Evaluation of cuff-induced ischemia in the lower extremity by magnetic resonance oximetry.
OBJECTIVE
The aim of this study was to evaluate vascular function in the lower extremities by making direct time-course measurement of oxygen saturation in the femoral/popliteal arteries and veins during cuff-induced reactive hyperemia with magnetic resonance imaging-based oximetry.


BACKGROUND
Magnetic resonance imaging-based oximetry is a new calibration-free technique taking advantage of the paramagnetic nature of blood that depends on the volume fraction of deoxyhemoglobin in red blood cells.


METHODS
We compared post-occlusive blood oxygenation time-course of femoral/popliteal vessels in: 1) young healthy subjects (YH) (n = 10; mean ankle-brachial index [ABI] 1.0 +/- 0.1, mean age 30 +/- 7 years); 2) peripheral arterial disease (PAD) patients (n = 12; mean ABI 0.6 +/- 0.1, mean age 71 +/- 9 years); and 3) age-matched healthy control subjects (AHC) (n = 8; mean ABI 1.1 +/- 0.1, mean age 68 +/- 9 years). Blood oxygenation was quantified at 3.0-T field strength with a field mapping pulse sequence yielding the magnetic susceptibility difference between blood in the vessels and surrounding muscle tissue from which the intravascular blood oxygen saturation is computed as %HbO(2).


RESULTS
Significantly longer washout time (42 +/- 16 s vs. 14 +/- 4 s; p < 0.0001) and lower upslope (0.60 +/- 0.20 %HbO(2)/s vs. 1.32 +/- 0.41 %HbO(2)/s; p = 0.0008) were observed for PAD patients compared with healthy subjects (YH and AHC combined). Furthermore, greater overshoot was observed in YH than in AHC (21 +/- 8 %HbO(2) vs. 10 +/- 5 %HbO(2); p = 0.0116).


CONCLUSIONS
Post-occlusive transient changes in venous blood oxygenation might provide a new measure of vascular competence, which was found to be reduced in subjects with abnormal ABI, manifesting in prolonged recovery during the early phase of hyperemia.
Langham
Michael C
MC
Department of Radiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA.
Floyd
Thomas F
TF
Mohler
Emile R
ER
Magland
Jeremy F
JF
Wehrli
Felix W
FW
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005263:Femoral Artery; D005268:Femoral Vein; D006801:Humans; D007511:Ischemia / Q000503:physiopathology*; D035002:Lower Extremity / Q000098:blood supply*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010092:Oximetry / Q000379:methods*; D011150:Popliteal Artery; D011152:Popliteal Vein