Hemodynamic conditions at the carotid bifurcation during protective commoncarotid occlusion

Objectives. Carotid angioplasty and stenting procedures are associated with an obligatory release of particulate debris into the distal cerebral circu lation. Although most of the emboli are small and do not result in symptoma tic neurologic deficits, some may be large enough to cause stroke. For this reason, a variety of filters and balloon occlusion devices have been emplo yed as adjuvants to decrease the risk of distal embolization during carotid stenting. Some of these devices rely on the arrest of antegrade blood flow with the use of inflow arrest. The present study was undertaken to investi gate the hemodynamic conditions that exist at the carotid bifurcation durin g common carotid artery (CCA) occlusion. Methods. Internal carotid artery (ICA) and external carotid artery (ECA) st ump pressures were measured in 29 patients undergoing carotid endarterectom y. Duplex ultrasound scanning was used to measure the direction and velocit y of blood flow in the ICA and ECA with the CCA cross-clamped but the ICA a nd ECA open, a clinical scenario analogous to CCA balloon occlusion at the time of carotid angioplasty and stenting. The direction and magnitude of IC A and ECA flow were compared with the stump pressures to determine whether a correlation existed between these variables. Results. The mean stump pressure in the ICA and ECA averaged 56 +/- 16 and 53 +/- 12 mm Hg, respectively. The ICA systolic stump pressure was lower th an the ECA systolic stump pressure in six patients (21%), and all of these patients had persistent antegrade systolic duplex blood flow by duplex inte rrogation during CCA occlusion. The ICA systolic stump pressure exceeded th e ECA systolic stump pressure in 19 patients (66%), and all of these patien ts had retrograde ICA flow during systole. Diastolic flow was also well cor related with the magnitude of the ICA/ECA stump pressure differential, with antegrade diastolic ICA blood flow in all nine patients with an ICA diasto lic stump pressure less than the ECA diastolic stump pressure. None of the 10 patients with ICA diastolic stump pressure greater than ICA diastolic st ump pressure maintained antegrade ICA diastolic flow, but four of these pat ients had flow to zero in diastole. Overall, 13 of 29 patients (45%) could be surmised to be at risk for distal. embolization to the brain based on th e persistence of some element of either systolic or diastolic antegrade ICA flow during common carotid occlusion. Conclusions. Common carotid occlusion alone appears insufficient to protect against distal embolization during manipulations of the carotid bifurcatio n. Persistent systolic or diastolic antegrade blood flow occurs in a high p roportion of patients, lending credence to the use of additional protective strategies to ameliorate the risk of embolic complications.