Review Article
Carotid Intima Media Thickness and Its Utility
as a Predictor of Cardiovascular Disease
A Review of Evidence
Mark Carpenter, MChem,* Hannah Sinclair, BSc, MB ChB, MRCP,†‡ and Vijay Kunadian, MBBS, MD, FRCP†‡
Abstract: Cardiovascular (CV) disease is still the leading cause of death in
the developed world, despite the considerable progress in CV medical and
surgical therapeutics. Many risk factors are associated with the development
of future adverse CV events, such as age, hypertension, body mass index, and
other comorbidities. Carotid intima media thickness (CIMT) is one method of
calculating plaque burden by assessing the level of arterial thickening present.
CIMT can be used as a noninvasive marker of atherosclerotic disease with
increasing CIMT linked to an increased risk of subsequent CV events. In this
review, the association of CIMT with CV disease is explored. Current literature on the role of CIMT in predicting CV outcomes is reviewed to determine
whether it is a predictor of CV events, both in the general population and in
the high-risk groups, such as those with hypertension, diabetes mellitus, and
chronic kidney disease.
Key Words: coronary artery disease, atherosclerosis, carotid intima media
thickness, cardiovascular risk, cardiovascular outcomes.
(Cardiology in Review 2016;24: 70–75)
C
ardiovascular disease (CVD) is still the leading cause of death in
the developed world, despite the considerable progress in cardiovascular (CV) medical and surgical therapeutics. Many risk factors are
associated with the development of future adverse CV events, such as
age, hypertension (HTN), body mass index (BMI), and other comorbidities. Carotid intima media thickness (CIMT) is one method of
calculating plaque burden by assessing the level of arterial thickening
present. CIMT can be used as a noninvasive marker of atherosclerotic
disease with increasing CIMT linked to an increased risk of subsequent CV events.1 CIMT is a combined measure of both the intimal
and the medial layers of the arterial wall, which may limit its use in predicting early atherosclerosis where intimal thickening predominates.1
Nonetheless, whether a change in CIMT over time affects the risk of
CV events has not been thoroughly investigated, with different studies describing CIMT as equally a good and poor predictor of future
adverse CV events. In the United States, the Intersocietal Accreditation Commission (IAC) has developed standards and methods for the
evaluation of the quality of care delivered in vascular testing.
From the *Faculty of Medical Sciences, Newcastle University Medical School,
UK; †Institute of Cellular Medicine, Newcastle University, Newcastle upon
Tyne, UK; and ‡Freeman Hospital, Newcastle upon Tyne NHS Foundation
Trust, Newcastle upon Tyne, UK.
Disclosure: The authors have no conflicts of interest to report.
This work was supported by the National Institute for Health Research (NIHR)
Newcastle Biomedical Research Centre based at Newcastle-upon-Tyne Hospitals National Health Service (NHS) Foundation Trust and Newcastle University. The views expressed are those of the authors and not necessarily those of
the NHS, the NIHR or the Department of Health.
Correspondence: Vijay Kunadian, MBBS, MD, FRCP, FACC, FESC, Institute of
Cellular Medicine, Faculty of Medical Sciences, Newcastle University, 3rd
Floor William Leech Building, Newcastle upon Tyne NE2 4HH UK. E-mail:
vijay.kunadian@ncl.ac.uk.
Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
ISSN: 1061-5377/16/2402-0070
DOI: 10.1097/CRD.0000000000000077
70 | www.cardiologyinreview.com
In this review, the association of CIMT with CVD is explored.
The potential for CIMT to be used as a predictor of future CV risk is
assessed. Current literature on the role of CIMT in predicting CV outcomes is reviewed, to determine whether it is a predictor of CV events,
both in the general population and in high-risk groups such as those
with HTN, diabetes mellitus (DM), and chronic kidney disease (CKD).
METHODS
The literature review was conducted on PubMed, NICE evidence, and Medline using the following search terms: “acute coronary syndrome,” “atherosclerosis,” “arterial stiffness,” “carotid intima
media thickness,” “coronary artery disease,” “cardiovascular disease
outcomes,” “myocardial infarction,” and “future cardiac risk.” Studies assessing the relationship between CIMT and CV events were
included. First, we searched for research that assessed the “use of
carotid intima media thickness in cardiology.” Second, we searched
for studies investigating the “relationship between carotid intima
media thickness and cardiovascular events.” Third, we evaluated the
“role of carotid intima media thickness in predicting cardiovascular
outcomes,” both in the general population and in high-risk groups.
References for all included studies were also searched and evaluated.
UTILITY OF CIMT IN THE PREDICTION OF ADVERSE
EVENTS IN THE GENERAL POPULATION
Previous studies suggest that CIMT is a good predictor of
future adverse CV events (Fig. 1). In addition to being a noninvasive
measurement, CIMT has no known adverse biological effects, which
may enable it to be used in studies including young populations.
CIMT is reproducible and quick to use2 and can be used to assess CV
risk in terms of disease progression and regression.
CIMT was first described as a predictor of future CV events
in a study based on the Rotterdam Cohort.3 A sample of 1683 subjects from the Rotterdam Study (7983 subjects) was cross-sectionally assessed by measuring CIMT, among other variables such as the
presence of plaque, BMI, and cholesterol levels, to estimate the absolute risk of coronary artery disease (CAD) within 10–12 years for
each participant.3 The 10-year absolute risk of CAD rose by 3.7% per
0.15-mm increase in CIMT. The subsequent risk of death increased
by 10.5% per 0.15-mm increase in CIMT within a 11.5-year period.
This study demonstrated that, when viewed cross-sectionally, CIMT
is a marker of risk of CAD and death within 10–12 years. The results
were detected when a significant level of stenosis was absent, suggesting that CIMT could help predict and detect the risk of CV events
earlier than other more traditionally used measurements.
Lorenz et al4 followed 37,197 subjects for a mean period of 5.5
years, demonstrating that an increase in CIMT of 0.1 mm increased
the future risk of myocardial infarction (MI) by 10–15% and stroke by
13–18%. Supplementing this finding, another study examined CIMT
in relation to future risk of MI and stroke in 4476 subjects with a mean
age of 72.5 years with no history of CVD.5 After a median follow-up
of 6.2 years, participants in the higher quintiles of maximal CIMT had
Cardiology in Review • Volume 24, Number 2, March/April 2016
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Cardiology in Review • Volume 24, Number 2, March/April 2016
CIMT and Cardiovascular Disease
FIGURE 1. Carotid intima media thickness. A, Normal CIMT; (B) CIMT measurement; (C) diffuse thickening of intima media;
and (D) atheroma in the carotid bulb.
an increased relative risk (RR) for MI or stroke compared with those
in the lower quintiles. A linear increase in RR of MI or stroke was
apparent across all quintiles, with the highest risk evident in the highest
quintile compared with the lowest risk in the lowest quintile.5
In the Carotid Atherosclerosis Progression Study (CAPS),6
5056 subjects had CIMT measurements and were followed up for MI,
stroke, and death over an average of 4.2 years. An increased unadjusted
hazard ratio (HR) for CIMT was found for all outcomes, and following
modification for age, sex, and vascular risk factors, CIMT was predictive for MI (HR, 1.16; 95% confidence interval [CI], 1.05–1.27) and
for MI, stroke, or death (HR, 1.16; 95% CI, 1.05–1.28). In a 10-year
cohort study of over 5000 participants living in Malmo, Sweden,
CIMT, carotid plaque, and carotid stenosis were associated with future
adverse CV outcome (ST elevation MI and non-ST elevation MI or
death).7 These relationships persevered after correction for the risk factors (0.15-mm increase in CIMT HR 1.23; 95% CI, 1.07–1.41).
In the Kuopio Ischaemic Heart Disease Study, 1288 Finnish men were followed for 2.5 years, where an increase in CIMT
by 1 mm or more demonstrated a 2.2-fold increased risk of MI.8 In
another study (Atherosclerosis Risk in Communities [ARIC]) 15,792
subjects aged 45–65 years were monitored across 4 communities in
the United States for 4–7 years after carotid ultrasound. It was found
that an increased CIMT was associated with an increased risk of
CAD (HR of 1.13 for MI per 0.1-mm increase in CIMT).9 The Cardiovascular Health Study observed 5888 adults aged ≥65 years for
© 2015 Wolters Kluwer Health, Inc. All rights reserved.
CV events for up to 12 years; 5020 of the subjects had no previous
history of CVD.10 It was demonstrated that the risk of CV adverse
outcome increased on migrating from low to high CIMT values.
The highest third had an 84% increased risk of CVD and a twofold
increased risk of death because of CVD.10
The Individual PROGgression of carotid Intima media Thickness
as a surrogate of vascular risk (PROG-IMT Project) evaluated CIMT in a
population of 36,984 subjects with the following inclusion criteria: individuals who had at least 2 CIMT assessments and a clinical follow-up
after the second ultrasound with records of any MI, stroke, and death.11
Participants were followed up for a mean of 7 years. The mean CIMT
was found to be associated with CV risk (HR, 1.16), but the study as
a whole discovered no association between CIMT progression and CV
risk. This suggested that a one-off baseline CIMT measurement can help
predict future adverse CV events, with CIMT progression not as effective, therefore limiting the use of this technique for CV screening.11
UTILITY OF CIMT IN THE PREDICTION OF ADVERSE
EVENTS IN HIGH-RISK GROUPS
Increased CIMT occurs in relation to various CV risk factors,
including HTN, smoking, hypercholesterolemia, and DM.12 Furthermore, an increased CIMT has been linked to future MI/CV death
and can be used as a screening tool for CV risk in high-risk patients
beyond information from recognized risk factors.12
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Cardiology in Review • Volume 24, Number 2, March/April 2016
Carpenter et al
In Patients With Vascular Risk Factors
In Patients With Diabetes Mellitus
A longitudinal cohort study performed in 7 centers across 5
European countries recruited 3482 participants with a median age
of 64.1 years. The cohort consisted of individuals with ≥3 vascular
risk factors (47.8% men) who were observed over 21.5 months.13
The aim was to investigate whether measures of CIMT progression were associated with subsequent risk of adverse CV events.
During this time, 129 subjects experienced a first vascular event,
and all CIMT measurements showed significant progression during the first 15 months (P < 0.001), but only those with maximal
progression (>1.5 mm) were significantly associated with the risk
of future CV events.13 This study demonstrated that large increases
in CIMT, in contrast to other progression variables, could be associated with CV risk.
CVD is the main cause of death in patients with type 2 DM
(T2DM).17 Identifying patients with a high probability of developing CV complications is therefore important for early prevention and
intervention, which could reduce their morbidity and mortality. A
recent review demonstrated that people with T2DM have a higher
CIMT than comparable non-diabetic people, with an average estimated difference of 0.13 mm after correction for risk factors, such as
age, risk of MI, and stroke.17 Another study on 150 subjects with DM
revealed a link between CIMT and CVD determined by CT coronary
angiography. Those with normal coronary arteries had the lowest
CIMT measurements (mean of 0.58 mm) and those with coronary
stenosis had the highest CIMT values (mean of 0.75 mm).12
A retrospective study assessed the relationship of CIMT progression with the risk of future CV events in 342 Japanese subjects
with T2DM who had no medical history of CV events.18 With at least
2 CIMT measurements carried out, these patients were followed for
a mean period of 7.6 years: 27 coronary events were recorded, with
a coronary event defined as a MI, unstable, or stable angina. Analysis
using the Cox proportional hazard model identified CIMT progression as a strong predictor of future CV events (HR, 2.24; P < 0.01).
Kaplan-Meier curves were also used in the multivariate analysis showing a significantly higher rate of CV events in patients with high CIMT
progression (>0.03 mm) compared with those with low CIMT progression (<0.01 mm). In addition, those with an initial high CIMT baseline
(>1.1 mm) who later had a high CIMT progression were shown to be at
a substantial risk of future adverse CV outcomes (HR, 5.89; P < 0.001)
compared with those with a low initial CIMT baseline (<1.1 mm).18
In Patients With Prior CVD
The Rotterdam Study determined the influence of CIMT in
predicting future CAD in 374 subjects with a previous stroke or
MI history, aged 55 years and above, who were followed up over
a mean period of 4.2 years.14 These subjects were evaluated to see
whether CIMT contributed to the prediction of a new MI. Receiver
operating characteristic (ROC) curves were used to measure the
prognostic value of the traditional risk factors added to the CIMT
measurements. The ROC area with age and sex was 0.65 (95% CI,
0.62–0.69). Risk factors included previous MI, stroke, DM, smoking,
systolic blood pressure (BP), diastolic BP, total, and HDL cholesterol
levels, which augmented the ROC area from 0.65 to 0.72 (95% CI,
0.69–0.75). When CIMT was added to the previous model, the ROC
area increased to 0.75 (95% CI, 0.72–0.78).
Data from the Second Manifestations of ARTerial Disease
study (SMART), a prospective cohort study following patients
with pre-existing arterial disease, have demonstrated that CIMT
can aid in the prediction of new vascular events.15 Patients
(n = 2374), primarily male (76%) with a mean age of 60 years,
were studied over a period of 2.8 years. CIMT values ranged from
0.36 to 4.52 mm, with a mean of 0.95 mm. Of the initial cohort,
225 patients experienced a new CV event (MI, unstable angina,
or stable angina), with 125 of those dying from it. An increase in
CIMT was related to an increased risk of future CV events (HR,
1.18; 95% CI, 1.04–1.32). The risk of stroke (RR, 1.35; 95% CI,
1.16–1.59) associated with an increase in CIMT was higher in
comparison with RR in association with CV events (RR, 1.19;
95% CI, 1.02–1.38).
The value of age-normalized CIMT in predicting future
adverse CV events was evaluated in the University of Virginia Study16
where CIMT was measured in 727 patients with an intermediate
risk of atherosclerosis, who ranged from age 16 to 85 years, with an
average age of 57.5 years. Of those patients, 706 were followed up
over a mean period of 4.78 years to determine clinical CV outcomes,
with their details entered into a database where age-specific quartiles
and odds ratios (ORs) in relation to CIMT were calculated. Twenty
patients had major adverse CV events: 7 patients had MI with another
7 requiring revascularization. Carotid bulb and internal carotid artery
(ICA) intima media thickness (IMT) measurements were considerably higher in patients who experienced a CV event compared with
those who did not. The OR for future adverse CV outcomes was 5.8
(95% CI, 1.3–26.6) in the highest quartile compared with the bottom
quartile in relation to CIMT measurements. Similar results were seen
with ICA IMT (P =0.03) with the OR for future CV events being 7.4
when comparing highest with lowest quartile in terms of thickness.16
However, the limitations of this study include small sample size in
comparison with other studies based on CIMT. Therefore, further
investigation using larger sample sizes could improve the reliability
and validity of CIMT findings.
72 | www.cardiologyinreview.com
In Patients With Chronic Kidney Disease
Given CVD is a leading cause death in patients with CKD,
it is important to evaluate the possible links between CIMT and the
future risk of poor CV outcomes in this category of patients.19 The
increased risk of CV death may be due to progressive atherosclerotic vascular changes, which can be assessed by CIMT. CIMT was
increased in patients with CKD (mean 0.81 mm), particularly those
who have concomitant DM.19,20 A prospective cohort study examined
whether CIMT could predict CV mortality in patients with CKD.19
Subjects with CKD (n = 438) who were treated with hemodialysis
had their CIMT measured by B-mode ultrasound. They were followed up over 30 months, during which time there were 82 deaths
and 44 others who experienced CV events, including MI, abdominal
aortic aneurysm, and cerebral hemorrhage. Subjects with a range
of CIMT values were compared (<1.0 mm, 1.0–2.0 mm, >2.0 mm).
Those with severe CIMT (>2.0 mm) had a significantly greater risk
of CV-related death (P < 0.0001).
Another study aimed to determine the predictive value of CIMT
and indicators of arterial stiffness, such as aortofemoral pulse wave
velocity [PWV (a-f)], with CVD outcomes in CKD patients. The study
consisted of 315 subjects with stage 4 to 5 CKD, aged 24 to 79 years,
with a mean follow-up of 3.6 years.21 During this follow-up, 95 CV
events occurred, and through analysis by the Cox proportional hazard
model, it was found that mean maximum CIMT and PWV (a-f) were
predictive of these CV events. However, after adjustment for age, sex,
BP, and risk factors such as DM, cholesterol level, and smoking, PWV
(a-f) was shown to be an independent predictor of CV events, whereas
CIMT was not. The higher prevalence of CV risk factors in the CKD
population could overshadow any independent role exhibited by CIMT
as CIMT does not replicate the complex arterial processes and mechanisms that can lead to CV events in CKD patients.21
In Patients With Hypertension
Zielinski et al22 examined CIMT as a marker of CV risk in
high-risk patients with existing HTN and CAD, to determine the risk
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Cardiology in Review • Volume 24, Number 2, March/April 2016
of future CV events. Subjects (n = 297) with a mean age of 57 years
were followed up for a mean of 41 months: 99% of the patients with
a low CIMT (<1.13 mm) survived for 5 years compared with 78% of
those with a high CIMT (>1.13 mm; P < 0.001). In those with low
CIMT, event-free survival was 95% compared with 74% in subjects
with high CIMT (P < 0.008), indicating that CIMT is a predictor of
death and CV events in patients with HTN and CAD. These results
highlight the possibility of using this method for CV risk, and even
though these patients were on optimal medical therapy for high BP
and cholesterol, increased CIMT could still be detected. However, it
must be noted that there were limitations to these findings. A sample
size of <300 using consecutive patients receiving coronary angiography is not representative, as it was not a random sample. The followup period was short in duration with the cutoff value for high CIMT
arbitrary and not necessarily used in other studies.
UTILITY OF CIMT IN THE PREDICTION OF SEVERITY
OF ATHEROSCLEROSIS
Forty-five subjects (41% female) with a mean age of 61.4 years
underwent a neck computed tomography scan to determine the magnitude of atherosclerotic disease present, followed by CIMT analysis
using B-mode ultrasound.23 The results were initially categorized for the
presence or absence of carotid calcification, with approximately 50%
of the sample having a diagnosis of HTN or hypercholesterolemia. The
average CIMT in the right common carotid artery (CCA) was 0.95 mm
for those with calcification present compared with 0.86 mm in those
with no calcification (P = 0.14), whereas the average CIMT in the left
CCA was 0.95 mm for those with calcification compared with 0.75 mm
in those without (P < 0.01). Mean CIMT was 0.91 mm with the median
total carotid calcium score being 48.4. The mean CIMT was 0.14 mm
greater in subjects with carotid calcification, with a 0.05-mm increase
in the CIMT associated with a 3 times higher risk of the presence of
atherosclerosis.23 A significant correlation between CIMT and atherosclerosis was demonstrated in this study with the extent of calcification
expressively associated with CIMT after adjustment for age. In addition, an increase in CIMT of 0.05 mm was associated with an increased
risk for the presence of calcification. An increase in sample size would
have provided additional validity and reliability to the results.
CIMT AS A SCREENING TOOL IN CARDIOVASCULAR
PREVENTION
Subjects from Spain (n = 325) over 30 years of age with low or
intermediate CV risk had their CIMT and subsequent 10-year risk of
CVD calculated in comparison with a reference population of French
citizens with a low CV risk.24 It was found that 18.4% of subjects had
CIMT values higher than the 75th percentile of the reference population,
indicating subclinical atherosclerosis which was not detected by traditional CV risk factors, such as BP, age, BMI, and a previous history of
hypercholesterolemia. The percentage detected by B-mode ultrasound
demonstrates that CIMT improves the stratification of risk in relation to
future CV events by highlighting its potential use in detecting subclinical atherosclerosis. However, one particular limitation was that there
were no CIMT reference values available in Spain; the CIMT reference values used were those of the population of France, with the study
assuming both regions would have the same level of CV risk, which
cannot yet be proven because of the aforementioned lack of data.24
IS CIMT A SOLITARY PREDICTOR OF
CARDIOVASCULAR EVENTS OR BETTER WITH
ADDITIONAL RISK SCORES?
The American Heart Association currently advises that CIMT
should be included in the assessment of atherosclerotic risk.25 Solitary
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CIMT and Cardiovascular Disease
CV risk factors have a limited capacity to predict the progression of
CVD, but risk stratification can be improved by integrating risk factors into models of risk, such as the Framingham risk score.26 CVD,
which has a relatively prolonged asymptomatic phase, has been in
need of fresh ways to categorize the stages of arterial disease from
subclinical to clinical form. Presently, CVD risk is evaluated by using
the Framingham or Systematic Coronary Risk Evaluation (SCORE)
risk scores based on an individual’s lipids, BP, and smoking results,
with those who score poorly at a higher risk of CV complications
and treatment.27 Whether CIMT as a predictor of future adverse CV
events is better when added to such predictive scores, or is more useful as a solitary biomarker, is examined below.
Framingham Offspring Cohort Study
In total, 2965 members of the Framingham Offspring Cohort
Study had their CIMT measured and their CV outcomes evaluated
over a 7-year period.28 Of those participants, 296 had a CV event
(MI, angina, or stroke) with risk factors from the Framingham Score
predicting this (C statistic of 0.748). A tool called “net reclassification” was used, where reclassification assigned those in whom CVD
developed to a higher risk category and those in whom CVD did not
develop to a lower risk category. The net reclassification index also
acknowledges movement between categories in the reverse direction
than predicted (high to low risk). Reclassifying these scores to include
the intimal thickness of the ICA and CCA showed an increase in net
reclassification index of 7.6% with the ICA (P < 0.001) but not with
CIMT (0%, P = 0.99), showing that only ICA IMT improves the classification of CV risk when added to the Framingham Score.28 CIMT
is safe, causing no radiation exposure, and is relatively inexpensive.
With results from CIMT measurements being highly reproducible, it
can be used as an independent predictor of CV events. In addition,
CIMT can add supplementary information to established risk assessment processes such as the Framingham Score.29
The Paroi Arterielle et Risque Cardiovasculaire Study
This study based on 6416 patients demonstrated that despite a
large amount of similarity between the Framingham Risk Score and
CIMT, there was a significant variation in one parameter, suggesting
that CIMT provides supplementary information to the Framingham
Risk Score.30 CIMT measurements were performed along with the
Framingham score for each individual, and a significant positive correlation was found between CIMT and all components of the Framingham score (P < 0.005). For example, a Framingham score of 20
was matched with a CIMT value of 0.9 mm, with Framingham risk
score increasing as CIMT increased, suggesting that CIMT provides
information to complement the Framingham score.30
The Multi-Ethnic Study of Atherosclerosis
The Multi-Ethnic Study of Atherosclerosis (MESA) aimed
to determine whether CIMT could provide additional prognostic
information to traditional risk scores such as Framingham, to predict future adverse CV events.31 Subjects aged 45 to 84 years who
had no history of CVD were monitored for 5.3 years. The data were
collected using ROC curves, showing a value of 0.77 for risk factors alone (HTN and plaque presence) and a value of 0.78 for CIMT
added to the risk factors, demonstrating that adding CIMT to risk
factors did not significantly enhance the prediction of CV disease.31
The Strong Heart Study
Studies examining the prognostic value of CIMT in predicting
future CV risk have not always assessed CIMT and the presence of
plaques separately. A plaque is a direct demonstration of the presence
of atherosclerosis, whereas CIMT is thought to be a measure of early
atherosclerosis. Because of this discrepancy, the Strong Heart Study
aimed to assess the individual prognostic value of CIMT and plaque
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Cardiology in Review • Volume 24, Number 2, March/April 2016
Carpenter et al
progression in a population with widespread HTN and DM.32 Subjects (n = 2441) with no history of CVD and a mean age of 63 years
were followed up for a mean period of 7.7 years: 65% of the participants were female, with a mean BMI of 31.3 kg/m2. The prediction of
CV events was assessed by the presence and extent of atherosclerosis,
along with the CIMT. Of the 2441 subjects, 495 (20.3%) experienced
a CV event [101 MIs, 204 CAD (defined as presence of atheroma),
98 strokes and 98 with congestive heart failure] with 21.4% of these
events leading to death. Both CIMT and the presence of plaques were
strongly associated with the prediction of stroke, but CIMT showed
a weak correlation in predicting future CV risk in those with HTN
and DM. In fact, CIMT was only predictive of CV outcomes in those
without CV risk factors present.32 However, there are some limitations to the Strong Heart Study. CIMT was only measured in the
distal section of the CCA, and not the ICA or the bifurcation, and the
study consisted of a specific patient group (American Indians) and
therefore cannot be generalized to other populations.
LIMITATIONS OF CIMT
Despite the plethora of data providing evidence for the effectiveness of CIMT as a marker for CV events, there are some limitations of CIMT that need to be highlighted. Along with the extent
of the atherosclerosis, the existence or absence of lesions with a
necrotic core might be reflected upon as a key indicator of future
risk.33 CIMT measurements do not distinguish between normal tissue
and a necrotic core. Thus, measurements of the plaque composition
are generally thought to be better predictors of atherosclerotic disease rather than CIMT.34 However, it needs to be realized that CIMT
and plaque do not necessarily reflect the same stage of the atherosclerotic disease process. CIMT abnormalities could be seen in early
atherosclerosis, when no plaques are present, and therefore be a valuable asset in assessing CV risk.34
IMT is generally acquired and measured in the CCA, but
advanced atherosclerotic disease occurs predominantly in the ICA.33
Having a necrotic core indicates advanced disease, with a necrotic
core defined as areas in which the extracellular matrix was lacking,
causing loss of collagen and replacement by dead cellular debris.35
CIMT struggles to distinguish between a simple lesion and a necrotic
core. This diagnostic investigation cannot tell how advanced the disease process is, and therefore how long the intimal thickening has
been present, with the accuracy of CIMT being hindered by the fact
that age-related thickening of intimal and medial layers of CCAs also
occur in the absence of atherosclerosis.36,37
Carotid atherosclerosis occurs mainly in the bulb region,
which is not easily visible with B-mode ultrasound.38 CIMT can also
be viewed as crude in its measurements as it fails to show the complex process of plaque evolution. A plaque grows 2.4 times faster
along the length of the carotid than it thickens, so CIMT may lack the
sensitivity to detect plaque progression soon enough.38 The question
remains whether a rise in CIMT corresponds to the level of atherosclerosis present. CIMT might simply reflect changes in vessel wall
because of stress.39 B-mode ultrasound cannot distinguish between
intima and medial layers. Pathological changes of medial and intimal
hypertrophy of the CCA can occur in the absence of atherosclerosis,
meaning there is potential for false-positive results and emotional
distress for patients and their families, questioning the fact whether
CIMT truly reflects the atherosclerotic process.40
CONCLUSIONS
CIMT is used increasingly as a marker for atherosclerotic disease. Whether CIMT is useful in predicting CV risk is still open to
debate. Currently, there is contradicting evidence that CIMT measurements improve CV disease prediction. Some evidence has indicated a
74 | www.cardiologyinreview.com
relationship between CIMT and a future risk of adverse CV events, but
this evidence is incomplete and requires further investigation. Methods
for measuring CIMT differ among studies, which could account for the
inconsistencies in published results. Most studies have reported results
using the mean CIMT, with others using the mean maximum CIMT
instead. These differences in methodology can limit the interpretation
of results and until a standard unit of measurement for CIMT is agreed
upon, discrepancies in findings may persist. The overall evidence has
only suggested that CIMT is a modest predictor of future adverse CV
events and not the revolutionary tool many had hoped. There is the
need for CIMT to be tested, established, and reviewed in relation to
traditional risk factors and high-risk populations.
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