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Biomedical subjects

M Dick

Publications and source records attributed to M Dick.

At least 145 records · Page 8Linked to original sources
PubMed1981

Electrophysiologic delineation of the intraventricular His bundle in two patients with endocardial cushion type of ventricular septal defect.

Two patients who had an endocardial cushion type of ventricular septal defect underwent electrophysiologic studies for detection of specialized conduction tissue during operative repair. In one patient, with an inferior leftward frontal plane QRS axis on the ECG, we recorded an intraventricular His bundle electrograms from both the anterosuperior and posteroinferior margins of the defect, suggesting dual atrioventricular conduction tracts (branching intraventricular His bundle). These anatomic and electrophysiologic findings may account for the more normally oriented QRS frontal plane axis on the surface ECG of both of these patients and support the hypothesis that the changes observed on the ECGs of patients with the various forms of endocardial cushion defect can be explained by alterations in the anatomic configuration of the specialized atrioventricular conduction tissue.

Bundle of His↗
PubMed1981

Quantitative morphometric analysis of the pulmonary arteries in two patients with D-transposition of the great arteries and persistence of the fetal circulation.

Quantitative morphometric studies were performed on the pulmonary arteries of two newborns who died at 1 and 3 days of age with both transposition of the great arteries and persistence of the fetal circulation. Similar studies were performed on two normal control subjects (age 2 and 6 days), one newborn infant (age 1 day) with secondary persistence of the fetal circulation, and one newborn infant (age 2 days) with isolated D-transposition of the great arteries, as compared to those without it. When wall thickness was related to external diameter of the vessel, the greatest difference in thickness was observed in the smallest vessels (less than 150 mu in diameter). Extension of smooth muscle peripherally and to the smallest vessels (less than 50 mu) was similarly most marked in those infants with persistence of the fetal circulation may coexist but at the same time be unrelated in a single patient. Furthermore when such coexistence is unrecognized, pharmacologic manipulation of the ductus arteriosus may be hazardous.

Female↗
PubMed1980

Distribution and inheritance of low serum thyroxine-binding globulin levels in Australian Aborigines: a new genetic variation.

Evidence is presented that low serum thyroxine-binding globulin (TBG) levels in Aborigines are widely distributed throughout Australia, and that these are inherited rather than acquired. Levels of TBG in children, and lack of any correlation of low TBG levels with alcohol consumption or liver dysfunction, suggest that the low levels are not acquired in adult life. Genetic studies in eight families indicate (with one exception) an autosomal dominant pattern of inheritance with direct male-to-male transmission. These findings are in marked contrast to the much rarer X-linked pattern of inheritance of low TBG levels in Caucasians. This type of prevalent and inherited low level of TBG in serum appears so far to be unique to the Aboriginal race. The synthesis (or degradation) of TBG may be controlled by an autosomal gene in Aborigines.

Adolescent↗
PubMed1980

Prevalent low serum thyroxine-binding globulin level in Western Australian aborigines: its effect on thyroid function tests.

The first major variation from the normal human levels of thyroxine-binding globulin (TBG) in a racial group is reported in full-blood Aborigines of Western Australia. This finding has not only biochemical and anthropological interest, but also medical significance in that many common laboratory tests of thyroid function in this group are very liable to misinterpretation because of low TBG levels. In Aborigines in the Halls Creek area of Western Australia, 40% have TBG levels below the lower reference limit for Caucasians, and 18% have levels between half and one-third of the lower limit. Such subjects have low thyroxine levels by Caucasian standards, and frequently the results of triiodothyronine uptake (T3U) tests lend support to the false suggestion of hypothyroidism. Caucasian reference ranges are not valid in this large proportion of the Aboriginal population. It is not yet clear whether the low TBG levels are a normal feature in this racial population, or whether there is some other cause. The subjects of the study were not acutely ill and Aborigines with low TBG are well distributed throughout the State.

Australia↗
PubMed1979

Intraoperative recording of specialized atrioventricular conduction tissue electrograms in 47 patients.

Intraoperative mapping of the specialized atrioventricular conduction system was performed in 47 patients during cardiac surgery. Specialized conduction tissue electrograms were identified in 37, and atrioventricular conduction preserved in 92%. Specialized conduction tissue was identified in 27 patients with atrioventricular canal defect: complete heart block was avoided in 25. Conduction tissue was located in six of 12 patients with complex transpositions; atrioventricular conduction was preserved in all six. Other lesions in which the technique was useful were Ebstein's anomaly and single atrium. Limitations to the technique are 1) deep hypothermia and circulatory arrest; 2) interruption in atrioventricular conduction during mapping; 3) inadequate exposure and access to probable sites of conduction tissue; 4) variation of size and spatial relations of individual malformations; and 5) limited time for identification of unusually located conduction tissue. Indications for use of this technique include patients with both forms of atrioventricular canal, complex transpositions, atrioventricular discordance, single ventricle and single atrium.

Adolescent↗
PubMed1978

His bundle electrogram after intracardiac repair of tetralogy of Fallot. Analysis of data in 59 patients.

His bundle electrograms were recorded in 59 patients after intracardiac repair of tetralogy of Fallot and were correlated with the postoperative electrocardiogram. Except for five patients with first degree atrioventricular block postoperatively all patients in Group A (those with either a normal electrocardiogram or solitary right bundle branch block) had a normal A-H interval (77.7 +/- 21.6 msec) (mean +/- standard deviation); all had a normal H-V interval (39.5 +/- 7.2 msec). Patients in Group B (bifascicular block) tended to have a normal A-H interval (97.2 +/- 26.2 msec) with a prolonged H-V interval (48.8 +/- 10.7 msec). Patients in Group C (trifascicular block) had prolongation of both the A-H (160.0 +/- 32.4 msec) and the H-V interval (58.8 +/- 10.6 msec) by comparison with control values. Patients in Group D (transient complete heart block) had a normal A-H interval (79.5 +/- 28.2 msec) but a prolonged H-V interval (57.8 +/- 16.4 msec), similar to that in Group C. A good hemodynamic result was associated with a normal H-V interval; a prolonged interval accompanied a poor result.

Adolescent↗
PubMed1978

Early and late results with the Mustard operation in infancy.

Eighty-one patients, ranging in age from 36 hours to 24 months and in weight from 2.5 to 12 kg had a Mustard operation for D-transposition of the great arteries (D-TGA) (20 with complex D-TGA) using either deep hypothermic circulatory arrest (68 patients) or conventional cardiopulmonary bypass (13 patients). A Dacron patch was used for the intraatrial baffle and pericardium for augmentation of the pulmonary atrium. Ten patients died following operation. Thirty-two patients had cardiac catheterization 1 year after operation. Of 24 patients with D-TGA and intact ventricular septum, 23 had normal pulmonary artery pressures. In 20 patients left ventricular outflow tract gradients decreased from a mean of 32 mm Hg to a mean of 18 mm Hg after operation. Five patients who had D-TGA and ventricular septal defect and systemic pressures in the left ventricle before operation, had a notable decrease in left ventricular pressures after the procedure. Seven patients required reoperation for baffle obstruction. Mortality following Mustard repair was primarily related to the complexity of the lesion, maturity of the infant, and degree of pulmonary vascular changes. Caval obstruction was related to the configuration of the baffle used in the early part of this series.

Blood Pressure↗
PubMed1978

An improved screening method for 3-methoxy-4-hydroxy mandelic acid excretion in urine.

A screening method is described for urinary 3-methoxy-4-hydroxy mandelic acid using an initial ion exchange procedure, vanillin formation and extraction into toluene. The technique, is simple, rapid and specific, with a reference value up to 35 mumol (7.0 mg)/day established on 92 normal human subjects. Over 200 patients' urines were analysed by the method of which 18 gave values above the reference range. The majority of these increased excretions are attributed to the metabolic effects of drugs, one patient suffered from phaeochromocytoma and only 2 results remaining unexplained.

Chromatography, Ion Exchange↗
PubMed1977

Electrophysiologic delineation of the specialized atrioventricular conduction system in two patients with corrected transposition of the great arteries in situs inversus (I,D,D).

Electrophysiologic delineation of the atrioventricular conduction system at surgery is described in two patients with corrected transpostion of the great arteries in situs inversus. Intra-atrial electrograms were recorded in one patient from sites immediately adjacent to the coronary sinus located in the left-sided right atrium. The intraventricular portion of the atrioventricular conduction system was identified in both patients along the posterior and inferior margin of the ventricular septal defect, in contrast to the superior and anterior location found in corrected transposition of the great arteries in situs solitus. In contrast to the superior and anterior location found in corrected transposition of the great arteries in situs solitus. The course of the conduction system in the hearts of these two patients and a possible relationship to the cardiac loop and dual origin of the atrioventricular node is discussed. These cases illustrate the usefulness of segmental diagnosis of congenital heart disease and of electrophysiologic identification of the specialized atrioventricular conduction system at surgery.

Adolescent↗
PubMed1976

Interrupted aortic arch in infancy.

Data from 30 infants with interrupted aortic arch in the New England Regional Infant Cardiac Program, 1968 to 1974, were reviewed. All patients had major associated cardiac abnormalities: approximately one third had ventricular septal defect with patent ductus arteriosus, one third had complex ventricular septal defect with left ventricular outflow obstruction, and one third had complex intracardiac lesions incompatible with survival. Twenty-one of the patients had either palliative or reconstructive surgery, with a hospital mortality rate of 76%. Nine patients did not have surgery; eight of them died at a median age of four days. One-stage primary repair of interrupted aortic arch including the associated cardiac defects, using deep hypothermia and circulatory arrest, is proposed as the current method of treatment in such infants.

Aorta↗
PubMed1976

Intraoperative recording of the His bundle electrogram in man. An assessment of its precision.

To estimate the effect of distance between the electrode and the signal source on the amplitude of the His bundle electrogram (HBE) recorded during open heart surgery, a specially designed probe, containing six pairs of closely spaced (1 mm) electrodes was placed on the endocardial surface of the right atrium such that each electrode pair was parallel to the course of the His bundle. The amplitude of the HBE recorded through electrodes closest to the His bundle ranged from 0.76 to 2.44 mV, at 1mm from 0.38 to 1.13 mV, at 2mm from 0.27 to 0.86 mV, and at 3 mm from 0.2 to 0.44 mV. Maximal amplitude of HBE decreased by 57% at 1mm, 73% at 2 mm, and 82% at 3mm. The percent decrease was initially rapid, then declined more slowly at distances greater than 1 mm, resembling in form data obtained previously in animal studies by different techniques. Since the maximum HBE was greater than 1.0 mV in nine of 11 patients, and equal to or greater than 1.0 mV in only two of 11 patients at 1 mm, and less than 1.0 mV in all patients 2.0 mm from the maximal HBE, the anatomic location of the His bundle can be estimated from HBE amplitude. Intracardiac electrograms, recorded through closely spaced bipolar electrodes during open heart surgery, afford clinically useful precision in locating the specialized conduction tissue of the heart.

Adolescent↗
PubMed1976

The palliative Mustard operation for double outlet right ventricle or transposition of the great arteries associated with ventricular septal defect, pulmonary arterial hypertension, and pulmonary vascular obstructive disease. A report of eight patients.

Five patients with double outlet right ventricle, ventricular septal defect, pulmonary arterial hypertension and pulmonary vascular obstructive disease and three patients with complete d-transposition of the great arteries, ventricular septal defect, pulonary arterial hypertension and pulmonary vascular obstructive disease underwent an elective Mustard baffle operation. The ventricular septal defect was not closed. A large patent ductus arteriosus was divided in three patients. Seven of the eight patients are alive five to 32 months after surgery; one patient died 11 months after surgery. Cyanosis, dyspnea on exertion, and exercise limitation improved initially in all and has persisted in the survivors. In pre and postoperative hemodynamic studies in four patients, systemic arterial oxygen saturation and effective pulmonary blood flow increased from mean values of 70% to 90% and 1.7/min/m2 to 3.3 L/mon/m2, respectively. Absolute systemic and pulmonary flows, and pressures and resistances, were not significantly altered. Criteria for selection of patients with transposition of the great arteries of double outlet right ventricle who would benefit from a palliative Mustard procedure (Mustard atrial baffle without closure of the ventricular spetal defect) are: 1) severe symptoms; 2) pulmonary arteiral hypertension (75% systemic) with pulmonary vascular obstructive disease; and 3) pulmonary artieral oxygen saturation greater than systemic (ascending aorta) arterial oxygen saturation by approximately 10%.

Adolescent↗