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Biomedical subjects

M Tynan

Publications and source records attributed to M Tynan.

At least 109 records · Page 6Linked to original sources
PubMed1982

M-mode echocardiography in the developing human fetus.

The M-mode echocardiogram can be obtained in the developing human fetus from around the 16th week of gestation until term. Errors in interpretation of the M-mode echocardiogram can be avoided by concurrent two dimensional fetal cardiac examination. The pattern of motion of the mitral, tricuspid, aortic, and pulmonary valves and ventricular wall motion can be studied. Motion of the foramen ovale flap, which is characteristic in fetal life, can also be observed. Using the M-mode tracing, measurement data for six variables were made and growth charts constructed. The variables recorded were septal and left ventricular wall thickness, right and left ventricular internal dimension in diastole, aortic root dimension, and left atrial internal dimension. The measurements were made in normal pregnancies where the fetal heart was structurally normal. Confidence limits for each measurement were derived for gestational ages between 16 and 39 weeks.

Aorta↗
PubMed1981

Normal fetal cardiac anatomy--a basis for the echocardiographic detection of abnormalities.

Real-time examination of the fetal heart in 350 pregnancies has allowed a composite picture of normal fetal cardiac anatomy to be established and echocardiographic interpretation has been confirmed by anatomical studies. Two echocardiographic sections are readily obtainable and are suggested as applicable to routine scanning but the specialist nature of interpreting abnormalities is stressed. Six abnormalities have been suspected during the study and five confirmed anatomically or at cardiac catheterization. In view of the low incidence of congenital heart disease in a normal obstetric population, high risk groups should perhaps be selected for cardiac scanning at the present time. These include mothers of previously affected babies, diabetic mothers and certain abnormalities of pregnancy. Fetal ascites is particularly important, being present in three of four proven cases of cardiac abnormality.

Ascites↗
PubMed1981

Identification of congenital cardiac malformations by echocardiography in midtrimester fetus.

Fetal echocardiograms were performed in 21 pregnancies before midtrimester termination. All fetal heart specimens were collected and studied morphologically. Eighteen had been diagnosed as normal echocardiographically and this was confirmed anatomically. Deficiency of the atrial septum was suspected in one, and primum and secundum atrial septal defects were found anatomically. Coarctation of the aorta was suspected in another and this was confirmed anatomically. A ventricular septal defect was suspected in one which proved to be normal on dissection.

Echocardiography↗
PubMed1980

New intervention in mitral valve prolapse. Use of cold pressor test during echocardiography.

A study was performed in 13 patients with idiopathic mitral valve prolapse and in 21 control subjects to assess the effect of the cold pressor test on systolic motion of the mitral valve. A significant increase in blood pressure occurred in 10 patients with mitral valve prolapse and in 19 controls after immersion of one hand in ice-cold water. M-mode echocardiographic recordings from the mitral valve were obtained in all patients before, during, and after the cold pressor test, together with simultaneous phonocardiograms in selected patients. Nine out of 10 patients with mitral valve prolapse and a hypertensive response to the cold stimulus showed a significant increase in the depth of mitral valve prolapse during the cold pressor test whereas in three patients with mitral valve prolapse and no hypertensive response the depth of mitral valve prolapse did not change during cold stimulation. Three patients with previously demonstrated mitral valve prolapse had equivocal resting echocardiograms but developed diagnostic evidence of mitral valve prolapse during the cold pressor test. No evidence of mitral valve prolapse was seen in any of the control subjects before, during or after the cold pressor test. In four patients with mitral valve prolapse and a hypertensive response to cold stimulation the systolic click was delayed by the cold pressor test, whereas the time of the systolic click remained constant in the three patients whose blood pressure did not increase. It is concluded that the cold pressor test provides a stimulus sufficient to delay the onset and increase the depth of mitral valve prolapse, thereby enhancing the diagnostic sensitivity of echocardiography in this condition.

Adult↗
PubMed1979

Univentricular heart of right ventricular type with double or common inlet.

Seventeen cases are described in which both atria connect directly to a chamber with right ventricular characteristics. The atria connected through separate atrioventricular valves in six hearts and a common valve in 11. All hearts had a posterior rudimentary chamber. The septum which separated it from the main chamber was directed to the crux of the heart. Ten hearts were from patients with atrial situs solitus and seven from patients with atrial situs ambigous. Arterial connections were concordant in three cases, had a double outlet from the main ventricular chamber in nine and single outlet of the heart in five. The patent artery always arose from the main chamber, with pulmonary atresia in three and aortic atresia in two. This and other studies indicate that double inlet atrioventricular connection does not predict the morphology of the main chamber. Although usually associated with a main chamber of left ventricular type, it may also be associated with a main chamber having right ventricular characteristics. Both types should be considered as univentricular hearts; the posterior chamber in hearts of right ventricular type are analogous to the anterior chamber in univentricular hearts of left ventricular type and are a rudimentary chamber rather than a hypoplastic ventricle. In the right ventricular form of univentricular heart, the trabecular zone of the rudimentary chamber is of left ventricular type.

Abnormalities, Multiple↗
PubMed1979

Nomenclature of the univentricular heart.

A simple system for the analysis and classification of the univentricular heart is described. The basis of this approach is the use of a step by step sequential nomenclature with attention paid to the morphology, connexions and relationships of each cardiac segment in turn. Three major morphological types of univentricular heart are identified and these may be distinguished, by their characteristic trabecular patterns, into hearts of left ventricular type, right ventricular type and indeterminate type. With the exception of the last it is usual for a rudimentary second chamber to be present upon the use of a clear definition of "ventricle", depending on readily ascertainable anatomical characteristics. Each morphological type of univentricular heart may be associated with a wide variety of different connexions and intracardiac relationships and it is neither possible nor desirable to describe these in terms of a rigidly structured classification. Adherence to the simple semantic framework outlined would resolve much of the confusion and controversy which exists in relation to the univentricular heart.

Heart Septal Defects, Ventricular↗
PubMed1979

Morphology and conducting tissue in univentricular hearts of right ventricular type.

22 specimens of univentricular hearts of right ventricular type were examined morphologically. 6 hearts were sectioned for study of the conducting tissue. All the specimens had rudimentary second chambers, which were frequently so small as to have been overlooked, both angiographically and at initial morphological study. The segmental connexions and intracardiac relationships varied widely. Examples were found with 2 atrioventricular valves, a common valve and with absence of either the right or the left atrio-ventricular connexion. In some cases straddling of an atrioventricular valve was observed. The rudimentary chambers always lay posteriorly but varied between a position to the left of the ventricle and one to the right. The septum between ventricle and rudimentary chamber ran to the crux of the heart in all but 2 instances. In most specimens both great arteries arose from the ventricle (double outlet ventricle), so that the rudimentary chamber was solely a trabecular pouch. 4 hearts had concordant arterial connections with the aorta arising from a posterior "outlet" chamber. Pulmonary atresia was found in 5 cases and aortic atresia in 2. The conduction system originated from a normally placed atrioventricular node in 4 out of 6 cases and was related to the trabecular septum in 5. The penetrating bundle usually descended onto the crest of the septum at the "crux" of the heart and bifurcated astride it. In 2 cases with an absent atrioventricular connexion the penetrating bundle originated from an abnormally placed node and in one of these specimens a sling of conducting tissue was identified with dual pathways.

Atrioventricular Node↗
PubMed1979

Ventricular morphology in the univentricular heart.

The ventricle morphology is described in hearts in which the entire atrial inputs are committed to a single chamber in the ventricular mass, this being considered the criterion for definition of the univentricular heart. Such a definition does not exclude from the univentricular category hearts with two chambers in their ventricular mass providing that the second chamber does not receive a direct atrial input. Three types of ventricular morphology were identified: hearts with a main chamber of left ventricular pattern and a rudimentary chamber of right ventricular pattern; hearts with a main chamber of right ventricular pattern and a rudimentary chamber of left ventricular pattern and hearts with a sole chamber in their ventricular mass of indeterminate pattern. Hearts may also exist of right or left ventricular type without rudimentary chambers. Variation was noted in type and position of the rudimentary chambers. Chambers of either right or left ventricular type were found supporting either or both great arteries (outlet chambers), and also without a direct outlet (trabecular pouches). Right ventricular rudimentary chambers were usually anterior but could be right or left sided; left ventricular chambers were posterior but again could be right or left sided. Hearts with these ventricular morphologies possessed either double inlet atrioventricular connexions, or absence of the right or left atrioventriuclar connexion. In double inlet ventricles, cases were observed with two valves, a common valve, one imperforate valve, and with straddling atrioventricular valves. A straddling valve was also found in hearts with absence of one atrioventricular connexion. Further variation was found in the pattern of arterial connexions. It is concluded that ventricular morphology is an important feature of the iniventricular heart but must be considered in the context of other important and variable features.

Heart Septal Defects, Ventricular↗
PubMed1979

Problems in the nomenclature of the univentricular heart.

There are three main reasons why there are problems concerning the nomenclature of the univentricular heart. The first is that different authorities have used the same term to describe different varieties of the univentricular heart. The second is that many of the terms used in categorisation of these anomalies are derived from embryological concepts which are more or less speculative. The final reason, perhaps the major one, is that there is a lack of definition of a ventricle. Consequently there is no consensus as to precisely what constitutes a "univentricular" heart. Many of the heart described as "single" or "common" ventricle possess two chambers within their ventricular mass. For such hearts to be univentricular it is evident that one of these chambers cannot be a ventricle. Yet definitions have yet to be provided to distinguish ventricles from rudimentary chambers. The solutions to these problems can be produced firstly by using descriptive terms for categorisation of univentricular hearts which do not have multiple meanings. Secondly, the problems concerning usage of embryologic terms can be easily circumvented by eschewing all embryologic considerations in naming these malformations. The problem of definition of a ventricle is best solved by considering normal ventricles as possessing three portions -- an inlet portion, a trabecular portion and an outlet portion. It may then be proposed that the minimal requirements for a ventricle are that it possesses at least an inlet and a trabecular portion. Chambers without inlet portions are rudimentary chambers. Either ventricles or rudimentary chambers may possess a trabecular pattern of right or left ventricular type. Tue univentricular heart may then be categorised as composing all anomalies which have a sole chamber in their ventricular mass together with all anomalies which possess a rudimentary chamber.

Heart Septal Defects, Ventricular↗
PubMed1977

Postnatal maturation of noradrenaline uptake and release in cat papillary muscles.

Catecholamine uptake and release have been studied in isolated right ventricular papillary muscles from kittens aged less than 24 hours, 16 to 18 days and 28 to 32 days. Under the age of 24 h catecholamine uptake (uptake I) does not appear to be functioning and at this age there is a significantly lower response to tyramine. These results suggest that myocardial sympathetic innervation continues to mature, in the cat, after birth.

Animals↗
PubMed1977

Direct effect of acebutolol on force generation in immature and adult myocardium.

The effect of acebutolol on active isometric force generation has been studied in isolated papillary muscle preparations from adult cats and kittens less than 24 h old. Statistically significant reduction in active force occurred at a concentration of 0.27 mmol-litre-1 in the adult preparations and at 1.34 mmol-litre-1 in the infant ones. At 2.86 mmol-litre-1 active force had fallen to 43.4%+/-2.2 (SEM) of the control value in the adults and to 52.4%+/-3.3(SEM) in the infants. These results suggest that the infant myocardium is no more sensitive to the negative inotropic effect of acebutolol than is the adult myocardium.

Acebutolol↗
PubMed1977

Infradiaphragmatic total anomalous pulmonary venous connection to portal vein. Diagnostic implications of echocardiography.

A case of total anomalous pulmonary venous connection to the portal vein is described. The diagnosis was suspected clinically, supported by the echocardiogram, and confirmed by cardiac catheterisation, angiocardiography, and contrast echocardiography. An echo-free space lying behind the left atrium initially was thought to represent the common pulmonary vein. However, contrast echocardiography showed that this space was not the anomalous vein but probably an artefact. This paper shows that the origins of intracardiac echoes cannot always be assumed from a simple comparison of echocardiography with angiocardiographic or necropsy findings. In some cases it is necessary to introduce a marker into the echocardiogram which unequivocally originates from, and, therefore, localises, the structure under examination. Contrast echocardiography provides such a marker.

Angiocardiography↗
PubMed1977

Diagnosis of ventriculo-arterial discordance (transposition of the great arteries) by contrast echocardiography.

The constant anatomical relation of the aortic arch and the pulmonary artery bifurcation permits echocardiographic differentiation of the two great arteries when viewed from the suprasternal notch. When this technique was employed with contrast echocardiography in 12 infants, 6 of whom had ventriculo-arterial discordance (transposition of the great arteries), it was possible to establish with certainty in all but 1 case which great artery was most directly connected to the systemic venous return.

Echocardiography↗
PubMed1977

Echocardiography of primitive ventricle.

The angiocardiographic, echocardiographic, and, where available, the necropsy findings were correlated in 32 cases of primitive ventricle. Single probe echocardiography was shown to be a reliable and accurate technique for diagnosis of primitive ventricle; the ventricular and atrioventricular valve appearances were characteristic, and the outlet chamber was usually recognised when present, though it was not possible to say whether it was rigt or left sided. Abnormalities of the atrioventricular valves were more accurately shown by echocardiography than by angiocardiography though the two techniques were shown to be complementary in the overall diagnostic process.

Adolescent↗
PubMed1977

Echocardiographic visualisation of the interatrial baffle after Mustard's operation.

Thirty children aged from 7 weeks to 14 years were examined by echocardiography after Mustard's operation for transposition of the great arteries. Discrete and persitent echoes were noted within the original left atrial cavity and contrast echocardiography was used to establish that these originated from the interatrial baffle. In the presence of caval channel obstruction, caused by malposition or shrinkage of the baffle, significant differences were seen in the echocardiographic appearances of the baffle, namely limitation of baffle motion, thickening, and multiplicity of the baffle echoes. These findings suggest that the technique may be of value in the postoperative assessment of patients with transposition of the great arteries.

Adolescent↗