Biomedical subjects

M J Tynan

Publications and source records attributed to M J Tynan.

At least 19 recordsLinked to original sources

PubMed2000

Intracardiac pressures in the human fetus.

OBJECTIVE: To obtain normal values for intracardiac pressures in the human fetus. DESIGN: Intracardiac pressures were measured directly in the four chambers of the human fetal heart during clinically indicated invasive obstetric procedures. SETTING: Department of fetal medicine in a tertiary referral centre. PATIENTS: 39 fetuses between 16 and 29 weeks of gestation. RESULTS: The ventricular waveforms obtained were similar to those found in postnatal life. There was an increase in ventricular systolic and end diastolic pressures with advancing gestation. There was no difference between left and right ventricular pressures. Atrial pressures were equal and remained constant in the gestational age range studied. CONCLUSIONS: Fetal cardiovascular pressure measurements in the normal fetus assist in understanding the fetal circulation, and provide a basis for the assessment of cases of congenital heart disease that may be amenable to intrauterine treatment.

Female↗

PubMed1995

Survival after fetal aortic balloon valvoplasty.

The pre- and postnatal course of a child surviving after successful intrauterine balloon aortic valvoplasty for critical aortic stenosis is described. She is now well at 4 years of age. A clearer understanding of the hemodynamics in such cases and improved catheter technology are necessary before this is advocated as a generally applicable technique. However, the outcome in this case is promising for the future of fetal interventional procedures.

Aortic Valve Stenosis↗

PubMed1994

Heart fatty acid binding protein is a novel regulator of cardiac myocyte hypertrophy.

Heart fatty acid binding protein (H-FABP) is a 15kDa protein that mediates the passage of fatty acids from the plasma membrane to sites of lipid synthesis. We report here, for the first time, that H-FABP is a potent inducer of cardiac myocyte hypertrophy, stimulating an increase in cell surface area, protein synthesis and c-jun expression. A high affinity receptor for H-FABP has also been identified. Taken together, these data suggest that H-FABP may participate in the regulation of cardiac myocyte growth and differentiation.

Animals↗

PubMed1992

Umbilical venous pressure in nonimmune hydrops fetalis: correlation with cardiac size.

OBJECTIVES: Our objectives were to examine the relationship between umbilical venous pressure and cardiac size in nonimmune hydrops fetalis and to assess the role of cardiac failure in the pathogenesis of the disease. STUDY DESIGN: Fourteen fetuses with nonimmune hydrops fetalis were investigated in a tertiary referral unit with high-resolution ultrasonography, echocardiography, and fetal blood sampling. Fetal heart size was assessed by measurement of the cardiothoracic ratio. Umbilical venous pressure was measured at the time of fetal blood sampling with a fluid-filled system. RESULTS: The 10 fetuses with elevated umbilical venous pressures had significantly increased cardiothoracic ratios (p = 0.02). These fetuses also had ascites. Four other fetuses had normal-sized hearts, normal umbilical venous pressures, and no ascites. There was a linear relationship between cardiothoracic ratio and umbilical venous pressure (r = 0.75, p = 0.003). CONCLUSION: Measurement of umbilical venous pressure validates cardiothoracic ratio as a noninvasive assessment of cardiac function in nonimmune hydrops.

Female↗

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

Balloon dilatation of the aortic valve in the fetus: a report of two cases.

Because they had irreversible damage to the left ventricular myocardium none of 12 patients with critical aortic stenosis diagnosed prenatally survived after postnatal treatment. This experience prompted three attempts at intrauterine balloon dilatation of the aortic valve in two fetuses with this condition. On each attempt the balloon catheter was successfully delivered to the left ventricle. In the first fetus the aortic valve was not crossed and the fetus died the next day. In the second fetus the balloon was correctly positioned across the aortic valve and inflated in the valve ring. After delivery, a further balloon angioplasty was performed; this relieved the stenosis but the patient died five weeks later from persisting left ventricular dysfunction related to endocardial fibroelastosis. Balloon angioplasty is feasible in fetal life but the prognosis depends on the ability of the relief of stenosis to limit, prevent, or allow regression of left ventricular damage before delivery.

Adult↗

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

The natural history of the hypoplastic left heart syndrome.

In a fetus, examined initially at 22 weeks gestation, we identified the echocardiographic features of a dilated, hypertrophied and poorly contracting left ventricle. The presumptive diagnosis was critical aortic stenosis. Subsequent scans at 32 weeks and at term showed that the left ventricle had not grown since the first study such that the left ventricle had developed the appearance of a hypoplastic and densely echogenic chamber. Thus, in some forms of the hypoplastic left heart syndrome, the left ventricle can be of normal size or even dilated in early pregnancy. This may mean that the more subtle sign of poor left ventricular contraction could be overlooked in a routine four-chamber view obstetric scan.

Aortic Valve Stenosis↗

PubMed1988

Obstetric importance, diagnosis, and management of fetal tachycardias.

During 1980-7, 23 pregnancies of 22-38 weeks' duration were investigated for fetal tachycardia. Twelve were cases of supraventricular tachycardia, eight of atrial flutter, and three cases in which the rhythm varied between supraventricular tachycardia and atrial flutter. In 11 cases the fetus had developed non-immune fetal hydrops before referral; 12 cases were non-hydropic at referral but one of this group of fetuses became hydropic during treatment. No relation was found between the rate or type of arrhythmia and the presence or absence of intrauterine heart failure. One non-hydropic infant was delivered electively prematurely. Maternal antiarrhythmic treatment was instituted in the remaining 22 cases. Conversion of the arrhythmia was achieved with digoxin alone in five cases and with a combination of digoxin and verapamil in nine. Control of the arrhythmia was achieved in seven of the 10 non-hydropic fetuses, and all were delivered at term with no deaths. Of the 12 hydropic fetuses, control was achieved in seven. Only three of the hydropic fetuses were delivered close to term. There were two deaths, both in the hydropic group. Of the whole group, five neonates suffered severe complications of prematurity. In this series the main benefit of treatment appeared to be in prolonging gestation of those hydropic fetuses in which conversion was achieved.

Delivery, Obstetric↗

PubMed1988

Experience with flecainide for the treatment of cardiac arrhythmias in children.

We treated 22 children, aged 3 days to 16 years 6 months (median 11 years 1 month), with flecainide for a variety of arrhythmias where a Class I agent was indicated. In 16, conventional antiarrhythmic treatment had failed. Structural heart disease was present in nine. The arrhythmia was paroxysmal re-entry atrioventricular tachycardia in nine; paroxysmal atrial tachycardia, flutter or fibrillation in five; paroxysmal ventricular tachycardia in five and frequent ventricular extrasystoles (with couplets) in three. Sinus rhythm was achieved in all four children who received flecainide during tachycardia (three received intravenous flecainide, one oral). During follow-up of 3-24 months (median 12 months), arrhythmia control was obtained in 13 children (59%). Combination therapy was used in seven of these; with digoxin in four and a beta blocker in three. Flecainide doses used in this study ranged from 1-11 mg kg-1 day-1 (median 4 mg kg-1 day-1), 25-297 mg m-2 day-1 (median 113 mg m-2 day-1). The median, pre-dose flecainide concentration in those responding to therapy was 225 micrograms l-1 and in those failing to respond was 417 micrograms l-1. An arrhythmogenic effect occurred in one child.

Adolescent↗

PubMed1988

Coarctation of the aorta in prenatal life: an echocardiographic, anatomical, and functional study.

In a prospective echocardiographic study of over 2000 pregnancies, 24 fetuses were found to have dilatation of the right ventricle and pulmonary artery when these structures were compared with those of the left heart. In 18 of these cases the diagnosis of coarctation or interruption of the aorta was correctly inferred from these findings. On direct echocardiographic examination of the aortic arch, arch hypoplasia or interruption of the aortic arch was recognisable prenatally in 10 of these 18 cases, most readily between 20-30 weeks' gestation. In 11 of 12 cases of aortic arch anomaly studied by Doppler echocardiography, a reduction in blood flow in the ascending aorta was demonstrated. The intracardiac appearances were suggestive of coarctation but the Doppler findings were within normal limits in two further cases which later proved to be normal. A diaphragmatic hernia was found in four fetuses and the intracardiac echocardiography and Doppler findings were the same as those found in fetuses with aortic coarctation. Five cases of coarctation were overlooked on the prenatal echocardiogram but these were found at follow up of the infants. Thus coarctation of the aorta can be diagnosed prenatally, although the condition may be missed or incorrectly predicted by the criteria examined in the present study. Reduced aortic blood flow is a demonstrable feature of aortic arch abnormalities but it is found in other conditions that are not associated with coarctation.

Aorta↗

PubMed1988

Fetal complete heart block.

In a series of over 6000 patients referred for fetal echocardiography during an eight year period, 37 fetuses were found to have complete heart block. There were 16 cases of isolated heart block and 21 cases associated with structural heart disease. All mothers of fetuses with isolated complete heart block had evidence of circulating syndrome Sjögren A antibody (Ro). Only one mother had clinical evidence of connective tissue disease. In the 21 cases associated with structural heart disease there were 17 cases of atrioventricular septal defect, one case of secundum atrial and perimembranous ventricular septal defects, two cases of tetralogy of Fallot, and one case of pulmonary stenosis. All fetuses with atrioventricular septal defects and complete heart block had left atrial isomerism. Additional abnormalities of the great arteries were often found in this group; these were double outlet right ventricle, transposition of the great arteries, pulmonary atresia, coarctation of aorta, and stenosis of the pulmonary or aortic valves. Intrauterine congestive heart failure was a feature of four cases in the group with isolated complete heart block and 11 cases of the group with associated structural heart disease. The outcome in the fetuses with isolated complete heart block was better than in those with heart disease: 12 of the 16 fetuses are alive, two of them have a pacemaker. But only three of the group of 21 fetuses with cardiac malformation are alive, and two of them have a pacemaker.

Echocardiography↗

PubMed1986

Familial recurrence of congenital heart disease in a prospective series of mothers referred for fetal echocardiography.

Fetal echocardiography can ascertain, at an early stage in pregnancy, recurrences of congenital heart disease (CHD) in mothers with a family history of CHD. In 1,021 mothers referred for this reason, 20 recurrences were found; 17 occurred when there had been 1 previously affected child, and 3 when there had been 2 previously affected children. No recurrences were found in the 41 cases in which a parent had CHD. The overall recurrence rate was 1 in 52 with a previously affected child and 1 in 10 with 2 previously affected children. However, certain forms of CHD recurred much more frequently than others. Aortic valve atresia was associated with a recurrence rate of 1 in 28, coarctation of the aorta at a rate of 1 in 15, complex CHD at a rate of 1 in 11 and truncus arteriosus at 1 in 13. These findings are inconsistent with previous family studies; this may be due to more complete ascertainment, particularly of major lesions, possibly overlooked by postnatal family studies because of fetal loss. Alternatively, the availability of prenatal diagnosis may be producing an increase in family size after major CHD. The results support current doubts on the polygenic theory of inheritance for all forms of CHD.

Aortic Coarctation↗

PubMed1986

Prenatal screening for congenital heart disease.

Routine ultrasound examination of the fetus is already established in most obstetric units in Britain. A simple method was devised to evaluate one section of the fetal heart systematically. Examination of this section, the four chamber view, may readily be incorporated into routine obstetric screening. Severe cardiac abnormalities detectable in this view occur in two per 1000 pregnancies. For six years the department of paediatric cardiology at Guy's Hospital, London, served as a referral centre for fetal echocardiography. As teaching became more widespread an increasing proportion of cases of cardiac anomaly were referred because the obstetrician suspected abnormality on examination of the four chamber view. Currently 80% of detected abnormalities are referred for this reason. Further extension and organisation of teaching might result in most severe cardiac malformations being detected in early prenatal life.

Female↗

PubMed1986

Pulmonary atresia in prenatal life.

Seven cases of pulmonary atresia with intact ventricular septum were detected in prenatal life. In two of these cases, there was a small hypertrophied right ventricle of the type commonly seen postnatally. In the remaining five cases, the right atrium and right ventricle were grossly dilated to a degree that caused lung compression. The resulting impairment of lung development appeared to be an important factor contributing to death in all five cases. Decompression of the right ventricle by intrauterine surgery to allow normal lung development in the last weeks of pregnancy may be the only way of changing this outcome.

Cardiomegaly↗

PubMed1986

Intravenous and oral amiodarone for arrhythmias in children.

Oral amiodarone was administered to 30 children (aged one week to 14 years) for treatment of resistant or life threatening tachycardias. Five children received initial intravenous medication. The mean duration of oral treatment ranged from two weeks to 64 months (mean 23 months). Infants required a higher oral dose than older children when this was calculated on the basis of body weight but not when it was calculated on the basis of body surface area, indicating that the prescribed dose of amiodarone for infants should be calculated on the basis of body surface area. Although plasma concentrations of amiodarone were similar in infants and children, the plasma concentration of the metabolite desethylamiodarone was lower in infants. The arrhythmias were effectively controlled, by amiodarone alone in 19 and by amiodarone in combination with other drugs in nine children; amiodarone was ineffective in the remaining two children. Unwanted effects were common but were not significantly related to the dose, duration of treatment, or plasma concentration of amiodarone when group results were analysed. Grey facial skin pigmentation developed in two patients who received high cumulative doses of amiodarone and in whom plasma concentrations of amiodarone were high. Four children with biochemical hepatic dysfunction had high plasma concentrations of amiodarone and a further four children who experienced sleep disturbance had required high doses of amiodarone.

Administration, Oral↗

PubMed1985

First-pass measurement of left ventricular function in infants and children.

The left ventricular ejection fraction was measured in 57 infants and children with congenital heart disease by both first-pass radionuclide angiography and left ventricular cineangiography. The correlation coefficient for the two sets of measurements was 0.79. In subgroups without left to right shunts (n = 21) and with left to right shunts (n = 36) it was 0.93 and 0.37, respectively. It is concluded that measurement of the left ventricular ejection fraction by the first-pass method is valid in children, provided there is no left-to-right shunt.

Adolescent↗

PubMed1985

Superiority of radionuclide over oximetric measurement of left to right shunts.

In 100 children with suspected left to right shunts the ratio of pulmonary to systemic flow was measured both by oximetry and first pass radionuclide angiography. The pulmonary time activity curve from the radionuclide study was analysed by the method of gamma variate fits. There was strong correlation between the two techniques; weaker correlation was found when the shunt was at atrial rather than ventricular level. This difference can be explained only by problems with the oximetric rather than the radionuclide technique. Although there are important limitations to the radionuclide method, it is the more precise and less invasive of the two and is to be preferred when the accurate measurement of left to right shunts is required.

Adolescent↗