In vivo MR angiography and velocity measurement in mice coronary arteries at 9.4 T: assessment of coronary flow velocity reserve.
OBJECTIVE
To demonstrate the feasibility of coronary magnetic resonance (MR) angiography in living mice and to evaluate a dynamic MR angiographic method for coronary flow measurement at 9.4-T field strength.


METHODS
This study was conducted according to European law and was in full compliance with National Institutes of Health recommendations for animal care and a local institutional animal care committee. Mice were anesthetized by using isoflurane. First, time-of-flight MR angiography was performed in 10 mice to measure coronary diameters at 80-mum isotropic resolution. Second, left coronary artery (LCA) velocity measurements were performed at seven cardiac phases in nine other mice to assess the velocity curve profile. Third, coronary velocities were measured at the middiastolic phase in 13 mice at rest and during adenosine-induced hyperemia to calculate coronary flow velocity reserve (CFVR). The Pearson coefficient compared the correlation between isoflurane dose and CFVR. Paired t tests compared R-R intervals and respiratory rates between rest and hyperemia.


RESULTS
Proximal diameters were, respectively, 404 mum +/- 34 [standard deviation] and 259 mum +/- 22 for the LCAs and the right coronary arteries, which were in accordance with reported values. The velocity curve profile throughout the cardiac cycle was similar to values from the literature. Baseline and hyperemic velocities were, respectively, 19.0 cm/sec +/- 4.4 and 33.7 cm/sec +/- 4.7 (P<.001), resulting in a CFVR of 1.77 +/- 0.19. CFVR did not correlate with isoflurane dose (r = 0.05, P = .88). R-R intervals shortened by 2.5% during hyperemia (P = .04). Respiratory rates showed no difference between rest and hyperemia (P = .39).


CONCLUSIONS
High-spatial-resolution three-dimensional coronary MR angiography is feasible in living mice. Dynamic MR angiography depicts coronary velocity changes throughout the cardiac cycle and between rest and maximum hyperemia, providing a tool for CFVR assessment.
Cochet
Hubert
H
Unit of Thoracic and Cardiovascular Imaging, Hôpital Cardiologique du Haut-Lévêque, CHU Bordeaux, avenue Magellan, 33604 Pessac, France. hcochet@wanadoo.fr
Montaudon
Michel
M
Laurent
François
F
Calmettes
Guillaume
G
Franconi
Jean-Michel
JM
Miraux
Sylvain
S
Thiaudière
Eric
E
Parzy
Elodie
E
D000241:Adenosine / Q000494:pharmacology; D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology*; D003331:Coronary Vessels / Q000502:physiology*; D005240:Feasibility Studies; D005260:Female; D018810:Magnetic Resonance Angiography / Q000379:methods*; D051379:Mice; D008810:Mice, Inbred C57BL; D015203:Reproducibility of Results; D014665:Vasodilator Agents / Q000494:pharmacology
D014665:Vasodilator Agents; D000241:Adenosine