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Biomedical subjects

M R Rees

Publications and source records attributed to M R Rees.

At least 19 recordsLinked to original sources
PubMed2005

The effect of Butterworth and Metz reconstruction filters on volume and ejection fraction calculations with 99Tcm gated myocardial SPECT.

This study was carried out to measure the differences produced by change of reconstruction filter in calculations of left-ventricular end-diastolic volumes, end-systolic volumes, stroke-volumes and left-ventricular ejection-fractions from (99)Tc(m) Sestamibi (Bristol-Myers Squibb) gated myocardial perfusion SPECT studies. 30 patients had gated SPECT myocardial perfusion imaging at rest. The acquired projections were separately filtered with two filters, a low-pass filter (Butterworth) and an edge-enhancement filter (Metz). Each study was then further processed to determine left-ventricular end-diastolic volume, end-systolic volume, stroke volume and ejection fraction, and to assess defect size. The results for each patient with the two filters were compared. Calculated end-diastolic volumes, end-systolic volumes and left-ventricular ejection fractions, for each filter, were well correlated. Stroke volumes showed worse correlation. The differences between left-ventricular ejection-fractions, end-diastolic volumes and end-systolic volumes were statistically significant. There was no significant difference in stroke volumes. Ejection fractions were inversely correlated with defect size, but change in ejection fraction due to filter was not. End-diastolic and end-systolic volumes were correlated with defect size, but change in volumes due to filter was not. Thus the results for changes produced by choice of filter are not dependent on defect size. Using different reconstruction pre-filters in gated myocardial perfusion SPECT significantly changes the results of calculations of physiological parameters. Each centre should be consistent in the use of filters as this may affect the clinical consequences of the result.

Adult↗
PubMed2005

In vivo validation of a novel semi-automated method for border detection in intravascular ultrasound images.

The aim of this work was to evaluate a new semi-automated intravascular ultrasound (IVUS) border detection method. The method was used to identify the lumen and the external elastic membrane or the borders of stents in 80 IVUS images, randomly selected from 10 consecutive human coronary arteries. These semi-automated results were compared with observations of two experts. Several indices in each case were obtained in order fully to evaluate the method. The time required for identification of the borders was also recorded. The interobserver variability of the method ranged from 1.21% to 5.61%, the correlation coefficient from 0.98 to 0.99, the slope was close to unity (0.94-1.03), the y intercept close to zero and the Williams index value was close to unity (range 0.67-0.91). The time (mean+/-SD) required for the method to identify the borders of the different vessel layers for the whole IVUS sequence was 5.2+/-0.2 min. The results demonstrate that the method is reliable and capable of identifying rapidly and accurately the different vessel layers depicted in IVUS images.

Aged↗
PubMed2001

The use of gated perfusion scanning in the assessment of left ventricular volume.

A total of 34 patients underwent both gated SPECT perfusion imaging and echocardiography, with each test blinded to the other. Wall motion analysis, calculation of ejection fraction and ventricular volume were obtained by each technique. A close correlation was observed between the ejection fractions calculated by each method (r=0.79). There was a less close relationship between the left ventricular volumes calculated by each method (r=0.61) this is probably due to the errors which result from geometric assumptions for each technique. Wall motion analysis revealed a good level of agreement between each method with no significant discrepancies between the techniques.

Adult↗
PubMed2001

Vibrational angioplasty in the treatment of chronic femoropopliteal arterial occlusions: preliminary experience.

PURPOSE: To evaluate the safety and efficacy of vibrational angioplasty in chronic femoropopliteal arterial occlusions. METHODS: Six patients (5 men; ages 52 to 84 years) with peripheral arterial occlusive disease were treated percutaneously using vibrational angioplasty to recanalize the lesion. Three occlusions ranging from 10 to 15 cm long were in the superficial femoral artery (SFA), while 3 other diffusely diseased popliteal arteries were occluded distally (length from 3.5 to 4.5 cm). Vibrational angioplasty using coronary equipment was applied to assist passage of a coronary guidewire, which was followed by conventional angioplasty. Follow-up surveillance featured periodic physical examination, ankle brachial index measurements, and duplex scanning. RESULTS: In all 6 cases, recanalization of the occlusions was successful and without complications. The time to cross the occlusions with the wire ranged from 20 to 25 minutes for the SFA lesions and from 4 to 10 minutes for the popliteal occlusions. Two SFA occlusions were treated with stent implantation. Over a follow-up of 3 to 9 months, all treated vessels were patent. In 3 patients with skin ulcers, healing of the ulcers was observed. CONCLUSIONS: Vibrational angioplasty using coronary guidewires seems to be a promising ancillary technique in the management of chronic femoropopliteal arterial occlusions.

Aged↗
PubMed2000

Vibrational angioplasty and hydrophilic guidewires in the treatment of chronic total coronary occlusions.

PURPOSE: To study the efficacy and safety of vibrational angioplasty versus hydrophilic guidewires for recanalizing chronic total occlusions (CTOs) of the coronary arteries. METHODS: In a retrospective study, 99 patients with old (>3 months) CTOs resistant to conventional techniques were treated either with vibrational angioplasty (group A, n = 72) or 0.014-inch hydrophilic guidewires (group B, n = 27). The selection of the technique (vibrational angioplasty or hydrophylic guidewires) was dependent only upon device availability. A variety of guidewires were employed in conjunction with vibrational angioplasty. RESULTS: The crossing success rates in groups A and B were 86.1% (62/72) and 55.5% (15/27) (p < 0.05), with final procedural success rates of 75% (54/72) and 44.4% (12/27) (p < 0.01), respectively. The main reasons for failure were inability to cross the lesion with a guidewire (10/18 in group A and 12/15 in group B) and large dissections resulting in vessel closure (2/18 in group A and 2/15 in group B). Three major complications were seen, 2 in group A and 1 in group B. Three vessel perforations were reported in group A. Both techniques needed prolonged fluoroscopy times. CONCLUSIONS: Vibrational angioplasty was more successful in treating CTOs compared to hydrophilic guidewires and had similar complication rates (most without clinical sequelae).

Adult↗
PubMed1999

Use of vibrational angioplasty for the treatment of chronic total coronary occlusions: preliminary results.

The aim of the study was to investigate the feasibility and clinical safety of vibrational angioplasty in the treatment of chronic total coronary occlusions and evaluate the clinical and angiographic factors that are predictive of the procedural success and complications of the procedure. Seventy-eight patients with chronic total occlusions (>3 months) resistant to conventional techniques were treated by vibrational angioplasty using a variety of conventional guidewires. Lesions were successfully crossed in 67 (85.9%) cases and antegrade flow was achieved in 59 (75.5%). Major complications (myocardial infarction and tamponade) occurred in two (2.5%) patients, but no fatalities ensued. Angiographically detectable dissections were seen in 23 (29.5%) patients but only resulted in vessel compromise and reclosure in 5 cases. Multiple stepwise logistic regression analysis identified the duration (<6 months, P = 0.008) and the length of the occlusion (<15 mm, P = 0.03) as independent predictors of final success and the age of the patient (<55 years, P = 0.006) as the only independent predictor of procedural complications. Vibrational angioplasty is a safe technique useful in the treatment of chronic coronary occlusive disease. Patients in whom the procedure is likely to prove most successful may be easily identified by clinical and angiographic features (duration and length of occlusion).

Adult↗
PubMed1999

The use of soft and flexible guidewires in the treatment of chronic total coronary occlusions by activated guidewire angioplasty.

Activated guidewire angioplasty (AGA) is a new technique which has been designed to assist in angioplasty of total occlusions. The purpose of this study was to determine the safety and efficacy of using flexible relatively soft guidewires (floppy wires) in conjunction with this technique and also to determine the predictors of lesion crossing and final success by this technique in patients with chronic total coronary occlusions. 73 patients with 73 chronic total coronary occlusions in whom coronary angioplasty using conventional techniques had failed were treated with AGA using floppy guidewires. The success of crossing these lesions was 65.7% (48/73) resulting in a final angioplasty success of 56.1% (41/73). Angioplasty success was reduced compared with crossing success in seven arteries in which complications occurred during balloon angioplasty. Multiple stepwise logistic regression analysis identified the location of the occlusion (right coronary artery, p = 0.005) as independent predictor of crossing success of this technique and the male gender (p = 0.03), the duration of occlusion (p = 0.05), the lesion length (p = 0.01) and the location of the occlusion (right coronary artery, p = 0.02) as independent predictors of final procedural success of the method.

Adult↗
PubMed1998

Fast rotating atherectomy catheter tip inhibits platelet aggregation and ATP release: a study using platelet-rich plasma.

The interaction of atherectomy devices with the arterial wall is the focus of many studies, but their effect on the surrounding blood is largely unknown. This is a detailed investigation on the effects of a rotational atherectomy device with a fast rotating tip on platelet structure and function. Platelet-rich plasma (PRP) was obtained from six volunteers, divided into 5 mL samples, and subjected to the atherectomy tip rotating at 20, 40, or 80 thousand rpm for 30 or 60 seconds. Platelet aggregation to collagen or adenosine diphosphate (ADP) was obtained in all samples by means of a dual-chamber optical aggregometer. The fast rotating catheter tip caused marked inhibition of platelet aggregation to both collagen and ADP. The maximum extent of aggregation was reduced from 85% +/-2.8 in control to 46% +/-4.8 with collagen (p<0.01) and from 86.1% +/-6.9 to 25.1% +/-4.3 with ADP (p<0.01). The rate of aggregation (measured at 4 minutes) dropped from 81.3% +/-2.7 to 40% +/-4.5 and from 73.9% +/-8.5 to 12.5% +/-2.6 (p<0.005) with collagen and ADP, respectively. These effects were related to rotating speed and duration of exposure. ATP release in response to collagen fell from 2.63 +/-0.13 nMol in control to 0.7 +/-0.1 nMol, p<0.001 after exposure to the rotating tip. There was no significant change in platelet count, nor was there formation of platelet aggregates (platelet aggregate ratio remained unchanged) to account for these phenomena. Furthermore, transmission electron microscopy showed no significant platelet disruption or release of granules, and little signs of activation were seen even after addition of collagen. This is the first study to demonstrate that exposure to a fast rotating catheter tip inhibits in vitro platelet aggregation and ATP release. There were no apparent loss of integrity of platelet structure, release of granules, or formation of platelet aggregates. This phenomenon and its clinical implication justify further investigation.

Adenosine Triphosphate↗
PubMed1995

Activated-guidewire technique for treating chronic coronary artery occlusion.

Coronary angioplasty was successfully carried out with an activated guidewire technique in 33 of 47 patients who had undergone a failed attempt at conventional angioplasty for the treatment of chronic coronary artery occlusion. 80% of these occlusions were stump-like occlusions. This technique involves the attachment of a hand-held battery-driven motorised device to standard angioplasty equipment and can be used at any time during the procedure. The device generates complex vibratory movement in the guidewire to facilitate crossing of occluded vessels.

Adult↗
PubMed1995

Innovation in clinical method: diabetes care and negotiating skills.

The development of a method to facilitate clinical negotiation with diabetic patients is described. The principles of the method incorporate patient centredness, an assessment of readiness to change and some elements of motivational interviewing. A simple low cost technology is part of the innovative method. Details of the method and its application are published before the results of a randomized controlled trial to ensure that the techniques are in the public domain before the outcome of the trial is known.

Clinical Competence↗
PubMed1995

Technical note: femoral angiography using the reverse shuffle technique.

We report our findings using the "reverse shuffle" technique of stepping table femoral angiography. This technique represents a simple modification of the conventional stepping table sequence entailing a reverse table movement allowing acquisition of early and late films in the distal positions. It was developed in order to minimize the number of runs required in each examination. In a retrospective study 52/53 (98%) of angiograms using the reverse shuffle technique required only a single run compared with 30/51 (58%) using the conventional technique. We believe that the reverse shuffle should be used where possible when stepping table angiography is performed. Furthermore, the incorporation of a reverse table movement may also be advantageous in angiography using automated digital subtraction angiography (DSA) stepping systems.

Aged↗
PubMed1994

Percutaneous transluminal angioplasty of the tibial arteries.

To evaluate the results of percutaneous transluminal angioplasty (PTA) of the tibial vessels, results of 50 procedures performed in 38 patients since 1988 were analysed retrospectively. A total of 73 tibial vessels were treated: 32 anterior tibial arteries, 16 posterior tibial arteries, four peroneal arteries, 12 tibioperoneal trunks and nine trifurcation lesions. Forty-four of 50 PTA procedures were performed in conjunction with interventions in the femoropopliteal arteries and six as isolated procedures. One patient required a femorodistal graft following perforation of the popliteal artery during atherectomy. Distal emboli occurred in two patients and acute thrombosis of both the angioplastied tibial vessels occurred in a third. The technical success rate was 96 per cent. Patients were followed for a mean(s.d.) of 21(13) months. At the latest follow-up, 58 per cent had improved clinically. There were significant improvements in 43 per cent of limb isotope blood flow studies and 52 per cent of ankle:brachial Doppler pressure indices in treated limbs at this time. PTA should be the first treatment option in patients with infrapopliteal arterial disease needing intervention, whenever it is technically feasible.

Adult↗
PubMed1994

Percutaneous laser recanalisation of femoropopliteal occlusions using continuous wave Nd-YAG laser and sapphire contact probe delivery system.

A conventional continuous wave Nd-YAG medical laser system delivered by transparent sapphire tipped optical fibres was used for percutaneous recanalisation of 32 chronic femoropopliteal occlusions in 27 patients (19 men, eight women; median age 68 years, range 46-83 years). Twenty-four patients had severe intermittent claudication and three had critical ischaemia. The median occlusion length was 8 cm (range 3-35 cm) and lesions were not negotiable by guidewire. Laser energy was delivered at powers of 10-15 Watts using intermittent 1 second emissions (mean total energy 315 Joules, range 30-1015]). The sapphire tips used were 1.8 to 3.0 mm diameter. After laser recanalisation adjunctive balloon dilatation was necessary to widen the resulting lumen. All patients received anti-platelet therapy. Initial clinical success was achieved in 22 limbs (69%) with symptomatic relief and increase in mean (+/- S.D.) ankle-brachial pressure ratio from 0.52 (+/- 0.25) to 0.80 (+/- 0.21) [Mann-Whitney U, p < 0.001]. Recanalisation was unsuccessful in all calcified lesions (four cases). There was a high incidence of vessel perforation (28%) and wall dissection (25%). Emergency surgery was not required after failed procedures. The median follow-up was 12 months (range 6-20 months). By 6 months, 15 of 22 successfully recanalised lesions (68%) had reoccluded. The cumulative primary patency at 1 year was only 12%. These disappointing results do not support routine use of this system. Clearly, modifications of the laser/delivery system or the technique, or both, are required. The aim should be to achieve sole laser recanalisation without concomitant balloon dilatation.

Aged↗
PubMed1994

Coronary angioplasty in high risk patients with percutaneous cardiopulmonary support.

Cardiopulmonary Support (CPS) was employed electively in 13 patients during high risk percutaneous transluminal coronary angioplasty (PTCA) in accordance with a selection criteria, which included at least two of the following; (i) left ventricular ejection fraction of less than 35%, (ii) target vessel(s) supplying more than 50% of the viable myocardium, and (iii) patients refused coronary bypass surgery. The mean age of the patients was 56.8 +/- 10.7 years (range 39-77). PTCA was attempted in a total of 35 lesions in 12 patients; 29 lesions were successfully dilated (technical success rate of 82.9%). On average, 2.7 lesions were attempted in each patient, and 2.2 lesions were successfully dilated per patient. In one patient the procedure was abandoned due to dissection of the iliac artery during cannulation. One patient died of a large pulmonary embolism 72 h after the procedure. All the surviving 11 patients who had successful PTCA on CPS showed symptomatic improvement during a mean follow-up period of 18.5 +/- 4.3 months (range 11 to 24 months). The commonest complication encountered following the CPS-assisted PTCA was local haematoma (nine of 13 patients), but all patients required transfusion due to significant periprocedural blood loss. Our early experience suggests that CPS enhances the safety of undertaking PTCA in high risk patients.

Adult↗
PubMed1994

Limb blood flow measurement in technically successful balloon angioplasty.

An isotope limb blood flow technique was used to assess the outcome of technically successful balloon angioplasty. Measurements were made on a total of 120 limbs, before angioplasty and at least once after angioplasty at 3 weeks, 3 months, 6 months, 12 months and 2-5 years. 67% of treated limbs showed a significant improvement in limb blood flow at 3 weeks. At 12 months following angioplasty 43% of limbs still showed an improvement in blood flow compared with the measurement made before angioplasty. However, a number of these limbs showed a significant fall in limb blood flow between 3 weeks and 12 months even though the 3 week and the 12 month flow figures were still greater than those before angioplasty. The degree of initial improvement in blood flow seen at 3 weeks persisted at 12 months after angioplasty without significant fall in only 30% of limbs. In 33% of limbs where the balloon angioplasty was technically successful there was no improvement in blood flow at 3 weeks. 80% of these limbs had further significant untreated disease angiographically, compared with 43% of limbs where there was an increase in limb blood flow.

Angioplasty, Balloon↗