Impact of oxygen extraction fraction on long-term prognosis in patients with reduced blood flow and vasoreactivity because of occlusive carotid artery disease.
BACKGROUND
Reduced cerebral blood flow and cerebrovascular reactivity to acetazolamide (type 3 ischemia) is believed as an independent predictor for subsequent ischemic stroke in patients with occlusive carotid artery diseases. However, recent studies have shown that type 3 patients can be divided into 2 pathophysiologically different subgroups as follows: those with elevated OEF and those with normal OEF. This study was aimed to clarify whether there is a difference in the prognosis between patients with type 3 and elevated OEF and those with type 3 but normal OEF.


METHODS
Twenty type 3 patients were enrolled in this prospective, longitudinal cohort study. Hemodynamic and metabolic parameters were quantitatively determined by (15)O-gas PET. All of them were medically treated.


RESULTS
Oxygen extraction fraction was elevated in 9 patients but was normal in other 11. During an average follow-up period of 45.6 months, 3 of 9 patients with type 3 and elevated OEF developed ipsilateral ischemic stroke. The annual risk was 10.6%. The location and shape of cerebral infarction strongly suggested a key role of hemodynamic compromise in their recurrence. On the other hand, no subsequent stroke occurred in none of 11 patients with type 3 but normal OEF. There was a statistically significant difference in the incidence of ipsilateral ischemic stroke between 2 groups (P = .0303).


CONCLUSIONS
Type 3 patients may be categorized into 2 subgroups as follows: those with elevated OEF and higher stroke risk and those with normal OEF and lower stroke risk, although larger number of subjects should be analyzed.
Hokari
Masaaki
M
Department of Neurosurgery, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo 060-8638, Japan.
Kuroda
Satoshi
S
Shiga
Tohru
T
Nakayama
Naoki
N
Tamaki
Nagara
N
Iwasaki
Yoshinobu
Y
D000086:Acetazolamide; D000368:Aged; D002545:Brain Ischemia / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology; D002257:Carbonic Anhydrase Inhibitors; D016893:Carotid Stenosis / Q000150:complications / Q000503:physiopathology*; D002536:Cerebral Arteries / Q000378:metabolism / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology*; D010104:Oxygen Radioisotopes; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D012307:Risk Factors; D055502:Secondary Prevention; D020521:Stroke / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology*; D015899:Tomography, Emission-Computed, Single-Photon
D002257:Carbonic Anhydrase Inhibitors; D010104:Oxygen Radioisotopes; D000086:Acetazolamide