Biomedical subjects

S T Lai

Publications and source records attributed to S T Lai.

At least 37 records · Page 2Linked to original sources

PubMed2001

Ascending aorta to lower limbs revascularization for reoperation via ministernotomy.

The extra-anatomic bypasses, femorofemoral or axillofemoral, have been performed in selected patients for lower extremity revascularization of aortoiliac occlusion. However, significant graft occlusion rate does exist and reoperation constitutes an increasing proportion of vascular surgery practice. We presented our experience in a high-risk patient who received bypass surgery for the third time using the ascending aorta as the source of inflow with good result.

Aged↗

PubMed2001

Combined innominate artery reconstruction and coronary artery bypass grafting.

Two patients having significant coronary artery disease with innominate artery near-total occlusion presented neurological deficit of syncope events or cerebellar and brain stem infarct. Both of them were successfully treated with one-stage reconstruction combined with aorto-carotid-subclavian bypass and coronary artery bypass grafting (CABG). While it could not be over-emphasized how to protect both myocardium and cerebrum during CABG, cerebral perfusion through the reconstructed carotid bypass graft is the key maneuver during cardiac arrest and moderate hypothermia. Hypoperfused cerebral hemispheres were both improved extensively in the follow-up angiography. The absence of cerebral deficit and the free from coronary angina suggested that surgical technique to combine innominate with coronary artery surgery is feasible with acceptable mortality and morbidity rate.

Aged↗

PubMed2001

Endovascular aortic graft exclusion of abdominal aortic aneurysm.

Endovascular repair of abdominal aortic aneurysms has evolved dramatically within the past few years. This study reports the first successful case in Taiwan area of infrarenal abdominal aortic aneurysm treated with endovascular aortic bifurcational stent-graft. Minimally invasive surgery leading to early recovery, mobilization and shortened hospital day was promising. In addition, there were no local, remote or systemic complications during a 18-month follow-up. Thus, the procedure is an attractive alternative in its potential to reduce morbidity and mortality associated with open surgical repair, especially for patients who are not surgical candidates because of comorbidities. Careful patient selection and more experiences with refined endograft models will elucidate the feasible alternative to conventional surgical repair.

Aged↗

PubMed2001

Effects of verapamil on coronary vascular resistance in rabbits: measurement with pulsed Doppler velocimetry.

BACKGROUND: Verapamil is an effective vasodilator. The purpose of this study was to investigate the in vivo effect of verapamil on coronary blood flow velocity and vascular resistance in anesthetized, open-chest rabbits. METHODS: Twenty-one male New Zealand white rabbits were anesthetized, and a 3-mm suction-type pulsed Doppler velocimeter probe was applied to the proximal part of the left anterior descending coronary artery after median sternotomy. The rabbits received intravenous bolus infusion of 4 different doses of verapamil (0.01 mg/kg, n = 5; 0.1 mg/kg, n = 5; 1 mg/kg, n = 5, and 10 mg/kg, n = 6). The percent changes in coronary blood flow velocity and coronary vascular resistance were examined. RESULTS: There was 10.0+/-1.6% increase in coronary blood flow (CBF) and 12.5+/-1.9% reduction in coronary vascular resistance (CVR) after infusion of 0.01 mg/kg of verapamil. The CBF increased 23.0+/-9.5% and CVR decreased 24.2+/-5.2% after infusion of 0.1 mg/kg of verapamil. Infusion of 1 mg/kg of verapamil induced 34.8+/-10.5% increase in CBF and 32.6+/-2.5% reduction in CVR. The CBF increased 41.1+/-14.8% and CVR decreased 45.1+/-5.4% after infusion of 10 mg/kg of verapamil. CONCLUSIONS: Compared with baseline condition, all doses of verapamil increased coronary blood flow velocity and decreased coronary vascular resistance significantly in anesthetized, open-chest rabbits.

Animals↗

PubMed2000

The cytotoxicity of corrosion products of nitinol stent wire on cultured smooth muscle cells.

Although nitinol is one of most popular materials of intravascular stents, there are still few confirmative biocompatibility data available, especially in vascular smooth muscle cells. In this report, the nitinol wires were corroded in Dulbecco's modified Eagle's medium with constant electrochemical breakdown voltage and the supernatant and precipitates of corrosion products were prepared as culture media. The dose and time effects of different concentrations of corrosion products on the growth and morphology of smooth muscle cells were evaluated with [(3)H]-thymidine uptake ratio and cell cycle sorter. Both the supernatant and precipitate of the corrosive products of nitinol wire were toxic to the primary cultured rat aortic smooth muscle cells. The growth inhibition was correlated well with the increased concentrations of the corrosion products. Although small stimulation was found with released nickel concentration of 0.95 +/- 0.23 ppm, the growth inhibition became significant when the nickel concentration was above 9 ppm. The corrosion products also altered cell morphology, induced cell necrosis, and decreased cell numbers. The cell replication was inhibited at the G0-G1 to S transition phase. This was the first study to demonstrate the cytotoxicity of corrosion products of current nitinol stent wire on smooth muscle cells, which might affect the postimplantation neointimal hyperplasia and the patency rate of cardiovascular stents.

Alloys↗

PubMed2000

Intravenous pretreatment with magnolol protects myocardium against stunning.

Magnolol, an antioxidant, has been reported to possess various protective effects on the cardiovascular system. However, its effect on myocardial stunning has not been elucidated. The purpose of this study was to investigate the antistunning effect of magnolol by evaluating the recovery of regional myocardial function after 10-minute coronary artery occlusion in anesthetized, open-chest rabbits. There was no significant hemodynamic change after intravenous infusion of magnolol. Systolic wall thickening fraction (WThF) measured with an epicardial Doppler sensor in animals pretreated with normal saline and vehicle solution remained significantly depressed (60 +/- 7% and 77 +/- 4% of baseline WThF, respectively) 3 hours after coronary artery reperfusion (CAR). Pretreatment with magnolol (10(-7) and 10(-6) g/kg, intravenous infusion) significantly enhanced the recovery of systolic wall thickening fraction (98 +/- 1 and 99 +/- 1% of baseline WThF, respectively) 60 minutes after CAR. This study demonstrated that intravenous pretreatment with magnolol protected myocardium against stunning.

Animals↗

PubMed2000

Surgical repair of postinfarction ventricular septal defect.

BACKGROUND: Rupture of the interventricular septum complicates 1% to 2% of all acute myocardial infarction patients and its natural course is ominous. The purpose of this study is to present our experience with surgical ventricular septal defect (VSD) repair and examine the possible risk factors and explanations for surgical mortality. METHODS: Fourteen patients underwent repair of postinfarction VSD from 1996 to 1998 at the Taipei Veterans General Hospital. Thirteen patients were in New York Heart Association (NYHA) Functional Class IV and one was in Functional Class III. Eleven patients were in cardiogenic shock with intra-aortic balloon pumps (IABPs) prior to surgery. The operative techniques for VSD repair range from extensive infarctectomy with reconstruction of the septum and the right and left ventricular free walls using single or double patches, to minimal or no infarctectomy with closure of the VSD by excluding the infarcted muscle from the left ventricular cavity and leaving the right ventricle intact. RESULTS: Overall surgical mortality occurred in four patients. All deaths occurred in patients with cardiogenic shock, two with anterior VSD and two with posterior VSD. Three late survivors had limited exercise tolerance with NYHA Functional Class II to III. Left ventricular function was moderately impaired in most patients with a mean nuclear scan ejection fraction of 0.32. However, all patients were elderly and adapted to their residual symptoms without significant life-style changes. CONCLUSIONS: The surgical mortality for treating patients with postinfarction VSD has decreased with improvements in surgical technique. Rapid diagnosis, appropriate preoperative management and delicate surgical repair improve the overall results and help to attain long-term survival.

Aged↗

PubMed2000

Minimally invasive mitral valve surgery via submammary hidden incision.

BACKGROUND: With the recent advancement in minimally invasive cardiac surgery based on the needs of decreasing costs, hospital stay, recovery time and improving cosmetic appearance, minimally invasive mitral valve surgery (MIMS) is being actively pursued. The objective of this study was to compare our submammary hidden incision method to two other more proven methods of MIMS with respect to length of operation, clinical outcome and cosmetic satisfaction. METHODS: From July, 1996 to June, 1998, a total of 14 patients underwent MIMS in our hospital. Three different approaches were used: the limited right-side thoracotomy approach, the parasternal incision approach and our submammary hidden incision approach, of which, this is the first report. All relevant clinical results are reported, including general characteristics of the operations, morbidity and mortality, length of hospitalization, pain relief and patient satisfaction. RESULTS: Five patients underwent MIMS via limited thoracotomy, four via parasternotomy and five with our submammary hidden incision method. There were six mitral valves repaired and eight replaced. Conversion to traditional sternotomy was not necessary in any of the three groups. The results from the three different approaches did not differ significantly across the different parameters measured. Nonetheless, the submammary hidden incision approach showed promise in the areas of length of stay for both intensive care patients (36.3 +/- 5.0 hours) and total hospitalization (10.7 +/- 0.6 days), pain relief and patient satisfaction. CONCLUSIONS: The submammary hidden incision method does not result in any significant disadvantage in clinical outcome. The method resulted in more satisfied patients due to less pain, shorter hospital stay, and most importantly, cosmetic appearance of the resulting surgical scar. We will make the submammary hidden incision approach the MIMS approach of choice at our institution and continue to monitor the long-term results.

Adult↗

PubMed2000

Effect of magnolol on coronary vascular resistance in rabbits: measurement with pulsed Doppler velocimetry.

BACKGROUND AND PURPOSE: Magnolol is an active component purified from Magnolia officinalis that has been reported to protect the myocardium against infarction and reperfusion injury. The purpose of this study was to investigate the effect of magnolol on the coronary circulation and to determine whether a change in coronary vascular resistance could be the mechanism underlying its myocardial protective effect. METHODS: Male New Zealand white rabbits were anesthetized. A 3-mm suction-type pulsed Doppler velocimetry probe was applied to the proximal part of the left anterior descending coronary artery after median sternotomy. The 39 rabbits received intravenous injection of either vehicle (n = 5), magnolol (10(-6) g/kg, n = 6; 10(-5) g/kg, n = 5; 10(-4) g/kg, n = 5), or nitroglycerin (10(-5) g/kg, n = 6; 10(-4) g/kg, n = 6; 10(-3) g/kg, n = 6). The effects of magnolol and nitroglycerin on coronary vascular resistance were compared. RESULTS: Magnolol did not change blood pressure or coronary blood flow velocity. However, at a dose of 10(-4) g/kg, it decreased coronary vascular resistance significantly more than vehicle (88 +/- 1% vs 95 +/- 1% of baseline coronary vascular resistance, p < 0.001). Nitroglycerin increased coronary blood flow velocity and decreased coronary vascular resistance in a dose-dependent manner (p < 0.01). CONCLUSIONS: Magnolol reduced coronary vascular resistance in anesthetized, open-chest rabbits only at a high concentration. Its effect was modest compared with that of nitroglycerin. Since magnolol protects the myocardium at relatively low doses, coronary vasodilatation is unlikely to be the underlying mechanism responsible for its myocardial protective effects.

Animals↗

PubMed2000

Surgical management of traumatic thoracic aortic rupture from falling.

A 40-year-male was admitted to our hospital after falling from a four-story height. Thoracic aortic rupture was suspected based on chest roentgenography and helical computed tomography. The patient was in the operating room within 6 hours after admission to the hospital. A median sternotomy with a left thoracotomy in the fifth intercostal space was done after left femoral arterial cannulation. Profound hypothermic circulation arrest with retrograde cerebral perfusion was applied. The site of aortic rupture was the descending aorta, just distal to the origin of the left subclavian artery. There were two areas of rupture within 2 cm of each other. The ruptured aorta was grafted with a 20-mm woven double-velour Hemashield graft. The total circulatory arrest time was 80 minutes and the cardiopulmonary bypass time was 290 minutes. The postoperative course was complicated by prolonged mechanical ventilation support due to pulmonary contusion. The patient was discharged 30 days after surgery without neurologic deficit.

Accidental Falls↗

PubMed2000

Plesiomonas shigelloides infection in Hong Kong: retrospective study of 167 laboratory-confirmed cases.

OBJECTIVE: To study the epidemiological, clinical, and microbiological features of Plesiomonas shigelloides infection in Hong Kong. DESIGN: Retrospective study. SETTING: Infectious Disease Unit of a district hospital, Hong Kong. PATIENTS: Patients with laboratory-confirmed cases of Plesiomonas shigelloides infection between 1 January 1995 and 31 December 1998. MAIN OUTCOME MEASURES: Epidemiological and clinical data, antibiotic sensitivity, and clinical outcome. RESULTS: There was an increasing trend in the number of isolates of Plesiomonas shigelloides obtained and the prevalence of the bacterium. A total of 197 isolates were obtained from 188 patients, and most isolates (172; 87.3%) were obtained during the summer. Clinical and epidemiological data were available for 167 patients (85 males, 82 females). Patient age ranged from 1 month to 95 years; the mean and median ages of the patients older than 15 years were 51.0 and 40.5 years, respectively (n=132). Only 35 (21.0%) of the 167 patients had a history of travel outside Hong Kong, whereas 21 (12.6%) had a history of consuming seafood or uncooked food; 39 (23.4%) had underlying medical conditions. Most patients (165; 98.8%) had symptoms of Plesiomonas shigelloides infection. Nine (5.4%) patients had had chronic diarrhoea for more than 2 weeks; watery and bloody diarrhoea was discharged by 122 (73.1%) and 42 (25.1%) of the patients, respectively. All 197 Plesiomonas shigelloides isolates were sensitive to ofloxacin, or levofloxacin and ceftriaxone. Resistance or partial resistance was recorded for ampicillin (72%), tetracycline (67%), co-trimoxazole (12%), and chloramphenicol (5%). The majority of patients (142/167; 85.0%) had self-limiting cases of infection, but 25 patients were given antibiotics for more severe symptoms at the time of presentation; there were two deaths. CONCLUSIONS: The occurrence of Plesiomonas shigelloides infection in Hong Kong is increasing, although most cases of are self-limiting.

Adolescent↗

PubMed1999

Sequential changes in heart rate variability after coronary artery bypass grafting.

Heart rate variability (HRV) decreased soon after coronary artery bypass grafting and returned to the preoperative level within 2 months; however, HRV did not exceed the preoperative level, even 6 months after coronary artery bypass grafting. Although myocardial ischemia can be improved by coronary artery bypass grafting, HRV did not benefit from coronary artery bypass grafting within 6 months.

Adult↗

PubMed1999

Cytomegalovirus colitis in individuals without apparent cause of immunodeficiency.

Cytomegalovirus infection is usually reported in immunocompromised patients. In this study, apparently immunocompetent patients with cytomegaloviral colitis were reviewed. Records with a diagnosis of cytomegaloviral colitis from January 1989 to June 1996 were retrieved for analysis. Ten patients were included (median age 70 yr). The major presenting symptoms were diarrhea and hematochezia. Ulceration was the main macroscopic finding. Rectal bleeding was mostly self-limiting. Three patients developed local complications (rectovaginal fistula in two; rectal stricture in one). In the two patients with rectovaginal fistula, lymphocytes subsets and proliferative response were entirely normal. In the other patient, low B lymphocyte count and low response to mitogen were demonstrated. However, the immunoglobulins were not suppressed and rectal biopsies revealed noncaseating granulomas, suggesting activated cell-mediated immunity. In conclusion, a high index of suspicion is crucial for early diagnosis of cytomegaloviral colitis in patients with bloody diarrhea, even though obvious evidence of immunodeficiency is lacking.

Aged↗

PubMed1999

Effects of dipyridamole, nitroglycerin, and nitroprusside on coronary vascular resistance in rabbits: measurement with pulsed Doppler velocimetry.

Dipyridamole, nitroglycerin, and nitroprusside are all effective vasodilators. However, few studies have compared their in vivo coronary vasodilatation effects. The purpose of this study was to compare the effects of these agents on coronary blood flow velocity and vascular resistance in anesthetized, open-chest rabbits. Male New Zealand white rabbits were anesthetized, and a 3-mm, suction-type, pulsed Doppler velocimeter probe was applied to the proximal part of the left anterior descending coronary artery after median sternotomy. The rabbits received infusion of various doses of dipyridamole (0.1 mg/kg, n = 5; 1 mg/kg, n = 5; 10 mg/kg, n = 9), nitroglycerin (0.01 mg/kg, n = 8; 0.1 mg/kg, n = 5; 1 mg/kg, n = 5; 10 mg/kg, n = 7), or nitroprusside (0.01 mg/kg, n = 5; 0.1 mg/kg, n = 5; 1 mg/kg, n = 5). The percent changes in coronary blood flow velocity and coronary vascular resistance were measured. All three vasodilators increased coronary blood flow velocity significantly and decreased coronary vascular resistance dose-dependently. The dose-response curves of dipyridamole, nitroglycerin, and nitroprusside were significantly different from one another (p < 0.01). Dipyridamole at a dose of 10 mg/kg produced the greatest increase in coronary blood flow velocity and the greatest reduction in coronary vascular resistance in anesthetized, open-chest rabbits.

Analysis of Variance↗

PubMed1999

Transmyocardial holmium-YAG laser channels in an animal model: a preliminary morphologic and histologic study.

BACKGROUND: Laser transmyocardial revascularization (TMR) appears to improve symptoms in patients with refractory angina. However, it remains a controversial treatment modality for relieving ischemia. We conducted our study in dogs and evaluated the changes in morphology and histology of the myocardium after laser TMR. METHODS: The hearts of 10 mongrel dogs (20-30 kg each) were treated with a holmiumyttrium aluminum garnet (YAG) laser in vivo. After opening the pericardium, the 1-mm fiberoptic device was used to create an average of 30 transmyocardial channels per heart at approximate intervals of 0.5 to 1 cm through normal left ventricular myocardium. All dogs tested survived the procedure. The dogs were sacrificed on the first and 60th postoperative days. RESULTS: In the day-1 postoperative group (n = 4), the transmyocardial channels were obliterated at both epicardial and endocardial ends. The channels were totally occupied by necrotic myocytes and did not appear patent under the microscope. In the day-60 postoperative group (n = 6), the epicardial and endocardial scars were identified at each original laser application site. On cross-section, the channels were invaded by fibrous tissue bands extending from the endocardium to the epicardium, without a prominent central passage. Trichrome stained specimens showed that the channels were replaced by collagen fibers, fat tissue and numerous well-developed capillaries or sinusoids in which plenty of red blood cells were found. CONCLUSIONS: We concluded that laser TMR offers no help for acute myocardial ischemia, but results in neovascularization inside the channels by the 60th postoperative day. Angiogenesis induced by laser TMR could possibly play a role in relieving chronic ischemia.

Animals↗

PubMed1999

Physicians' practice patterns of treating Helicobacter pylori-associated peptic ulceration in public hospitals in Hong Kong: questionnaire survey. Coordinator Group of the Quality Assurance Subcommittee (Medicine), Hospital Authority, Hong Kong.

To survey the practice patterns of physicians in public hospitals in Hong Kong when treating Helicobacter pylori-associated peptic ulceration, the records of all patients from 22 medical units who had new peptic ulcers that had been diagnosed endoscopically during August 1996 were examined systematically. Patient data were entered on a one-page questionnaire. Five hundred and twelve patients with peptic ulceration were studied; 173 (34%) of whom had presented with gastro-intestinal bleeding. The Helicobacter pylori status had been determined in 449 (88%) patients, 280 (62%) of whom had subsequently tested positive for Helicobacter pylori. The biopsy urease test or histological examination had been performed for more than 95% of patients. Of 260 patients who had tested positive for Helicobacter pylori, 244 (94%) had received eradication therapy to eliminate this organism; a total of 291 patients, however, were receiving eradication therapy. The most commonly used regimen was proton pump inhibitor triple therapy (151 [52%] of 291 patients). Confirmation of the eradication of Helicobacter pylori had been planned for 152 (52%) of the 291 patients, whereas ulcer-healing drugs--mainly H2-receptor antagonists--had been prescribed for 87 (30%) patients after eradication. Curing Helicobacter pylori infection is therefore widely accepted in the management of peptic ulcer disease among physicians working in Hong Kong public hospitals.

Journal Article↗

PubMed1998

Delayed mid-ileal perforation secondary to acute-on-chronic ischaemia after a diagnostic colonoscopy.

Perforation occurring at a remote site of the bowel after diagnostic colonoscopy is rare. A 61-year-old man presenting with bloody diarrhoea underwent colonoscopy. A dynamic ileus developed in less than 1 day, and mid-ileal perforation occurred 7 days after the procedure. It is suggested that high air pressure during colonoscopy further compromised the reduced blood flow in the mid-ileum, which had underlying chronic ischaemia, leading to perforation. Our patient constitutes the first reported case of small-bowel perforation after colonoscopy due to pre-existent ileal ischaemia.

Acute Disease↗

PubMed1998

Acute encephalitis complicating rubella.

During an epidemic of rubella in Hong Kong between October 1996 and June 1997, four male patients presented with rubella complicated by encephalitis, the symptoms of which started 1 to 5 days after the appearance of the rash characteristic of rubella. Two patients recovered completely within 1 week and one complained of a slight impairment of short-term memory. Severe cerebral oedema, and herniation across the brainstem and cerebellum developed in the fourth patient, who died 15 days later. The presence of serum immunoglobulin M antibody against rubella virus was demonstrated in all four patients; one patient also had immunoglobulin M antibody against rubella virus in his cerebrospinal fluid. No virus could be isolated during post-mortem examination of the fourth patient.

Journal Article↗