sábado, 20 de agosto de 2011

Internal carotid IMT slightly improves risk classification - by theheart.org


Boston, MA - Cardiovascular risk assessment can be modestly improved with ultrasound measurement of the intima-media thickness (IMT) of the internal carotid artery wall, a new study from the Framingham Offspring Study cohort shows [1].



Recent American College of Cardiology (ACC)/American Heart Association (AHA) guidelines on cardiovascular risk assessment in asymptomatic patients give carotid IMT—the distance between the lumen-intima interface to the media-adventitia interface—a level 2a recommendation, the same level as the ankle-brachial index and coronary artery calcium scoring, emphasizing that patients with a common carotid-artery IMT above the 75th percentile should be categorized as high risk.

However, "in primary prevention, the incremental predictive value of the IMT of either the common carotid artery or the internal carotid artery, over and above the value of traditional cardiovascular risk factors, is questionable," Dr Joseph Polak (Tufts Medical Center, Boston, MA) and colleagues write in the July 21, 2011 issue of the New England Journal of Medicine.

Polak and colleagues measured the mean and maximum IMT of the internal carotid artery in 2965 participants in the Framingham Offspring Study cohort. During a mean follow-up of 7.2 years, 296 participants had a cardiovascular event.

Traditional Framingham risk factors predicted these events with a C statistic of 0.748. For a one standard-deviation increase in maximum IMT of the internal carotid artery, the hazard ratio was 1.21, with a modest but statistically significant increase in the C statistic of 0.009. Reclassification of patients' cardiovascular risk was aided by adding the IMT of the internal carotid artery to the Framingham score; the net reclassification index—a statistical measure of how much a new factor improves the accuracy of a risk-prediction model—increased 7.6% (p<0.001).
However, the adjusted hazard ratio for cardiovascular disease associated with a one standard-deviation increase in common carotid artery mean IMT was 1.13 and the associated change in the C statistic of 0.003 was nonsignificant. The IMT of the common carotid artery did not improve reclassification; the net reclassification index did not change (0%, p=0.99).
In patients in whom carotid plaque was detected in the internal carotid artery, the net reclassification index was 7.3% (p=0.01), with an increase in the C statistic of 0.014. The presence of plaque in the internal carotid artery can either be measured as part of the continuous IMT or assumed to be there if the thickness exceeds 1.5 mm, Polak and colleagues explain

1. Polak J, Pencina M, Pencina K, et al. Carotid-wall intima-media thickness and cardiovascular events. N Engl J Med 2011; 365:213-221

Nenhum comentário:

Postar um comentário