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Biomedical subjects

A R Naylor

Publications and source records attributed to A R Naylor.

At least 127 records · Page 7Linked to original sources
PubMed1996

Can lower limb vascular reconstruction be based on colour Duplex imaging alone?

OBJECTIVES: To determine the safety and efficacy of Duplex scanning as the only imaging modality prior to lower limb vascular reconstruction. DESIGN: Retrospective review. SETTING: A single university vascular unit. PATIENTS AND METHODS: Review of all lower limb vascular reconstructions over a 2 year period. RESULTS: Eighty-five limbs underwent vascular reconstruction based on colour Duplex alone. A wide range of revascularising operations were performed, including 29 cases of infragenicular reconstruction. In the latter cases, the findings of Duplex scanning were confirmed by on table pre-reconstruction angiography in 28 cases and the graft occlusion rate in the first month was 14%. There were no postoperative complications that could be attributed to a failure of preoperative Duplex imaging. CONCLUSION: Vascular reconstruction can be undertaken safely in patients with lower limb arterial disease on the basis of Duplex scanning alone.

Adult↗
PubMed1996

A comparison of quality control methods applied to carotid endarterectomy.

OBJECTIVES: To compare the ability of continuous wave Doppler (CWD), B-mode ultrasound (BMU), angioscopy and transcranial Doppler (TCD) to detect technical error during carotid endarterectomy (CEA). DESIGN: A prospective, comparative study in 100 consecutive patients. SETTING: Leicester Royal Infirmary, Leicester, U.K. MATERIALS: Intraoperative TCD monitoring was performed using a SciMed PcDop 842 2 MHz TCD. An Olympus 2.8mm flexible angioscope was used to inspect the arterial lumen prior to restoration of bloodflow. After restoration of flow 10Mhz BMU images and 8Mhz CWD velocity spectra of carotid artery blood flow were obtained. CHIEF OUTCOME MEASURES: The detection of intimal flaps, thrombus, stenoses or other errors of surgical technique likely to result in perioperative morbidity. MAIN RESULTS: CWD and BMU images were technically inadequate in 9% and 24% of cases respectively and neither technique altered clinical management. Angioscopy demonstrated significant technical errors in 12 cases (four intimal flaps, thrombus in eight). TCD detected shunt malfunction in 13% of patients, emboli during dissection in 23% and early postoperative carotid artery thrombosis in three patients. CONCLUSIONS: A combination of TCD monitoring and completion angioscopy provided the maximum yield in terms of diagnosing technical error and establishing the cause of perioperative morbidity.

Angioscopy↗
PubMed1996

Unstable carotid plaques: preoperative identification and association with intraoperative embolisation detected by transcranial Doppler.

OBJECTIVES: To investigate whether unstable carotid plaque characteristics, as determined by preoperative colour Duplex ultrasonography (CDU) and postoperative histological examination, were associated with particulate embolisation, detected by transcranial Doppler (TCD), during the initial dissection of the carotid bifurcation during carotid endarterectomy(CEA). DESIGN: A prospective, consecutive study was undertaken of 50 patients undergoing carotid endarterectomy(CEA). SETTING: Leicester Royal Infirmary, Leicester, U.K. MATERIALS: Carotid plaques were assessed preoperatively using CDU. Intraoperative TCD monitoring of the ipsilateral middle cerebral artery was performed using a Scimed 2MHz TCD. Carotid plaques removed at operation were processed histologically and multiple sections assessed microscopically. CHIEF OUTCOME MEASURES: Plaque composition was classified ultrasonically and histologically according to the Gray-Weale classification and plaque surface characteristics were graded according to a five point classification. TCD detected emboli were identified and counted during the initial dissection of the artery. MAIN RESULTS: Particulate embolisation occurred in nine patients. Histologically, embolisation was associated with ulcerated plaque in three cases and ulcerated plaque with associated thrombus in six cases (p = 0.0005). However, the ability of CDU to positively predict embolisation based on the correct identification of an unstable plaque surface was only 25%. CONCLUSIONS: Embolisation during dissection is strongly associated with ulcerated plaque with associated thrombus. CDU is unable to reliably identify these characteristics preoperatively. Intraoperative TCD monitoring can detect potentially harmful embolisation during this stage enabling surgical technique to be modified appropriately.

Arteriosclerosis↗
PubMed1996

The effect of a surveillance programme on the patency of synthetic infrainguinal bypass grafts.

OBJECTIVES: Vein graft surveillance is widely acknowledged to be of benefit in improving graft patency at least in the first year after arterial bypass surgery. The aim of this study was to examine the effect of a surveillance programme on the patency of synthetic infrainguinal bypass grafts. DESIGN: A prospective study of 69 consecutive prosthetic bypass grafts was undertaken over a 3 year period. METHODS: Patients were seen at 3 monthly intervals after surgery and underwent measurement of ankle brachial pressure indices and a colour Duplex scan of the graft. RESULTS: The surveillance programme was able to detect treatable lesions in five grafts and in the run-off vessels of two other grafts prior to occlusion. However 14 grafts failed after the first 30 days, 12 of which were not predicted by the surveillance programme. CONCLUSIONS: Surveillance appears to be of limited benefit in the maintenance of patency of synthetic infrainguinal bypass grafts.

Aged↗
PubMed1996

Quality control during carotid endarterectomy.

Although some form of quality control assessment is standard practice following virtually all forms of peripheral vascular reconstruction, it is seldom applied to carotid endarterectomy. This is despite the fact that the complications following endarterectomy can be catastrophic, are often related to technical error and are not easily remedied. A number of novel quality control techniques are now available. This review article summarizes the application of these methods to ensuring optimal surgical practice in patients undergoing carotid endarterectomy.

Angioscopy↗
PubMed1995

Fate of the non-operated carotid artery after contralateral endarterectomy.

The long-term fate of the non-operated internal carotid artery (ICA) in 219 patients undergoing contralateral carotid endarterectomy was studied; 151 patients underwent serial postoperative imaging of the vessel. Cumulative freedom from stroke in the non-operated hemisphere was 99, 96 and 86 per cent at 1, 5 and 10 years respectively, giving a mean incidence of stroke of 1 per cent per annum. Only one stroke was preceded by a transient ischaemic attack and no stroke was associated with severe (70 per cent or greater) stenosis of the ICA. Ten patients (7 per cent) with initially mild or moderate disease of the non-operated ICA progressed to severe stenosis during follow-up, but only three became symptomatic and, in each case, the onset of symptoms preceded recognition of disease progression. The long-term risk of stroke in the non-operated ICA territory is very small. Of practical importance is that none of the observed strokes could have been prevented by postoperative surveillance of this type.

Carotid Artery Diseases↗
PubMed1995

Measurement of blood flow velocity in the basal cerebral circulation: advantages of transcranial color-coded sonography over conventional transcranial Doppler.

Unlike conventional transcranial Doppler (TCD), transcranial color-coded sonography (TCCS) enables imaging of the basal cerebral arteries using color-flow ultrasonography and correction for the angle of insonation when determining blood flow velocities. We present hemodynamic data from 20 normal subjects, each studied with TCD and TCCS. Velocities derived using TCCS with angle correction were significantly greater than those derived using TCD in all vessels (mean velocities [cm/sec; mean with 95% confidence intervals)--anterior cerebral artery: TCD 48 (45-50), TCCS 62 (58-66), p < .0001; middle cerebral artery: TCD 61 (58-64), TCCS 70 (66-74), p < .0001; posterior cerebral artery: TCD 43 (41-46), TCCS 54 (50-57), p < .0001; basilar artery: TCD 40 (34-45), TCCS 45 (38-52), p < .01. Pulsatility index values were significantly greater in all arteries when determined by TCCS, and resistance index values were significantly greater except in the basilar artery. Correcting for the angle of insonation using TCCS may enable estimation of blood flow velocities closer to the "true" values than those derived using conventional TCD.

Adult↗
PubMed1995

The additional value of intraoperative angiography in infragenicular reconstruction.

OBJECTIVE: To evaluate the ability of preoperative intraarterial digital subtraction angiography (IADSA) to predict the feasibility of infragenicular reconstruction and site of the distal anastomosis. DESIGN: Prospective study. SETTING: University Hospital MATERIALS: 45 patients with 50 ischaemic limbs, considered potential candidates for infragenicular reconstruction. CHIEF OUTCOME MEASURES: Pre-reconstruction intraoperative angiography (IOA) was used as the gold standard. Analysis of angiograms was performed blindly and independently by a single observer. In patients who ultimately underwent primary amputation, exploration and attempted angiography of the crural and ankle vessels was performed to verify the IADSA findings. MAIN RESULTS: There was 87% accuracy (kappa = 0.66) between IADSA and IOA in differentiating between a normal, stenosed and occluded tibial artery and there was 86% accuracy (kappa = 0.67) in determining the adequacy of run-off into the pedal arch. IADSA had a positive predictive value of 100% to determine the feasibility of reconstruction but a negative predictive value of only 73%. After excluding those patients tha IADSA deemed non-reconstructable, IADSA had a positive predictive value of 97% to determine the correct artery and 92% to determine the correct segment of artery for distal anastomosis. CONCLUSIONS: IADSA could not determine when reconstruction was not possible, but in those deemed reconstructable by IADSA, the surgeon can confidently expose the appropriate artery at the appropriate level knowing the pedal run-off status in 86% of patients. IADSA should not be used to exclude reconstruction (i.e. pre-reconstruction IOA is still required in these patients) but for the remainder, IADSA can be used to plan surgical strategy without recourse to IOA.

Amputation, Surgical↗
PubMed1995

Infrapopliteal percutaneous transluminal angioplasty: a safe and successful procedure.

AIM: To review outcome of 40 consecutive infrapopliteal percutaneous transluminal angioplasty (PTA) procedures performed over a 65 month period. CHIEF OUTCOME MEASURES: The indication for PTA was intermittent claudication in 20 (50%) cases and rest pain, ulceration or gangrene in the remainder. RESULTS: There was one technical failure; the remaining 39 limbs were all clinically improved by 24 h and this improvement was maintained at 3 months in 36 (90%). There were no deaths nor limb loss related to PTA and 2 embolic complications were successfully treated percutaneously. The primary and secondary symptomatic patencies at 24 months were 59 and 79% respectively. The actuarial limb salvage rate at 1 year for the 20 limbs presenting with critical ischaemia was 77%, and 10 of the 14 procedures performed for ulceration or gangrene resulted in healing with only minor surgical intervention. CONCLUSIONS: With modern endovascular techniques, infrapopliteal PTA is a safe, worthwhile and durable procedure.

Aged↗
PubMed1995

Color-coded ultrasound diagnosis of vascular occlusion in acute ischemic stroke.

A combination of extracranial and transcranial color-coded sonography was used to identify the patterns of vascular occlusion in 47 patients with acute ischemic stroke. Total anterior circulation infarction (n = 20) was associated with internal carotid artery (ICA) or middle cerebral artery (MCA) occlusion (n = 8 and 9, respectively), or with significant reduction in ipsilateral MCA velocities (n = 5). Patients with partial anterior circulation (n = 22) infarction had patency of the ipsilateral ICA and MCA. In this group, significant reduction of ipsilateral MCA velocities (n = 7) was associated with more extensive infarcts on conventional neuroimaging (n = 6), suggesting multiple MCA branch occlusions. Ultrasound imaging was unable to identify underlying vascular pathology in patients with posterior circulation infarction or with lacunar infarction (n = 5). An ultrasound-based approach enables noninvasive identification of major vascular pathology of the anterior cerebral circulation in patients with acute cerebral infarction. It may be useful for the rapid identification of patients most and those least likely to benefit from acute intervention, and for monitoring their response.

Acute Disease↗
PubMed1995

Assessment of intracranial primary collaterals using transcranial color-coded real-time sonography.

Transcranial color-coded sonography (TCCS) was used to assess primary willisian collaterals in 100 patients with extracranial internal carotid artery (ICA) stenosis. Their importance was determined during carotid endarterectomy (CEA) by transcranial Doppler measurement of blood flow velocity in the ipsilateral middle cerebral artery (MCAV) before and after carotid clamping. All patients had unilateral ICA disease of at least 60% stenosis. Twenty-nine ICAs (14.5%) were occluded, 70 vessels (35%) were stenosed by 80 to 99%, 43 vessels (21.5%) were stenosed by 60 to 79%, and 53 ICAs had stenosis of less than 60%. Temporal hyperostosis precluded TCCS in 15 patients (15%). Anterior cerebral/communicating artery collaterals were detected in 40 patients (49%) and posterior cerebral/communicating artery collaterals were detected in 22 patients (27%). No patients with ICA stenosis of less than 80% had established collateral pathways. Patients with willisian collaterals showed higher postclamp MCAVs as a proportion of the preclamp value during CEA (72% [62-81]; median with 95% confidence interval) than did those without primary collaterals (46% [34-58], p = 0.02). TCCS allows noninvasive assessment of intracranial primary collaterals whose functional importance is recognized during abrupt hemodynamic challenge. It may determine which patients are at greatest risk of ischemia during cerebral revascularization.

Aged↗
PubMed1995

Interpretation of embolic phenomena during carotid endarterectomy.

BACKGROUND AND PURPOSE: Air and particulate emboli are a major source of morbidity during carotid endarterectomy (CEA); however, amplitude overload and poor time resolution have restricted the ability of transcranial Doppler ultrasound to differentiate between the two. METHODS: We have now overcome these two limitations by (1) rerouting embolic signals away from the audio frequency amplifier to avoid amplitude overload and (2) substituting the Wigner distribution function for the fast Fourier transform to improve time and frequency resolution. Thus, we can now accurately determine embolic duration and embolic velocity, the product of which is the sample volume length (SVL). This measurement represents the physical distance over which an embolic signal can be detected. The underlying hypothesis was that air reflected more ultrasound and would therefore be detected over a greater SVL. RESULTS: The median SVL (interquartile range) for 75 in vitro air emboli was 1.97 cm (range, 1.70 to 2.35) compared with 0.27 cm (range, 0.16 to 0.43) for 185 particulate emboli detected during the dissection phase of CEA. Off-line analysis on an additional 560 embolic signals detected during different phases of CEA suggested that 46 of 143 (32%) of emboli immediately after shunt insertion were particulate, as were 19 of 33 (58%) occurring during shunting, 28 of 78 (36%) after restoration of flow in the external carotid artery, 23 of 251 (9%) after restoration of flow in the internal carotid artery, and 55 of 55 (100%) of those emboli detected during the early recovery phase. CONCLUSIONS: This development provides objective physical criteria upon which embolus characterization (particulate/air) can be based. This could have major implications for future patient monitoring with respect to modification of surgical technique and pharmacological intervention.

Embolism, Air↗
PubMed1994

Role of completion angioscopy in detecting technical error after carotid endarterectomy.

Completion fibreoptic angioscopy was performed in 30 consecutive patients after carotid endarterectomy. The aim was to evaluate the potential role of angioscopy as a quality-control technique. Major abnormalities (two initial flaps, two large thrombi) were identified in four patients and minor adherent thrombus was encountered in five. All abnormalities were corrected before restoration of flow. This preliminary experience suggests that completion angioscopy merits further study as a method for the intraoperative detection of potentially harmful lesions after carotid endarterectomy.

Angioscopy↗
PubMed1994

Prevalence of impaired cerebrovascular reserve in patients with symptomatic carotid artery disease.

Cerebrovascular reserve (CVR) was studied in 104 consecutive patients with symptomatic carotid territory disease and ipsilateral internal carotid artery stenosis. Overall, 30 of 104 patients (29 per cent) had impaired CVR. The frequency of CVR impairment increased with the severity of internal carotid artery stenosis: impairment was present in none of 11 patients with stenosis of less than 50 per cent, four of 24 with stenosis of 50-69 per cent, 14 of 41 with stenosis of 70-89 per cent and 12 of 28 with stenosis of 90-99 per cent. Patients presenting with a stroke were significantly more likely to have impaired CVR than those with transient ischaemic attacks and/or amaurosis fugax (odds ratio 3.7 (95 per cent confidence interval (c.i.) 1.5-9.0)), as were those with a residual neurological deficit (odds ratio 4.3 (95 per cent c.i. 1.6-11.5)) and evidence of infarction from computed tomography (odds ratio 3.8 (95 per cent c.i. 1.6-9.4)).

Adult↗