Changes in internal carotid blood flow after CEA evaluated by transit-time flowmeter.

Abstract

The aim of this study was to investigate whether there was an association between the degree of the stenosis of the internal carotid artery (ICA) and post-operative increase of blood flow. In 200 out of 660 patients undergoing carotid endarteriectomy (CEA) for a high-degree ICA stenosis, pre-operatively a bilateral selective carotid and intracerebral angiography was performed. The degree of the ipsilateral and contralateral stenosis was digitally assessed by using computer software according to the CC-Index. Intraoperatively, the pressure ratio over the stenosis (ICA/CCA) was measured by direct arterial puncture. Blood flow in the ICA was measured before and after CEA with an ultrasound flowmeter using the transit-time principle. These findings were correlated to the degree of stenosis revealed by angiographic analysis and the pressure ratio. Before CEA the median blood flow in the ICA was 171 ml/min (range 620 ml/min) with a significant (p<0.001) post-operative increase to 250 ml/min (range 875 ml/min). The median relative increase of flow (post-flow-pre-flow/pre-flow) was 42%. The pre-CEA flow volumes were dependent on the degree of stenosis and also the pressure ratio. The increase of flow following CEA correlated better with pressure ratio (r=-0.435, p<0.001), than the stenosis severity (r=0.319, p<0.001). Analysis of variance identified only the pressure gradient as an independent determinant of flow changes following CEA. The blood flow increase following CEA is mainly determined by the pressure gradient across the stenosis.