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Biomedical subjects

H Edwards

Publications and source records attributed to H Edwards.

At least 55 records · Page 3Linked to original sources
PubMed1982

Area variations in infant mortality 1975-7.

Infant mortality rates vary from area to area. Part of this variation is due to the socioeconomic characteristics of the area and part to other factors including the obstetric, paediatric, and community health services. Four social indicators associated with infant deaths are used to control for some of the variations in socioeconomic characteristics and residual variation is then examined. The four social indicators are the level of unemployment, the proportion of large families, the proportion of lone-parent families, and the level of overcrowding.

Crowding↗
PubMed1982

Benefits of normothermic induction of blood cardioplegia in energy-depleted hearts, with maintenance of arrest by multidose cold blood cardioplegic infusions.

This study tests the hypothesis that warm induction of cardioplegia prior to prolonged maintenance by multidose infusions of cold blood cardioplegic solution would increase the tolerance of energy-depleted hearts to subsequent aortic clamping. Eighty percent depletion of subendocardial adenosine triphosphate (ATP) was produced in 30 dogs by 45 minutes of normothermic ischemia. This was followed either by unmodified blood reperfusion or 2 additional hours of aortic clamping with multidose cold blood cardioplegia. We compared a brief (5 minute) period of 37 degrees C cardioplegic induction to standard 4 degrees C blood cardioplegic induction to determine if warm induction would enhance metabolic and functional recovery. Warm cardioplegic induction resulted in more oxygen consumption than cold induction (16.9 versus 8.1 cc/100 gm), and lower levels of glucose-6-phosphate (G6P), suggesting better aerobic metabolism (0.97 versus 1.87 microM/gm wet weight). Prompt repletion of creatine phosphate (CP) occurred with warm and cold cardioplegic induction, although ATP levels levels remained low. Hearts undergoing ischemia and unmodified reperfusion consumed insufficient oxygen to meet basal metabolic needs during reperfusion (7 cc/100 gm below requirement) and recovered only 33% +/- 5% of control left ventricular performance. Better function occurred with cold cardioplegic induction (63% +/- 5%), and almost complete recovery (85% +/- 5%) occurred when warm induction of cardioplegia was used. We conclude that warm induction followed by prolonged cold multidose blood cardioplegic arrest enhances aerobic metabolism, results in normal left ventricular performance, and improves tolerance of aortic clamping in energy-depleted hearts.

Adenosine Triphosphate↗
PubMed1981

Postoperative deterioration in psychomotor function.

To help understand the postoperative fatigue state, psychomotor performance before and after surgical procedures or bed rest has been analyzed. Forty subjects in three groups were studied during test periods ranging from five to 21 days. Patients undergoing routine elective operations as well as subjects at bed rest alone experienced substantial impairment in several measures of psychomotor performance. Maximum deterioration was noted on postoperative days 4 and 5.

Bed Rest↗
PubMed1981

Effect of cimetidine on serum calcium levels in an elderly patient.

A 92-year-old woman with a normal serum calcium level received cimetidine postoperatively. She became severely hypocalcemic and exhibited tetany, seizures, and impaired mental status. Her condition responded to intravenous diazepam, phenytoin sodium, and gluconate calcium. Normal serum calcium levels were maintained by calcium infusions until the cimetidine treatment was stopped. Cimetidine may have been responsible for the observed complications due to its effect on serum parathyroid hormone level.

Aged↗
PubMed1981

Dynamic electrocardiography V. The "imaginary cardiac vector" hypothesis: experimental evaluation.

This paper experimentally evaluates the "imaginary cardiac vector" hypothesis, that the cardiac vector is not a real vector. We have previously shown on theoretical grounds that the basis of the cardiac vector is invalid in that Einthoven used scalar, not vector, procedures. Attempts by subsequent workers to compensate for the theoretical flaws have not succeeded. The concept of the "cardiac vector" which they have invented has the dimensions of an imaginary entity. Experimental measurement of isopotential maps derived from dipoles in a volume conductor demonstrates that these dipoles do not summate vectorially. Isopotential maps of the thoracic surface confirm that this applies to the human ECG. An imaginary "man-frog" cardiac vector loop is demonstrated using a lead from a man and a lead from a frog. This illustrates that the "imaginary cardiac vector" is a tenable concept. Finally, a crucial test of the hypothesis is reported which demonstrates that exercise causes deviations of the so-called cardiac vector in opposite directions, simultaneously, in different VCG lead systems. Since a physical entity can only be in one place and more in one direction at a particular instant, this experiment invalidates the "real cardiac vector" hypothesis. This strongly suggests that the cardiac vector is a brilliant, but imaginary, construction with immense clinical value, especially in the interpretation of the sequence of depolarization. Nevertheless, it obstructs analysis of the real basis of the electricity of the heart.

Animals↗
PubMed1981

Dynamic electrocardiography. III. The "imaginary cardiac vector" hypothesis: theoretical basis.

The "imaginary cardiac vector" hypothesis states that the "cardiac vector" is not a "real" vector entity. The hypothesis arises from the fact that voltage is not a vector but a scalar quantity. Nevertheless, in classical electrocardiographic analysis and teaching, the ECG voltage is treated as a vector. These voltages are used as "vector" components--first, to calculate a "resultant manifest potential difference", represented by the "cardiac vector" arrow in electrocardiography, and second, to draw the "cardiac vector" loop in vectorcardiography. The resultant "cardiac vector" is usually considered to be a "real" vector quantity describing the electrical activity of the heart. It is also widely believed that this "vector" was first described by Einthoven in 1913. To evaluate the hypothesis, we have utilised the actual values and methods presented by Einthoven, and demonstrated that the theoretical basis of the "cardiac vector" is false. It appears that Einthoven followed scalar and not vector procedures and that he did not describe a vector.

Electrocardiography↗
PubMed1981

Dobutamine in the rejecting transplanted heart.

Dopamine is commonly used to improve cardiac output and to maintain peripheral perfusion after myocardial injury. It has several advantages over other catecholamines. At effective inotropic dose levels, dopamine produces less peripheral vasoconstriction than norepinephrine. Dopamine also causes fewer arrhythmias than isoproterenol. This is a case report of a heart transplant patient who began rejecting and developed heart failure. In addition to the immunosuppressive agents, dopamine was used initially as the vasopressor with marked deterioration in the patient's condition. Dobutamine, a new inotropic agent, was substituted for dopamine with subsequent improvement in cardiac function. The authors concluded that dobutamine may be the most appropriate agent to use in the rejecting transplanted heart because of the former's direct action on the heart. Dobutamine may also be preferred for support of the cardiac outputs of patients with chronic heart failure.

Cardiotonic Agents↗
PubMed1979

Dynamic electrocardiography. II. A crucial test of the electromechanical QRS wave theory.

The dynamic electromechanical electrocardiogram hypothesis, that QRS voltage fluctuations can be used as a simple noninvasive transducer of cardiac mechanical function, has been subjected to a crucial experiment. Under direct vision, transient modifications of the end-diastolic volume of the baboon heart were produced and photographed. Sequential obstructions to filling (by vena caval compression) and to emptying (by aortic compression), and vice versa, significantly distorted the size and shape of the heart. The instantaneous effects of these manipulations on the amplitudes of the R and S waves were evaluated in electrocardiograms recorded from electrodes glued to selected pericardial and epicardial sites. Major QRS voltage deviations occurred in the perircardial leads. Manipulations increasing the left ventricular volume increased the S wave and reduced the R wave, while those decreasing heartsize had the opposite effect. These findings refute the null hypothesis, that the electrocardiogram is not an indicator of mechanical function. No changes of the QRS waves in the epicardial lead were detected, supporting the concept that displacement relative to the recording electrode is the basis of the QRS CHANGEs due to heartsize variation. The results negate the classical concept that the electrocardiogram does not reflect cardiac mechanical function, and strongly corroborate the dynamic electromechanical electrocardiogram hypothesis.

Animals↗
PubMed1977

Skinfold thickness measurements in assessment of nutritional status of Indian and White schoolchildren.

A statistical comparison is presented between height, weight, and subscapular and triceps skinfold thickness for age of Indian and White schoolchildren. It was found that (i) although a high degree of correlation existed between height and weight for age of White children, this was not true for Indian children; (ii) for both White and Indian children of both sexes inconsistent variations occurred between both height and weight and skinfold thickness; (iii) despite extremely low heights and weights observed for Indian children, which could be interpreted as depicting chronic undernutrition, the skinfold thicknesses of the latter children were close to normal as judged by conventional standards: the subscapular skinfold thicknesses in Indian girls actually exceeded the conventionally accepted normal standard values. It is concluded that in the indirect assessment of nutritional status of Indian subjects, anthropometric variables should be used with caution. Finally, it is proposed that further anthropometric and individual energy balance studies be conducted on a cross-section of various socio-economic, age and sex groups of the Indian population in an attempt to establish the basis for the described anomalies.

Body Height↗
PubMed1975

Exercise stress testing and an electromechanical S wave of the electrocardiogram. Does the S-wave voltage change with increasing work rate?

A new view of the electrocardiogram, first proposed by Posel and arising from Craib's travelling dipole concept, predicts an electromechanical relationship between S-wave amplitude changes and cardiac mechanical function changes. In an attempt to determine whether the S-wave voltage changes with increasing work rate, 10 male subjects were tested at rest and at maximum exercise. A statistically significant increase in the S wave occurred with increased mechanical work. The theoretical prediction of an electromechanical S wave is thus validated and a request is extended to other workers to verify or refute its existence.

Electrocardiography↗
PubMed1975

Electrocardiographic measurement of cardiac function. Are the amplitude changes of the S wave indicative of changes in the size of the heart?

Preliminary tests to determine whether there is an electromechanical link between the electrocardiogram and cardiac function have been done by means of echocardiography. Three different haemodynamic manipulations which alter cardiac function, viz. nitroglycerin, intravenous digoxin and exercise-induced angina, were used. The changes in the S-wave amplitude, in selected leads, appear to be directionally related to the changes in the left ventricular enddiastolic volume. It is thus suggested that the S-wave changes may be indicative of changes in cardiac function.

Angina Pectoris↗