Volumetric Evaluation of Carotid Artery Flow, Imortance of Compensatory Mechanisms

Abstract

Carotid artery stenosis exceeding 70-80% is an indication for interventional procedure consideration. However two groups of patients – symptomatic and asymptomatic have to be evaluated separately. One of obvious mechanisms of different patient's performance is development of collateral circulation providing blood to affected region - patency of Willis circle vessels, which connects inflow of both carotid and vertebral arteries. It is fully developed in only 34,5% of patients. In our work we concentrated on volumetric measurements of cerebral inflow in basic arteries – ICA, ECA & VA assuming that total flow volume in elderly patients does not exceed 800 – 1000 ml (ICA – 250-350 ml, VA-100-120ml / min). To establish range of normal values control group of 80 patients age>65 with no evidence of neurological/vascular disease were checked. In a group of 100 patients with ICA narrowing >50% global flow in ICA, ECA & VA was estimated using Aloka F75 & ToshibaAplio500. In cases of major stenosis/obstruction of ICA significant increase of flow in nonstenosed vessels was observed in over 80% of patients, with absent or minimal clinical symptoms, vs. only 27% in group of symptomatic patients with stenosis >70/80%. The results are obscured by the fact, that atheromatic changes are present in different vessels providing blood to brain flow, causing different interactive alterations of brain perfusion. Changing point of interest from degree of stenosis towards global cerebral inflow estimation can possibly change our indications for vascular invasive procedures by excluding patients with developed collateral circulation. On the other hand patients without sufficient compensatory mechanisms should be considered principal candidates for surgery, even in absence of clinical symptoms.