SINGLE BEAT EVALUATION OF CIRCUMFERENTIAL AORTIC ELASTIN ELASTIC-MODULUS IN CONSCIOUS DOGS - POTENTIAL APPLICATION IN NONINVASIVE MEASUREMENTS

A description of the arterial wall elastic properties comprehends both collagen and elastin, clearly shown in a biphasic stress-strain relat ionship. From chronically instrumented conscious dogs, aortic pressure -diameter curves can be obtained in a single beat, which is impossible to perform in human beings. In control conditions, the collagen fiber s are almost not distended and the resistance to stretch is mainly sup ported by the elastin fibers. Therefore, the mechanical properties of the aorta are almost purely elastic in the basal beat to beat conditio ns. In this study we propose and test five indexes, which include as v ariables: systolic, diastolic and mean arterial pressure and diameter; besides, arterial compliance and pressure-strain elastic modulus as s uggested to evaluate the elastic behaviour of the elastic fibers. This data can be easily obtained by non-invasive methods, such as Doppler- ultrasound techniques and auscultative esphygmomanometrical measuremen ts, while the indexes evaluated can be retrieved from a single beat ev aluation. Of three measurements performed in chronically instrumented conscious dogs on different days, one of these indexes, the ME(5) = P- mean x R(mean) - P-dias x R(dias)/R(mean) - R(dias) x R(dias) proved t o be an accurate and reliable parameter to evaluate the mechanical beh aviour of arteries. This kind of parameter may be useful for research and evaluation of several diseases that markedly alter the arterial wa ll compliance.