Aortic pulsation is caused by the arterial blood pressure variation during the cardiac cycle. Thickening of arterial intima, as well as the presence of atherosclerotic plaques may influence vessel pulsation by increasing wall stiffness. There is no data available concerning regional changes in aortic elasticity in relation with local wall thickness and the magnitude of atherosclerosis. The study group comprised 36 patients (27 men, 9 women, mean age 53 +/- 10 years) referred to our echocardiographic laboratory for transesophageal echocardiography (TEE). TEE probe was placed at the depth of 35 cm. The spatial interval between acquired images was 3 degrees. The reconstructed data sets were reviewed and the border between the aortic wall, plaque and lumen was determined. The reconstruction of a two-centimeter-long segment of aorta was divided by coaxial planes into four longitudinal sections. Thereafter the diastolic and systolic radius of each section, thickness of atherosclerotic plaques and intima-media thickness in each section were measured. The regional beta-index was calculated as Ln (systolic pressure/diastolic pressure)/relative change in regional aortic lumen, where relative change in regional aortic lumen was calculated as the difference between aortic lumen volume in systole and diastole divided by aortic lumen volume in diastole. In total, 144 aortic sections were analyzed. The volume of two-centimeter-long segments of descending aorta ranged from 6.9 cm3 to 31.5 cm3 (mean 12.8 +/- 5.2 cm3) in systole and from 4.9 cm3 to 29.2 cm3 (mean 11.2 +/- 4.9 cm3) in diastole. The volume of the examined sections of the aortic segments ranged from 1.3 cm3 to 10.6 cm3 (mean 3.2 +/- 2.6 cm3) in systole and from 1.1 cm3 to 8.7 cm3 (mean 2.8 +/- 1.5 cm3) in diastole. The pulsation of the aortic sections varied from 0.01 cm3 to 2.7 cm3 (mean 0.4 +/- 0.3 cm3), which constituted 0 to 37% (mean 13 +/- 8%) of the section volume. The thickness of atherosclerotic plaques in the studied aortic sections ranged from 0.0 mm to 1.1 mm (mean 0.3 +/- 0.2 mm) and the intima-media thickness was within the range 1.3 mm to 2.5 mm (mean 1.9 +/- 0.3 mm). The regional beta-index of the individual section ranged from 1.1 to 253.9 (mean 9.3 +/- 24.3). The regional beta-index was statistically significantly dependent on the intima-media thickness (p=0.02). We found no significant correlation between beta-index and the thickness of atherosclerotic plaques in the studied segments (p=0.38).
Conclusions: Transoesophageal three-dimensional echocardiography facilitates quantitative analysis of aortic wall stiffness and regional beta-index measurements. The local variability of beta-index is correlated with intima-media thickness, whereas the correlation with the thickness of atherosclerotic plaques is not statistically significant. These measurements may be of importance in the assessment of the degree of atherosclerosis advancement. It forms new perspectives in diagnostics with the ability to evaluate the influence of pharmacotherapy and life-style modifications.