Washout collaterometry: a new method of assessing collaterals using angiographic contrast clearance during coronary occlusion

Objective To investigate the hypothesis that the time to washout of radiogr aphic contrast medium trapped distal to an occluded collateral receiving ve ssel is inversely related to collateral flow, and that this provides an acc urate method for characterising coronary collaterals. Methods-An intracoronary pressure derived collateral flow index was determi ned in 54 patients undergoing percutaneous transluminal coronary balloon an gioplasty (PTCA). The study group was subdivided according to whether the c ollateral vessels were sufficient (n = 17) or insufficient (n = 37) to prev ent ECG signs of myocardial ischaemia during PTCA. Washout collaterometry-a n angiographic washout method-was carried out simultaneously; after injecti on of radiographic contrast medium into the collateral receiving vessel fol lowed immediately by vascular occlusion, the number of heart beats was coun ted until approximately half the length of the epicardial vessel was cleare d of contrast. Results-The collateral flow index was higher (0.28 (0.09) v 0.12 (0.07); p < 0.0001) and the contrast washout time shorter (8.0 (2.9) v 17.5 (6.7) hea rt beats; p < 0.0001) in patients with sufficient versus insufficient colla terals. There was an inverse correlation between contrast washout time and collateral flow index (r = 0.72, p < 0.0001). Washout of contrast distal to the occluded vessel within I I heart beats correctly determined sufficient and insufficient collaterals with 88% sensitivity and 81% specificity. Conclusions-Washout collaterometry is a new radiographic contrast washout m ethod based on the inverse relation between collateral flow and the time to clearance of radiographic dye injected into the ipsilateral vessel during PTCA. It appears to be an accurate method of characterising coronary collat eral vessels.