Effect of Detection of Subclinical Atherosclerosis on Carotid Ultrasound on Cardiovascular Events in A Primary Prevention Clinical Setting.

Abstract

Background: The relative contribution of common carotid artery (CCA) intimal medial thickness (IMT), carotid bifurcation plaque presence and its burden in predicting cardiovascular disease (CVD) events in a primary prevention clinical cohort remain unclear.

Aims: To assess the usefulness of distal far wall of right (R) and left (L) CCA IMT assessment (in the absence of carotid bifurcation plaque), and plaque presence and plaque number on incident CVD in a primary prevention clinical setting.

Methods: Observational study of consecutive 1903 patients free of known CVD clinically referred for R and L carotid bifurcation 2D ultrasound for SA assessment between 2007-2014 at a single center. Incident composite CVD (cardiac death, myocardial infarction, unstable angina and ischemic stroke) was compared between patients with and without plaque (defined as focal or diffuse medial-adventitial border to luminal border thickening of >1.5 mm), with increasing plaque number and with increasing CCA IMT percentiles (<25^th, 25-49, 50-74 and >75^th centile adjusted for atherosclerotic CVD scores using Pooled Cohort Equation (PCE) and Framingham Risk Score (FRS) in the absence of bifurcation plaque RESULTS: Final study cohort was 1569 (mean age 55.1±8.6; female 36%) after study exclusions with mean follow-up of 9.8±5.5 years. 859 (54.7%) had carotid plaque and 710 (45.3%) had no plaque. Incident composite CVD occurred in 90 (5.7%) patients, with no difference in patients with and without plaque (HR 1.19, 95% CI 0.78-1.82, P=0.425) or with >75th vs. < 75^th IMT percentile in the absence of plaque (HR 1.35, 95% CI 0.64-2.85, P=0.431). Increased incident CVD events occurred in patient with 3 or more plaques vs. no plaque (HR 2.9, 95% CI 1.48-5.65, p=0.002) which remained significant after adjusting for PCE (HR 2.45, 95% CI 1.13-5.3, p=0.023) and FRS. Patients with IMT centile >75% and presence of carotid plaque received increasing new statin prescriptions after carotid ultrasound result. Significant LDL-c reduction (19.3±25.7mg/dl, p<0.001) on follow up occurred only in patients in whom plaque was identified.

Conclusions: Number of carotid bifurcation plaques on carotid ultrasound is associated with incident CVD in a primary prevention cohort. Given referral nature of study cohort, evaluation of only carotid vascular bed and increased statin prescriptions after carotid ultrasound result, our findings regarding lack of prognostic value of CCA IMT or of any plaque should be interpreted with caution. Presence of plaque on carotid ultrasound led to increased statin prescriptions and greater LDL-c reduction on follow up. This clinically useful and simple method can be adopted in clinical practice for CVD risk stratification.