Biomedical subjects
Publications and source records attributed to T Buckenham.
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BACKGROUND: Renovascular disease is the most frequently encountered secondary cause of hypertension and is one of the few potentially reversible causes of chronic renal failure. These patients are at increased risk of having cerebrovascular events following operative management for atheromatous renal-artery stenosis. We studied the prevalence of carotid-artery disease in patients with atheromatous renal-artery stenosis. METHODS: A cross-sectional study was carried out on 38 consecutive patients with atheromatous renal-artery stenosis who underwent renal-artery balloon angioplasty. Extracranial carotid atherosclerosis was assessed using a commercially available colour Doppler scanner, depending on the velocity of the peak systolic waveform in the internal carotid artery, and the internal carotid-artery/common carotid-artery ratio. RESULTS: Twenty-one patients (55.3%) had normal or mild carotid-artery disease, 10 (26.3%) had moderate, and 7 (18.4%) had severe carotid-artery disease. Nine patients had previously suffered a stroke (eight infarction, one haemorrhage) and one had multiple transient ischaemic attacks. CONCLUSIONS: Our results suggest that, in patients with atheromatous renal-artery disease severe enough to require angioplasty, 4 out of 10 appear to have moderate to severe carotid-artery disease. This may explain the increased prevalence of atherothrombotic cerebrovascular events in these patients, and also previous observations that, following operative management for atheromatous renal-artery stenosis, some patients had developed an acute or late cerebrovascular event. We suggest therefore that such patients should always be regarded as having generalized vascular disease not confined to one system, and need to be assessed for carotid-artery disease prior to operative management for atheromatous renal-artery stenosis.
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BACKGROUND AND PURPOSE: There has been concern about carotid percutaneous transluminal angioplasty (PTA) carrying a greater risk of cerebral ischemia than carotid endarterectomy. We set out to compare cerebral hemodynamics and microembolization during carotid PTA and CEA. METHODS: We used transcranial Doppler to monitor the middle cerebral artery of 28 patients undergoing carotid PTA (n = 14) or carotid endarterectomy (CEA) with a shunt (n = 14). Each period during which the internal carotid artery was occluded by PTA balloon or by clamp when the shunt was not in place was timed. Individual periods were summated to give a total occlusion time. Ischemic time was defined as the period for which mean middle cerebral artery velocity fell to a third or less of baseline. Microembolic signals were counted during each procedure. RESULTS: CEA resulted in significantly longer individual and total occlusion time than PTA (mean individual occlusion time, seconds), CEA, 168 +/- 51; PTA, 20 +/- 7; P < .001; mean total occlusion time; CEA, 337 +/- 70; PTA, 26 +/- 10; P < .001. Ischemic time was also significantly longer during CEA than during PTA (CEA, 165 +/- 40; PTA, 17 +/- 5; P = .001). There were significantly more microembolic signals during PTA than during CEA (mean number of microembolic signals during CEA, 52 +/- 64; during PTA, 202 +/- 119; P = .001). There was no correlation between any of the parameters measured and periprocedural stroke, which occurred in one patient in each group. CONCLUSION: PTA results in less hemodynamic ischemia but more cerebral microembolism than CEA. In this small series, however, it is not possible to comment on the relations between ischemic time, microembolism, and stroke.
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BACKGROUND AND PURPOSE: Carotid percutaneous transluminal angioplasty ( PTA) may offer an alternative treatment to carotid endarterectomy. However, in contrast to carotid endarterectomy, which has been shown to normalize impaired cerebral hemodynamics, the effects of carotid PTA are unknown. Therefore, we prospectively studied the effect of carotid PTA on both perioperative and postoperative cerebral hemodynamics. METHODS: Eleven patients undergoing carotid PTA for symptomatic carotid artery stenosis were prospectively studied. Transcranial Doppler recordings from the ipsilateral middle cerebral artery (MCA) were performed during the procedure. In addition, MCA blood flow velocity and CO2 reactivity were determined before PTA and at 2 days, 1 month, and 6 months after procedure. The results were compared with those in 11 similar patients undergoing carotid endarterectomy in whom measurements were performed before and 1 month after the operation. RESULTS: During carotid PTA, in 2 of 11 patients during passage of the balloon catheter through the stenosis, MCA blood flow velocity fell transiently. In 6 of 11 patients there was a reduction in flow velocity (>50%) during balloon deflation, but this lasted only a few seconds. After the procedure there was a significant improvement in ipsilateral hypercapnic reactivity: preoperative value, 59.8+/-42.2% (mean+/-SD); 2 days, 77.9+/-31.4%; 1 month, 88.7+/-45.0%; 6 months, 89.8+/-33.9%; and (ANOVA P=.003) preoperative value versus 1 month, P<.02; versus 6 months, P<.02. In all cases in which reactivity was significantly impaired preoperatively, it returned to the normal range. Pulsatility index also increased significantly: preoperative value, 0.827+/-0.251 (mean+/-SD); 2 days, 0.992+/-0.262 (P=.002). Contralateral MCA hypercapnic reactivity also improved after carotid PTA. There was a similar improvement in ipsilateral hypercapnic reactivity after carotid endarterectomy. CONCLUSIONS: Carotid PTA results in a normalization of impaired hemodynamics, as assessed by CO2 reactivity. The degree of improvement is similar to that seen after carotid endarterectomy.
OBJECTIVE: Our aim was to evaluate duplex ultrasound imaging in the identification of renal artery stenosis using a new technique to enhance the recorded Doppler signal. DESIGN: Colour Doppler studies of interlobar renal arteries were performed before and after enhancement using an intravenous contrast of galactose microparticle suspension containing microbubbles (Levovist, Schering) in patients with angiographically confirmed renal artery stenosis. SETTING: Blood Pressure Unit, St. George's Hospital Medical School, and Department of Radiology. The Middlesex Hospital, London, UK. PARTICIPANTS: Twenty-one consecutive hypertensive patients in whom the diagnosis of renal artery stenosis was made on digital subtraction angiography. MAIN OUTCOME MEASURES: The diagnosis of haemodynamically significant renal artery stenosis (> or = 60% on angiography). RESULTS: With Levovist, there was a 20 db increase in the Doppler intensity and, as a result, intrarenal signals were much more clearly delineated and distinct spectral waveforms were obtained from all but one kidney, which was occluded. Significant associations were found between the degree of stenosis (as assessed by angiography) and the following Doppler parameters: diastolic velocity (F = 7.6; P < 0.01), acceleration time (F = 33.5, < 0.0001), peak systolic velocity (F = 37.7, P < 0.0001) and acceleration (F = 60.0; P < 0.0001). Without enhancement, there were five false-positive and two false-negative examinations (sensitivity 85%; specificity 79%) using the acceleration cut-off value of 3.5 m/s2 to identify haemodynamically significant renal artery stenosis (> or = 60% on angiography). After contrast enhancement, there were only three false-positive and one false-negative examinations (sensitivity 94% and specificity of 88%) using the acceleration cut-off value of 3.75 m/s2 and the examination time was reduced by approximately half (sensitivity and specificity of 90% using the acceleration cut-off value of 3.5 m/s2). CONCLUSIONS: Our results suggest that renal duplex scanning using contrast enhancement is a promising new non-invasive technique in screening patients with suspected renal artery stenosis. Contrast enhancement produces more reproducible spectral waveforms, improves accuracy and halves the examination time.
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OBJECTIVE: To study the prevalence, severity, vascular risk factors, and clinical implications of renal artery stenosis in patients with peripheral vascular disease. DESIGN: Cross-sectional study of consecutive patients who were electively referred from the department of vascular surgery for lower limb digital subtraction angiography. SETTING: St. George's Hospital, London, United Kingdom. SUBJECTS: One hundred twenty-seven patients presenting with intermittent claudication or lower limb ischemic ulceration. MAIN OUTCOME MEASURES: Prevalence and clinical importance of renal artery stenosis in patients with peripheral vascular disease adjusted for the confounding effects of age and hypertension. RESULTS: Of the 127 patients, 57 (44.9%) had renal artery disease, of whom 22 (17.3%) had mild disease, 20 (15.7%) had severe disease, and 15 (11.8%) had bilateral renal artery stenosis. There was a significant positive relationship between the presence of renal artery stenosis and the severity of peripheral vascular disease (p = 0.00015). The risk of having renal artery stenosis was nearly four times greater in those with three to four vessels affected and nearly seven times greater in those with five or more vessels affected as compared with those with a milder degree of peripheral vascular disease (one or two vessels affected). This association persisted when the confounding effect of age and hypertension was accounted for. Six patients (31.6%) with renal artery stenosis who underwent revascularization for peripheral vascular disease died during the early postoperative period of cardiac or renal complications. None of the patients with normal renal arteries who had similar surgery developed postoperative complications (p = 0.005). CONCLUSIONS: Renal artery stenosis is a common independent feature in patients with peripheral vascular disease, and its prevalence increases with the increasing severity of the peripheral vascular disease. The postoperative risk following revascularization for peripheral vascular disease appears to be greater in those patients with renal artery stenosis. All patients studied with digital subtraction angiography for peripheral vascular disease should have an aortic flush performed to image the renal arteries. This information may be used to identify those patients likely to develop postoperative complications during peripheral revascularization.
1. Platelet volume was measured in citrated blood in two groups of patients at risk of having atherosclerotic renal artery stenosis, namely (i) 30 patients with severe hypertension, and (ii) 44 patients with peripheral vascular disease. 2. Platelet volume was increased in patients with hypertension who had atherosclerotic renal artery stenosis diagnosed by angiography: no renal artery stenosis, median 7.2 (interquartile range 0.5) x 10(-15)/l; renal artery stenosis 7.8 (0.8) x 10(-15)/l; platelet mass also increased with increasing severity of renal artery stenosis. Platelet volume correlated with severity of renal artery stenosis (rs = 0.391, 2p = 0.033, n = 30). Similarly, platelet volume correlated with severity of renal artery stenosis in patients with peripheral vascular disease (rs = 0.319, 2p = 0.035, n = 44). Serum immunoreactive platelet-derived growth factor (predominantly released from platelets) and plasma immunoreactive interleukin-6 (a cytokine which has been postulated to regulate platelet volume) concentrations were not different between hypertensive patients with and without renal artery stenosis. 3. Since large platelets are hyperactive, increased platelet volume may contribute to the development of atherosclerotic renal artery stenosis. However, the present data do not lend support to the hypothesis that platelet-derived growth factor is central to renal artery atherogenesis. Interleukin-6 does not appear to regulate platelet volume.
BACKGROUND AND PURPOSE: Carotid angioplasty may offer an effective treatment for carotid stenosis, but there has been concern about the incidence and clinical consequences of distal embolization. Transcranial Doppler monitoring in carotid endarterectomy has demonstrated embolic signals during this procedure. We used this technique in patients undergoing carotid angioplasty. METHODS: Transcranial Doppler ultrasound was used to monitor for embolic signals in the ipsilateral middle cerebral artery before and during 10 technically successful carotid angioplasties and at various standardized times in the following month. RESULTS: In the month before angioplasty asymptomatic embolic signals were detected in 3 of 10 patients. During angioplasty multiple embolic signals were detected immediately after balloon inflation in 9 of 10 subjects. A minor ipsilateral cerebral ischemic event occurred in 1 of these 9, but the other 8 were asymptomatic. Embolic signals were common immediately after the procedure and intra-arterial femoral catheter removal (8 of 10 subjects) but thereafter became less frequent and were present in 1 of 5 at 4 hours, 2 of 10 at 48 hours, 1 of 6 at 7 days, and 1 of 10 at 1 month. CONCLUSIONS: Embolization at the time of carotid angioplasty is very common but usually asymptomatic; monitoring by means of Doppler ultrasound will allow the effectiveness of measures to reduce this embolization to be studied. Late embolization occurs in a minority of patients and may account for the small but significant risk of delayed stroke. Doppler monitoring may allow identification of patients at risk and assessment of the effectiveness of prophylactic therapy.
Traumatic rupture of the thoracic aorta is a justifiably feared condition. Some authors have proposed the use of computed tomography as a non-invasive means of diagnosis. We report two cases where computed tomographic scans were misinterpreted, leading to erroneous diagnoses and inappropriate referrals. The pitfalls of using a cross-sectional imaging technique to diagnose a transverse lesion and the relative ease and accuracy of aortography are discussed.
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Cerebral angiography is associated with a risk of neurological complications and air embolism may contribute towards this risk. To test this hypothesis, transcranial doppler ultrasonography was used to monitor the presence of air emboli in the middle cerebral arteries of 7 patients undergoing cerebral angiography. Doppler signals consistent with numerous air emboli were noted during each injection of radiographic contrast. This phenomenon was studied further in sheep. Radiographic contrast medium was injected into the carotid artery while a major carotid branch was insonated transorbitally. Embolic signals similar to those seen in patients were noted. Air was introduced at two points. First, at the time of drawing up the contrast into the syringe, especially with more viscous media. Standing the media before injection resulted in a highly significant reduction of air embolism, reducing the total mean duration of emboli from 1.32 (SD 0.60) s after immediate injection to 0.04 (0.05) s after ten minutes standing for iohexol 340 mg/mL (p < 0.001). Second, air was introduced at the time of injection, possibly by the formation of cavitation bubbles under pressure. This occurred most prominently with the less viscous contrast media and with saline, and was significantly reduced by slow injection (mean duration of emboli for saline 2.85 [2.43] s with fast injection compared with 0.32 [0.37] s with slow injection, p = 0.004). Air embolism may contribute towards neurological dysfunction after angiography. Measures should be taken to reduce this by allowing contrast media to stand prior to injection, and by flushing catheters with saline injected slowly.
We report two cases of iliofemoral occlusive vascular disease which were successfully treated by angioplasty via the popliteal artery. The merits of this approach, when ipsilateral femoral puncture is precluded, are discussed.
We review our results in treating 5 patients with parotid duct pathology (3 stenoses, 2 calculi), using digital subtraction imaging for sialography, and standard interventional techniques using balloon catheters. Good technical results were achieved in all 5 patients. We describe our techniques and how they were modified to overcome various difficulties.