Coronary collateral quantitation in patients with coronary artery disease using intravascular flow velocity or pressure measurements
Christian Seiler, MD, FACCa,
Martin Fleisch, MDa,
Ali Garachemani, MDa and
Bernhard Meier, MD, FACCa
a Department of Cardiology, University Hospital, Bern, Switzerland
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Figure 1 Schematic illustration of the coronary collateral circulation with an inflated angioplasty balloon and a Doppler and pressure guidewire located distal to the stenosis. A coronary flow velocity spectrum obtained distal to the stenosis is shown on the right side (horizontal axis: time, second; vertical axis: average peak velocity [APV], cm/sc, i.e., time average value of instantaneous peak velocity samples over two cardiac cycles). The flow velocity trend depicts a graphic illustration of the concept of the velocity-derived collateral flow index (CFIv, no unit) showing that APV during occlusion amounts to more than half of APV during vessel patency. For the actual calculation of CFIv, ratios of distal velocity time integrals during (VIoccl or PVi, cm) to that after occlusion and following cessation of reactive hyperemia (Vi -occl, cm) are used (see equations above). Abbreviations: CFIp (no unit): pressure-derived collateral flow index; CVP: central venous pressure (mm Hg); Pao: mean aortic pressure (mm Hg); Poccl: intracoronary distal occlusive pressure (mm Hg).
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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 (Pao, 89 mm Hg during occlusion) and IC distal pressure before, during (Poccl, 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 (Vioccl) during occlusion amounts to 2.3 cm. Vi after PTCA was equal to 33 cm (Viø-occl, not shown), thus CFIv = 2.3/33 = 0.07; CFIp = (11-7)/(89-7) = 0.05. (B) Simultaneous tracings as described above. Pao = 90 mm Hg during occlusion, Poccl = 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, Vioccl amounts to 5.3 cm. Vi after PTCA was equal to 15 cm (Viø-occl, not shown), thus CFIv = 5.3/15 = 0.35; CFIp = (34-5)/(90-5) = 0.34.
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Figure 3 Coronary collaterals assessed by angiography (squares and circles, thick short lines: standard deviation) and intracoronary (IC) ECG (triangles and diamonds) compared with the IC velocity- and pressure-derived collateral flow index (CFI, vertical axis). Well-developed collaterals were defined as those with an angiographic collateral degree  2 (0 to 3). Patients with sufficient collaterals were defined as those without ST-segment changes (>1 mm) on IC or surface ECG during balloon occlusion (IC guidewire distal to the stenosis). Velocity- and pressure-derived collateral flow indices do not accurately differentiate between well and poorly developed collaterals, whereas they accurately predict sufficient and insufficient collaterals at a threshold of 0.30 (broken line).
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Figure 4 (A) Comparison between simultaneously obtained velocity- and pressure-derived collateral flow indices (CFIv, vertical axis; CFIp, horizontal axis). There is a direct, significant correlation between CFIv and CFIp. (B) Bland-Altman analysis of the average between CFIv and CFIp (horizontal axis) and the difference between CFIv and CFIp (vertical axis).
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