SUMMARY Eight hundred and four patients with persistence of the ductus arteriosus were seen in Edinburgh between 1940 and 1979. Thirty-seven of them reached the age of 50 years, and in 32 the shunt was exclusively from left to right. Fifteen of the 32 were subsequently treated surgically.None of the 32 was lost to follow-up. Duration ofclinical observation averaged 17 years and extended to over 30 years in eight patients. Their features have been correlated with those from reports of 48 comparable patients in an attempt to clarify the management of the persistent ductus in the older patient. Impairment of left ventricular function is shown as the major risk, even when the ductus is small. Bacterial endarteritis is infrequent.Surgical treatment carries greater risk than in childhood and early adult life but usually reduces heart size and restores exercise tolerance. Left ventricular dysfunction, however, occasionally vitiates the benefits; symptoms are then incompletely relieved and death from heart failure may occur months or years after operation. Experience in older patients thus emphasises the value of elective operation in childhood, however well the child, however trivial the shunt.It is concluded that in older patients, the presence or the development of symptoms or cardiac enlargement are almost always indications for surgical treatment. As age increases, especially by the eighth decade, medical treatment may be preferable. Continued follow-up of symptomless patients without cardiomegaly is important because increase in heart size usually precedes further deterioration which can then be prevented by timely surgical treatment.Most patients with persistence of the ductus arteriosus die before 50 years of age'-3 unless treated surgically.4 5 Occasional patients, however, survive with little disability and a few live a normal life span.6-9 In the majority of adults, exercise tolerance is liable to deteriorate rapidly'I and in them surgical treatment has been of great benefit, even at over 65 years of age. 1"12 Available information, however, has been based on single case reports with little long term follow-up.The Edinburgh experience of the persistent ductus since 1940, with and without surgical treatment, has therefore been analysed and correlated with earlier reports in an attempt to amplify knowledge of the clinical course and improve the management of these older patients. The 40 years, 1940 to 1979, have been selected in order to encompass periods before and after 1%1 when the first older patient with a persistent ductus was treated surgically in Edinburgh. During this time 37 patients (among a total of 804 with persistence of the ductus) had reached 50 years of age before death, surgical treatment, or their last medical assessment. Twentynine were women and eight were men. In five patients, severe pulmonary hypertension was associated with a right to left shunt. The progress of the 32 patients, in whom the shunt was exclusively from left to right, is the subject of the present study (Table). One of the...
Abstract-A fading-memory system is a system that tends to forget its input asymptotically over time. It has been shown that discrete-time fading-memory systems can be uniformly approximated arbitrarily closely over a set of bounded input sequences simply by uniformly approximating sufficiently closely either the external or internal representation of the system. In other words, the problem of uniformly approximating a fading-memory system reduces to the problem of uniformly approximating continuous real-valued functions on compact sets. The perceptron is a parametric model that realizes a set of continuous real-valued functions that is uniformly dense in the set of all continuous real-valued functions. Using the perceptron to uniformly approximate the external and internal representations of a discrete-time fading-memory system results, respectively, in simple finite-memory and infinite-memory parametric system models. Algorithms for estimating the model parameters that yield a best approximation to a given fading-memory system are discussed. An application to nonlinear noise cancellation in telephone systems is presented.
SummaryRecent changes in the structure of the examination for M.R.C.P. (U.K.) have prompted a review of these together with a historical outline of the examinations which preceded it at the Royal Colleges of Physicians of Edinburgh, Glasgow, and London.Part I of the examination continues to fulfil its role as a screen and a slight change in the marking system appears to have improved its discriminating powers still further. The major change in part II is the substitution of a more objective written test in place of the essay papers.
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