Intravascular ultrasound assessment of regional aortic wall stiffness, distensibility, and compliance in patients with coarctation of the aorta

Background: Impaired aortic pulsatility has been demonstrated by angiography in children and in studies of experimental animals with coarctation of the aorta. Objectives: The purpose of this study was to assess regional aortic stiffness, distensibility, and compliance before and after baloon dilation in patients with coarctation of the aorta. Methods and Results: Intravascular ultrasound examination was performed in 13 pediatric patients with the diagnosis of coarctation of the aorta to yield aortic diameter. Area transverse sections at both systolic and diastolic period were measured at three aortic levels: the proximal, distal, and coarctation segments. Balloon dilation was also performed in eight of 13 patients. By using pressures measured in the same areas, an aortic stiffness index (β) was calculated as In(Ps/Pd)/(Ds-Dd), where in is natural logarithm, Ps is systolic pressure, Pd is diastolic pressure, Ds is systolic diameter, and Dd is diastolic diameter. Aortic distensibility and an estimation of aortic compliance were also calculated. The β stiffness index of the coarctation and the proximal segments of the aorta were significantly greater than that of the distal segment of the aorta (p < 0.01). The aortic wall stiffness β index did not acutely change after successful balloon dilation, but the distensibility and compliance of distal aorta were nonetheless significantly decreased after balloon dilation (p < 0.01, p < 0.05) as a function of changes of pulsatility of flow. Conclusions: Abnormal proximal aortic stiffness may be a strong contributing factor that promotes the genesis of hypertension in patients with coarctation even after successful repair or balloon angioplasty.