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Biomedical subjects

K W Lau

Publications and source records attributed to K W Lau.

At least 37 records · Page 2Linked to original sources
PubMed1999

Intracardiac echocardiography via the transvenous approach with use of 8F 10-MHz ultrasound catheters.

OBJECTIVE: To study the safety and feasibility of intracardiac imaging using a novel 8F 10-MHz non-over-the-wire ultrasound catheter system. SUBJECTS AND METHOD: Intracardiac imaging using a transfemoral venous approach was performed in 33 adults, 14 men and 19 women, aged 25 to 66 years (mean, 46 years). Six were normal subjects, 12 had congenital heart diseases (5 atrial septal defects, 3 ventricular septal defects, 1 tetralogy of Fallot, 2 patent ductus arteriosus, and 1 Ebstein anomaly), 14 had valvular heart diseases (12 mitral stenoses and 2 calcific aortic stenoses), and 1 had acute pulmonary embolism. RESULTS: Ultrasound images were obtained, without any complications, from the right side of the heart in all subjects. The atria and ventricles could be recognized by anatomic relationships to the cardiac chambers and the valves by their characteristic motion during each cardiac cycle. The vessels were verified by their connections to the cardiac chamber and by contrast echocardiography if indicated. CONCLUSION: Intracardiac imaging using the 8F 10-MHz non-over-the-wire ultrasound catheter system via a transfemoral venous approach is feasible and safe. Intracardiac echocardiography is potentially useful for assessing a variety of cardiac anomalies and in guiding and monitoring certain intervention procedures.

Adult↗
PubMed1999

Large granular lymphocytic leukemia in a mixed breed dog.

A mixed breed dog was diagnosed with large granular lymphocytic leukemia. Immunophenotypic analysis indicated the lymphocytes were CD3+, CD8+ T cells expressing the alpha beta T cell receptor and a leukointegrin, alpha d. Chemotherapy and splenectomy resulted in an initial reduction in the lymphocyte count.

Animals↗
PubMed1998

Ki-ras codon 12 point mutational activation in Hong Kong colorectal carcinoma patients.

This study investigated the frequency and importance of Ki-ras codon 12 mutations in 99 Hong Kong Chinese colorectal carcinoma specimens by allele-specific oligonucleotide hybridization. The frequency of mutations detected was 30% and the most common mutation observed resulted in aspartic acid substitutions. Previous studies showed that specific Ki-ras mutations have been significantly associated with prognosis. Ki-ras codon 12 point mutational activation in CRC was significantly associated with the differentiation status of tumors in this study. Ethnic differences in the patterns of Ki-ras codon 12 point mutations were observed.

Adult↗
PubMed1998

Early experience with the NIR intracoronary stent.

Immediate and midterm results of 61 NIR stent placement attempts in 55 native coronary vessels in 52 patients demonstrate a high clinical success rate of 98%, no early stent thrombosis, and a 5-month angiographic restenosis rate of 23%. The frequency of in-stent restenosis was significantly heightened in small vessel sizes and in diabetic patients.

Angioplasty, Balloon, Coronary↗
PubMed1998

Long-term (36-63 month) clinical and echocardiographic follow-up after Inoue balloon mitral commissurotomy.

Although Inoue balloon mitral commissurotomy (BMC) offers excellent short-term results, there remains a paucity of data on its long-term (> or =3 yr) outcome. We therefore analyzed the outcome of 68 consecutive patients who had regular long-term clinical and serial echocardiographic follow-up of > or =3 yr after successful BMC. The procedure provided significant improvements in transmitral valve gradient (13+/-6 mmHg before to 5+/-2 mmHg after BMC, P = 0.0001), left atrial pressure (21+/-6 mmHg before to 14+/-5 mmHg after BMC, P = 0.0001), and mitral valve area (0.8+/-0.2 cm2 before to 1.7+/-0.4 cm2 after BMC, P = 0.0001) without incurring > grade 2+ angiographic mitral regurgitation. At a mean follow-up of 44+/-9 mos (range, 36-63 mo), functional benefits were maintained in 91% of patients. Serial echocardiographic evaluations performed in 97% of patients revealed a restenosis rate of 15% (defined as a loss of >50% initial gain in valve area or a valve area of <1.5 cm2). No strokes or deaths were encountered. Of the 15 clinical, echocardiographic, and procedural variables analyzed in a multivariate model, only the presence of chronic atrial fibrillation was an independent correlate of restenosis (P < 0.05). It was clearly more common in patients with than those without restenosis (100% with vs. 57%, respectively, P = 0.009). In conclusion, our study shows that BMC confers maintained long-term functional benefits and a low anatomic restenosis rate 23 yr after BMC.

Adult↗
PubMed1998

Laparoscopic management of Tenchkoff catheters in continuous ambulatory peritoneal dialysis. A one-port technique.

We describe a one-port laparoscopic technique for assisting in Tenchkoff catheter placement and salvaging obstructed ones in patients requiring continuous ambulatory peritoneal dialysis (CAPD). This unique technique enables diagnostic laparoscopy, adhesiolysis, repositioning of catheters, and omentectomy to be performed without laparotomy. Six patients were treated. Only one 10-mm port was required, using an operating laparoscope and an instrument introduced through the working channel of the laparoscope. Adhesiolysis was performed under laparoscopic vision; omentectomy and flushing of blocked catheters were carried out extracorporeally. The catheters were then repositioned to the pelvic cavity under laparoscopic vision. All patients were followed up for 6-10 months. No mechanical problem was noticed. Our one-port laparoscopic technique is a simple and effective method for treating patients who have mechanical problems with their peritoneal dialysis catheters.

Adult↗
PubMed1998

Midterm angiographic outcome of single-vessel intracoronary stent placement in diabetic versus nondiabetic patients: a matched comparative study.

BACKGROUND: It remains controversial whether diabetes is associated with an increased risk of restenosis after intracoronary stenting. METHODS AND RESULTS: We selected 42 diabetic patients and an equal number of nondiabetic patients with follow-up angiographic restudy after single-vessel stenting, matched for 4 important stent-related and angiographic variables (stent design, reference vessel size and expanded stent diameter, coronary vessel treated, and poststent residual diameter stenosis). The 2 patient groups did not differ in their baseline lesion severity and acute luminal gain. At 5-month angiographic assessment, the observed in-stent restenosis rate was significantly higher in diabetic than nondiabetic patients (40.5% vs 16.7%, P = 0.0157). It was highest in diabetic patients who received small stents <3.0 mm in diameter and intermediate in diabetic patients who received larger stent sizes (55% vs 27%, P = 0.0675). The frequency of restenosis in nondiabetic patients, however, was low; it was 18% and 15% in those who received small stents and larger stents, respectively (P = 0.7823). CONCLUSIONS: Our data suggest that diabetes predisposes to an increased risk of in-stent restenosis, particularly in small vessels.

Coronary Angiography↗
PubMed1998

Goldberger's triad in dilated cardiomyopathy--can it predict the severity of left ventricular dysfunction?

Goldberger's triad is a specific, but relatively insensitive, electrocardiographic sign for dilated cardiomyopathy. To study the correlation between the presence of this sign and the severity of left ventricular dysfunction, the electrocardiograms and echocardiographically-determined left ventricular parameters of 17 patients (mean age 59.3 +/- 11.8 years) with dilated cardiomyopathy were examined. Five of the patients had Goldberger's triad. We found that the mean left atrial diameter, the mean left ventricular internal diameters (both end-systolic and end-diastolic) and the mean left ventricular ejection fraction of the group of patients with Goldberger's triad did not differ significantly from the group without. Coronary angiography revealed occult coronary artery disease in 5 of 12 patients. A larger, prospective study is required to verify our finding.

Cardiomyopathy, Dilated↗
PubMed1997

p16 tumor suppressor gene mutations in Chinese esophageal carcinomas in Hong Kong.

The frequency and nature of genetic alterations in the p16 tumor suppressor gene in 25 esophageal squamous cell carcinoma specimens from Chinese patients were investigated by PCR-SSCP and DNA sequencing techniques. No gross deletions occurred in either exon 1 and 2 of the gene by PCR amplification. However, genetic changes were observed in three cases. These included a point mutation in codon 12 of exon 1 with a resulting Ala --> Thr amino acid substitution, a point mutation at base 91 in the non-coding region of exon 1, and a 1 base pair insertion in codon 116 of exon 2. The low mutation frequency of 12% is consistent with that of three previous studies involving Japanese and Caucasian patients (8, 16 and 21% frequency: Esteve et al., 1996, Igaki et al., 1995 and Zhou et al., 1994). p16 gene mutations do not appear to play a major role in esophageal carcinogenesis.

Aged↗
PubMed1997

Transradial coronary angiography and angioplasty in Chinese patients.

Radial artery punctures for diagnostic coronary angiography or coronary balloon angioplasty were performed in 211 patients with a success rate of 98% (207 patients). In the four failed transradial accesses, the procedure was accomplished via the transfemoral route. Major local vascular complications included one arteriovenous fistula, one pseudo-aneurysm, and one ischemic contracture of the right hand. Reduced radial pulses were noted in 25 (12%) patients at follow-up without ischemic manifestations. Transradial diagnostic coronary angiography was successfully completed in 184 (98%) of 187 patients. The technical success for balloon angioplasty was obtained in 73 (97%) of 75 patients. Clinical success was observed in 68 (91%) patients; balloon angioplasty resulted in one nonfatal myocardial infarction and four late deaths (3 cardiac and 1 stroke). We believe that transradial catheterization for diagnostic coronary angiography and balloon angioplasty in our relatively small built Chinese population is a safe and practical alternative approach.

Adult↗
PubMed1997

Percutaneous transvenous mitral commissurotomy versus surgical commissurotomy in the treatment of mitral stenosis.

There is no doubt that percutaneous transvenous mitral commissurotomy (PTMC) in experienced centers is associated with a low risk of major complications and yields excellent immediate and long-term outcome. Although previous observational studies on both PTMC and surgical commissurotomy have indicated similar outcome between the two treatment strategies in terms of valve area improvement and risk of major complication (death, thromboembolism and significant resultant mitral regurgitation), it was not until recently that several prospective randomized trials comparing the two procedures and involving > 470 patients with favorable valve characteristics (pliable, noncalcified valve with mild subvalvular disease and no or mild mitral regurgitation), have confirmed that PTMC is indeed just as, if not more, effective as surgical commissurotomy. The late restenosis rate at up to 3-year follow-up appears comparable. Furthermore, PTMC has other additional benefits. It is nontraumatic, may be repeated without additional risk, and has been shown to be an extremely useful and efficacious palliative tool in those with end-stage mitral stenosis or with unfavorable valve anatomy who refuse surgery, and in certain subset of patients at high surgical risk because of medical comorbidities.

Angioplasty, Balloon, Coronary↗
PubMed1997

Safety and efficacy of angiography-guided stent placement in small native coronary arteries of < 3.0 mm in diameter.

BACKGROUND AND HYPOTHESIS: Increased operator experience, greater insight in stent deployment techniques, and improved poststent medication regimen have significantly reduced the risk of thrombotic stent closure following stent placement in large coronary arteries (> or = 3.0 mm in diameter). Whether equally favorable results are afforded by stent placement in small vessels (< 3.0 mm), however, remains unclear. Accordingly, the aim of this study was the specific examination of the risk of stent placement in small native coronary vessels, using stent deployment technique consisting of supplementary dilatations with larger balloons or high-pressure inflations, and aggressive aspirin-ticlopidine and short-term oral anticoagulation poststent therapy. METHODS: Forty-seven balloon-expandable stents (20 Gianturco-Roubin, 21 NIR, 6 Palmaz-Schatz) were successfully implanted without intravascular guidance in 45 native coronary arteries (mean reference diameter of 2.5 mm) in 44 consecutive patients (31 men, 13 men), the majority of whom (87%) were stented for the treatment of failed or suboptimal balloon angioplasty outcome. RESULTS: Successful stent placement reduced the lesion diameter stenosis from 91 +/- 9% to 3 +/- 7% (p = 0.0001). There were no early stent thrombosis or major cardiovascular events prior to hospital discharge. During a 12-month follow-up period, most patients remained symptomatically improved and no myocardial infarction, stroke, or death was observed. Five-month angiographic reassessment revealed an in-stent restenosis rate of 41%, which was higher in vessels < or = 2.5 mm in size (47 vs. 33% for vessels > 2.5 mm, p = 0.2747). CONCLUSIONS: In selected patients with small native coronary vessels < 3.0 mm in diameter, angiography-guided optimal stent placement is associated with a low risk of stent thrombosis and bleeding complications. However, the in-stent restenosis rate is high with the stents used in this study.

Angioplasty, Balloon, Coronary↗
PubMed1997

p53 mutations detected in colorectal carcinoma patients in Hong Kong.

A mutational spectrum for exons 5-8 of the p53 tumor suppressor gene in colorectal carcinomas in Hong Kong Chinese was established. Ninety-nine colorectal carcinomas from Hong Kong patients were analyzed for mutations in p53 gene by PCR-single-strand conformation polymorphism analysis and direct DNA sequencing. Thirty-five of the 99 tumors (35.4%) contained mutations. Point mutations accounted for 80% of all genetic changes and were predominantly base transitions at CpG dinucleotide sites, mutations that were also predominant in Caucasian carcinomas. The major hot spots at codons 175 and 248 of p53 in Caucasians are also hot spots in the Chinese gene. Identical mutations in codons 152 and 306 were detected in two independent tumors in the Chinese, which were reported only rarely in Caucasians. Moreover, a significantly higher frequency (20%) of deletion and insertion mutations was observed in Hong Kong colorectal cancer patients. Distinct genetic and/or environmental factors may contribute to these findings.

Adult↗