The PARC-AALA trial: carotid artery intima media thickness revisited
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- Pantazopoulos, N.J. & Henein, M.Y. Int J Cardiovasc Imaging (2008) 24: 53. doi:10.1007/s10554-007-9220-1
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In this quite original trial the PARC-AALA investigators have studied the correlation between common carotid artery intima-media thickness (CCAIMT) and presence of carotid plaques with cardiovascular risk across several different populations. Normal controls from three continents were compared to a population with hypertension and dyslipidaemia. The gathering of information was strictly cross-sectional, with calculation of CCAIMT, estimation of carotid plaque presence and Framingham Cardiovascular Score (FCS) calculation. As CCAIMT increased, so did FCS. The same relationship was recorded between FCS and the number of carotid plaques. These findings were similar for all geographical regions. The authors conclude that the study clearly demonstrates a correlation between CCAIMT and FCS for these populations and propose this method as a diagnostic tool for the prediction of cardiovascular disease.
Despite significant advances in technology and campaigns for increased awareness and treatment of risk factors, ischaemic heart disease (IHD) remains the leading cause of death in developed countries and the third largest cause of death worldwide . For this reason there is an ongoing effort in the scientific community to better recognize new ways of early prognosis of IHD and of risk stratification. CCAIMT has been evaluated for this purpose for several years. There is an increasing number of publications suggesting that increases in CCAIMT are directly associated with a rise in cardiovascular and cerebrovascular disease incidence in adults [2–5] and that, therefore, this method is a valid diagnostic tool.
Nevertheless there are still a number of caveats which need to be taken into account before accepting the technique as universally valid. For example, most trials have taken place in developed countries or in homogeneous populations. More studies need to be undertaken in the developing world to establish that the technique produces reproducible results in patients with different socioeconomic circumstances and genetic characteristics.
It would also be useful to compare controls with patients with subjects possessing combinations of all classic cardiovascular risk factors. Is intima-media thickness, for example, more a better measure in dyslipidaemics and diabetics, or do smokers have a greater prognostic benefit?
Another question we have to answer is whether CCAIMT is useful as a “spot-test” diagnostic tool, or whether it can also be used for follow-up and estimation of risk modification. Although it correlates with increased cardiovascular events, data to support an association between the progression of intima-media thickness and these events is scarce . Longitudinal trials are finally starting to appear, with encouraging results .
Finally, now that data is available for correlation between CCAIMT and cardiovascular risk scores or the presence of atherosclerosis, it is time to estimate the ability of the test to withstand comparison against robust data such as morbidity and mortality. For example a recent study suggests that the FCS overestimates the absolute coronary risk in British men . Information about clinical events is already available, but for specific populations such as older adults rather than the general population . A trial using CCAIMT for predicting cardiovascular events in a wider population begs to be performed.
In summary, measurements of common carotid artery intima-media thickness have produced encouraging results for predicting cardiovascular disease. More research is needed before definitively adding the method to our clinical armamentarium.