The volume distensibility of the descending thoracoc aortic wall and the effect of nifedipine on the volume distensibility : clinical study using radionuclide angiograpy

To evaluate the circumferential volume distensibility (Dc) of aortic wall and the effects of nifedipine (NIF) on the Dc of aortic wall, 53 patients with various heart diseases and 7 normal persons were studied with use of non-invasive ECG-gated radionuclide angiography. Their mean age was 66±11 years. The time- activity curves at the portions of the upper decending thoracic aorta (A_1), and the lower descending thoracic aorta (A_2) were generated under the control state and after oral NIF of 10mg. TheDc of aortic wall at each portion was expressed as 100 △ V /V_0/PP, where △ is difference between maimum (systolic) and minimum (diastolic) volume (＝V_0) of aorta, and PP is pulse pressure. After oral NIF, blood pressure decreased and heart rate increased significantly from 147±26/80±15mmHg to 122±20/67±12mmHg and from 67±11/min. to 73±12/min., respectively. The Dcs at portions od A_1 and A_2 under the control state are 0.28±0.13 and 0.23±0.11%/mmHg, respectivery. Therewas significant difference in the Dc between these two portions. After oral NIF, the Dcs incresed significaantly both at the portions of A_1 and A_2, from control values to 0.36±0.12 (P＜0.001) and 0.34±0.13%mmHg (P＜0.001), respectively. The ratios of the value after oral NIF to controlstate were 1.39±0.38 and 1.63±0.69 at the portions of A_1 and A_2, respectively and there was significant difference in the ratio between these two portions. These results indicate that the Dc of the decending thoratic wall is lower at the distal aorta than that at the proximal aorta. NIF increases the Dc more at the distal aorta than at the proximal aorta, so that the difference of the Dc between two potrions of aorta becomes smaller after oral NIF than under the control.