Complex Plaques in the Proximal Descending Aorta

Abstract

Background and Purpose-To investigate the incidence of retrograde flow from complex plaques (Ն4-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 Ն3-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 (PϽ0.02) 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. (Stroke. 2010;41:1145-1150.)Key Words: acute stroke Ⅲ aorta Ⅲ atherosclerosis Ⅲ magnetic resonance Ⅲ pathogenesis C omplex aortic plaques defined as Ն4-mm-thick, ulcerated or containing mobile thrombi are considered a major source of stroke. 1 Although their incidence is highest in the proximal descending aorta (DAo), such plaques are only considered an embolic source of stroke in the unlikely coincidence of severe aortic valve insufficiency causing retrograde flow and embolization in case of plaque rupture. 1,2 However, there is growing evidence that diastolic retrograde flow in the DAo may be a frequent phenomenon in the presence of atherosclerosis and thus an overlooked mechanism of retrograde embolization in stroke patients. Oscillating thrombus mobility 3 and Doppler flow curves in the DAo in transesophageal echocardiography (TEE) indirectly proved the existence of flow reversal. 4 In contrast to TEE, flowsensitive 4-dimensional MRI permits the precise analysis of individual 3-dimensional flow patterns at the site of complex DAo plaques. [5][6][7] Moreover, it allows for a more reliable detection and characterization of aortic plaques compared to TEE. 8,9 In this context, retrograde embolization from complex DAo plaques was recently described as a proof-ofprinciple and constituted the only proba...

Velocity encoded cardiovascular magnetic resonance to assess left atrial appendage emptying

“…Passive LAA emptying is primarily related to a suction effect of passive LA emptying in early diastole in SR as well as in AF [13,14]. In SR, the e-wave velocity is a surrogate parameter for passive LAA emptying and is typically lower than active emptying velocities (Figure 3A) [14].…”

“…In SR, the e-wave velocity is a surrogate parameter for passive LAA emptying and is typically lower than active emptying velocities (Figure 3A) [14]. Being of little relevance in SR under physiological conditions, passive LAA emptying gains importance in situations with impaired active LAA emptying such as atrial stunning [3,4,13,14]. In patients with AF, LAA emptying is inherently passive.…”

“…LAA a-wave velocity is a surrogate parameter for active LAA emptying [16,18]. A reduced a-wave velocity can be present in SR as transient stunning after cardioversion or AF ablation, but is also related to ageing [3,13,16,20]. However, since TEE is an invasive procedure, data are limited on time course, potential predictors and modulators of LAA stunning after catheter ablation of AF [16,18].…”

“…Such a protocol could incorporate information on LA dimensions and function, LAA emptying, LA fibrosis as well as on aortic plaque morphology and flow characteristics to improve current risk stratification for stroke [8-13]. Second, VENC-CMR LAA flow measurements could be combined with MR angiographies of the LA and pulmonary veins that are frequently performed in clinical routine before AF ablation procedures [25].…”

“…Furthermore, plaques with retrograde flow in the descending aorta can be assessed by CMR as a potential non-cardiac source for cerebral embolism [12,13]. Velocity-encoded (VENC) CMR serves as the reference method for the quantification of intracardiac flow, indicating a potential use for measurements of LAA flow as a component of a comprehensive CMR protocol in patients at risk for stroke [14].…”