Search PubMed⌕ Search

Biomedical subjects

D Gibson

Publications and source records attributed to D Gibson.

At least 109 records · Page 6Linked to original sources
PubMed1984

Interaction between systolic and diastolic time intervals in atrial fibrillation.

To assess determinants of left ventricular filling time at rest simultaneous phonocardiograms, M mode echocardiograms, and indirect carotid pulse traces were performed on 50 patients with atrial fibrillation. Thus the effect of random variation in RR interval in the absence of atrial contraction on the inter-relation between systolic and diastolic events could be seen. Left ventricular filling time was closely related to RR interval and affected by it to a much greater extent than ejection time, so that filling time became very short when heart rate was fast. Two mechanisms were, however, identified whereby filling time was preserved: (a) prolongation of filling during the pre-ejection period of the following cycle, so that when the RR interval was less than 400 ms all of ventricular filling frequently occurred at this time; and (b) abbreviation of the QA2 interval of the succeeding beat with reduced filling, so that mitral valve opening occurred early. Changes in the duration of isovolumic contraction or relaxation time were not involved, neither could alteration in left ventricular contractile state resulting from variation in the interval between beats be shown to affect time at rest. The striking sensitivity of left ventricular filling time to rapid heart rate in atrial fibrillation suggests that it may be a major factor limiting cardiac performance. Diastolic as well as systolic events should, therefore, be taken into account when the effects of drugs or other physiological manoeuvres are studied in these patients.

Adult↗
PubMed1984

L-glutamic acid, a possible neurotransmitter to anterior aorta of Aplysia.

The effect of L-glutamate on muscle fibers of the anterior aorta of the marine gastropod Aplysia are characterized. Iontophoretically applied L-glutamate depolarized anterior aorta muscle fibers in 14% of the applications; no response was detected in the other applications. Responses to iontophoretically applied L-glutamate desensitize rapidly and are antagonized by 2-amino-4-phosphonobutyric acid (2-APB). 2-APB also blocked excitatory junctional potentials (EJPs) in the anterior aorta. No significant response to D-glutamate was observed. These characteristics match those of L-glutamate at the arthropod neuromuscular junction. Bath-applied L-glutamate also depolarizes anterior aorta muscle fibers, by a mechanism clearly different from that of iontophoretically applied L-glutamate. Present results make L-glutamate a candidate neurotransmitter to molluscan circulatory muscles.

Animals↗
PubMed1984

Mental development of adults with Down syndrome.

Measures of cognitive, verbal, and functional performance obtained at widely separated time periods were examined for adults with Down syndrome. Comparisons of first and last test profiles for Raven Coloured Progressive Matrices, Peabody Picture Vocabulary Test, and Adaptive Functioning Index (Social Education) Test all demonstrated significant increases over a mean time span of 5 years. These increases could not be attributed to year of entry into program, history of institutionalization, or age of the individuals. The findings indicate that mental development of adults with Down syndrome continues well into the third and fourth decade of life.

Adolescent↗
PubMed1982

Independence of changes in left ventricular diastolic properties of pericardial pressure.

There has been much interest in the published reports as to the extent to which measured left ventricular diastolic properties are affected by the pericardium. In this study observations were made on 24 patients, seven days after cardiopulmonary bypass. Left ventricular dimensions were measured from echocardiographic recordings and left ventricular diastolic pressure assessed from measurements of isovolumic relaxation time. Pericardial pressure was measured directly using a small solid state transducer inserted into the pericardial space at the time of operation. Left ventricular diastolic properties were altered by either isometric handgrip or glyceryl trinitrate administration. Isometric handgrip produced an increase in cavity dimension at end-systole and diastole, with reduction in isovolumic relaxation time, suggesting an increase in left ventricular end-diastolic pressure; glyceryl trinitrate produced the reverse effect, with decreased cavity dimensions and prolongation of isovolumic relaxation time. These changes occurred in the absence of significant changes in pericardial pressure. We therefore conclude that even in the rather unusual conditions of the early postoperative period, when the sensitivity of pericardial pressure to small volume changes might be expected to be increased, substantial changes in left ventricular diastolic properties can occur without detectable alteration in pericardial pressure.

Blood Pressure↗
PubMed1981

Congenital mitral stenosis. Anatomical and functional assessment by echocardiography.

Digitised left ventricular echocardiograms were studied in nine children with congenital mitral stenosis to assess the severity of inflow obstruction. In six children the two prime indices of mitral stenosis were abnormal, with a prolonged time from minimum dimension to 20 per cent dimension change and a reduced peak dimension change during diastole. In three, however, these values did not suggest inflow obstruction, depsite significant gradients at cardiac catheterisation. Two-dimensional echocardiography was performed in 10 children with congenital mitral stenosis to determine the mitral annular size and the morphology of the valve and subvalvular apparatus. The annular size and number of papillary muscles could be assessed along with the detection of combined mitral abnormalities. Two-dimensional studies can reliably delineate the type of mitral abnormality, and should be performed in all cases with congenital heart disease having a high incidence of associated left ventricular inflow obstruction. Digitised M-mode left ventricular echocardiography is in general unreliable in assessing congenital obstruction, though it may be of some value in individual cases.

Adolescent↗
PubMed1981

Two dimensional echocardiographic categorisation of the univentricular heart. Ventricular morphology, type, and mode of atrioventricular connection.

Most univentricular hearts have two chambers in their ventricular mass, only one of which possesses an atrioventricular connection. Categorisation into univentricular heart of right, left, or indeterminate type, using two dimensional echocardiography has been successfully achieved in 122 out of 132 patients to whom this technique has been applied. Thus, right ventricular rudimentary chambers in 84 univentricular hearts of left ventricular type were shown to be anterosuperior and either to the right or left. In contrast, left ventricular rudimentary chambers in 25 univentricular hearts of right ventricular type were posteroinferior and to the right, left, or directly posterior. Thirteen univentricular hearts of indeterminate morphology were characterised by absence of rudimentary chamber on angiography and echocardiography. The trabecular pattern of both main and rudimentary chambers were separately identified in some of the patients with univentricular hearts of right and left ventricular type and two dimensional echocardiography also illustrated the mode of atrioventricular connection, either via two atrioventricular valves, a common valve, or a valve straddling or overriding the trabecular septum. Finally it was also possible to distinguish absent atrioventricular connection from an imperforate valve in 10 patients.

Echocardiography↗
PubMed1980

Heparin necrosis. An anticoagulation syndrome.

Lesions indistinguishable from coumarin necrosis developed in three patients who were given heparin sodium subcutaneously. Two of the patients had received only heparin while another had also received coumarin. Heparin necrosis should be added to the list of complications of anticoagulation therapy.

Aged↗
PubMed1980

Lateralized hand gesture during speech.

A group of individuals conversing in natural dyads and a group of lecturers were observed for lateral hand movement patterns during speech. Right-handed individuals in both groups displayed a significant right hand bias for gesture movements but no lateral bias for self-touching movements. The study provides external validity for previous laboratory studies of lateralized hand gesture. The results were interpreted as evidence of a central processor for both spoken and gestural communication.

Journal Article↗
PubMed1979

Mechanisms of prolongation of pre-ejection period in patients with left ventricular disease.

In order to determine the mechanism underlying prolongation of the pre-ejection period in patients with left ventricular disease, 11 patients with congestive cardiomyopathy and 29 with coronary artery disease, 10 of whom were taking beta-adrenergic blocking drugs, were studied non-invasively. Recordings of carotid pulse, and apex, phono-, and echocardiogram were obtained. In the absence of treatment with beta-blocking drugs, prolongation of pre-ejection period correlated closely with incoordinate left ventricular wall movement during isovolumic contraction assessed from simultaneous apex and echocardiograms. There was no correlation between pre-ejection period index (PEPI) and end-diastolic dimension and PEPI correlated poorly with fractional shortening and peak Vcf. A PEPI of greater than 140 ms was associated with incoordinate contraction in all but one case, and of less than 140 ms with normal contraction in all. Therapeutic doses of beta-blocking drugs caused prolongation of PEPI to a greater extent than would have been predicted from wall movement during isovolumic contraction. Incoordinate left ventricular contraction and a negative inotropic effect both therefore prolong PEPI, but by different mechanisms, whose effects can be separated in individual patients using non-invasive methods based on echocardiography.

Adrenergic beta-Antagonists↗
PubMed1979

The chronicity of symptoms and disability in Reiter's syndrome. An analysis of 131 consecutive patients.

To assess the natural history of Reiter's disease, we evaluated 131 consecutive patients at a university clinic or at a community center. One hundred twenty-two patients (93%) were available for follow-up at a mean of 5.6 years. The results showed that there were no major differences between patients at the two centers; at follow-up, 101 (83%) had some disease activity, 27 (22%) had annoying symptoms, 42 (34%) had sustained disease activity, 19 (16%) had had to change jobs, and 13 (11%) were unemployable; there were no major differences between the 19 (15%) females and 112 (85%) males or between the HLA-B27-positive (83%) and -negative (17%) patients, except for increased prevalence of sacroilitis and chronic uveitis in HLA-B27-positive patients; and, at entry, only increased heel disease differentiated those destined to have a poor prognosis. Most patients with Reiter's syndrome have persisting symptoms that can lead to chronic disability.

Adult↗
PubMed1978

The use of arterial--central venous oxygen differences to calculate cardiac output and oxygen consumption in critically ill surgical patients.

Simultaneous determinations of cardiac output (using the cardiogreen indicator dilution technique) and arterial--central venous oxygen differences [C(a-cv)O2] were obtained in 200 critically ill surgical patients. The average initial values +/- SD included arterial--central venous oxygen differences of 3.6 +/- 1.6 vol%, cardiac index of 3.4 "/- 1.2 liter/min/sq m, and oxygen consumption of 100 ml/min/sqm. As might be expected, low arterial--central venous oxygen differences, especially if less than 2.0 vol%, were associated with high cardiac indices, but the oxygen consumptions were much lower than normal and the mortality rates were increased. The cardiac indices calculated from the C(a-cv)O2 averaged 4.1 liter/min/sq m and correlated rather well with the measured cardiac indices, particularly if the patients with a C(a-cv)O2 of less than 2.0 vol% were excluded. Arterial pH values did not correlate well with the calculated oxygen consumption. Arterial oxygen contents of more than 16.2 vol% equivalent to a hemoglobin of 12.5 gm/dl or higher with an oxygen saturation of 95%, provided better arteriovenous oxygen differences, oxygen consumptions, and survival rates than those found with lower hemoglobin values. Arterial--central venous oxygen differences and calculated oxygen consumptions can be practical clinical and prognostic value.

Arteries↗