Detection of viable myocardium by low dose of dobutamine cine MR imaging in miniswine.
OBJECTIVE
To evaluate the diagnostic value of dobutamine stress magnetic resonance imaging (MRI) for myocardial viability.


METHODS
Ten male miniswines underwent left ventriculography and coronary angiography, followed by stenosis of the left circumflex coronary artery (LCX) using ameroid constrictor. More than one month later, left ventriculography and coronary angiography were performed again, followed by cine-MRI at rest and during stress with incremental dose of dobutamine 5 - 20 micro g.kg(-1).min(-1). Traditional and/or breath-hold cine-MRI were used to evaluate regional left ventricular wall motion, corresponding to basal, midventricular and apical short-axis tomograms. Regional wall motion score index (WMSI) was calculated. The miniswines were finally sacrificed for pathological examination. Triphenyl tetrazolium chloride (TTC) delineated myocardial infarction. Microscopy was used to identify myocardial cellular changes.


RESULTS
One pig died, one pig suffered from aneurysm and another showed no negative findings. The other seven pigs were found with hypokinetic (n = 4) or akinetic (n = 3) myocardial regions related to stenosed LCX. Their mean WMSI at rest for the lateral and posteroinferior walls (ischemic regions) of the left ventricle was 2.27 +/- 0.32, as compared with 1.00 +/- 0.00 (P < 0.01) for the corresponding nonischemic anteroseptal regions. Further, the mean WMSI for the ischemic regions was 2.27 +/- 0.32 at rest compared with 1.40 +/- 0.39 (P < 0.01) at the dose of dobutamine 5 micro g.kg(-1).min(-1). However, the mean WMSI at the doses of dobutamine 10 and 20 micro g.kg(-1). min(-1) were 1.70 +/- 0.76 and 1.75 +/- 0.83, respectively, with no significant difference as compared with the mean WSCI at rest (P > 0.05). The pathologic examination showed viable myocardium at the ischemic regions.


CONCLUSIONS
Low-dose dobutamine (5 micro g.kg(-1).min(-1)) recovers hypokinetic or akinetic myocardial regions, and dobutamine stress MRI can be used to detect myocardial viability.
Lu
Minjie
M
Department of Radiology, Experimental Surgery, Department of Pathology, Cardiovascular Institute & Fuwai Hospital, CAMS & PUMC, Beijing 100037, China.
Zhao
Shihua
S
Wei
Yunqing
Y
Wang
Cheng
C
Jiang
Shiliang
S
Huang
Lianjun
L
Zhang
Yan
Y
Mou
Feng
F
Meng
Liang
L
Ruan
Yingmao
Y
D000818:Animals; D004280:Dobutamine; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D013552:Swine; D013556:Swine, Miniature; D016277:Ventricular Function, Left
D004280:Dobutamine