Complex Plaques in the Proximal Descending Aorta: An Underestimated Embolic Source of Stroke

Abstract

and much work needs to be done to identify the causes of regional variability. Finally, it needs to be emphasized that "fistula first" does not mean "fistula only." Patients with poor likelihood of maturation of a fistula, or a short life expectancy, may be better candidates for a graft.Complex Plaques in the Proximal Descending Aorta: An Underestimated Embolic Source of Stroke Harloff A, Simon J, Brendecke S, et al. Stroke 2010;41:1145-50. Conclusion: Retrograde flow from complex descending aorta plaques is a potential source of emboli to all brain territories.Summary: Complex aortic plaques are defined as Ն4 mm in thickness, or those associated with ulceration or that have mobile thrombi. Such plaques are considered a significant source of stroke. When such plaques are located in the ascending aorta or the aortic arch, embolization can be through antegrade flow from the aorta into a major cerebral vessel. However, the incidence of complex plaques is highest in the proximal descending aorta. Plaques in this location have only previously been considered a source of stroke in the setting of severe aortic valve insufficiency resulting in retrograde flow in the aorta during diastole. However, it now appears that diastolic retrograde flow in the descending thoracic aorta may be common in patients with atherosclerosis and therefore serve as a potentially overlooked mechanism of stroke (Svedlund S, et al, Cerebrovasc Dis 2009;27:22-8).The authors hypothesize that retrograde flow in the proximal descending thoracic aorta has the potential to reach all the supra-aortic arteries and, thus, may be a previously underappreciated source of stroke in the setting of a complex descending aorta plaque. They studied 94 consecutive acute stroke patients who had aortic plaques Ն3 mm in thickness as determined by transesophageal echocardiography. All subjects underwent magnetic resonance imaging (MRI) to localize complex plaques and to measure timeresolved 3-dimensional (3D) blood flow within the aorta. The 3D visualization was then used to determine if diastolic retrograde flow connected plaque location with origins of the left subclavian, left common carotid, or innominate artery. If retrograde flow associated with a complex descending thoracic aortic plaque reached a supra-aortic vessel that supplied the territory of an MRI-determined acute embolic retinal or cerebral infarction, the distal thoracic aortic plaque was considered a possible embolic source for the stroke.Decreasing heart rate was correlated with increasing flow reversal to the aortic arch (P Ͻ .02). Retrograde flow associated with complex proximal descending aortic plaques reached the left subclavian artery in 58.5% of cases, the left common carotid artery in 24.5%, and the brachiocephalic artery in 13.8%. Stroke etiology was determined in 57 of the 94 patients in the study and was not determined in the remaining 37 patients, so-called cryptogenic stroke. Potential embolization from a descending thoracic aortic plaque was identified in 19 of 57 patients (33.3%) wi...

Non‐contrast enhanced MR angiography: Physical principles

“…The 4D flow technique has been applied to the measurement of aortic pulse wave velocity (65) and wall shear stress (66) for the purposes of identifying potential emboli from high-risk atherosclerotic plaque (67). Figure 7 shows an example of 4D flow analysis of atherosclerotic plaque in the aorta.…”

Complex Atheromatous Plaques in the Descending Aorta and the Risk of Stroke

“…2,3 Moreover, aortic plaques situated in the descending thoracic aorta are often overlooked and may be neglected as a potential mechanism of cerebral embolism through retrograde aortic flow. [4][5][6] Interestingly, 3-dimensional and 4-dimensional MRI data via image fusion demonstrated that emboli from complex plaques in the descending aorta reached the left subclavian artery and common carotid artery in 67% and 25% of evaluated cases. In addition, retrograde embolism from the descending aorta was postulated as the only probable cause of retinal or cerebral infarction in 24% of patients with cryptogenic stroke.…”

Intracranial 4D Flow MRI: Toward Individualized Assessment of Arteriovenous Malformation Hemodynamics and Treatment-Induced Changes

“…Previous studies have used similar approaches to analyze 3D blood flow distributions in patients with high-risk aortic plaques. 25 In consensus reading, 2 observers identified the number of arterial feeders and draining veins visible in the 4D flow data. Feeding/draining velocities in each vessel were visually graded as 0 (low flow Ͻ25 cm/s), 1 (medium flow Ͻ50 cm/s), and 2 (high flow Ͼ50 cm/s).…”