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Figure 1 Diagram showing two coronary arteries with interconnecting collaterals (depicted as one anastomosis). The stenotic lesion on the left side is occluded by an angioplasty balloon. Angioplasty guidewire-based Doppler- and pressure-sensors are positioned distal to the occluded stenosis in order to measure simultaneously occlusive i.c. velocity (i.e., velocity time integral, Vioccl, cm) and pressure (Poccl, mm Hg). At the same time, Pao is determined via the angioplasty guide catheter. A pressure- and velocity-derived collateral flow index (CFIp, mm Hg/mm Hg; CFIv, cm/cm) can be calculated as shown on the right side by additional measurement of the distal i.c. velocity during vessel patency (Viø-occl, cm; CVP = 5 mm Hg). The vascular resistance indexes of the collateral circulation (Rcoll, mm Hg/cm) and of the collateral-receiving (i.e., ipsilateral) microcirculation (R4) can be computed. Resistance indexes of the contralateral side (R1 and R3) cannot be determined. CFIp = pressure-derived collateral flow index; CFIv = velocity-derived collateral flow index; CVP = central venous pressure; i.c. = intracoronary; Pao = mean aortic pressure; Poccl = distal coronary occlusive pressure; Rcoll = collateral resistance index; R1 = epicardial vascular resistance; R3 = contralateral resistance index; R4 = ipsilateral resistance index; Vioccl = distal velocity time integral during vessel occlusion; Viø-occl = distal velocity time integral during vessel patency.
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