Complications of cerebral angiography in patients with symptomatic carotid territory ischaemia screened by carotid ultrasound

Accuracy of duplex ultrasonography versus angiotomography for the diagnosis of extracranial internal carotid stenosis

INTRODUCTION

Internal carotid artery (ICA) stenosis causes about 15% of ischemic strokes. Duplex ultrasonography (DUS) is the first line of investigation of ICA stenosis, but its accuracy varies in the literature and it is usual to complement the study with another more accurate exam when faced with significant stenosis. There is a lack of studies that compare DUS with angiotomography (CTA) in the present literature.

METHODS

we performed an accuracy study, which compared DUS to CTA of patients in a tertiary hospital with a maximum interval of three months between tests. Patients were selected retrospectively, and two independent and certified vascular surgeons evaluated each image in a masked manner. When there was discordance, a third evaluator was summoned. We evaluated the diagnostic accuracy of ICA stenosis of 50-94% and 70-94%.

RESULTS

we included 45 patients and 84 arteries after inclusion and exclusion criteria applied. For the 50-94% stenosis range, DUS accuracy was 69%, sensitivity 89%, and specificity 63%. For the 70-94% stenosis range, DUS accuracy was 84%, sensitivity 61%, and specificity 93%. There was discordance between CTA evaluators with a change from clinical to surgical management in at least 37.5% of the conflicting reports.

CONCLUSION

DUS had an accuracy of 69% for stenoses of 50-94% and 84% for stenoses of 70-94% of the ICA. The CTA analysis depended directly on the evaluator with a change in clinical conduct in more than 37% of cases.

Cerebral thromboembolic complications during cerebral angiography and their risk factors in different subgroups: Analysis of 2,457 procedures

PURPOSE

Diagnostic cerebral digital subtraction angiography (DSA) is an invasive examination that involves catheterization of the major supra-aortic arterial trunks and evaluation of intracranial vessels for diagnostic purposes. Although considered the gold standard method for investigating cerebrovascular diseases, DSA carries measurable and potentially serious complication rates. This report describes the frequency of neurological and non-neurological complications of DSA performed in five hospitals in the state of São Paulo, Brazil, and analyzes them in different disease subgroups. It has a special focus on thromboembolic cerebral complications.

METHODS

We retrospectively reviewed clinical records of all adult patients who underwent DSAs between January 2019 and December 2022. Demographic variables, DSA reports, CT/MRI reports, and clinical follow-up notes were reviewed.

RESULTS

Twenty-four patients experienced some type of complication among 2,457 diagnostic DSAs (0.97%). Thromboembolic complications were recorded in 9 patients (0.36%), and access site hematomas larger than 5 cm were registered in six patients (0.24%). There was a statistical trend for thromboembolic complications in patients with cervical and/or intracranial atherosclerosis (p = 0.07), but age was not associated with them (p = 0.93). Patients who received heparin had lower rates of embolic complications than those who did not receive it, but there was no statistically significant difference (p = 0.17). Intravenous administration of heparin showed a trend toward significance with groin hematoma (p = 0.10).

CONCLUSION

Diagnostic catheter DSAs have low complication rates.

Detection of moderate to severe middle cerebral artery atherosclerotic stenosis in stroke patients: Transcranial color-coded duplex sonography versus computed tomography angiography

Background

Intracranial atherosclerotic stenosis is a common cause of ischemic cerebrovascular events and is associated with a high risk of stroke recurrence. This study aimed to assess the diagnostic accuracy of transcranial color-coded duplex sonography for moderate-to-severe middle cerebral artery stenosis in stroke patients.

Methods

A retrospective analysis was carried out, including 31 patients aged ⩾18 years hospitalized for ischemic cerebrovascular event in whom middle cerebral artery stenosis ⩾30% was identified on computed tomography angiography. Transcranial color-coded duplex sonography findings were compared to the degree of stenosis blindly identified on the computed tomography angiography used as the reference method.

Results

Overall, 27 patients had M1 stenosis and the other 4 had M2 stenosis. To detect M2 stenosis ⩾ 50% and ⩾ 70%, stenotic to pre-stenotic ratio ⩾ 2 and ⩾ 3 had a sensitivity of 100%, respectively. To detect M1 stenosis ⩾ 70%, peak systolic velocity ⩾ 300 cm/s had a sensitivity of 53.8% and specificity of 85.7% with area under the receiver-operating characteristic curve of 0.753 (95% confidence interval: 0.568-0.938; p = 0.026), and stenotic to pre-stenotic ratio ⩾ 3 had a sensitivity of 84.6% and a specificity of 78.6% (area under the curve = 0.854; 95% confidence interval: 0.707-1; p = 0.002). Middle cerebral artery/anterior cerebral artery velocity ratio < 0.7 had a sensitivity of 57.1% and specificity of 90% to detect dampened pre-stenotic flow in middle cerebral artery secondary to downstream M1 stenosis ⩾ 70% (area under the curve = 0.800; 95% confidence interval: 0.584-1; p = 0.040).

Conclusion

This study showed that stenotic to pre-stenotic ratio ⩾ 3 was more sensitive than peak systolic velocity ⩾ 300 cm/s to screen M1 stenosis ⩾ 70%. Middle cerebral artery/anterior cerebral artery ratio < 0.7 was a good indirect sign to detect dampened pre-stenotic flow due to M1 stenosis ⩾ 70%.

Unravelling the role of carotid atherosclerosis in predicting cardiovascular disease risk: A review

Carotid atherosclerosis disease assessment can predict the patient's risk of cardiovascular disease (CVD). The purpose of this review is to provide a comprehensive review of carotid atherosclerosis disease's pathophysiology, diagnostic evaluation, imaging applications, and treatment strategies. Carotid atherosclerosis is diagnosed using a variety of techniques, including transcranial Doppler imaging (TCD), computed tomography angiography (CTA), magnetic resonance angiography (MRA), and cerebral digital subtraction angiography (DSA), with duplex ultrasound (DUS) as the primary screening. Measurements of carotid intima-media thickness (CIMT) have drawn attention recently as a marker of early-stage carotid atherosclerosis or CVD risk prediction. The classification of cardiovascular risk may be enhanced by the expanding fields of stress testing and carotid plaque screening.

Duplex ultrasound for diagnosing symptomatic carotid stenosis in the extracranial segments

BACKGROUND

Carotid artery stenosis is an important cause of stroke and transient ischemic attack. Correctly and rapidly identifying patients with symptomatic carotid artery stenosis is essential for adequate treatment with early cerebral revascularization. Doubts about the diagnostic value regarding the accuracy of duplex ultrasound (DUS) and the possibility of using DUS as the single diagnostic test before carotid revascularization are still debated.

OBJECTIVES

To estimate the accuracy of DUS in individuals with symptomatic carotid stenosis verified by either digital subtraction angiography (DSA), computed tomography angiography (CTA), or magnetic resonance angiography (MRA).

SEARCH METHODS

We searched CRDTAS, CENTRAL, MEDLINE (Ovid), Embase (Ovid), ISI Web of Science, HTA, DARE, and LILACS up to 15 February 2021. We handsearched the reference lists of all included studies and other relevant publications and contacted experts in the field to identify additional studies or unpublished data.

SELECTION CRITERIA

We included studies assessing DUS accuracy against an acceptable reference standard (DSA, MRA, or CTA) in symptomatic patients. We considered the classification of carotid stenosis with DUS defined with validated duplex velocity criteria, and the NASCET criteria for carotid stenosis measures on DSA, MRA, and CTA. We excluded studies that included < 70% of symptomatic patients; the time between the index test and the reference standard was longer than four weeks or not described, or that presented no objective criteria to estimate carotid stenosis.

DATA COLLECTION AND ANALYSIS

The review authors independently screened articles, extracted data, and assessed the risk of bias and applicability concerns using the QUADAS-2 domain list. We extracted data with an effort to complete a 2 × 2 table (true positives, true negatives, false positives, and false negatives) for each of the different categories of carotid stenosis and reference standards. We produced forest plots and summary receiver operating characteristic (ROC) plots to summarize the data. Where meta-analysis was possible, we used a bivariate meta-analysis model.

MAIN RESULTS

We identified 25,087 unique studies, of which 22 were deemed eligible for inclusion (4957 carotid arteries). The risk of bias varied considerably across the studies, and studies were generally of moderate to low quality. We narratively described the results without meta-analysis in seven studies in which the criteria used to determine stenosis were too different from the duplex velocity criteria proposed in our protocol or studies that provided insufficient data to complete a 2 × 2 table for at least in one category of stenosis. Nine studies (2770 carotid arteries) presented DUS versus DSA results for 70% to 99% carotid artery stenosis, and two (685 carotid arteries) presented results from DUS versus CTA in this category. Seven studies presented results for occlusion with DSA as the reference standard and three with CTA as the reference standard. Five studies compared DUS versus DSA for 50% to 99% carotid artery stenosis. Only one study presented results from 50% to 69% carotid artery stenosis. For DUS versus DSA, for < 50% carotid artery stenosis, the summary sensitivity was 0.63 (95% confidence interval [CI] 0.48 to 0.76) and the summary specificity was 0.99 (95% CI 0.96 to 0.99); for the 50% to 69% range, only one study was included and meta-analysis not performed; for the 50% to 99% range, the summary sensitivity was 0.97 (95% CI 0.95 to 0.98) and the summary specificity was 0.70 (95% CI 0.67 to 0.73); for the 70% to 99% range, the summary sensitivity was 0.85 (95% CI 0.77 to 0.91) and the summary specificity was 0.98 (95% CI 0.74 to 0.90); for occlusion, the summary sensitivity was 0.91 (95% CI 0.81 to 0.97) and the summary specificity was 0.95 (95% CI 0.76 to 0.99). For sensitivity analyses, excluding studies in which participants were selected based on the presence of occlusion on DUS had an impact on specificity: 0.98 (95% CI 0.97 to 0.99). For DUS versus CTA, we found two studies in the range of 70% to 99%; the sensitivity varied from 0.57 to 0.94 and the specificity varied from 0.87 to 0.98. For occlusion, the summary sensitivity was 0.95 (95% CI 0.80 to 0.99) and the summary specificity was 0.91 (95% CI 0.09 to 0.99). For DUS versus MRA, there was one study with results for 50% to 99% carotid artery stenosis, with a sensitivity of 0.88 (95% CI 0.70 to 0.98) and specificity of 0.60 (95% CI 0.15 to 0.95); in the 70% to 99% range, two studies were included, with sensitivity that varied from 0.54 to 0.99 and specificity that varied from 0.78 to 0.89. We could perform only a few of the proposed sensitivity analyses because of the small number of studies included.

AUTHORS' CONCLUSIONS

This review provides evidence that the diagnostic accuracy of DUS is high, especially at discriminating between the presence or absence of significant carotid artery stenosis (< 50% or 50% to 99%). This evidence, plus its less invasive nature, supports the early use of DUS for the detection of carotid artery stenosis. The accuracy for 70% to 99% carotid artery stenosis and occlusion is high. Clinicians should exercise caution when using DUS as the single preoperative diagnostic method, and the limitations should be considered. There was little evidence of the accuracy of DUS when compared with CTA or MRA. The results of this review should be interpreted with caution because they are based on studies of low methodological quality, mainly due to the patient selection method. Methodological problems in participant inclusion criteria from the studies discussed above apparently influenced an overestimated estimate of prevalence values. Most of the studies included failed to precisely describe inclusion criteria and previous testing. Future diagnostic accuracy studies should include direct comparisons of the various modalities of diagnostic tests (mainly DUS, CTA, and MRA) for carotid artery stenosis since DSA is no longer considered to be the best method for diagnosing carotid stenosis and less invasive tests are now used as reference standards in clinical practice. Also, for future studies, the participant inclusion criteria require careful attention.

Transcranial Color-Coded Sonography Criteria for Moderate and Severe Middle Cerebral Artery Stenosis

This study aimed to establish optimal criteria for evaluation of moderate (50%-69%) and severe (70%-99%) middle cerebral artery (MCA) stenosis with transcranial color-coded sonography (TCCS). A total of 375 cases provided 409 TCCS/digital subtraction angiography vessel pairs. Peak systolic velocity (PSV), end-diastolic velocity (EDV) and mean flow velocity (MFV) of the MCA were measured. The stenotic/distal MFV ratios (SDRs) were calculated. With digital subtraction angiography as a reference, for 50%-69% MCA stenosis, the optimal combined criteria were PSV ≥180 cm/s (sensitivity 95.7%, specificity 64.9% and overall accuracy 69.7%); EDV ≥75 cm/s (90.0%, 66.4% and 68.7%); MFV ≥110 cm/s (95.7%, 64.0% and 69.4%); and SDR ≥2.5 (88.6%, 71.3% and 76.3%). Criteria for 70%-99% MCA stenosis were PSV ≥240 cm/s (93.5%, 89.9% and 85.5%); EDV ≥100 cm/s (96.8%, 89.0% and 87.3%); MFV≥160 cm/s (91.9%, 92.8% and 92.2%); and SDR ≥4 (87.1%, 92.2% and 91.4%). Parameters of the MCA detected by TCCS, especially SDR, may increase accuracy in diagnosis of 50%-69% and 70%-99% MCA stenosis.

Importance of cerebral angiography and intraoperative neuromonitoring in carotid endarterectomy

It is an increasingly common practice to indicate a carotid endarterectomy procedure based on the information provided by non-invasive tests like Duplex ultrasound, MR angiography or CT angiography, thereby obviating the performance of a conventional cerebral angiography. We present a case of symptomatic left carotid artery 80% stenosis in which cerebral angiography showed absence of the right A1 segment and bilateral anterior cerebral artery territories that filled only from a left injection. Just 90seconds after carotid artery clamping at the neck, brain oximetry and somatosensory evoked potentials significantly dropped, that recovered after immediate clamp removal. Endarterectomy was dismissed and a carotid stent was successfully placed. This case highlights the importance of knowing the dynamics of cerebral blood circulation distal to the stenosis. If endarterectomy had been attempted, unawareness of the information provided by the cerebral angiography would have likely result in severe bi-hemispheric ischemia.

Fractional Flow on TOF-MRA as a Measure of Stroke Risk in Children with Intracranial Arterial Stenosis

BACKGROUND AND PURPOSE

Conventional angiography is the criterion standard for measuring intracranial arterial stenosis. We evaluated signal intensity ratios from TOF-MRA as a measure of intracranial stenosis and infarct risk in pediatric stroke.

MATERIALS AND METHODS

A retrospective study was undertaken in children with intracranial arterial stenosis, who had TOF-MRA and conventional angiography performed within 6 months. Arterial diameters were measured for percentage stenosis. ROI analysis on TOF-MRA measured signal intensity in pre- and poststenotic segments, with post-/pre-signal intensity ratios calculated. The Pearson correlation was used to compare percentage stenosis on MRA with conventional angiography and signal intensity ratios with percentage stenosis; the point-biserial correlation was used for infarcts compared with percentage stenosis and signal intensity ratios. Sensitivity, specificity, and positive and negative predictive values were calculated for determining severe (≥70%) stenosis from MRA and signal intensity ratios against the criterion standard conventional angiography. P < .05 was considered statistically significant.

RESULTS

Seventy stenotic segments were found in 48 studies in 41 children (median age, 11.0 years; range, 5 months to 17.0 years; male/female ratio, 22:19): 20/41 (48.8%) bilateral, 11/41 (26.8%) right, and 10/41 (24.4%) left, with the most common site being the proximal middle cerebral artery (22/70, 31%). Moyamoya disease accounted for 27/41 (65.9%). Signal intensity ratios and conventional angiography stenosis showed a moderate negative correlation (R = -0.54, P < .001). Receiver operating characteristic statistics showed an area under the curve of 0.86 for using post-/pre-signal intensity ratios to determine severe (≥70%) carotid stenosis, yielding a threshold of 1.00. Sensitivity, specificity, and positive and negative predictive values for severe stenosis were the following-MRA: 42.8%, 58.8%, 30.0%, and 71.4%; signal intensity ratio >1.00: 97.1%, 77.8%, 71.7%, and 97.4%; combination: 75.5%, 100%, 100%, and 76.8%, respectively. Signal intensity ratios decreased with increasing grade of stenosis (none/mild-moderate/severe/complete, P < .001) and were less when associated with infarcts (0.81 ± 0.52 for arteries associated with downstream infarcts versus 1.31 ± 0.55 for arteries without associated infarcts, P < .001).

CONCLUSIONS

Signal intensity ratios from TOF-MRA can serve as a noninvasive measure of intracranial arterial stenosis and allow identification of high-risk lesions in pediatric stroke.

Autodetect extracranial and intracranial artery stenosis by machine learning using ultrasound

BACKGROUND

and Purpose: This study proposed a machine learning method for identifying ≥50% stenosis of the extracranial and intracranial arteries.

PATIENTS AND METHODS

A total of 8211 patients with both carotid ultrasound and cerebral angiography were enrolled. Support vector machine (SVM) was employed as the machine learning classifier. Carotid Doppler parameters and transcranial Doppler parameters were used as the input features. Feature selection was performed using the Extra-Trees (extremely randomized trees) method.

RESULTS

For the machine learning method, the sensitivities and specificities of identifying stenosis of the extracranial arteries were 88.5%-100% and 96.0%-100%, respectively. The sensitivities and specificities of identifying stenosis of the intracranial arteries were 71.7%-100% and 88.9%-100%, respectively.

CONCLUSIONS

The SVM classifier with feature selection is an efficient method for identifying the stenosis of both intracranial and extracranial arteries. Comparing with traditional Doppler criteria, this machine learning method achieves up to 20% higher in accuracy and 45% in sensitivity, respectively.

Ultrasound assessment of carotid arteries: Current concepts, methodologies, diagnostic criteria, and technological advancements

Following cardiac disease and cancer, stroke continues to be the third leading cause of death and disability due to chronic disease in the developed world. Appropriate screening tools are integral to early detection and prevention of major cardiovascular events. In a carotid artery, the presence of increased intima-media thickness, plaque, or stenosis is associated with increased risk of a transient ischemic attack or a stroke. Carotid artery ultrasound remains a long-standing and reliable tool in the current armamentarium of diagnostic modalities used to assess vascular morbidity at an early stage. The procedure has, over the last two decades, undergone considerable upgrades in technology, approach, and utility. This review examines in detail the current state and usage of this integrally important means of extracranial cerebrovascular assessment.

Intra- and inter-operator reproducibility of automated cloud-based carotid lumen diameter ultrasound measurement

BACKGROUND

Common carotid artery lumen diameter (LD) ultrasound measurement systems are either manual or semi-automated and lack reproducibility and variability studies. This pilot study presents an automated and cloud-based LD measurements software system (AtheroCloud) and evaluates its: (i) intra/inter-operator reproducibility and (ii) intra/inter-observer variability.

METHODS

100 patients (83M, mean age: 68±11years), IRB approved, consisted of L/R CCA artery (200 ultrasound images), acquired using a 7.5-MHz linear transducer. The intra/inter-operator reproducibility was verified using three operator's readings. Near-wall and far carotid wall borders were manually traced by two observers for intra/inter-observer variability analysis.

RESULTS

The mean coefficient of correlation (CC) for intra- and inter-operator reproducibility between all the three automated reading pairs were: 0.99 (P<0.0001) and 0.97 (P<0.0001), respectively. The mean CC for intra- and inter-observer variability between both the manual reading pairs were 0.98 (P<0.0001) and 0.98 (P<0.0001), respectively. The Figure-of-Merit between the mean of the three automated readings against the four manuals were 98.32%, 99.50%, 98.94% and 98.49%, respectively.

CONCLUSIONS

The AtheroCloud LD measurement system showed high intra/inter-operator reproducibility hence can be adapted for vascular screening mode or pharmaceutical clinical trial mode.

Web-based accurate measurements of carotid lumen diameter and stenosis severity: An ultrasound-based clinical tool for stroke risk assessment during multicenter clinical trials

BACKGROUND

This pilot study presents a completely automated, novel, smart, cloud-based, point-of-care system for (a) carotid lumen diameter (LD); (b) stenosis severity index (SSI) and (c) total lumen area (TLA) measurement using B-mode ultrasound. The proposed system was (i) validated against manual reading taken by the Neurologist and (ii) benchmarked against the commercially available system.

METHOD

One hundred patients (73 M/27 F, mean age: 68 ± 11 years), institutional review board approved, written informed consent, consisted of left/right common carotid artery (200 ultrasound scans) were acquired using a 7.5-MHz linear transducer.

RESULTS

The measured mean LD for left and right carotids were (in mm): (i) for proposed system (6.49 ± 1.77, 6.66 ± 1.70); and (ii) for manual (6.29 ± 1.79, 6.45 ± 1.63), respectively and coefficient of correlation between cloud-based automated against manual were 0.98 (P < 0.0001) and 0.99 (P < 0.0001), respectively. The corresponding TLA error, Precision-of-Merit, and Figure-of-Merit when measured against the manual were: 4.56 ± 3.54%, 96.18 ± 3.21%, and 96.85%, respectively. The AUC for the receiving operating characteristics for the cloud-based system was: 1.0. Four statistical tests such as: Two-tailed z-test, Mann-Whitney test, Kolmogorov-Smirnov (KS) and one-way ANOVA were performed to demonstrate consistency and reliability.

CONCLUSIONS

The proposed system is reliable, accurate, fast, completely automated, anytime-anywhere solution for multi-center clinical trials and routine vascular screening.

Dose reduction potential of iterative reconstruction algorithms in neck CTA-a simulation study

OBJECTIVES

This study aimed to determine the degree of radiation dose reduction in neck CT angiography (CTA) achievable with Sinogram-affirmed iterative reconstruction (SAFIRE) algorithms.

METHODS

10 consecutive patients scheduled for neck CTA were included in this study. CTA images of the external carotid arteries either were reconstructed with filtered back projection (FBP) at full radiation dose level or underwent simulated dose reduction by proprietary reconstruction software. The dose-reduced images were reconstructed using either SAFIRE 3 or SAFIRE 5 and compared with full-dose FBP images in terms of vessel definition. 5 observers performed a total of 3000 pairwise comparisons.

RESULTS

SAFIRE allowed substantial radiation dose reductions in neck CTA while maintaining vessel definition. The possible levels of radiation dose reduction ranged from approximately 34 to approximately 90% and depended on the SAFIRE algorithm strength and the size of the vessel of interest. In general, larger vessels permitted higher degrees of radiation dose reduction, especially with higher SAFIRE strength levels. With small vessels, the superiority of SAFIRE 5 over SAFIRE 3 was lost.

CONCLUSIONS

Neck CTA can be performed with substantially less radiation dose when SAFIRE is applied. The exact degree of radiation dose reduction should be adapted to the clinical question, in particular to the smallest vessel needing excellent definition.

Extracranial and Transcranial Color-Coded Sonography Reduce the Need for Angiography Prior to Carotid Endarterectomy

The growing need for carotid endarterectomy must be accompanied by safe and reliable methods of imaging the cerebral circulation. The authors used extracranial and tran scranial color-coded sonography to evaluate the cervical carotid arteries and the basal cerebral circulation in 76 patients prior to surgery, aiming to reduce the need for preop erative angiography. In 3 patients (proximal and distal carotid disease; subtotal occlusion) carotid ultrasound failed to define the nature and extent of stenosis adequately, and thus conventional angiography was performed. Transcranial imaging identified intracranial stenotic disease in 4 patients and interhemispheric collateral flow in 29 patients. All patients underwent carotid endarterectomy without any complications due to inadequate preoperative imaging. An ultrasound-based approach eliminated the need for angiography in the majority of patients with significant implications for risk reduction and financial expenditure.

Preoperative Computed Tomography Angiography for Evaluation of Feasibility of Free Flaps in Difficult Reconstruction of Head and Neck

BACKGROUND

Free tissue transfer has been advocated for anatomic and functional reconstruction of soft tissue defects after surgical removal of an extensive recurrent tumor and/or arising from previous irradiation in the head and neck. We report a case series of difficult reconstruction in the head and neck in which preoperative computed tomography (CT) angiography was utilized to evaluate the feasibility of free flap reconstruction. The preoperative radiological evaluation was performed to determine the availability of reliable vessels for anastomosis in free flap reconstruction. If none was found, regional pedicle flap or palliative treatment was applied instead. The use of CT angiography allows the clinical surgeon to perform precise surgical planning with greater confidence. This may improve surgical results, thereby potentially reducing perioperative morbidity.

METHODS

Twenty CT angiograms were obtained from 20 patients. All patients were men with a mean age of 57.2 years (range, 42-72 years) and were scheduled to undergo difficult reconstruction in the head and neck. All patients (20/20 [100%]) suffered from oral squamous cell carcinoma. They had all received extensive operations and radiation therapy. Eighteen patients (18/20 [90%]) had completed a course of perioperative irradiation. The CT angiography reports were used to perform detailed preoperative surgical planning accordingly. The findings of CT angiography were classified into 3 groups: group I: normal CT angiography (patent recipient arteries) (Fig. 3); group II: abnormal CT angiography (recipient vessels were present but stenosis or atherosclerotic lesions were noted) (Fig. 4); group III: abnormal CT angiography with no patent recipient arteries in bilateral sides of the neck (Fig. 5); CT angiography results were correlated to the operative findings.

RESULTS

The patients were classified into 3 groups based on the angiographic findings. Six patients (6/20 [30%]) were assigned to group I, 8 patients (8/20 [40%]) to group II, and 6 patients (6/20 [30%]) to group III. In groups I and III, all patients (12/12 [100%]) underwent the treatment according to the original preoperative detailed planning. No flap failure was noted in these 2 groups. In group II, 4 patients' recipient vessels (4/8 [50%]) possessed adequate blood flow intraoperatively; hence, microvascular free flaps were transplanted. Venous congestion in 1 case (1/4 [25%]) was noted. The remaining patients in this group (4/8 [50%]) underwent reconstruction with pedicle flaps rather than free flaps because of the lack of suitable target vessels intraoperatively. All flaps (4/4 [100%]) survived. Among the patients who were treated surgically, intraoperative findings were in accordance with those predicted by CT angiography. The total abnormality rate of CT angiography was 70%. Vascular abnormalities detected as a result of preoperative CT angiography led to changes in the operative plan in 50% (10/20) of the patients.

CONCLUSIONS

The use of CT angiography should be considered for difficult microsurgical reconstructions in the head and neck. When an abnormality in vascular anatomy is detected by CT angiography, the surgeon is advised to consider altering the operative plan accordingly. This allows precise operation, thereby maximizing the possibility of an optimal outcome. Changing the operative plan based on results of CT angiography may also help to avoid the difficult situation in which the surgeon finds that there are no suitable recipient vessels for free flap reconstruction during the operation. In addition, CT angiography enables surgeons to conduct the preoperative surgical planning with greater confidence, thereby potentially enhancing the success rate of difficult reconstructions in the head and neck, which in turn would tend to improve the perioperative course for the patient and consequently to improve results by decreasing vascular complication rates.

Impact of Real-World Adherence with Best Medical Treatment on Cost-Effectiveness of Carotid Endarterectomy for Asymptomatic Carotid Artery Stenosis

BACKGROUND

To present a model of decision and cost-effectiveness analysis that allows assessing the trade-off between the short-term risks of performing a carotid endarterectomy (CEA) and the rate of preventable future events and the impact of real-world adherence of best medical treatment (BMT) on cost-effectiveness of both therapeutic options.

METHODS

We used data from the current literature to define values for a base case and perform a sensitivity analysis. The primary end point was a comparison of the fatal and disabling stroke-free survival during a 5-year period in a cohort of hypothetical patients who presented asymptomatic severe carotid stenosis and were treated with either prophylactic CEA or adherent and nonadherent best medical treatment, respectively.

RESULTS

The difference in estimated fatal and disabling stroke-free survival favoring endarterectomy in patients with asymptomatic severe carotid stenosis is 44 days over the course of 5 years in case of nonadherent best medical treatment. Over a 5-year time horizon, prophylactic CEA would be cost-effective in 50.8% of bootstrap replicates and nonpersistent BMT might be economically dominant in 11.1%. The probability that CEA would be cost-effective at a willingness-to-pay (WTP) threshold of Euro 50,000/quality-adjusted life year gained was 71.8%. In 17.9% prophylactic CEA would be more costly and effective than persistent BMT, but its incremental cost-effectiveness ratio was greater than the WTP, so persistent BMT would be optimal.

CONCLUSIONS

In this model, in case of real-world drug adherence, it was likely that a strategy of early endarterectomy might be a cost-effective or even the dominant therapeutic option in comparison with a strategy of medical therapy alone (deferred surgery). If background any-territory stroke rates on contemporary medical therapy would fall substantially below 0.7%, surgery would cease to be cost-effective.

Multimodality Imaging of Carotid Stenosis

Four diagnostic modalities are used to image the following internal carotid artery: digital subtraction angiography (DSA), duplex ultrasound (DUS), computed tomography angiography (CTA), and magnetic resonance angiography (MRA). The aim of this article is to describe the potentials of these techniques and to discuss their advantages and disadvantages. Invasive DSA is still considered the gold standard and is an indivisible part of the carotid stenting procedure. DUS is an inexpensive but operator-dependent tool with limited visibility of the carotid artery course. Conversely, CTA and MRA allow assessment of the carotid artery from the aortic arch to intracranial parts. The disadvantages of CTA are radiation and iodine contrast medium administration. MRA is without radiation but contrast-enhanced MRA is more accurate than noncontrast MRA. The choice of methods depends on the clinical indications and the availability of methods in individual centers. However, the general approach to patient with suspected carotid artery stenosis is to first perform DUS and then other noninvasive methods such as CTA, MRA, or transcranial Doppler US.

An assessment of the cost-effectiveness of magnetic resonance, including diffusion-weighted imaging, in patients with transient ischaemic attack and minor stroke: a systematic review, meta-analysis and economic evaluation

BACKGROUND

Patients with transient ischaemic attack (TIA) or minor stroke need rapid treatment of risk factors to prevent recurrent stroke. ABCD2 score or magnetic resonance diffusion-weighted brain imaging (MR DWI) may help assessment and treatment.

OBJECTIVES

Is MR with DWI cost-effective in stroke prevention compared with computed tomography (CT) brain scanning in all patients, in specific subgroups or as 'one-stop' brain-carotid imaging? What is the current UK availability of services for stroke prevention?

DATA SOURCES

Published literature; stroke registries, audit and randomised clinical trials; national databases; survey of UK clinical and imaging services for stroke; expert opinion.

REVIEW METHODS

Systematic reviews and meta-analyses of published/unpublished data. Decision-analytic model of stroke prevention including on a 20-year time horizon including nine representative imaging scenarios.

RESULTS

The pooled recurrent stroke rate after TIA (53 studies, 30,558 patients) is 5.2% [95% confidence interval (CI) 3.9% to 5.9%] by 7 days, and 6.7% (5.2% to 8.7%) at 90 days. ABCD2 score does not identify patients with key stroke causes or identify mimics: 66% of specialist-diagnosed true TIAs and 35-41% of mimics had an ABCD2 score of ≥ 4; 20% of true TIAs with ABCD2 score of < 4 had key risk factors. MR DWI (45 studies, 9078 patients) showed an acute ischaemic lesion in 34.3% (95% CI 30.5% to 38.4%) of TIA, 69% of minor stroke patients, i.e. two-thirds of TIA patients are DWI negative. TIA mimics (16 studies, 14,542 patients) make up 40-45% of patients attending clinics. UK survey (45% response) showed most secondary prevention started prior to clinic, 85% of primary brain imaging was same-day CT; 51-54% of patients had MR, mostly additional to CT, on average 1 week later; 55% omitted blood-sensitive MR sequences. Compared with 'CT scan all patients' MR was more expensive and no more cost-effective, except for patients presenting at > 1 week after symptoms to diagnose haemorrhage; strategies that triaged patients with low ABCD2 scores for slow investigation or treated DWI-negative patients as non-TIA/minor stroke prevented fewer strokes and increased costs. 'One-stop' CT/MR angiographic-plus-brain imaging was not cost-effective.

LIMITATIONS

Data on sensitivity/specificity of MR in TIA/minor stroke, stroke costs, prognosis of TIA mimics and accuracy of ABCD2 score by non-specialists are sparse or absent; all analysis had substantial heterogeneity.

CONCLUSIONS

Magnetic resonance with DWI is not cost-effective for secondary stroke prevention. MR was most helpful in patients presenting at > 1 week after symptoms if blood-sensitive sequences were used. ABCD2 score is unlikely to facilitate patient triage by non-stroke specialists. Rapid specialist assessment, CT brain scanning and identification of serious underlying stroke causes is the most cost-effective stroke prevention strategy.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

3D reconstruction of a carotid bifurcation from 2D transversal ultrasound images

Visualizing and analyzing the morphological structure of carotid bifurcations are important for understanding the etiology of carotid atherosclerosis, which is a major cause of stroke and transient ischemic attack. For delineation of vasculatures in the carotid artery, ultrasound examinations have been widely employed because of a noninvasive procedure without ionizing radiation. However, conventional 2D ultrasound imaging has technical limitations in observing the complicated 3D shapes and asymmetric vasodilation of bifurcations. This study aims to propose image-processing techniques for better 3D reconstruction of a carotid bifurcation in a rat by using 2D cross-sectional ultrasound images. A high-resolution ultrasound imaging system with a probe centered at 40MHz was employed to obtain 2D transversal images. The lumen boundaries in each transverse ultrasound image were detected by using three different techniques; an ellipse-fitting, a correlation mapping to visualize the decorrelation of blood flow, and the ellipse-fitting on the correlation map. When the results are compared, the third technique provides relatively good boundary extraction. The incomplete boundaries of arterial lumen caused by acoustic artifacts are somewhat resolved by adopting the correlation mapping and the distortion in the boundary detection near the bifurcation apex was largely reduced by using the ellipse-fitting technique. The 3D lumen geometry of a carotid artery was obtained by volumetric rendering of several 2D slices. For the 3D vasodilatation of the carotid bifurcation, lumen geometries at the contraction and expansion states were simultaneously depicted at various view angles. The present 3D reconstruction methods would be useful for efficient extraction and construction of the 3D lumen geometries of carotid bifurcations from 2D ultrasound images.

Central retinal artery occlusion occurring intraoperatively during angiography for subarachnoid hemorrhage: a case report

PURPOSE

To report a case of central retinal artery occlusion that occurred during cerebral angiography for the treatment of vasospasm secondary to subarachnoid hemorrhage.

RESULTS

Examination was notable for 20/Hand Motion vision and an afferent pupillary defect. Fundus examination at the time of the event revealed a cherry red spot typical of central retinal artery occlusion with surrounding edema of the retina and severe attenuation of the arterioles. There were no emboli noted. Review of the angiography confirmed flow to the ophthalmic artery and retina at the start of the procedure, with severely decreased flow noted at the end of the procedure. Five days after presentation, there were notable areas of potential choroidal infarction, indicating that the ophthalmic artery was also involved to some extent. The patient refused fluorescein angiography, which could have provided more insight to the extent of ischemia. Optical coherence tomography also showed diffuse retinal edema. She was monitored for complications resulting from this event with visual acuity remaining largely unchanged.

CONCLUSION

Ophthalmic and central retinal artery occlusions are devastating events that result in severe vision loss. Most patients have some underlying risk factors precluding the initial event. Undergoing angiography, or other invasive vascular procedure, may put the patient at risk for distal vascular occlusions. Our case is unique in that it shows intraoperative imaging of the acute event occurrence.

Pitfalls and complications management in the endovascular treatment of aneurysms

This article reviews complications associated with the endovascular management of intracranial aneurysms, focusing on risk factors, avoidance, recognition, and management. Such complications can be devastating. Both neurologic and nonneurologic complications can occur. Several patient and procedure related parameters can increase the incidence of complications. Reduction of complication rates can be achieved by careful patient selection, meticulous planning and preparation for the procedure, anticipating potential complications, and preparing for their management. Tracking outcomes and a robust case conference can further enhance outcomes. Education of the care team and a collaborative environment can foster greater focus on avoidance of complications.

Whole body magnetic resonance angiography and computed tomography angiography in the vascular mapping of head and neck: an intraindividual comparison

Introduction

The aim of the study was to compare the detectability of neck vessels with contrast enhanced magnetic resonance angiography (MRA) in the setting of a whole-body MRA and multislice computed tomography angiography (CTA) for preoperative vascular mapping of head and neck.

Methods

In 20 patients MRA was performed prior to microvascular reconstruction of the mandible with osteomyocutaneous flaps. CTA of the neck served as the method of reference.

1.5 T contrast enhanced magnetic resonance angiograms were acquired to visualize the vascular structures of the neck in the setting of a whole-body MRA examination. 64-slice spiral computed tomography was performed with a dual-phase protocol, using the arterial phase images for 3D CTA reconstruction. Maximum intensity projection was employed to visualize MRA and CTA data. To retrieve differences in the detectability of vessel branches between MRA and CTA, a McNemar test was performed.

Results

All angiograms were of diagnostic quality. There were no statistically significant differences between MRA and CTA for the detection of branches of the external carotid artery that are relevant host vessels for microsurgery (p = 0.118). CTA was superior to MRA if all the external carotid artery branches were included (p < 0.001).

Conclusions

MRA is a reliable alternative to CTA in vascular mapping of the cervical vasculature for planning of microvascular reconstruction of the mandible. In the setting of whole-body MRA it could serve as a radiation free one-stop-shop tool for preoperative assessment of the arterial system, potentially covering both, the donor and host site in one single examination.

Risk factors of ischemic lesions related to cerebral angiography and neuro-interventional procedures

Embolic stroke is not a rare complication of cerebral angiography. The risk factors for incidental embolism after cerebral angiography were retrospectively examined using diffusion-weighted magnetic resonance imaging (DWI) in 180 patients who underwent 247 angiography procedures, consisting of 174 diagnostic angiography and 73 interventional procedures, and magnetic resonance imaging including DWI within 72 hours after angiography. The two neuroradiologists in our hospital detected embolism after cerebral angiography as high-intensity lesions (HIL) on DWI. The relationships between HIL on DWI and procedural factors were evaluated. DWI after cerebral angiography revealed HIL related to the procedure in 72 of 247 angiographies. In all procedures, age (p < 0.01), past history of cerebral infarction (p < 0.05), anti-platelet therapy (p < 0.05), neuro-intervention (p < 0.01), and total amount of contrast medium (odds ratio [OR] 2.125, 95% confidence interval [CI] 1.045-4.321) were significantly correlated with HIL. In diagnostic angiography, the performance of the procedure by a resident operator (OR 2.526, 95% CI 1.214-5.254) was significantly correlated with HIL. Age, past history of cerebral infarction, and previous anti-platelet therapy determined the risk of atherosclerotic changes in patients. The neuro-intervention and total amount of contrast medium used could predict the risk of time limitations for angiography. Resident operator is also a risk factor. This study demonstrates the importance of improving the risk of time limitations for angiography and the risk due to operator inexperience. Further training of residents may be needed to reduce the occurrence of embolic complications.

Multimodality imaging of carotid atherosclerotic plaque: Going beyond stenosis

Apart from the degree of stenosis, the morphology of carotid atherosclerotic plaques and presence of neovascularization are important factors that may help to evaluate the risk and ‘vulnerability’ of plaques and may also influence the choice of treatment. In this article, we aim to describe the techniques and imaging findings on CTA, high resolution MRI and contrast enhanced ultrasound in the evaluation of carotid atherosclerotic plaques. We also discuss a few representative cases from our institute with the related clinical implications.

Poor agreement in carotid artery stenosis detection by ultrasound between external offices and a vascular center

BACKGROUND

Carotid duplex ultrasonography is the prime investigation used to grade carotid artery stenosis in clinical routine. We compared the carotid ultrasound (US) scans performed externally with our results.

MATERIALS AND METHODS

This retrospective study included 288 patients who had been referred to our outpatient department and initially presented with an external carotid duplex scan report indicating carotid atherosclerosis. The external scans were analyzed and compared with our scans in respect of the accuracy of identification and quantification of stenosis, the criteria used to grade stenosis and the duplex criteria used. Weighted Kappa coefficients (K) were computed to quantify the agreement between internal and external findings.

RESULTS

The majority of the external reports had been performed by radiologists [70.8 % (n = 204)], followed by specialists of internal medicine [19.4 (n = 56)] and by neurologists [9.8 % (n = 28)]. Only slight agreement was registered between the external reports and those performed at our institution with regard to the identification of stenosis (K = 0.2 for the left and K = 0.12 for the right side). Greater agreement was observed in respect of the level of stenosis (K = 0.42 for the right and K = 0.54 for the left side). Overestimation of the level of stenosis was registered for 45 % in the left internal carotid artery (ICA) and 36 % in the right ICA; the overestimation was most pronounced for occlusions and high-grade stenoses, which is a source of great concern for decision-making.

CONCLUSIONS

The present data indicate only a slight agreement between carotid duplex US imaging performed at medical offices and our results.

The ocular pulse amplitude as a noninvasive parameter for carotid artery stenosis screening: a test accuracy study

PURPOSE

To investigate a potential correlation between the ocular pulse amplitude (OPA; i.e., the intraocular pressure difference between the systolic and diastolic phases of the heartbeat) and the severity of carotid artery stenosis (CAS) and to test its role as a screening parameter for CAS during routine ophthalmic examination.

DESIGN

Test accuracy study.

PARTICIPANTS

Patients referred for color duplex ultrasound examination of the extra- and intracranial cerebral arteries were enrolled consecutively.

METHODS

We measured OPA on both eyes by dynamic contour tonometry. Multivariate analyses were performed with risk factors for CAS (age, total cholesterol, low-density lipoprotein, and triglycerides) to compare the diagnostic value of OPA measurements with other non- or minimally invasive screening parameters.

MAIN OUTCOME MEASURES

The difference between OPA measurements in patients with no (<50%) and patients with severe CAS (>70%) as well as the value of OPA measurements to predict the severity of CAS taking further risk factors of CAS into consideration.

RESULTS

One hundred thirty-four eyes of 67 patients (25 women, 42 men) with a mean age of 67±13 years (range, 25-87) were included. The means of the OPA values of those patients showing no CAS (<50%) differed significantly (P = 0.036) from those with a stenosis of ≥70%. The multivariate model produced a statistically significant odds ratio (0.46; P = 0.007) for CAS of ≥70%.

CONCLUSIONS

The results of the present study provide proof of principle that the OPA is reduced in patients with CAS and may be used as a noninvasive, inexpensive, readily available, and unconfounded screening parameter to detect CAS and possibly to reduce the incidence of stroke.

FINANCIAL DISCLOSURE(S)

The authors have no proprietary or commercial interest in any of the materials discussed in this article.

Preprocedural imaging strategies in symptomatic carotid artery stenosis

BACKGROUND

The benefit of carotid endarterectomy (CEA) over best medical therapy was established using intra-arterial angiography (IAA) for patient selection. Its cost, availability, and risk together with the emergence of newer imaging modalities have led to its replacement in the routine assessment of internal carotid artery (ICA) stenosis. The relative performance of these methods should dictate the optimum imaging strategy in symptomatic patients.

METHODS

A previous meta-analysis (NIHR Health Technology Assessment Programme) was reviewed. Medline and PubMed search was performed for relevant publications since 2006 together with a review of the references in retrieved publications.

RESULTS

Compared to IAA, the sensitivity and specificity for noninvasive imaging of a ≥70% to 99% ICA stenosis are duplex ultrasound (DUS): 0.89 (0.85-0.92) and 0.84 (0.77-0.89); time-of-flight magnetic resonance angiography (TOF-MRA): 0.88 (0.82-0.92) and 0.84 (0.76-0.97); contrast-enhanced MRA (CE-MRA): 0.94 (0.88-0.97) and 0.93 (0.89-0.96); and computed tomography angiography: 0.77 (0.68-0.84) and 0.95 (0.91-0.97), respectively. A policy of initial DUS followed by confirmatory CE-MRA best matches patient selection by arteriography. Single modality imaging for 50% to 69% ICA stenoses suggests reduced reliability resulting in more inappropriate operations.

CONCLUSIONS

DUS is the optimum screening tool due to its sensitivity and specificity, availability, and low cost. When CEA appears indicated, confirmatory imaging with CE-MRA is the most reliable and cost-effective method of investigation.

Assessing cost-effectiveness and value as imaging grows:the case of carotid artery CT

Computed tomographic (CT) angiography is an imaging test that is safer and less expensive than an older test in diagnosing narrowing of the carotid arteries-the most common cause of stroke in US adults. Our examination of Medicare data between 2001 and 2005 found that about 20 percent of the time this test was used, it substituted for the older test. The majority of new use, however, constituted "incremental" use, in cases where patients previously would not have received any test. We found no evidence that the growth in CT angiography led to more patients' being treated for carotid artery disease. The value of the test as a substitute for the older procedure may be enough to still justify expanding use. Tracking the uses of emerging technologies to encourage efficient use is essential, but it can be challenging in cases where new tools have multiple uses and information is incomplete.

[Ocular ischemic syndrome]

Ocular ischemic syndrome (OIS) is a group of ocular diseases caused by chronic artery occlusion usually involving the internal carotid artery. Patients suffer from visual loss and pain. OIS is a rare disease which can be confounded with diabetic retinopathy or an older central retinal vein occlusion. The only therapy is to treat the neovascular complications. Due to the high mortality of OIS patients, medical and neurological examinations are mandatory. We discuss the clinical findings and diagnostic and therapeutic options of OIS patients in this paper.

Whole-body magnetic resonance angiography for presurgical planning of free-flap head and neck reconstruction

OBJECTIVES

Aim of the study was to evaluate if a whole-body magnetic resonance angiography (MRA) protocol meets the requirements to evaluate the donor and host site target vessels for planning of microvascular head and neck reconstructions.

PATIENTS AND METHODS

In 20 patients, scheduled for reconstruction of the mandible with fibular free flaps, contrast-enhanced whole-body MRA was performed prior to surgery. 32-Channel 1.5-T MR angiograms were acquired using a 2-step contrast (gadobutrol) injection scheme to visualize the arterial vasculature from head to feet. Maximum intensity projection and multiplanar reconstruction technique was employed to visualize MRA data. For image evaluation the arterial tree was divided into 51 segments. The presence of artefacts impairing diagnostic quality was noted. Evaluable segments were assessed regarding the presence of stenoses >50% diameter reduction, occlusions or aneurysms.

RESULTS

No adverse reactions or complications occurred. Of 1020 vessel segments 1003 (98.3%) were evaluable. 36 stenoses >50%, 50 occlusions and one aneurysm were observed. In 21 of 40 lower limbs relevant atherosclerotic changes were depicted.

CONCLUSION

Whole-body MRA proved to be a suitable three-dimensional, noninvasive, nonionising modality for preoperative evaluation of the entire arterial vasculature.

[Diagnostic dilemmas of multislice CT angiography in the evaluation of the degree of common carotid artery stenosis]

INTRODUCTION

Multislice CT angiography (CTA) is a noninvasive and quick technique to image carotid artery stenosis, as well as intracerebral vasculature. Modern multidetector CTA produces images with a high resolution of, not only the contrast-filled lumen, but also of the vessel wall and the surrounding soft tissues. Multiple studies have verified the ability of CTA to provide an accurate representation of the degree of carotid stenosis in comparison to digital subtraction angiography, both for moderate and high-grade stenosis. Because of its fast and accurate vessel imaging, CT angiography is increasingly used in the assessment of carotid artery stenosis.

CASE OUTLINE

A 37-year-old female patient was admitted at the Vascular Surgery Clinic of the Institute for Cardiovascular Diseases "Dedinje", Belgrade, for angiography and endovascular procedure of a high-grade stenosis of the left common carotid artery based on Multislice CT findings brought by the patient. She complained of problems which we considered to be the result of cerebral circulation ischemia. After detailed diagnostic procedures, we concluded that no pathological lesions could be verified either on the left common carotid artery or other supraaortic branches.Therefore, the patient was discharged for further neurological examinations.

CONCLUSION

Although Multislice CTA has many advantages over classical angiography, its validity should be taken with reserve, especially in younger patients.

Carotid Artery Imaging for Secondary Stroke Prevention

Background and Purpose— Patients with transient ischemic attack require carotid imaging to diagnose carotid stenosis. The differing sensitivity/specificity and availability of carotid imaging methods have created uncertainty over which noninvasive method is best and whether intra-arterial angiography is still required. We evaluated the influence of carotid imaging methods on secondary stroke prevention.

Methods— We modeled the effect of different carotid imaging strategies and timing on endarterectomy workload, stroke, and death at 1 and 5 years. We used all available data on stroke prevention after transient ischemic attack from systematic reviews (carotid imaging, medical and surgical interventions), population-based transient ischemic attack/stroke studies, government statistics, and stroke prevention clinics.

Results— Choice of imaging strategy affected speed of assessment, strokes prevented, and endarterectomy workload. The number of strokes prevented at 5 years varied by up to 22 per 1000 patients between imaging strategies for a given time to assessment. Delaying endarterectomy from 14 to approximately 30 days would fail to prevent up to 11 strokes per 1000 patients depending on the imaging strategy. Sensitive fast imaging (eg, ultrasound) was best for patients seen early; specific imaging (eg, CT angiography or contrast-enhanced MR angiography) was best for patients seen late after transient ischemic attack. Intra-arterial angiography conferred no advantage over noninvasive imaging.

Conclusions— Rapid access to sensitive noninvasive carotid imaging prevents most strokes. However, imaging strategies differ in their effect on stroke prevention by as much as 22 per 1000 patients and optimal imaging varies with time after transient ischemic attack TIA. Routine intra-arterial angiography should be avoided.