Carotid risk reclassification in according with carotid intima-media thickness

I - Background

Preventing death and morbidity from cardiovascular disease (CVD) is a major challenge for the clinician. Risk factor assessment is the cornerstone of primary prevention and helps guide therapeutic strategy. However conventional risk factor assessment may not be sufficient to assess total risk. Identification of asymptomatic patients with advanced pre-clinical disease would allow us to establish early and intensive antihypertensive and lipid-lowering therapy.

II - Carotid intima-media thickness

The introduction of high-resolution ultrasonography has provided a reliable, reproducible, and non-invasive method to detect and monitor the progression of subclinical atherosclerosis. Increased carotid intima-media thickness (IMT) is associated with a risk of myocardial infarction, stroke, and death independent on conventional risk factors (1).

In view of these relationships, carotid IMT has been proposed as a surrogate for systemic atherosclerotic disease burden. Carotid IMT values greater than or equal to 75th percentile are considered high and indicative of increased cardiovascular risk (CVR) (2). In addition to IMT, carotid ultrasonography also provides information about the presence of plaque, lumen stenosis, and arterial remodelling.
In spite of these findings no guidelines have called for use of these tests in primary prevention.

III - Prospective evaluation

We performed a prospective evaluation in the city of Madrid, to assess the impact of carotid IMT and carotid plaque assessment in modifying the risk stratification of population with a low-intermediate cardiovascular risk (CVR) by clinical criteria. 320 voluntary people aged over 30 years with low-intermediate CVR according European Score were prospectively enrolled. Carotid IMT and plaque assessment was performed using high-resolution B-mode ultrasonography according with Mannheim Consensus(3).

Carotid IMT was defined as the average for the right and left common carotid IMT. Carotid IMT percentile was calculated using previous data as reference values4. Plaque was qualitatively defined as focal widening greater than 1.5 mm, relative to adjacent segments with protrusion into the lumen that is distinct from the adjacent boundary. All examinations were performed by cardiologists experienced in carotid ultrasound techniques, who were blinded to the risk factor status of the participants.

Mean age of patients was 58.9 ±12.7 years, and 171 patients (53.4%) were men. According with clinical criteria alone 104 patients (32.5%) were of low CVR and 216 (67.5%) of intermediate CVR. Mean carotid IMT was 0.62 +/- 0.13 mm, and carotid plaque was found in 35 patients (10.9%). Atherosclerosis screening with carotid ultrasonography changed the risk stratum in 59 patients (18.4 %), deemed as low or intermediate risk by clinical criteria alone, into a high CVR. Reclassification was more frequent in the intermediate CVR group (22.7% vs 9.6 %, p= 0.005), and was associated to age (p<0.001), history of arterial hypertension (p=0.002), and increased systolic blood pressure (p=0.05). 

Conclusion:

Our findings suggest carotid ultrasonography improves CVR assessment in asymptomatic patients assigned to low and intermediate CVR category according with the European Score. This method is particularly useful in patients classified at intermediate risk, because a considerable proportion of them had an abnormal IMT or carotid plaque, thus placing them in the high CVR category. This should be taken into account when estimating CVR of such patients. High-resolution B-mode ultrasonography could become an important tool in preventive medicine enabling identification of asymptomatic patients at high CVR.