Aorta tapered

A 48-year-old man with an inflammatory aneurysm of the ascending aorta and severe heart failure due to massive aortic regurgitation was given a continuous intravenous infusion of milrinone O.Smicrograms/kg/ minute (1). His pulmonary arterial pressure fell and his symptoms improved over 7 weeks while he was taking corticosteroids. The diseased tissue was successfully replaced at operation and the milrinone was tapered uneventfully. 

Typical pressure and velocity fluctuations throughout the cardiac cycle in man are shown in Figure 56.3 Although mean pressure decreases slightly toward the periphery due to viscous effects, peak pressure shows small increases in the distal aorta due to wave reflection and vessel taper. A rough estimate of mean... 

Velocity varies across the vessel due to viscous and inertial effects as mentioned earher. The velocities in Figure 56.3 were measured at one point in the artery. Velocity profiles are complex because the flow is pulsatile and vessels are elastic, curved, and tapered. Profiles measured in the thoracic aorta of a dog at normal arterial pressure and cardiac output are shown in Figure 56.4. Backflow occurs during diastole, and profiles are flattened even during peak systohc flow. The shape of the profiles varies considerably with mean aortic pressure and cardiac output [Ling et al., 1973]. 

The aorta is tapered, but most other arteries can be considered to have a constant diameter between branches. The rate of taper varies from individual to individual, presumably, between species. However, in the dog, the change of aortic cross sectional area can be described by the exponential equation ... 

Technical Considerations Catheterization of the bronchial arteries is best approached from the femoral artery. Since most patients with lung cancer are older and the aorta is tortuous and atherosclerotic, a 5-F catheter with good torque control in a shepherd s crook (reverse curve) or forward seeking configuration is recommended. A finely tapered tip catheter for access which would allow a 3-F microcatheter coaxial system is optimal to bypass the spinal artery. The use of nonionic contrast media should minimize pain and the risk of contrast media-induced complications. The digital subtraction technique is of value for the identification of the anterior spinal artery with small branches to the spinal cord. 

It is instructive to estimate Sh at the end of a straight tube having dimensions and flow rate characteristics of the human aorta (actually a tapered tube). Table 9.1 compares Sh and Da (for O2, ATP, albumin, and LDL) at the end of a 60-cm long model aorta having a diameter of 1 cm and a flow characterized by Re = 500. 

---