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Biomedical subjects

D G Gibson

Publications and source records attributed to D G Gibson.

At least 163 records · Page 9Linked to original sources
PubMed1983

Diastolic mechanisms of impaired exercise tolerance in aortic valve disease.

In order to determine the significance of abnormalities of diastolic function in patients with left ventricular hypertrophy, exercise echocardiography to heart rates of 140 to 150 beats/min was performed in 18 normal subjects and 14 patients after aortic valve replacement. Simultaneous echo-, phono-, and electrocardiograms were recorded. Left ventricular cavity size was determined at end-diastole and end-systole. The timing of mitral valve opening and closure was measured, and hence left ventricular filling time derived, expressed either as ms/beat, or s/min when multiplied by heart rate. Isovolumic relaxation was taken as the interval between A2 and mitral valve opening. Systolic function, assessed from cavity dimensions, peak VCF, and QA2 interval was normal in all but two patients at rest and on exercise. Isovolumic relaxation was prolonged at rest in the patients to 85 +/- 8 ms (normal 69 +/- 9 ms), but left ventricular filling times were normal. With exercise, in normal subjects, isovolumic relaxation remained constant, but filling times dropped strikingly from 380 +/- 66 ms/beat, or 27 +/- 2 s/min at rest to 115 +/- 10 ms/beat or 16 +/- 2 s/min. In patients with left ventricular hypertrophy, isovolumic relaxation dropped on exercise to 41 +/- 15 ms. Filling periods were normal at rest, 367 +/- 67 ms/beat or 27 +/- 3 s/min, but failed to show the normal drop with exercise, being 240 +/- 44 ms/beat or 28 +/- 4 s/min. At heart rates above 120/min, separation between the two groups was complete. Thus, striking abnormalities of left ventricular filling can be demonstrated on exercise in patients with left ventricular hypertrophy. They appear to represent loss of mechanisms whereby rapid diastolic filling is achieved in the normal subject.

Aged↗
PubMed1983

Mechanisms of reduced left ventricular filling rate in coronary artery disease.

To identify mechanisms underlying slow left ventricular filling in coronary artery disease, left ventriculograms from 93 patients and 18 normal subjects were digitised frame by frame and global and regional function analysed. In 54 patients peak normalised filling rates were above the lower 95% confidence limit of normal (2 X 9s-1) and in 39 they were below. Patients with slow filling had a lower ejection fraction, a higher end systolic volume, and less overall shape index change, although a larger percentage occurred during isovolumic relaxation owing to asynchronous relaxation. Stroke volume was not significantly different. Slow outward wall motion was associated with increased cavity volume and systolic hypokinesis. Wall motion was also appreciably asynchronous, with wide spreads in the times of peak outward velocity and termination of rapid outward movement between regions. Early outward movement usually started in the anterior region, with peak velocity occurring before mitral valve opening, and significantly earlier than that in the apex or the inferior region. Ventricular oscillations occurred during filling in 23 patients. This asynchronous wall movement was unrelated to the distribution of coronary artery disease, systolic hypokinesis, or Q waves on electrocardiograms but was similar to that occurring in mitral stenosis. The main causes of slow left ventricular filling in patients with coronary artery disease appear to be (a) failure to achieve a normal low end systolic volume, with associated loss of physiological changes in left ventricular cavity shape, and (b) incoordinate wall motion during isovolumic relaxation which dissipates energy normally coupled to rapid ventricular filling. The resulting slow and asynchronous wall motion may have clinical implications especially when the time available for left ventricular filling is short.

Adult↗
PubMed1983

Echocardiographic features of tropical endomyocardial disease in South India.

Fifteen patients with tropical endomyocardial disease which had been proved angiographically were studied using M-mode and cross-sectional echocardiography to determine the extent to which specific features of this disease could be recognised by these non-invasive methods. Tethering of the posterior mitral valve leaflet to the ventricular wall in combination with areas of echo-dense material in the posterior left ventricular wall and associated papillary muscle appeared to be a constant diagnostic feature of this disease. Colour coding of regional echo amplitude showed high intensity echoes in a distribution corresponding closely to that of the fibrosis known to occur in this condition. Though M-mode echocardiography did not contribute diagnostic information, it was useful in defining the functional consequences of myocardial or mitral valve disease. Digitisation of records allowed a restrictive pattern of left ventricular filling to be observed. It was concluded that cross-sectional echocardiography, particularly when supplemented by colour coded amplitude processing, can make a confident non-invasive diagnosis of tropical endomyocardial disease and so could be useful in assessing its progression or response to treatment.

Adolescent↗
PubMed1982

Non-invasive assessment of changes in left ventricular relaxation by combined phono-, echo-, and mechanocardiography.

In order to investigate interrelations between early diastolic events, simultaneous apex-, phono-,f and echocardiograms were recorded in 10 normal and 55 patients with ischaemic heart disease. In normal subjects isovolumic relaxation time measured as A2 to mitral valve opening was 72 +/- 9 ms, the interval A2-0 point was 116 +/0 15 ms, and the amplitude of the f wave of the apexcardiogram relative to the total amplitude was 11 +/- 2%. In patients with a normal left ventricular end-diastolic pressure (less than 15 mmHg), isovolumic relaxation time was prolonged to 99 +/- 18 ms, A2-0 point to 162 +/- 5 ms, and the relative height of the f wave was increased to 21 +/- 4%. Isovolumic relaxation time and A2-0 point interval both showed significant inverse correlation with left ventricular diastolic pressure. Glyceryl trinitrate administration or isometric stress both caused well recognised changes in arterial pressure and cavity size. Neither had any additional effect during early diastole in normal subjects. In the patients, however, glyceryl trinitrate prolonged isovolumic relaxation time, delayed the 0 point of the apexcardiogram with respect to A2, increased the interval 0 point - f wave, and reduced the relative amplitude of the f wave. Isometric stress had the opposite effects. These changes extend beyond the end of ventricular relaxation and so are more readily explained on a mechanical basis, possibly as oscillations whose periodicity and degree of damping were increased by glyceryl trinitrate and decreased by isometric stress.

Coronary Disease↗
PubMed1982

Recognition of imperforate atrioventricular valves by two dimensional echocardiography.

The majority of hearts in which selective right or left atrial angiography shows no direct communication between one atrium and a ventricular chamber are considered to be examples of atresia of the right or left atrioventricular valves. Most patients presenting with the clinical features of tricuspid atresia have an absent right atrioventricular connection, while those with features of mitral atresia and a normal aortic root frequently have an absent left atrioventricular connection. By studying 67 patients using two dimensional echocardiography we have identified 12 in whom there was an imperforate atrioventricular valve and not an absent atrioventricular connection. Thus, in 44 hearts with the angiographic features of tricuspid atresia, 36 had absence of the right atrioventricular connection and six had an imperforate right atrioventricular valve. In the latter, four were examples of atrioventricular concordance and two were univentricular hearts of left ventricular morphology in which the mode of atrioventricular connection was through one perforate and one imperforate valve. Similarly, 17 out of 23 cases of mitral atresia had absence of the left atrioventricular connection. The remaining six had an imperforate left atrioventricular valve which was associated with atrioventricular concordance in two patients and with double inlet univentricular heats in four patients.

Child↗
PubMed1982

Effect of age related changes in chamber size, wall thickness, and heart rate on left ventricular function in normal children.

We assessed the effects of age related changes in chamber size, wall thickness, and heart rate of left ventricular function in 78 normal children, aged 1 1/2 to 12 1/2 years, using computer analysis of their left ventricular echocardiograms. Left ventricular cavity size and wall thickness increased linearly with age. Left ventricular fractional shortening, percentage of wall thickening, and the ratio of end-diastolic wall thickness to cavity radius (H/R ratio) did not change with age. Peak Vcf correlated with heart rate and the decrease in heart rate with age resulted in the progressive fall in peak Vcf, while peak rate of left ventricular was thickening remained constant. The peak rate of increase in left ventricular cavity dimension in early diastole varied inversely with heart rate, but independently of cavity size, increasing throughout childhood. The peak rate of wall thinning also increased with age, correlating with wall thickness and not heart rate. Thus, age related increases in left ventricular cavity dimension and wall thickness during the rapid growth period of childhood occurred in such a way that left ventricular architecture (H/R ratio) remained unchanged. This may account for the constancy of regional and cavity systolic function. The greater dependence of diastolic cavity function on heart rate may be explained by the disproportionately greater effect of cardiac cycle length on the duration of diastole and systole.

Aging↗
PubMed1982

Echocardiographic features of eosinophilic endomyocardial disease.

Nine patients with eosinophilic endomyocardial disease who had undergone angiocardiography with histological staging of their disease, were studied by M-mode and two dimensional echocardiography to determine the extent to which specific features of the disease could be evaluated by these non-invasive methods. In seven patients, amplitude processed two dimensional echocardiography showed regions where the relative intensity of endomyocardial echoes was greater than normal, and their distribution corresponded to known areas of fibrosis. Standard two dimensional echocardiography was normal in all but three patients. In eight patients M-mode echocardiography showed only non-specific abnormalities, but appeared to be useful in assessing the functional consequences of myocardial or mitral valve disease. After digitisation a reduction in the duration and an increase in the peak rate of dimension increase during filling was prolonged. It was concluded that amplitude processed two dimensional echocardiography might be useful in diagnosing the extent and severity of endomyocardial disease in patients with hyperosinophilia. These noninvasive techniques may thus provide a means for the early diagnosis of endomyocardial fibrosis and could be useful in assessing in progression or response to treatment.

Adult↗
PubMed1981

Valve replacement without preoperative cardiac catheterization.

During the year 1978, the decision to perform cardiac catheterization in patients with valvular heart disease was delayed until clinical and noninvasive assessment have been completed. As a result, 184 patient underwent operation without invasive studies, and 59 had elective catheterization. Another 62 patients were referred during the same period for valve replacement after routine catheterization had been performed elsewhere. Age, sex distribution, symptoms, and cause of valve disease were similar in all three groups, although we managed emergencies and second operations more frequently without catheterization. In all patients, the preoperative diagnosis was confirmed, and no unexpected pathologic process was encountered. Operative mortality was the same in all three groups, and after two years of follow-up there was no difference in survival or symptoms. No uncorrected valve lesions became apparent in uncatheterized patients. We conclude that routine catheterization is unnecessary before valve replacement but can be reserved for specific indications in some patients.

Adolescent↗
PubMed1981

Regional non-uniformity of left ventricular wall movement in man.

In order to assess the possible importance of regional non-uniformity of left ventricular function, angiograms of 42 normal subjects and 105 patients with coronary artery disease were digitised frame by frame. Regional curvature around the cavity was assessed, only positive curvature being compatible with ellipsoidal geometry. In normal subjects, positive curvature of the anterior wall was shown by all, but on the inferior wall was present in only 12 (28%) at end-diastole and five (12%) at end-systole. In patients with ischaemic heart disease, anterior wall curvature was again positive in all but four with apical aneurysm, but positive curvature of the inferior wall was present more frequently than normal, 47 (42%) at end-diastole and 39 (36%) at end-systole. In these patients, positive curvature at end-diastole was associated with reduced wall movement during ejection. Though the pattern of coronary artery involvement was random, there were conspicuous regional differences in the distribution of abnormal wall movement during isovolumic relaxation. Outward movement was found only on the anterior wall. Abnormal inward movement was five times as frequent on the inferior wall as on the anterior. An ellipsoidal cavity outline is not therefore characteristic of the normal left ventricle and, when present, this configuration is likely to be associated with a reduced amplitude of inferior wall movement. Regional differences of both structure and function can thus be shown in normal and abnormal hearts. They may arise from variation in local fibre architecture. Their presence must be taken into account in interpreting abnormalities of left ventricular function.

Coronary Angiography↗
PubMed1981

Left ventricular fibre architecture in man.

In order to investigate the possibility of regional variation of ventricular structure, 25 normal postmortem human hearts were studied by inspection of cavity shape and subepicardial fibre orientation, by dissection, and by the histology of sections in two orthogonal planes. Ventricular architecture was complex. Inlet and outlet long axes were separated by 30 degrees in the left ventricle. In the right the corresponding figure was 90 degrees. The thickest part of the left ventricular wall was at the base. At the apex there was potential endo- and epicardial continuity. Left ventricular cavity shape departed significantly from any simple geometric figure, there being, consistently, regions of both positive and negative curvature on the diaphragmatic aspect. The presence of trabeculae caused considerable variation in wall thickness. Striking variation was found in the arrangement of subepicardial muscle fibres. Most pronounced was the contrast between the longitudinal arrangement of fibres observed on the oblique margin and the circumferential arrangement of those on the acute. On the diaphragmatic surface of the left ventricle, fibres near the crux and apex ran circumferentially while those between ran obliquely; those on the diaphragmatic surface of the right ventricle also ran circumferentially. Deeper in the myocardium the arrangement was simpler. In the mid-wall of the left ventricle fibres were circumferential, best developed towards the base and in the upper part of the septum. Near the apex of the left ventricle and in the mid-wall of the right ventricle such fibres were sparse. The subendocardial region consisted of longitudinally directed fibres forming the trabeculae and papillary muscles, while fibres deep to and between the trabeculae coursed more obliquely. These findings were confirmed by histology. Models based on uniform myocardial fibre structure cannot explain wall movement in normal subjects, and are likely to have significant limitations if used to investigated left ventricular function in disease.

Dissection↗
PubMed1981

Regional non-uniformity of wall dynamics in normal left ventricle.

M-mode echocardiograms were performed in 31 normal children in order to compare myocardial wall dynamics in different regions of the left ventricle. Tracings were recorded at the level of the mitral valve ring (level 1), near the tips of the mitral valve leaflets (level 2), and in the region of the papillary muscles (level 3) and were digitised. Fractional shortening increased from 31.7 per cent at level 1 to 36.5 per cent at level 3. Peak VCF and minor dimension lengthening rate were the same at all three levels, as were end-diastolic posterior wall thickness and peak systolic wall thickening rate. Striking regional differences, however, were seen in the extent of systolic posterior wall thickening which increased from 55 per cent at the base to 106 per cent at the papillary muscles, and in peak posterior wall thinning rate, which increased from 6.4 cm/s at the base to 10.0 cm/s at the papillary muscles. There was greater systolic inward movement of epicardium at level 1 than at levels 2 and 3. The septum thinned and thickened more slowly than did the posterior wall and did not show major differences between levels. Systolic reduction in minor dimension thus occurs largely by thickening of the wall at level 3 and by sphincter-like inward movement of the entire wall at level 1. These regional differences can be explained by a circumferential arrangement of myocardial fibres at the base of the heart and a more prominent longitudinal component towards the apex. Thus, non-uniformity of function is a prominent feature of the normal left ventricle and may reflect regional variation in its structure.

Child↗
PubMed1981

Clinical application of amplitude processing of echocardiographic images.

In order to assess the possible clinical value of measuring regional amplitude of ultrasound reflected from intracardiac structures, two-dimensional echocardiographic images from 20 normal subjects and 70 patients with heart disease were processed by modulation of both colour and intensity to represent grey scale. Maximum echo intensity was consistently recorded from the pericardial interface behind the posterior left ventricular wall, and this was taken as 100 per cent. In the normal heart, central fibrous body reflected at 64 +/- 5 per cent, and mitral and aortic valves at 35 +/- 5 per cent and 36 +/- 8 per cent, respectively. Normal septal myocardium gave a valve of 33 +/- 8 per cent and posterior wall of 23 +/- 6 per cent. Consistent increases were recorded from prosthetic mitral valves in 20 patients, and also from the anterior cusp of the mitral valve (54 +/- 11%) in 20 patients with rheumatic heart diseases. In all of 15 patients with left ventricular involvement caused by coronary artery disease, septal echo amplitude was increased in all to 71 +/- 11 per cent, and localised increases were also noted in the posterior wall, subendocardially, or in one or both papillary muscles. Similar focal changes were noted in five, and increases in septal density in 10 of 15 patients with left ventricular hypertrophy and in 12 of those with mitral valve disease. Thus, measurement of regional echo amplitude is possible without degradation of the quality from standard two-dimensional cardiac images. Abnormalities are particularly common in left ventricular disease where their distribution corresponds to that described for fibrous tissue.

Cardiomegaly↗
PubMed1981

Echocardiographic demonstration of aortic root abscess after infective endocarditis.

We describe a patient with infective endocarditis in whom the diagnosis was apparent only on two-dimensional echocardiography. There was no clinical or haematological evidence of active endocarditis and the diagnosis was made by the demonstration of an abscess cavity and vegetation posterior and lateral to the aortic root, deforming the left atrial cavity. The findings were confirmed by cardiac catheterisation and operation.

Adult↗