Correlation of pharmacological ^99mTc-sestamibi myocardial perfusion imaging with poststenotic coronary flow reserve in patients with angiographically intermediate coronary artery stenoses

Background: The physiological assessment of angiographically intermediate-severity stenoses remains problematic. Functional measurements of poststenotic intracoronary Doppler coronary flow reserve can be performed in humans but have not been correlated with hyperemic myocardial perfusion imaging or angiographic data in this patient population. Methods and Results: Thirty-three patients undergoing diagnostic quantitative coronary angiography (QCA) for assessment of intermediate-severity coronary artery disease (mean QCA percent diameter stenosis, 56±14%) were studied. Proximal and distal poststenotic Doppler coronary flow velocities were measured (left anterior descending coronary artery, 16; right coronary artery, 10; left circumflex artery, 7 patients) before and during peak maximal hyperemia with intracoronary adenosine (8 to 12 μg). Intravenous pharmacological stress (adenosine, 20 patients; dipyridamole, 13 patients) ^99mTcsestamibi tomographic perfusion imaging was performed within 1 week of coronary flow-velocity studies, κ statistics were calculated to measure the strength of correlation among coronary flow velocities, perfusion imaging data, and QCA results. QCA stenosis severity (abnormal, ≥50% diameter stenosis) and poststenotic Doppler coronary flow reserve (ratio of abnormal distal hyperemic to basal flow, ≤2.0) were correctly correlated in 20 of 27 patients (74%; κ= .48). QCA stenosis severity and ^99mTc-sestamibi imaging (abnormal if one or more reversible myocardial segments were present in the poststenotic zone) were correlated in 28 of 33 patients (85%; κ=.63). ^99mTc-sestamibi imaging results agreed with the basal (nonhyperemic) proximal-to-distal velocity ratio (normal, <1.7) in 15 of 31 patients (48%; κ=.17). The strongest correlation occurred between hyperemic distal flow-velocity ratio measurements and ^99mTc-sestamibi perfusion imaging results in 24 of 27 patients (89%; κ=.78). All 14 patients with abnormal distal hyperemic flow-velocity values had corresponding reversible ^99mTc-sestamibi tomographic defects. More reversibly hypoperfused segments were present in patients with abnormal poststenotic hyperemic flow-velocity ratios (abnormal, 2.4±0.7 segments; normal, 0.6±1.0 segments; P<.05). The number of poststenotic myocardial ^99mTc-sestamibi perfusion defects was correlated with the QCA percent cross-sectional area reduction (P<.02) and with minimal Iuminal diameter (F<.05) of intermediate-severity coronary artery stenoses. Conclusions: Two technologically diverse functional measures of stenosis severity - Doppler-derived poststenotic hyperemic intracoronary flow reserve and vasodilator stress ^99mTc-sestamibi myocardial perfusion imaging - are highly (89%) correlated. The physiological assessment of coronary stenoses of angiographically intermediate severity may be improved by the use of these techniques.