Carotid Echo Doppler for Plaque Area Measurement in Cardiovascular Risk Stratification

PICHON RIVIERE, A.; AUGUSTOVSKI, F.; GARCIA MARTI, S.; GLUJOVSKY, D.; ALCARAZ, A.; LOPEZ, A.; BARDACH, A.; CIAPPONI, A; SPIRA, C

Documento de Evaluación de Tecnologías Sanitarias

IECS

Año: 2012 p. 1 - 30

1668-2793

Cardiovascular diseases (CVD) are the main cause of death worldwide. Since cardiovascular risk factors (RF) increase the likelihood of an event, overall risk assessment is critical. Currently, risk assessment scores have restricted sensitivity and discrimination power. Although used as screening methods to identify patients at risk of cardiovascular disease in an asymptomatic population, no-invasive methods are required to improve their predictive power. Atherosclerosis of the carotid artery is a strong predictor of a future ischemic event. High-resolution ultrasound carotid assessment may be useful to identify those "vulnerable" subjects beyond their cardiovascular risk as calculated by score. Non-invasive atherosclerosis detection should ideally involve safe, non-expensive, reproducible, reliable, non-invasive methods and lead to interventions that may have a beneficial impact on the natural history of the disease. Technology Total measurement of the plaque area is carried out by B mode ultrasonography associated with conventional echo Doppler of the carotid arteries. A specific software is required for data processing. Purpose To assess the available evidence on the efficacy, safety and use coverage policy related aspects of carotid echo Doppler for the measurement of the plaque area in cardiovascular risk stratification in asymptomatic patients. Methods A bibliographic search was carried out on the main databases: DARE, NHS EED, on Internet general search engines, in health technology evaluation agencies and health sponsors. Priority was given to the inclusion of meta-analyses, systematic reviews; controlled, randomized clinical trials (RCTs); health technology assessments and economic evaluations; clinical practice guidelines and coverage policies from other health systems. Results Two meta-analyses and one cohort study published at a later date were included. One meta-analysis included 11 longitudinal population studies (n=54,336) where asymptomatic subjects with no cardiovascular history were evaluated by carotid ultrasound and reported a CV event; and 27 diagnostic cohorts (n= 4,787) where patients with suspected CVD underwent carotid ultrasound and coronary angiography. The first type of studies showed that assessment of the carotid plaque by ultrasound had a higher diagnostic accuracy to detect future myocardial infarction than Carotid Intima-Media Thickness (CIMT). The Area Under Curve (AUC) for the carotid plaque was 0.64 (95% CI 0.61-0.67), while that for CIMT was 0.61 (95% CI 0.59-0.64; p=0.046). The second type of study evidenced that the assessment of the carotid plaque by ultrasound had similar diagnostic accuracy for coronary disease when compared with CIMT (AUC for plaque was 0.76- 95% CI 0.73-0.80, while that for CIMT was 0.74- 95% CI 0.72-0.76; p=0.21). Another meta-analysis published in 2009, assessed performance of the carotid ultrasound. Nineteen studies were included: 13 cases and controls and 6 cohorts, with 2,920 patients with CVD and 41,941 without disease. The overall result showed a 62% plaque detection rate (RD) (95% CI 50-75) and a 30% false positive rate (FPR) (18-39%). One cohort, included in the already mentioned meta-analyses, assessed 13,145 asymptomatic subjects for 15.1 years; it studied whether CIMT or the presence of plaque improves risk prediction in CVD versus the ARIC risk score. When including information about the carotid or plaque thickness to this score, the AUC significantly improves as it does when including it to the Framingham score (AUC 0.61 vs. 0.685 and 0.741 vs. 0.751 - in males and females, respectively). This cohort also measured the net reclassification index (NRI) when adding information about the presence of plaque with CIMT to the ARIC score, reclassifying 8.6%; 37.5%, 38.3% and 21.5% of the total sample in <5%, 5-10%,10-20% and >20% CV risk at 10 years respectively (NRI 9.9% total sample). One observational longitudinal study published in 2011, included 1,734 asymptomatic subjects 43-79 years old, with a 5-year follow up. RF AUC was 0.724 (95% CI 0.675- 0.773) while for RF plus TBS (a score made up by the CIMT of those who did not develop plaque and the number of segments with plaque from those who developed it) was 0.784 (95% CI 0.738-0.829) (p<0.01). In addition, TBS increases the risk prediction by 17.1% versus the risk score specifically used for this study. Clinical Practice Guidelines The American College of Cardiology considers that only the CIMT measurement is reasonable for the CV risk assessment in asymptomatic adults at intermediate risk. The American Society of Echocardiography recommends that carotid plaque identification may be useful to determine risk of CVD in patients at intermediate risks meeting certain requirements. The European Society of Cardiology recognizes this technique as useful but does not include it in its recommendations. The Canadian Society suggests that those individuals at moderate risk who have detected atherosclerosis by this technique are classified as at high risk. The Argentine Society of Cardiology and the Argentina Federation of Cardiology do not mention this practice. Conclusions At present, risk scores have an acceptable predictive value to predict a cardiovascular event. Since they have certain limitations it would be useful to complement them. There is no conclusive evidence that the plaque area is better than the CIMT, even when combining them, a RF-based score associated prediction is discretely improved. Some Cardiology Societies suggest the inclusion of these techniques in some groups at intermediate CV only. It is a safe technique but operator-dependent due to the marked inter and intra-observer variability. This technology may be included based on the availability of resources at each institution, however, the risk score are still the screening methods of choice for CV risk prediction in asymptomatic patients.