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Biomedical subjects

A Ng

Publications and source records attributed to A Ng.

At least 91 records · Page 5Linked to original sources
PubMed1995

Percutaneous balloon valvuloplasty in mitral restenosis after previous surgical commissurotomy.

OBJECTIVES: The aim of this study was to determine the safety profile, mitral valve outcome and follow-up functional status after percutaneous balloon mitral valvuloplasty (PBMV) in patients with mitral restenosis post-surgical commissurotomy. METHODS: Sixteen patients with symptomatic mitral restenosis after previous surgical commissurotomy underwent valvuloplasty using the Inoue balloon stepwise dilatation method. Echocardiography was performed before and after the procedure to evaluate the mitral valve area. RESULTS: All procedures were successfully completed without cardiac perforation, thromboembolism, resultant severe mitral regurgitation or death. The mitral valve area improved from 0.9 +/- 0.2 to 1.6 +/- 0.3 (p = 0.0001), accompanied by a significant immediate reduction in the left atrial pressure and transmitral gradient. Compared with PBMV in patients without past mitral surgery, patients with mitral restenosis undergoing PBMV experienced less valve area improvement but the difference was not significant (p = 0.137). Optimal valve enlargement resulting in mild mitral stenosis was achieved in 12 of the 16 patients. Midterm symptomatic benefit was observed in almost all patients. CONCLUSIONS: In view of the excellent success rate, low complication risk, the optimal haemodynamic results and favourable functional outcome afforded by mitral balloon valvuloplasty in patients with mitral restenosis after prior surgical commissurotomy, it is logical that balloon mitral valvuloplasty, where available, should be the initial treatment modality in this group of patients with suitable valve morphology before considering repeat mitral surgery.

Adult↗
PubMed1995

Evaluation of the efficacy of sequential intravenous-oral administration of pefloxacin in community-acquired lower respiratory tract infections in patients with underlying conditions.

We studied the efficacy of sequential intravenous-oral pefloxacin therapy in community-acquired lower respiratory tract infection in 24 patients with one or more underlying conditions. Twenty-eight patients were enrolled into the study but only 24 patients were evaluated. There were 16 males and 8 females with a mean age of 66.9 +/- 11.2 years (mean +/- SD, range 46 to 87 years). The underlying conditions present were bronchiectasis, chronic obstructive lung disease and diabetes mellitus. Patients who were older than 70 years but without any underlying condition were also enrolled. All received 4 days of intravenous pefloxacin 400 mg twice a day followed by oral pefloxacin 400 mg twice a day for another 10 days. Assessment of success was based on clinical, microbiological and radiological improvement. Pefloxacin produced 79.2% clinical cure rate. Another 8.3% showed improvement. Pefloxacin was well tolerated. There were few adverse effects and none of the patients required a change of antibiotic. Pefloxacin was an effective and well tolerated treatment for respiratory tract infection and had the advantage of broad in-vitro antibacterial activity, twice daily dosing and sequential availability in an intravenous and oral formulation.

Administration, Oral↗
PubMed1994

Radiofrequency catheter ablation of accessory pathways: the initial experience in Singapore.

Radiofrequency catheter ablation is a recently introduced non-surgical technique for curing patients with arrhythmias as a result of conduction over an accessory pathway in patients with the Wolff-Parkinson-White (WPW) syndrome. We present our initial experience with this technique. There were 90 patients (61 males, 29 females) with a mean age of 37 +/- 14.4 years (range: 13-73 years). All except one were symptomatic with a mean duration of symptoms of 10 +/- 9.4 years (range: 0.1-40 years). The indications for catheter ablation were failure of drug therapy in 71, patient's preference in 10, increased risk of sudden death in 6 and almost incessant tachycardia in 3. The radiofrequency ablation was performed using a deflectable 7 French 4 mm tip electrode catheter positioned at the mitral or tricuspid annulus. The site of the accessory pathway was localised by electrophysiological study and radiofrequency energy applied via the tip of the catheter. There were 100 accessory pathways as 10 (10%) patients had multiple accessory pathways. There were 69 (69%) left free wall, 11 (11%) posteroseptal, 13 (13%) right free wall, 6 (6%) right anteroseptal accessory pathways and one (1%) midseptal accessory pathways. Ninety-six percent (96%) of the accessory pathways were successfully ablated on the first ablation. Two of the 4 initially unsuccessful ablations were successfully reablated, giving an overall success rate of 98%. There were no major complications. In conclusion, radiofrequency catheter ablation of accessory pathways is highly successful and safe and provides a definitive cure for patients with the WPW syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Early ambulation following diagnostic 7-French cardiac catheterization: a prospective randomized trial.

There is a paucity of randomized studies concerning transfemoral cardiac catheterization and its complications, in particular that of 7F catheterization. Accordingly, we conducted a prospective, randomized trial comparing early ambulation (group A) 6 hr after diagnostic 7F cardiac catheterization versus late ambulation (group B) the following morning. A total of 273 patients were randomized in the study; 142 in group A and 131 in group B (NS). Except for a difference in the indications for catheterization, the baseline and procedure-related parameters were similar between the 2 groups. Early hematoma (formed within 6 hr) developed in 6 (4%) and 7 (5%) patients in groups A and B, respectively (NS). Similarly, there was no difference in the incidence of late hematoma formation (2% in each group). All hematomas detected were small and required no surgical intervention or extension of hospital stay. Our data showed that early ambulation following 7F left heart catheterization is feasible and safe. The access site complication rate is acceptably low and minor in nature.

Cardiac Catheterization↗
PubMed1993

New directions in cardiovascular mapping and therapy.

Cardiovascular mapping has allowed us to fully understand the mechanisms of some of the cardiac arrhythmias and enabled us to devise new therapeutic options for them. Endocardial mapping by electrophysiological studies using three to four endocardial catheters introduced via the vein or artery to the heart allows us to directly map the electrical activity of the heart during sinus rhythm and during abnormal tachyarrhythmias. The simultaneous recording of electrical activity from the surface electrocardiogram, right ventricular apex, His bundle, high right atrium, coronary sinus, with or without a roving mapping catheter, enables us to precisely map the electrical activation sequence in the heart. This technique has been especially useful for mapping supraventricular tachycardias and the precise mapping of the accessory pathway or slow pathway potentials have now allowed us to selectively ablate them using radiofrequency energy delivered via the tip of the endocardial catheter. Intraoperative direct cardiac mapping has allowed us to reconfirm the findings of endocardial catheter mapping immediately prior to surgery. The intraoperative mapping is more precise and allows direct visualisation of the abnormal site for the surgeon to operate. Computerised mapping using multichannel recordings has facilitated mapping of the abnormal site for patients with haemodynamically unstable or nonsustained ventricular tachycardia, and thus allows the surgeon to perform surgical resection or cryoablation of the abnormal site. Cardiovascular mapping has thus enabled us not only to understand the mechanisms of cardiac arrhythmias but allows us to provide curative therapy for patients who are at risk from sudden arrhythmic death or otherwise need life long drug therapy.

Adult↗
PubMed1992

Intra-operative blood loss during elective lower segment caesarean section.

OBJECTIVE: To measure intra-operative blood loss at elective lower segment caesarean section and to compare estimated with measured blood loss. DESIGN: Prospective observational study. Blood loss was measured in patients who underwent lower segment caesarean section in the course of routine hospital activity. SETTING: Tsan Yuk Hospital (Hong Kong), which is affiliated to the University of Hong Kong, 1990-1991. SUBJECTS: Forty women (mean age 29 years) with singleton pregnancies (mean gestation 38 weeks) delivered by elective lower segment caesarean section under general anaesthesia (mean birthweight 3177 g). MAIN OUTCOME MEASURE: Intra-operative blood loss measured by the alkaline haematin method (intra-assay co-efficient of variation 2.2%). RESULTS: The mean measured blood loss was 487 ml (SE 40, range 164-1438). The mean estimated blood loss was 425 ml (SE 31) range 100-1300; mode 400). Observer error in estimating blood loss was higher if measured blood loss greater than 600 ml. One patient received a blood transfusion and another had a post-operative haemoglobin level less than 10.0 g/dl. CONCLUSION: Blood loss at elective lower segment caesarean section was usually less than 500 ml and was estimated with reasonable accuracy. However, there was a tendency to under-estimate blood loss when the measured loss exceeded 600 ml.

Adult↗
PubMed1991

Determination of disulfide bond pairs and stability in recombinant tick anticoagulant peptide.

Tick anticoagulant peptide (TAP) is a potent and selective inhibitor of blood coagulation factor Xa (Waxman, L., Smith, D.E., Arcuri, K.E., and Vlasuk, G.P. (1990) Science 248, 593-596). The 60-amino acid sequence of TAP shows limited homology to Kunitz-type inhibitors, including cysteines at positions 5, 15, 33, 39, 55, and 59. For detailed biochemical and pharmacological studies, a recombinant version of TAP (rTAP) has been produced in yeast. To determine the arrangement of the disulfide bonds, rTAP was cleaved with trypsin and chymotrypsin and the purified peptides sequenced using a gas-phase sequenator. The positions of the disulfide bonds were assigned by identifying the cycle(s) at which di-phenylthiohydan-toin-cystine was released. The specific disulfide bridges, Cys-5 to Cys-59, Cys-15 to Cys-39, and Cys-33 to Cys-55, are analogous to those in the prototype Kunitz-type inhibitor, bovine pancreatic trypsin inhibitor (BPTI). While treatment of BPTI with dithiothreitol rapidly and specifically reduced one disulfide bond, the reduction of disulfide bonds in rTAP proceeded at a slower rate and appeared to be nonspecific, reaching a maximum of two disulfides reduced. Reduced rTAP derivatized with either iodoacetic acid or iodoacetamide lost 59% of its inhibitory activity. In contrast, BPTI alkylated with iodoacetic acid inhibited trypsin half as well as the iodoacetamide derivative. Although the arrangement of disulfides in the two inhibitors is the same, their susceptibility to reduction is markedly different.

Amino Acid Sequence↗
PubMed1990

Nonfunctioning paraganglioma of the liver, gallbladder and common bile duct.

Paragangliomas are rare extra-adrenal neoplasms of neural crest origin. Although most of these lesions are of retroperitoneal origin, paragangliomas have been reported at a host of remote sites, including the urinary bladder, larynx, orbit and lung. In our review of the literature, we discovered only solitary case reports of such neoplasms involving the gallbladder and hepatic duct. We report a case of paraganglioma simultaneously involving the liver, gallbladder and common bile duct, as well as celiac and portal lymph nodes. Our findings add paraganglioma to the list of differential diagnoses for hypervascular portacaval space lesions. Furthermore, the radiographic appearance of this unusual tumor may be sufficiently distinctive to suggest the correct histologic diagnosis preoperatively.

Cholangiopancreatography, Endoscopic Retrograde↗
PubMed1990

Six-month combination chemotherapy for cervical tuberculous lymphadenitis.

A prospective study was undertaken to determine the effectiveness of a 6-month four-drug regimen in the treatment of 123 patients with cervical tuberculous lymphadenitis. The results showed that the disease was satisfactorily controlled with residual lymph nodes which did not necessitate further chemotherapy in 14.6% of patients at 3 years follow-up. Recurrence requiring further chemotherapy occurred in 3.3% of patients between 9 and 28 months. Wound sinuses occurred in 3.3% of patients and all healed with conservative treatment. The culture results and numbers of lymph nodes at presentation had no effect on outcome at 3 years. An excisional procedure was associated with a lower incidence of residual lymph nodes than an incisional biopsy. Minor gastrointestinal upset from drug treatment was common, but only 2.4% of patients needed a change of regimen. Six months of combination chemotherapy is adequate for the treatment of the disease.

Adolescent↗