title: Physiological basis for angina and ST-segment change PET-verified thresholds of quantitative stress myocardial perfusion and coronary flow reserve.
abstract: OBJECTIVE
  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.
  
  
  BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Weatherhead PET Center For Preventing and Reversing Atherosclerosis, Division of Cardiology, Department of Medicine, University of Texas Medical School and Memorial Hermann Hospital, Houston, Texas, USA.
authors.forename: Nils P
authors.initials: NP
authors.lastname: Johnson
authors.forename: K Lance
authors.initials: KL
authors.lastname: Gould
mesh_terms: D000328:Adult; D000368:Aged; D000787:Angina Pectoris / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D017023:Coronary Angiography; D003324:Coronary Artery Disease / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology; D003326:Coronary Circulation; D004176:Dipyridamole; D005260:Female; D006801:Humans; D006940:Hyperemia / Q000000981:diagnostic imaging / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D049268:Positron-Emission Tomography; D011237:Predictive Value of Tests; D012372:ROC Curve; D012720:Severity of Illness Index; D013781:Texas; D014665:Vasodilator Agents
chemical_list: D014665:Vasodilator Agents; D004176:Dipyridamole