Carotid Ultrasound Identifies High Risk Subclinical Atherosclerosis in Adults with Low Framingham Risk Scores

Abstract

Conclusion: A high percentage of young to middle-aged individuals with a Framingham Risk Score (FRS) indicating <5% risk of cardiovascular events have abnormal carotid ultrasound findings associated with an increased risk for cardiovascular events. Summary: Atherosclerosis-related clinical events are presumably preceded by a period of asymptomatic atherosclerosis. The FRS is a population-based algorithm recommended to identify at-risk individuals and determine the aggressiveness of preventive therapy (JAMA 2001;285:2486-97). However, population-based risk algorithms do not quantify atherosclerosis. They provide only a probability of cardiovascular events over a relatively short fixed period, usually <10 years. The FRS risk assessment also does not incorporate family history, premature coronary artery disease, remote smoking history, impaired fasting glucose, triglyceride levels, or waist circumference. Tests for subclinical atherosclerosis are therefore sometimes recommended to add incremental information and provide more accurate risk stratification. The authors tested the hypothesis that patients with a low (<5%) FRS 10-year risk for a first cardiovascular event and intermediate (6% to 20%) FRS 10-year risk will have increased cardiovascular risk as determined by an abnormal carotid intima-media thickness (IMT). This study included individuals aged <65 years who were not taking statins and who did not have diabetes or a history of coronary artery disease, but who did undergo a determination of carotid IMT and plaque for primary intervention. Clinical variables analyzed included lipid values, family history of coronary artery disease, FRS, and subsequent pharmacotherapy recommendations. The study comprised 441 individuals who were a mean age of 49.7 ± 7.9 years. Of these patients, 184 (42%, 95% CI, 37.3%-46.5%) had high-risk carotid IMT findings (carotid IMT ≥75th percentile adjusted for age, sex, race, or presence of plaque). In 336 individuals with the lowest FRS score of <5%, 127 (38%, 95% CI, 32.6%-43.0%) had high-risk carotid ultrasound findings. The treating physicians recommended lipid-lowering therapy for 77 individuals (61%) with a FRS ≤5% and high-risk carotid ultrasound findings. Comment: This study indicates a disconnect between the risk assessment by the FRS and carotid IMT. Studies have also found high-risk carotid ultrasound findings influence physicians to prescribe aspirin or lipid-lowering therapies (Wyman RA, et al; Am Heart J 2007;154:1072-7 and Korcarz CE, et al; J Am Soc Echocardiogr 2008;21:1156-62). However, although physicians may make treatment decisions based on a finding of increased carotid IMT, it appears that observing changes in IMT to monitor effects of drug therapy will not reduce subsequent clinical events. A practical point may be that carotid IMT can be used to identify patients at increased risk for cardiovascular events, but once treatment is initiated, subsequent studies to monitor effectiveness of treatment may not be needed.