Biomedical subjects

Stephen W K Cheng

Publications and source records attributed to Stephen W K Cheng.

24 records · Page 2Linked to original sources

PubMed2003

Endovascular repair for abdominal aortic aneurysms: initial experience of an endograft programme.

OBJECTIVE: To evaluate early clinical results of elective endovascular repair of abdominal aortic aneurysms during the initial phase of an aortic endograft programme and to compare them with conventional open surgery. METHODS: Between July 1999 and September 2001, all patients with infrarenal abdominal aortic aneurysms undergoing elective repair were studied. The results of endovascular repair were compared with those of conventional repair. RESULTS: Twenty-seven endovascular repairs (24 men and three women; mean age, 74 yr) and 25 conventional repairs (19 men and six women; mean age, 73 yr) for infrarenal abdominal aortic aneurysms were evaluated. The aneurysm diameters in the two groups were similar (mean, 6.1 cm in the endovascular repair group and 6.6 cm in the conventional repair group). The comorbidities of the two groups were also comparable. The duration of operation was longer in the endograft group (249 +/- 86 min vs. 206 +/- 56 min), while the blood loss was significantly less (600 +/- 486 mL vs. 1074 +/- 1220 mL). The length of stay in the Intensive Care Unit (ICU) and the overall duration of hospitalization was also significantly less in the endograft group (1 +/- 1 d vs. 3 +/- 2 d in ICU; 9 +/- 5 d vs. 13 +/- 6 d of hospitalization). There was one hospital death in each group (4%), and the complications were similar between the two groups. During a mean follow-up period of 11.6 +/- 7.5 months, there was no rupture or open conversion in the endograft group. CONCLUSIONS: In the initial phase of the aortic endograft programme, the mortality and morbidity were acceptable and comparable to that of open surgery.

Aged↗

PubMed2003

Endoluminal stent grafts for aortic diseases: experience at a major teaching hospital in Hong Kong.

BACKGROUND: The purpose of the present paper was to review the initial experience of an endovascular aortic stent graft program at a major teaching hospital in Hong Kong. METHODS: Demographics, operative details, complications and follow-up data of all the patients receiving endovascular repair for aortic disease were recorded prospectively. RESULTS: Between July 1999 and December 2001, endovascular repairs were attempted in 39 patients with aortic disease. The procedural success rate was 97.4%. Thirty-three procedures were for abdominal aorto-iliac aneurysms. Graft configuration was bifurcated in 28 patients (85%) while an aorto-uni-iliac device with a femoro-femoral bypass was carried out in the remaining five patients. Thoracic procedures were carried out for one thoracic aortic aneurysm, two traumatic thoracic aortic injuries, one thoracic aortic dissection, and one thoracic aortic pseudoaneurysm with aorto-oesophageal fistula. There was one hospital mortality (2.6%) from a type A thoracic aortic dissection with cardiac tamponade. Postoperative complications were seen in seven patients (18%). With a mean follow-up of 11.6 +/- 8.1 months, there was no open conversion or rupture. The endoleak rate was 27% at discharge, 15% at 6 months and 5% at 12 months postoperatively. For aneurysm endografts, the aneurysm sac decreased in size in 21 patients (62%), and remained static in 13 patients (38%). CONCLUSIONS: The endoluminal stent graft appears to be a promising device that can be used safely in selected patients with aortic disease. Continued follow-up is required to monitor the presence of endoleak and the size of the aneurysm sac.

Aged↗

PubMed2002

Ultrasonic analysis of plaque characteristics and intimal-medial thickness in radiation-induced atherosclerotic carotid arteries.

OBJECTIVES: to investigate the effect of external irradiation on the morphology of atherosclerotic plaques and the intimal-medial thickness of the carotid artery. METHODS: a group of 46 patients (16 symptomatic) who had received external irradiation to the head and neck area more than five years previously and developed carotid stenosis exceeding 50%, were evaluated by duplex ultrasound. The carotid artery lumen, intimal-medial complex, and the plaque echogenicity was determined using computer digital image processing methods. Forty-six age and sex matched patients with similar degrees of non-radiation associated carotid stenosis were used as controls. RESULTS: irradiated stenotic carotid arteries had a greater intimal-medial thickness (0.96 mm vs 0.80 mm, p=0.008) and a narrower lumen (5.5 mm vs 6.6 mm, p<0.001) than the controls. The carotid plaque characteristics (gray-scale median (GSM) and heterogeneity) of the irradiated and control groups did not differ significantly. Symptomatic patients who had received external radiotherapy to the head and neck have a more echolucent plaque (mean GSM of 98) than their asymptomatic counterparts (mean GSM 114, p=0.03). Intimal-medial thickness and carotid lumen was not related to the occurrence of symptoms. CONCLUSIONS: external irradiation to the head and neck area leads to significantly increased thickness of the carotid wall and a corresponding narrowing of the lumen. There seems to be no difference in the plaque characteristics between irradiation-induced and spontaneous carotid atherosclerosis.

Adult↗

PubMed2002

Early and late outcomes in Hong Kong Chinese patients undergoing carotid endarterectomy.

OBJECTIVE: To determine the benefit of carotid endarterectomy (CEA) for stroke prevention by reviewing the early and late outcomes of Hong Kong Chinese patients undergoing CEA who have a high reported incidence of intracranial atherosclerotic disease (IAD). METHODS: Fifty-nine Chinese patients underwent 62 CEA. There were 48 males and 11 females, with a mean age of 70 +/- 7 years (range: 52 - 86 years). Twenty-one CEA (34%) were performed for asymptomatic disease. Duplex scan was the primary tool of evaluation prior to surgery. Preoperative angiography was done in 36 instances (58%). All CEA were performed under general anaesthesia with routine intraoperative shunting. The arteriotomy was closed primarily in all patients except three. Patients were followed up regularly with six-monthly Duplex scan surveillance. RESULTS: There were 2 perioperative neurological events consisting of one transient ischemic attack and one minor stroke. There was no operative mortality or major morbidity such as bleeding or cranial nerve injury. Mean hospital stay was 6.5 +/- 4 days (range: 3 - 26 days). The patients were followed up for a mean interval of 24 +/- 17 months (range: 1 - 57 months). Seven patients died during follow-up and subsequent neurological events occurred in 5 patients, including 2 fatal strokes. The 3-year survival, freedom from stroke and stroke free survival were 86%, 87% and 83%, respectively. One recurrent stenosis of 80% was detected on follow-up Duplex scan. CONCLUSIONS: Despite a high incidence of IAD, CEA in Hong Kong Chinese patients is associated with acceptable perioperative morbidity and mortality with satisfactory long-term efficacy in stroke prevention.

Aged↗

PubMedDate not supplied

Perioperative deep vein thrombosis in Chinese patients undergoing craniotomy.

BACKGROUND: We attempted to determine the incidence of perioperative deep vein thrombosis (DVT) in Chinese patients undergoing elective craniotomy for brain tumors and to assess the efficacy of clinical and serial calf circumference assessment in detecting DVT. METHODS: Between June 1999 and February 2001, 100 consecutive patients who underwent elective craniotomy for brain tumors at the Department of Neurosurgery, University of Hong Kong Medical Centre were examined for perioperative DVT. The demographic data, Glasgow coma score (GCS), mobility status, and the operative details were recorded. Graduated compression stockings and intermittent pneumatic compression were applied perioperatively as prophylaxis against DVT. Serial duplex scans were performed before and after operation. Clinical examination was also performed daily to look for signs of DVT. The calf circumference was measured at fixed levels for both limbs before each duplex scan surveillance. RESULTS: The study group consisted of 44 males and 56 females, with a mean age of 54 +/- 15 years (range, 20-81 years). There was no preoperative DVT. Postoperative DVT was detected on duplex scan in four patients (4%), two of whom had bilateral involvement. The thrombosis was confined to the calf veins in two limbs. The demographic data, neurologic status and operative details of patients with and without DVT were similar. Patients with DVT had no clinically recognizable signs. The change in calf circumference measurement was also not predictive of DVT. CONCLUSIONS: The incidence of perioperative DVT in Chinese patients undergoing elective craniotomy for brain tumors appears to be low with the present mechanical prophylactic measures. Given the low incidence of proximal DVT as detected by duplex scan, the use of heparin prophylaxis may not be justified because of the increased risk of intracranial bleeding. Clinical assessment with calf circumference measurement is unreliable in the diagnosis of DVT.

Adult↗

PubMedDate not supplied

Expression of integrin alpha5beta1 and the relationship to collagen and elastin content in human suprarenal and infrarenal aortas.

The infrarenal aorta is especially prone to the development of aneurysm, suggesting an intrinsic structural and molecular difference in different parts of the aorta. Previous study from this laboratory has implicated a potential role of integrin alpha5beta1 in maintaining aortic integrity. The aim of this study was to investigate the expression of integrin alpha5beta1 and the relationship to collagen and elastin content between 2 different aortic segments. In this study, the variation of smooth muscle cells and the localization of integrin alpha5beta1 in the suprarenal and infrarenal aorta tissues removed from organ donors were studied immunohistochemically. The biochemical analysis for matrix proteins and integrin alpha5beta1 protein was done by Western Blot on the corresponding tissues. All interested protein content was normalized to the smooth muscle alpha-actin protein. No significant difference of smooth muscle cells density between the 2 segments of aortas was observed. Integrin alpha5beta1 was localized in the outer layer of all aortic media. The authors found that the ratio of collagen/elastin in infrarenal aortas was significantly increased 2-fold because elastin content in infrarenal aortas decreased 49% as compared with suprarenal aortas. Integrin alpha5beta1 content relative to its specific ligand-collagen-did not differ between these 2 different aortic segments. These results suggest that the infrarenal aorta differed biochemically from the suprarenal aorta. A decrease in infrarenal elastin without a corresponding decrease in collagen and integrin alpha5beta1 may affect the compliance and integrity of the distal aorta. These intrinsic anatomic differences may be important in the susceptibility of the infrarenal aortas to aneurysm formation.

Aorta, Abdominal↗