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Biomedical subjects

M R Rees

Publications and source records attributed to M R Rees.

At least 37 records · Page 2Linked to original sources
PubMed1993

Balloon angioplasty of totally and subtotally occluded coronary arteries: results using the Hydrophillic Terumo Radifocus Guidewire M (glidewire)

Balloon angioplasty was attempted, using hydrophillic Terumo guidewires, in 52 totally and subtotally occluded coronary arteries (50 patients), in which recanalisation by conventional angioplasty guidewires had failed. Hydrophillic guidewires had a crossing success rate of 65.4% (34/52); there was subsequently a technical success rate of 56% (29/52) and clinical success of 39% (20/52). Dissection of the coronary artery was seen in 16/29 technically successful cases. In 12/16 arteries, dissection was small and localised, whereas in 4/16 large and extended distally. There was one myocardial infarction and no peri-procedural deaths. Eleven out of 29 technically successful cases continued to be regarded as successful 12 mo postangioplasty. We conclude that the hydrophillic Terumo guidewire can improve the success rate in angioplasty of totally and subtotally occluded coronary arteries when conventional wires have failed.

Adult↗
PubMed1993

A comparison of methods for estimating left ventricular volumes from radionuclide ventriculography.

An accurate reproducible measurement of left ventricular volume is important in the evaluation of cardiac disease. Four methods of left ventricular volume measurement by radionuclide ventriculography have been compared and their reproducibility assessed in a patient group. The methods studied were a geometric method, a method based on count data alone and two methods which require a blood sample and an estimate of ventricular depth. The accuracy of absolute volumes is difficult to determine due to the lack of a 'gold standard'. The method using count data alone was found to give reproducible results. Volumes can be calculated quickly and easily from data acquired in a standard radionuclide ventriculogram. End systolic volumes calculated using this method clearly separated normal and abnormal patient groups.

Aged↗
PubMed1993

Does peripheral angioplasty compromise limb blood flow?

Isotope limb blood flow studies were carried out using balloon, laser and Kensey catheter techniques to assess the outcome of peripheral angioplasty. Limb blood flow and Doppler ankle-brachial pressure measurements were obtained before angioplasty and at 6 months after angioplasty in a total of 101 angioplastied limbs: A fall in limb blood flow at 6 months was seen in 17% of the angioplastied limbs with no significant difference in the figures for the different types of angioplasty. Limb blood flow was also measured in 53 contralateral untreated limbs, approximately half of the patient group having both legs angioplastied. 25% of untreated limbs showed a fall in limb blood flow. Significantly more of the untreated limbs showed a fall in limb blood flow at 6 months where the contralateral, treated limb did not improve as a result of the angioplasty compared with those patients where the angioplastied leg improved. These results suggest that a lack of improvement in blood flow in the angioplastied limb may not result from failure of the angioplasty but may be the result of some factor, or combination of factors, which adversely affects both the angioplastied and the untreated leg in some patients.

Angioplasty↗
PubMed1993

Fast magnetic resonance angiography using turbo-FLASH sequences in advanced aortoiliac disease.

A prospective study using contrast enhanced turbo-FLASH (Fast Low-Angle Shot) magnetic resonance (MR) angiography was performed to assess the arterial anatomy in patients who had advanced atherosclerotic aortoiliac disease. This new imaging sequence was employed in 17 patients and the results were compared with conventional abdominal aortography. MR angiography accurately detected all aortic occlusions (3/3), their sites and their extent. All nine iliac occlusions were correctly identified (sensitivity 100%, specificity of 90%). The sensitivity was 100% for stenosis of 50% or greater in the abdominal aorta, and the iliac and common femoral arteries. The degree of stenosis was overgraded in 20 of 51 lesions (39.2%). Mild stenosis was overgraded as moderate stenosis in 10 and as severe stenosis in three. Moderate stenosis was overgraded as severe stenosis in four. None of the mild or moderate stenoses resulted in areas of signal voids suggestive of occlusions. Three severe stenoses were seen as areas of signal voids (two iliac, one femoral). In the eight patients who had in total 10 aneurysmal dilatations of the aorta or the iliac arteries, MR angiography was superior in demonstrating the true extent of the aneurysms. We conclude that turbo-FLASH MR angiography has the potential to be a useful non-invasive imaging technique for patients with advanced aortoiliac disease.

Aged↗
PubMed1993

Iatrogenic vascular injury following arterial cannulation: the importance of early surgery.

Prospective data were collected over a 7-year period on patients undergoing repair of iatrogenic vascular injury following arterial cannulation. From 9375 procedures (7790 coronary angiograms, 835 coronary angioplasties, 445 other cardiac catheterizations, 155 femoral angiograms, 150 peripheral angioplasties) surgical repair was required in 26 patients. The overall incidence of significant injury was 0.28% and higher in therapeutic than diagnostic procedures. The mode of presentation included: critical limb ischaemia in 18 cases, false aneurysm in three, haematoma in three and claudication in two. The common femoral artery was the most common site of injury. No patient presenting with false aneurysm or haematoma suffered any deleterious sequelae. However, 50% of those presenting with critical ischaemia suffered permanent disability after operation. The median delay to surgery was significantly longer in this group (24 versus 4 h; P < 0.001) but there was no difference in age or incidence of underlying peripheral vascular disease. The physical, psychological and litigious sequelae of the complications of iatrogenic vascular injury cannot be overstated. It is strongly advocated that immediate surgical consultation be applied when limb ischaemia is suspected.

Adolescent↗
PubMed1992

Cardiac resuscitation with percutaneous cardiopulmonary support.

Percutaneous cardiopulmonary support (CPS) was initiated in 9 patients to provide haemodynamic stability after failure of conventional resuscitation. 4 patients were in cardiogenic shock and 4 remained in asystole, with 1 in resistant ventricular fibrillation, after cardiac arrest. During CPS for those in cardiogenic shock, the mean intra-arterial pressures ranged from 65 to 100 mm Hg (mean 84), at flow rates of between 3 to 5 l/min (mean 3.9). 2 patients underwent technically successful coronary angioplasty. No patient in this group survived. In the cardiac arrest group, acceptable mean intra-arterial blood pressures were achieved (mean 95, range 90-100 mm Hg) at flow rates of between 2 to 3 l/min (mean 2.6). All 5 subjects underwent technically successful coronary angioplasty whilst on CPS. 4 survived. 2 were alive and well at 12 months follow-up, 1 of whom had returned to work; the third is alive and well at 4 months.

Aged↗
PubMed1992

Exogenous chromophores for the argon and Nd:YAG lasers: a potential application to laser-tissue interactions.

Chromophore dyes can be employed to modify laser-tissue interaction. A number of dyes have been investigated for their effect on the absorption and transmission of argon and Nd:YAG laser energy by vascular tissue in vitro. Three histological dyes have been assessed as potential chromophores for the argon laser and four infrared dyes for the Nd:YAG. Segments of porcine coronary artery to which dye had been applied were lased (1,064 nm, 2.5 W, 83 W/cm2, 60 s and 488/514 nm, 400 mW, 10.5 W/cm2, 60s) and the tissue temperature measured remotely using an infrared thermometer. In addition, energy transmission was measured with a photodiode and tissue morphological changes assessed histologically. All three argon dyes significantly increased energy absorption (typically 60 degrees C v. 20 degrees C at 60 s, P less than 0.001, 2-way ANOVA). Three of the four infrared dyes behaved similarly (40-70 degrees C v. 20 degrees C, P less than 0.001). All dyes significantly increased the initial rate of rise in tissue temperature during lasing. A reduction in energy transmission was observed for each of the Argon dyes but not for the Nd:YAG dyes. Histological evidence of thermal damage in control tissue first occurred for the argon and Nd:YAG lasers at 800 mW and 7.5 W without chromophore and at 400 mW and 2.5 W with the chromophore, respectively. A number of effective chromophores have therefore been identified at each wavelength.

Absorption↗
PubMed1992

Value of a radionuclide limb blood flow technique in the assessment of percutaneous balloon and dynamic angioplasty.

In a prospective study, a radionuclide technique was used to evaluate the limb blood flow (LBF) changes in 30 patients undergoing dynamic (n = 15) or balloon (n = 15) angioplasty for arterial occlusions or stenoses, respectively. The results were compared with Doppler Ankle Brachial Index (DABI) and treadmill exercise tests. Whilst LBF values (ml of blood flow per 100 ml of limb volume per min) were significantly lower in limbs with arterial occlusion than stenosis (4.5 +/- 0.46 and 6.4 +/- 0.74, respectively; P less than 0.05). DABI provided no discrimination. Immediately after balloon angioplasty, there was a fall in DABI, from 0.60 +/- 0.05 to 0.47 +/- 0.04 (P less than 0.05), which rose 24 h later to 0.73 +/- 0.02 (P less than 0.01). Following dynamic angioplasty, DABI improved from 0.60 +/- 0.05 to 0.66 +/- 0.02 (P less than 0.05). At 3 weeks, the LBF improved from 4.6 +/- 0.66 to 11.1 +/- 0.53 (P less than 0.001) following dynamic angioplasty and from 6.2 +/- 0.68 to 8.53 +/- 0.81 (P less than 0.001) following balloon angioplasty. "Normal" LBF (greater than 10 ml/100 ml per min) was achieved in 80% of patients who underwent successful dynamic angioplasty but in only 36% of the balloon group (P less than 0.05, chi 2-test). Reproducibility of repeated LBF measurements in control limbs was superior to that of DABI. This was indicated by a lower coefficient of variation, 13.8% compared with 25.2%, and a higher correlation coefficient, r = 0.79 compared with 0.27. Treadmill exercise tests were invalid or impossible in 30% of all occasions.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon↗
PubMed1992

Assessment of coronary stent by intravascular ultrasound.

The use of intravascular ultrasound to assess the adequacy of the deployment of an intracoronary stent is described. Although angiographically a good result was suggested, intravascular ultrasound showed this to be misleading.

Aged↗
PubMed1992

Stenting of the arterial duct: a new approach to palliation for pulmonary atresia.

OBJECTIVE: To assess the possibility of maintaining ductal patency in neonates with complex pulmonary atresia by percutaneous implantation of balloon expandable stents. PATIENTS: Two duct-dependent neonates with long segment pulmonary atresia, right sided aortic arch, and left sided arterial duct. RESULTS: Stents with final diameter of 3.5 or 4 mm and initial length of 7 or 15 mm were successfully positioned in the arterial duct. Two stents were required in one child and four in the other in order to stent the entire length of the duct. After the procedures the ducts remained widely patent and arterial oxygen saturations remained above 80%. Complications of the procedures included perforation of a peripheral pulmonary artery and cardiac perforation, both caused by guide wire manipulation. Both babies died suddenly, one at five weeks, and the other at nine days after successful stenting of the duct. Both ducts were patent at necropsy; the exact cause of one death was not clearly defined, but the second seemed to be caused by pneumococcal septicaemia. CONCLUSIONS: Stenting of the arterial duct is technically feasible. It provides adequate palliation for neonates with pulmonary atresia at least in the short term and it seems to result in balanced, central perfusion of both pulmonary arteries. This preliminary report suggests that this previously untried technique may prove to be a promising and attractive alternative to neonatal aortopulmonary shunt operation.

Dinoprostone↗
PubMed1992

Use of thermal imaging to monitor crural thrombolysis.

Intra-arterial thrombolysis is increasingly being used as the treatment of choice in selected cases of critical limb ischaemia. At present angiography is the established method of monitoring the progress of thrombolysis. We report a case in which thermal imaging was used in conjunction with angiography to monitor the effects of thrombolysis.

Adult↗
PubMed1992

The use of dobutamine stress thallium scintigraphy in the diagnosis of syndrome X.

Dobutamine stress thallium scintigraphy is a non-exercise stress technique used in the assessment of myocardial ischaemia. Non-exercise techniques are independent of the patient's exercise capacity or the subjective development of limiting symptoms. Preliminary data are presented regarding the effects of graded infusions of dobutamine (maximum 20 micrograms/kg/min) in seven consecutive patients with syndrome X. The dobutamine stress test caused significant increases in mean heart rate (rest 65.4 beats/min, peak dobutamine infusion 112.4 beats/min, P < 0.001) and systolic blood pressure (rest 138.6 mmHg, peak dobutamine infusion 166.7 mmHg, P = 0.002) and provoked typical symptoms in all the patients. Single photon emission computerized tomography was performed and the mean number of reversible defects was 1.86 per patient (range 1-3). One patient developed transient atrial fibrillation during the dobutamine infusion but there were no complications in the remainder of the study group. It is concluded that dobutamine-thallium scintigraphy in patients with syndrome X is safe, reproduces patients symptoms' reliably and presents a controllable degree of stress to the cardiovascular system. The consistent demonstration of a reversible perfusion defect in patients with syndrome X is evidence of abnormal myocardial physiology. This criterion could be added to those currently used to define syndrome X in order to improve objectively the identification of this patient group.

Aged↗
PubMed1991

Isotope limb blood flow measurement in patients undergoing peripheral laser angioplasty.

A technique of isotope limb blood flow (ILBF) measurement employing Technetium-labelled human albumin and a gamma camera, was used to assess limb perfusion in 19 patients undergoing percutaneous laser angioplasty, both before and one month after treatment. Twenty-three limbs with femoro-popliteal occlusions ranging in length from 3-35 cm (median 8 cm) were recanalized using an Nd-YAG laser and sapphire tipped optical fibre. Primary angiographic success was achieved in 19 lesions of which 6 re-occluded within the first month, and 13 remained patent with relief of symptoms. Clinically successful procedures were associated with a large increase in ILBF. However, normal blood flow was restored in only 54% of limbs. There was a slight decrease in limb perfusion after failed laser angioplasty but this was not statistically significant in this small series. Furthermore, there was no clinically apparent circulatory compromise, or need for urgent surgical bypass in failed cases. We conclude that ILBF is a useful means of assessing patients undergoing laser angioplasty, particularly for detecting small flow changes in patients who are unable to complete a standard exercise test. Its use can be recommended for assessing blood flow changes following other forms of limb revascularization.

Aged↗
PubMed1991

Computed tomography in the pre-operative assessment of mediastinal tumours--does it improve surgical management?

Computed tomography (CT) provides detailed imaging of the mediastinum. To assess whether this information improves subsequent surgical management 39 consecutive cases were reviewed. 21 patients had pre-operative CT of the mediastinum (CT group); 18 did not (No-CT group). The pre-operative use of CT resulted in the correct assessment of tumour consistency in 20 patients, the correct extent of invasion in 16, and the correct diagnosis in 10. In 15 of the 39 cases the surgical management was inappropriate because exploration was performed for an inoperable tumour, where no tumour was found, or when nonsurgical treatment was indicated. The number of inappropriate procedures was significantly lower in the CT group. These results suggest that the routine use of CT in the assessment of mediastinal tumours is justified by a subsequent improvement in surgical management.

Adult↗
PubMed1991

Percutaneous laser valvotomy with balloon dilatation of the pulmonary valve as primary treatment for pulmonary atresia.

A neonate with pulmonary atresia and an intact ventricular septum with a tripartite right ventricle was successfully treated by percutaneous balloon dilatation of the pulmonary valve. This was facilitated by previous laser valvotomy with a hot tip Trimedyne laser wire. There were no major complications. Four weeks later the patient was discharged home on no medication with peripheral oxygen saturations of 70% in air.

Catheterization↗