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Biomedical subjects

S S Quek

Publications and source records attributed to S S Quek.

16 recordsLinked to original sources
PubMed2001

A ten-year review of ruptured sinus of valsalva: clinico-pathological and echo-Doppler features.

Rupture of the sinus of valsalva (RSOV) is an uncommon condition with a variety of manifestations ranging from an asymptomatic murmur to cardiogenic shock. This retrospective 10-year review (1985-1995) of 18 patients from a single institution revealed that 6 (33%) were female and 12 (67%) were male with a mean age of 37.6 +/- 13.4 years and that 72% were Chinese by ethnic descent with the remaining 28% being Malay. Eight patients (44.4%) presented with an asymptomatic murmur, 4 (22.2%) with acute chest pain, 4 (22.2%) with mild heart failure, 2 (11.1%) with severe heart failure, and 2 (11.1%) with cardiogenic shock. Rupture of the right aneurysmal coronary cusp (RCC) made up 15 (83.3%) while those of the non-coronary cusp (NCC) made up the remaining. Most of the RCC ruptures were directed into the right ventricle and all of the NCC ruptures were into the right atrium. Ventricular septal defects (VSDs) were found in 9 (50%) of the patients, (although detected by echocardiography in only one third of those patients), aortic regurgitation in 6 (33.3%) and aortic valve vegetations in 2 (11.1%). Echocardiography was found to be accurate in diagnosing RSOVs with 100% diagnostic accuracy after 1990 with four misdiagnoses before 1990. Of these four patients, two were misdiagnosed as having VSDs, one as having a coronary arteriovenous fistula and one as having a patent ductus arteriosus. The anatomical structure of the "windsock" was seen in 64% of the patients who were correctly diagnosed. The pattern of colour flow and spectral Doppler was seen in all patients and helped to localise the site of rupture and the direction of flow. In summary, echocardiography is a simple and accurate way of diagnosing and defining RSOVs and is the imaging modality of choice.

Adult↗
PubMed2000

Use of artificial neural networks to predict drug dissolution profiles and evaluation of network performance using similarity factor.

PURPOSE: To use artificial neural networks for predicting dissolution profiles of matrix-controlled release theophylline pellet preparation, and to evaluate the network performance by comparing the predicted dissolution profiles with those obtained from physical experiments using similarity factor. METHODS: The Multi-Layered Perceptron (MLP) neural network was used to predict the dissolution profiles of theophylline pellets containing different ratios of microcrystalline cellulose (MCC) and glyceryl monostearate (GMS). The concepts of leave-one-out as well as a time-point by time-point estimation basis were used to predict the rate of drug release for each matrix ratio. All the data were used for training, except for one set which was selected to compare with the predicted output. The closeness between the predicted and the reference dissolution profiles was investigated using similarity factor (f2). RESULTS: The f2 values were all above 60, indicating that the predicted dissolution profiles were closely similar to the dissolution profiles obtained from physical experiments. CONCLUSION: The MLP network could be used as a model for predicting the dissolution profiles of matrix-controlled release theophylline pellet preparation in product development.

Cellulose↗
PubMed1995

Clinical utility, safety, acceptability and complications of transoesophageal echocardiography (TEE) in 901 patients.

Transoesophageal echocardiography (TEE) has earned an important role in the evaluation of patients with cardiovascular diseases. We report our TEE experience in 901 patients who had suboptimal transthoracic echocardiographic studies performed between September 1989 and June 1993. The patient-population consisted of 459 females and 442 males, with an ethnic distribution of Chinese 76.5%, Malays 12.7%, Indians 8.5% and Others 2.3%. The mean age was 48 years. The main indications for TEE were: cardiac source of embolism (27.5%); native valve pathology (19.1%); atrial septal abnormality (9.7%); infective endocarditis (8.3%); intracardiac masses (7.0%); prosthetic valve dysfunction (6.3%); congenital heart diseases (4.6%); aortic diseases (3.4%) and miscellaneous (14.1%). The majority of the studies were done on in- and out-patients, with only 1.2% performed in the intensive care area and 1% intraoperatively. 82.6% of TEE intubation were accomplished within one minute and most of the TEE studies were completed within twenty minutes. There were ten failures (1.2%). Major complications occurred in 5 patients (0.6%) but there was no mortality. 90.5% of the studies were considered by the operators as additionally-informative or useful for clinical decision making. In a subgroup analysis, 90.6% of the patients who had undergone TEE indicated their willingness for repeat studies if required and TEE was able to increase the sensitivity of detecting a potential cardioembolic source from 10.3% to 29.5%. In conclusion, with increasing experience, TEE can be performed expeditiously and safely, with good acceptability by our local population. TEE provides useful or additional information that supplements standard transthoracic echocardiography in a wide-ranging spectrum of cardiac conditions.

Adolescent↗
PubMed1992

Cardiac life support training: the Ministry of Health's experience.

This study reviews the records of all cardiac life support training courses conducted at the Ministry of Health's Life Support Training Centre situated in Singapore General Hospital over a six period from 1985 to 1990. A total of 1,789 persons were trained in Basic Life Support (BCLS), 65 as BCLS Instructors, 267 in Advanced Cardiac Life Support (ACLS), 276 in Emergency Cardiac Care (ECC) and 24 in Emergency Cardiac Defibrillation (ECD). These courses have involved a total of 1111 doctors, 1248 nurses and 62 ancillary staff. At the end of the course, 90.7% of those learning BCLS agreed that they would use their CPR skills, if required. Only 60% felt they would use mouth-to-mouth ventilation. Of 415 who expressed an interest in becoming instructors, 15.7% have, to-date, been trained. While more than 80% of persons learning, ACLS were doctors, only 25% of these were willing to instruct. There are currently 14 ACLS instructors. The ECC courses were modified from the ACLS course and taught to Emergency Room doctors only. It was found to be immensely popular with 98% expressing benefit. The ECD programme trained emergency ambulance nurses in the use of semi-automatic electrical defibrillators. The marked increased in yearning for cardiac life support skills amongst medical and nursing staff has been a major factor in the proliferation of life support training programmes at the Centre. Nurturing this enthusiasm is the key to ensuring that the programmes continue to expand for the benefit of both inpatients and the out-of-hospital lay public.

Attitude of Health Personnel↗
PubMed1990

Clinical impact of echo-Doppler in the management of heart disease.

The management of patients with cardiovascular disease requires a comprehensive evaluation of both morphological and pathophysiological abnormalities associated with the disease process. To this end, a diagnostic technique that is noninvasive, painless, biologically safe, readily repeatable, economical and highly accurate would be ideal. The echo-Doppler modality satisfies these criteria and in so doing has emerged the diagnostic procedure of choice in many instances. While echocardiography supplies detailed anatomical information on cardiovascular structures, the Doppler mode define the associated haemodynamic profiles. Used in complement, they provide a complete pathophysiological picture in the majority of congenital and acquired cardiac diseases, aiding both diagnostic and therapeutic management decisions.

Blood Flow Velocity↗
PubMed1990

Transoesophageal echocardiography--an overview.

The introduction of transoesophageal echocardiography has provided another acoustic window to the heart and mediastinum. The unique relationship of the esophagus to the heart and thoracic aorta has made transesophageal echocardiography ideal for imaging and assessment of the mitral valve particularly mitral prosthesis, atrial appendages, atrial septum, cardiac masses, aortic valve and thoracic aorta. It is a safe procedure and can be easily performed on patients as an outpatient procedure, on critically ill patients as well as for intraoperative monitoring of left ventricular function and air embolism and intraoperation assessment of cardiovascular surgical procedures.

Aortic Diseases↗
PubMed1990

Ventricular septal rupture in acute myocardial infarction.

This is a review of 31 patients with ventricular septal rupture occurring in myocardial infarction which have been managed at the Singapore General Hospital. Ventricular septal rupture occurs more frequently in the elderly, in females and those presenting with the first myocardial infarction. Very few have a prior history of stable angina pectoris before the myocardial infarction. Sudden deterioration as manifested by an increase in heart rate, fall in blood pressure and signs of right heart failure in a patient with acute myocardial infarction (AMI) especially if accompanied by a systolic murmur should encourage a search for a mechanical cause, especially a ventricular septal rupture. 2D echocardiography or Swan-Ganz catheterisation are 100% diagnostic and can be easily and rapidly done at the bedside. Medical management includes vasodilator therapy and inotropic support. Intra-aortic balloon counterpulsation is especially useful and was instituted in 6 patients. Early surgical repair of the ventricular septal defect is important if overall prognosis of these patients is to be improved. Our operative survival of 42.9% is comparable to others, considering that without surgery all have died. Survival appears to be related to the site of the myocardial infarction (very poor prognosis in inferior myocardial infarction), operative treatment (no survivors if treated conservatively) and the mode of presentation (poor prognosis in patients who develop a ventricular septal rupture while in hospital).

Aged↗
PubMed1990

Coronary risk profile screening during National Heart Week--1986.

Coronary risk profile screening was performed in 1422 volunteer subjects during National Heart Week 1986. A great proportion (55%) of this study group had blood cholesterol above 200 mg/dl; 10% of the subjects were smokers. This study documents the coronary risk profile of 1422 subjects whose biodata provide a baseline for future follow up of the possible changes in any of the various risk factors. This study identifies modifiable risk factors, high blood cholesterol and smoking which should be the target of public education in the efforts to reduce coronary diseases in Singapore.

Adult↗
PubMed1989

PTCA--the initial 100 cases in the Singapore General Hospital.

Percutaneous transluminal coronary angioplasty (PTCA) is an increasingly important technique for the treatment of patients with coronary artery disease. One hundred cases of PTCA were performed in Singapore General Hospital between 1985 to September 1988. 87% were males and 13% were females. The mean age of these patients were 55 +/- 9 SD years (range from 28 to 79 years). 85% had angina pectoris, 43% had a previous myocardial infarction and 12% received intravenous streptokinase previously. One hundred and twenty-nine lesions were dilated. 51% of the cases had single, 40% had double and 9% triple vessel disease. 83% had single, 16% double and 1% triple vessel dilatation. The distribution of the cases by vessel location was 64% for LAD, 19% for RCA and 17% for CX. Overall lesion success was 86%, with an increment in the success rate from 76% in 1987 to 89% in 1988. Similarly, the clinical success rate was 86% for the whole group; it increased from 74% to 90% from 1987 to 1988. The mean diameter stenosis was decreased from 86 +/- 14% SD predilatation to 28 +/- 28% SD postdilatation (p less than 0.005). The mean transtenotic gradient was reduced from 60 +/- 17 mmHg SD predilatation to 18 +/- 11 mmHg SD postdilatation (p less than 0.005). There were 14 failures (14%), the majority of which were due to inability transversing the lesion with a guide wire or balloon catheter. Fourteen complications (14%) occurred in these 100 cases of PTCA. 3% required emergent/semiemergent surgical revascularization. There was no mortality. PTCA is now an established mode of therapy for coronary artery disease in Singapore General Hospital.

Adult↗
PubMed1988

Mitral valve prolapse--a review.

Mitral valve prolapse is one of the more common cardiac conditions in our community. The prevalence is difficult to assess due to differences in diagnostic criteria and population selection. The prevalence in the community has been estimated to be from 5 to 15%. In females there is a decline in prevalence with increasing age which is not observed in males. 30% of subjects with mitral valve prolapse have relatives with the same condition. Strahan et al suggested that mitral valve prolapse was inherited as an autosomal dominant trend with its manifestations modified by age and other factors.

Humans↗
PubMed1980

Six-month's experience (July 1978--December 1978) in a medical intensive care unit.

The Medical Intensive Care Unit at Tan Tock Seng Hospital was established in October 1970. Additional beds were added to the Unit over the years and by June 1977 it had become a 10-beded Unit. A survey of admissions for a six month period from July 1978 to December 1978 was done to gain further insight into future needs. Six hundred and eleven patients were admitted during this period. Two thirds of the patients were over the age of 50. There were 451 (73.4%) with cardiovascular problem and 160 (26.6%) with other acute medical problems. Of the patients with cardiovascular problems, 232 had acute myocardial infarction. The duration of stay in the Unit was less than 3 days in 80% of the patients. The mortality rate was 15.7%.

Adolescent↗