Using imaging for cardiovascular risk prediction: an overview

Interrelationship between noninvasive predictors of atherosclerosis: transthoracic coronary flow reserve, flow-mediated dilation, carotid intima-media thickness, aortic stiffness, aortic distensibility, elastic modulus, and brachial artery diameter

BACKGROUND

In this study, we searched for a correlation between transthoracic coronary flow reserve (CFR) and well-established surrogates of coronary atherosclerosis.

METHODS

The study was conducted on 136 healthy subjects (mean age: 39.9 +/- 7.3 years) who were free of coronary risk factors. Transthoracic echocardiography was used to measure the aortic stiffness index (AoSI), aortic distensibility (AoD), and aortic elastic modulus (AoEM). High-resolution ultrasound was used to measure brachial artery endothelium-dependent and independent vasomotion and carotid intima-media thickness (IMT). In addition, transthoracic second harmonic Doppler echocardiography was used to measure CFR.

RESULTS

All of the parameters significantly correlated with each other except brachial endothelium-independent dilation. CFR correlated significantly with brachial endothelium-dependent dilation (EDD) (r = 0.302, P < 0.01), carotid IMT (r =-0.388, P < 0.01), brachial artery diameter (r = 0.340, P < 0.01), AoD (r = 0.275, P < 0.01), AoS (r =-0.299, P < 0.01), and AoEM (r =-0.30,7 P < 0.01). Carotid IMT correlated significantly with brachial EDD and modestly with brachial artery diameter, AoD, AoS, and AoEM.In multivariate analysis, carotid IMT (beta=-0.323, P < 0.0001) and brachial artery diameter (beta = -0.259, P = 0.001) were significant independent predictors of CFR. The left ventricular mass index (beta= 0.371, P < 0.0001), brachial EDD (beta = -0.232, P = 0.002), and CFR (beta = -0.228, P = 0.003) were significant predictors for IMT.

CONCLUSION

Transthoracic CFR correlated significantly with well-established noninvasive predictors of atherosclerosis, and we suggest that it can be used as a surrogate for coronary atherosclerosis.

Carotid intima–media thickness

In advanced countries the incidence of cardiovascular diseases is constantly increasing. During the last century many resources were employed to investigate atherosclerosis in relation to the main risk factors and to modification of lifestyles. Technologies have been developed to identify atherosclerosis in the sub-clinical phase. Measurement of the carotid intima-media thickness (IMT) by B-mode ultrasound is a well-validated procedure to detect the early stages of atherosclerosis and to track progression of atherosclerosis whereas other techniques have limited utility because of their invasive nature or limited sensitivity and reproducibility. In comparison with angiography, B-mode ultrasound has greater sensitivity for detecting early atherosclerosis and plaques at risk of rupture. IMT is associated with the severity of atherosclerosis in different vascular districts and has been measured in several clinical studies in order to assess the influence of risk factors, therapies and diet. It is also validated for drug evaluation. In spite of this evidence IMT measurement is not routinely performed in patients with high and middle levels of risk for cardiovascular diseases. Scientific societies and specifically those involved in ultrasonography should promote wider recognition of the diagnostic power of ultrasonic IMT by emphasizing the low costs and low risk of use of the instruments and its major contribution to knowledge, evaluation and monitoring of the progression of atherosclerosis.