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Figure 2 Myocardial lactate extraction ratio (A) and coronary lumen diameter assessed by quantitative arteriography (B) at baseline (BSL), at submaximal and maximal doses of acetylcholine (ACH) and after isosorbide dinitrate (ISDN). Lactate extraction ratio was significantly different between groups (p < 0.01 by two-way analysis of variance) at the submaximal dose (p < 0.01 by ad-hoc t test). Lumen diameter is expressed as percentage of that after ISDN administration. Closed circles = Group 1 patients with evidence of microvascular spasm (MVS); open squares = Group 2 patients without evidence of MVS.