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Davies AH, Magee TR, Horrocks M, 1994, Vein graft factors in the outcome of femorodistal bypass., Eur J Vasc Surg, Vol: 8, Pages: 249-256, ISSN: 0950-821X
Various vein factors affect the outcome of femorodistal bypass using vein in the treatment of lower limb ischaemia. In this review, the effect of factors such as vein size, compliance and morphology are discussed.
Magee TR, Davies AH, Baird RN, et al., 1994, Blood flow in the internal carotid artery and velocity in the middle cerebral artery during carotid endarterectomy., Cardiovasc Surg, Vol: 2, Pages: 37-40, ISSN: 0967-2109
A stenosing atherosclerotic plaque of the internal carotid artery acts as a source of emboli and may impede flow. The contribution made by a stenosed carotid artery to cerebral perfusion is unclear. This study examined blood flow in the internal carotid artery and a comparison was made with the effect of clamping on flow velocity in the middle cerebral artery. Some 50 patients were assessed before carotid endarterectomy by preoperative duplex scanning, triplanar arteriography and transcranial Doppler ultrasonography. At operation, maximal flow in the internal carotid artery was measured using a Doppler flowmeter and flow velocity was monitored by transcranial Doppler. No correlation was found between the degree of stenosis and resting flow velocity. Mean flow in the internal carotid artery in patients with > 90% stenosis was significantly lower than those with lesser stenoses (P < 0.01). However, a mean minimal blood flow of 141 ml/min passed through the > 90% stenoses. The effect of internal carotid artery clamping on flow velocity was similar irrespective of the degree of stenosis. In patients with > 90% stenosis, the internal carotid artery continues to make an important contribution to cerebral perfusion.
Horrocks M, Magee TR, Davies AH, et al., 1994, Blood flow in the internal carotid artery and velocity in the middle cerebral artery during carotid endarterectomy, Vascular, Vol: 2, Pages: 37-40, ISSN: 1708-5381
A stenosing atherosclerotic plaque of the internal carotid artery acts as a source of emboli and may impede flow. The contribution made by a stenosed carotid artery to cerebral perfusion is unclear. This study examined blood flow in the internal carotid artery and a comparison was made with the effect of clamping on flow velocity in the middle cerebral artery. Some 50 patients were assessed before carotid endarterectomy by preoperative duplex scanning, triplanar arteriography and transcranial Doppler ultrasonography. At operation, maximal flow in the internal carotid artery was measured using a Doppler flowmeter and flow velocity was monitored by transcranial Doppler. No correlation was found between the degree of stenosis and resting flow velocity. Mean flow in the internal carotid artery in patients with >90% stenosis was significantly lower than those with lesser stenoses (P < 0.01). However, a mean minimal blood flow of 141 ml/min passed through the >90% stenoses. The effect of internal carotid artery clamping on flow velocity was similar irrespective of the degree of stenosis. In patients with >90% stenosis, the internal carotid artery continues to make an important contribution to cerebral perfusion. © 1994, SAGE Publications. All rights reserved.
Ng RL, Davies AH, Magee TR, et al., 1994, Early reoperation rates after arterial surgery., Eur J Vasc Surg, Vol: 8, Pages: 78-82, ISSN: 0950-821X
Between 1 January 1985 and 31 December 1991, 2426 patients underwent arterial surgery. Three hundred and seventy one reoperations were performed on 258 patients within 30 days of the initial procedure. One hundred and ninety three (52%) of the operations were attempted revascularisations, 95 (26%) were amputations and 58 (16%) were to control bleeding. One hundred and sixty nine (66%) of first operations were successful, but 76 patients required a further 113 reoperations. The mortality of reoperation was 16%, while the mortality of patients not requiring reoperation was 9% (p < 0.01). The mean hospital stay in days was higher in patients requiring reoperation (p < 0.05). Where appropriate, patients should be informed of the significant incidence of reoperation and reoperative mortality after vascular surgery. The increased hospital stay in reoperated patients has financial implications.
Magee TR, Davies AH, Horrocks M, 1994, Transcranial Doppler evaluation of cerebral hyperperfusion syndrome after carotid endarterectomy., Eur J Vasc Surg, Vol: 8, Pages: 104-106, ISSN: 0950-821X
Cerebral hyperperfusion syndrome after carotid endarterectomy is rare. Unilateral headache, confusion, seizures or focal neurological signs may occur and intracranial haemorrhage may be a terminal event. We report a case of hyperperfusion accompanied by transient hemiparesis. The changes in cerebral perfusion were documented using transcranial Doppler sonography which helped to make the diagnosis.
Magee TR, Davies AH, 1993, Auditory phenomena during transcranial Doppler insonation of the basilar artery., J Ultrasound Med, Vol: 12, Pages: 747-750, ISSN: 0278-4297
During transcranial Doppler insonation of the basilar artery, 15 normal subjects heard high-frequency tones similar to tinnitus. The pitch of the tones equated with the PRF, and intensity equated with loudness. Alteration of pulse length did not change the tones heard, and the effect was highly dependent on probe position and direction. This is an example of ultrasonography acting as a sensory stimulus. The exact mechanism and implications of this effect will need to be clarified by further investigation. Although this phenomenon is not proved to be harmful, it would seem prudent to use the minimum transmitted power necessary to obtain a satisfactory signal from the basilar artery.
Sikovec A, Davies AH, Baird RN, 1993, Evaluation of distal runoff in femorodistal bypass., Cardiovasc Surg, Vol: 1, Pages: 619-623, ISSN: 0967-2109
Blann AD, Bushell D, Davies A, et al., 1993, von Willebrand factor, the endothelium and obesity., Int J Obes Relat Metab Disord, Vol: 17, Pages: 723-725
von Willebrand factor (vWf), risk factors for atherosclerosis, body mass index (BMI) and waist-to-hip ratio (WHR) were measured in 108 non-diabetic patients attending lipid and vascular disease clinics and in 107 normal asymptomatic controls. High levels of vWf and increased BMI relative to controls were found in patients with hyperlipidaemia and vascular disease, but WHR was higher only in patients with vascular disease. Total serum cholesterol concentration (P < 0.001), systolic blood pressure (P < 0.001), smoking (P < 0.02) and BMI (P < 0.001), but not WHR, were associated with vWf. As raised levels of vWf are a probable indicator of endothelial damage in vascular disease, these data suggest that obesity has an adverse influence on the endothelium and may help explain its link with cardiovascular disease.
Davies AH, Magee TR, Baird RN, et al., 1993, Pre-bypass morphological changes in vein grafts., Eur J Vasc Surg, Vol: 7, Pages: 642-647, ISSN: 0950-821X
Random vein samples taken prior to bypass surgery have shown certain pathological features. Long saphenous vein was taken from the groin (proximal) and knee to mid-calf (distal) of 85 patients undergoing femoro-distal bypass over a 2-year period. During this period only four patients had cephalic arm vein used; this was also studied. Histological examination was performed using haematoxylin and eosin and van Geison stains. Intimal hyperplasia was seen in 62 (73%) proximal and 74 (87%) distal samples. There were significantly more distal veins with moderate to severe focal hyperplasia and circular muscle hypertrophy (p < 0.05 and p < 0.001). Changes of diffuse intimal hyperplasia were seen in three of the cephalic veins. Muscle hypertrophy occurred in 58 (68%) of proximal segments compared to 75 (88%) of distal segments (p < 0.005). This study shows that significant pathological changes are seen in long saphenous and cephalic veins thought to be "normal". These changes are more evident in the distal long saphenous vein. These changes may have a significant effect on the outcome of vein bypass.
Davies AH, Magee TR, Baird RN, et al., 1993, Intraoperative measurement of vascular graft resistance as a predictor of early outcome., Br J Surg, Vol: 80, Pages: 854-857, ISSN: 0007-1323
The quality of distal run-off is one of the most important factors influencing the early outcome of femorodistal vein grafting. During femoropopliteal and infrapopliteal bypass, assessment of graft resistance and flow were made using a combination of Doppler flowmeter recordings and measurements of arterial pressure. In a series of 100 reconstructions there were 12 early failures. The mean (95 per cent confidence interval (c.i.)) maximal flow measurement in the group of grafts that failed when anastomosed to the popliteal artery or tibioperoneal trunk was 125 (74-176) ml/min compared with 256 (223-289) ml/min in successful grafts (P = 0.006). The corresponding figures for grafts inserted into a single crural vessel were 99 (72-126) and 165 (137-193) ml/min (P < 0.02). In the group that failed the mean (95 per cent c.i.) resistance after papaverine injection was 1.02 (0.82-1.22) peripheral resistance units (p.r.u.) compared with 0.47 (0.44-0.51) p.r.u. in the successful group (P < 0.001). Using a combination of resistance > 0.9 p.r.u. and capacity loss ratio after papaverine injection < 10 per cent to identify grafts that subsequently failed, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 92, 97, 85, 99 and 97 per cent respectively. These results confirm that haemodynamic measurements can be used at operation to identify a group of patients in whom bypass is likely to fail.
Davies AH, Magee TR, Thompson JF, et al., 1993, Preliminary experience of angioscopy in femorodistal bypass., Ann R Coll Surg Engl, Vol: 75, Pages: 178-180, ISSN: 0035-8843
During femorodistal bypass angioscopy can be used in vein graft preparation allowing valve lysis and the identification of tributaries under direct vision. A total of 30 patients have undergone angioscopic assisted femorodistal bypass using either an Olympus or Stortz system. Nineteen patients have undergone full vein mobilisation and valve lysis under direct vision. Eleven patients had in situ bypass with ligation of tributaries, identified by the angioscope, through small stab incisions. No evidence of fistula or retained valve cusps was found by subsequent duplex scanning and arteriography. One of these grafts failed at 6 days due to an unrecognised outflow stenosis. The mean hospital stay after operation for this latter group of patients was 5.2 days (range 4.4-6.0 days) compared with 9.5 days (8.6-10.3 days) in a historical group of 30 patients (P < 0.001). Angioscopy is a useful aid in the performance of femorodistal bypass. Early experience suggests that hospital stay may be reduced by angioscope assisted in situ femorodistal bypass because of the minimal dissection involved.
Davies AH, Magee TR, Thompson JF, et al., 1993, Stenting for vein graft stenosis., Eur J Vasc Surg, Vol: 7, Pages: 339-341, ISSN: 0950-821X
Davies AH, Horrocks M, 1993, Vascular assessment, surgery and the diabetic foot, Practical Diabetes International, Vol: 10, Pages: 52-54, ISSN: 1357-8170
Davies AH, Magee TR, Wyatt M, et al., 1993, Impedance analysis versus colour Duplex in femorodistal vein graft surveillance., Eur J Vasc Surg, Vol: 7, Pages: 14-15, ISSN: 0950-821X
Fifty patients who have undergone femorodistal bypass surgery have been followed up using impedance analysis and colour Duplex, with biplanar intraarterial digital subtraction angiography being used as the arbiter to define "at risk" grafts. An impedance score of 0.49 (0.43-0.55) was found in the "at risk" grafts, all of which underwent an interventional procedure compared to 0.39 (0.36-0.42) (p = 0.003, Mann-Whitney U test) in those with no problem. In total, 166 examinations were performed. The sensitivity and specificity were all greater than 91% when compared to angiography. Impedance analysis is simple, non-invasive, easy to perform and it takes only 10 min to complete the examination. In view of the results obtained using impedance analysis in comparison with Duplex scanning, we suggest that non-invasive impedance is a suitable alternative to colour Duplex for graft surveillance (mean +95% confidence interval).
Davies AH, Magee TR, Baird RN, et al., 1992, Prevention of malalignment during non-reversed femorodistal bypass., Ann R Coll Surg Engl, Vol: 74, Pages: 434-435, ISSN: 0035-8843
A simple technique is described using a Doppler flowmeter to prevent malalignment of a vein graft during femorodistal reconstruction. In 63 non-reversed vein bypass grafts, this technique has been used and no evidence of malalignment has been found on subsequent completion arteriography.
Cook TA, Davies AH, Horrocks M, et al., 1992, Amputation level is not adversely affected by previous femorodistal bypass surgery., Eur J Vasc Surg, Vol: 6, Pages: 599-601, ISSN: 0950-821X
Data was reviewed on patients presenting with lower limb-threatening ischaemia to a single vascular unit between September 1984 and December 1990. Three hundred and thirty patients underwent either femoro-popliteal or femoro-infrapopliteal reconstructive surgery and 316 primary amputations were performed on 281 patients. Sixty-three secondary amputations were performed following a femoro-distal bypass failure. The below-knee amputation to above-knee amputation ratio (BKA/AKA) was 1.0 in the primary amputation group to 0.91 in the secondary amputation group. A direct comparison cannot be made as the patients represent two separate clinical groups. The ratio of reconstructive operations to primary amputations more than doubled between the first and second halves of the study. The BKA:AKA ratio in the secondary amputation group and the total number of secondary amputations remained relatively constant. This study supports the view that previous femoro-distal surgery does not adversely affect the overall outcome of amputation.
Magee TR, Davies AH, 1992, Who should undergo carotid endarterectomy?, Br J Hosp Med, Vol: 48, ISSN: 0007-1064
Davies AH, Magee TR, Baird RN, et al., 1992, Vein compliance: a preoperative indicator of vein morphology and of veins at risk of vascular graft stenosis., Br J Surg, Vol: 79, Pages: 1019-1021, ISSN: 0007-1323
Compliance measurements of 53 long saphenous veins before femorodistal bypass have been performed using a duplex scanner with venous occlusion for distension. These have been compared with the histological features of the veins. There was significantly more moderate or severe focal hyperplasia and circular muscle hypertrophy in distal long saphenous vein than in its proximal counterpart (P < 0.01 and P < 0.05 respectively). The mean (95 per cent confidence interval) compliance of distal vein with moderate or severe hyperplasia was 0.16 (0.13-0.19) compared with 0.29 (0.22-0.36) for that with no, minimal or mild hyperplasia (P = 0.001). The mean compliance of distal vein with moderate or severe muscle hypertrophy was 0.19 (0.17-0.21) and of vein with no, minimal or mild hypertrophy 0.25 (0.21-0.29) (P = 0.14). The mean lowest compliance in seven patients who developed stenosis was 0.10 (0.07-0.13) compared with 0.21 (0.16-0.26) in the rest (P < 0.001). Preoperative measurement of vein compliance can be used to identify vein with marked pre-existing intimal hyperplasia and as a predictor of future graft stenosis.
Magee TR, Davies AH, Baird RN, et al., 1992, Transcranial Doppler measurement before and after carotid endarterectomy., J R Coll Surg Edinb, Vol: 37, Pages: 311-312, ISSN: 0035-8835
Carotid endarterectomy not only removes a source of emboli but significantly increases flow up the internal carotid artery (ICA). ICA flow and middle cerebral artery velocity (Vmca) measurements were made before, during and after endarterectomy in 40 consecutive patients. Mean ICA flow increased from 207 ml/min (95% confidence interval (CI) 136-259) to 388 ml/min (95% CI 348-428) (P < 0.001, Mann-Whitney U test) following endarterectomy. Despite this, Vmca did not rise significantly at the end of the procedure. By the first postoperative day Vmca rose to 55.3 cm/s (95% CI 47.6-62.4) (P < 0.025, ANOVA) only to fall preoperative values (46.0 cm/s (95% CI 40.0-52.1)) by 6 weeks. These results suggest that cerebral autoregulation takes time to adapt to the increased flow and pressure following endarterectomy, but has stabilized by 6 weeks.
Ng RL, Gillies TE, Davies AH, et al., 1992, Iliofemoral versus femorofemoral bypass: a 6-year audit., Br J Surg, Vol: 79, Pages: 1011-1013, ISSN: 0007-1323
Iliofemoral and femorofemoral crossover bypass operations performed over a 6-year period were reviewed. A total of 226 patients underwent 231 operations from 1984 to 1990. Seventy-two patients had 75 iliofemoral grafts and 154 patients had 156 femorofemoral grafts. The early mortality rate was 6 per cent for the iliofemoral group and 1.3 per cent for femorofemoral reconstruction. There was a higher reoperation rate in the iliofemoral group (31 versus 16.0 per cent). The cumulative patency rate at 6 years was 75 per cent for iliofemoral bypass and 92 per cent for the femorofemoral procedure (P < 0.01), while the survival rates for the same period were 55 and 74 per cent respectively (P < 0.01). Hospital stay was significantly shorter for patients undergoing femorofemoral bypass (P < 0.05).
Davies AH, Magee TR, 1992, Vein graft stenosis., Br J Hosp Med, Vol: 48, ISSN: 0007-1064
Magee TR, Davies AH, Baird RN, et al., 1992, A head box to protect transcranial Doppler transducers during carotid surgery., Eur J Vasc Surg, Vol: 6, Pages: 563-564, ISSN: 0950-821X
Davies AH, Magee TR, Parry R, et al., 1992, Duplex ultrasonography and pulse-generated run-off in selecting claudicants for femoropopliteal angioplasty., Br J Surg, Vol: 79, Pages: 894-896, ISSN: 0007-1323
Non-invasive assessment of lower limb vasculature may avoid unnecessary angiography in claudicants. Colour duplex ultrasonography of the femoral and popliteal arteries was performed to assess patency and the presence of any stenoses, and pulse-generated run-off (PGR) was used to assess the distal vasculature. In 65 legs colour duplex scanning was successful, compared with angiography, in identifying the site and type of disease in the femoropopliteal segment and 23 lesions were correctly identified as suitable for angioplasty. More patent distal vessels were demonstrated by PGR than by angiography; no vessels patent on angiography were missed by PGR. The estimated cost of diagnostic angiography was 330 pounds per test compared with 52 pounds for non-invasive assessment. By using duplex examination as a screening test, a potential saving of 8062 pounds could have been made in this series. Duplex ultrasonography offers a non-invasive and cost-effective alternative to diagnostic angiography for clinically suspected infrainguinal arterial disease presenting as claudication. PGR was not of clinical value in assessing suitability for angioplasty.
Ng RL, Davies AH, Grace RH, et al., 1992, Subcutaneous rectal stump closure after emergency subtotal colectomy., Br J Surg, Vol: 79, Pages: 701-703, ISSN: 0007-1323
Subtotal colectomy with preservation of the rectum is now the procedure of choice for patients with severe colitis requiring emergency surgery. The use of subcutaneous 'rectal closure' when the retained distal bowel is placed at the caudal end of the abdominal incision in the subcutaneous or fascial layer is studied. An anal catheter may be placed to drain the rectum. Thirty-two patients (14 men, 18 women) of mean age 33 (range 17-77) years with severe inflammatory bowel disease (29 ulcerative colitis, one Crohn's disease, one indeterminate colitis, one Campylobacter colitis) underwent emergency colectomy with subcutaneous rectal stump closure. Twenty-three stumps were closed with staples, four sutured and five by both staples and sutures. Complications developed in seven patients (22 per cent), of which two required surgical intervention. One significant wound infection was treated successfully with a course of antibiotics. Three minor wound infections did not require specific treatment. The rectal stump was always readily located at the time of restorative surgery. This technique is recommended as a simple and safe alternative to an open mucus fistula provided that surgeons adhere to standard surgical principles; in particular the distal bowel should not be brought out into the wound under tension.
Davies AH, Cole SE, Magee TR, et al., 1992, The effect of diabetes mellitus on the outcome of angioplasty for lower limb ischaemia., Diabet Med, Vol: 9, Pages: 480-481, ISSN: 0742-3071
Angioplasty is an important tool in the armamentarium of the clinician dealing with atherosclerotic disease. Diabetic patients with occlusive disease pose special problems. Four hundred and twenty-five lesions were dilated in 370 patients. No difference in site was found when comparing the diabetic and non-diabetic groups (p less than 0.001), but a significant difference in indication for treatment was observed. Cumulative patency at 5 years for iliac lesions in non-diabetic patients was 61.2% and in diabetic patients was 35.6% (p less than 0.05), for superficial femoral and popliteal artery lesions in non-diabetic patients it was 49.7% and in diabetic patients it was 38.8% (NS). The need for subsequent surgical intervention (p less than 0.01) and risk of death (p less than 0.001) are both significantly greater in the diabetic group. This study shows that angioplasty is a technique that can be used with success in diabetic patients and if the indications for interventions are compared, diabetic patients do not worse.
Davies AH, Magee TR, Baird RN, et al., 1992, Praxilene (naftidrofuryl oxalate) as an alternative for the augmentation of femoro-distal bypass blood flow., Eur J Vasc Surg, Vol: 6, Pages: 299-301, ISSN: 0950-821X
In 30 patients undergoing femoro-distal bypass the effect of papaverine and praxilene on blood flow in the graft was measured. The mean resting flow was 129 ml min-1 (range: 91-167) and after papaverine was 202 ml min-1 (142-262) and after praxilene was 205 ml min-1 (143-267). Praxilene has a similar effect to papaverine in the augmentation of blood flow, and further investigation is needed to see if long-term praxilene administration might improve graft survival.
Davies AH, Horrocks M, 1992, Vascular assessment and the ischaemic foot, The Foot, Vol: 2, Pages: 1-6, ISSN: 0958-2592
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Davies AH, Magee TR, Baird RN, et al., 1992, Higher naftidrofluryl dose equivalent to papaverine, European Journal of Vascular Surgery, Vol: 6, Pages: 686-687, ISSN: 0950-821X
Davies AH, Magee TR, Hayward J, et al., 1992, Non-Invasive Methods of Measuring Venous Compliance, Phlebology, Vol: 7, Pages: 78-81, ISSN: 0268-3555
To compare two non-invasive methods of qualitative assessment of the long saphenous vein in terms of venous compliance. Thirty-five long saphenous veins were examined. Compliance measurements have been calculated using: Method A in which an AV Impulse machine (Novamedix, UK) is used to generate a pulse wave in the long saphenous vein and the measurement of transit times are performed. Method B involves duplex ultrasound and venous occlusion of the long saphenous vein. Occlusive pressure measurements are used in both methods. The mean vein compliance ratio measured in 35 long saphenous veins with the different methods was 0.23 (0.18-0.28) and 0.26 (0.22-0.30) using method A and B respectively. (Mean and (95% confidence interval)). The results show that a good correlation r = 0.91 and this was confirmed using methods of agreement. Both techniques give comparable results, however, the method involving Duplex is easier to perform. The research and clinical implications of these techniques remain to be assessed. © 1992, SAGE Publications. All rights reserved.
Davies AH, Pope I, Collin J, et al., 1992, Early reoperation after major vascular surgery: a four-year prospective analysis., Br J Surg, Vol: 79, Pages: 76-78, ISSN: 0007-1323
Between 1 January 1985 and 31 December 1988, 1176 major vascular operations were performed on 1040 patients by the Oxford Regional Vascular Service, of which 136 (12 per cent) were reoperations within 30 days of the initial procedure (110 patients). Sixty-seven (49 per cent) of the reoperations were attempted revascularizations, 43 (32 per cent) were amputations, and surgery for bleeding accounted for 18 (13 per cent). Of the first reoperations 71 (65 per cent) were successful, but among the remaining 39 patients, 17 underwent 26 further reoperations, 15 of which were reoperations for revascularization. The 30-day mortality rate for patients undergoing one reoperation was 13 per cent; this rose to 35 per cent if more than one reoperation was performed. Early reoperation after major vascular surgery is common and carries a high operative mortality. This should be borne in mind when obtaining the informed consent of the patient.
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