Aortic Atherosclerotic Disease and Stroke

Relation of aortic arch complex plaques to risk of cerebral infarction in patients with aortic stenosis

Aortic stenosis (AS) and systemic atherosclerosis have been shown to be closely related. We evaluated the prevalence of aortic arch plaques and their possible association with the risk of cerebral infarction in patients with severe AS. Transesophageal echocardiography was performed in 116 patients with severe AS (55 men, mean age 71 ± 7 years, mean aortic valve area 0.68 ± 0.15 cm(2)) who were scheduled for aortic valve replacement. The presence, thickness, and morphology of the aortic arch plaques were evaluated using transesophageal echocardiography. Cerebral infarcts (chronic cerebral infarction and cerebral infarction after cardiac catheterization and aortic valve replacement) were assessed in all patients. Compared to age- and gender-matched control subjects, the patients with severe AS had a significantly greater prevalence of aortic arch plaques (74% vs 41%; p <0.0001) and complex arch plaques such as large plaques (≥4 mm), ulcerated plaques, or mobile plaques (30% vs 10%; p = 0.004). Multivariate logistic analyses showed that the presence of complex arch plaques was independently associated with cerebral infarction in patients with AS after adjusting for traditional atherosclerotic risk factors and coronary artery disease (odds ratio 8.46, 95% confidence interval 2.38 to 30.12; p = 0.001). In conclusion, the results from the present study showed that there is a greater prevalence of aortic arch plaques in patients with AS and that the presence of complex plaques is independently associated with cerebral infarction in these patients. Therefore, the identification of complex arch plaques using transesophageal echocardiography is important for risk stratification of cerebrovascular events in patients with severe AS.

Right–Left Propensity and Lesion Patterns Between Cardiogenic and Aortogenic Cerebral Embolisms

Background and Purpose—

Based on thrombus location and nature and anatomic features of aorta and cerebral arteries, we hypothesized that cardiogenic embolisms (CE) and aortogenic embolisms (AE) might have different right–left propensity and lesion patterns.

Methods—

We retrospectively reviewed patients with acute ischemic stroke with high-risk CE sources or moderate-or-severe aortic atherosclerotic plaques on transesophageal echocardiography. Lesion side and patterns on diffusion-weighted imaging were compared between CE and AE.

Results—

CE was identified in 123 and AE in 63. In multivariate analysis, right-sided lesions and corticosubcortical infarcts were independently associated with CE, and left-sided lesions and pial infarcts were independently associated with AE.

Conclusions—

CE and AE have different radiological characteristics, as shown by the right–left propensity and lesions patterns of cerebral infarcts.

Guidelines for the primary prevention of stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association

BACKGROUND AND PURPOSE

This guideline provides an overview of the evidence on established and emerging risk factors for stroke to provide evidence-based recommendations for the reduction of risk of a first stroke.

METHODS

Writing group members were nominated by the committee chair on the basis of their previous work in relevant topic areas and were approved by the American Heart Association (AHA) Stroke Council Scientific Statement Oversight Committee and the AHA Manuscript Oversight Committee. The writing group used systematic literature reviews (covering the time since the last review was published in 2006 up to April 2009), reference to previously published guidelines, personal files, and expert opinion to summarize existing evidence, indicate gaps in current knowledge, and when appropriate, formulate recommendations using standard AHA criteria (Tables 1 and 2). All members of the writing group had the opportunity to comment on the recommendations and approved the final version of this document. The guideline underwent extensive peer review by the Stroke Council leadership and the AHA scientific statements oversight committees before consideration and approval by the AHA Science Advisory and Coordinating Committee.

RESULTS

Schemes for assessing a person's risk of a first stroke were evaluated. Risk factors or risk markers for a first stroke were classified according to potential for modification (nonmodifiable, modifiable, or potentially modifiable) and strength of evidence (well documented or less well documented). Nonmodifiable risk factors include age, sex, low birth weight, race/ethnicity, and genetic predisposition. Well-documented and modifiable risk factors include hypertension, exposure to cigarette smoke, diabetes, atrial fibrillation and certain other cardiac conditions, dyslipidemia, carotid artery stenosis, sickle cell disease, postmenopausal hormone therapy, poor diet, physical inactivity, and obesity and body fat distribution. Less well-documented or potentially modifiable risk factors include the metabolic syndrome, excessive alcohol consumption, drug abuse, use of oral contraceptives, sleep-disordered breathing, migraine, hyperhomocysteinemia, elevated lipoprotein(a), hypercoagulability, inflammation, and infection. Data on the use of aspirin for primary stroke prevention are reviewed.

CONCLUSIONS

Extensive evidence identifies a variety of specific factors that increase the risk of a first stroke and that provide strategies for reducing that risk.

MR-based visualization and quantification of three-dimensional flow characteristics in the portal venous system

PURPOSE

To evaluate the feasibility of time-resolved flow-sensitive MRI for the three-dimensional (3D) visualization and quantification of normal and pathological portal venous (PV) hemodynamics.

MATERIALS AND METHODS

Portal venous hemodynamics were evaluated in 18 healthy volunteers and 5 patients with liver cirrhosis. ECG- and adaptive respiratory navigator gated flow-sensitive 4D MRI (time-resolved 3D MRI with three-directional velocity encoding) was performed on a 3 Tesla MR system (TRIO, Siemens, Germany). Qualitative flow analysis was achieved using 3D streamlines and time-resolved particle traces originating from seven emitter planes precisely placed at anatomical landmarks in the PV system. Quantitative analysis included retrospective extraction of regional peak and mean velocities and vessel area. Results were compared with standard 2D flow-sensitive MRI and to the reference standard Doppler ultrasound.

RESULTS

Qualitative flow analysis was successfully used in the entire PV system. Venous hemodynamics in all major branches in 17 of 18 volunteers and 3 of 5 patients were reliably depicted with good interobserver agreement (kappa = 0.62). Quantitative analysis revealed no significant differences and moderate agreement for peak velocities between 3D MR and 2D MRI (r = 0.46) and Doppler ultrasound (US) (r = 0.35) and for mean velocities between 3D and 2D MRI (r = 0.41). The PV area was significantly (P < 0.01) higher in 3D and 2D MRI compared with US.

CONCLUSION

We successfully applied 3D MR velocity mapping in the PV system, providing a detailed qualitative and quantitative analysis of normal and pathological hemodynamics.

The correlation between carotid siphon calcification and lacunar infarction

INTRODUCTION

The aim of this study was to evaluate the correlation between carotid siphon (CS) calcification and lacunar infarction caused by small-vessel disease.

METHODS

This retrospective study included 445 patients (M/F = 256:189) older than 40 years (mean age 60.0 ± 12.3 years, range 41-98 years) without large intracranial lesions who had undergone both brain CT and MRI within an interval of 6 months. The patients were classified into three groups according to the number of lacunar infarctions: group I-zero infarctions (n = 328), group II-one to three infarctions (n = 94), and group III-four or more infarctions (n = 23). The severity of CS calcification was evaluated on CT and scored on a five-point scale (0-none, 1-stippled, 2-thin continuous or thick discontinuous, 3-thick continuous, 4-double tracts), and the calcification scores on both sides were summed. An ANOVA test was used to compare calcification scores among the three groups, and a logistic regression test was used to evaluate the influence of CS calcification and known cerebrovascular risk factors on the occurrence of lacunar infarction.

RESULTS

On the ANOVA test, total calcification scores were significantly different among the three groups (group I = 1.28 ± 1.99, group II = 3.31 ± 2.39, group III = 4.36 ± 2.08; P < 0.05). Higher rates of lacunar infarction were associated with higher CS calcification scores. On the logistic regression test, CS calcification, age, and hypertension were significant risk factors for lacunar infarction (P < 0.05).

CONCLUSION

CS calcification was correlated with the occurrence of lacunar infarction. The degree of CS calcification may be used to predict the possibility of a future lacunar infarction.

Estimation of global aortic pulse wave velocity by flow-sensitive 4D MRI

The aim of this study was to determine the value of flow-sensitive four-dimensional MRI for the assessment of pulse wave velocity as a measure of vessel compliance in the thoracic aorta. Findings in 12 young healthy volunteers were compared with those in 25 stroke patients with aortic atherosclerosis and an age-matched normal control group (n = 9). Results from pulse wave velocity calculations incorporated velocity data from the entire aorta and were compared to those of standard methods based on flow waveforms at only two specific anatomic landmarks. Global aortic pulse wave velocity was higher in patients with atherosclerosis (7.03 +/- 0.24 m/sec) compared to age-matched controls (6.40 +/- 0.32 m/sec). Both were significantly (P < 0.001) increased compared to younger volunteers (4.39 +/- 0.32 m/sec). Global aortic pulse wave velocity in young volunteers was in good agreement with previously reported MRI studies and catheter measurements. Estimation of measurement inaccuracies and error propagation analysis demonstrated only minor uncertainties in measured flow waveforms and moderate relative errors below 16% for aortic compliance in all 46 subjects. These results demonstrate the feasibility of pulse wave velocity calculation based on four-dimensional MRI data by exploiting its full volumetric coverage, which may also be an advantage over standard two-dimensional techniques in the often-distorted route of the aorta in patients with atherosclerosis.

Aortic atheroma and adverse cerebral outcome: risk, diagnosis, and management options

Aortic atheromatous disease is a common finding in the patient presenting for cardiac surgery. Adverse neurologic outcome has been closely linked to the extent of aortic atherosclerosis. In order to optimize perioperative outcomes, the location and severity of disease needs accurate characterization using multimodal techniques. Although various preoperative radiographic techniques have variably identified patients with significant atheroma, intraoperative echocardiographic imaging has proven most useful in localizing and characterizing the degree of aortic atheroma. Epiaortic assessment of the ascending aorta has been utilized in guiding surgical modifications and interventions aimed at reducing the risk of neurologic injury. Although no particular technique has been definitely studied, avoidance of the identifiable atheromatous aortic region has been a main feature of the various modifications employed to optimize neurologic outcome after cardiac surgery.

Carotid, aortic arch and coronary calcification are related to history of stroke: the Rotterdam Study

OBJECTIVE

Multidetector computed tomography (MDCT), which has been mainly used to study coronary atherosclerosis, also enables non-invasive measurement of carotid and aortic atherosclerosis and might be suitable for screening in the general population. The aim of this study was to investigate the associations of carotid artery, aortic arch and coronary artery calcification as assessed by MDCT, with presence of stroke.

METHODS

The study was embedded in the population-based Rotterdam Study and comprises 2521 persons (mean age 69.7±6.8 years, 48% males) that underwent an MDCT scan. History of stroke was reported by 96 persons. We used multivariable logistic regression to investigate the associations of calcification in the carotid arteries, aortic arch, and coronary arteries with presence of stroke.

RESULTS

We found strong and graded associations of prevalent stroke with carotid artery (OR quartile 4 versus 1 (95% CI): 5.0 (2.2-11.0)), aortic arch (3.3 (1.5-7.4)) and coronary artery calcification (3.1 (1.3-7.3)), independent of cardiovascular risk factors. Only the association of carotid artery calcification with presence of stroke was independent of calcification in the other two vessel beds.

CONCLUSION

In this population-based study, we found a strong and graded association of prevalent stroke with carotid artery, aortic arch and coronary artery calcification, independent of cardiovascular risk factors. After additional adjustment for calcification in the other vessel beds, prevalent stroke was still significantly related to carotid calcification, but no longer to aortic arch or coronary calcification.

Complex Plaques in the Proximal Descending Aorta

Background and Purpose— To investigate the incidence of retrograde flow from complex plaques (≥4-mm-thick, ulcerated, or superimposed thrombi) of the descending aorta (DAo) and its potential role in embolic stroke.

Methods— Ninety-four consecutive acute stroke patients with aortic plaques ≥3-mm-thick in transesophageal echocardiography were prospectively included. MRI was performed to localize complex plaques and to measure time-resolved 3-dimensional blood flow within the aorta. Three-dimensional visualization was used to evaluate if diastolic retrograde flow connected plaque location with the outlet of the left subclavian artery, left common carotid artery, or brachiocephalic trunk. Complex DAo plaques were considered an embolic source if retrograde flow reached a supra-aortic vessel that supplied the territory of visible acute and embolic retinal or cerebral infarction.

Results— Only decreasing heart rate was correlated (P <0.02) with increasing flow reversal to the aortic arch. Retrograde flow from complex DAo plaques reached the left subclavian artery in 55 (58.5%), the left common carotid artery in 23 (24.5%), and the brachiocephalic trunk in 13 patients (13.8%). Based on routine diagnostics and MRI of the ascending aorta/aortic arch, stroke etiology was determined in 57 and cryptogenic in 37 patients. Potential embolization from DAo plaques was then identified in 19 of 57 patients (33.3%) with determined and in 9 of 37 patients (24.3%) with cryptogenic stroke.

Conclusions— Retrograde flow from complex DAo plaques was frequent in both determined and cryptogenic stroke and could explain embolism to all brain territories. These findings suggest that complex DAo plaques should be considered a new source of stroke.

The purple digit: an algorithmic approach to diagnosis

The acute onset of purple digits is a concerning manifestation and may represent underlying, potentially life-threatening disease. Correctly identifying the etiology of purple digits is essential to proper management, and can aid in the diagnosis of systemic disease. Multiple causes of purple digits and significant overlap in clinical presentation can make diagnosis difficult. Despite the various causes of acute purple digits in the published literature, an algorithmic approach to the evaluation and management of the most common and alarming etiologies has yet to be established. The initial step in evaluating a patient with purple digits is to determine if the cause is associated with hypoxemia or trauma. If the patient is in a stable condition, the dermatologist needs to determine if the process could be related to cold exposure such as Raynaud phenomenon, acrocyanosis, pernio, cryoglobulinemia or frostbite. If the disease occurs independent of temperature, physical examination and histological evaluation of the skin is recommended. The lack of peripheral pulses are concerning for acute arterial thrombosis from peripheral vascular disease or arterial embolism. Non-blanching skin changes on the digit that lack inflammation and microthrombosis most likely represent a bleeding or platelet abnormality; however, if microthrombi are identified a more life-threatening processes such as purpura fulminans or embolic phenomenon may be occurring. Evidence of blood vessel inflammation suggests a leukocytoclastic vasculitis. The patient with a purple blanching digit and normal pulses requires an extensive historical review to help determine the cause. This review presents an algorithmic approach to assist in the evaluation and management of the purple digit.

Silent and Apparent Cerebral Ischemia After Percutaneous Transfemoral Aortic Valve Implantation

Background— The risk of stroke after transfemoral aortic valve implantation (TAVI) due to dislodgement and subsequent embolization of debris from aortic arch atheroma or from the calcified valve itself ranges between 2% and 10%. The rate of clinically silent cerebral ischemia is unknown but may be even higher.

Methods and Results— Thirty-two patients who underwent TAVI with the use of a balloon-expandable (n=22) or self-expandable (n=10) stent valve prosthesis were included in this descriptive study and compared with a historical control group of 21 patients undergoing open surgical aortic valve replacement. Periprocedural apparent and silent cerebral ischemia was assessed by neurological testing and serial cerebral diffusion-weighted magnetic resonance imaging at baseline, at 3.4 (2.5 to 4.4) days after the procedure, and at 3 months. TAVI was successful in all patients. After the procedure, new foci of restricted diffusion on cerebral diffusion-weighted magnetic resonance imaging were found in 27 of 32 TAVI patients (84%) and were more frequent than after open surgery (10 of 21 patients [48%]; P =0.011). These lesions were usually multiple (1 to 19 per patient) and dispersed in both hemispheres in a pattern suggesting cerebral embolization. Volumes of these lesions were significantly smaller after TAVI than after surgery (77 [59 to 94] versus 224 [111 to 338] mm 3 ; P <0.001). There were neither measurable impairments of neurocognitive function nor apparent neurological events during the in-hospital period among TAVI patients, but there was 1 stroke (5%) in the surgical patient group. On 3-month follow-up diffusion-weighted magnetic resonance imaging, there were no new foci of restricted diffusion, and there was no residual signal change associated with the majority (80%) of the foci detected in the periprocedural period.

Conclusions— Clinically silent new foci of restricted diffusion on cerebral magnetic resonance imaging were detected in almost all patients (84%) undergoing TAVI. Although typically multiple, these foci were not associated with apparent neurological events or measurable deterioration of neurocognitive function during 3-month follow-up. Further work needs to be directed to determine the clinical significance of these findings in a larger patient population.

Development of a catheter for combined intravascular ultrasound and photoacoustic imaging

Atherosclerosis is characterized by formation and development of the plaques in the inner layer of the vessel wall. To detect and characterize atherosclerotic plaques, we previously introduced the combined intravascular ultrasound (IVUS) and intravascular photoacoustic (IVPA) imaging capable of assessing plaque morphology and composition. The utility of IVUS/IVPA imaging has been demonstrated by imaging tissue-mimicking phantoms and ex vivo arterial samples using laboratory prototype of the imaging system. However, the clinical realization of a IVUS/IVPA imaging requires an integrated intravascular imaging catheter. In this paper, two designs of IVUS/IVPA imaging catheters--side fire fiber-based and mirror-based catheters--are reported. A commercially available IVUS imaging catheter was utilized for both pulse-echo ultrasound imaging and detection of photoacoustic transients. Laser pulses were delivered by custom-designed fiber-based optical systems. The optical fiber and IVUS imaging catheter were combined into a single device. Both designs were tested and compared using point targets and tissue-mimicking phantoms. The results indicate applicability of the proposed catheters for clinical use.

[Diagnosing stroke aetiologies. Morphologic and functional analysis of the aorta and carotid arteries by MRI]

Magnetic resonance imaging allows detailed visualization of the thoracic aorta and is not limited by air artefacts or insonation angles like transoesophageal echocardiography (TEE). Thus the aortic arch can be investigated with higher accuracy, and additional embolic high-risk sources such as complex plaques can be additionally detected by MRI in patients with cryptogenic stroke. Furthermore, MRI provides exact 3D plaque localisation and can be combined with multidirectional 3D MRI velocity mapping. In this way, previously not demonstrable retrograde flow paths originating at complex descending aortic plaques reaching the supra-aortic great arteries can be identified as the probable stroke mechanism in certain patients. The same technique can also be applied to the carotid arteries. This allows analysing the complex 3D helical flow within the internal carotid artery as well as measuring absolute flow velocities and wall shear stress in combination with data on vessel anatomy derived from conventional MR angiography. It is the purpose of this work to describe the state of the art of these modern MR imaging techniques and their potential to identify potential stroke mechanisms, and to analyse the particular role of individual haemodynamic factors on the development of local atherosclerosis.

[Cryptogenic cerebral infarction: from classification to concept]

Since the foundations laid by Sacco and Mohr in 1989, from the Stroke data bank, cryptogenic infarctions have had a predominant place among the causes of ischemic strokes. In that study, they accounted for approximately 40% of the stroke causes. Cryptogenic infarctions are infarctions without a defined cause, despite a complete work-up; they differ from infarctions of undetermined causes, which may involve overlapping causes or an incomplete investigation. The size of this group will probably shrink as knowledge advances. Patent foramen ovale (PFO), with or without a septal aneurysm, is more frequent in patients with a cryptogenic infarction. Transesophageal echocardiography is the reference examination for screening for these abnormalities. A meta-analysis of several case-control studies showed a significant association between PFO and stroke in subjects younger than 55 years. For now, these septal abnormalities constitute a risk factor but not a cause. Complex aortic atheroma affecting area upstream of the left subclavian artery may be a source of cerebral embolisms in some conditions. The prevalence of this disease increases with age. It is identified most frequently in patients older than 60 years with a cryptogenic infarction. The thickness of the atheromatous plaque determines whether it is a risk factor or a cause. Recent stroke classifications do not consider carotid atheromatous lesions less than 50% to be a source of ischemic stroke. Nonetheless some studies identify moderate stenosis of the carotid artery more frequently in infarctions of unknown causes than in other categories. The increased risk of cerebral infarction when parents and homozygous twins have a history of stroke suggests that there may be genetic causes that have not yet been detected. An unknown genetic cause would thus be included in the infarctions of unknown causes. A recent study tested for Fabry disease in young patients with a cryptogenic infarction: 4.9% of the men and 2.4% of the women had a functional mutation of the alpha-galactosidase gene. These findings must be confirmed. Some studies suggest an association between cryptogenic infarction and hereditary thrombophilias. Nonetheless the risk attributable to these thrombophilic disorders is slight and the discovery may be only a coincidence. The work described above shows the importance of stratification in the identification of stroke causes: age older or younger than 55/60 years, type of interatrial abnormality (PFO and aneurysms of the interatrial septum), type of atheroma of the aortic arch (more or less than 4mm). They also show the difficulty involved in attributing cause to an identified abnormality: is carotid stenosis of less than 50% a marker of atherosclerosis or also a cause of stroke? To continue improving our understanding of the mechanisms of strokes, new investigational techniques are under evaluation. They include magnetic resonance imaging (MRI), computed tomographic angiography (CT), positron emission tomography (PET) of carotid plaque and of the aortic arch, transcranial Doppler, cardiac recording by telemetry, and even new biological assays.

Amounts of aortic atherosclerosis in patients with aortic stenosis as determined by transesophageal echocardiography

We quantified the graded amounts of aortic atherosclerosis (AA) in patients with aortic stenosis (AS) to better delineate the need for preprocedural risk stratification. Complex AA is strongly related to embolic events, especially during open heart surgery and catheterization. Despite the frequency of these procedures in patients with AS and the increased prevalence of atherosclerosis, current guidelines do not recommend screening for AA. Patients with concomitant transesophageal and transthoracic echocardiograms were retrospectively identified. AS and AA were graded by expert reviewers as mild, moderate, and severe according to established guidelines. Three hundred sixty patients (212 men, mean age 69 +/- 14 years) were identified, 186 (52%) without AS, 82 (23%) with mild AS, 55 (15%) with moderate AS, and 37 (10%) with severe AS. There was a strong graded positive association between AA and AS (p <0.00001). The prevalence of severe AA increased across grades of AS. Of all patients with severe AS, 54% had severe AA. Of patients with severe AS not referred for an embolic event, 57% had severe AA. The odds ratio for severe AA was 4.9 (95% confidence interval 2.3 to 10.3) in patients with severe AS compared with without AS. In conclusion, AS and AA are closely correlated. The majority of patients with severe AS have severe AA, even without previous thromboembolic events. This significant atherosclerotic burden may warrant preprocedural risk assessment with transesophageal echocardiography.

Graft replacement for massive mobile embolic source in brachiocephalic artery

A 76-year-old woman presented with multiple brain infarctions in the right middle cerebral artery and vertebral artery area. Carotid sonography revealed a large mobile pedunculated mass in the brachiocephalic artery, which showed rapid growth despite treatment with heparin and aspirin. Graft replacement of the brachiocephalic artery was performed under selective cerebral perfusion with deep hypothermia. Histology of the resected specimen revealed aortic atherosclerotic plaque.

An Argument for Routine Ultrasound Screening of the Thoracic Aorta in the Cardiac Surgery Population

Stroke and neurological injury are among the most devastating and disabling complications associated with cardiac surgery. Transesophageal echocardiography and epiaortic ultrasound allow for sensitive, point-of-care diagnosis of thoracic aortic disease, which is especially common in patients with heart disease. Unlike other operative procedures, the manipulation of the ascending aorta is routine in cardiac surgery and often unavoidable. Dislodgement and embolization from the ascending and aortic arch atheromas have been clearly associated with manipulation during cardiac surgery. Epiaortic ultrasound and transesophageal echocardiography screening are more accurate and more accessible to the operative team than any other available modality to diagnose atherosclerosis of the aorta. The goal of this review is to review the rationale and scientific evidence that suggests that the routine use of ultrasound guidance in cardiac surgery may improve postoperative outcomes in this patient population.

Aortic atherosclerosis, hypercoagulability, and stroke the APRIS (Aortic Plaque and Risk of Ischemic Stroke) study

OBJECTIVES

Our goal was to assess the effect of hypercoagulability on the risk of stroke in patients with aortic plaques.

BACKGROUND

Atherosclerotic plaques in the aortic arch are a risk factor for ischemic stroke. Their relationship with blood hypercoagulability, which might enhance their embolic potential and affect treatment and prevention, is not known.

METHODS

We performed transesophageal echocardiography in 255 patients with first acute ischemic stroke and in 209 control subjects matched by age, gender, and race/ethnicity. The association between arch plaques and hypercoagulability, and its effect on the stroke risk, was assessed with a case-control design. Stroke patients were then followed prospectively to assess recurrent stroke and death.

RESULTS

Large (> or =4 mm) arch plaques were associated with increased stroke risk (adjusted odds ratio [OR]: 2.4, 95% confidence interval [CI]: 1.3 to 4.6), especially when ulcerations or superimposed thrombus were present (adjusted OR: 3.3, 95% CI: 1.4 to 8.2). Prothrombin fragment F 1.2, an indicator of thrombin generation, was associated with large plaques in stroke patients (p = 0.02), but not in control subjects. Over a mean follow-up of 55.1 +/- 37.2 months, stroke patients with large plaques and F 1.2 over the median value had a significantly higher risk of recurrent stroke and death than those with large plaques but lower F 1.2 levels (230 events per 1,000 person-years vs. 85 events per 1,000 person-years; p = 0.05).

CONCLUSIONS

In patients presenting with acute ischemic stroke, large aortic plaques are associated with blood hypercoagulability, suggesting a role for coagulation activation in the stroke mechanism. Coexistence of large aortic plaques and blood hypercoagulability is associated with an increased risk of recurrent stroke and death.

MR imaging of thrombi using EP-2104R, a fibrin-specific contrast agent: initial results in patients

This study was an initial phase II trial in humans of molecular magnetic resonance (MR) imaging for improved visualization of thrombi in vessel territories potentially responsible for stroke using a new fibrin-specific contrast agent (EP-2104R). Eleven patients with thrombus in the left ventricle (n = 2), left or right atrium (n = 4), thoracic aorta (n = 4) or carotid artery (n = 1) as verified by an index examination (ultrasound, computed tomograpy, or conventional MR) were enrolled. All MR imaging was performed on 1.5 T whole-body MR-system using an inversion-recovery black-blood gradient-echo sequence. The same sequence was performed before and 2-6 h after low-dose intravenous administration of 4 mumol/kg EP-2104R. Two investigators assessed image quality and signal amplification. Furthermore, contrast-to-noise ratios (CNR) between the clot and the blood pool/surrounding soft tissue before and after administration of the contrast agent were compared using Student's t-test. MR imaging and data analysis were successfully completed in 10 patients. No major adverse effects occurred. On enhanced images, thrombi demonstrated high signal amplification, typically at the clot surface, with a significantly increased contrast in comparison to the surrounding blood pool and soft tissue (CNR for clot vs. blood pool, unenhanced and enhanced: 6 +/- 8 and 29 +/- 14; CNR for clot vs. soft tissue, unenhanced and enhanced: 0 +/- 4 and 21 +/- 13; P < 0.01 for both comparisons). EP-2104R allows for molecular MR imaging of thrombi potentially responsible for stroke. High contrast between thrombus and surrounding blood and soft tissues can be achieved with enhanced imaging.

Plaques in the descending aorta: a new risk factor for stroke? Visualization of potential embolization pathways by 4D MRI

The combination of morphologic and hemodynamic information can help in assessing the risk of embolic stroke associated with thrombi and plaques in the descending aorta. For two acute stroke patients, the determination of individual embolic pathways using flow-sensitive four-dimensional (4D) MRI are reported. 3D visualization of local flow patterns, i.e., retrograde flow channels originating at the site of the atheroma, in conjunction with exact plaque localization, suggested potential embolization of high-risk plaques in the descending aorta although they are located downstream from the supraaortic arteries. Our findings indicate that taking plaques of the descending aorta into consideration may help improve the spectrum of pathologies considered as high-risk sources for brain ischemia.