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Figure 2 (A) Simultaneous tracing of three surface and one intracoronary (i.c.) ECG lead (at the top), of phasic (left side), mean aortic (P_ao, 89 mm Hg during occlusion) and IC distal pressure before, during (P_occl, 11 mm Hg) and after occlusion. CVP = central venous pressure (7 mm Hg). During occlusion of the stenosis, there are marked ST-segment elevations (arrows) on the i.c. ECG lead that disappear after balloon deflation. On the simultaneous flow velocity tracing, flow velocity time integral (Vi_occl) during occlusion amounts to 2.3 cm. Vi after PTCA was equal to 33 cm (Vi_ø-occl, not shown), thus CFI_v = 2.3/33 = 0.07; CFI_p = (11-7)/(89-7) = 0.05. (B) Simultaneous tracings as described above. P_ao = 90 mm Hg during occlusion, P_occl = 34 mm Hg, CVP assumed to be 5 mm Hg. During occlusion of the stenosis, there are no ST-segment elevations on the IC or surface ECG leads. On the simultaneous flow velocity tracing, Vi_occl amounts to 5.3 cm. Vi after PTCA was equal to 15 cm (Vi_ø-occl, not shown), thus CFI_v = 5.3/15 = 0.35; CFI_p = (34-5)/(90-5) = 0.34.