| BackgroundCompliance and distensibility are physical properties of large arteries. Arterial compliance reflects the buffering capacity of an artery. Compliance of large conduit arteries has been found to be decreased as a result of aging, arterial hypertension, atherosclerosis, diabetes, and heart failure. A decrease in aortic compliance increases cardiac and vascular load and leads to increase in systolic pressure and pulse pressure, an independent risk factor for development of cardiovascular disease. With recent reports suggesting that arterial wall compliance is improved by drugs acting on vascular structure or endothelial cell or smooth muscle function, estimation of central aortic compliance in clinical settings may become more relevant.Although the central aorta , acting as a compliant tube that buffers and conducts pulsatile ventricular output, contributes most to total compliance of the arterial tree, most studies employing noninvasive imaging modalities have focused on evaluating superficial arteries such as the carotid, brachial, and femoral arteries. Recently, aortic compliance in humans has been studied using two-dimensional and transesophageal echocardiography and invasive intravascular ultrasound, but noninvasive evaluation of aortic compliance with Doppler-derived pulse wave velocity(PWV) is rarely reported.ObjectiveTo determine clinical value of Doppler-derived PWV in evaluating aortic compliance and assess the effect of age and blood pressure on aortic compliance .SubjectsThe study group consisted of 63 normal subjects without a history of cardiovascular disease and with a normal physical examination, electrocardiogram and echocardiogram (31 male and 32 female; ranging in age from 38 to 82 years; mean 41 ±16 years ) and 20 hypertensive patients (6 male and 14 female; ranging in age from 14 to 73 years; mean 60 ±11 years ). Hypertensive patients had systolic blood pressure ≥140 mm Hg or(and) diastolic blood pressure ≥90 mm Hg, or taking antihypertensive agents. All subjects had sinus rhythm.MethodsPWV along the descending thoracoabdominal aorta was measured non-invasively on the basis of Doppler ultrasound measurements in 63 normal subjects and 20 hypertensive patients, while using two-dimensional guided M-mode ultrasound measurements. We measured changes in arterial diameter of the right common carotid artery and calculated cross-sectional compliance (CC), distensibility coefficient (DC), the pressure-strain elastic modulus (Ep) and stiffness parameter (β ) from inner diameter, its pulsatile change, and blood pressure. The following formulas were used : DC=2ΔD /(Ds×ΔP), CC=ΔD× πΔDs/2ΔP, Ep=(ΔP/ΔD)×Dd, β=ln(SBP/DBP)/(ΔD/Dd), where SBP is systolic pressure; DBP is diastolic pressure; AP is the pulse pressure (=SBP-DBP); Ds is the inner diameter at systole; Dd is the inner diameter at diastole; ΔD is the change in diameter (=Ds-Dd). Of 30 subjects had their above indices remeasured approximately one an houre after their first measurements to document the reproducibility of the technique. All data were analyzed by SPSS 10.0 for windows software.Results1 PWV was negatively correlated to DC, CC and positively to Ep , β in all subjects.(DC: r = -0.655, P<0.01; CC: r = -0.562 , P<0.01; EP: r = 0.707 , P<0.01; β : r = 0.661 , P<0.01) .2 The indices of arterial compliance, except to CC, had no significant difference between men and women in normal subjects [PWV: 6.64±1.84 vs6.37±1.49m/s, P=0.528; DC:39.84±17.65 vs 38.43±12.62 (10-3/kPa), P=0.715; CC: 13.66±7.4 vs 10.49±3.66 C10-7m2/kPa), P=0.035; Ep: 55.06±25.46 vs 53.39±21.9 kPa , P=0.781; 0: 4.68±2.16vs4.39±1.63, P=0.563 ].3 The indices of arterial compliance had significant difference between hypertensive patients and age-and gender-matched normal subjects [ PWV : 8.92±1.59 vs7.94±1.14 m/s, p<0.05; DC: 16.83±5.23 vs28.34±9.83(10-3/kPa), p<0.01; CC: 6.15±1.7 vs 8.42±2.99 C 10-7m2/kPa) , p<0.01... |
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