Jf. Debatin et al., MR CHARACTERIZATION OF BLOOD-FLOW IN NATIVE AND GRAFTED INTERNAL MAMMARY ARTERIES, Journal of magnetic resonance imaging, 3(3), 1993, pp. 443-450
In the postoperative patient with anginal symptoms, differentiation be
tween bypass graft compromise and nonischemic causes has until now bee
n accomplished only by means of x-ray angiography. A noninvasive test
is clearly desirable. The authors used a cine phase-contrast (PC) magn
etic resonance (MR) imaging technique to characterize blood flow in na
tive and grafted internal mammary arteries (IMAs). Ten volunteers and
15 patients who had recently undergone IMA coronary artery bypass graf
ting were imaged. Cine PC MR imaging was performed in the transaxial p
lane at the level of the pulmonary artery bifurcation. Flow in both IM
As was quantified and expressed as a percentage of cardiac output meas
ured in the ascending aorta. In the 15 patients, flow analysis was per
formed in both the native and grafted IMAs. In the volunteers, IMA blo
od flow ranged from 2. 1 % to 4.3 % of cardiac output on the left (mea
n, 3.5%) and 2. 1 % to 5. 1 % (mean, 3.5%) on the right. There was con
siderable intersubject variability, with coefficients of variation of
10.7 % for the left and 12.3 % for the right IMA. Intrasubject variabi
lity was limited, with estimated common standard deviations of 0.45 %
of cardiac output (range, 0.2%-1.1 %) for the left and 0.39% (range, 0
.1%-0.6%) for the right IMA. Flow in grafted IMAs was identified in 13
of 15 patients. In one of two patients without demonstrable IMA graft
flow, cardiac catheterization confirmed lack of flow. IMA graft flow
varied from 28 to 164 mL/min (mean, 80.3 ml/min). This study shows the
feasibility of using cine PC MR imaging as a quantitative method of e
valuating blood flow in IMA coronary artery bypass grafts.