Lung/heart uptake ratio (L/H R) in 201T1 myocardial perfusion scan is a reliable marker for long-term prognosis in patients with coronary artery disease. However, the value of L/H R in 99mTc-MIBI myocardial perfusion scan is controversial in
determining
the prognosis and severity of the coronary artery disease. The purpose of this study was to determine the clinical implications of L/H R in 99mTc-MIBI myocardial perfusion scan.
Forty five patients who received 99mTc-MIBI myocardial perfusion scan were divided into control group and coronary artery disease (CAD) group by their clinical findings, EKGs, and 99mTc-MIBI myocardial perfusion scans. Twenty five patients in CAD
group
were divided into ischemic group and infarct group according to their results from 99mTc-MIBI myocardial perfusion scan. L/H R was calculated on the anterior planar view, 60 minutes after infusion of dipyridamole. Two regions of interest (ROI)
were
placed on the left lung area 8 pixel above the left ventricle and on the myocardial area which had the highest radioactivity.
In the control group, there were no significant differences of L/H R according to sex and age. No significant difference of L/H R was found between the control and CAD group (0.26±0.06, 0.29±0.05, p>0.05). In the CAD group, there was also no
significant difference of L/H R between the ischemic group and infarct group (0.29±0.07, 0.30±0.04, p>0.05). L/H R in CAD group did not show correlations with the defect area of stress polar map (r=0.18, p>0.05) and with the sum of severity
weighted
extent score or reversibility score which represent severity and extent of myocardial perfusion defect area in stress (r=0.18, p>0.05).
We conclude that it is difficult to use L/H R as a marker for severity of CAD in dipyridamole 99mTc-MIBI myocardial perfusion scan.
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