Figure 4.

Simultaneous recordings of an intracoronary (i.c.) ECG lead (top), phasic (left side) and mean (right side) aortic (P_ao, mm Hg), coronary occlusive (P_occl, mm Hg), and central venous pressures (CVP, mm Hg). P_ao is gauged via a 6 French coronary artery guiding catheter, P_occl via a pressure guidewire positioned distal of a stenosis to be dilated, and CVP via a right atrial catheter. To the right of the phasic pressure tracings obtained during coronary artery patency, mean pressures are recorded during and after angioplasty balloon deflation. During inflation, there are pronounced ECG ST segment elevations (arrows) indicating collateral vessels insufficient to prevent myocardial ischaemia. Collateral flow index (CFI) is calculated as follows: CFI = (P_occl − CVP)/(P_ao − CVP).