Complex Plaques in the Proximal Descending Aorta

Extended Computed Tomography Angiography for the Successful Diagnosis of Cardioaortic Thrombus in Acute Ischemic Stroke and TIA: Study Protocol for a Randomized Controlled Trial

INTRODUCTION

Cardiac imaging is one of the main components of the etiological investigation of ischemic strokes. However, basic and advanced cardiac imaging remain underused in most stroke centers globally. Computed tomography angiography (CTA) of the supra-aortic and intracranial arteries is the most frequent imaging modality applied during the evaluation of patients with acute ischemic stroke to identify the presence of a large vessel occlusion. Recent evidence from retrospective observational studies has shown a high detection of cardiac thrombi, ranging from 6.6 to 17.4%, by extending a CTA a few cm below the carina to capture cardiac images. However, this approach has never been prospectively compared against usual care in a randomized controlled trial. The Extended Computed Tomography Angiography for the Successful Screening of Cardioaortic Thrombus in Acute Ischemic Stroke and TIA (DAYLIGHT) prospective, randomized, controlled trial evaluates whether an extended CTA (eCTA) + standard-of-care stroke workup results in higher detection rates of cardiac and aortic source of embolism compared to standard-of-care CTA (sCTA) + standard-of-care stroke workup.

METHODS

DAYLIGHT is a single-center, prospective, randomized, open-blinded endpoint trial, aiming to recruit 830 patients with suspected acute ischemic stroke or transient ischemic attack (TIA) being assessed under acute code stroke at the emergency department or at a dedicated urgent stroke prevention clinic. Patients are randomized 1:1 to eCTA versus sCTA. The eCTA expands image acquisition caudally, 6 cm below the carina. All patients receive standard-of-care cardiac imaging and diagnostic stroke workup. The primary efficacy endpoint is the diagnosis of a cardioaortic thrombus after at least 30 days of follow-up. The primary safety endpoint is door-to-CTA completion time. The diagnosis of a qualifying ischemic stroke or TIA is independently adjudicated by a stroke neurologist, blinded to the study arm allocation. Patients without an adjudicated ischemic stroke or TIA are excluded from the analysis. The primary outcome events are adjudicated by a board-certified radiologist with subspecialty training in cardiothoracic radiology and a cardiologist with formal training in cardiac imaging. The primary analysis is performed according to the modified intention-to-diagnose principle and without adjustment by logistic regression models. Results are presented with odds ratios and 95% confidence intervals.

CONCLUSION

The DAYLIGHT trial will provide evidence on whether extending a CTA to include the heart results in an increased detection of cardioaortic thrombi compared to standard-of-care stroke workup.

Complex aortic plaques: hidden danger in aortic stenosis. Role of transesophageal echocardiography

Aortic stenosis is associated with aortic plaques in up to 85% of cases because they share risk factors and pathogenic pathways. Intrinsically, complex aortic plaques carry a high risk of stroke, which has also been demonstrated in the context of aortic stenosis, especially in patients who underwent percutaneous or surgical replacement. Transesophageal echocardiography (TEE) is the imaging test of choice to detect plaques in the thoracic aorta and classify them as complex plaques. Furthermore, the 3D modality allows us to better specify its dimensions and anatomical characteristics, such as added thrombi or the presence of ulcers inside. This review aims to evaluate the use of TEE to detect complex aortic plaques in patients with an indication for percutaneous or surgical aortic valve replacement. To highlight the association between aortic stenosis and complex aortic plaques, we attached to the review some TEE studies from our experience.

Aortic arch atheroma and stroke recurrence in mild stroke patients: ADS post-hoc analysis

BACKGROUND

Aortic arch atheroma is one of the embolic sources in patients with ischemic stroke. Although transesophageal echocardiogram (TEE) is the golden standard to evaluate the aortic arch atheroma, it is invasive and may be limited to patients with suspected embolism. Present post-hoc analysis evaluated the acute dual study data on mild stroke patients who had aortic arch atheroma proven by TEE and evaluate whether combined cilostazol and aspirin therapy might reduce the rate of stroke recurrence comparing aspirin therapy.

METHODS

Aortic arch atheroma was defined as aortic arch plaque with a maximal intima-medial thickness of ≥4.0 mm. Stroke recurrence included new diffusion-weighted image (DWI) lesions within 14 days.

RESULT

Among 316 (227 [72%] men; median, 66 [interquartile, 60-76] years old) patients, TEE found that 93 patients (29%) had the aortic arch atheroma, and 223 (71%) did not had it. The aortic arch atheroma group was older (P = 0.001) and accompanied with diabetes mellitus (P = 0.003), dyslipidemia (P = 0.046), smoking (P = 0.034), and had previous ischemic stroke history (P = 0.042) and multiple infarcts (P = 0.024) on admission. During hospitalization, new DWI lesion was frequently observed in the aortic arch atheroma group compared to the group without it (14.1% vs. 6.8%, P = 0.049). The rates of new DWI lesion were not different between dual antiplatelet therapy group and aspirin group (14.9% vs. 13.3%, P = 1.000).

CONCLUSION

Aortic arch atheroma was the representative of systematic arteriosclerosis associated with new DWI lesion in short-term. Combined antiplatelet therapy using cilostazol did not prevent new DWI appearance comparing aspirin therapy in this cohort.

Acute Ischemic Stroke and Transient Ischemic Attack in ST-Segment Elevation Myocardial Infarction Patients Who Underwent Primary Percutaneous Coronary Intervention

BACKGROUND

Acute ischemic stroke (AIS) is a rare but critical complication following ST-elevation myocardial infarction (STEMI). The risk of AIS or transient ischemic attack (TIA) may be amplified by invasive procedures, including primary percutaneous coronary intervention (PCI). This study aimed to investigate the factors associated with in-hospital AIS/TIA in patients with STEMI who required primary PCI.

METHODS

We included 941 STEMI patients who underwent primary PCI and divided them into an AIS/TIA group (n = 39) and a non-AIS/TIA group (n = 902), according to new-onset AIS/TIA. The primary interest was to find the factors associated with AIS/TIA by multivariate logistic regression analysis. We also compared clinical outcomes between the AIS/TIA and non-AIS/TIA groups.

RESULTS

The incidence of in-hospital deaths was significantly higher in the AIS/TIA group (46.2%) than in the non-AIS/TIA group (6.3%) (p < 0.001). Multivariate analysis revealed that cardiogenic shock (OR 3.228, 95% CI 1.492-6.986, p = 0.003), new-onset atrial fibrillation (AF) (OR 2.280, 95% CI 1.033-5.031, p = 0.041), trans-femoral approach (OR 2.336, 95% CI 1.093-4.992, p = 0.029), use of ≥4 catheters (OR 3.715, 95% CI 1.831-7.537, p < 0.001), and bleeding academic research consortium (BARC) type 3 or 5 bleeding (OR 2.932, 95% CI 1.256-6.846, p = 0.013) were significantly associated with AIS/TIA.

CONCLUSION

In STEMI patients with primary PCI, new-onset AIS/TIA was significantly associated with cardiogenic shock, new-onset AF, trans-femoral approach, the use of ≥4 catheters, and BARC type 3 or 5 bleeding. We should recognize these modifiable and unmodifiable risk factors for AIS/TIA in the treatment of STEMI.

Significant Contribution of Aortogenic Mechanism in Ischemic Stroke: Observation of Aortic Plaque Rupture by Angioscopy

BACKGROUND

Although embolic stroke accounts for most cerebral infarction, examinations to identify the embolic source have been insufficient. Nonobstructive general angioscopy (NOGA) has developed to allow the detailed observation of atheromatous changes of the aorta.

OBJECTIVES

The purpose of this study was to clarify the importance of the aortogenic mechanism in the development of ischemic stroke.

METHODS

We examined 114 consecutive patients whose aorta was observed by NOGA and who subsequently underwent brain magnetic resonance imaging to detect ischemic stroke lesions. In the evaluation of the aorta, the presence and location of spontaneously ruptured aortic plaque (SRAP) were determined. The aorta was observed from the origin to the arch (proximal aorta [PAo]) and the proximal descending aorta.

RESULTS

Forty-nine of 114 patients had SRAP observed by NOGA. Among these, 24 had SRAP in the PAo, and 43 had SRAP in the descending aorta. Thirty-three patients had ischemic stroke lesions, including 6 with a clinical neurologic deficit. The frequency at which SRAP was detected in these patients was significantly higher in comparison to 81 patients without ischemic stroke (69% vs 33%; P < 0.01). The sensitivity and specificity of the presence of SRAP for ischemic stroke were 0.70 and 0.68, respectively. The presence of SRAP in PAo was significantly correlated with ischemic stroke (odds ratio: 14.3; P < 0.001).

CONCLUSIONS

In the treatment of ischemic stroke, attention should be paid to SRAP, especially that in the PAo. (STROKE-NOGA [SponTaneously Ruptured aOrtic plaques as a potential cause of embolic stroKEs visualized by Non-Obstructive General Angioscopy] Study; UMIN000034588).

Intracranial Blood Flow Quantification by Accelerated Dual-venc 4D Flow MRI: Comparison With Transcranial Doppler Ultrasound

BACKGROUND

Dual-venc 4D flow MRI, recently introduced for the assessment of intracranial hemodynamics, may provide a promising complementary approach to well-established tools such as transcranial Doppler ultrasound (TCD) and overcome some of their disadvantages. However, data comparing intracranial flow measures from dual-venc 4D flow MRI and TCD are lacking.

PURPOSE

To compare cerebral blood flow velocity measures derived from dual-venc 4D flow MRI and TCD.

STUDY TYPE

Prospective cohort.

SUBJECTS

A total of 25 healthy participants (56 ± 4 years old, 44% female).

FIELD STRENGTH/SEQUENCE

A 3 T/dual-venc 4D flow MRI using a time-resolved three-dimensional phase-contrast sequence with three-dimensional velocity encoding.

ASSESSMENT

Peak velocity measurements in bilateral middle cerebral arteries (MCA) were quantified from dual-venc 4D flow MRI and TCD. The MRI data were quantified by two independent observers (S.M and Y.M.) and TCD was performed by a trained technician (A.L.M.). We assessed the agreement between 4D flow MRI and TCD measures, and the interobserver agreement of 4D flow MRI measurements.

STATISTICAL TESTS

Peak velocity from MRI and TCD was compared using Bland-Altman analysis and coefficient of variance. Intraclass correlation coefficient (ICC) was used to assess MRI interobserver agreement. A P value < 0.05 was considered statistically significant.

RESULTS

There was excellent interobserver agreement in dual-venc 4D flow MRI-based measurements of peak velocity in bilateral MCA (ICC = 0.97 and 0.96 for the left and right MCA, respectively). Dual-venc 4D flow MRI significantly underestimated peak velocity in the left and right MCA compared to TCD (bias = 0.13 [0.59, -0.33] m/sec and 0.15 [0.47, -0.17] m/sec, respectively). The coefficient of variance between dual-venc 4D flow MRI and TCD measurements was 26% for the left MCA and 22% for the right MCA.

DATA CONCLUSION

There was excellent interobserver agreement for the assessment of MCA peak velocity using dual-venc 4D flow MRI, and ≤20% under-estimation compared with TCD.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 2.

Vessel wall MR imaging of aortic arch, cervical carotid and intracranial arteries in patients with embolic stroke of undetermined source: A narrative review

Despite advancements in multi-modal imaging techniques, a substantial portion of ischemic stroke patients today remain without a diagnosed etiology after conventional workup. Based on existing diagnostic criteria, these ischemic stroke patients are subcategorized into having cryptogenic stroke (CS) or embolic stroke of undetermined source (ESUS). There is growing evidence that in these patients, non-cardiogenic embolic sources, in particular non-stenosing atherosclerotic plaque, may have significant contributory roles in their ischemic strokes. Recent advancements in vessel wall MRI (VW-MRI) have enabled imaging of vessel walls beyond the degree of luminal stenosis, and allows further characterization of atherosclerotic plaque components. Using this imaging technique, we are able to identify potential imaging biomarkers of vulnerable atherosclerotic plaques such as intraplaque hemorrhage, lipid rich necrotic core, and thin or ruptured fibrous caps. This review focuses on the existing evidence on the advantages of utilizing VW-MRI in ischemic stroke patients to identify culprit plaques in key anatomical areas, namely the cervical carotid arteries, intracranial arteries, and the aortic arch. For each anatomical area, the literature on potential imaging biomarkers of vulnerable plaques on VW-MRI as well as the VW-MRI literature in ESUS and CS patients are reviewed. Future directions on further elucidating ESUS and CS by the use of VW-MRI as well as exciting emerging techniques are reviewed.

Hemodynamic Assessment in Bicuspid Aortic Valve Disease and Aortic Dilation: New Insights From Voxel-By-Voxel Analysis of Reverse Flow, Stasis, and Energetics

Objectives: Clinical management decisions surrounding ascending aorta (AAo) dilation in bicuspid aortic valve (BAV) disease benefit from personalized predictive tools. 4D-flow MRI may provide patient-specific markers reflective of BAV-associated aortopathy. This study aims to explore novel 4D-flow MRI parametric voxel-by-voxel forward flow, reverse flow, kinetic energy and stasis in BAV disease. We hypothesize that novel parametric voxel-by-voxel markers will be associated with aortic dilation and referral for surgery and can enhance our understanding of BAV hemodynamics beyond standard metrics.

Methods: A total of 96 subjects (73 BAV patients, 23 healthy controls) underwent MRI scan. Healthy controls had no known cardiovascular disease. Patients were clinically referred for AAo dilation assessment. Indexed diameters were obtained by dividing the aortic diameter by the patient’s body surface area. Patients were followed for the occurrence of aortic surgery. 4D-flow analysis was performed by a single observer in five regions: left ventricular outflow tract (LVOT), AAo, arch, proximal descending aorta (PDAo), and distal descending aorta (DDAo). In each region peak velocity, kinetic energy (KE), forward flow (FF), reverse flow (RF), and stasis were measured on a voxel-by-voxel basis. T-tests (or non-parametric equivalent) compared flow parameters between cohorts. Univariate and multivariate analyses explored associations between diameter and parametric voxel-by-voxel parameters.

Results: Compared to controls, BAV patients showed reduced stasis (p < 0.01) and increased RF and FF (p < 0.01) throughout the aorta, and KE remained similar. In the AAo, indexed diameter correlated with age (R = 0.326, p = 0.01), FF (R = −0.648, p < 0.001), RF (R = −0.441, p < 0.001), and stasis (R = −0.288, p < 0.05). In multivariate analysis, FF showed a significant inverse association with AAo indexed diameter, independent of age. During a median 179 ± 180 days of follow-up, 23 patients (32%) required aortic surgery. Compared to patients not requiring surgery, they showed increased KE and peak velocity in the proximal aorta (p < 0.01), accompanied by increased RF and reduced stasis throughout the entire aorta (p < 0.01).

Conclusion: Novel voxel-by-voxel reverse flow and stasis were altered in BAV patients and are associated with aortic dilation and surgical treatment.

Influence of Pulse Wave Velocity on Atherosclerosis and Blood Flow Reversal in the Aorta: A 4-Dimensional Flow Magnetic Resonance Imaging Study in Acute Stroke Patients and Matched Controls

BACKGROUND

Aortic stiffness is associated with a higher incidence of cardiovascular events including stroke. The primary aim of this study was to evaluate whether increased pulse wave velocity (PWV), a marker of stiffness, is an independent predictor of aortic atheroma. The secondary aim was to test whether increased PWV reinforces retrograde blood flow from the descending aorta (DAo), a mechanism of stroke.

METHODS

We performed a cross-sectional case-control study with prospective data acquisition. In all, 40 stroke and 60 ophthalmic patients matched for age and cardiovascular risk factors were included. Multicontrast magnetic resonance imaging (MRI) protocol of the aorta tailored to allow a detailed plaque analysis using 3-dimensional (D) T1-weighted bright blood, T2-weighted and proton density-weighted black blood, and hemodynamic assessment using 4D flow MRI was applied. Individual PWV was calculated based on 4D flow MRI data using the time-to-foot of the blood flow waveform. The extent of maximum retrograde blood flow from the proximal DAo into the arch was quantified.

RESULTS

PWV was higher in stroke patients compared with controls (7.62±2.59 vs. 5.96±2.49 m/s; P=0.005) and in patients with plaques (irrespective of thickness) compared with patients without plaques (7.47±2.89 vs. 5.62±1.89 m/s; P=0.002). Increased PWV was an independent predictor of plaque prevalence and contributed significantly to a predictor model explaining 36.5% (Nagelkerke R2) of the variance in plaque presence. Maximum retrograde flow extent from the proximal DAo was not correlated with PWV.

CONCLUSIONS

Aortic stiffness was higher in stroke patients and associated with a higher prevalence of plaques. Increased PWV was an independent predictor of plaque presence. Accordingly, regional PWV seems to be a valuable biomarker for the assessment and management of aortic atherosclerosis. However, no association was found for increased retrograde flow extent from the DAo.

Thoracic endovascular aortic repair for recurrent stroke due to atheromatic plaque in the proximal descending aorta: a case report

Background

Diastolic retrograde flow in the descending aorta (DAo) may occur in the presence of atherosclerosis and may be overlooked as a mechanism of retrograde embolization in patients with stroke. We performed thoracic endovascular aortic repair (TEVAR) in a patient with recurrent cerebral infarctions for treatment of aortic aneurysm with atheromatic plaque, which was considered as the source of embolism.

Case presentation

A 56-year-old man with a history of idiopathic thrombocytopenia and hypertension was referred to our hospital with paralysis of the right upper and lower limbs. Multiple cerebral infarctions were found and treated; however, 1 month later, another cerebral infarction developed. A small saccular aortic aneurysm with plaque was found beyond the left subclavian artery, and this site was deemed as the source of embolism. We performed TEVAR to prevent further recurrence of cerebral infarctions. No cerebral infarctions were observed 6 months post-operation.

Conclusions

TEVAR is a useful treatment for not only aortic aneurysm and dissection, but also cerebral infarctions caused by an embolic source proximal to the DAo due to retrograde aortic blood flow.

Investigation of Aortic Wall Thickness, Stiffness and Flow Reversal in Patients With Cryptogenic Stroke: A 4D Flow MRI Study

BACKGROUND

Stroke etiology is undetermined in approximately one-sixth to one-third of patients. The presence of aortic flow reversal and plaques in the descending aorta (DAo) has been identified as a potential retrograde embolic mechanism.

PURPOSE

To assess the relationships between aortic stiffness, wall thickness, and flow reversal in patients with cryptogenic stroke and healthy controls.

STUDY TYPE

Prospective.

POPULATION

Twenty one patients with cryptogenic stroke and proven DAo plaques (69 ± 9 years, 43% female), 18 age-matched controls (age: 65 ± 8 years, 61% female), and 14 younger controls (36 ± 9 years, 57% female).

FIELD STRENGTH/SEQUENCE

1.5T; 4D flow MRI and 3D dark blood T1 -weighted turbo spin echo MRI of the aorta.

ASSESSMENT

Noncontrast aortic 4D flow MRI to measure 3D flow dynamics and 3D dark blood aortic wall MRI to assess wall thickness. 4D flow MRI analysis included automated quantification of aortic stiffness by pulse wave velocity (PWV) and voxelwise mapping of the flow reversal fraction (FRF).

STATISTICAL TESTS

Analysis of variance (ANOVA) or Kruskal-Wallis tests, Student's unpaired t-tests or Wilcoxon rank-sum tests, regression analysis.

RESULTS

Aortic PWV and FRF were statistically higher in patients (8.9 ± 1.7 m/s, 18.4 ± 7.7%) than younger controls (5.3 ± 0.8 m/s, P < 0.0167; 8.5 ± 2.9%, P < 0.0167), but not age-matched controls (8.2 ± 1.6 m/s, P = 0.22; 15.6 ± 5.8%, P = 0.22). Maximum aortic wall thickness was higher in patients (3.1 ± 0.7 mm) than younger controls (2.2 ± 0.2 mm, P < 0.0167) and age-matched controls (2.7 ± 0.5 mm) (P < 0.0167). For all subjects, positive relationships were found between PWV and age (R2 = 0.71, P < 0.05), aortic wall thickness (R2 = 0.20, P < 0.05), and FRF (R2 = 0.47, P < 0.05). Patients demonstrated relationships between PWV and FRF in the ascending aorta (R2 = 0.32, P < 0.05) and arch (R2 = 0.24, P < 0.05).

DATA CONCLUSION

This study showed the utility of 4D flow MRI for evaluating aortic PWV and voxelwise flow reversal. Positive relationships between aortic PWV, wall thickness, and flow reversal support the hypothesis that aortic stiffness is involved in this retrograde embolic mechanism.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 1.

Mind the Heart: Electrocardiography-gated cardiac computed tomography-angiography in acute ischaemic stroke-rationale and study design

Rationale

About one-third of ischaemic strokes are caused by cardioembolism, and a substantial proportion of cryptogenic strokes likely also originate from the heart or aortic arch. Early determination of aetiology is important to optimise management. Computed Tomography-angiography of the heart is emerging as an alternative to echocardiography to detect cardio-aortic sources of embolism in stroke patients, but its diagnostic yield in acute ischaemic stroke has not been thoroughly assessed.Hypothesis: We hypothesise that electrocardiography-gated computed tomography-angiography of the heart and aortic arch, acquired in the acute phase in patients with ischaemic stroke, has a higher diagnostic yield than transthoracic echocardiography as a first-line screening method for detection of cardio-aortic sources of embolism.

Methods and design

Mind the Heart is a single-centre prospective observational cohort study. We will include consecutive adult patients with acute ischaemic stroke who are potentially eligible for reperfusion therapy. Patients undergo non-electrocardiography-gated computed tomography-angiography of the aortic arch, cervical and intracranial arteries, directly followed by prospective sequential electrocardiography-gated cardiac computed tomography-angiography. Routine work-up for cardioembolism including 12-leads electrocardiography, Holter electrocardiography and transthoracic echocardiography is performed as soon as possible. The primary endpoint is the proportion of patients with a predefined high-risk cardio-aortic source of embolism on computed tomography-angiography versus transthoracic echocardiography in patients who underwent both investigations. Based on an expected 5% additional yield of computed tomography-angiography, a sample size of 450 patients is required.

Conclusions

The Mind the Heart study will generate a reliable estimate of the diagnostic yield of echocardiography-gated cardio-aortic computed tomography-angiography performed in the acute phase of ischaemic stroke.

Who Should Rather Undergo Transesophageal Echocardiography to Determine Stroke Etiology: Young or Elderly Stroke Patients?

Introduction: The indication of transesophageal echocardiography (TEE) in acute stroke is unclear. Thus, we systematically studied the impact of TEE on determining stroke etiology and secondary prevention in patients of different age-groups with cryptogenic stroke.

Methods: Four hundred and eighty five consecutive patients with acute retinal or cerebral ischemia were prospectively included and underwent routine stroke workup including TEE. Stroke etiology was identified according to the TOAST classification and patients were divided in those with determined and cryptogenic stroke etiology without TEE results. Then, the frequency of high- and potential-risk sources in TEE was evaluated in <55, 55–74, and ≥75 year-old patients with cryptogenic stroke etiology.

Results: Without TEE, stroke etiology was cryptogenic in 329(67.8%) patients and TEE determined possible etiology in 158(48.4%) of them. In patients aged <55, 55–74, ≥75, TEE detected aortic arch plaques ≥4 mm thickness in 2(1.2%), 37(23.0%), and 33(40.2%) and plaques with superimposed thrombi in 0(0.0%), 5(3.1%), and 7(8.5%); left atrial appendage peak emptying flow velocity ≤30cm/s in 0(0.0%), 1(0.6%), and 2(2.4%), spontaneous echo contrast in 0(0.0%), 1(0.6%), and 6(7.3%), endocarditis in 0(0.0%), 0(0.0%), and 1(1.2%) and patent foramen ovale (PFO) plus atrial septum aneurysm (ASA) in 18(20.9%), 32(19.9%), and 14(17.1%), respectively. TEE changed secondary prevention in 16.4% of these patients following guidelines of 2010/11 and still 9.4% when applying the guidelines of 2020.

Conclusions: TEE was highly valuable for determining stroke etiology and influenced individual secondary prevention based on available treatment guidelines and expert opinion in most cases. In young patients the impact of TEE was limited to the detection of septal anomalies. By contrast, in older patients TEE detected high numbers of complex aortic atheroma and potential indicators of paroxysmal atrial fibrillation.

Neurologic complications of diseases of the aorta

Neurologic complications of diseases of the aorta are common, as the brain and spinal cord function is highly dependent on the aorta and its branches for blood supply. Any disease impacting the aorta may have significant impact on the ability to deliver oxygenated blood to the central nervous system, resulting in ischemia-and if prolonged-cerebral and spinal infarct. The breadth of pathology affecting the aorta is diverse and neurologic complications can vary dramatically based on the location, severity, and underlying etiology. This chapter outlines the major pathology of the aorta while highlighting the associated neurologic complications. This chapter covers the entire spectrum of neurologic complications associated with aortic disease by beginning with a detailed overview of the spinal cord vascular anatomy followed by a discussion of the most common aortic pathologies affecting the nervous system, including aortic aneurysm, aortic dissection, aortic atherosclerosis, inflammatory and infectious aortopathies, congenital abnormalities, and aortic surgery.

A Review of Potential Mechanisms of Cryptogenic Stroke and a Recommended Approach to Diagnosis

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Right-sided Upper Extremity Access for Patients Undergoing Parallel Graft Placement during Endovascular Aortic Repair is Not Associated with Increased Neurologic Events When Compared with Left Upper Extremity Access

BACKGROUND

The safety and efficacy of right axillary cannulation during complex aortic aneurysm repair for the deployment of chimney grafts is controversial; however, there are few studies that compare right and left upper extremity access. We favor the right axillary approach because of the relative ease of access to the visceral branches and the ability of surgeons and nursing staff to work on the same side of the patient, while avoiding the left sided image intensifier. We aim to demonstrate that right-sided access is equivalent or safer than left-sided access in terms of technical success and complication rates, with a focus on neurologic outcomes.

METHODS

This is a single-institution retrospective study with a review of patients who underwent aortic intervention from January 2012 through December 2018. A total of 398 aortic interventions were performed, and 97 of these required brachial, axillary, or subclavian arterial access for attempted ChEVAR or thoracic endovascular aortic repair with parallel chimney grafts. Primary end points that were analyzed were site or sites of upper extremity access, technical success, 30-day mortality, cerebrovascular events, and subclavian/axillary artery injury. The number of parallel grafts, age, mean hospital length of stay, prior aortic intervention, emergent or elective status were also analyzed.

RESULTS

Ninety-seven endovascular aortic operations required upper extremity access, with 67 using access from the right upper extremity, 26 using access from the left upper extremity, and 4 using bilateral upper extremity access. A total of 68.0% of patients had undergone prior aortic surgery. Technical success was achieved in 85 cases (87.6%). Five total patients suffered cerebrovascular accidents, with 2 occurring in left-sided access (7.7%), 2 in right-sided access (3.0%), and 1 in bilateral access (25%).

CONCLUSIONS

Right upper extremity access for patients undergoing parallel graft placement during endovascular aortic aneurysm repair is a safe and feasible approach that is not associated with an increased risk of stroke or neurological events as compared with left upper extremity access.

Blood Flow Visualization and Wall Shear Stress Measurement of Carotid Arteries Using Vascular Vector Flow Mapping

Carotid artery ultrasound is extensively used to assess early- and late-stage atherosclerosis via the intima-media thickness and increased blood flow velocity caused by stenosis, respectively. However, the effect of wall shear stress (WSS) has not been considered to date. This study aimed to visualize the blood flow of carotid arteries and measured WSS using vector flow mapping (VFM) developed specifically for vascular use. Patients with cerebrovascular diseases were prospectively enrolled and examined with carotid ultrasound using VFM Vascular. WSS was calculated in the common carotid artery and internal carotid artery. Blood flow in 82 common carotid arteries was visualized with VFM Vascular. The maximum and mean WSSs were negatively correlated with age and intima-media thickness. The WSS in 16 internal carotid artery plaques was significantly higher upstream of the plaque than downstream. Therefore, VFM Vascular is a promising method that provides a novel indicator of atherosclerosis.

Heart applications of 4D flow

Four-dimensional (4D) flow sequences are an innovative type of MR sequences based upon phase contrast (PC) sequences which are a type of application of Angio-MRI together with the Time of Flight (TOF) sequences and Contrast-Enhanced Magnetic Resonance Acquisition (CE-MRA). They share the basic principles of PC, but unlike PC sequences, 4D flow has velocity encoding along all three flow directions and three-dimensional (3D) anatomic coverage. They guarantee the analysis of flow with multiplanarity on a post-processing level, which is a unique feature among MR sequences. Furthermore, this technique provides a completely new level to the in vivo flow analysis as it allows measurements in never studied districts such as intracranial applications or some parts of the heart never studied with echo-color-doppler, which is its sonographic equivalent. Furthermore, this technique provides a completely new level to the in vivo flow analysis as it allows accurate measurement of the flows in different districts (e.g., intracranial, cardiac) that are usually studied with echo-color-doppler, which is its sonographic equivalent. Of note, the technique has proved to be affected by less inter and intra-observer variability in several application. 4D-flow basic principles, advantages, limitations, common pitfalls and artefacts are described. This review will outline the basis of the formation of PC image, the construction of a 4D-flow and the huge impact the technique is having on the cardiovascular non-invasive examination. It will be then studied how this technique has had a huge impact on cardiovascular examinations especially on a central heart level.

Renin Angiotensin System Inhibitors Reduce Aortic Stiffness and Flow Reversal After a Cryptogenic Stroke

BACKGROUND

Blood flow reversal is a possible mechanism for retrograde embolism in the setting of high-risk atherosclerotic plaques in the descending aorta (DAo). Evidence suggests that pulse wave velocity (PWV) is a determinant of blood flow reversal and can be reduced by the destiffening effect of renin-angiotensin system inhibitors (RASI).

PURPOSE

To evaluate the impact of antihypertensive therapy on in vivo changes in PWV and flow reversal in patients with cryptogenic stroke.

STUDY TYPE

Prospective.

POPULATION

Sixteen patients (69 ± 9 years; 10 males) included after cryptogenic stroke.

FIELD STRENGTH/SEQUENCE

3T. 4D flow sequence (temporal resolution = 19.6 msec) ASSESSMENT: Patients underwent aortic MRI at baseline and at 6-month follow-up. Patients received standard-of-care antihypertensive therapy that were classified as RASI vs. non-RASI medications (ie, destiffening vs. nondestiffening).We compared aortic PWV, flow reversal fraction (FRF), aortic measurements, cardiac function, and other aortic and cardiac measurements in the antihypertensive therapy groups.

STATISTICAL TESTS

Two-tailed paired or unpaired Student's t-tests (normal distributions) or Wilcoxon tests (nonnormal distribution). Univariate correlations using Pearson correlation coefficients.

RESULTS

There was a significant decrease in PWV in the RASI (n = 10) group (9.4 ± 1.6 m/s vs. 8.3 ± 1.9 m/s; P < 0.05), as well as FRF (18.6% ± 4.1% vs. 16.3% ± 4.0%; P < 0.05) between baseline and the 6-month MRI studies. There were no changes in PWV or FRF in the non-RASI (n = 6) group (P = 0.146 and P = 0.32). A decrease in FRF was significantly correlated with a decrease in PWV (r = 0.53; P < 0.05).

DATA CONCLUSION

The findings of our study suggest that RASI therapy after cryptogenic stroke resulted in a decrease of blood flow reversal and aortic stiffness.

EVIDENCE LEVEL

1 TECHNICAL EFFICACY STAGE: 4.

Atherosclerotic plaque detected by transesophageal echocardiography is an independent predictor for all-cause mortality

Atherosclerotic lesions in the great arteries are frequent findings in the elderly. Numerous studies have shown their strong predictive value for cardiovascular disease, embolic events, and mortality. We sought to determine the risk of all-cause mortality depending on the localization of plaques in the thoracic aorta evaluated by transesophageal echocardiography (TEE). A total of 2,054 patients (median age 65 years, interquartile range 52–73; 58% men) who underwent a TEE examination between 01/2007 and 03/2015 were retrospectively analyzed. For each patient, the presence of atherosclerotic lesions in the ascending aorta, the aortic arch, and in the descending aorta, as well as cardiovascular risk factors and survival were documented. Median follow-up period was 48 months (interquartile range 38–58). Multivariate Cox regression analysis indicated plaque in the ascending aorta (HR of 1.36, 95% CI 1.01–1.83, P = 0.046), the aortic arch (HR of 1.78, 95% CI 1.29–2.45, P < 0.001), the descending aorta (HR of 2.01, 95% CI 1.54–2.77, P < 0.001), and plaque in any part of the thoracic aorta (HR of 1.84, 95% CI 1.42–2.4, P < 0.001), as independent predictors for all-cause mortality after adjusting for age, sex, arterial hypertension, hyperlipidemia, smoking, and diabetes. In this study, we could demonstrate that more than mild plaque at any site of the thoracic aorta predicts all-cause mortality. Assessment of atherosclerotic lesions in all segments of the thoracic aorta should be part of every routine TEE examination.

The American Association for Thoracic Surgery consensus guidelines on bicuspid aortic valve-related aortopathy: Full online-only version

Bicuspid aortic valve disease is the most common congenital cardiac disorder, being present in 1% to 2% of the general population. Associated aortopathy is a common finding in patients with bicuspid aortic valve disease, with thoracic aortic dilation noted in approximately 40% of patients in referral centers. Several previous consensus statements and guidelines have addressed the management of bicuspid aortic valve-associated aortopathy, but none focused entirely on this disease process. The current guidelines cover all major aspects of bicuspid aortic valve aortopathy, including natural history, phenotypic expression, histology and molecular pathomechanisms, imaging, indications for surgery, surveillance, and follow-up, and recommendations for future research. It is intended to provide clinicians with a current and comprehensive review of bicuspid aortic valve aortopathy and to guide the daily management of these complex patients.

[Possibilities and limitations of three-dimensional transesophageal echocardiography in the diagnosis of thoracic aorta atherosclerosis]

OBJECTIVES

To compare the possibilities and limitations of the two-dimensional (2D) and three-dimensional (3D) multiplane transesophageal echocardiography (TEE) for the diagnosis of the thoracic aorta (TA) atherosclerosis stage, qualitative and quantitative assessment of aortic atheromas and coronary atherosclerosis prediction. Materials and methods. 2D and 3D multiplane TEE of the TA was performed in 180 consecutive CAD patients (104 men, 76 women, mean age 62,4±7,5 years) using Philips IE33 xMatrix system and a X7-2t multiplane probe. Ascending aorta, accessible parts of the arch and descending TA were visualized in 2D mode with standard protocol using Live xPlane mode. 3D study of TA was performed using Live 3D and Full Volume modes. 2D and 3D studies were recorded as video clips series on a system hard drive with subsequent off line processing on a QLab 10.8 (Philips) workstation. Qualitative and quantitative assessment of every atheroma was performed using 2D and 3D modes. The degree of severity and distribution of the TA atheromatosis was evaluated according to the classification of ASE and EACVI (2015): grade 0 - intimal-medial thickness ≤1 mm, 1 - intimal thickness ≤2 mm, 2 - focal or diffuse intimal thickening of 2-3 mm (small atheromas), 3 - atheromas &gt;3-5 mm (no mobile/ulcerated components), 4 - atheromas &gt; 5 mm (no mobile/ulcerated components), 5 - grade 2, 3, or 4 atheromas plus mobile or ulcerated components. After TEE all patients underwent digital coronary angiography. SYNTAX Score was calculated in 122 (67,7%) patients with no coronary stents and bypass grafts. Results. 620 atheromas were analysed: 109 (17,6%) in the ascending part, 8 (1,3%) in the arch and 503 (81,1%) in the descending part. On average 3,4±2,1 atheromas per patient were revealed. Atheromas height in 3D was significantly higher (p&lt;0,001), than in 2D, being 0,38±0,09 cm and 0,26±0,07 cm, respectively.  Averaged atheromas height increase in 3D was 0,12±0,06 cm. In 3D 87,7% of atheromas have shown irregular contours while in 2D only 35,4% of atheromas had rough countors. The mobile component in 6 (66,6%) out of 9 atheromas was revealed only in 3D. In 2D 1-5 stages of TA atheromatosis were revealed in 22 (12,2%), 103 (57,2%), 43 (23,9%), 7 (3,9%) and 4 (2,2%) cases, respectively. In 3D 1-5 stages of TA atheromatosis were revealed in 16 (8,9%), 25 (13,9%), 90 (50%), 38 (21,1%) and 10 (5,5%) cases, respectively. With 3D TEE 130 (72,2%) patients were found to have higher gradation of TA atheromatosis stage. TA atheromatosis was not detected in 1 (0,6%) patient. The direct Spearman's correlation between a stage of TA atheromatosis and SYNTAX Score which has been established for 2D rs =0,32 p&lt;0,001 and 3D rs =0,30, p&lt;0,01, respectively. Conclusion. A comparison between 2D and 3D TEE has shown, that 3D is more precise method of qualitative and quantitative assessment of aortic atheromas and diagnosis of TA atheromatosis stage which allows, ultimately, to change the stage of TA atheromatosis towards a higher gradation. 3D ultrasound stage of TA atheromatosis is a surrogate marker of the severity and prevalence of coronary atherosclerosis.

Aortic and Internal Carotid Atherosclerosis in Patients with Carotid Stenosis: Semiautomatic Volumetric Analysis of Low-Attenuation Plaque on Curved Planar Reformations Using MDCT Angiographic Data

This retrospective study included 65 patients who underwent multidetector computed tomography (MDCT) carotid angiography; 28 patients were <70 years old (group 1), and 37 were ≥70 years old (group 2). Each low-attenuation (<30 Hounsfield units [HU]) plaque volume (LPV) and total uncalcified plaque volume ([TUPV] ≤150 HU) were semiautomatically measured on each aortic arch and internal carotid artery (ICA) curved planar reformations (CPR), using MDCT angiographic data. Correlation coefficients were employed to assess the impact of each plaque volume on various factors including ICA stenosis. The correlations (r > 0.5) were observed between aortic LPV and each ICA stenosis ratio and >30% stenosis in group 1, between aortic TUPV and male gender in group 1, and between ICA-TUPV and each aortic TUPV or the largest plaque thickness in group 2. Marginal correlations were observed between hyperlipidemia and aortic LPV and ICA-TUPV in group 1. There was no association between cerebral infarction and the aortic and ICA plaques. Both the aortic arch and ICA plaque volumes can be measured clinically. The increasing aortic LPV may be a significant factor associated with the development of ICA stenosis in patients younger than 70 years old.

Embolic strokes of undetermined source: theoretical construct or useful clinical tool?

In 2014, the definition of embolic strokes of undetermined source (ESUS) emerged as a new clinical construct to characterize cryptogenic stroke (CS) patients with complete vascular workup to determine nonlacunar, nonatherosclerotic strokes of presumable embolic origin. NAVIGATE ESUS, the first phase III randomized-controlled, clinical trial (RCT) comparing rivaroxaban (15 mg daily) with aspirin (100 mg daily), was prematurely terminated for lack of efficacy after enrollment of 7213 patients. Except for the lack of efficacy in the primary outcome, rivaroxaban was associated with increased risk of major bleeding and hemorrhagic stroke compared with aspirin. RE-SPECT ESUS was the second phase III RCT that compared the efficacy and safety of dabigatran (110 or 150 mg, twice daily) to aspirin (100 mg daily). The results of this trial have been recently presented and showed similar efficacy and safety outcomes between dabigatran and aspirin. Indirect analyses of these trials suggest similar efficacy on the risk of ischemic stroke (IS) prevention, but higher intracranial hemorrhage risk in ESUS patients receiving rivaroxaban compared to those receiving dabigatran (indirect HR = 6.63, 95% CI: 1.38-31.76). ESUS constitute a heterogeneous group of patients with embolic cerebral infarction. Occult AF represents the underlying mechanism of cerebral ischemia in the minority of ESUS patients. Other embolic mechanisms (paradoxical embolism via patent foramen ovale, aortic plaque, nonstenosing unstable carotid plaque, etc.) may represent alternative mechanisms of cerebral embolism in ESUS, and may mandate different management than oral anticoagulation. The potential clinical utility of ESUS may be challenged since the concept failed to identify patients who would benefit from anticoagulation therapy. Compared with the former diagnosis of CS, ESUS patients required thorough investigations; more comprehensive diagnostic work-up than is requested in current ESUS diagnostic criteria may assist clinicians in uncovering the source of brain embolism in CS patients and individualize treatment approaches.

Retrograde aortic blood flow as a mechanism of stroke: MR evaluation of the prevalence in a population-based study

OBJECTIVES

Retrograde blood flow from complex atheroma in the descending aorta (DAo) has only recently been described as a potential mechanism of stroke. However, prevalence of this mechanism in the general population and the exact factors influencing stroke risk are unclear.

METHODS

One hundred twenty-six consecutively recruited inhabitants of Freiburg, Germany, between 20 and 80 years of age prospectively underwent 3-T MRI. Aortic plaque location and thickness were determined by 3D T1 MRI (1 mm³). 4D flow MRI (spatial/temporal resolution 2 mm³/20 ms) and dedicated software were used to determine prevalence and extent of flow reversal and potential embolization from DAo plaques. Flow was correlated with baseline characteristics and echocardiographic and MRI parameters (aortic diameter, wall thickness, and pulse wave velocity).

RESULTS

The maximum length of retrograde blood flow connecting the DAo with the left subclavian artery (LSA) increased from 16.1 ± 8.3 mm in 20-29-year-old to 24.7 ± 11.7 mm in 70-80-year-old subjects, correlated with age (r = 0.37; p < 0.001), and was lower in females (p = 0.003). Age was the only independent predictor of increased flow reversal. Complex DAo plaques ≥ 4-mm thickness were found in eight subjects (6.3%) and were connected with the LSA, left common carotid artery, and brachiocephalic trunk in 8 (100%), 1 (12.5%), and 0 (0%) cases, respectively.

CONCLUSIONS

Retrograde blood flow from the DAo was very frequent. However, potential retrograde embolization was rare due to the low incidence of complex DAo plaques. The magnitude of flow reversal and prevalence of complex atheroma increased with age. Thus, older patients with aortic atherosclerosis are especially vulnerable to this stroke mechanism.

KEY POINTS

• 4D flow MRI allows in vivo visualization and quantification of individual and three-dimensional blood flow patterns within the thoracic aorta including retrograde components. • This population-based study showed that blood flow reversal from the proximal descending aorta to the brain-supplying great arteries is very frequent and able to reach all brain territories. The extent of such flow reversal increases with age and with the extent of aortic atherosclerosis. • The combination of blood flow reversal with plaque rupture in the proximal descending aorta constitutes a potential stroke mechanism that should be considered in future trials and in the management of stroke patients in clinical routine.

Atherosclerotic plaque burden evaluated from neck to groin: effect of gender and cardiovascular risk factors

We explored the impact of gender and cardiovascular risk factors (RF) in the distribution and burden of coronary and extra-coronary atherosclerotic plaques among patients undergoing ECG-gated thoracoabdominal computed tomography angiography (CTA) from the supra-aortic trunks to the femoral arteries. We included a consecutive cohort of patients who underwent ECG-gated thoracoabdominal aortic CTA from the supra-aortic trunks to the pubic symphysis. We evaluated the number of coronary segments with plaques [segment-involvement score (SIS)]; and the extra-coronary atherosclerotic plaque burden, comprising the aorta and supra-aortic trunks, iliofemoral arteries, and visceral arteries (extra-coronary SS). A total of 3400 vascular segments were evaluated in 100 patients (mean age 67.0 ± 12.6 years, 66% male). Seventy-two (72%) patients had evidence of atherosclerosis in the coronary tree (coronary SIS ≥ 1), of which 32% was extensive (coronary SIS > 5). Males had a significantly higher prevalence of coronary SIS ≥ 1 [53 (80%), vs. 19 (56%), p = 0.018], and coronary SIS > 5 [24 (36%) vs. 8 (24%), p = 0.035] than females. Extra-coronary SS was similar between genders (males 10.2 ± 5.8 vs. females 9.7 ± 5.4, p = 0.70), irrespective of the location along the different vascular beds. The number of coronary RF was significantly related to the coronary SIS (p = 0.038), and hypertension and diabetes were consistently related to coronary and extra-coronary plaque burden. In the present study involving analysis of multiple vascular beds from the supra-aortic trunks to the femoral arteries, we identified significant sex-related differences in coronary plaque burden, whereas extra-coronary plaque burden was similar between genders irrespective of the vascular bed assessed.

Blood flow reversal from the external into the internal carotid artery-New insights into the hemodynamics at the carotid bifurcation

BACKGROUND

Complex blood flow patterns are a well-known phenomenon at the carotid bifurcation. However, unlike for the descending aorta, a blood flow reversal has not been detected at the carotid bifurcation, so far.

METHODS

In 17 subjects, flow patterns with focus on blood flow reversal were examined at the carotid bifurcation with vector flow imaging.

RESULTS

We found a blood flow reversal from the external carotid artery (ECA) into the internal carotid artery (ICA) in 13 of 25 (52%) carotid bifurcations. The blood flow reversal ranged 5.3 ± 1.7 mm (range 2.6-8.3 mm) distally to the beginning of the ECA and lasted 105 ± 59 ms (range 32-225 ms). The mean peak systolic velocity within the blood flow reversal was 12.5 ± 4.6 cm/s (range 5-18 cm/s).

CONCLUSION

A blood flow reversal from the ECA into the ICA during the systole is a frequent finding at the carotid bifurcation. Considering ischemic stroke, retrograde embolism from plaques in the proximal ECA into the ICA might play a role.

[Ten key messages regarding embolic stroke of undetermined source and cryptogenic stroke]

Cryptogenic stroke is a cerebral infarction where no source of cardioembolic events, no microangiopathy with lacunar infarcts, and no macroangiopathy with high-grade stenosis of the cerebral arteries can be detected. However, cryptogenic stroke is not operationally defined. The new concept of the embolic stroke of undetermined source (ESUS) is defined as a nonlacunar stroke in cerebral imaging and exclusion of significant stenosis of the cerebral arteries by angiographic or ultrasound techniques. Cardiac embolic sources must be excluded by ECG monitoring and echocardiography. At the moment, secondary prevention in patients with ESUS is performed with acetylsalicylic acid. The question of whether non-vitamin K oral anticoagulants (NOAK) are effective in these patients for secondary prevention is currently being investigated in randomized trials. The acute treatment of cryptogenic stroke/ESUS does not differ from other stroke subtypes because the stroke etiology is often not known initially, but can be identified during the course of treatment in the stroke unit.

Recent Advances in Primary and Secondary Prevention of Atherosclerotic Stroke

Atherosclerosis is a major cause of ischemic stroke that can be effectively prevented with appropriate lifestyle modifications and control of cardiovascular risk factors. Medical advances in recent years along with aggressive cardiovascular risk factor modifications have resulted in decreased recurrence rates of atherosclerotic stroke. Non-statin lipid-lowering molecules have recently shown clinical benefit and are recommended for very high-risk patients to reduce their risk of stroke. Aggressive hypertension treatment is crucial to reduce atherosclerotic stroke risk. Advances in antithrombotic treatments include combinations of antiplatelets and new antiplatelet agents in the acute phase post-stroke, which carries a high risk of recurrence. Intensive medical treatment has also limited the indications for carotid interventions, especially for asymptomatic disease. Intracranial atherosclerotic disease may provoke stroke through various mechanisms; it is increasingly recognized as a cause of ischemic stroke with advanced imaging and is best managed with lifestyle modifications and medical therapy. The diagnostic search for the vulnerable culprit atherosclerotic plaque is an area of intense research, from the level of the intracranial arteries to that of the aortic arch. Ultrasonography and novel magnetic resonance imaging techniques (high-resolution vessel-wall imaging) may assist in the identification of vulnerable atherosclerotic plaques as the underlying cause in cryptogenic or misdiagnosed non-atherosclerotic ischemic stroke. Vertebrobasilar atherosclerotic disease is less common than carotid artery disease; thus, high-quality data on effective prevention strategies are scarcer. However, aggressive medical treatment is also the gold standard to reduce cerebrovascular disease located in posterior circulation.

Voxel-by-voxel 4D flow MRI-based assessment of regional reverse flow in the aorta

BACKGROUND

Complex and reverse flow in the aorta has been implicated in aneurysm development and stroke via retrograde embolization.

PURPOSE

To evaluate global and regional differences between standard 2D plane-based and volumetric voxel-based quantification of regional forward/reverse flow, and reverse flow fraction (RFF) in the aorta.

STUDY TYPE

Retrospective.

SUBJECTS

In all, 35 subjects: 10 healthy controls (age: 57 ± 7 years, nine male), nine patients without aortic valve regurgitation (AR) (age: 63 ± 10 years, seven male), six patients with mild AR (age: 66 ± 6 years, five male), and 10 with moderate or severe AR (age: 60 ± 16 years, eight male).

FIELD STRENGTH/SEQUENCE

4D flow MRI (3T and 1.5T) was employed to acquire 3D blood flow velocities with entire thoracic aorta in all subjects.

ASSESSMENT

Data analysis included standard 2D plane-based quantification of forward/reverse flow, and RFF-plane. In addition, a new semiautomatic workflow based on 3D segmentation and extraction of an aorta centerline was developed for voxel-by-voxel visualization (forward/reverse flow and RFF-voxel maps) and quantification of regional voxel-by-voxel forward/reverse flow in the entire thoracic aorta.

STATISTICAL TESTS

Kruskal-Wallis tests were performed to test for differences between groups. A two-sample t-test or Wilcoxon rank sum test was used to compare voxel-based and plane-based results.

RESULTS

Semiautomatic plane-based analysis showed excellent agreement with standard manual plane-based analysis for net flow and RFF-plane (RFF-plane: y = 0.99x-0.0, net flow: y = 1.00x-0.21, R > 0.99, P < 0.0001). Voxel-by-voxel maps demonstrated marked regional flow reversal in the ascending aorta in all patients and RFF-voxel was significantly increased (P < 0.001) compared to RFF-plane for all four groups, with the most pronounced differences for mild AR (18.0 ± 15.2% vs. 4.7 ± 5.4%). Voxel-based flow and RFF-voxel along the aorta showed areas with marked regional flow reversal (eg, vortex flow) compared to plane-based analysis.

DATA CONCLUSION

Voxel-based analysis demonstrated regional flow reversal that was not detected by plane-based analysis.

LEVEL OF EVIDENCE

3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:1276-1286.

The association between aortic regurgitation and undetermined embolic infarction with aortic complex plaque

Background Retrograde embolism from the descending thoracic aorta is one possible cause of undetermined ischemic stroke. Significant aortic regurgitation can increase the amount of reversed flow in the thoracic aorta and thus is associated with an increased incidence of stroke. Aims This study aimed to examine the association between significant aortic regurgitation and undetermined embolic infarction with aortic complex plaques. Methods This study included 380 patients with undetermined embolic stroke who did not have abnormal flow such as atrial septal defect, patent foramen ovale determined by agitated saline bubble test, intracardiac thrombi on transesophageal echocardiography, atrial fibrillation, or small vessel stroke, cerebral artery, and carotid stenosis on the brain magnetic resonance imaging. The patients were divided into the complex aortic plaques group (n = 63), which was defined as having plaque with >4 mm in thickness, ulceration, or high mobility, and the no complex aortic plaques group (n = 317). Results Transesophageal echocardiography with a bubble study, brain MRI, and laboratory tests were performed for all subjects. Significant aortic regurgitation was more prevalent in patients with undetermined embolic stroke and complex aortic plaques than in patients without complex aortic plaques (adjusted OR = 4.981; 95% CI = 1.323-18.876, P = 0.028). In addition, the distribution of complex aortic plaques according to the severity of aortic regurgitation in patients with undetermined embolic stroke had a tendency toward the ascending thoracic aorta and proximal aortic arch. Conclusions Significant aortic regurgitation may affect undetermined embolic stroke in patients with complex aortic plaques.

Aortic atheroma as a source of stroke - assessment of embolization risk using 3D CMR in stroke patients and controls

BACKGROUND

It was our purpose to identify vulnerable plaques in the thoracic aorta using 3D multi-contrast CMR and estimate the risk of cerebral embolization using 4D flow CMR in cryptogenic stroke patients and controls.

METHODS

One hundred patients (40 with cryptogenic stroke, 60 ophthalmologic controls matched for age, sex and presence of hypertension) underwent a novel 3D multi-contrast (T1w, T2w, PDw) CMR protocol at 3 Tesla for plaque detection and characterization within the thoracic aorta, which was combined with 4D flow CMR for mapping potential embolization pathways. Plaque morphology was assessed in consensus reading by two investigators and classified according to the modified American-Heart-Association (AHA) classification of atherosclerotic plaques.

RESULTS

In the thoracic aorta, plaques <4 mm thickness were found in a similar number of stroke patients and controls [23 (57.5%) versus 33 (55.0%); p = 0.81]. However, plaques ≥4 mm were more frequent in stroke patients [22 (55.0%) versus 10 (16.7%); p < 0.001]. Of those patients with plaques ≥4 mm, seven (17.5%) stroke patients and two (3.3%) controls (p < 0.001) had potentially vulnerable AHA type VI plaques. Six stroke patients with vulnerable AHA type VI plaques ≥4 mm had potential embolization pathways connecting the plaque, located in the aortic arch (n = 3) and proximal descending aorta (n = 3), with the individual territory of stroke, which made them the most likely source of stroke in those patients.

CONCLUSIONS

Our findings underline the significance of ≥4 mm thick and vulnerable plaques in the aortic arch and descending aorta as a relevant etiology of stroke.

CLINICAL TRIAL REGISTRATION

Unique identifier: DRKS00006234 ; date of registration: 11/06/2014.

Evolution of Precision Medicine and Surgical Strategies for Bicuspid Aortic Valve-Associated Aortopathy

Bicuspid aortic valve (BAV) is a common congenital cardiac malformation affecting 1–2% of people. BAV results from fusion of two adjacent aortic valve cusps, and is associated with dilatation of the aorta, known as bicuspid valve associated aortopathy. Bicuspid valve aortopathy is progressive and associated with catastrophic clinical events, such as aortic dissection and rupture. Therefore, frequent monitoring and early intervention with prophylactic surgical resection of the proximal aorta is often recommended. However, the specific pattern of aortopathy is highly variable among patients, with different segments of the ascending aorta being affected. Individual patient risks are sometimes difficult to predict. Resection strategies are informed by current surgical guidelines which are primarily based on aortic size and growth criteria. These criteria may not optimally reflect the risk of important aortic events. To address these issues in the care of patients with bicuspid valve aortopathy, our translational research group has focused on validating use of novel imaging techniques to establish non-invasive hemodynamic biomarkers for risk-stratifying BAV patients. In this article, we review recent efforts, successes, and ongoing challenges in the development of more precise and individualized surgical approaches for patients with bicuspid aortic valves and associated aortic disease.

Association of descending thoracic aortic plaque with brain atrophy and white matter hyperintensities: The Framingham Heart Study

BACKGROUND AND AIMS

Aortic atherosclerosis is an aggregate marker of vascular risk factor exposure and has been associated with intracranial atherosclerosis and stroke. We hypothesized that atherosclerosis of the descending aorta (DAo) could be a risk marker for brain aging and injury.

METHODS

We evaluated 1527 participants (mean age 59.9 years, 53.5% women) in the Framingham Offspring cohort who underwent both aortic and brain MRI. Participants were free of clinical stroke, dementia, or other neurological illness at the time of axial MRI of the thoracic and abdominal DAo and subsequent brain MRI. We related the prevalence and burden of aortic plaque to total cerebral brain volume (TCBV) and white matter hyperintensity volume (WMHV). An additional analysis compared incidence of stroke or TIA in participants with and without DAo plaques.

RESULTS

Presence of thoracic DAo plaque (8%) was associated with decreased TCBV in sex-pooled analysis (-0.77, SE 0.25, p = 0.002, equivalent to 4.5 years of aging) and with increased WMHV only in men (0.26, SE 0.12, p = 0.032, equivalent to 6.5 years aging). We observed similar associations of DAo plaque burden with TCBV and WMHV. There were 43 strokes and 11 TIAs in prospective follow-up (median 7 years). Presence of DAo plaque was not associated with subsequent stroke or TIA.

CONCLUSIONS

In this cross-sectional community-based study, we found DAo plaque is associated with accelerated brain aging. These data underscore the potential implications of incidentally identified subclinical aortic atherosclerosis and question whether targeted intervention in these high risk individuals can modulate cognitive decline.

Importance of variants in cerebrovascular anatomy for potential retrograde embolization in cryptogenic stroke

OBJECTIVES

To test the hypothesis that variants in cerebrovascular anatomy will affect the number of patients demonstrating a plausible retrograde embolization mechanism from plaques in the descending aorta (DAo).

METHODS

Thirty-five patients (aged 63 ± 17 years) with cryptogenic stroke underwent 4D flow MRI for the assessment of aortic 3D blood flow and MR angiography for the evaluation of circle of Willis, posterior circulation, and aortic arch architecture. In patients with proven DAo plaque, retrograde embolization was considered a potential mechanism if retrograde flow extended from the DAo to a supra-aortic vessel supplying the cerebral infarct territory.

RESULTS

Retrograde embolization with matching cerebral infarct territory was detected in six (17%) patients. Circle of Willis and aortic arch variant anatomy was found in 60% of patients, leading to reclassification of retrograde embolization risk as present in three (9%) additional patients, for a total 26% of cryptogenic stroke patients.

CONCLUSION

4D flow MRI demonstrated 26% concordance with infarct location on imaging with retrograde diastolic flow into the feeding vessels of the affected cerebral area, identifying a potential etiology for cryptogenic stroke. Our findings further demonstrate the importance of cerebrovascular anatomy when determining concordance of retrograde flow pathways with vascular stroke territory from DAo plaques.

KEY POINTS

• Retrograde embolization from descending aortic plaques constitutes a plausible etiology in cryptogenic stroke. • Common variants of cerebrovascular anatomy are important in determining retrograde embolization mechanism. • Variant cerebrovascular anatomy can link retrograde flow pathways with vascular stroke territory.

4D flow MRI assessment of right atrial flow patterns in the normal heart - influence of caval vein arrangement and implications for the patent foramen ovale

AIM

To investigate atrial flow patterns in the normal adult heart, to explore whether caval vein arrangement and patency of the foramen ovale (PFO) may be associated with flow pattern.

MATERIALS AND METHODS

Time-resolved, three-dimensional velocity encoded magnetic resonance imaging (4D flow) was employed to assess atrial flow patterns in thirteen healthy subjects (6 male, 40 years, range 25-50) and thirteen subjects (6 male, 40 years, range 21-50) with cryptogenic stroke and patent foramen ovale (CS-PFO). Right atrial flow was defined as vortical, helico-vortical, helical and multiple vortices. Time-averaged and peak systolic and diastolic flows in the caval and pulmonary veins and their anatomical arrangement were compared.

RESULTS

A spectrum of right atrial flow was observed across the four defined categories. The right atrial flow patterns were strongly associated with the relative position of the caval veins. Right atrial flow patterns other than vortical were more common (p = 0.015) and the separation between the superior and inferior vena cava greater (10±5mm versus 3±3mm, p = 0.002) in the CS-PFO group. In the left atrium all subjects except one had counter-clockwise vortical flow. Vortex size varied and was associated with left lower pulmonary vein flow (systolic r = 0.61, p = 0.001, diastolic r = 0.63 p = 0.002). A diastolic vortex was less common and time-averaged left atrial velocity was greater in the CS-PFO group (17±2cm/sec versus 15±1, p = 0.048). One CS-PFO subject demonstrated vortical retrograde flow in the descending aortic arch; all other subjects had laminar descending aortic flow.

CONCLUSION

Right atrial flow patterns in the normal heart are heterogeneous and are associated with the relative position of the caval veins. Patterns, other than 'typical' vortical flow, are more prevalent in the right atrium of those with cryptogenic stroke in the context of PFO. Left atrial flow patterns are more homogenous in normal hearts and show a relationship with flow arising from the left pulmonary veins.

Aortic Atherosclerosis Determines Increased Retrograde Blood Flow as a Potential Mechanism of Retrograde Embolic Stroke

BACKGROUND

Retrograde brain embolization from complex plaques of the proximal descending aorta (DAo) has been identified as a new potential mechanism of stroke. Our purpose was to identify predictors of increased retrograde aortic blood flow indicating an elevated risk of brain embolization from the DAo.

METHODS

A total of 485 patients with acute ischemic stroke were prospectively included and underwent transesophageal echocardiography. Blood flow velocities in the proximal DAo were studied using 2D pulse-wave Doppler ultrasound. Velocity-time integrals (VTI) were calculated for antegrade and retrograde velocity directions. The ratio (VTIretrograde/VTIantegrade) was used to estimate retrograde flow extent. Associations between patient demographics, cardiovascular risk factors, echocardiographic parameters, and VTIratio were analyzed using multivariate linear regression.

RESULTS

Retrograde blood flow in the DAo occurred in all patients. Velocity profiles in the proximal DAo were as follows (mean ± SD): VTIantegrade = 21.1 ± 6.5, VTIretrograde = 11.0 ± 3.6, and VTIratio = 0.54 ± 0.16. Diameter (r = 0.25, p < 0.001), presence of complex plaques (r = 0.12, p = 0.007), and reduced strain of the DAo (r = -0.23, p < 0.001) had significant partial effects in a predictor model based on predefined variables, which predicted 26% (adjusted R2 = 0.26) of the variance in VTIratio. A unit increase in the DAo diameter was associated with a 2% increase in VTIratio (95% CI 1-2.8%, p < 0.001). Presence of complex plaques increased VTIratio by 7% (95% CI 2-13%, p = 0.007) and an increase in strain by 0.1 indicated a decrease in VTIratio by about 11% (95% CI 6.2-15.5%, p < 0.001). Complex atheroma was found in the proximal DAo of 79 subjects, of which 40 (50.6%) had a VTIratio above average (VTIratio ≥0.54) compared to 87 of 261 (33.3%) patients without any complex plaques (p < 0.001). Twenty-five of 79 (31.7%) patients with complex DAo plaques had a VTIratio ≥0.60, which indicates a high likelihood of retrograde pathline length of ≥3 cm and thus increased risk of retrograde cerebral embolization. Stroke etiology of those 25 patients was determined in 13 and cryptogenic in 12 cases.

CONCLUSIONS

Retrograde blood flow in the DAo was found in all stroke patients. However, it increased further in patients with concomitant complex plaques, low strain, and/or large aortic diameter, that is, in those with atherosclerosis of the DAo. Accordingly, such patients may be predisposed to retrograde embolization in case of occurrence of a complex plaque in proximity to a brain-supplying artery.

Year in review: bicuspid aortopathy

PURPOSE OF REVIEW

This article outlines the key research contribution to bicuspid aortic valve (BAV) aortopathy over the past 18 months.

RECENT FINDINGS

Investigators have further defined the current gaps in knowledge and the scope of the clinical problem of BAV aortopathy. Support for aggressive resection strategies is waning as evidence mounts to suggest that BAV is not similar to genetic connective tissue disorders with respect to aortic risks. The role of cusp fusion patterns and valve-mediated hemodynamics in disease progression is a major area of discovery. Molecular and cellular mechanisms remain elusive and contradictory.

SUMMARY

BAV aortopathy is a major public health problem that remains poorly understood. New insights on valve-mediated hemodynamics using novel imaging modalities may lead to more individualized resection strategies and improved clinical guidelines.

Advanced flow MRI: emerging techniques and applications

Magnetic resonance imaging (MRI) techniques provide non-invasive and non-ionising methods for the highly accurate anatomical depiction of the heart and vessels throughout the cardiac cycle. In addition, the intrinsic sensitivity of MRI to motion offers the unique ability to acquire spatially registered blood flow simultaneously with the morphological data, within a single measurement. In clinical routine, flow MRI is typically accomplished using methods that resolve two spatial dimensions in individual planes and encode the time-resolved velocity in one principal direction, typically oriented perpendicular to the two-dimensional (2D) section. This review describes recently developed advanced MRI flow techniques, which allow for more comprehensive evaluation of blood flow characteristics, such as real-time flow imaging, 2D multiple-venc phase contrast MRI, four-dimensional (4D) flow MRI, quantification of complex haemodynamic properties, and highly accelerated flow imaging. Emerging techniques and novel applications are explored. In addition, applications of these new techniques for the improved evaluation of cardiovascular (aorta, pulmonary arteries, congenital heart disease, atrial fibrillation, coronary arteries) as well as cerebrovascular disease (intra-cranial arteries and veins) are presented.

Evaluating the Atrial Myopathy Underlying Atrial Fibrillation: Identifying the Arrhythmogenic and Thrombogenic Substrate

Atrial disease or myopathy forms the substrate for atrial fibrillation (AF) and underlies the potential for atrial thrombus formation and subsequent stroke. Current diagnostic approaches in patients with AF focus on identifying clinical predictors with the evaluation of left atrial size by echocardiography serving as the sole measure specifically evaluating the atrium. Although the atrial substrate underlying AF is likely developing for years before the onset of AF, there is no current evaluation to identify the preclinical atrial myopathy. Atrial fibrosis is 1 component of the atrial substrate that has garnered recent attention based on newer MRI techniques that have been applied to visualize atrial fibrosis in humans with prognostic implications regarding the success of treatment. Advanced ECG signal processing, echocardiographic techniques, and MRI imaging of fibrosis and flow provide up-to-date approaches to evaluate the atrial myopathy underlying AF. Although thromboembolic risk is currently defined by clinical scores, their predictive value is mediocre. Evaluation of stasis via imaging and biomarkers associated with thrombogenesis may provide enhanced approaches to assess risk for stroke in patients with AF. Better delineation of the atrial myopathy that serves as the substrate for AF and thromboembolic complications might improve treatment outcomes. Furthermore, better delineation of the pathophysiologic mechanisms underlying the development of the atrial substrate for AF, particularly in its earlier stages, could help identify blood and imaging biomarkers that could be useful to assess risk for developing new-onset AF and suggest specific pathways that could be targeted for prevention.

Contributing Mechanisms of Aortic Atheroma in Ischemic Cerebrovascular Disease

In recent years, the correlation between aortic atheroma (AA) and the occurrence and recurrence of ischemic cerebrovascular disease (ICVD) has attracted much attention, but the contributory mechanisms remain controversial. This review analyzes related research on the roles of AA in ICVD, and demonstrates the correlation between the formation and development of AA and abnormal metabolism, inflammation, hemodynamic changes, and other contributory factors. The presence of complex aortic plaque (CAP) in the ascending aorta and aortic arch increases the risk of cerebral embolism and degree of injury, while the association between CAP in the descending aorta and cerebral embolism remains ambiguous. AA also functions as an indicator of atherosclerosis burden as well as hypercoagulability, which may further increase the risk of ICVD. Further study on the relationship of AA to ICVD will improve diagnosis and treatment in clinical practice.

Cardiovascular causes of emergency neurology presenting to an ICU

Stroke or transient ischemic attacks (TIA) represent an urgent clinical entity that is not limited only to elderly patients. The underlying causes of stroke and TIA are diverse, with those of cardiovascular origin being among the most prominent. This review seeks to elucidate some of the most important aspects of the disease in the context of emergency and critical care practice.