C.P. Shearman

Systemic effects associated with intermittent claudication. A model to study biochemical aspects of vascular disease

Patients with intermittent claudication were used as a clinical model to study the effects of transient episodes of ischaemia. Compared with age and sex matched controls significantly greater increases in serum lipid peroxides and urinary microalbumin occurred after exercise. These results suggest that even relatively minor ischaemic episodes, as occur with claudication, are sufficient to cause tissue damage which may be mediated by oxygen derived free radicals. There are also changes in renal permselectivity suggestive of a generalised increase in vascular permeability. These preliminary findings may have important diagnostic, aetiological and therapeutic implications for patients with vascular disease.

Falsely elevated ankle pressures in severe leg ischaemia: The pole test—An alternative approach

Ankle-branchial pressure indices (ABPIs), measured by sphygmomanometer and Doppler probe, are an accepted index of chronic leg ischaemia. However, tibial artery sclerosis or calcification decreases compliance, producing falsely elevated cuff occlusion pressures. Arterial cannulation is invasive and impractical, but by elevating the foot and measuring the height at which the Doppler signal disappears, ankle systolic pressure in mmHg can be derived. Using an 8MHz Doppler apparatus and calibrated pole, ankle systolic pressures measured by sphygmomanometer and elevation were compared in 49 severely ischaemic legs (40 patients). ABPIs were derived by dividing ankle systolic pressure by brachial pressure. Median (interquartile range) ABPI assessed by sphygmomanometry was 0.46 (0.35-0.56). Median ABPI measured by leg elevation was significantly lower at 0.21 (0.14-0.30), p < 0.0001, Wilcoxon. In 20 patients undergoing in situ vein bypass grafting, direct transducer-derived pressure measurements were obtained. Median ABPI for this method was 0.15 (0.11-0.27). No significant difference was found when compared with ABPIs derived by elevation, median 0.2 (0.13-0.31), p = 0.324, however median ABPI measured by sphygmomanometry was significantly higher at 0.37 (0.27-0.6), p = 0.0008. Correlation of elevation with transducer-assessed pressure measurements (r = 0.88) was closer than with cuff-derived measurements (r = 0.69). Pressures derived by leg elevation provide a more accurate index of severe leg ischaemia than sphygmomanometry, although the technique is limited to assessing pressures of less than approximately 60 mmHg. Falsely elevated ABPIs may underestimate the extent of disease in patients assessed for vascular reconstruction.

Assessment of intermittent claudication by quantitation of exercise induced microalbuminuria

Urinary albumin excretion rates, expressed as albumin-creatinine ratios (ACR, mg/mmol) were measured before and after exercise in 23 claudicants and 10 controls. The mean (range) resting ACRs in the claudicants and controls were 4.42 (0.2-34.6) and 0.77 (0.3-2.8) respectively (P less than 0.001). ACR increased after exercise by a mean of 153% in claudicants to 9.7 (0.2-48.1; P less than 0.001) with no change in controls, 0.79 (0.2-2.1). In patients with claudication there was a positive correlation between ankle pressure recovery time and the relative increase in ACR after exercise (r = 0.64, P less than 0.01). The post-exercise increase in ACR was reduced in all nine patients who underwent bypass surgery. Measurement of ACR after exercise appears to be related to severity of muscle ischaemia and may assist in the assessment of patients with intermittent claudication.

Effect of surgery on the systemic inflammatory response to intermittent claudication

The hypothesis that intermittent claudication initiates a systemic inflammatory response was investigated by studying the effect of exercise on markers of neutrophil activation and vascular permeability in 25 claudicants and 10 controls. Urinary albumin excretion, previously demonstrated to reflect vascular permeability, increased significantly after exercise in claudicants and was associated with decreased neutrophil filterability and increased serum lysozyme activity. No similar exercise-induced changes were seen in controls or in claudicants after successful arterial bypass surgery. These results suggest that intermittent claudication is associated with potentially deleterious systemic manifestations that are surgically reversible.

A clinical method for the detection of arteriovenous fistulas during in situ great saphenous vein bypass

Residual arteriovenous fistulas are a potential source of morbidity after femorodistal bypass operation has been performed with the in situ great saphenous vein graft. A review of our initial experience with 155 operations in which various methods of intraoperative detection were used showed that fistulas were overlooked in 27 cases (17.4%), causing graft thrombosis in 10 cases (6.4%). After the introduction of a rapid and simple intraoperative test that used retrograde irrigation of the graft, only three superficial fistulas were overlooked in 70 operations (4.2%), with no associated graft thrombosis. The test had no detectable deleterious effects and graft distension pressures were within acceptable limits.

Iloprost improves femoro-distal graft flow after a single bolus injection

A double-blind, randomised, placebo-controlled trial was conducted to study the effect of the stable prostacyclin analogue iloprost on femoro-distal graft blood flow. After completing femoro-distal reconstruction, 3000 ng of iloprost or placebo was injected into the graft over 2 min. Graft blood flow, measured by electromagnetic flowmetry, increased by a mean (range) of 94% (12 to 192%) in patients receiving iloprost (n = 15) compared to 6% (-34 to 53%) in controls (n = 16; p less than 0.0001, t-test). Increased graft flow, measured by duplex ultrasound, was maintained in the iloprost group over a 7 day period postoperatively (F = 5.2, p = 0.03; analysis of variance) and remained higher at 7 days (p = 0.007, t-test). Iloprost produces an immediate, sustained increase in graft blood flow after femoro-distal reconstruction and may therefore be of benefit in reducing the incidence of early graft failure.

Femoro-distal Graft Flow Augmentation with the Prostacyclin Analogue Iloprost

The possible application of the prostacyclin analogue Iloprost to improve the results of arterial surgery has been studied. On completion of femoro-distal reconstruction, intra-graft administration of Iloprost caused an increase in graft blood flow measured by electromagnetic flowmetry. Three thousand nanograms of the drug appeared to be the optimum dose and in 10 patients who received this amount the graft blood flow increased from a mean of 117.6 ml/min to 225.5 ml/min (P less than 0.01, Wilcoxon), a mean (range) increase of 127.9% (54-190) after 20 min. Iloprost requires further evaluation, but may be a useful adjunct to femoro-distal reconstruction.

The influence of patent branches on in situ vein graft haemodynamics

The effect of patent graft branches on intra-operative graft flow and pressure has been studied in 50 patients undergoing in situ vein femoro-distal arterial bypass. In 35 grafts in which patent branches in the calf and thigh were preserved as arteriovenous fistulae, release of temporary branch occlusion increased mean proximal graft flow by 178.6% in 32, and reduced distal graft flow by 49.7% in 30. Seventeen limbs had thigh fistulae only: release of temporary fistula occlusion produced a fall in distal graft flow in only three. We identified three types of fistula: (a) cutaneous branches usually found in the thigh, which do not affect graft flow; (b) perforator branches which increase graft inflow but have no effect on distal graft flow: (c) perforator branches which increase graft inflow and decrease graft outflow, and are most frequently found in the calf. Discrimination between these haemodynamically differing branches at operation proved difficult. Since patent branches never improve distal graft flow and may reduce it, we recommend that all fistulae are ligated at operation.

Anastomotic arteriovenous fistulae—Are they worth it?

An adjuvant distal arteriovenous fistula (ADAVF) has been claimed to increase arterial bypass graft flow and patency when run-off is poor but others have suggested that a patent fistula does not improve in distal limb perfusion. In 10 dogs, hind limbs were rendered ischaemic by proximal arterial ligations and then revascularised with vein grafts. In each dog an ADAVF was constructed on the left graft while the right was used as a control. Flow and pressure were measured in each graft and distal artery and the effect of temporary occlusion and release of the fistula noted. These measurements were repeated at re-operation 3 months later. Mean flow through control grafts was 83 +/- 8.57 (S.E.M.) ml/min, increasing to 146 +/- 22.89 (S.E.M.) ml/min with papaverine (P less than 0.001, Students t test), and was unchanged at 3 months. Mean flow in grafts with a distal A-V fistula was 250 +/- 41.68 (S.E.M.) ml/min with no change after papaverine, and an increase to 730 +/- 110.5 (S.E.M.) ml/min at 3 months (P less than 0.001, Students t test). However, arterial flow distal to the fistula was invariably retrograde at initial operation (20 +/- 3.0 S.E.M. ml/min), and this retrograde flow increased to 180 +/- 33.2 (S.E.M.) ml/min at 3 months (P less than 0.001, Students t test). Distal arterial pressure at initial operation fell from 88.8 +/- 3.35 (S.E.M.) mmHg to 10.8 +/- 1.01 (S.E.M.) mmHg with the fistula open. We conclude that in this animal model an adjuvant distal arteriovenous fistula may improve bypass graft flow, but is unlikely to benefit distal limb perfusion.

The anatomical basis for the route taken by Fogarty catheters in the lower leg

The infrapopliteal route taken by Fogarty catheters when introduced through a common femoral arteriotomy is uncontrolled. We studied the passage of a catheter into the femoral artery in twenty cadavers and related the infrapopliteal route taken, to the angles of origin of the three crural arteries. We then attempted to modify the direction of travel of the catheter by manipulation. In 85% of cadavers the catheter passed into the peroneal artery on each of three consecutive passes, and the tip arrested at mid calf. In 75% of cadavers a 30 degrees bend to the tip of the catheter allowed passage into the posterior tibial artery in which case, the catheter could always be passed into the foot. In only one instance, when the angle of origin was unusually narrow, could the anterior tibial artery be entered.