2D-spatially-selective real-time magnetic resonance imaging for the assessment of microvascular function and its relation to the cardiovascular risk profile.
BACKGROUND
While local endothelial dysfunction of conduit arteries is well recognized as an early step in atherogenesis, contradictory observations are reported with regard to alterations in the microcirculation and their association with cardiovascular risk factors (RFs). A real-time MR approach was developed to investigate the relationship between the RFs profile and microcirculatory alterations assessed as impairment of reactive hyperemic flow in the leg circulation.


METHODS
The MR technique was applied to patients (n = 17, Pats1) with 1.8 +/- 0.8 RFs but without peripheral arterial occlusive disease (PAD), to age-matched healthy controls (n = 13, Con1), to young controls (n = 12, 23 +/- 4 y), and to patients with RFs and PAD (n = 8, Pats2).


RESULTS
Superficial femoral artery (SFA) peak hyperemic flow in Pats1 was reduced vs Con1 (24.6 +/- 4.2 vs 30.4 +/- 7.3 mL min-1 100 mL-1 calf tissue, p < 0.02), and minimal vascular resistance increased incrementally with the number of RFs and with Framingham and Procam risk scores. Flow-mediated vasodilation (FMD) of the SFA was blunted in both Pats1 and Con1 (-0.5 +/- 3.4% and +0.6 +/- 3.2%, respectively, both ns vs 0). In young controls, peak hyperemic flow (30.1 +/- 3.3 mL min-1. 100 mL-1) and endothelium-independent vasodilation (9.2 +/- 10.0%) were preserved, while FMD was minimal (2.0 +/- 5.9%,p < 0.02 vs endothelium-independent vasodilation). In Pats2, peak hyperemic flow was severely reduced (12.2 +/- 3.6 mL min-1 100 mL-1, p < 0.0003 vs Con1 and Pats1), and both FMD and endothelium-independent vasodilation were absent.


CONCLUSIONS
Reactive hyperemic flow in the SFA, reflecting microcirculatory function of the lower limb, gradually decreases with increasing cardiovascular risk suggesting a role for microvascular dysfunction in atherogenesis. The presented MR approach might become a valuable tool to study (micro)-vascular pathophysiology.
Schwitter
Juerg
J
Division of Cardiology and CardioVascular Center, University Hospital Zurich, Zurich, Switzerland. juerg.schwitter@usz.ch
Oelhafen
Markus
M
Wyss
Barbara M
BM
Kozerke
Sebastian
S
Amann-Vesti
Beatrice
B
Lüscher
Thomas F
TF
Boesiger
Peter
P
D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D001783:Blood Flow Velocity; D002318:Cardiovascular Diseases / Q000503:physiopathology*; D016022:Case-Control Studies; D003199:Computer Systems; D004730:Endothelium, Vascular / Q000503:physiopathology; D005260:Female; D005263:Femoral Artery / Q000503:physiopathology; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology; D007866:Leg / Q000098:blood supply; D008279:Magnetic Resonance Imaging; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D015588:Observer Variation; D011673:Pulsatile Flow; D012039:Regional Blood Flow; D015203:Reproducibility of Results; D012107:Research Design; D018570:Risk Assessment; D012307:Risk Factors; D013318:Stroke Volume; D014655:Vascular Resistance; D014664:Vasodilation
D015415:Biomarkers