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Biomedical subjects

A R Naylor

Publications and source records attributed to A R Naylor.

At least 145 records · Page 8Linked to original sources
PubMed1994

Extracranial carotid artery flow measurement during carotid endarterectomy using a Doppler ultrasonographic flowmeter.

A study was performed to evaluate immediate changes in carotid artery blood flow after carotid endarterectomy using a Doppler ultrasonographic flowmeter. Forty-seven consecutive patients aged 49-78 (median 64) years with symptomatic internal carotid artery (ICA) stenosis underwent carotid endarterectomy. Volume flow, resistance and pulsatility index were measured in the common carotid artery (CCA) and ICA both before and after operation. ICA flow increased by 54 per cent (P < 0.01) and resistance decreased by 58 per cent (P = 0.01). CCA flow rose by 17 per cent (P = 0.1) and resistance fell by 21 per cent (P = 0.02). The pulsatility index did not change significantly. The Doppler ultrasonographic flowmeter offers a simple, non-invasive and convenient means of improving understanding of the immediate haemodynamic effects of carotid endarterectomy. It is useful in everyday practice to confirm the adequacy of endarterectomy, particularly in the absence of other methods of quality control. Duplex ultrasonography might still be necessary after surgery if the flowmeter does not demonstrate an increase in flow compared with the preoperative value.

Aged↗
PubMed1994

Diagnosis of intracranial occlusive disease before carotid endarterectomy: preliminary experience with transcranial colour-flow Doppler ultrasonography.

Transcranial colour-coded Doppler ultrasonography allows both imaging and simultaneous haemodynamic investigation of the basal cerebral arteries. Four of 16 patients undergoing carotid endarterectomy were found to have intracerebral artery stenotic disease by use of this technique. Discrete stenotic segments were recognized by their markedly raised blood flow velocities with damping of the spectral Doppler waveform distally. Colour-coded transcranial Doppler ultrasonography used in conjunction with extracranial duplex imaging might provide an effective and safe alternative to angiography.

Aged↗
PubMed1994

Clinical relevance of intraoperative embolization detected by transcranial Doppler ultrasonography during carotid endarterectomy: a prospective study of 100 patients.

A study was performed to investigate the clinical significance of microembolization detected by transcranial Doppler ultrasonography (TCD) by determining the quantity and character of emboli and correlating these with neurological and psychometric outcome, fundoscopy, automated visual field testing and computed tomographic brain scans in 100 consecutive patients undergoing carotid endarterectomy. Embolization was detected in 92 per cent of successfully monitored operations. Most emboli were characteristic of air and not associated with adverse clinical outcome. However, more than ten particulate emboli during initial carotid dissection correlated with a significant deterioration in postoperative cognitive function. A relationship between persistent particulate embolization in the immediate postoperative period, and both incipient carotid artery thrombosis and the development of major neurological deficits was observed. Immediate intervention, based on TCD evidence of embolization, has the potential to avert neurological deficits resulting from particulate embolization.

Aged↗
PubMed1994

Intracranial aneurysms and arteriovenous malformations: transcranial colour-coded sonography as a diagnostic aid.

Transcranial colour-coded sonography (TCCS) is a new development in noninvasive cerebral vascular imaging. We studied 5 patients with known intracranial aneurysms and 12 patients with arteriovenous malformations (AVM). We were unable to image any of the aneurysms (all 5 mm or less in diameter) using colour flow ultrasound. Similarly, pulsed wave Doppler interrogation failed to reveal any flow disturbances. Nine out of 12 AVMs were successfully visualised as serpiginous structures and the principal feeder vessels were identified in 11 cases. Blood flow velocities in the feeder vessels were elevated compared with the same vessel contralaterally (median [cm/s]; peak systolic 227 vs. 89, P = 0.001; mean 178 vs. 57, P = 0.001; end diastolic 138 vs. 37, P < 0.0005). Pulsatility indices (PI) and resistance indices (RI) in the feeder vessels were reduced relative to the same vessel contralaterally (median PI 0.46 vs. 0.94, P < 0.0005; median RI 0.37 vs. 0.59, P < 0.0005). At present, TCCS appears of little value in the diagnosis of intracranial aneurysms, but it shows promise for the imaging of AVMs and their haemodynamic study.

Adolescent↗
PubMed1994

On-table diagnosis of incipient carotid artery thrombosis during carotid endarterectomy by transcranial Doppler scanning.

We present a case where transcranial Doppler ultrasound monitoring of a carotid endarterectomy enabled us to detect the incipient thrombosis of the operated artery before reversal of anesthesia. The use of transcranial Doppler ultrasound monitoring in carotid endarterectomy has the potential to detect this complication before serious neurologic damage has occurred and therefore reduce the morbidity and mortality rates associated with the operation.

Aged↗
PubMed1994

Subintimal angioplasty of femoropopliteal artery occlusions: the long-term results.

The technique of subintimal angioplasty has been attempted on 200 consecutive femoropopliteal artery occlusions of median (range) length 11 (2-37) cm. The principle of the technique is to traverse the occlusion in the subintimal plane and recanalise by inflating the angioplasty balloon within the subintimal space. The technical success rate was 159/200 (80%) and was not significantly different for occlusions < 10 cm (81%, n = 73), 11-20 cm (83%, n = 63) or > 20 cm (68%, n = 23), p = 0.20. There were no deaths nor limb loss resulting from the procedure. The median (range) ankle-brachial pressure index increased from 0.61 (0.21-1.0) preangioplasty to 0.90 (0.26-1.50) postangioplasty. The actuarial haemodynamic patencies of technically successful procedures at 12 and 36 months were 71% and 58% respectively, the symptomatic patencies were 73% and 61%. A multiple regression analysis showed that smoking multiplied the risk of reocclusion by 2.70 (p < 0.001), each additional run-off vessel reduced the risk by 0.54 (p < 0.001) and the risk increased by 1.73 (p = 0.020) for every 10 cm of occlusion length. In conclusion, the technical success rate (80%) of subintimal angioplasty for femoropopliteal occlusions is unrelated to occlusion length and for all procedures, including technical failures, cumulative symptomatic and haemodynamic patencies of 46 and 48% can be achieved at 3 years. The factors influencing long-term patency were smoking, the number of calf run-off vessels and occlusion length.

Aged↗
PubMed1994

Transcranial color-coded sonography of the basal cerebral circulation. Reference data from 115 volunteers.

BACKGROUND AND PURPOSE: Transcranial color-coded sonography is a new development in noninvasive cerebral vascular imaging. Reference data using this technique are described. METHODS: Blood velocities and pulsatility and resistance indices were determined in the anterior cerebral, middle cerebral, posterior cerebral, vertebral, and basilar arteries in 115 volunteers after correction for the angle of insonation. RESULTS: Of 1265 basal arterial segments, 1053 were insonated (83%). The vertebral (98%), basilar (92%), middle cerebral (84%), and posterior (P1) cerebral arteries (84%) were the most successfully insonated, with the anterior (73%) and posterior (P2) cerebral arteries (72%) the least successfully insonated. Mean and end-diastolic blood velocities decreased significantly with age in all vessels (middle cerebral artery mean velocity: 20 to 39 years, 74 cm/s [71-76]; > 60 years, 58 cm/s [55-61], P < .0001; mean with 95% confidence intervals), and peak systolic velocity decreased significantly except in the posterior (P2) cerebral artery. Blood velocities were higher in women except in the > 60-year group. Velocities showed the least interhemispheric asymmetry in the middle cerebral artery (r = .85 and r = .83, peak and mean velocities, respectively) and the greatest asymmetry in the posterior (P2) cerebral artery (r = .58 and r = .59, peak and mean velocities, respectively). Pulsatility and resistance indices increased significantly with age in all vessels (middle cerebral artery pulsatility index: 20 to 39 years, 0.84 [0.82-0.87], > 60 years, 0.97 [0.93-1.02], P < .0001; middle cerebral artery resistance index: 20 to 39 years, 0.55 [0.54-0.56], > 60 years, 0.62 [0.60-0.64], P < .0001). CONCLUSIONS: Transcranial color-coded sonography can image the basal cerebral arteries and distinguish vertebral from basilar artery flow and enables pulsed Doppler interrogation with correction for the angle of insonation.

Adult↗
PubMed1993

Interventional radiology in the maintenance of infrainguinal vein graft patency.

The impact of interventional radiology on the cumulative patency rate of 112 consecutive infrainguinal vein grafts was reviewed. The primary, primary assisted and secondary cumulative patency rates at 42 months were 40, 65 and 69 per cent respectively. The difference between primary and primary assisted patency rates (40 versus 65 per cent, P = 0.001) resulted from the early detection and treatment of stenoses in 30 grafts by percutaneous transluminal angioplasty (PTA). Interventional radiology also improved the cumulative graft patency rate through PTA of one inflow and five outflow arteries, thrombolysis of two graft occlusions, embolization of two persistent arteriovenous fistulas and salvage of one graft on the first day after operation by percutaneous aspiration of distal graft thrombus. Interventional radiology has a crucial role to play in the maintenance of infrainguinal vein graft patency; provided that graft stenoses are detected early in their development by aggressive graft surveillance, PTA is a highly effective treatment.

Adult↗
PubMed1993

Serial imaging of the carotid bifurcation and cerebrovascular reserve after carotid endarterectomy.

A radioisotopic method of quantifying mean cerebral transit time was used to assess the immediate effects of carotid endarterectomy on cerebrovascular reserve (CVR) in 69 patients. In addition, serial postoperative data were acquired on CVR, clinical status and non-invasive imaging of the internal carotid arteries in 56 patients over a period of 6-48 (median 24) months. Twenty-one patients (30 per cent) had preoperative evidence of impaired CVR in the symptomatic hemisphere. Within 4 days of surgery, however, reserve had returned to normal in 17 of the 21 patients. During follow-up, four of the 56 patients developed recurrent stenosis (> 50 per cent) or occlusion of the artery operated on but only two of these had impairment of CVR and none was symptomatic. Three patients suffered recurrent transient ischaemic attacks (TIAs) but none had recurrent internal carotid artery disease or impaired CVR. One patient suffered a TIA in the territory of the non-operated artery during follow-up in association with disease progression and CVR impairment. However, the TIA preceded recognition of either of these changes. Twelve other patients had (or developed) stenosis (> 50 per cent) in the non-operated artery during follow-up but none was symptomatic or developed impairment of CVR. Although assessment of CVR provided useful information on the frequency of haemodynamic compromise before carotid endarterectomy and on the natural history of disease progression, neither serial assessment of reserve nor non-invasive imaging of the carotid bifurcation influenced clinical practice during follow-up.

Blood Flow Velocity↗
PubMed1993

Factors influencing the hyperaemic response after carotid endarterectomy.

Transcranial Doppler ultrasonography was used to evaluate serially the changes in middle cerebral artery blood flow velocity (MCAV) in 37 consecutive patients during the first 72 h after carotid endarterectomy to identify factors that may predispose towards postoperative hyperaemia. Within 6 h of endarterectomy, median MCAV in the operated hemisphere was 48 per cent (95 per cent confidence interval 37-60 per cent) above that on admission and remained 27 per cent (95 per cent confidence interval 19-37 per cent) higher at 72 h. There was a similar, but less marked, increase in MCAV in the contralateral middle cerebral artery during the same time period. There was no association between the postoperative increase in MCAV and clinical presentation, admission MCAV, the presence or absence of a residual neurological deficit or infarction on computed tomography before operation, carotid clamp time, shunt usage, internal carotid artery stump pressure or MCAV during clamping. The greatest increase in MCAV was observed in patients with internal carotid artery stenosis > or = 50 per cent and, more particularly, in those with preoperative evidence of impaired cerebrovascular reserve. In the latter patients, MCAV was 100 per cent above the admission level within 12 h of operation and was still 50 per cent raised at 72 h.

Blood Flow Velocity↗