Physiological Basis for Angina and ST-Segment Change PET-Verified Thresholds of Quantitative Stress Myocardial Perfusion and Coronary Flow Reserve

Memorial Hermann Hospital, Houston, Texas, United States
JACC. Cardiovascular imaging (Impact Factor: 7.19). 09/2011; 4(9):990-8. DOI: 10.1016/j.jcmg.2011.06.015
Source: PubMed


This study aimed to determine the quantitative low-flow threshold for stress-induced perfusion defects with severe angina and/or significant ST-segment depression during dipyridamole hyperemia.
Vasodilator stress reveals differences in regional perfusion without ischemia in most patients. However, in patients with a perfusion defect, angina, and/or significant ST-segment depression during dipyridamole stress, quantitative absolute myocardial perfusion and coronary flow reserve (CFR) at the exact moment of definite ischemia have not been established. Defining these low-flow thresholds of angina or ST-segment changes may offer insight into physiological disease severity in patients with atherosclerosis.
Patients underwent rest-dipyridamole stress positron emission tomography (PET) with absolute flow quantification in ml/min/g. Definite ischemia was defined as a new or worse perfusion defect during dipyridamole stress with significant ST-segment depression and/or severe angina requiring pharmacological treatment. Indeterminate clinical features required only 1 of these 3 abnormalities. The comparison group included patients without prior myocardial infarction, or angina or electrocardiographic changes after dipyridamole.
In 1,674 sequential PET studies, we identified 194 (12%) with definite ischemia, 840 (50%) studies with no ischemia, and 301 (18%) that were clinically indeterminate. A vasodilator stress perfusion cutoff of 0.91 ml/min/g optimally separated definite from no ischemia with an area under the receiver-operator characteristic curve (AUC) of 0.98 and a CFR cutoff of 1.74 with an AUC = 0.91, reflecting excellent discrimination at the exact moment of definite ischemia.
Thresholds of low myocardial vasodilator stress perfusion in ml/min/g and CFR sharply separate patients with angina or ST-segment change from those without these manifestations of ischemia during dipyridamole stress with excellent discrimination. Stress flow below 0.91 ml/min/g in dipyridamole-induced PET perfusion defects causes significant ST-segment depression and/or severe angina. However, when the worst vasodilator stress flow exceeds 1.12 ml/min/g, these manifestations of ischemia occur rarely.

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    • "A significant correlation existed between rest PRP and average absolute flow at baseline (r = 0.71, 95% confidence interval 0.39 to 0.88, P < .001), as expected and previously described.6 However, the correlation between rest PRP and average flow while taking daursentan was not significant (r = 0.25, 95% confidence interval −0.21 to 0.63, P = .28), suggesting an uncoupling of PRP from absolute flow as seen with other vasodilators such as dipyridamole.12 "
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