Statin Naïve Patients with Myocardial Infarction have more Echolucent Plaques Compared to Long-term Statin Treated Chronic Atherosclerotic Patients – A 3D Ultrasound Study

Abstract

Introduction: Size and morphology of carotid atherosclerotic plaques can be quantified by ultrasound (US) imaging. Carotid artery plaque size and gray-scale median (GSM) have been identified as risk markers for both cardiovascular events and stroke ADDIN EN.CITE ADDIN EN.CITE.DATA (1, 2). Unstable plaques have a thin fibrotic cap and a lipid or hemorrhagic core ADDIN EN.CITE ADDIN EN.CITE.DATA (3-6). A higher amount of lipid and hemorrhage have been observed in echolucent carotid plaques presenting as lower GSM compared to echogenic carotid plaques containing fibrotic tissue and calcification ADDIN EN.CITE ADDIN EN.CITE.DATA (7-10). Classic cardiovascular risk scores such as Framingham score lack precision ADDIN EN.CITE ADDIN EN.CITE.DATA (11, 12). Information about atherosclerotic plaque characteristics and development can potentially improve risk stratification. Methods: : Two patient populations were included prospectively; a group admitted with first-time myocardial infraction and naive to statin treatment and a group followed for peripheral arterial disease on stable statin treatment for more than six months, all being ≤65 years old. Both carotid arteries were scanned with 3D ultrasound by the same sonographer. All plaques were analyzed using a semiautomated software. Gray-scale readings were normalized with adventitia as reference and GSM recorded. In patients with bilateral carotid artery plaques the thickest plaque was used for data analyses. Results: In the statin treated patients (n=70 , 64% male, mean age 60 (range 40-65)) compared to the statin naive patients (n= 70, 79% male, mean age 57 (range 38-65)) we found an increased plaque thickness (difference 0.65 mm, P=0.001), a larger plaque volume (difference 31.98 mm3, P=0.001) as well as a higher GSM (difference 9.46, 95% confidence interval: 1.59 - 17.33, P=0.019) (figure 1). The differences in thickness and volume disappeared after adjustment for age, gender, smoking, hypertension and diabetes mellitus (P= 0.066 and 0.050, respectively). The differences in GSM persisted after adjusting for volume (difference of 9.05, CI95%: 0.90 - 17.21, P=0.030). There was no correlation between volume and GSM (P=0.16). Conclusion: .By 3D US we detected differences in carotid plaque thickness, volume and morphology between two different atherosclerotic populations. The statin treated group with known clinical atherosclerotic disease, had larger plaques indicating a more advanced stage of disease as the difference diminished when adjusting for atherosclerotic risk factors. Also, this group had more echogenic plaques (higher GSM) which indicate less vulnerability, or a more stable stage of disease as compared to the statin naive group. Carotid 3D US imaging may prove clinically useful for identification and assessment of treatment response in high-risk patients with vulnerable plaques Disclosure: Co-author H. Sillesen has received research grants from Philips Ultrasound.