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Figure 1 Tracings of simultaneous mean aortic pressure (Pao), distal coronary artery pressure (Poccl) and an intracoronary (i.c.) electrocardiographic (ECG) lead obtained in a patient with marked collateral recruitment during the three 2-min coronary artery occlusions (time: horizontal axis). The distal coronary artery pressure during the balloon occlusions (i.e., i.c. wedge pressure, Poccl = 12 mm Hg) is close to the dotted line (= 10 mm Hg) and increases during as well as between each of the occlusions. Meanwhile, Pao remains relatively constant. Collateral flow index during each of the occlusions is calculated as (Poccl – CVP)/(Pao – CVP); CVP: central venous pressure = 5 mm Hg. The i.c. ECG lead obtained via the pressure guidewire for the measurement of Poccl shows marked ST elevation during the occlusions that decreases between the first and third occlusion.