CAROTID ARTERIES
Atherosclerosis is the most common cause of both carotid and coronary
artery stenotic disease. The plaques were detected in carotids in 31%
of patients during the PESA (Progression of Early Subclinical
Atherosclerosis) Study 23. Ruptures of atherosclerotic
plaques, which can lead to thrombus formation, can clinically manifest
as stroke or as ACS 24. Many reports suggest a
correlation between the presence of atherosclerosis in the coronary
arteries and carotid arteries. Proving such correlations can help
identify the presence of atherosclerotic plaques in the coronary
arteries using a non-invasive imaging modality - CAUS. Reports of an
association between the presence of atherosclerotic plaques in the
carotid arteries in CAUS and the presence of atherosclerotic plaques in
the coronary arteries have been demonstrated in observational studies -
prospective and cohort studies (Table 2).
There are also reports that carotid atherosclerosis, and carotid artery
stenosis (CAS), are independent predictors of major adverse
cardiovascular events in patients without preexisting CAD (respectively,
HR=1.69; p=0.07 and HR=3.17; p<0.01) 25.
They also showed that the incidence of clinically significant severe CAS
(>50%) was progressively increased among patients with
non-obstructive CAD, single vessel disease (VD), double VD, triple VD,
and left main coronary artery disease. In the Japanese population, the
prevalence of carotid stenosis diagnosed in CAUS was 14.5% in single VD
and 29.8% in multivessel disease (p<0.0001)16. Also, in patients with confirmed CAD, the majority
(about 95%) showed atherosclerotic changes in the carotid arteries,
with 15% showing hemodynamically significant CAS 8.
The result of the study by Puz et al. is also significant, as they found
no differences in the incidence of carotid atherosclerosis between
patients with stable and unstable CAD (15.3% vs. 19%, respectively)15. Another study also confirmed the hypothesis that
critical CAS is more common in patients with CAD 26.
It has also been shown that maximal plaque area can reflect the clinical
severity of CAD and can be used as a simple, non-invasive indicator of
the severity of coronary atherosclerosis 27. One study
confirmed that the presence of plaques is a better predictor of CAD and
the Framingham risk scale than intima-media thickness (IMT). This study
found that patients with CAD had a higher rate of clinical (referred to
as the presence of plaque) or subclinical (referred to as IMT) carotid
atherosclerosis 28. In the study by Morito et al. also
IMT and plaque score (PS) were assessed in a population of Japanese
patients and compared with CA data 29. It was shown
that a high PS showed the strongest predictive value for the presence
and/or severity of CAS. A study by Kandasi et al. examined the
relationship between CAD and common carotid artery (CCA) wall morphology
also using CAUS. They showed that the strongest predictor of CAD was the
presence of calcified atherosclerotic plaque compared to the presence of
fibrous plaque and thickened IMT 30. Moreover, in the
study group, none of the subjects with normal CCA wall morphology had
significant coronary artery lesions. Another meta-analysis confirmed
that atherosclerosis affects both the carotid and coronary systems,
although not always in identical phenotypes 31. It
confirmed that carotid artery testing is useful in any case of suspected
CAD. It cites publications showing a correlation between CAS and
significant CAD (r=0.53, P<0.001) and between carotid and
coronary calcification (r=0.61, P<0.001). The studies cited in
this meta-analysis 32-36 and others are summarized in
Table 2.
Reduction of Atherothrombosis for Continued Health (REACH) registry with
4-year follow-up (23 364 patients) showed that the risk of coronary
events increased by 22% in patients with versus without carotid
atherosclerosis 37. The prevalence of critical CAS has
been shown to correlate with the number of critically stenosed coronary
arteries. Patients (n=109) with severe CAD (three-vessel disease) were
also examined for CAS with CCT 38. Significant lesions
included cervical and intracranial segments of both the internal carotid
artery (ICA) and the right vertebral artery. An autopsy study by Molnár
et al. comparing the extent of atherosclerosis in the carotid, coronary
and femoral arteries showed correlations among patients who died of
ischemic stroke. The authors found a significant correlation between the
external carotid and left anterior descended coronary artery (r=0.458,
p=0.028) 39.
Advances in the US have also increased the role of this method in the
stratification of patients with CAD. The US is used to detect
subclinical atherosclerosis, particularly by evaluating the plaque
(height, total area) in the carotid arteries, and is increasingly used
in making clinical decisions regarding the treatment of atherosclerosis40-42. This method is now standardized in the 2020
American Society of Echocardiography (ASE) guidelines43. The benefits of arterial US can also be achieved
in asymptomatic patients. As described in a systematic review by Peters
et al. who showed that imaging of subclinical atherosclerosis as an
adjunct to conventional risk factor assessment can improve risk
prediction of cardiovascular events (CVE) in asymptomatic individuals44. Relevant evidence includes: CIMT, carotid plaques,
and/or coronary arteries calcium score (CACS). In addition to the mere
co-occurrence of plaques in the mentioned arteries, the phenotype of the
plaques may also be effective in patient risk stratification. A closer
analysis of plaques was also studied by Zhao et al. in which they found
a significant correlation between plaque phenotype and carotid artery
plaque composition 45. They also found that mixed
coronary plaque may suggest high-risk carotid plaque. In addition, a
study was conducted to investigate plaque composition concerning the
incidence of stroke and CAD in a group of asymptomatic individuals who
had subclinical atherosclerosis in CAUS 46. Plaque
features were assessed by resonance imaging - the presence of specific
plaque components (intimal hemorrhage [IPH], lipid-rich necrotic
core, and calcification, and measures of plaque size). A study showed
that the presence of IPH in carotid atherosclerotic plaque is an
independent risk factor for stroke and CAD. The article by Uematsu et
al. on ultrasound evaluation of the carotid artery highlighted the
assessment of atherosclerotic plaque echo lucent as a predictor of
coronary events 47. Echolucent carotid artery plaques
are characterized by being rich in macrophages and lipids. Susceptible
plaques can be stabilized by statins. The study aimed to identify
patients who are at high risk but could benefit from lipid-lowering
therapy for secondary prevention. As it turned out, the evaluation of
carotid artery echolucency was useful in this selection and made it
possible to predict secondary coronary events in patients with CAD after
statin therapy. The study also showed that the prognostic effect of
lipid-lowering therapy depends on the echolucency of atherosclerotic
plaque in the carotid artery 48. In addition to
phenotypic plaque characteristics, it has been shown that assessment of
neovascularization can be useful in risk stratification of patients at
cardiovascular risk. This can be assessed by quantitative analysis by
contrast-enhanced ultrasound of the carotid artery. Based on the common
underlying pathology of atherosclerosis in the 2 arterial systems, the
study of carotid arteries in CAD and vice versa became clinically
important to accurately identify patients who could benefit from
aggressive preventive therapy as well as prompt treatment49, 50.