MESA Measurements
Computed Tomography (CT) for Measurement of Coronary Calcium
Coronary calcium is a specific, quantifiable marker for the presence of coronary
atherosclerosis. Its presence closely follows epidemiologic patterns for
coronary atherosclerosis, with marked increases with age and higher prevalence
in men than women. It is associated with coronary risk factors and predicts
coronary disease and mortality. Repeat determinations over time are expected to
provide a measure of progression of atherosclerosis.
Magnetic Resonance Imaging (MRI) of the Heart and Carotid Artery
MRI is capable of determining soft tissue characteristics of the carotid artery
wall, including wall thickness, plaque size, composition and lumen size. The
potential for finding abnormalities related to small vessel disease of the
heart represents a tremendous opportunity for enhanced understanding of
ventricular dysfunction and congestive heart failure. MRI represents a
relatively new imaging modality for epidemiologic studies. For established risk
factors, MRI offers high degree of reproducibility and the ability to
successfully image left ventricular mass on a greater proportion of
participants than echocardiography. MRI is also much more sensitive to the
presence of disease.
Enhanced Grey-Scale and Doppler Ultrasound of Carotid Arteries
The well-established methodology for carotid ultrasound imaging and current
knowledge of its relationships to risk factors and disease will complement
information obtained from different imaging modalities. Ultrasound can serve as
a benchmark for determining whether risk associated with different measures of
vascular disease is additive, multiplicative, or only confirmatory. Examination
of gray-scale characteristics of carotid plaque will permit assessment of their
relationship to disease in other vascular beds.
Flow-Mediated Brachial Vasodilation
Endothelium-dependent vasodilation can be induced by reactive hyperemia and
measured by ultrasound imaging of the brachial artery. It is related to
coronary vasoconstriction, appears to precede clinical coronary heart disease,
and demonstrates a wide range of response even in young persons. Treatment
appears to improve endothelium-mediated vasodilation even in the absence of
significant decreases in measured stenosis. The addition of this functional
measure to strictly structural assessments will illuminate a critical aspect of
the physiology of progression from subclinical to clinical disease.
Ankle-Brachial Blood Pressure Index
The simple ratio of brachial systolic blood pressure to posterior tibial blood
pressure has been found to reflect blood flow adequacy in the lower extremity
and thus serve as an indirect measure of peripheral artery disease. Though
peripheral vascular disease may have a distinct risk factor profile, ankle-arm
index correlates strongly with prevalent cardiovascular disease and subsequent
mortality.
Arterial Wave Forms
A tracing of the contours of the arterial wave form at the radial artery will be
obtained to estimate compliance of the small and large arteries and the
augmentation index, which may relate to atherosclerosis and left ventricular
mass.