Biomedical subjects
Publications and source records attributed to H C Tan.
The electrocardiographic patterns in leads V7, V8, and V9 were studied in 225 young, normal men (age range 17 to 21 years). The prevalence of 0.5- to 1.0-mm ST-segment elevation in leads V7, V8, and Vg 0.08 second after the J point was 8.9%, 5.8%, and 3.1%, respectively; the ST-segment elevation was not >1.0 mm in any subject.
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A syndrome akin to graft-versus-host disease in the recipient of syngeneic stem cells is hitherto described as being milder, self-limiting and confined to the skin. It is enhanced by prior cyclosporin A therapy. We describe here a recipient of a syngeneic marrow transplant who did not receive priming with cyclosporin A and yet developed severe and progressive graft-versus-host disease which necessitated and responded to high-dose immunosuppressive therapy. We believe that this is because the conditioning regimen in stem cell transplant acts to reset the immune system enabling it to recognise 'self' antigens. Bone Marrow Transplantation (2000) 25, 205-207.
We review our cases of leukemia and lymphoma relapse after allogeneic marrow transplant and describe here a series of 10 patients with extramedullary (EM) relapse. In the 13 relapses in acute myeloid leukemia, 5 cases had EM involvement. There were 3 EM involvement out of 13 acute lymphoblastic leukemia relapses, one EM disease in 11 chronic myeloid leukemia relapses and one case of lymphoma with EM relapse. A common observation is that in some of these cases, EM relapse occurred in the presence of continuous marrow remission, In those cases with both marrow and EM involvement marrow remission could often be achieved and maintained temporarily while EM disease progressed despite chemotherapy or immunotherapeutic measures such as immunosuppressant withdrawal and donor lymphocyte infusion. Survival in partial remission after relapse could be prolonged in some cases but eventual death from progressive disease was often the case.
BACKGROUND: Abciximab, a monoclonal antibody to platelet glycoprotein IIb/IIIa receptor, has been shown to be effective in reducing ischemic complications after coronary angioplasty in recent trials. However, little is known about its efficacy and safety when used in Asian patients. METHODOLOGY: Based on our abciximab registry, we performed a retrospective analysis of 115 Asian patients who received the antiplatelet agent while undergoing percutaneous coronary intervention in our centre. They constituted 18.4% of the total number of patients undergoing percutaneous revascularisation during the corresponding period. The majority of the patients were males (84%). The mean age of the cohort was 54 and the mean weight was 70 kg. The ethnic composition of the study population was: Chinese 54%, Indians 21%, Malays 19% and Others 6%. All patients received aspirin 100 mg and weight-adjusted heparin before the procedure. Abciximab may be administered on a preplanned basis prior to the procedure or be given as a 'bailout' strategy. RESULTS: There was a high clinical success rate of 95.8% and low incidence of ischemic complications when abciximab was given during coronary angioplasty. There were 0% Q myocardial infarction, 3.3% non-Q myocardial infarction and 0.8% death in our series. Bleeding complications were uncommon at 7.6%, predominantly involving the groin and gingiva. Thrombocytopenia occurred in 5.8% of patients. Abciximab was noted to increase the procedural activated clotting time (ACT) by 38 seconds when given concomitantly with heparin. The mean maximal procedural ACT achieved was 323 +/- 51 seconds. CONCLUSIONS: Abciximab may be used safely and efficaciously in Asian patients undergoing coronary angioplasty. The drug confers protection against ischemic complications during the procedure whether it is administered electively or as a 'bailout'. There is however, a need to redefine the heparin regime for our patients, given the high ACT obtained when abciximab is administered.
BACKGROUND: Minimally invasive cardiac surgery is a new and promising approach to the treatment of coronary artery disease allowing surgery to be performed through smaller incisions with lesser morbidity. METHODOLOGY: From November 1995 to February 1997, ten minimally invasive direct coronary artery bypass (MIDCAB) grafts were performed. The left internal mammary artery was used to bypass the left anterior descending coronary artery (LAD) through a limited left anterior thoracotomy. PATIENTS: There were seven males and three females and their ages ranged from 42 to 72 years (mean = 60 years). Two patients had prior interventional procedures. Cardiopulmonary bypass was used in the first two patients. Two patients were converted to conventional surgery early in the series. RESULTS: There was no mortality nor major morbidity. Mean post-operative hospital stay was seven days. To date, three patients have had post-operative angiography confirming the patency of the left internal mammary artery to LAD anastomosis. CONCLUSION: Early results of the MIDCAB procedure are encouraging. However, the definitive place of such procedures awaits longer term follow-up.
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An 88-year-old man presented with acute Q wave inferior, posterior and right ventricular myocardial infarction which was associated with intermittent complete right and left bundle branch block.
Six patients with complete left bundle branch block and an increase in the transverse:frontal plane QRS voltage ratio are described. All these patients presented with congestive heart failure which was due to severe left ventricular dysfunction.
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Twelve lead electrocardiograms together with right-sided chest leads V4R, V5R and V6R were recorded in four patients with acute pulmonary embolism. All four patients showed ST segment elevation and a qs or qr pattern (with prominent q waves) in one to three of the leads V4R, V5R and V6R. These abnormalities were absent in the repeat electrocardiograms which were recorded after the acute illness.
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Platelets play a key role in the pathogenesis of atherosclerosis, acute coronary syndromes and ischaemic complications following percutaneous coronary intervention. More recently, the platelet glycoprotein (GP) IIb/IIIa receptor has been identified as the pivotal mediator of platelet aggregation, leading to thrombus formation. This has led to the emergence of a novel class of potent antiplatelet agent, the GP IIb/IIIa receptor antagonists. These agents show great promise in reducing ischaemic complications of coronary angioplasty and acute coronary syndromes. This review summarizes the current state of knowledge of the biology of GP IIb/IIIa receptor, the different classes of GP IIb/IIIa receptor antagonists, the results of the various trials, and their impact on current clinical practice.
This is a case of an unusual electrocardiographic manifestation of a patient with right ventricular (RV) myocardial infarction occurring in association with left ventricular inferoposterior myocardial infarction. There was massive ST-segment elevation in the precordial leads resembling that of an anterior myocardial infarct in addition to the ST-segment elevation seen normally in right ventricular leads. Two-dimensional echocardiography confirmed right ventricular hypokinesia and coronary angiography revealed single-vessel coronary artery disease involving the right coronary artery. It served to remind us that the presence of diffuse and massive ST-segment elevation in the precordial leads in a patient with inferior myocardial infarction may indicate simultaneous RV infarction and warrants further confirmatory tests.
In order to detect and type dengue viruses in serum specimens, four type-specific downstream primers were designed for use with a consensus upstream primer in a reverse transcription and polymerase chain reaction (RT-PCR) assay. RT-PCR using these five primers amplified NS3 gene fragments of diagnostic sizes of 169, 362, 265 and 426 base pairs for dengue virus types 1, 2, 3 and 4, respectively, but not for Japanese encephalitis, Kunjin and yellow fever viruses. The conventional two-step RT-PCR procedure was simplified by combining RT and PCR in a single-step format with a "hot start". This RT-PCR protocol was applied successfully to dengue virus-spiked serum and dengue patient serum samples, and could detect as few as one PFU of dengue virus. This assay offers a rapid, specific and sensitive molecular technique for the simultaneous detection and typing of dengue viruses.
Pseudomonas pseudomallei isolates from 62 human, 17 animal, 3 soil and 3 water samples were examined by genomic DNA digestion with PstI. Five major (RE I, II, III, IV, V) reproducible restriction patterns were observed, with most (56/62) of the human isolates displaying RE I (30/62), II (5/62), III (15/62), IV (4/62), V (2/62), and the animal (16/17), soil (2/3), water (3/3) isolates showing predominantly RE II profiles. Six human and one soil isolates showed patterns different from those of RE I to V. Restriction endonuclease analysis may be applied in epidemiological studies of melioidosis.
Duplex ultrasonography is a safe, accurate, efficient, inexpensive, noninvasive diagnostic test for deep vein thrombosis (DVT). The sensitivity and specificity of this technique is comparable to venography in symptomatic patients in many studies. The diagnostic accuracy of this test can be further enhanced by serial studies. We report our experience with the use of this technique for study of 180 patients with clinically suspected DVT. Only 55 (30.6%) patients were confirmed to have DVT on duplex ultrasonography which illustrates the inaccuracy of bedside diagnosis of this potentially life-threatening condition. Almost all our DVT patients have proximal vein involvement, indicating that venous thrombosis usually do not cause signs or symptoms until they become large, occlusive and extend into the proximal veins. It is also observed in our study cohort that half of the patients with proximal vein thrombosis has incomplete recanalisation on follow-up study. None of them with normal study developed significant sequelae of untreated DVT, suggesting that it is safe to withhold treatment based on result of this non-invasive test. Duplex ultrasonography is the diagnostic modality of choice for suspected DVT in symptomatic patients and is an excellent substitute for conventional contrast venography.
Isolated abdominal aortic stenosis resulting in bilateral lower limb claudication is uncommon in Asians. We report a 75-year-old Oriental man with isolated abdominal aortic stenosis who underwent intraluminal stenting, resulting in the abolishment of a 76 mmHg gradient. As the stenotic segment was local, only the mid-segment of the Palmaz stent was apposed to the aortic wall. Follow-up ultrasound scans showed that the partially apposed stent was potent, with no thrombosis in the free space between the stent and the wall. Hence, although aortic stenting in this patient resulted in partial apposition of the stent to the aortic wall, there was no thrombosis or migration of the stent. The patient remained symptom-free one year post-stenting. Stenting in this patient with failed balloon angioplasty was a safe and efficacious method of treating significant isolated abdominal aortic stenosis.