Biomedical subjects
Publications and source records attributed to M H Choo.
Isolated quadricuspid aortic valve is a rare congenital anomaly. We present a case diagnosed on cross-sectional echocardiography. To the best of our knowledge, this is the first case report on echocardiographically diagnosed quadricuspid aortic valve in Singapore.
Over a period of 36 months, we detected 54 patients with normal coronary arteries or non-critical coronary artery stenosis within our study series of coronary angiography. We studied these patients to determine their clinical, electrocardiographic, stress testing and angiocardiographic characteristics. We detected among them a preponderance of female sex and a higher incidence of ethnic Indians. The majority of the patients studied had one or more coronary risk factors. 52% had a normal resting ECG. In those with a positive stress test and reports available for review, there is a near equal distribution of horizontal and J-type ST depression. Those patients with a positive treadmill tend to have a higher left ventricular end diastolic pressure (LVEDP) at cardiac catheterization. We also noted in this group of patients a higher proportion with a small distal left anterior descending artery. These patients also tend to have higher LVEDP even in the presence of normal left ventriculogram. Our current series suggests the possibility of raised left ventricular end-diastolic pressure and the presence of a "small distal left anterior descending artery" syndrome in association with patients with a 'false positive' treadmill test.
We report a case of mitral stenosis with a large left atrial thrombus which was obstructing pulmonary venous inflow where the conventional use of the pulmonary capillary wedge pressure as an approximation of the left atrial pressure during diagnostic cardiac catheterisation led to the over-estimation of the severity of mitral stenosis.
Pure red cell aplasia (PRCA) is characterised by an anaemia with reticulocytopenia but with normal leukocyte and platelet counts, and a bone marrow with the selective absence of erythroid precursor cells. Drug-induced PRCA is a rare cause of secondary erythroid aplasia, but distinct from the primary and most secondary forms, it is usually acute and fully reversible upon withdrawal of the causative drug. We report a 36 year-old Chinese man who developed diphenylhydantoin associated PRCA two months after commencing the treatment. Reappearance of reticulocytes was observed six days following the cessation of diphenylhydantoin therapy and the haemoglobin level rose to normal one month later. The extreme rarity of this adverse reaction to a drug used so widely strongly suggests an individual predisposition.
The accurate measurement of blood pressure is the bedrock of the proper management of disorders of arterial pressure. This is especially important as hypertension is a prevalent disease, with very considerable impact on morbidity and mortality. Pitfalls in the measurement of blood pressure occur in three main areas: blood pressure measurement devices, blood pressure measurement technique, and blood pressure sampling pattern. Ignorance concerning these areas leads to errors of diagnosis, particularly overdiagnosis in persons with borderline or labile blood pressure. By contrast, skilful application of blood pressure measuring devices will increase one's understanding of blood pressure physiology, pathology, and response to treatment.
Between December 1980 and December 1987, approximately 6,000 two-dimensional echocardiographic examinations were performed in our noninvasive cardiac laboratory. During this period, five cases of intra-atrial smoke-like echoes were diagnosed. The four patients with dense smoke-like echoes in the left atria all had echocardiographic evidence of severe mitral stenosis and thrombi in the left atrial cavity, both of which were confirmed at open-heart surgery. One patient with right-sided cardiomyopathy had echocardiographic evidence of dense smoke-like echoes and thrombus in the right atrial cavity. One of our five patients was receiving anticoagulant therapy, and none had a history of thromboembolism. We conclude that using conventional two-dimensional echocardiographic techniques, smoke-like echoes in the atria are a very infrequent finding and are very commonly associated with formation of thrombi.
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Electrocardiograms from 204 subjects aged 60 and above, residing in homes for the aged, were analysed. 13% had evidence of cardiovascular disease. 55% of the electrocardiograms showed at least one abnormality. At least 10% of electrocardiograms showed left atrial hypertrophy, first degree atrioventricular block, right bundle branch block, pathologic Q waves, ST-T abnormalities, or prolonged QT interval. Findings predictive of cardiovascular disease were left ventricular hypertrophy patterns and ST-T abnormalities, or prolonged QT interval. Findings predictive of cardiovascular disease were left ventricular hypertrophy patterns and ST-T abnormalities. Increase of age from 60 to 100 years was associated with prolongation of PR and QT intervals, but shortening of the RR interval.
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Postectopic normalization of inverted U waves, a previously undescribed phenomenon, provides another parallel to T wave behavior.
Spontaneous change in direction of F waves in atrial flutter is rare. Its analysis may lend some insight to the current uncertainty about mechanisms responsible for atrial flutter.
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