PubMed Health⌕ Search

Biomedical subjects

M Tynan

Publications and source records attributed to M Tynan.

At least 73 records · Page 4Linked to original sources
PubMed1990

Magnetic resonance imaging of the great arteries in infants.

Sixty infants, aged 1-48 (median 8) weeks, with suspected congenital heart disease underwent a morphological evaluation of the great arteries using magnetic resonance imaging at 1.5 Tesla. Cross-sectional echocardiography was performed in all infants, angiography in 33 and surgery in 44. Multiple sections, 5 mm thick and gated to the patients' electrocardiogram were acquired in standard and oblique imaging planes. Ventriculo-arterial connexions were correctly identified in 54 infants (6 did not have intracardiac imaging performed) and an accurate description of the relationships of the great arteries was made in all. Magnetic resonance imaging clearly demonstrated normal and hypoplastic pulmonary arteries to the level of the first hilar branches and was better than echocardiography at confirming the presence or absence of central intrapericardial pulmonary arteries in 4 infants with pulmonary atresia. All parts of the thoracic aorta were accurately demonstrated and, in 23 infants with clinical suspicion of aortic coarctation, magnetic resonance images provided more information than echocardiography. Magnetic resonance imaging accurately demonstrates great arteries non-invasively supplementing echocardiographic and angiographic findings. In many cases, it replaces the need for invasive investigations.

Aorta, Thoracic↗
PubMed1990

Doppler evaluation of superior caval venous pathways after Mustard and Senning operations.

Doppler waveforms from the superior caval vein were analysed to evaluate the patency of superior caval venous pathways following venous redirection (Mustard and Senning) operations for complete transposition. The group consisted of 26 unselected survivors of Mustard (9 patients) and Senning operations (17 patients). Patients were examined a mean of 5.9 (range 0.1-15.3) years following operation and their age at study ranged from 0.4-25.3 years, mean 7.3 years. Doppler waveforms were correlated with digital subtraction angiograms, which were performed in every patient within 24 hours of the Doppler study. Totally occluded superior caval venous pathways were identified in 3 patients with digital subtraction angiography. The remaining patients had angiographically patent pathways. In the 23 patients with patent pathways, Doppler waveforms demonstrated an initial systolic peak smaller than a second diastolic peak. In the 3 patients with totally occluded pathways, the pattern of the waveform was reversed, with the systolic larger than the diastolic peak. Doppler examination of the superior caval vein is a quick and simple bedside method of accurately determining patency of superior caval venous pathways after atrial redirection procedures for complete transposition.

Adolescent↗
PubMed1990

Balloon dilatation of critical stenosis of the pulmonary valve in neonates.

Percutaneous balloon dilatation was attempted in 15 consecutive neonates (mean age 7.3 (range 1-27) days and weight 3.2 (range 2.5-4.1) kg) with critical stenosis of the pulmonary valve. Dilatation was successful in 11 (73%) patients. The mean balloon to annulus ratio was 1.1 (range 0.6-1.77). The ratio of right ventricle to femoral artery systolic pressure decreased from a mean (1 SD) of 1.4 (0.32) before to 0.8 (0.24) after dilatation and the transvalvar gradient decreased from 81 (29.7) mm Hg before to 33 (27.7) mm Hg after dilatation. All four (27%) patients in whom dilatation was unsuccessful underwent surgical valvotomy. Complications of balloon dilatation occurred in three (20%) patients; these included retroperitoneal haematoma (one) and iliofemoral venous occlusion (two). In one (7%) patient severe hypoxia and hypotension developed when the valve was crossed with a guide wire and balloon catheter. Despite successful dilatation he died 7 days after the procedure. During a mean (1 SD) follow up of 2 (1.7) years, seven (64%) of the 11 patients remained free of important restenosis. One patient required repeat dilatation three weeks after the initial procedure. In three (27%) patients restenosis developed 4-9 months after dilatation and all three had surgical valvotomy. Of the four patients initially referred for surgery three required a second operation and one required balloon dilatation. Percutaneous balloon dilatation gave effective relief of critical pulmonary stenosis in most neonates but complications and restenosis requiring surgery were common.

Blood Pressure↗
PubMed1990

Percutaneous transcatheter myectomy of subvalvar pulmonary stenosis in tetralogy of Fallot: a new palliative technique with an atherectomy catheter.

A male infant with tetralogy of Fallot was given a modified left Blalock-Taussig shunt at 11 days of age because of duct dependence. Twenty months later, because of increasing cyanosis and polycythaemia, he was given palliative treatment with balloon dilatation of the right ventricular outflow tract. Seven months later a right ventricular angiogram showed further progression of the infundibular stenosis with poor anterograde opacification of the pulmonary arteries. He underwent percutaneous transcatheter myectomy of the infundibulum with an atherectomy catheter. One month later he was well and less cyanosed.

Cardiac Catheterization↗
PubMed1990

An evaluation of right and left ventricular function after anatomical correction and intra-atrial repair operations for complete transposition of the great arteries.

Anatomical correction of complete transposition of the great arteries has the potential advantage over intra-atrial repair in that the left ventricle becomes the systemic pump. To investigate the importance of this, we evaluated right and left ventricular function in 21 patients after anatomical correction and in 21 patients after Mustard or Senning operations. First-pass and equilibrium-gated radionuclide angiography were used to measure right and left ventricular ejection fractions between 17 and 78 (mean, 47) months after anatomical correction and between 3 and 187 (mean, 67) months after intra-atrial repair. The mean age of the patient groups at the time of study was 52 and 84 months, respectively. The right ventricular ejection fraction ranged from 35% to 78% (mean, 58%) in patients after anatomical correction and from 27% to 68% (mean, 51%) after intra-atrial repair (p = 0.066). The left ventricular ejection fraction ranged from 39% to 74% (mean, 58%) after anatomical correction and from 35% to 74% (mean, 58%) after intra-atrial repair (p = 0.86). The mean right and left ventricular ejection fractions of both groups were significantly lower than those of normal children. Individuals with systemic ventricular dysfunction were identified after both types of operations; however, symptomatic dysfunction occurred only after intra-atrial repair (p = 0.24).

Cardiac Surgical Procedures↗
PubMed1989

Magnetic resonance imaging of coarctation of the aorta in infants: use of a high field strength.

Nineteen infants with suspected coarctation of the aorta were studied with electrocardiographically gated magnetic resonance imaging on a 1.5 T whole body imaging system. In all cases imaging was successful and produced diagnostic images of high resolution. Coarctation was shown in 12 cases. The position and shape of the coarctation were well displayed by the magnetic resonance images. In addition, they clearly showed the relation of the coarctation to arteries arising from the aortic arch and to the length and diameter of the aortic isthmus and the distal aortic arch. The anatomy was confirmed at operation in all 12 patients, except for two with a small ductus arteriosus (arterial duct), which was not seen in the magnetic resonance images. In the seven remaining patients, coarctation was excluded. Magnetic resonance imaging produced high quality images that showed the anatomy better than other non-invasive methods. It provided all the anatomical information required for surgical correction.

Aorta, Thoracic↗
PubMed1989

Magnetic resonance imaging at a high field strength of ventricular septal defects in infants.

Magnetic resonance imaging at a high field strength has potential benefits for the study of the heart in infants, which is when most congenital heart disease presents. Seventeen infants with various anatomical types of ventricular septal defect were studied by this technique. Good quality, high resolution, images were obtained in every case. There were no major practical problems. The morphology of the defects in all 17 hearts was displayed in great detail. In some instances, the interpretation of the images resembled that of equivalent images from cross sectional echocardiography. But this new technique allowed imaging in planes that cannot be obtained by echocardiography. One particularly valuable plane gave a face on view of the inlet and trabecular components of the septum. This allowed very precise localisation of defects in these areas. The relation between the defects and the atrioventricular and arterial valves was exceptionally well shown in various different imaging planes. One patient in the series had multiple trabecular defects that were clearly shown. Magnetic resonance imaging gives detailed morphological information about ventricular septal defects.

Heart Septal Defects, Ventricular↗
PubMed1988

A quantitative evaluation of aortic regurgitation after anatomic correction of transposition of the great arteries.

Twenty patients who had undergone anatomic correction of transposition of the great arteries were assessed by Doppler echocardiography or cardiac catheterization, or both, to identify the presence of aortic regurgitation. The severity of aortic regurgitation was evaluated by radionuclide angiographic measurement of the stroke volume index a mean of 47.1 months postoperatively. The stroke volume index was defined as the ratio of the stroke counts between the left and right ventricles. A value greater than 1.8 was considered to indicate significant left ventricular volume overload. Eight patients (40%) were shown to have various degrees of aortic regurgitation by Doppler echocardiography or cardiac catheterization, or both. The mean (+/- SD) stroke volume index was 1.03 +/- 0.15 in these patients and 1.01 +/- 0.21 in the 12 patients without aortic regurgitation (p = NS). The stroke volume index was not above the normal range in any patient, indicating that the degree of aortic regurgitation present was trivial. This medium-term study indicates that trivial or mild aortic regurgitation is a frequent finding after anatomic correction of transposition of the great arteries. However, it rarely results in an audible cardiac murmur or significant left ventricular volume overload. Long-term evaluation is required to determine its importance.

Aortic Valve Insufficiency↗
PubMed1988

Balloon angioplasty in congenital heart disease.

Balloon angioplasty and valvuloplasty offer an alternative to surgery in many congenital cardiac conditions and are a useful adjunct in others. To yield optimal results, the most desirable improvement in hemodynamics with the least amount of damage to normal tissue, choice of the catheter should take into consideration the size of the balloon, type of shaft and shape of the balloon. Experience has shown that dilatation is best achieved when the size of the balloon is such that there is a combination of circumferential force, the stress exerted when the balloon is near its maximal diameter, and longitudinal force, the extent of which is directly proportional to the deformity of the balloon. If the balloon is too small, little benefit may be accrued from the procedure; if it is too large, there is a risk of danger to adjacent normal structures. A stiff shaft helps to maintain a stable position during inflation and the size of the shaft determines the caliber of the guidewire lumen and the inflation/deflation lumen. A single, circular balloon has the advantage of distributing the dilating forces uniformly during inflation; more recently introduced alternative designs with two or three balloons mounted around the shaft have the advantage of allowing some blood flow to occur even at full inflation but they also have the theoretical disadvantage of not ensuring an even distribution of circumferential force. Dilatation of pulmonary valve stenosis may be considered indicated in the presence of a pressure gradient of 40 mm Hg with a right ventricular pressure of 60 mm Hg as the lower limit. In the newborn, this may be qualified by setting the lower limit of right ventricular pressure as 10 mm Hg below systemic arterial pressure if that is 60 mm Hg or less. On choice of the proper balloon size, approximately 20 to 30 percent greater than the pulmonary root, success may be expected in 90% of the cases and, in general, the initial result appears to be that which persists. Although Doppler echocardiography frequently shows pulmonary regurgitation, this is rarely clinically evident. The procedure is safe and only few complications have been reported. Establishing the indication for aortic valvuloplasty usually requires the presence of a systolic gradient of 60 mm Hg without severe regurgitation; mild aortic regurgitation is not a contraindication to the procedure. Reports have indicated good results in both infants and children. This procedure is not without risk and deaths have been reported.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1987

The pathology of balloon pulmonary valvoplasty.

The pulmonary valve was examined following balloon dilation of pulmonary valve stenosis in six children. Stenosis was due to commissural fusion in two. In these patients, cineangiography showed that the valve was slightly thickened and "domed" during systole. Balloon valvoplasty produced complete separation of fused commissures in one and partial separation in the other. Commissural splitting is likely to be the most common mechanism of relief of pulmonary stenosis by balloon dilation. Incomplete separation could account for the partial reduction of the gradient in most children treated with this technique. Four children had pulmonary valve dysplasia. Balloon valvoplasty did not produce haemodynamic improvement or morphological changes that were identifiable at the time of surgical correction. Tearing of pulmonary valve tissue and avulsion of pulmonary cusps were not seen in this series.

Adolescent↗
PubMed1987

The value of counter-current aortography in infants.

Counter-current aortograms were performed on five infants weighing from 1.6 to 2.8 kg. All had symptoms suggestive of congenital heart disease. The images obtained were all of diagnostic quality. In only one, who had anomalous origin of the subclavian artery on the side chosen for the injection, was the diagnosis not made by this technique. No complications directly attributable to the procedure occurred. Counter-current aortography is a safe and effective minimally invasive method of elucidating the anatomy of the aortic arch in young infants.

Aortic Coarctation↗
PubMed1987

Doppler echocardiographic evaluation of the normal human fetal heart.

Pulsed wave Doppler estimates of blood flow velocity were made across the mitral, tricuspid, aortic, and pulmonary valves in a series of 120 normal fetuses (gestational age 16-36 weeks). In 36 of these the data were obtained in all four sites. The maximum and mean velocities were calculated for each valve and these values were plotted against gestational age. There was little change in these values throughout pregnancy. The orifice dimensions of the valves were measured by cross sectional echocardiography. At all ages the tricuspid orifice was larger than the mitral and the pulmonary orifice was larger than the aortic. The blood flow values for each valve were derived from the product of the mean velocity and the valve orifice dimensions. The output of the right ventricle was usually, but not always, greater than that of the left ventricle. Combined ventricular output increased from approximately 50 ml/min at 18 weeks to 1200 ml/min at term. Despite limitations in the accuracy of the technique these results form a useful basis for the analysis of blood flow in the normal fetus and for the interpretation of abnormal Doppler findings in prenatal life.

Aortic Valve↗
PubMed1986

Radionuclide measurement of right ventricular function in atrial septal defect, ventricular septal defect and complete transposition of the great arteries.

Right ventricular (RV) function was assessed in 80 patients with congenital heart disease by first-pass and gated equilibrium radionuclide angiography. In 30 patients with a ventricular septal defect (VSD) the mean RV ejection fraction (+/- standard deviation) was 64 +/- 7%. In 30 patients with a secundum atrial septal defect it was 61 +/- 9% and in 20 patients with surgically corrected complete transposition of the great arteries it was 49 +/- 13%. These values are in close agreement with values established with cineangiography for similar groups of patients. The mean ejection fraction in the group with transposition of the great arteries was significantly less than in the group with VSD (p less than 0.001). Phase analysis of the equilibrium studies showed that there was delayed RV contraction in many patients in the absence of conduction abnormalities. This delay was significantly greater in patients with atrial septal defect than in those with VSD (p less than 0.05). There was a strong correlation between size of left-to-right shunt and phase delay in patients with VSD (r = -0.72). Thus, first-pass gated radionuclide angiography provides a valid measurement of RV ejection fraction, and delayed RV contraction on phase analysis may be a sensitive index of early RV dysfunction.

Adolescent↗
PubMed1986

Balloon aortoplasty for recoarctation following the subclavian flap operation.

Transluminal balloon aortoplasty was successfully performed 7 times in 5 children between 3 and 14 months of age who had had the subclavian flap operation for coarctation of the aorta in the neonatal period. In two the balloon aortoplasty was performed twice. All recoarctations presented with upper limp hypertension and marked upper to lower limb pressure gradients. The pressure gradient decreased immediately after the procedure from 57.1 +/- 13.8 mm Hg to 17.9 +/- 15.5 mm Hg, P less than 0.001. The diameter of the recoarcted region increased from 2.67 +/- 1.0 mm to 3.85 +/- 1.23 mm, P less than 0.05. There were no complications attributable to the dilatation technique. Intermediate term success was unpredictable from the initial results or the angiographic appearance of the recoarctation. Follow-up has been for an average of 12.7 months (range 2-30 months). Four patients have pressure gradients from upper to lower limbs of 20 mm Hg or less. In one this has been achieved by repeat balloon aortoplasty. Severe restenosis has occurred in one other patient despite repeating the angioplasty. The procedure is safe and although intermediate term success cannot be predicted in all cases, we propose that balloon aortoplasty be the initial treatment of choice for recoarctation of the aorta. The place of repeating the procedure when early restenosis occurs has yet to be defined.

Angioplasty, Balloon↗