealed LEDVT in 125 segmental veins in 63 patients. Patient-based evaluation with combined CTV yielded an accuracy of 96.9% to 97.9%, a sensitivity of 95.2% to 96.8%, a specificity of 100% to 100%, a PPV of 100% to 100%, and an NPV of 91.7% to 94.3% in the detection of LEDVT. Location-based evaluation yielded similar results. Through combined direct and indirect CTV, patients obtained a combined CT angiogram on the diseased limb and an indirect CT angiogram on the opposite side. The image quality of combined CTV was superior to an indirect venogram. Combined CTV shows promising diagnostic accuracy in the detection of LEDVT with 3-dimensional modeling of the lower limb venous system.

Interobserver Agreement between On-Call Radiology Resident and General Radiologist Interpretations of CT Pulmonary Angiograms and CT Venograms

Objectives

To evaluate the interobserver agreement (IOA) between the initial radiology resident and the final staff radiologist reports of combined computed tomographic pulmonary angiograms (CTPA) and computed tomographic venograms (CTV) performed during on-call hours.

Materials and Methods

Approval by the institutional review board was obtained. Six-hundred and ninety-six consecutive studies (CTPA or CTPA with CTV) performed during on-call hours and interpreted by 30 residents were identified. Radiology residents’ reports were compared to the final staff reports. Three tests outcomes were considered (positive, P; negative, N; indeterminate, I). Discordant cases were reviews by a chest radiologist.

Results

CTPAs were reported by staff radiologists as positive for pulmonary embolism (PE) in 18% (126/694), with a kappa of 0.81 (95% CI 0.77-0.86) with 3 outcomes (P, N, I), and a kappa of 0.89 (95% CI 0.85-0.94) with 2 outcomes (P, N). Regarding PE location, good concordance was observed for positive studies, with a kappa of 0.86 (95% CI 0.78 – 0.95). CTVs were reported as positive by staff radiologists in 8.5% (33/388), with a kappa of 0.66 (95% CI 0.55-0.77) with 3 outcomes (P, N, I), and a kappa of 0.89 (95% CI 0.8-1.0) with 2 outcomes (P, N). The IOA between residents and staff radiologists increased with increasing residency year level for CTPAs, but did not for CTVs.

Conclusions

Very good and good IOA were observed between resident and staff radiologist interpretations for CTPA and CTV, respectively, with tendency towards improved IOA as residency level of training increased for CTPA, but not for CTV.

CT venography for deep vein thrombosis using a low tube voltage (100 kVp) setting could increase venous enhancement and reduce the amount of administered iodine

Objective

To investigate the validity of the 100 kVp setting in CT venography (CTV) in the diagnosis of deep vein thrombosis (DVT), and to evaluate the feasibility of reducing the amount of administered iodine in this setting.

Materials and Methods

After receiving the contrast medium (CM) of 2.0 mL/kg, 88 patients underwent CTV of the pelvis and lower extremities by using one of four protocols: Group A, 120 kVp setting and 370 mgI/mL CM; group B, 120 kVp and 300 mgI/mL; group C, 100 kVp and 370 mgI/mL; group D, 100 kVp and 300 mgI/mL. The groups were evaluated for venous attenuation, vein-to-muscle contrast-to-noise ratio (CNR_VEIN), DVT-to-vein contrast-to-noise ratio (CNR_DVT), and subjective degree of venous enhancement and image quality.

Results

Venous attenuation and CNR_VEIN were significantly higher in group C (144.3 Hounsfield unit [HU] and 11.9), but there was no significant difference between group A (118.0 HU and 8.2) and D (122.4 HU and 7.9). The attenuation value of DVT was not significantly different among the four groups, and group C had a higher absolute CNR_DVT than the other groups. The overall diagnostic image quality and venous enhancement were significantly higher in group C, but there was no difference between groups A and D.

Conclusion

The 100 kVp setting in CTV substantially help improve venous enhancement and CNR_VEIN. Furthermore, it enables to reduce the amount of administered iodine while maintaining venous attenuation, as compared with the 120 kVp setting.

Venous thromboembolism: classification, risk factors, diagnosis, and management

Venous thromboembolism (VTE) is categorised as deep venous thrombosis (DVT) and pulmonary embolism (PE). VTE is associated with high morbidity and causes a huge financial burden on patients, hospitals, and governments. Both acquired and hereditary risks factors contribute to VTE. To diagnose VTE, noninvasive cost-effective diagnostic algorithms including clinical probability assessment and D-dimer measurement may be employed followup by compression ultrasonography for suspected DVT patients and multidetector computed tomography angiography for suspected PE patients. There are pharmacological and mechanical interventions to manage and prevent VTE. The pharmacological approaches mainly target pathways in coagulation cascade nonspecifically: conventional anticoagulants or specifically: new generation of anticoagulants. Excess bleeding is one of the major risk factors for pharmacological interventions. Hence, nonpharmacological or mechanical approaches such as inferior vena cava filters, graduated compression stockings, and intermittent pneumatic compression devices in combination with pharmacological interventions or alone may be a good approach to manage VTE.