title: Prevalence of potential retrograde embolization pathways in the proximal descending aorta in stroke patients and controls.
abstract: BACKGROUND
  Retrograde diastolic blood flow in the proximal descending aorta (DAo) connecting complex plaques (≥4 mm thick) with brain-supplying supra-aortic arteries may constitute a source of stroke. Yet, data only from high-risk populations (cryptogenic stroke patients with aortic atheroma≥3 mm) regarding the prevalence of this potential stroke mechanism are available. We aimed to quantify the frequency of this mechanism in unselected patients with cryptogenic stroke after routine diagnostics and controls without a history of stroke.
  
  
  METHODS
  88 patients (67 stroke patients, 21 cardiac controls) were prospectively included. 3D T1-weighted bright blood MRI of the aorta was applied for the detection of complex DAo atheroma. ECG-triggered and navigator-gated 4D flow MRI allowed measuring time-resolved 3D blood flow in vivo. Potential retrograde embolization pathways were defined as the co-occurrence of complex plaques and retrograde blood flow in the DAo reaching the outlet of (a) the left subclavian artery, (b) the left common carotid artery, or/and (c) the brachiocephalic trunk. The frequency of these pathways was analyzed by importing 2D plaque images into 3D blood flow visualization software.
  
  
  RESULTS
  Complex DAo plaques were more frequent in stroke patients (44 in 31/67 patients (46.3%) vs. 5 in 4/21 controls (19.1%); p=0.039), especially in older patients (29/46 (63.04%) patients≥60 years of age with 41 plaques vs. 2/21 (9.14%) patients<60 years of age with 3 plaques; p<0.001). Contrary to our assumption, retrograde diastolic blood flow at the DAo occurred in every patient irrespective of the existence of plaques with a similar extent in both groups (26±14 vs. 32±18 mm; p=0.114). Therefore, only the higher prevalence of complex DAo plaques in stroke patients resulted in a three times higher frequency of potential retrograde embolization pathways compared to controls (22/67 (32.8%) vs. 2/21 (9.5%) controls; p=0.048).
  
  
  CONCLUSIONS
  This study revealed that retrograde flow in the descending aorta is a common phenomenon not only in stroke patients. The existence of potential retrograde embolization pathways depends mainly on the occurrence of complex plaques in the area 0 to ∼30 mm behind the outlet of the left subclavian artery, which is exposed to flow reversal. In conclusion, we have shown that the frequency of potential retrograde embolization pathways was significantly higher in stroke patients suggesting that this mechanism may play a role in retrograde brain embolism.
authors.affiliation: Department of Neurology, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Wehrum
authors.forename: Miriam
authors.initials: M
authors.lastname: Kams
authors.forename: Christoph
authors.initials: C
authors.lastname: Strecker
authors.forename: Iulius
authors.initials: I
authors.lastname: Dragonu
authors.forename: Felix
authors.initials: F
authors.lastname: Günther
authors.forename: Annette
authors.initials: A
authors.lastname: Geibel
authors.forename: Johann
authors.initials: J
authors.lastname: Drexl
authors.forename: Anja
authors.initials: A
authors.lastname: Hennemuth
authors.forename: Martin
authors.initials: M
authors.lastname: Schumacher
authors.forename: Bernd
authors.initials: B
authors.lastname: Jung
authors.forename: Andreas
authors.initials: A
authors.lastname: Harloff
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001013:Aorta, Thoracic / Q000473:pathology* / Q000503:physiopathology; D001018:Aortic Diseases / Q000453:epidemiology* / Q000473:pathology / Q000503:physiopathology; D016022:Case-Control Studies; D004617:Embolism; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D058226:Plaque, Atherosclerotic / Q000453:epidemiology* / Q000473:pathology / Q000503:physiopathology; D015995:Prevalence; D011446:Prospective Studies; D012039:Regional Blood Flow; D020521:Stroke / Q000453:epidemiology*