Validation of flow convergence region method in the assessment of carotid artery stenoses during color-flow duplex studies.

Abstract

The flow convergence region (FCR) method (also known as the proximal isovelocity surface area method) is currently used in echocardiography to evaluate the flow through cardiac valves and septal defects. The FCR method is based on the characteristic alterations in flow dynamics that occur proximal to a stenotic orifice. Blood converges uniformly and radially towards an orifice that is small relative to the section of the vessel and forms concentric isovelocity hemispheric shells where velocity progressively increases and flow remains laminar. The purpose of the article is to validate the use of this principle in the detection and assessment of carotid stenoses in the course of color-flow duplex studies. In this prospective study, 80 patients affected by unilateral or bilateral carotid artery stenoses were evaluated for the presence of the FCR from February 1997 to March 1999. The results were compared with digital subtraction angiography. Color-flow duplex diagnosis of carotid artery stenoses of 70% or more was confirmed in 100% of the carotid artery stenoses (40/40 patients) with angiography. The FCR was detected in 72.2% (13/18) of carotid arteries affected by stenoses greater than 80%, in 54.4% (12/22) of carotid arteries affected by stenoses 70% to 80%, and in 13.6% (6/44) of carotid arteries affected by stenoses 50% to 69% (P <.001). In 5% of cases (2/40 of stenoses) the FCR was the only detectable sign of carotid stenosis. Our data suggest that a routine search for FCR in the course of color-flow duplex study of carotid arteries may further improve the reliability of this examination in the detection of carotid artery stenoses, particularly in the presence of heavily calcified lesions.