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Biomedical subjects

J F Reidy

Publications and source records attributed to J F Reidy.

At least 19 recordsLinked to original sources
PubMed1992

Embolization with detachable balloons--applications outside the head.

Detachable balloons, although widely used as an embolization material in neurovascular work, are rarely used outside the head. Yet they offer distinct advantages over other methods of embolization in certain situations. They can effect an instant and precise occlusion of large arteries and fistulae and unlike any other embolization technique the occlusion is reversible until the balloon is finally detached. In addition, they can be floated out to distal locations inaccessible with more conventional catheter techniques. They are inflated with contrast medium or silicone monomers. Large arteries and arteriovenous fistulae (AVFs) are best suited to balloon embolization where embolization distal to the fistula resulting in parenchymal infarction is not indicated. Thirteen patients underwent 14 detachable balloon embolizations. Eleven had large AVFs (4 coronary AVFs, 4 Blalock-Taussig shunts, 2 vertebro-vertebral fistulae and 1 renal AVF) and three had large arteries (2 aorto-pulmonary collaterals in one patient and 1 innominate artery pseudo-aneurysm). Twelve of these embolization procedures were successful and there were no complications. The two failures were due to inability to pass the balloon catheter around an acute angle in the introducer catheter and to early deflation. These cases illustrate a wide range of situations where balloon embolization may be used successfully. Continued refinement and improvement in the technique will allow expansion of the indications for non-neurological balloon embolization.

Adolescent↗
PubMed1992

The management of renal transplant artery stenosis in children by percutaneous transluminal angioplasty.

Between 1967 and 1989 in this unit 262 children (age at transplantation 9 months to 17 years, mean 9.6 years) had 345 renal transplants performed. Transplant artery stenosis (TAS) was found in 30 (8.7%) as demonstrated by arteriography, performed only when there was unexplained deterioration in transplant function, hypertension that was difficult to control, or in the presence of a vascular bruit. All patients with TAS except one had received a cadaveric allograft. From 1980 onward, percutaneous transluminal angioplasty (PTA) has been available for TAS, and this was attempted on 21 occasions in 16 patients. Nine patients demonstrated angiographic improvement following the procedure, and 7 showed immediate clinical improvement. On one occasion angioplasty precipitated graft loss. Five patients underwent planned corrective surgery, 4 after unsuccessful angioplasties. Our experience suggests that PTA should be the first method of intervention for TAS. Moderate success, both in angiographic and clinical terms, can be achieved, negating the need for surgery, while failure of PTA does not preclude surgical attempts at correction.

Adolescent↗
PubMed1992

Middle aortic syndrome: clinical and radiological findings.

Eight patients with the middle aortic syndrome are described. They were aged 2 months to 14 years at diagnosis; follow up was one to 11 years. Clinical presentations included asymptomatic hypertension (n = 5), severe headache, nose bleed, and chest pain (n = 1), and cardiac failure (n = 1). All had severe hypertension requiring multiple drug treatment. Diminished peripheral pulses were not helpful in the diagnosis, which is made on aortography. Associated clinical findings were Williams' syndrome (n = 3) and appreciable eosinophilia (n = 3). The differential diagnosis includes Takayasu's arteritis, fibromuscular dysplasia, and neurofibromatosis. Blood pressure was adequately controlled by medical treatment in six patients. Surgical angioplasty was performed in two. One patient remained normotensive without drug treatment 21 months after operation; the other died of sepsis and uncontrollable haemorrhage in the postoperative period. Medical treatment is satisfactory in most cases: surgery should be reserved for those in whom blood pressure cannot be controlled without unacceptable side effects of drug treatment. Although rare, the middle aortic syndrome should be considered in the differential diagnosis of hypertension when commoner causes have been excluded. Aortography is necessary for diagnosis.

Adolescent↗
PubMed1991

Validation of a quantitative radiographic technique to estimate pulsatile blood flow waveforms using digital subtraction angiographic data.

We have validated a new radiographic technique for determining pulsatile volume flow in arteries following an intraarterial injection of contrast material. Instantaneous blood velocities were estimated by generating a parametric image from dynamic angiographic images in which the image grey level represents contrast material concentration as a function of time and distance along a vessel segment. Adjacent concentration--distance profiles in the parametric image were shifted with respect to distance until a match occurred. A match was defined as the point where the sum of squares of the differences in the two profiles was a minimum. The distance translated per frame interval gives the instantaneous contrast material bolus velocity. We have validated the technique using an experimental phantom of blood circulation, consisting of a pump, flexible plastic tubing, the tubular probe of an electromagnetic flowmeter (EMF) and a solenoid, to simulate a pulsatile flow waveform, which includes reverse flow. Small boluses of contrast material can be injected at various positions in the circuit. Measurements of pulsatile velocity flow were taken at 40 ms intervals, using a tube of 6.6 mm internal diameter and an imaged tube length of 200 mm. The shape of the flow velocity waveform was faithfully reproduced but there was an overestimation of peak velocity of 40% at low velocities (peak velocity of 540 mm s-1), reducing to 19% at peak velocities of 964 mm s-1 with an underestimation of 16% at the peak velocities of 1899 mm s-1. The validation was repeated for distances ranging from 130 to 230 mm between injection and measurement sites and for imaged tube lengths varying from 200 to 20 mm.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Transcatheter embolization in the treatment of coronary artery fistulas.

Seven patients with a coronary artery fistula underwent percutaneous transcatheter embolization (five were male and two female; the age range was 2 to 67 years [median 17]). Three patients were symptomatic. The left to right shunt ranged from 1.6 to 2.6:1. In six patients, the fistula was an isolated congenital anomaly; in one, it was acquired. The fistula arose from branches of the left (n = 5) and right (n = 2) coronary arteries and drained to the right ventricle (n = 2), right atrium (n = 2), coronary sinus (n = 1), pulmonary artery (n = 1) and a bronchial artery (n = 1). Different embolization techniques were used to occlude eight feeding arteries. The embolization materials included a detachable balloon (n = 3), coaxial embolization with platinum microcoils (n = 3), a combination of detachable balloon and microcoil (n = 1) and standard steel coils (n = 1). Satisfactory occlusion was achieved in six patients. In one case, the valve of the detachable balloon was damaged, resulting in early balloon deflation and a residual fistula. There were no associated complications in any patient. Follow-up investigation by Doppler ultrasound or coronary angiography 4 months to 4 years later showed that permanent occlusion was achieved in all six patients in whom embolization was initially successful. Transcatheter embolization should be considered the treatment of choice for coronary artery fistulas.

Adolescent↗
PubMed1991

Quickscan: Doppler ultrasound emulation of angiography--its value prior to arteriography in peripheral vascular disease.

The prevalence of peripheral vascular disease demands a quick, reliable, non-invasive technique for initial assessment. We have devised a new method which combines the two physical principles that (1) Doppler shift is proportional to blood velocity and (2) blood velocity is inversely proportional to arterial cross-section with the ability to track probe position using a non-contacting method. An image of the probe track and any arterial narrowing is shown superimposed on an outline of the patient. Pressure measurement, scan and graphics with final report take about 20 minutes. The accuracy of this system in peripheral vascular disease was evaluated. Thirty-one patients underwent quickscan (QS) and arteriography within an average time of 7 days. Abdominal aorta, common iliac-common femoral, superficial femoral and popliteal artery segments were graded independently as normal, significant stenosis (greater than 50% of diameter) or occluded by both techniques. Of 197 segments, QS correctly assessed 106 normal, 22 stenosed and 28 occluded segments. Four equivocal angiographic stenoses were normal on QS and three severe stenoses were graded occlusion. Fifteen segments on angiography and five on QS were not assessed. For the iliac and superficial femoral artery segments, sensitivity and specificity averaged 77% and 86%, respectively, for all grades. Aortic statistics were invalid (only one significant lesion). Six out of eight popliteal occlusions were correctly diagnosed by QS, but no popliteal stenoses were detected out of six shown on arteriography. Low numbers may contribute to this discrepancy but an improved popliteal scanning method may be necessary. We find initial QS an invaluable aid to direct percutaneous angiography and to indicate potential sites for angioplasty.

Adult↗
PubMed1991

Arteriovenous fistulas complicating biopsy of renal allografts: treatment of bleeding with superselective embolization.

The use of superselective embolization was assessed as a treatment for bleeding from postbiopsy arteriovenous fistulas (AVFs) in renal transplants. AVFs commonly occur after biopsy procedures in renal transplants, but severe bleeding is rare. Transcatheter embolization can be used to control bleeding, but unless it is sufficiently selective, the procedure results in loss of significant amounts of renal parenchyma. During a 4-year period, embolization procedures were attempted in seven patients 30-65 years old. All had AVFs shown on arteriography. Five patients underwent embolization; occlusion occurred only in the branch supplying the AVF. In one patient with three large AVFs, two were found to have occluded the day after embolization was attempted. In another, an AVF occluded when superselective catheter position was achieved but before embolization. Catheter manipulation in these cases may have precipitated occlusion. In five cases, coaxial embolization techniques were used. Embolization materials consisted of coils in three cases: 0.038 in. (0.97 mm) in one case, 0.025 in. (0.64 mm) in one case, 0.018 in. (0.46 mm) in one case; 0.038 in. (0.97 mm) coils and gelatin foam particles in one case; and localized contrast extravasation in one case. Serum creatinine level was measured before and after embolization in all patients, and radionuclide studies were undertaken in three cases. In all patients, bleeding was effectively controlled. None of the patients showed an increase in serum creatinine level after embolization, and in four, significant improvement was seen. Nuclear medicine studies showed no loss of renal function and a dramatic improvement in one patient. No complications due to the procedure were seen. Our experience suggests that superselective embolization with coaxial catheter techniques is an effective method of treating bleeding from postbiopsy AVFs in renal transplants with minimal loss of renal parenchyma.

Adult↗
PubMed1990

Splenic artery aneurysm embolisation--the preferred technique to surgery.

A case of embolisation of a splenic artery aneurysm is presented. The aneurysm and proximal splenic artery were successfully occluded with steel coils and there were no associated complications. Transcatheter embolisation-should be the treatment of choice for splenic artery aneurysms. The procedure carries less morbidity than surgery and more importantly allows preservation of the spleen and its function.

Aneurysm↗
PubMed1990

Embolisation of a complex coronary arteriovenous fistula in a 6 year old child: the need for specialised embolisation techniques.

Transcatheter embolisation was performed in a six year old child with a large haemodynamically significant arteriovenous fistula between the left coronary artery and right ventricle. The fistula seemed to fill via a single large septal branch of the left anterior descending coronary artery. This was occluded distally with a detachable balloon backed up by a proximal coil. After this the flow through the fistula was considerably reduced but it still filled via a small diagonal branch that had not been noted previously. This branch was subsequently occluded in its most distal part by a coaxial catheter technique and a single microcoil. Complete occlusion of the fistula was produced and there were no complications.

Arteriovenous Malformations↗
PubMed1989

Increased incidence of renal transplant arterial stenosis in children.

We have found an increase from 10% to 16.4% in the incidence of clinically significant transplant arterial stenosis since the introduction of cyclosporin immunosuppression. During the same period there has been a coincidental increase in the use of donor kidneys harvested from children less than 6 years of age. In patients treated with cyclosporin these stenoses of the donor artery are not related to the surgical anastomosis, and have only rarely been associated with clinical or histological evidence of rejection, whereas those patients who have developed transplant arterial stenosis whilst receiving azathioprine have had a higher incidence of rejection. Regardless of immunosuppressive regimes, the use of small donor kidneys appears to be the most significant association with transplant arterial stenosis in our experience, and this finding has major implications for cadaveric renal transplantation in children.

Adolescent↗