Pressure Wave Transmission along theHuman Aorta
Introduction: When relating the systolic and diastolic levels of blood pressure recorded in a peripheral artery to corresponding levels in the proximal aorta, it is necessary to consider the alterations in amplitude and contour of the pressure wave that occur during propagation. Such alterations have been investigated in man and other animals. Studies of wave transmission in humans have been performed on normal healthy subjects and on a few patients with cardiac and vascular lesions . There are no comprehensive reports on wave transmission in patients with arterial disease, neither have any data been published on changes in transmission with age. This is surprising because transmission characteristics are determined to a great extent by the physical properties of the large arteries , which alter with age and in degenerative disease . The purpose of this report is to present data on pressure wave transmission from proximal aorta to iliac artery in human subjects, to demonstrate the changes in wave transmission that occur with age and accompany arterial degenerative disease, and to attempt an explanation of these changes on the basis of previous studies on models and experimental animals.
Methods: Forty-three patients whose ages ranged from 6 to 71 years were studied during diagnostic cardiac catheterization or during diagnostic arteriography. All patients were conscious but sedated and lying supine and flat. Adults were premeditated with pentobarbital, 50 to 100 mg, meperidine, 50 to 100 mg, and atropine, 0.2 to 0.4 mg, and children with meperidine, 2.75 mg/ kg, promethazine, 0.7 mg/kg, and chlorpromazine, 0.7 mg/kg.
In 38 patients the catheter was inserted percutaneous into the femoral artery in the groin and advanced to the aortic arch or ascending aorta. In one patient, the catheter was inserted into the right brachial artery and threaded down to the iliac artery. Catheter positions were determined fluoroscopically. Records were taken at short time intervals in the aortic arch, descending thoracic aorta at the level of the dome of the diaphragm (tenth thoracic vertebra or bottom of ninth thoracic vertebra), and abdominal aorta at the second lumbar vertebra, and in the iliac artery at the level of the sacroiliac joint. The whole procedure was completed in 3 to 5 minutes. In three patients, difficulties were encountered in inserting the catheter, and records were taken only at the peripheral sites. In 19 patients pressure records were taken in the ascending aorta as well as at the other four sites. The catheter was the one used for the diagnostic studies; it was 1.2 to 3.0 mm o.d., was made of barium-impregnated polyethylene or Dacron, and usually had two or more side holes within 1 cm of its open tip. Catheters used for selective celiac or renal arteriography had a curved end to engage the vessel
Pressure waves recorded between the ascending aorta or aortic arch and common iliac artery in three children. Position 1 is the ascending aorta, position 2 the aortic arch, position 3 the descending thoracic aorta at the level of the diaphragmatic dome, position 4 the abdominal aorta at the second lumbar vertebra, and position 5 the distal part of the common iliac artery at the level of the sacroiliac joint. The beginning of each wave corresponds in time with the peak of the R wave in the simultaneously recorded electrocardiogram.
Results: Figure 1 shows pressure waves recorded at different positions between the proximal aorta and iliac artery in three children aged 13, 11, and 10. The first child (R.C.) had aortic stenosis, the second (K.S.) had a normal aortic valve, and the third (D.H.) had aortic incompetence.All presumably had healthy arteries. Despite differences in the pressure wave generated in the proximal aorta, changes in the amplitude and contour of the wave during transmission were similar in all.
In the 11 children studied, pulse pressure increased by an average value of 55% between the aortic arch and iliac artery. A diastolic pressure wave was obvious in the abdominal aorta and iliac artery of 10 of the 11 children.