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Transcript
2 4 ~ Medical Research Society found that closing volume increases with age in a linear relationship and is unaffected by bronchodilators. Our preliminary results showed that a satisfactory alveolar plateau and terminal increase in 133Xenonconcentration could be achieved in cardiac patients. Closing volume is increased above the value predicted for age in patients with left heart failure and some of these patients, without reversible airways obstruction, have shown a reduction in closing volume following sympathomimetic bronchodilators. A positive correlation was found between closing volume and residual volume but increase in closing volume was poorly correlated with dyspnoea index and left heart pressures. From our preliminary results we suggest that patients with heart disease may have abnormal airway narrowing and that in some cases this may reflect increased bronchomotor tone. In asthmatic patients the traces produced are difficult to interpret but in some cases following bronchodilator aerosols a change has occurred towards a more normal pattern. Our experience suggests that the 133Xenontechnique may be a useful method for examining airway closure in patients with heart disease. lamella net of elastin and collagen in the media. In addition, the decrease of the area ratio, with the consequent partial standing wave of pressure in the aorta, enhances the oscillatory stress components in the wall at and above the junction. If these localized regions of stress can no longer be distributed uniformly by the damaged interlamella net it would explain the focal nature of atheromatous plaques and their distribution above the junction. In man, the area ratio of the aortic bifurcation has been measured from aortagrams of Caucasian subjects with ages between 0 and 50 years exhibiting no radiological or clinical signs of atherosclerosis. It is found that the area ratio in infancy is 1.11 (close to the expected matched value) and decreases linearly to a value of -0.75 for subjects within the age range of 41-50 years. No significant sex difference was found. 10. LEFT VENTRICULAR WALL MOVEMENT MEASURED BY REFLECTED ULTRASOUND C. S. SMITHEN and E. SOWTON C. F. P. WHARTON, Cardiac Department, Guy's Hospital Movement of the posterior wall of the left ventricle 9. IS ATHEROMA A SECONDARY PHENO- was assessed using an ultrasound technique in eleven normal subjects at rest and immediately following MENON ? R. G. GOSLING, D. L. NEWMAN and N. L. BOWDEN maximal erect exercise. Maximum posterior wall Department of Physics, Guy's Hospital Medical School velocity was measured as the initial slope of the wall movement from end-diastole t o end-systole, and (Introduced by H. Keen) posterior wall excursion was measured as the distance An increase in aortic distensibility is observed in between the end-diastolic and end-systolic positions. cockerels fed an atherogenic crushed egg diet. The Posterior wall velocity increased from a mean of abnormal distensibility is correlated with the severity 37 mmjs at rest to 96 mm/s after exercise (P<O.Ol), of the atherosclerotic lesion using an atherosclerotic and post-wall excursion increased from 4.00 mm at index I ranging from 1 to 100. It is found that in- rest to 6.8 mm after exercise (P<0.01). The effect of creased distensibility occurs very early in athero- heart rate alone on posterior wall movement was genesis and reaches a maximum value around index evaluated using the technique of atrial pacing. Invalues of -40. For index values > 60 the distensi- creasing the heart rate in six patients resulted in a bility decreases to below the normal value due to reduction in both posterior wall velocity and excurincreasing calcification and fibrosis. sion. At identical heart rates in four patients there The increase in aortic distensibility in early athero- was a significant increase in both posterior-wall genesis causes a decrease in the area ratio' of the velocity and excursion during exercise compared to aortic junction which remains as the vessel hardens. atrial pacing. Posterior wall velocity and excursion For an equibifurcation the area ratio giving minimum were potentiated following ectopic beats and were reflection of the pressure pulse is shown theoretically depressed after propranolol injection. to be -1.15. Normal cockerels have aortic junction It is suggested that changes in posterior wall movearea ratios close to this value-1.1 6&0.06 for fourteen ment reflect alterations in left ventricular function birds-whilst eighteen diet cockerels had an average independent of heart rate, and that these changes can area ratio of 0.86-10.06. This would be expected to be measured by reflected ultrasound. lead to the reflection of the pressure pulse increasing from 2% for the matched junction to 25% for the 11. THE USE OF SYSTOLIC TIME INTERVALS diet birds, resulting in a partial standing wave of AS AN ASSESSMENT OF LEFT VENTRICULAR pressure in the aorta with an antinode at the junction. FUNCTION IN ACUTE MYOCARDIAL INComparison of the aortic elastic moduli/pressure FARCTION characteristics, measured in situ, for normal and diet E. D. BENNETT, C. S. SMITHEN and G. E. SOWTON cockerels suggests that an essential factor in early Institute of Cardiology, London, W.l atherogenesis is the partial breakdown of the interThe systolic time intervals obtained from the arterial * Area ratio of any vessel junction = Sum of crosssectional areas of branch vessels divided by the pressure trace, the electrocardiogram and the phonocardiogram have been shown to be useful indicators cross-sectional area of the parent vessel. -