Thrombus In False Lumen Research Articles

Surgical strategy and long-term outcomes of dissected carotid artery with false lumen thrombus in acute type A aortic dissection.

Optimal management of involved common carotid artery (CCA) with false-lumen thrombus remains unclear in aortic dissection patients. We aim to investigate outcomes and compare different surgical strategies. This is a retrospective cohort study and the institutional database of acute type A aortic dissection was reviewed. The patients with CCA involvement and extended false-lumen thrombus were enrolled and grouped according to the management of CCA: extra-thoracic carotid artery replacement (CAR) and reconstruction in situ (RIS). Multivariate logistic regression analysis was used to investigate the effect of management on neurological outcomes. Kaplan-Meier method was used for survival analysis and log-rank test was used to compare the difference on survival rate. From March 2011 to December 2019, 68 patients were enrolled (24 in the CAR group and 44 in the RIS group). The overall operative mortality was 7.4% (5 patients) and 21 patients had the incidence of postoperative neurological deficit was (30.9%). The rates of main postoperative complications were similar between the two groups. Twenty-five (56.8%) patients in the RIS group had residual false-lumen thrombus at discharge. In multivariate analysis, CAR was the only independent protective factor of postoperative neurological deficit [odds ratio (OR) =0.03, 95% confidence interval (CI): 0.0-0.61, P=0.02] and age was the only risk factor (OR =1.34, 95% CI: 1.11-1.62, P=0.002). The median follow-up time was 40 (interquartile range, 24-69) months and some of the patients received imaging follow-up. The overall survival rates at 5 and 10 years were 95.8%, and 95.8% in the CAR group and 84.1%, and 76.4% in the RIS group, with no significant difference (P=0.22). No cerebrovascular accident and reintervention occurred and 20 (90.9%) patients with residual false-lumen thrombus had reabsorption of thrombus during the follow-up period. CAR was a thorough technique and could protect patients from postoperative neurological deficit than RIS. Patients in either group could have a satisfying long-term prognosis after surviving from perioperative period. Most patients had reabsorption of residual false-lumen thrombus after anticoagulant therapy.

False lumen hemodynamics and partial thrombosis in chronic aortic dissection of the descending aorta.

Partial thrombosis of the false lumen (FL) in patients with chronic aortic dissection (AD) of the descending aorta has been associated with poor outcomes. Meanwhile, the fluid dynamic and biomechanical characteristics associated with partial thrombosis remain to be elucidated. This retrospective, single-center study tested the association between FL fluid dynamics and biomechanics and the presence and extent of FL thrombus. Patients with chronic non-thrombosed or partially thrombosed FLs in the descending aorta after an aortic dissection underwent computed tomography angiography, cardiovascular magnetic resonance (CMR) angiography, and a 4D flow CMR study. A comprehensive quantitative analysis was performed to test the association between FL thrombus presence and extent (percentage of FL with thrombus) and FL anatomy (diameter, entry tear location and size), fluid dynamics (inflow, rotational flow, wall shear stress, kinetic energy, and flow acceleration and stasis), and biomechanics (pulse wave velocity). Sixty-eight patients were included. In multivariate logistic regression FL kinetic energy (p = 0.038) discriminated the 33 patients with partial FL thrombosis from the 35 patients with no thrombosis. Similarly, in separated multivariate linear correlations kinetic energy (p = 0.006) and FL inflow (p = 0.002) were independently related to the extent of the thrombus. FL vortexes, flow acceleration and stasis, wall shear stress, and pulse wave velocity showed limited associations with thrombus presence and extent. In patients with chronic descending aorta dissection, false lumen kinetic energy is related to the presence and extent of false lumen thrombus. In patients with chronic aortic dissection of the descending aorta, false lumen hemodynamic parameters are closely linked with the presence and extent of false lumen thrombosis, and these non-invasive measures might be important in patient management. • Partial false lumen thrombosis has been associated with aortic growth in patients with chronic descending aortic dissection; therefore, the identification of prothrombotic flow conditions is desirable. • The presence of partial false lumen thrombosis as well as its extent was related with false lumen kinetic energy. • The assessment of false lumen hemodynamics may be important in the management of patients with chronic aortic dissection of the descending aorta.

Longitudinal investigation of aortic dissection in mice with computational fluid dynamics

Predicting late adverse events in aortic dissections is challenging. One commonly observed risk factor is partial thrombosis of the false lumen. In this study we investigated false lumen thrombus progression over 7 days in four mice with angiotensin II-induced aortic dissection. We performed computational fluid dynamic simulations with subject-specific boundary conditions from velocity and pressure measurements. We investigated endothelial cell activation potential, mean velocity, thrombus formation potential, and other hemodynamic factors. Our findings support the hypothesis that flow stagnation is the predominant hemodynamic factor driving a large thrombus ratio in false lumina, particularly those with a single fenestration.

Abstract 14815: Clinical Prediction Model of Growth Rate in Type B Aortic Dissection Using 4D Flow MRI

Introduction: Chronic type B aortic dissection is often associated with aneurysmal degeneration and rupture of the descending aorta (DAo). Early identification of patients at risk for aneurysmal degeneration could identify candidates for prophylactic surgical intervention. Clinical and static imaging measures (age, early aortic dilation, etc.) have been unable to reliably predict DAo growth rate (GR). Importantly, these measures do not account for dissection hemodynamics, an important driver of GR. We therefore aimed to build a multivariate linear regression model that combines baseline clinical, morphologic, and hemodynamic metrics to predict GR. Methods: Patients who underwent 4D-flow MRI and had ≥9 months of imaging follow-up were identified. Baseline clinical features were obtained from medical records. Morphologic metrics were assessed on baseline imaging and GR (mm/y) was calculated by comparison to follow-up scans. Baseline 4D-flow MRI was used to measure the following parameters in the true lumen: pulse wave velocity (PWV), peak velocity (PV), and forward flow. False lumen thrombus (FLT) was assessed in percentage quartiles (0, 1-25%, 26-50%, 51-75%, >75%) and scored from 0 to 4. Stepwise multivariate regression was conducted to identify a model for best prediction of GR (Figure 1). Results: Thirty-four patients were included (70.0 ± 16.5y; 21 M). On multivariate analysis, we detected a model that significantly correlates with GR (r 2 = 0.55 p < 0.001) by using PWV, FLT, and PV as predictors. In fact, PWV was the strongest predictor overall (r = - 0.54 p = 0.001). Clinical features and other imaging measures showed no association with GR and hence were excluded by stepwise regression analysis. Conclusions: The regression model identified two hemodynamic parameters and FLT as the strongest predictors of GR. This finding suggests that a multitude of hemodynamic factors impact GR and that 4D flow parameters have the potential to improve clinical risk models.

Management Strategy and Radiologic Outcomes of Symptomatic Spontaneous Isolated Superior Mesenteric Artery Dissection Based on Angiographic Classification: The Follow-Up Experience in a Single Center

Purpose: To investigate the demographics, clinical features, radiologic measurement, treatment, and outcomes of symptomatic spontaneous isolated superior mesenteric artery dissection (SISMAD) according to computed tomography (CT) classification. Methods: This retrospective study included 201 patients diagnosed with symptomatic SISMAD from November 2014 to December 2020. Symptomatic spontaneous isolated superior mesenteric artery dissection was categorized into four types based on CT images by Yun’s angiographic classification. Their clinical characteristics, images features, treatment methods, and radiological outcomes were comparatively analyzed by CT angiographic types. Results: SISMADs were categorized into type I (13.9%) patent false lumen (FL) with both entry and re-entry; type IIa (37.3%), blind pouch of FL; type IIb (43.3%), thrombosed FL; and type III (5.5%), and the occlusion of superior mesenteric artery (SMA). Type IIb, the most common SISMAD, showed the largest true lumen (TL) residual diameter and the lowest percentage of TL stenosis. Type III positioned most proximally to SMA origin and had the maximum dissection length. Symptomatic spontaneous isolated superior mesenteric artery dissections underwent conservative (75.1%), endovascular (22.4%), and surgical (2.5%) treatment. Conservative treatment was more frequent in type I (85.7%) and type IIb (83.9%) than in type IIa (65.3%) and type III (45.5%). Endovascular intervention was more commonly utilized in type IIa (32.0%) and type III (36.4%) than in type I (14.3%) and type IIb (14.9%). Conservative patients achieved FL vanishment/shrinkage (57.8%), stabilization (26.6%), and enlargement (15.6%). After conservative treatment, type I showed angiographic FL stabilization; type IIa achieved FL shrinkage (48.1%), stabilization (22.2%), and enlargement (29.6%); type IIb exhibited FL vanishment/shrinkage (92.0%) and enlargement (8.0%). Cumulative rate of stent patency was 92.3% during 6-year follow-up. Conclusions: Conservative management with close follow-up is initially provided especially for types I and IIb. Morphological stabilization is more frequent in type I of patent FL with entry and re-entry. False lumen vanishment or shrinkage was more likely to occur in type IIb due to the thrombus absorption. Endovascular intervention has excellent long-term in-stent patency and is predominantly utilized in types IIa and III. Blood flow sustained into a blind-ending FL causes the TL compression and stenosis in type IIa. Type III with the occlusion of SMA has the high risk of bowel ischemia. Clinical Impact According to Yun’s angiographic classification of spontaneous isolated superior mesenteric artery dissection (SISMAD), type I (13.9%) has patent true and false lumen and the morphological pattern is maintained stable; type IIa (37.3%) possesses a patent blind-ending false lumen which might shrink, remain unchanged, or enlarge; and endovascular intervention is suggested when conservative treatment failed; type IIb (43.3%) recovers spontaneously due to the absorption of false lumen thrombus and conservative treatment is preferentially considered; type III (5.5%) with the occlusion of main trunk carries a high risk of bowel necrosis, early endovascular intervention is proposed, and open surgery might be necessary.

Impact and risk factors associated with false lumen thrombus status within stent segments of type B aortic dissection after endovascular repair

article: Impact and risk factors associated with false lumen thrombus status within stent segments of type B aortic dissection after endovascular repair - Italian Journal of Vascular and Endovascular Surgery 2022 September;29(3):100-6 - Minerva Medica - Journals

Volumetric Measurements Improve the Accuracy of Aortic Remodeling Prediction in Aortic Dissection.

Accessing aortic remodeling status through regular follow-ups is essential for acute type A aortic dissection patients undergone surgical treatment. Aortic remodeling status was usually determined using diameter or area measurements of the true and false lumen in specific anatomical slices of medical images. However, these indicators only represent partial information about the aorta and can hardly characterize the overall aorta situation. In this study, we included two types of morphology features collected from computed tomography angiography images to predict the aortic remodeling. One type is the volumetric measurements of the true and false lumen, which provide a better overall description of the aorta, and the other type is the volumetric measurements of the thrombus in false lumen and the patent false lumen, which present more detailed information of the dissection. Through progressively incorporating these measurements into the construction of the remodeling prediction model, we investigated the importance of the features that describe the overall situation and that characterize aortic internal details in remodeling prediction, especially the effect of quantitative thrombosis features. The results showed that with the inclusion of the two types of volume features, the prediction accuracy of the model increased, which proves that volumetric measurements of aortic dissection, especially the volume of thrombus, are of significant value in aortic remodeling prediction, and should be paid more attention on in clinical practice and research areas. Clinical Relevance-Demonstrating the importance of volumetric measurements of true and false lumen thrombus in false lumen and patent false lumen in the prediction of aortic remodeling.

False lumen thrombus following aortic dissection diagnosed as the source of repeat lower extremity emboli with angioscopy: a case report

BackgroundAcute arterial embolization caused by a free-floating thrombus of the false lumen after surgery for acute aortic dissection is a rare complication; hence, determining its cause may be difficult. We report a case in which angioscopy was valuable in diagnosing and treating the unstable thrombus within the false lumen.Case presentationThe patient was a 71-year-old woman who underwent hemiarch replacement for Stanford type A acute aortic dissection. Two months after the operation, left renal infarction occurred. Eighteen months after the operation, the patient visited the hospital for treatment of intermittent claudication of her left leg. Computed tomography (CT) showed occlusion below the left common femoral artery. Surgical thrombectomy was performed for acute lower extremity arterial occlusion. One month later, thrombectomy was performed again for the same phenomenon and again after 2 months. She had no history of cardiac arrhythmia. No obvious source for the repeat embolization could be found on echocardiography or enhanced CT. Angiography was performed to further identify the cause, revealing a new entry site at the distal anastomosis, which exhibited antegrade flow into the false lumen. Furthermore, selective false lumen angiography via the re-entry revealed a thrombus in the false lumen corresponding to the descending aorta. A non-obstructive angioscopy system in the false lumen revealed a free-floating thrombus. As the patient had undergone multiple surgeries over a short period and desired minimally invasive treatment, coil embolization of the new entry site as well as false lumen was performed. As a result, blood flow from the true to the false lumen resolved. More than 1 year has passed following coil embolization with no signs of embolism.ConclusionsWe experienced a case of repeat embolism caused by unstable thrombus formation in the false lumen resulting from antegrade blood flow in the false lumen secondary to development of a new entry site. Angioscopy revealed that this antegrade flow caused formation of an unstable thrombus which caused recurrent acute lower extremity arterial occlusion. Therefore, angioscopy may be a useful option for the diagnosis of false lumen thrombosis.

False Lumen Thrombosis and Pressure Predicts Outcome in Patients with Acute Type B Aortic Dissection

Introduction: Owing to the uncertainty around how best to manage patients with type B aortic dissection (TBAD), improved risk stratification is a key priority. Partial false lumen thrombus morphology has been demonstrated to predict complications; however, partial thrombosis is poorly defined and has not been evaluated in detail. We hypothesised that partial false lumen thrombosis is a marker of false lumen pressure and that false lumen pressure is related to clinical events.

Proximal false lumen thrombosis is associated with low false lumen pressure and fewer complications in type B aortic dissection

BackgroundImproved risk stratification is a key priority for type B aortic dissection (TBAD). Partial false lumen thrombus morphology is an emerging predictor of complications. However, partial thrombosis is poorly defined, and its evaluation in clinical studies has been inconsistent. Thus, we aimed to characterize the hemodynamic pressure in TBAD and determine how the pressure relates to the false lumen thrombus morphology and clinical events. MethodsThe retrospective admission computed tomography angiograms of 69 patients with acute TBAD were used to construct three-dimensional computational models for simulation of cyclical blood flow and calculation of pressure. The patients were categorized by the false lumen thrombus morphology as minimal, extensive, proximal or distal thrombosis. Linear regression analysis was used to compare the luminal pressure difference between the true and false lumen for each morphology group. The effect of morphology classification on the incidence of acute complications within 14 days was studied using logistic regression adjusted for clinical parameters. A survival analysis for adverse aortic events at 1 year was also performed using Cox regression. ResultsOf the 69 patients, 44 had experienced acute complications and 45 had had an adverse aortic event at 1 year. The mean ± standard deviation age was 62.6 ± 12.6 years, and 75.4% were men. Compared with the patients with minimal thrombosis, those with proximal thrombosis had a reduced false lumen pressure by 10.1 mm Hg (95% confidence interval [CI], 4.3-15.9 mm Hg; P = .001). The patients who had not experienced an acute complication had had a reduced relative false lumen pressure (−6.35 mm Hg vs −0.62 mm Hg; P = .03). Proximal thrombosis was associated with fewer acute complications (odds ratio, 0.17; 95% CI, 0.04-0.60; P = .01) and 1-year adverse aortic events (hazard ratio, 0.36; 95% CI, 0.16-0.80; P = .01). ConclusionsWe found that proximal false lumen thrombosis was a marker of reduced false lumen pressure. This might explain how proximal false lumen thrombosis appears to be protective of acute complications (eg, refractory hypertension or pain, aortic rupture, visceral or limb malperfusion, acute expansion) and adverse aortic events within the first year.

ImageTBAD: A 3D Computed Tomography Angiography Image Dataset for Automatic Segmentation of Type-B Aortic Dissection.

Type-B Aortic Dissection (TBAD) is one of the most serious cardiovascular events characterized by a growing yearly incidence, and the severity of disease prognosis. Currently, computed tomography angiography (CTA) has been widely adopted for the diagnosis and prognosis of TBAD. Accurate segmentation of true lumen (TL), false lumen (FL), and false lumen thrombus (FLT) in CTA are crucial for the precise quantification of anatomical features. However, existing works only focus on only TL and FL without considering FLT. In this paper, we propose ImageTBAD, the first 3D computed tomography angiography (CTA) image dataset of TBAD with annotation of TL, FL, and FLT. The proposed dataset contains 100 TBAD CTA images, which is of decent size compared with existing medical imaging datasets. As FLT can appear almost anywhere along the aorta with irregular shapes, segmentation of FLT presents a wide class of segmentation problems where targets exist in a variety of positions with irregular shapes. We further propose a baseline method for automatic segmentation of TBAD. Results show that the baseline method can achieve comparable results with existing works on aorta and TL segmentation. However, the segmentation accuracy of FLT is only 52%, which leaves large room for improvement and also shows the challenge of our dataset. To facilitate further research on this challenging problem, our dataset and codes are released to the public (Dataset, 2020).

Descending endografts for type A dissections: con.

An important goal of surgical repair of type A aortic dissection is to resect the intimal tear. Studies on the fate of residual dissection after acute type A aortic dissection repair in the past decade have driven surgeons to seek procedures to avoid distal reoperation. Aggressive surgical approach with total arch replacement in acute type A dissection has demonstrated lower incidence of distal reoperation and slower aortic growth rate compared to less aggressive ascending/hemiarch repair. Recently, successful results of thoracic endovascular aortic repair (TEVAR) in type B aortic dissection have encouraged surgeons to further attack acute type A aortic dissection with hybrid approach: antegrade endografting in the descending thoracic true lumen as an adjunct to hemiarch or total arch repair. However, is the hybrid approach with simultaneous descending endografting justified in all the acute type A aortic dissection cases? The outcomes of the hybrid approach reported by the several groups have demonstrated 80-100% of false lumen thrombus formation in the proximal descending aorta (stented segment); however, the complete obliteration of the false lumen is only 17-50%. The incidence of distal reoperation/reintervention after hybrid approach is as high as 14% and an adjunctive procedure is often performed. Moreover, there are concerns about additional risks associated with the hybrid procedures, such as spinal cord injury (SCI), stent graft induced new entry and stroke. The data on this new approach are still very limited. Hence, further study is warranted to prove its safety and durability.

Usefulness of new imaging methods for assessment of type B aortic dissection.

While the medical management of uncomplicated type B aortic dissection has good outcomes in the short term, the longer term mortality can be in the region of 50% at 5 years. Up to 40% of the survivors can have significant dilatation of the false lumen with the risk of aneurysm formation and death due to rupture. The results of the randomized controlled trials ADSORB and INSTEAD-XL have shown that beneficial aortic remodelling occurs after endoluminal stent graft placement, but these trials were underpowered to show any effect on survival. Static computed tomography (CT) angiography imaging methods have been used to try to identify high risk patients using parameters such as diameter, the position and size of the entry tear, and the amount of false lumen thrombus, but these so far are not able to clinically risk stratify individual patients. In this manuscript, we present our initial experience with new MR imaging methods. These have allowed us to develop a greater understanding of aortic dissection by providing information regarding the underlying hemodynamic and biomechanics of the dissection, as well as more accurate assessment of important clinical imaging endpoints, such as false lumen thrombosis.

A New Classification System for Aortic Dissection

All medical classifications group patients into categories that can be used to predict outcome, and therefore can select patients who may benefit from a specific treatment regimen. The paradox of aortic dissection is that there are a multitude of factors that affect outcome, some of which are only just being defined with new imaging techniques and other methodologies. It has been recognised for some time that the established anatomical classifications of aortic dissection (DeBakey and Stanford) together with the chronological division between acute and chronic dissection (at 14 days) are outdated. The management of aortic dissection changed significantly with the advent of endovascular treatment, and a meta-analysis shows that these techniques have a much lower mortality than open surgery in treating patients with complicated acute type B aortic dissection. 1 The premise of endovascular repair is that by covering the primary entry tear, the flow in the false lumen will be reduced so encouraging thrombosis, and the intra-luminal pressure will fall thereby decreasing the risk of aortic expansion and improving end-organ ischaemia. The DISSECT classification is an attempt to modernise the classification of aortic dissection to make it relevant to clinicians of all disciplines treating patients with a combination of medical therapy together with open surgical and endovascular techniques. One of the difficulties in trying to select criteria for any new classification, acknowledged in the paper, is that our understanding of dissection is in its infancy. 2 Almost all clinical decisions are currently based on static images from computed tomography because it is fast, readily available and has excellent spatial resolution. Features evaluated include the size of the false lumen, the total aortic diameter, the amount of false lumen thrombus, and the presence of aortic rupture and end-organ ischaemia. However, there is increasing evidence that functional imaging, particularly using four-dimensional magnetic resonance and ultrasound, gives a much richer data set which can be used to measure haemodynamic information within the false lumen. 3,4 High resolution imaging has also shown that each patient presenting with aortic dissection has a unique set of findings, particularly in terms of the size and location of the primary and secondary entry tears. This information is important for the success of endovascular repair and may help to reduce the high reintervention rate suffered by patients with aortic dissection. 5 At first sight the DISSECT classification is complex and unwieldy;however, all the majorelementsthat need tobe taken intoaccountinpatientswithdissectionareincluded.Someare morecontentiousthanothers,withthedivisionoftheduration ofdissectionintothreecategoriesbeingthemostcontroversial (as recognised by the authors). There is widespread dissatisfaction with the current division into acute and chronic based on14days.The introduction ofa sub-acute phase lastingfrom 14daystothreemonthsisalsofairlyarbitrary.Theabilityofthe aorta to remodel is one of the most important factors in the successofendovascularrepair.Theduration ofthisplasticityis likely to be patient-specific and movement of the dissection flap can be detected in some patients well after the threemonth limit of the proposed sub-acute phase. A classification based on the rigidity of the dissection flap may be shown in future to be more relevant than any set time limit. Endovascular techniques will, in future, be applied to dissections with the entry tear in the ascending aorta, and will include complex devices incorporating aortic valve components and branches for the coronary arteries. Patient-specific treatment based on accurate individual risk stratification from functional imaging may well provide the best way forward. A classification system such as DISSECT will undoubtedly continue to have an important role but will need to be continually updated as new information becomes available from high-quality clinical trials.

Thoracic Endovascular Aortic Repair for Retrograde Type A Aortic Dissection with an Entry Tear in the Descending Aorta

PurposeTo report the immediate and follow-up outcome of thoracic endovascular aortic repair (TEVAR) in highly selected patients with retrograde type A aortic dissection (RAAD) and an entry tear in the descending aorta. Materials and MethodsTEVAR was performed in 17 patients with RAAD and an entry tear in the descending aorta. None of the patients had severe aortic regurgitation, cardiac tamponade, coronary artery involvement, or brain ischemia. The false lumen in the ascending aorta was patent in nine patients. Two patients had acute malperfusion of the branched artery. Computed tomography (CT) was performed 14 days, 3 months, and 6 months after the intervention and annually thereafter. ResultsAll procedures were technically successful, with complete coverage of the entry tear and complete thrombosis of the false lumen in the ascending aorta. All patients survived through the follow-up period (25.7 months ± 17.2). TEVAR resulted in thrombosis of the false lumen, reabsorption of the false lumen thrombus, and enlargement of the true lumen. The mean maximal diameter of the ascending aorta and the false lumen in the ascending aorta significantly decreased after TEVAR. At the distal edge of the stent graft, the mean diameter of the descending aorta and the false lumen markedly decreased after TEVAR. Complete thrombosis of the false lumen was observed at the distal edge of the stent graft in 16 (94.1%) patients and at the diaphragmatic level in 9 (52.9%) patients. ConclusionsTEVAR for RAAD with an entry tear in the descending aorta is a safe and effective technique in highly selected patients.

Evaluation of Acute Aortic Dissection by Use with Gadolinium Enhanced MR Angiogra p hy: Comparison withSpin-echo MR Image

Purpose: To compare the usefulness of Gadolinium-enhanced MR angiography(Gd-MRA) with spin-echo(SE) MRI for the evaluation of acute aortic dissection. Materials and Methods: During a recent one-year period were trospectively reviewed the results of SE MRI and Gd-MRA in 14 patients (10 males, 4 females; mean age 57 years)with acute aortic dissection. DeBakey type I was found in six patients, DeBakey type II in one, and DeBakey typeIII in seven. MR techniques were as follows. First, multislice multiphase images were obtained in axial, coronal and oblique sagittal planes using SE T1WI(TR/TE/flip angle=600/14/90; acquisition time=25min), and images of selected slices were obtained using breath-hold turbo SE T2WI(TR/TE/flip angle=800/76/160). Second, breath-holdGd-MRA imaging (3D-FISP; TR/TE/Flip angle=4.2/1.7/25; acquisition time=1min) was performed, with oblique sagittal(arch view) orientation. We compared 14 SE MRI images with nine thoracic and five abdominal Gd-MRA images, evaluating the presence and extent of intimal flap, entry and reentry tear, thrombus in false lumen (and comparison to true lumen), the involvement of major branching vessels of the aortic arch, the origin of majorabdominal branching vessels, the presence of hemothorax and hemopericardium. Results : Both SE MRI and Gd-MRA very accurately detected the extent of intimal flap, and false lumen status. For detecting the site of entry tear, and the involvement of major branching vessels at the aortic arch, Gd-MRA(n=12) was more accurate than SE MRI(n=7).When used to image 20 vessels in five patients, Gd-MRA identified with perfect accuracy the origin of majorabdominal branching vessels; SE MRI, however, demonstrated only six of 20 vessels. SE MRI, however, was muchsuperior for the identification of complications such as hemothorax(n=9) and hemopericardium(n=2); in thisrespect, Gd-MRA failed completely. Conclusion: For the evaluation of patients with acute aortic dissection, Gd-MRAprovides information regarding site of entry tear and the involvement of major branching vessels very much fasterthan SE-MRI. In such cases, Gd-MRA can therefore be used for initial investigatory imaging.

Spontaneous dissections of the internal carotid artery: appearances on colour Doppler ultrasound.

Spontaneous dissection of the internal carotid artery (ICA) is an unusual finding. We present an analysis of five patients (aged 40-60 years) with ICA dissections, describing the various flow patterns detected on colour Doppler ultrasound. Particular attention was paid to the presence of a dual lumen, the direction of flow in the false lumen and the velocity/spectral broadening of the Doppler trace obtained from the true and false lumens. Four different patterns were observed. Narrowing of the true lumen by the false lumen thrombus was seen in two cases with a low velocity Doppler waveform; three cases had a patent false lumen ("double lumen" pattern); the direction of flow in the patent false lumen varied from being (i) forward, (ii) reversed and (iii) bidirectional. The flow dynamics in carotid dissections are complex and are primarily dependent upon the presence of thrombus within the false lumen, the entry and exit flaps if the false lumen is patent, the motion of the flap wall and the extent of the dissection. They illustrate the diverse nature of the disease and Doppler ultrasound plays an important role in the imaging of ICA dissections.