J. D. Beard

Does the in situ technique for autologous vein femoropopliteal bypass offer any hemodynamic advantage

The improved patency rates that have been claimed for in situ femoropopliteal vein bypass have been attributed to improved hemodynamics because of the natural taper of the vein and maintenance of wall compliance because of preservation of the nutrient vasa vasorum. Blood flow in 31 in situ and 21 reversed vein grafts was measured noninvasively with a duplex ultrasound scanner at a median of 6 months after operation. There was no significant difference in the resting or hyperemic flows between the two groups (p much greater than 0.1). The compliance of 15 undisturbed and 15 fully mobilized in situ vein grafts was measured noninvasively by Doppler ultrasonography immediately after operation and at 3 months. There was a significant fall in compliance in both groups (p less than 0.001) but no significant difference between them (p much greater than 0.1). We have been unable to demonstrate any significant hemodynamic advantage with the in situ technique but believe that its use is still justified because of technically easier anastomoses and an improved utilization rate. Preservation of the vasa vasorum does not maintain wall compliance and complete mobilization of the vein relieves any uneven tension and ensures that all venous tributaries are ligated, removing the risk of arteriovenous fistulas.

Blood flow to the limbs

The blood flowing into the limbs supplies skin, subcutaneous tissue, muscle and bone. While blood flow to the bone, nerve and connective tissue of the limb is relatively constant, that to skin and muscle show a great range. The circulation to the skin, and especially that of the extremities, is determined by the need for temperature regulation so that any change in the blood flow in the resting limb occurs as a result of change in the local or ambient temperature. Enormous changes in blood flow to skeletal muscle occur during exercise in response to the workload, and continue afterwards in repayment of the flow debt incurred during exercise. Thus, the resting blood flow is determined by temperature, and exercising blood flow by the degree of muscle activity.

Persistent bilateral sciatic arteries—an unusual presentation

A 20-year-old m an suddenly developed a cold white painful left lower leg after playing football a l though there was no history of t rauma. On examinat ion no pulses were palpable or detectable with Doppler u l t rasound below the left c o m m o n femoral artery. A right t ransfemoral lumbar aor togram (TFLA) demonstra ted bilateral persistent sciatic arteries with intimal irregularity at the level of the ace tabulum on the left (Fig. 1) and occlusion of all 3 calf vessels (Fig. 2). The superficial femoral ar tery was complete on the right, rejoining the sciatic ar tery at the knee but was incomplete on the left (Fig. 3). A diagnosis of thrombosis and subsequent embolism at the site of an intimal tear was made and a low dose infusion of streptokinase 6 0 0 0 uni ts /h commenced via a catheter advanced down to the popliteal artery. After 24 h the left foot was w a r m and pink but still pulseless and the streptokinase infusion was replaced by an in t ravenous heparin infusion 40 000 uni t s /24 h for 5 days. However, the foot again became critically ischaemic with rest pain and a Doppler pressure index of only 0.39. A repeat TFLA 1 week later showed tha t the irregularity in the left sciatic artery had been replaced by slight dilatation raising the possibility of an aneurysm a l though a mass in the buttock was not detectable clinically or by ul t rasound scanning. All 3 calf vessels were still occluded and so a lumbar sympathec tomy and popliteal embolectomy was performed. Organised th rombus was retrieved

The investigation of extracranial carotid disease

Duplex sonography combines the ability to real time image the carotid artery and accurately sample the vessel using pulsed Doppler. The flow information is presented graphically as velocity vs. time (Figure 8.1). It has become possible to color encode the velocity information and superimpose this upon the 2D gray-scale image — color flow Doppler. The color of each pixel displayed is the mean velocity and not peak velocity. It is standard practice that color flow Doppler is used quickly to locate and identify vessels and areas of turbulence; pulsed Doppler is then used to quantify flow accurately (Figure 8.2). ‘Power flow’ Doppler is a more recent development that analyzes the amplitude of the returning signal rather than frequency and direction. The signal is sensitive to flow, has a high signal to noise ratio and is less dependent upon the angle of insonation than pulsed or color flow Doppler. However, the image does not produce information on either peak velocity or direction of flow and is one of anatomy rather than function.

Stroke epidemiology and risk factors

Stroke is one of the most devastating of human illnesses and the most common life-threatening neurological disease [1]. Although stroke is more often disabling than lethal, it is still the third most common cause of death in the Western world after coronary heart disease and cancer [2,3]. According to a consensus statement on stroke, ‘Every five minutes someone in the United Kingdom has a stroke’ [4]. Stroke patients occupy around 10% of bed-days in the NHS and account for about 5% of health-care expenditure [5]. At 12 months after stroke onset, about 25% of patients will be dead and a further 30% will be reliant on the help of others for at least some of their activities of daily life [6]. The mortality from stroke has been declining worldwide over the last 30 years. In the UK the overall mortality from stroke fell about 20% between 1976 and 1986 but it is still double that in the USA

Management of extracranial carotid disease

The first part of this chapter deals with the interventional indications for carotid artery disease based on the results of the recently published North American and European trials. The management of asymptomatic patients and those with acute stroke is also discussed.