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Biomedical subjects

D G Gibson

Publications and source records attributed to D G Gibson.

At least 217 records · Page 12Linked to original sources
PubMed1976

Echocardiographic assessment of abnormal left ventricular relaxation in man.

In 64 patients requiring cardiac catheterization for chest pain, echocardiograms showing anterior mitral leaflet and left ventricular cavity simultaneously were recorded. These were digitized and their first derivatives computed in order to study time relations between mitral valve and left ventricular wall movement in early distole. In 10 patients with normal left ventricular angiograms and coronary arteriograms, mitral valve opening began 1-1 +/- 9-3 ms (mean +/- SD) before the onset of outward wall movement, and reached peak opening velocity 2-0 +/- 13 ms after maximum rate of change of dimension. Virtually identical time relations were seen in 15 patients with normal left ventricular angiograms but with obstructive coronary artery disease (3-6 +/- 9-3 ms and 0-7 +/- 7-3 ms, respectively). These close relations were lost in patients with segmental abnormalities of contraction on left ventricular angiogram. In 19 such patients with normal septal motion, outward wall movement began 53 +/- 31 ms before the onset of anterior movement of the mitral valve leaflet, and this isovolumic wall movement accounted for 31 per cent of the total diastolic excursion. In 9 patients with reversed septal movement, these abnormalities were greater, 92 +/- 39 ms and 33 per cent, respectively, while in 11 patients with diffuse left ventricular involvement they were small, 5-5 +/- 13 ms and 3 per cent. Frame-by-frame digitization of cineangiograms was used to confirm these findings which appear to reflect an abnormal change in left ventricular cavity shape during isovolumic relaxation.

Adult↗
PubMed1976

Analysis of left ventricular wall movement during isovolumic relaxation and its relation to coronary artery disease.

Left ventricular angiograms of 60 patients with ischaemic heart disease and 10 normal subjects were digitized frame by frame in order to study abnormalities of wall movement during the period of isovolumic relaxation. Plots were made of regional wall movement around the cavity throughout the cardiac cycle. In normal subjects 1-5 to 3-0 mm of symmetrical outward wall movement occurred during isovolumic relaxation, associated with an apparent increase of left ventricular volume of 10 +/- 4 per cent. The corresponding peak velocities of wall movement were 4-3 to 5-7 cm/s, significantly less than those recorded in the same region of the cavity after mitral valve opening. In patients with ischaemic heart disease, the following abnormalities were encountered: (1) Abnormal inward movement, which, in single coronary artery disease, occurred in the area supplied by the affected vessel. (2) Abnormal outward movement of more than 6 mm in non-affected areas which appeared to be a compensatory phenomenon. (3) An abnormal cavity shape change towards a more circular configuration before mitral valve opening. (4) Reduced peak rates of wall movement in affected areas during systole and filling. It is concluded that such inward wall movement during isovolumic relaxation is abnormal and a sign of local ischaemia whose presence has significant effects on overall left ventricular function in both systole and diastole.

Cardiac Output↗
PubMed1976

Non-invasive assessment of left ventricular function after correction of severe aortic regurgitation.

Twenty patients were studied with simultaneous left ventricular cavity echocardiograms and apex cardiograms during the first two weeks after correction of severe aortic regurgitation. Endocardial echoes and apex cardiograms were digitized, so that left ventricular dimensions, their rates of change, and echo dimension-apex cardiogram relations could be studied. After aortic valve replacement, there was an early reduction in end-diastolic dimension, within 2 days, from 7-0 +/- 0-8 cm to 5-7 +/- 1-0 cm (P less than 0-001), while peak normalized shortening rate (peak Vcf) dropped from 1-9 +/- 0-6 to 1-4 +/- 0-6 S-1 (P less than 0-01), and remained unchanged for the remainder of the study. Immediately after operation, striking abnormalities of isovolumic contraction and, to a lesser extent, of early relaxation, could be seen, which regressed over 4 to 7 days, except in 2 patients who developed a low output state. These changes in left ventricular dimension, Vcf, and isovolumic contraction could not have been described by an single "measure" of left ventricular function.

Adolescent↗
PubMed1975

Measurement of peak rates of left ventricular wall movement in man. Comparison of echocardiography with angiography.

Estimates of peak systolic and diastolic rates of left ventricular wall movement were made in 23 patients by echocardiography and angiocardiography. Echocardiographic measurements were calculated as the rate of change of the transverse left ventricular dimension, derived continuously throughout the cardiac cycle. These were compared with similar plots of transverse left ventricular diameter, in the same patients, derived from digitized cineangiograms taken within 10 minutes of echocardiograms. The results indicate close correlation between the two methods, and suggest that either can be used to measure peak rates of left ventricular wall movements in patients with heart disease.

Adolescent↗
PubMed1975

Continuous assessment of left ventricular shape in man.

Frame by frame analysis of left ventriculograms has been performed in 10 normal subjects and 40 patients with heart disease. Left ventricular shape index was derived as 4 pi (cavity area)/(perimeter)2, which has a maximum value of 1 when the outline is circular. In normal subjects systole was always associated with progressive reduction in shape index, indicating that the cavity projection had become less circular. This change was smaller in patients with low ejection fraction and also when inferior or anterior hypokinesia was present, even though ejection fraction was normal. During early diastole shape index rose rapidly due to an increase in minor diameter occurring throughout the period of rapid filling. In some cases this preceded any change in long axis, which was due to upward movement of the aortic root as well as outward movement of the apex. These results have functional implications, suggesting in particular that wall movement during filling may be non-uniform and that assumptions about cavity shape used in the derivation of wall properties from estimates of ventricular volume may require modification.

Angiocardiography↗
PubMed1974

Haemodynamic effects of salbutamol in patients needing circulatory support after open-heart surgery.

The effects of substituting an infusion of salbutamol for isoprenaline were studied in 12 patients needing circulatory support after valve replacement surgery. The cardiac output rose while the heart rate remained unaltered. There was a reduction in systemic vascular resistance, and though the oxygen uptake tended to rise the increase in cardiac output was proportionately greater so that the arteriovenous oxygen difference fell.It is suggested that the drug is of value for two reasons. It causes a selective reduction in peripheral arteriolar resistance, which avoids peripheral pooling, but permits limited myocardial work to be used to generate flow rather than pressure, and the increase in cardiac output is not accompanied by a corresponding rise in oxygen uptake.

Albuterol↗