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

Cerebrovasc Dis. 2017;43(3-4):132-138. doi: 10.1159/000455053. Epub 2017 Jan 4.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aorta / diagnostic imaging
  • Aorta / physiopathology*
  • Aortic Diseases / complications*
  • Aortic Diseases / diagnostic imaging
  • Aortic Diseases / physiopathology
  • Atherosclerosis / complications*
  • Atherosclerosis / diagnostic imaging
  • Atherosclerosis / physiopathology
  • Blood Flow Velocity
  • Echocardiography, Doppler, Pulsed
  • Echocardiography, Transesophageal
  • Female
  • Humans
  • Intracranial Embolism / diagnostic imaging
  • Intracranial Embolism / etiology*
  • Intracranial Embolism / physiopathology
  • Linear Models
  • Male
  • Middle Aged
  • Multivariate Analysis
  • Plaque, Atherosclerotic
  • Prospective Studies
  • Regional Blood Flow
  • Risk Factors
  • Stroke / diagnostic imaging
  • Stroke / etiology*
  • Stroke / physiopathology