Biomedical subjects
Publications and source records attributed to K H Tan.
The mechanisms of pruritus, an unpleasant irritation on the skin that provokes an urge to scratch, are reviewed. Whilst symptomatic treatment is only partially effective, antihistamines remain the first choice of treatment. However, recent novel treatment using opiate antagonists, propofol (subhypnotic doses) and serotonin antagonists offer attractive alternatives.
The angiographic findings of 569 patients who underwent repeat coronary angiography for recurrence of chest pain after successful coronary angioplasty were evaluated. On the basis of angiographic findings, 250 patients (44%) were classified as having restenosis, 72 (13%) incomplete revascularization, 115 (20%) new significant coronary artery lesions, and 132 (23%) no significant disease. The number of diseased vessels at the time of coronary angioplasty (P < 0.001), number of vessels dilated (P < 0.001), and in particular, the time from angioplasty to recurrent chest pain (P < 0.001), were predictive of angiographic findings. When chest pain recurred within 4 weeks of angioplasty, 70% of patients had either incomplete revascularization or no significant coronary artery stenosis, when it recurred between 4 and 24 weeks of angioplasty, restenosis was the most common finding (71%), and when it recurred more than 24 weeks after angioplasty, new disease was the most common finding, occurring in 53% of patients. Of the 115 patients who developed new disease, angioplasty was initially performed on 133 vessels, and 222 vessels were not dilated. At repeat angiography, 81 of the 133 vessels (61%) that had had angioplasty and 109 of the 222 vessels (49%) that had not had angioplasty had new lesions; this difference was significant at P = 0.03. In conclusion, although the most common cause of recurrence of chest pain after initially successful coronary angioplasty was restenosis, other mechanisms may also be responsible. The time from coronary angioplasty to onset of recurrent chest pain was the most powerful predictor of angiographic outcome. The incidence of new lesion development was higher in the vessels that had instrumented angioplasty, possibly reflecting accelerated atherosclerosis or increased fibrocellular proliferation from intimal injury.
The acute and long-term outcome of 198 patients who underwent coronary angioplasty of ostial stenoses was evaluated. Procedural success was achieved in 85% of aorta ostial stenoses, 90% of non-aorta ostial stenoses, and 87% of branch ostial stenoses (P = 0.84). A major complication occurred in 5.9%, 6.3%, and 6.9% of patients who underwent aorta ostial, non-aorta ostial, and branch ostial stenosis angioplasty, respectively (P = 0.97). A greater residual stenosis (P = 0.005) resulted from angioplasty of aorta ostial lesions despite a greater inflation frequency (P < 0.001), inflation pressure (P < 0.001), and total inflation duration (P < 0.001). The restenosis rate was higher for aorta ostial lesions (71%) when compared to non-aorta ostial (60%) and branch ostial lesions (32%) (P = 0.01). However, since the denominator included only the 49% who returned for repeat coronary angiography, the exact angiographic restenosis rate cannot be determined. The cumulative probability of survival was 99% at 1 year and 93% at 3 years. The 1 and 3 year freedom from death, myocardial infarction, bypass surgery, and repeat angioplasty was 70% and 57%, respectively. At census, 57% were asymptomatic, and only 9% suffered severe angina. Coronary angioplasty of ostial stenoses can be carried out with an acceptable success and complication rate, and provides good symptomatic relief and favourable long-term outcome. Randomized trials to compare new angioplasty technology with balloon angioplasty will be necessary to select the best device therapy for ostial lesions.
BACKGROUND: To evaluate the acute and long-term results of 'tandem lesion' coronary angioplasty in the left anterior descending artery, and to identify the determinants of restenosis. METHODS: A retrospective analysis of clinical, angiographic, and procedure-related variables was carried out on a consecutive series of 102 patients (mean age 54 years, range 34-71 years; 77% men) who had undergone tandem lesion coronary angioplasty in the left anterior descending artery (204 lesions) between 1981 and 1991. RESULTS: Angiographic success was achieved in 96 patients (94%) and 195 lesions (96%). Clinical success was achieved in 91 patients (89%). Five patients (5%) suffered a non-fatal Q-wave myocardial infarction. No procedural deaths occurred. Complete follow-up data were available for all 102 patients (median 46 months, range 1-122 months). During the follow-up period, two patients (2%) died, two (2%) suffered non-fatal myocardial infarction, and 18 (18%) underwent a second revascularization procedure. The cumulative probability of survival was 98.9% and 97.8% at 1 and 5 years respectively. Survival free from myocardial infarction, bypass surgery and repeat angioplasty at 1 and 5 years was 80.8% and 74.9% respectively. Thirty patients underwent repeat angiography (mean 8.8 months) for symptoms or evidence of reversible ischaemia. Restenosis occurred at a single dilated site in 14 patients and at both sites concurrently in six patients. Eight patients had no restenosis but two had total occlusion of the left anterior descending artery. Multiple logistic regression analysis identified increased inflation frequency as the only independent predictor of restenosis. CONCLUSIONS: Tandem lesion coronary angioplasty of the left anterior descending artery can be performed with a high primary success rate and favourable long-term outcome. The fact that restenosis occurred at a single site more often than at both, suggests that systemic factors are less important than local factors in influencing restenosis.
OBJECTIVE: To report on the short-term and long-term results of patients who underwent a third coronary balloon angioplasty for a second restenosis and to identify the correlates of a third clinical restenosis. DESIGN: A retrospective analysis of clinical, angiographic, and procedure related variables of a consecutive series of patients. PATIENTS: 62 patients (mean (range) age 53 (31-72) years; 84% men) who underwent a third coronary balloon angioplasty of a single coronary artery segment at which restenosis had occurred after two previous angioplasty procedures between 1986 and 1992. RESULTS: Procedure success was achieved in 56 patients (90%). Complications included one myocardial infarction (2%) and one emergency coronary artery bypass surgery (2%). Complete follow up data were available (median (range) 48 (12-94) months). During the follow up period, four patients (6%) died, two (3%) had a non-fatal myocardial infarction, and five (8%) underwent elective coronary artery bypass surgery. Nine patients (14%) underwent a fourth angioplasty for a third clinical restenosis, and three (5%) had a fourth angioplasty procedure for new coronary lesions. The cumulative probability of survival for all 62 patients was 97% and 95% at 1 and 5 years, respectively. The 1 and 5 year freedom from death, infarction, bypass surgery, and repeat angioplasty was 82% and 66.6%, respectively. At census, of the 58 survivors, 31 (53%) were asymptomatic and only eight (14%) complained of angina grade III or IV (P < 0.001). A third clinical restenosis occurred in 22 (39%) of the 56 patients who had initially successful procedures. Multiple stepwise logistic regression analysis identified the interval between the second and third angioplasty procedure as the only independent predictor of a third clinical restenosis (P = 0.004). CONCLUSIONS: A third coronary angioplasty for a second restenosis can be performed safely and effectively and should be considered as an integral part of the overall coronary angioplasty revascularisation strategy. The incidence of a third clinical restenosis remains high, however, and is correlated with the interval between the previous angioplasty procedures.
OBJECTIVE: To evaluate the short and long term results of coronary angioplasty in patients aged 70 years and older and identify the determinants of long-term survival. DESIGN: A retrospective analysis of clinical, angiographic, and procedure related variables on a consecutive series of patients. PATIENTS: 163 patients aged 70 years and older (mean (range) age 73 (70-83) years; 63% men) who underwent a first coronary angioplasty procedure between 1981 and 1993. RESULTS: Procedural success was achieved in 82% of patients. Four patients (2%) died, three (2%) had a myocardial infarction, and five (3%) underwent emergency coronary artery bypass surgery. Complete follow up data were available for all patients (median (range) 35 (2-146) months). During the follow up period 16 patients (10%) died, two (1%) suffered non-fatal myocardial infarction, and 12 (7%) underwent elective coronary artery bypass surgery. A second angioplasty procedure was performed in 24 patients (15%). The cumulative probability of survival was 90.7% at 1 year and 83.4% at 5 years. Survival free from myocardial infarction, bypass surgery, and repeat angioplasty at 1 and 5 years was 68.2% and 56.0%, respectively. Proportional hazards regression analyses identified incomplete revascularisation as the only independent predictor of poorer overall survival (P = 0.04) and event free survival (P < 0.001). At census, of the 143 survivors, 75 (52%) were asymptomatic, 58 (41%) had mild angina, and only 10 (7%) complained of grade III or IV angina. Some 112 patients (78%) improved by at least two angina grades. CONCLUSION: Coronary angioplasty can be performed safely in the elderly and provides good symptomatic relief and favourable long-term outcome. Complete revascularisation may not be necessary if the primary goal is to achieve symptomatic relief, but incomplete revascularisation is associated with poorer long-term survival.
OBJECTIVE: To study the aetiology and pattern of Postmenopausal Bleeding (PMB) in the local population. DESIGN: A retrospective study SUBJECTS: 163 consecutive patients who presented with postmenopausal bleeding (PMB) SETTING: Kandang Kerbau Hospital, Singapore RESULTS: Malignant causes were found in 42 (25.7%) patients. Cervical carcinoma was the most common malignancy (12.9% of the patients) followed by endometrial carcinoma (11%). Important benign causes are cervicitis (12.9%), atrophic vaginitis (12.3%) and cervical polyp (6.7%). Other benign causes include endometrial hyperplasia (3.1%), urethral caruncle (2.5%) and estrogen replacement therapy (1.8%). CONCLUSION: PMB is a symptom of varied aetiologies. The associated incidence of malignancy is high and a thorough diagnostic evaluation is mandatory.
INTRODUCTION: The mean red cell volume (MCV) has been shown to be useful in a 2-stage screening process for beta-thalassaemia traits among pregnant women though associated with a large number of false positive results. We tested prospectively the ability of 5 discriminant functions (DF), (England & Fraser, Shine & Lal, Mentzer, Srivistava and Klee et al) to reduce the number of false positives when used as additional screening determinants for beta-thalassaemia in antenatal patients with red cell microcytosis. METHODS: The diagnostic performance of each DF was compared in 493 patients with microcytosis and known beta-thalassaemia status. Truth table analysis and Receiver Operation Characteristic curves for each function were determined. RESULTS: 11.4% of the patients with microcytosis were diagnosed to have beta-thalassaemia traits. DFs incorporating the red cell indices: haemoglobin or total red cell count are unsuitable during pregnancy. Shine & Lal's index [(0.01 x MCH x (< MCV)2] reduced the number of people recalled for confirmatory testing by 31.1% and increased the diagnostic yield to 38.7% while maintaining a negative predictive value for the test of 0.993. CONCLUSION: We conclude that a 3-stage screening process for beta-thalassaemia among pregnant women in Singapore involving the MCV, Shine & Lal's index and a confirmatory test to be both valid and cost-effective.
The aim of this paper is to determine the antecedent factors, clinical presentation, complications and management of uterine rupture in the context of modern obstetric practice in Singapore. We conducted a retrospective study of 26 proven cases of uterine rupture in Kandang Kerbau Hospital, Singapore between January 1983 to December 1992. These cases were analysed with regards to their past history, clinical presentation, complications, management and outcome. The incidence of uterine rupture was 1 in 6331 deliveries. The ratio of cases with scarred uteri against those with unscarred uteri was 3:1. The commonest antecedent factor was previous lower segment caesarean section for the scarred group and cephalo-pelvic disproportion in the unscarred group. Overall, 46.2% of the patients had augmentation with oxytocin. The major clinical presentations were abnormal cardiotocogram (25%) and blood-stained amniotic fluid (20%) in the scarred group, and postpartum haemorrhage (50%) and shock (33%) in the unscarred group. Repair of the uterus with or without tubal ligation was performed in 95% of the patients with scarred uteri, whereas 67% of the patients with unscarred uteri underwent total abdominal hysterectomy with or without salpingo-oophorectomy. There was 1 (3.8%) maternal death. Maternal morbidity included bladder injuries, broad ligament haematoma, disseminated intravascular coagulation and gastrointestinal bleeding. The overall incidence of fetal loss was 7.4%. When compared to a previous study on uterine rupture in the same hospital, there was an improvement in obstetric performance.
We evaluated the acute and long-term results of percutaneous transluminal coronary angioplasty in 140 patients with prior coronary artery bypass grafting treated over a 10-year period (1981-1991). Angioplasty was technically successful in 85% of 122 nonoccluded native vessels and in 86% of 50 saphenous vein grafts. Two patients (1.4%) had a myocardial infarction and there were three procedure-related deaths (2.1%). The cumulative probability of survival was 91.5% and 74.5% at 1 and 5 years, respectively. Survival free from myocardial infarction and repeat bypass grafting at 1 and 5 years was 77.3% and 53.9%, respectively. At census, 31% of the 117 survivors were asymptomatic, and 47% were improved by at least two angina grades. Coronary angioplasty provides an apparently safe and effective alternative method of revascularization in selected patients with prior coronary artery bypass grafting. This treatment strategy potentially avoids reoperation with its attendant risks.
Arteriovenous fistulas affecting the mesenteric circulation are rare. To our knowledge, this is the first case report in which a large fistula was initially treated by steel coil embolization and, after failure of this procedure, subsequently surgically corrected. A case is reported and the literature reviewed.
A retrospective study was performed on 111 consecutive primigravidae aged 35 and above (study group) who delivered in the Gynaecological Oncology Department, Kandang Kerbau Hospital, Singapore during the two-year period (1990 and 1991). For comparison, all the 10,189 patients in the department who were delivered during the same time period were also analysed and served as the control group. The aim of the study was to examine the risks involved with advanced maternal age, the obstetric performance and neonatal outcome of both groups in the context of modern obstetric care in Singapore. In the study group, pre-eclampsia was the commonest antenatal complication (17.1%), followed by preterm labour (16.2%) and diabetes mellitus (including impaired glucose tolerance test) (16.2%). In the control group, the corresponding incidences were 10.8%, 6.3% and 2.8% respectively. The incidence of labour induction (28.8%) and instrumental deliveries (31.5%) were higher in the study group than in the control group (7.1% and 7.3% respectively). The Caesarean section rate was twice as common in the study group (32.4%) than in the control group (16%). Only 15 patients (13.5%) had amniocentesis performed. The majority of patients (41.5%) who did not have amniocentesis were 35 years of age at delivery. The perinatal mortality rate of the study group was similar to that of the control group. There were no maternal deaths.
Both beta thalassaemia and HbE disease are microcytic red cell disorders. Pregnancy however induces macrocytosis which makes screening with the mean cell volume (MCV) difficult in antenatal patients. In addition, population screening for HbE has not been widely reported in the literature and the screening criteria for beta thalassaemia may not necessarily apply. A study of the value of the MCV for routine screening for both beta thalassaemia and HbE traits in 3696 antenatal patients of different gestational ages was carried out. All patients with an MCV < or = 80 fL received confirmatory tests for haemoglobinopathies. The MCV rose by only 2.0% in pregnancy. A total of 494 patients (13.4% of the general population) had an MCV < or = 80 fL. Of these microcytic patients, 11.3% (56) and 4.7% (23) were eventually confirmed to have beta thalassaemia and HbE traits respectively. The mean MCV for the 3696 antenatal patients was 87.8 fL (SD 7.5) compared to patients with beta thalassaemia and HbE traits, which were 67.5 fL (SD 4.5) and 75.7 fL (SD 4.1). HbE traits were less microcytic than beta thalassaemia traits and overlapped significantly with the general population. Beta thalassaemia trait and HbE trait detected by this screening method constituted 1.52% and 0.62% respectively of the total antenatal population screened. The MCV remains a valid screening parameter in pregnancy for beta thalassaemia trait. As for HbE trait, applying a discriminant value of 80 fL to the MCV in the population screening would miss a significant proportion of the HbE traits.(ABSTRACT TRUNCATED AT 250 WORDS)
OBJECTIVE: To study the determinants of success of coronary angioplasty in patients with chronic total occlusions, and to formulate a multiple logistic regression model to improve selection of patients. DESIGN: A retrospective analysis of clinical and angiographic data on a consecutive series of patients. PATIENTS: 312 patients (mean age 55, range 31 to 79 years, 86% men) who underwent coronary angioplasty procedure for a chronic total occlusion between 1981 and 1992. RESULTS: Procedural success was achieved in 191 lesions (61.2%). A major complication occurred in six patients (1.9%). Multiple stepwise logistic regression analysis identified the presence of bridging collaterals (p < 0.001), the absence of a tapered entry configuration (p < 0.001), estimated duration of occlusion of greater than three months (p = 0.001), and a vessel diameter of less than 3 mm (p = 0.003) as independent predictors of procedural failure. The logistic regression model was used to classify patients into groups of high, intermediate, and low probability of procedural success with cut off points of 70% and 30%. The predictive value for procedural success (probability > or = 70%) was 91% (95% confidence intervals (95% CI) 83% to 96%) and predictive value for procedural failure (probability < 30%) was 81% (95% CI 64% to 92%). CONCLUSIONS: Percutaneous transluminal coronary angioplasty of chronic total occlusions is associated with a low risk of acute complication. Procedural success is influenced by easily identifiable clinical and angiographic features and the multiple regression model described may help to improve selection of patients.
We report of a 39 years old patient with a large testicular tumor found during an examination for infertility. The tumor consisted of a spermatocytic seminoma (SS) and a differentiated teratoma (TD). Furthermore, two small foci of seminoma were seen in the surrounding testicular tissue, several testicular tubuli contained carcinoma in situ (CIS). The diagnosis was based on the results obtained with various immunohistochemical markers: keratin, vimentin, desmin, LCA, CD3, CD20, CD45R, ferritin, PLAP, AFP. On the basis of the macroscopic and histopathological features, we propose the following etiology: CIS progressed in an earlier phase to the (larger) TD and later to the (smaller) classical seminoma; likewise, in an earlier phase, SS developed from a still unknown precursor stage. Our case of a mixed tumor as well as other cases reported in the last years do not allow the explanation of a differing etiology for SS. On the contrary, it may be presumed that the origins of seminoma and teratoma on the one hand and SS on the other hand are less divergent than hitherto thought.
The management of 159 consecutive women with singleton breech presentation occurring at 37 or more weeks of gestational age was reviewed. They were stratified into three groups: (a) caesarean section without trial of labour (87), (b) trial of labour resulting in caesarean section (21), and (c) trial of labour culminating in successful vaginal delivery (51). The criteria for allowing a trial of labour were described. Careful review of material and foetal variables indicated that a trial of labour in carefully selected patients resulted in vaginal delivery in 70.8% and that this was achieved without an increase in foetal or maternal mortality or morbidity.
The year 1928 marked the beginning of the mental health service in Singapore. From a large asylum which provided mainly custodial care the mentally ill were managed by a handful of expatriate medical pioneers and nurses. Drugs were limited and hospitalisations lasted years. The scene has changed tremendously over the last six decades. Today the Mental Health Service in Singapore is largely provided by the public sector with contributions from private and voluntary organisations. It provides a comprehensive and integrated programme consisting of both hospital-based and community-based treatment programmes with the objectives to promote good mental health for everyone as well as to provide the best possible treatment for those afflicted with mental illnesses of all types. With the rapid development of community-based mental healthcare, several changes have taken place to reflect this trend. Besides introducing a wide range of community support services and greater liaison with primary care givers, the need to educate medical students and doctors, members of the public, people involved in healthcare in the voluntary sector and others about mental health and illness has been recognised to be an important component in the delivery of good mental healthcare. As a step forward the National Mental Health Programme has been launched by the Ministry of Health in 1993 to further improve the mental health service that is currently available (Fig 1). The newly established Institute of Mental Health will serve as the education, training and research arm of the National Mental Health Programme. Together with the new Woodbridge Hospital, mental healthcare in the future will be professionally organised, coordinated and community-orientated.
A retrospective study in the use of Kielland's Forceps for rotation of the foetal head and mid-cavity delivery in Kandang Kerbau Hospital, Singapore from 1987-1990 is presented. Out of a total of 53,889 singleton births during this period, Kielland's Forceps was used for delivery in 137 (0.25%) patients with an incidence of 0.65% in the primiparae and 0.07% in the multiparae. Primiparity, induction of labour and epidural analgesia were associated with a significantly higher incidence of rotational delivery by Kielland's forceps. The success rate of Kielland's forceps delivery was 93.4% (128 of 137). There was no maternal or perinatal mortality. About one-third of the mothers experienced postpartum morbidity, commonest being retention of urine, postpartum haemorrhage and vaginal lacerations. Traumatic injuries were present in about one-quarter of the babies and were minor. Out of a total of 306 mid-cavity deliveries for occipito-transverse malposition, Kielland's forceps accounted for 38.2% (117), vacuum extraction 30.7% (94), manual rotation followed by Neville-Barnes forceps 11.1% (34) and Caesarean section 20.0% (61). The junior specialists tended to use vacuum extraction for rotational delivery more than the senior specialists.