RECLASSIFICATION OF LOW AND INTERMEDIATE FRAMINGHAM RISK SCORE PATIENTS USING CAROTID DUPLEX IMAGING
Author Block: MF Matangi, AK Peirce, DW Armstrong
PURPOSE. The Framingham risk score (FRS) is used by many clinicians to classify a patient's (P) 10 year risk of a cardiovascular event as either low risk (20%). The purpose of our investigation was to see if the addition of common carotid artery (CCA) intimal medial thickening (IMT) and internal carotid artery (ICA) stenosis using intersocietal commission for the accreditation of vascular laboratories (ICAVL) imaging and velocity criteria could reclassify P in the low and intermediate FRS categories.
METHODS. CARDIOfile, our cardiology database and reporting system was searched for P with a low or intermediate FRS, who also had carotid duplex imaging performed. 90 P were obtained who had all the necessary data points entered. These were FRS, R) CCA IMT, L) CCA IMT and if applicable any internal carotid artery stenosis using ICAVL imaging and velocity criteria. A CCA IMT >0.99 was considered abnormal as was the presence of any degree of ICA stenosis in either carotid territory.
RESULTS. Of the 90 P, 37 P were low FRS and 53 P were intermediate FRS. 13 P (35.1%) in the low FRS group had an abnormal carotid study. 37 P (69.8%) in the intermediate FRS group had an abnormal carotid study. Of the 180 ICA in the 90 P studied. 43 ICA (23.9%) had an ICA stenosis based on ICAVL imaging and velocity criteria. There were 36 ICA with a stenosis of 1-39%, 6 ICA with a stenosis of 40-59% and 1 ICA with a stenosis of 60-79%.
CONCLUSIONS. 70% of all intermediate FRS P are reclassified as high risk when carotid duplex imaging data is added. The other 30% drop down to low FRS. This has important ramifications with respect to lipid target values and vascular protective therapy for both groups. Aspirin, Statin and even ACE inhibitor drug therapy for the truly high risk group and no vascular protective therapy for those reclassified to low risk. Although the diagnostic yield in the low FRS P is much lower it is still very important for the 35% who move from a low FRS to a high FRS category and therefore require the same vascular protective drug therapy. We believe that all P with an intermediate FRS should undergo carotid duplex imaging for proper classification of vascular risk and that serious consideration should be given to the low FRS P as well.