Three-dimensional computed tomography angiography and magnetic resonance angiography of carotid bifurcation stenosis

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included studies and other relevant publications and contacted experts in the field to identify additional studies or unpublished data.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.

A Reappraisal of CT Angiography Derived Duplex Ultrasound Velocity Criteria With a Comparison to Digital Subtraction Angiography in Patients With Carotid Artery Stenosis

BACKGROUND

Traditionally, carotid duplex ultrasound (CDUS) velocity criteria have been derived from angiography. Recent studies support a shift toward computed tomography angiography (CTA) derived velocity criteria; however, they lack a comparison to angiography. The purposes of this study are to validate CTA derived measurements with digital subtraction angiography (DSA) and to update our previous CTA-derived velocity criteria for 50% and 80% stenosis.

METHODS

All patients between 2010 and 2019 who underwent CDUS and a neck CTA within 6 months were identified for a retrospective review. Vessel diameter and corresponding CDUS data were recorded. Additional DSA measurements were recorded for a subset of patients. Data from this cohort were added to a previously reported deidentified data set from patients between 2000 and 2009. Receiver operating characteristic (ROC) curves were generated to determine optimal velocity thresholds. Spearman rank correlation was used to correlate measurements obtained by CTA to those obtained by DSA.

RESULTS

A total of 1139 vessels from 636 patients were analyzed. ROC analysis to identify ≥ 50% stenosis resulted in optimized thresholds of 143 cm/sec, 46.2 cm/sec, and 2.15 for peak systolic velocity (PSV), end-diastolic velocity (EDV), and PSV to common carotid artery PSV ratio (PSVR), respectively. ROC analysis to identify ≥ 80% stenosis resulted in optimized thresholds of 319 cm/sec, 87.2 cm/sec, and 3.49 for PSV, EDV, and PSVR, respectively. The degree of carotid artery stenosis for a subset of 124 vessels on CTA correlated well with that of DSA (ρ = 0.89, P< 0.0001).

CONCLUSIONS

These data demonstrate a high correlation between measurements obtained on CTA and DSA while forming reliable CTA-derived CDUS velocity criteria.

Carotid Artery Imaging in the United Kingdom: A Postal Questionnaire of Current Practice

There has been a steady rise in the use of carotid duplex imaging in the selection of patients for carotid endarterectomy (CEA). Some would suggest that CEA could be safely performed without preoperative contrast angiography. The purpose of this study was to focus on the role of duplex imaging among vascular surgeons in the United Kingdom and to highlight current practices in imaging prior to CEA. A postal questionnaire was sent to all consultant members of the Vascular Surgical Society of Great Britain and Ireland about the choice of imaging prior to selection of patients for CEA, preoperative imaging, and choice of imaging (if any) in the confirmation of carotid occlusion indicated by duplex scanning. Of 396 questionnaires sent, 323 (82%) were returned. Of these, 259 (80%) consultants performed carotid surgery, 118 (45%) in university hospitals (UHs) and 141 (53%) in district general hospitals (DGHs). One hundred eighteen (100%) and 137 (97%) respondents, respectively, chose duplex scanning as their first-line investigation. Sixty (51%) respondents in UHs and 49 (35%) respondents in DGHs repeated duplex scanning immediately preoperatively, with 57 (95%) and 46 (94%), respectively, using duplex scanning. Forty-seven (40%) respondents in UHs and 78 (55%) respondents in DGHs would reconfirm an occlusion, with 30 (64%) and 48 (62%), respectively, using computed tomography and magnetic resonance imaging as their preferred tool. Our study shows that duplex scanning is the first-line imaging technique for patient selection for CEA by vascular surgeons in the United Kingdom. Magnetic resonance imaging and computed tomography are replacing conventional angiography where duplex scanning is equivocal.

Correlation between ABCD, ABCD2 scores and craniocervical artery stenosis in patients with transient ischemic attack

BACKGROUND AND PURPOSE

Craniocervical artery stenosis is an important etiology for transient ischemic attack (TIA). We hypothesized ABCD and ABCD2 scores can predict craniocervical artery stenosis in patients with TIA.

METHODS

ABCD and ABCD2 scores were calculated in a total of 479 consecutive first-ever TIA patients in Nanjing Stroke Registry Program and compared with angiographic imaging derived from MRI or invasive catheter-based angiography.

RESULTS

Overall craniocervical artery (O-CA) stenosis was found in 197 (41.1%) patients. Extracranial craniocervical artery (E-CA) and intracranial craniocervical artery (I-CA) stenosis was found in 101 (21.1%) and 110 (23%) cases, respectively. ABCD and ABCD2 scores with similar accuracy for O-CA (AUCABCD 0.71, AUCABCD2 0.70), E-CA (AUCABCD 0.72, AUCABCD2 0.72) and I-CA stenosis (AUCABCD 0.62, AUCABCD2 0.62) were both independent predictors for various categories of artery stenosis after being adjusted for non-ABCD2 parameters. The cut-off points were equally 4 in both predicting rules. For ABCD, sensitivity was 57.4, 65.3 and 52.7% and specificity 77.0, 70.4 and 67.5% for O-CA/E-CA/I-CA, respectively. For ABCD2, sensitivity was 61.9, 69.3 and 58.2% and specificity 72.3, 65.6 and 63.1%.

CONCLUSIONS

In patients with TIA, despite an association between ABCD and ABCD2 scores and underlying craniocervical artery stenosis, the clinical utility was limited by unsatisfactory sensitivity and specificity.

Evaluation framework for carotid bifurcation lumen segmentation and stenosis grading

This paper describes an evaluation framework that allows a standardized and objective quantitative comparison of carotid artery lumen segmentation and stenosis grading algorithms. We describe the data repository comprising 56 multi-center, multi-vendor CTA datasets, their acquisition, the creation of the reference standard and the evaluation measures. This framework has been introduced at the MICCAI 2009 workshop 3D Segmentation in the Clinic: A Grand Challenge III, and we compare the results of eight teams that participated. These results show that automated segmentation of the vessel lumen is possible with a precision that is comparable to manual annotation. The framework is open for new submissions through the website http://cls2009.bigr.nl.

Dual-energy CTA with bone removal for transcranial arteries: intraindividual comparison with standard CTA without bone removal and TOF-MRA

RATIONALE AND OBJECTIVES

Dual-source computed tomography enables bone removal on computed tomographic angiographic data on the basis of simultaneous dual-energy (DE) acquisition. The aim of this study was to evaluate the impact of this technique for the assessment of transcranial arteries. Therefore, the degree of stenosis of the transcranial arteries on DE computed tomographic angiography (CTA) with bone removal was compared to those on standard CTA and time-of-flight (TOF) magnetic resonance angiography (MRA).

MATERIALS AND METHODS

DE-CTA was performed using a dual-source computed tomographic scanner in 50 patients with suspected cerebrovascular disease. From the source images on DE-CTA, data sets with and without bone removal were reconstructed. TOF-MRA was performed on a 1.5-T scanner. Two blinded radiologists evaluated the segments of the internal carotid artery (C2-C7), the vertebral artery (V4), and the basilar artery for degree of stenosis. A five-step scale (0%-49%, 50%-69%, 70%-89%, 90%-99%, and 100% [occlusion]) for degree of stenosis was applied. Wilcoxon's signed-rank test was used for statistical analysis.

RESULTS

The degrees of stenosis on standard CTA were consistent with those on TOF-MRA in all segments. In contrast, DE-CTA showed significantly higher degrees of stenosis compared to standard CTA and TOF-MRA in both C2 segments (P < .001). In addition, DE-CTA revealed a significantly higher degree of stenosis compared to standard CTA and TOF-MRA in the left C4 segment (P < .01 and P < .005, respectively). All other segments showed no significant differences of stenosis among TOF-MRA, DE-CTA, and standard CTA.

CONCLUSIONS

Compared to TOF-MRA, standard CTA showed similar results. In contrast, DE-CTA revealed significant overestimation of stenosis for segments with close relations to bony structures as well as in calcified stenosis. Consequently, such findings on DE-CTA require confirmation with standard CTA or MRA to eliminate false-positive results.

3D-3D tubular organs registration based on bifurcations for the CT images

The registration of tubular organs (pulmonary tracheobronchial tree or vasculature) of 3D medical images is critical in various clinical applications such as surgical planning and radiotherapy. In this paper, we present a novel method for tubular organs registration based on the automatically detected bifurcation points of the tubular organs. We first perform a 3D tubular organ segmentation method to extract the centerlines of tubular organs and radius estimation in both planning and respiration-correlated CT (RCCT) images. This segmentation method automatically detects the bifurcation points by applying Adaboost algorithm with specially designed filters. We then apply a rigid registration method which minimizes the least square error of the corresponding bifurcation points between the planning CT images and the respiration-correlated CT images. Our method has over 96% success rate for detecting bifurcation points.We present very promising results of our method applied to the registration of the planning and respiration-correlated CT images. On average, the mean distance and the root-mean-square error (RMSE) of the corresponding bifurcation points between the respiration-correlated images and the registered planning images are less than 2.7 mm.

Carotid bifurcation calcium and correlation with percent stenosis of the internal carotid artery on CT angiography

The aim of this paper was to determine the correlation between calcium burden (expressed as a volume) and extent of stenosis of the origin of the internal carotid artery (ICA) by CT angiography (CTA). Previous studies have shown that calcification in the coronary arteries correlates with significant vessel stenosis, and severe calcification (measured by CT) in the carotid siphon correlates with significant (greater than 50% stenosis) as determined angiographically. Sixty-one patients (age range 50-85 years) underwent CT of the neck with intravenous administration of iodinated contrast for a variety of conditions. Images were obtained with a helical multidetector array CT scanner and reviewed on a three-dimensional workstation. A single observer manipulated window and level to segment calcified plaque from vascular enhancement in order to quantify vascular calcium volume (cc) in the region of the bifurcation of the common carotid artery/ICA origin, and to measure the extent of ICA stenosis near the origin. A total of 117 common carotid artery bifurcations were reviewed. A "significant" stenosis was defined arbitrarily as >40% (to detect lesions before they become hemodynamically significant) of luminal diameter on CTA using NASCET-like criteria. All "significant" stenoses (21 out of 117 carotid bifurcations) had measurable calcium. We found a relatively strong correlation between percent stenosis and the calcium volume (Pearson's r = 0.65, P<0.0001). We also found that there was an even stronger correlation between the square root of the calcium volume and the percent stenosis as measured by CTA (r= 0.77, P<0.0001). Calcium volumes of 0.01, 0.03, 0.06, 0.09 and 0.12 cc were used as thresholds to evaluate for a "significant" stenosis. A receiver operating characteristic (ROC) curve demonstrated that thresholds of 0.06 cc (sensitivity 88%, specificity 87%) and 0.03 cc (sensitivity 94%, specificity 76%) generated the best combinations of sensitivity and specificity. Hence, this preliminary study demonstrates a relatively strong relationship between volume of calcium at the carotid bifurcation in the neck (measured by CT) and percent stenosis of the ICA below the skull base (as measured by CTA). Use of calcium volume measurements as a threshold may be both sensitive and specific for the detection of significant ICA stenosis. The significance of the correlation between calcium volume and ICA stenosis is that potentially a "score" can be obtained that will identify those at risk for high grade carotid stenosis.

Comparison of ultrasonography, CT angiography, and digital subtraction angiography in severe carotid stenoses

Digital subtraction angiography (DSA) is considered to be the 'gold standard' for confirmation of severe (70-99%) stenoses of internal carotid arteries (ICAs). However, it is associated with a risk of complications. The aim of this study was to assess the accuracy of ultrasonography (US), computed tomographic angiography (CTA), and their combined use for the detection and quantification of severe carotid stenoses, when compared with DSA. Severe ICA stenoses were diagnosed by US in a set of 29 patients. All patients also underwent CTA and DSA. Sensitivity, specificity, positive (PPV), negative predictive values (NPV), and Pearson's correlation coefficient were used in the evaluation of the percentage of stenosis results. Homogeneity chi2 test was applied when assessing statistical significance. Severe stenosis was diagnosed in 34 ICAs. Two ICAs with uninterpretable CTA finding were excluded. The number of ICAs with stenoses 70-99%/<70%- US 32/0; CTA 29/3; US + CTA 29/3; DSA 24/8. Pearson's correlation coefficient - US 0.601; CTA 0.725; US + CTA 0.773. Sensitivity/specificity/PPV/NPV - US 1.0/0.75/0.75/xxx; CTA 1.0/0.844/0.828/1.0; US + CTA 1.0/0.844/0.828/1.0. Homogeneity chi2 test results - US, P = 0.002; CTA, P = 0.098; US + CTAG, P = 0.098. US in combination with CTA can be used for relatively secure diagnostics of severe ICA stenoses. Thus, invasive DSA can be avoided in a substantial number of patients.

Systematic Review of Computed Tomographic Angiography for Assessment of Carotid Artery Disease

Background and Purpose— To review the literature on the diagnostic accuracy of computed tomographic angiography (CTA) compared with arteriography/intra-arterial digital subtraction angiography as reference standard for assessment of symptomatic carotid artery disease.

Methods— The PubMed, MEDLINE, PREMEDLINE, EMBASE, and CINAHL databases were searched to retrieve studies published between 1990 and July 2003, comparing CTA and intra-arterial digital subtraction angiography in patients with symptomatic carotid artery disease that presented raw data for detection of a <70% or 70% to 99% stenosis or an occlusion. Two observers independently assessed methodological quality and constructed 2×2 tables for sensitivity and specificity of CTA for detection of a 70% to 99% stenosis versus <70% stenosis or an occlusion, and for <99% stenosis versus occlusion. A bivariate random effects model was used to calculate the pooled sensitivity and specificity of CTA for detection of these lesions.

Results— Some 864 patients (66% male) with a mean age of 66 years were studied in the 28 studies included in the meta-analysis. In all studies, a single-slice CT-scan was used. Only 8 studies satisfied all methodological quality criteria. The pooled sensitivity and specificity for detection of a 70% to 99% stenosis were 85% (95% CI, 79% to 89%) and 93% (95% CI, 89% to 96%), respectively. For detection of an occlusion, the sensitivity and specificity were 97% (95% CI, 93% to 99%) and 99% (95% CI, 98% to 100%), respectively. Incomplete reporting of demographic characteristics and technical differences in the individual studies obstructed a meaningful subgroup analysis.

Conclusions— CTA is an accurate modality for detection of severe carotid artery disease, especially for detection of occlusions. The fair methodological quality of the included studies must be taken into account when interpreting these results.

The diagnostic accuracy of computed tomography angiography for traumatic or atherosclerotic lesions of the carotid and vertebral arteries: a systematic review

INTRODUCTION

Helical computed tomography angiography (CTA) has become an established technique for evaluating atherosclerosis of the cerebrovascular arteries. However, the role of CTA in penetrating and blunt trauma to the carotid and vertebral arteries is not well defined. We conducted a systematic literature review to determine the diagnostic accuracy of CTA for atherosclerotic, penetrating and blunt lesions in the carotid and vertebral arteries.

METHODS

We searched MEDLINE and EMBASE databases to identify studies evaluating the diagnostic accuracy of CTA of the carotid and vertebral arteries published between January 1, 1992 and December 31, 2002. Two reviewers independently assessed abstracts and full text to determine study eligibility. Information on methodological quality, imaging technique and diagnostic accuracy was abstracted from all eligible studies by three independent reviewers. We pooled sensitivity and specificity data from diagnostic accuracy studies of high methodological quality.

RESULTS

Forty-three articles met the inclusion criteria and were included in the review. Thirty studies examined atherosclerotic disease, two blunt trauma, two penetrating trauma and nine examined patients with other pathology. Pooled data from 15 higher quality studies demonstrated that CTA had a sensitivity of 95% (91-97% CI) for detecting severe (>70%) atherosclerotic stenosis of the carotid artery. The specificity of CTA for severe stenosis was also high 98% (96-99% CI). CTA remained a sensitive technique (95%; 93-97% CI) when the criterion for a positive result is relaxed to moderate or greater (>30%) stenosis. Two studies raised concerns about the use of CTA in the blunt trauma setting, suggesting that CTA may not be sensitive for detecting small intimal injuries, although both of these studies used older technologies for either obtaining or viewing images. Conversely, two penetrating trauma studies concluded that the sensitivity of CTA was high.

CONCLUSIONS

Our findings demonstrate that CTA is both a sensitive and specific imaging technique for identifying severe atherosclerotic stenosis and occlusion of the carotid arteries. However, there is currently not enough high quality evidence to accurately estimate the sensitivity and specificity of CTA in the setting of blunt or penetrating trauma.

Duplex ultrasound and magnetic resonance angiography compared with digital subtraction angiography in carotid artery stenosis: a systematic review

BACKGROUND AND PURPOSE

The purpose of this work was to review and compare published data on the diagnostic value of duplex ultrasonography (DUS), MR angiography (MRA), and conventional digital subtraction angiography (DSA) for the diagnosis of carotid artery stenosis.

METHODS

We performed a systematic review of published studies retrieved through PUBMED, from bibliographies of review papers, and from experts. The English-language medical literature was searched for studies that met the selection criteria: (1) The study was published between 1994 and 2001; (2) MRA and/or DUS was performed to estimate the severity of carotid artery stenosis; (3) DSA was used as the standard of reference; and (4) the absolute numbers of true positives, false negatives, true negatives, and false positives were available or derivable for at least one definition of disease (degree of stenosis).

RESULTS

Sixty-three publications on duplex, MRA, or both were included in the analysis, yielding the test results of 64 different patient series on DUS and 21 on MRA. For the diagnosis of 70% to 99% versus <70% stenosis, MRA had a pooled sensitivity of 95% (95% CI, 92 to 97) and a pooled specificity of 90% (95% CI, 86 to 93). These numbers were 86% (95% CI, 84 to 89) and 87% (95% CI, 84 to 90) for DUS, respectively. For recognizing occlusion, MRA yielded a sensitivity of 98% (95% CI, 94 to 100) and a specificity of 100% (95% CI, 99 to 100), and DUS had a sensitivity of 96% (95% CI, 94 to 98) and a specificity of 100% (95% CI, 99 to 100). A multivariable summary receiver-operating characteristic curve (ROC) analysis for diagnosing 70% to 99% stenosis demonstrated that the type of MR scanner predicted the performance of MRA, whereas the presence of verification bias predicted the performance of DUS. For diagnosing occlusion, no significant heterogeneity was found for MRA; for DUS, the presence of verification bias and type of DUS scanner were explanatory variables. MRA had a significantly better discriminatory power than DUS in diagnosing 70% to 99% stenosis (regression coefficient, 1.6; 95% CI, 0.37 to 2.77). No significant difference was found in detecting occlusion (regression coefficient, 0.73; 95% CI, -2.06 to 3.51).

CONCLUSIONS

These results suggest that MRA has a better discriminatory power compared with DUS in diagnosing 70% to 99% stenosis and is a sensitive and specific test compared with DSA in the evaluation of carotid artery stenosis. For detecting occlusion, both DUS and MRA are very accurate.

Pulmonary vein anatomy in patients undergoing catheter ablation of atrial fibrillation: lessons learned by use of magnetic resonance imaging

BACKGROUND

This study sought to define the technique and results of magnetic resonance imaging (MRI) of pulmonary vein (PV) anatomy before and after catheter ablation of atrial fibrillation (AF).

METHODS AND RESULTS

Twenty-eight patients with AF underwent ablation. Patients underwent gadolinium-enhanced MRI before and 6 weeks after their procedures. A control group of 27 patients also underwent MRI. Variant PV anatomy was observed in 38% of patients. AF patients had larger PV diameters than control subjects, but no difference was observed in the size of the PV ostia among AF patients. The PV ostia were oblong in shape with an anteroposterior dimension less than the superoinferior dimension. The left PVs had a longer "neck" than the right PVs. A detectable PV narrowing was observed in 24% of veins. The severity of stenosis was severe in 1 vein (1.4%), moderate in 1 vein (1.4%), and mild in 15 veins (21.1%). All patients were asymptomatic, and none required treatment.

CONCLUSIONS

This study demonstrates that AF patient have larger PVs than control subjects and demonstrates the value of MRI in facilitating AF ablation. The benefits of preprocedural MRI of PVs include the ability to evaluate the number, size, and shape of the PVs. MRI also provides an assessment of the severity of PV stenosis.

Utility of noninvasive studies in the evaluation of patients with carotid artery disease

Endarterectomy reduces the risk of stroke in selected patients with carotid artery stenosis, and the benefit is related to the degree of stenosis. Although the randomized trials demonstrating this benefit measured the degree of stenosis with conventional catheter angiography, many physicians are relying on noninvasive tests to select patients for surgery. Technologic advancement in this area is outpacing the availability of quality data supporting the clinical utility of the newer noninvasive tests.