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Biomedical subjects

A T Tan

Publications and source records attributed to A T Tan.

At least 37 records · Page 2Linked to original sources
PubMed1991

Pacing experience with the atrial screw-in leads at the Singapore General Hospital.

This is a retrospective study of atrial screw-in leads implanted at the Singapore General Hospital from January 1988 to August 1990. There were 21 (13 female and 8 male) consecutive patients, with age ranging from 17 to 79 years (mean 55 years). Thirteen patients had sick sinus syndrome and the remaining eight patients had high grade AV block. Eleven patients had AAI, six had DDD and four had DDDR pacing modes respectively. Three different models of unipolar screw-in leads were used. Eight patients had Medtronic Model 6957, seven had Medtronic Model 4057 and six had Siemens-Pacesetter Model 1007 pacing leads implanted. At the time of implant, the measured P wave amplitudes ranged from 1 to 4.8 mV (2.5 +/- 1.1 mV) and the pacing thresholds ranged from 0.5 to 2.3 volts (1.21 +/- 0.51 volts). There were no acute complications at the time of implant. On follow-up ranging from one month to two years, two patients had inadequate sensing in the atrium and one patient had high pacing threshold. There were no lead dislodgement. In conclusion, these screw-in leads can be safely used in the atrium with acceptable pacing characteristics.

Adolescent↗
PubMed1990

Nuclear cardiology in the detection of coronary artery disease--an overview of its role in the Singapore General Hospital.

Nuclear cardiology at the Singapore General Hospital (SGH) had a humble beginning in 1983 when it was carried out by the joint staff of the departments of cardiology and nuclear medicine. At the onset the bulk of the scans were blood pool studies. In 1984, qualitative tomographic myocardial perfusion studies replaced the less accurate planar scans and this was carried out on a routine basis. Its superiority to conventional exercise electrocardiography in the detection, management and prognostication of coronary artery disease (CAD) has since been validated locally. We have since progressed to the fields of research involving pharmacological stress testing with intravenous dipyridamole and use of technetium-based isonitrile as an alternative to the conventional myocardial perfusion agent, thallous chloride. Our results mirror those from other research centres. On this encouraging note we are looking into newer areas such as the role of diastolic function for early detection of cardiac disease. In under a decade we are in a position to provide scintigraphic service expected of an established nuclear cardiac laboratory. This article provides an overview of our work in the management of CAD.

Coronary Disease↗
PubMed1990

Coronary angioplasty in ischaemic heart disease.

Since its inception a decade ago, Coronary Angioplasty has been shown to be an effective and increasingly preferred method of coronary revascularisation. In order for all physicians involved in the care of cardiac patients to be aware of the relatively new technique we have discussed the indications, advantages and limitations of Coronary Angioplasty. It is only by careful assessment of the patient, international as well as local operator experience, that the appropriate method of coronary revascularisation can be decided for the patient.

Angioplasty, Balloon, Coronary↗
PubMed1990

Felodipine as monotherapy in Asian patients with mild to moderate hypertension.

Felodipine (Plendil) is a once daily antihypertensive calcium antagonist. The present study evaluated the clinical efficacy and tolerability of felodipine as monotherapy in treating Asian patients with mild to moderate hypertension. Twenty-three males and 14 females with supine diastolic blood pressure (sDBP) above 95 mmHg after a 2-4 week placebo treatment period were included in the study. Active treatment was initiated with felodipine 10 mg once every morning for 2 weeks. The dose was titrated stepwise with increments of 10 mg every two weeks if BP was greater than the target DBP of 90 mmHg. The optimum dose was then maintained for at least 4 months during which the patients returned for 2 weekly follow-up visits. At each visit, supine and standing blood pressure and heart rate (HR) were measured after dosing. Any adverse events were recorded when they occurred. Blood chemistry was checked before and at 4 weeks after starting felodipine treatment and at the end of the study. The target DBP was achieved in all 37 patients, 25 with 10 mg, 11 with 20 mg and 1 with 30 mg. The supine BP was reduced to 127 +/- 10/83 +/- 5 by felodipine which was significantly lower than the pre-treatment BP (151 +/- 16/103 +/- 8, p less than .001). The BP control was maintained at the end of the study period (124 +/- 12/82 +/- 6). No significant changes in heart rates were detected after felodipine treatment. Side effects attributable to vasodilation were observed in 10 patients (transient headache in 8 and mild ankle oedema in 2), none requiring withdrawal of the drug. We conclude that felodipine 10-20 mg given once daily is an effective and well-tolerated monotherapy for the treatment of mild to moderate hypertension.

Adult↗
PubMed1990

Thrombolytic therapy in myocardial infarction.

Since its reintroduction in 1979, the administration of streptokinase for the treatment of myocardial infarction has revolutionised the management of this common condition. Intracoronary, and subsequently intravenous infusion of this lytic agent have been shown to recanalise the totally occluded infarct related vessel. Overall mortality reduction was 18% when it was administered intravenously in the GISSI study. The survival advantage has been maintained over 1-2 years. The addition of aspirin has increased the survival rate, as reported in the ISIS-2 study. Recombinant tissue plasminogen activator, a clot specific agent, achieves a higher patency rate when compared to streptokinase, besides favourably influencing survival. Both drugs also improve left ventricular function. Complications include a 0.5-1% incidence of intracranial haemorrhage, as well as a small risk of major bleeding. Although the incidence is low, reinfarction is increased after thrombolytic therapy. Hence, some form of assessment of residual myocardial ischaemia should be performed. Routine PTCA after thrombolysis has not been shown to be of additional benefit. The introduction of more potent and clot specific drugs without unwanted side effects are eagerly awaited.

Animals↗
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

The use of intravenous streptokinase (SK) in a peripheral hospital in the treatment of acute myocardial infarction.

We report our early experience in the use of intravenous Streptokinase in acute coronary occlusion in a peripheral hospital. From 1st November 1988 to 20th July 1989, 30 patients were treated with Streptokinase. The hospital mortality was 1/30 (3.3%) from a non-streptokinase related event. The commonest complication following streptokinase infusion was transient hypotension, affecting 10/30 patients. From a total of 30 patients, 3 had transient bleeding complications and was self limiting. Follow up coronary angiograms were performed on 17/30 patients, demonstrating a patent infarct related artery in 12/17 patients (70.6%). We concluded that it is both feasible and safe to use intravenous streptokinase in a peripheral setting in the treatment of acute myocardial infarction.

Adult↗
PubMed1990

Mortality trends in the coronary care unit.

To evaluate the clinical features, complication rates, and mortality from infarction in the coronary care unit, we analysed all cases of acute myocardial infarction admitted to the Coronary Care Unit of the Singapore General Hospital over a 4 month period in 1988. There were 184 cases of acute infarction with a male:female ratio of 3.4:1. Fifty-five percent of patients were aged 60 years or above. Complications included congestive cardiac failure in 40%, sustained ventricular tachycardia in 9%, cardiogenic shock in 18% and complete heart block in 8%. The overall in-hospital mortality was 20.6%. Multiple logistic regression analysis of clinical variables showed that of the clinical variables, age (elderly patients) and the diabetes were independently associated with a higher mortality as well as development of cardiogenic shock and sustained ventricular tachycardia. Comparing our results with previous smaller studies of CCU outcome in 1975 and 1967, there was a marked increase in the proportion of elderly patients in 1988 but despite this the overall mortality rate was not significantly different. Age is the most important clinical variable predicting outcome from infarction.

Adult↗
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↗
PubMed1990

Anti-arrhythmic surgery for atrioventricular junctional and atrioventricular re-entrant tachycardia--a report of six cases.

Since 15th March 1989, six patients with recurrent supraventricular tachycardia (SVT) had antiarrhythmic surgery performed. There were 4 males and 2 females, ages ranged from 23 to 62 years (mean 41 years). Two of these patients with the Wolff Parkinson White (WPW) syndrome also had syncope. Five of these patients had atrioventricular re-entrant tachycardia (AVRT) involving the bypass tracts. Two patients with the WPW syndrome had persistent antegrade conduction, two had intermittent conduction and the last patient had no antegrade conduction via the bypass tract. The bypass tracts were localised at the left free wall in all the five patients. Only one patient had atrioventricular junctional re-entrant tachycardia (AVJRT) of the slow-fast type. The indications for surgery for these patients include failed medical therapy, "dangerous" arrhythmias and patient's preference. All the patients had surgery performed using the endocardial dissection technique on the cardioplegic heart. There were no perioperative mortality and morbidity. All the patients were discharged within 2 weeks. To date, none of the patients had clinical recurrence of SVT and only one patient remained in atrial fibrillation and is on digoxin. In conclusion, antiarrhythmic surgery should be considered for patients with "symptomatic" palpitations as it is curative with a resumption to normal life.

Adult↗
PubMed1990

Permanent pacemaker trends in Singapore General Hospital in the eighties.

This is a ten year survey of all the pacemakers implanted in the Department of Cardiology, Singapore General Hospital, from January 1980 to July 1989. There were 331 (164 male and 167 female) patients with pulse generators and leads implanted. The ages of the subjects ranged from 8 to 91 years (mean 63 years). Two-thirds of the patients were greater than 60 years. The indications for pacemaker implants were high grade atrioventricular block in 199 (60%) patients, sick sinus syndrome in 112 (34%) patients and in the remaining 20 (6%) of patients, no data was available, 298 (90%) patients had VVI pacing (133 were non-programmable and 165 were programmable pacemakers), 8 (2%) had AAI, 16 (5%) had DDD and the remaining 9 (3%) had VVIR mode of pacing. 282 (85%) of the patients had new pacemakers implanted while the remaining 49 (15%) patients had pacemaker replacements. At the time of replacement of pacemakers, 23 patients had upgrade of their non-programmable to programmable VVI pacemakers and 4 to DDD and VVIR pacing modes respectively. Furthermore, 293 (88%) patients had endocardial leads as compared to 38 (12%) with epicardial leads. In conclusion, most of the patients who require pacemaker implants will continue to have single chamber system. However, to improve longevity of the pacemakers, one should consider using low pacing threshold leads and programmable pacemakers.

Adolescent↗
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↗