ITB melhora o Framingham Risk Score

Ankle Brachial Index Combined With Framingham Risk Score to Predict Cardiovascular Events and Mortality
A Meta-analysis Ankle Brachial Index Collaboration
JAMA. 2008;300(2):197-208.
Context Prediction models to identify healthy individuals at high risk of cardiovascular disease have limited accuracy. A low ankle brachial index (ABI) is an indicator of atherosclerosis and has the potential to improve prediction.
Objective To determine if the ABI provides information on the risk of cardiovascular events and mortality independently of the Framingham risk score (FRS) and can improve risk prediction.
Data Sources Relevant studies were identified. A search of MEDLINE (1950 to February 2008) and EMBASE (1980 to February 2008) was conducted using common text words for the term ankle brachial index combined with text words and Medical Subject Headings to capture prospective cohort designs. Review of reference lists and conference proceedings, and correspondence with experts was conducted to identify additional published and unpublished studies.
Study Selection Studies were included if participants were derived from a general population, ABI was measured at baseline, and individuals were followed up to detect total and cardiovascular mortality.
Data Extraction Prespecified data on individuals in each selected study were extracted into a combined data set and an individual participant data meta-analysis was conducted on individuals who had no previous history of coronary heart disease.
Results Sixteen population cohort studies fulfilling the inclusion criteria were included. During 480 325 person-years of follow-up of 24 955 men and 23 339 women, the risk of death by ABI had a reverse J-shaped distribution with a normal (low risk) ABI of 1.11 to 1.40. The 10-year cardiovascular mortality in men with a low ABI (0.90) was 18.7% (95% confidence interval [CI], 13.3%-24.1%) and with normal ABI (1.11-1.40) was 4.4% (95% CI, 3.2%-5.7%) (hazard ratio [HR], 4.2; 95% CI, 3.3-5.4). Corresponding mortalities in women were 12.6% (95% CI, 6.2%-19.0%) and 4.1% (95% CI, 2.2%-6.1%) (HR, 3.5; 95% CI, 2.4-5.1). The HRs remained elevated after adjusting for FRS (2.9 [95% CI, 2.3-3.7] for men vs 3.0 [95% CI, 2.0-4.4] for women). A low ABI (0.90) was associated with approximately twice the 10-year total mortality, cardiovascular mortality, and major coronary event rate compared with the overall rate in each FRS category. Inclusion of the ABI in cardiovascular risk stratification using the FRS would result in reclassification of the risk category and modification of treatment recommendations in approximately 19% of men and 36% of women.
Conclusion Measurement of the ABI may improve the accuracy of cardiovascular risk prediction beyond the FRS.

ITB e risco cardiovascular

Different Calculations of Ankle-Brachial Index and Their Impact on Cardiovascular Risk Prediction
Christine Espinola-Klein MD*, Hans J. Rupprecht MD, Christoph Bickel MD, Karl Lackner MD, Savvas Savvidis MD, Claudia M. Messow , Thomas Munzel MD, Stefan Blankenberg MD, for the AtheroGene Investigators
Background—An ankle-brachial index (ABI; ratio of ankle and brachial systolic blood pressure) <0.9 indicates peripheral arterial disease (PAD) and is a strong predictor of cardiovascular events. The aim of the present study was to address the prognostic value of different methods of ABI calculation.
Methods and Results—In 831 patients admitted with chest pain for diagnostic heart catheterization, blood pressure of both anterior and posterior tibial arteries was measured. ABI was calculated for each leg with the higher of the 2 ankle pressures (current definition of the American Heart Association) or with the lower of the 2 ankle pressures (modified definition) in relation to the higher of the left or right brachial systolic blood pressure. For each patient, the lower ABI from both legs was used for further evaluation. Fifteen patients (1.8%) with ABI >1.5 were excluded. We compared patients with ABI <0.9 according to the current definition (with PAD, n=204 [25.0%]), those with ABI 0.9 according to the modified definition (without PAD, n=524 [64.2%]), and those with ABI <0.9 according to the modified definition and 0.9 according to the current definition (suspected PAD, n=88 [10.8%]). Follow-up data (median 6.6 years) were available for 812 patients (99.5%); 157 patients (19.3%) experienced cardiovascular events (cardiovascular death, myocardial infarction, or stroke). Patients without PAD had the lowest cardiovascular event rate, whereas event rates were comparable for patients with PAD and those with suspected PAD (14.8% versus 28.4% versus 25.0%, respectively). In a fully adjusted Cox regression analysis that included patients without PAD as the reference group, the hazard ratio (95% CI) was 1.56 (0.97 to 2.53) for patients with suspected PAD and 1.67 (1.16 to 2.40) for patients with PAD.
Conclusions—When the higher ankle pressure is used for ABI calculation, a group of patients at high risk for cardiovascular events is overlooked. With a simple modification of ABI (use of the lower instead of the higher ankle pressure), more patients at risk could be identified.