Time course and extent of collateral channel recruitment during coronary angioplasty

OBJECTIVES: To assess the extent and timing of recruitment of collateral channels during coronary angioplasty in patients without spontaneous collaterals at diagnostic angiography. SETTING: The extent of collateral channel recruitment during coronary angioplasty is variable and its contribution to myocardial protection is not well established. The functional significance of collaterals recruited during balloon occlusion remains in question. PATIENTS: Collateral channels were assessed in 16 patients by contralateral injection at 30, 60 and 90 s into each of four 90 s inflations and by a 0.014 " Doppler guide wire distal to the lesion. RESULTS: Angiographic collateral recruitment was evident in 11 out of 16 patients (71%), but in only four (24%) by intracoronary Doppler. Grade I collaterals were present in seven patients, grade II in three and grade III in two. Collaterals were evident angiographically by 30 s in 10 out of 11 patients, with no progressive recruitment during subsequent inflations. In the four patients with Doppler evidence of collateral flow there were no differences in any flow velocity parameters with successive inflations. There was no difference in either maximum ST segment shift or time to 2 mm ST segment elevation between successive inflations. CONCLUSIONS: Collateral channel recruitment is variable between patients and appears maximal early in the first inflation. The lack of incremental recruitment of collaterals together with low or absent evidence of flow by Doppler wire suggests that these channels do not make a major contribution to myocardial protection in this setting.