Albert C.W. Ting

Irradiation-induced extracranial carotid stenosis in patients with head and neck malignancies

BACKGROUND Carotid stenosis is a recognized complication of external irradiation to the head and neck for malignancy. This study aim to investigate the pattern and prevalence of radiation induced carotid disease, and to identify risk factors associated with significant stenosis. METHODS In a comparative cross-sectional study, carotid arteries color flow duplex scan was performed on 240 patients who had received external irradiation to the head and neck area, with a mean interval of 72 months from radiotherapy. They consisted of 181 men and 59 women, with a mean age of 59 years. Fifteen patients had a history of cerebrovascular symptoms. RESULTS Internal carotid artery (ICA) stenosis of 70% or greater was detected in 29 arteries in 24 patients. Common carotid artery (CCA) disease of > or =70% was present in 13 arteries in 12 patients. Overall 28 patients had significant ICA/ CCA disease (11.7%). Patients with nasopharyngeal and laryngeal carcinoma had more cerebrovascular symptoms, and more frequent CCA stenosis. Significant ICA/CCA stenosis was associated with age, smoking, coronary heart disease, stroke, no head and neck surgery, time interval from radiotherapy, and the site of primary tumor. On logistic regression analysis age (>60 years), cerebrovascular symptoms, interval from irradiation (>5 years), and nasopharynx and larynx cancer were found to be independent significant (P<0.05) predictors of 70% or greater ICA/CCA stenosis. CONCLUSIONS Patients who had received radiotherapy to the head and neck have a high risk of developing significant carotid stenosis. Routine duplex ultrasound screening in these patients is indicated.

Aortic Aneurysm Morphology in Asians: Features Affecting Stent-Graft Application and Design:

Purpose: To determine the morphological features of abdominal aortic aneurysms (AAA) in an Asian cohort in order to identify unique features relevant to stent-graft planning and application. Methods: Spiral computed tomography (CT) and angiographic assessment of AAA morphology was performed on 65 ethnic Chinese (58 men; mean age 74 years, range 50–87) who underwent endovascular AAA repair. Morphological parameters were compared with published data from American and European patients. The eligibility and potential concerns referable to 4 current stent-graft designs were addressed. Results: Both common iliac arteries (CIA) measured significantly shorter in Asians, particularly on the right side. The mean RCIA and LCIA lengths were 29.9 mm and 34.2 mm, respectively (25.7 and 34.1 mm for CIAs <20 mm in diameter), compared to >50-mm in Caucasians (p<0.001). The distance between the lowest renal artery and the CIA bifurcation averaged 20 mm shorter in Asians: 148 mm on the right side and 153 mm for the left. The CIAs were also wider, averaging 20.2 mm for the right and 17.9 mm for the left. Other linear measurements did not show a population difference. The AAAs in this series were slightly larger (p<0.001), with a shorter neck (mean 23 mm, p<0.001). No correlation was found between the morphological parameters and body build. Internal iliac artery coverage with or without embolization was necessary in 51% of endovascular repairs due to short or aneurysmal CIAs. Conclusions: These differences in AAA morphology pose unique challenges for endovascular repair in Asians. Preoperative angiography is more often necessary. The need for an accurate landing in a short CIA and insufficient length for maneuvering placed constraints on 2-piece graft designs with long main body lengths. A 3-piece endograft with wider aortic and iliac diameters is currently the most attractive option.

Endovascular stenting of superficial femoral artery stenosis and occlusions: results and risk factor analysis.

PURPOSE To determine the early and midterm results of femoro-popliteal angioplasty with adjunctive stenting and to identify factors affecting early and continuing success. METHODS Sixty-nine consecutive balloon angioplasty procedures on the superficial femoral artery (SFA) were performed in 60 limbs and 55 patients in the operating theater. Fifty-two percent of lesions were occlusions, and 87% involved the distal half or the whole segment of the SFA. Immediate endovascular stenting was used in all procedures, involving the placement of 105 stents, with a mean stented length of 13.8 cm. Twenty-nine procedures (43%) were performed for critical ischemia. Three-monthly duplex ultrasound was used for follow up assessment, with stenosis of > 50% defined as the endpoint for failure. The patient demographic and biochemical data, and procedural details were correlated with success criteria according to Society of Vascular Surgery standards. RESULTS Initial technical success by intent to treat was 92%, with four procedure-related complications and no deaths. Initial success by anatomic, hemodynamic and clinical criteria were 98.3, 96.7 and 93.3% respectively (92.2, 90.6 and 87.5% by intent to treat). Cumulative primary patency at 6, 12, and 24 months was 73.1, 62.6 and 53.8%, and secondary patency 84.9, 72.1 and 72.1% correspondingly. Significant factors relating to inferior patency were occlusions, stented segment length > 10 cm, procedure in claudicants, and the use of the Memotherm stent. CONCLUSIONS Angioplasty and stenting of the superficial femoral artery has acceptable primary and secondary patency rates even in the presence of long stenosis and occlusions. A duplex surveillance program is recommended for early detection and timely treatment of restenosis.

Femoral pseudoaneurysms in drug addicts.

Abstract. Femoral pseudoaneurysm is a serious complication in drug addicts who habitually inject via the groin. A total of 33 drug addicts presenting with 34 infected femoral pseudoaneurysms were treated in the Department of Surgery, the University of Hong Kong, Queen Mary Hospital from July 1993 to June 1996. There were 27 men and 6 women, with ages ranging from 23 to 76 years (mean 39.6 years). Positive intraoperative tissue cultures were seen in 29 (85%), with 17 being pure growth of methicillin-sensitiveStaphylococcus aureus (MSSA). Twenty-four pseudoaneurysms involved the femoral bifurcation and were treated by triple ligation of the common femoral, superficial femoral, and profunda femoris arteries. Seven other limbs underwent ligation of the common femoral artery alone, and three had superficial femoral artery ligation. Nineteen limbs had the external iliac artery ligated in addition to the femoral ligation for better proximal control. The mean postoperative ankle–brachial index (ABI) was 0.43 and 0.52 in those with triple ligation and those with single-vessel ligation, respectively. There was no hospital mortality, and all patients were discharged with a viable limb. The duration of follow-up ranged from 2 to 36 months (mean 15.5 months). Four patients were asymptomatic, but the rest suffered some degree of intermittent claudication. No delayed limb loss was identified. We conclude that systemic antibiotics active against MSSA are the antibiotics of choice in drug addicts with infected femoral pseudoaneurysms. Ligation and excision of the pseudoaneurysm without revascularization is safe, with acceptable morbidity and a low limb loss rate.

Supra-aortic hybrid endovascular procedures for complex thoracic aortic disease : Single center early to midterm results

BACKGROUND Hybrid technique with open surgical supra-aortic extra-anatomical bypasses (to provide a suitable proximal landing zone) and simultaneous or staged thoracic endovascular stent grafting is less invasive than open surgery in the treatment of complex aortic arch pathology. The aim of this study is to report our hybrid experience. METHODS Retrospective review of prospectively collected computerized database. All patients had regular clinical and radiological computed tomography follow-up. RESULTS Sixteen patients (13 males and 3 females) with mean age of 64.8 (range 51-79) were treated with hybrid techniques between May 2005 and September 2007. There were nine elective, two urgent (within 2 weeks of presentation), and five emergency cases. Thirteen patients had arch or proximal descending thoracic aortic aneurysms, and six patients had aortic dissections. All extra-anatomical bypasses were performed simultaneously with stent grafts, with mean operating time of 331.2 (range 195-540) minutes. Eight patients had right to left carotid-carotid cross-over graft, five had bifurcating grafts from ascending aorta to innominate and left carotid artery, two had left carotid to left subclavian artery, and one had left carotid to aberrant right subclavian bypass graft. All patients had Cook Zenith thoracic stent grafts. Deployment success was 100%, with no endoleak on completion angiogram. There was no mortality. Three patients had postoperative nondebilitating stroke and no paraplegia. The mean follow-up was 14 (range 1-27) months. One reintervention was required, and two patients had type II endoleak treated conservatively. CONCLUSION Supra-aortic hybrid procedures in treating aortic arch pathology are safe and effective, and early- to midterm results are encouraging.

Posterior or laparoscopic approach for adrenalectomy

Abstract Background: The pathologies and size of adrenal lesions removed through the open posterior and laparoscopic routes share remarkable similarities. This study aims at comparing the relative merits of these two approaches. Methods: Patients with adrenal tumors operated on by posterior approach (n = 56) and transabdominal laparoscopic approach (n = 12) between January 1981 and May 1997 were retrospectively reviewed. Results: The two groups were comparable in terms of age, and the position, size, and weight of the tumor. The operative time of posterior adrenalectomy was significantly shorter than that of laparoscopic adrenalectomy (median 120 minutes versus 160 minutes), whereas laparoscopic adrenalectomy was associated with less parenteral analgesic requirement (median 0 mg versus 225 mg), a shorter hospital stay (median 3 days versus 5 days), and a shorter duration off work (median 11 days versus 26 days). The estimated blood loss was also significantly reduced in the laparoscopic group (median 50 mL versus 150 mL). Conclusions: Laparoscopic adrenalectomy is replacing posterior adrenalectomy to become the procedure of choice for the majority of patients undergoing adrenalectomy.BACKGROUND The pathologies and size of adrenal lesions removed through the open posterior and laparoscopic routes share remarkable similarities. This study aims at comparing the relative merits of these two approaches. METHODS Patients with adrenal tumors operated on by posterior approach (n = 56) and transabdominal laparoscopic approach (n = 12) between January 1981 and May 1997 were retrospectively reviewed. RESULTS The two groups were comparable in terms of age, and the position, size, and weight of the tumor. The operative time of posterior adrenalectomy was significantly shorter than that of laparoscopic adrenalectomy (median 120 minutes versus 160 minutes), whereas laparoscopic adrenalectomy was associated with less parenteral analgesic requirement (median 0 mg versus 225 mg), a shorter hospital stay (median 3 days versus 5 days), and a shorter duration off work (median 11 days versus 26 days). The estimated blood loss was also significantly reduced in the laparoscopic group (median 50 mL versus 150 mL). CONCLUSIONS Laparoscopic adrenalectomy is replacing posterior adrenalectomy to become the procedure of choice for the majority of patients undergoing adrenalectomy.

Epidemiology of atherosclerotic peripheral arterial occlusive disease in Hong Kong.

p < 0.001), age (p < 0.001), nonsmoking (p < 0.001), diabetes (p < 0.005), a low hemoglobin/hematocrit (p < 0.001), a high white blood cell count (p < 0.001), and high levels of fibrinogen (p < 0.01) and cholesterol (p < 0.05). An increasing incidence of PAD was noted in Hong Kong. Most of the patients present late with advanced ischemia. It is possible that this disease pattern represents only a fraction of the true incidence of PAD in the territory.

Carotid Stenting for Radiation-Induced Extracranial Carotid Artery Occlusive Disease: Efficacy and Midterm Outcomes

PURPOSE To investigate the immediate and midterm results of carotid stenting for severe radiation-induced extracranial carotid artery disease. METHODS Between April 1998 and May 2002, 16 patients (15 men; mean age 64 +/- 8 years, range 48-72) presented with 18 severe radiation-induced carotid stenoses in the internal carotid artery (n=3), common carotid artery (n=7), and both vessels (n=8). Thirteen (76%) patients were symptomatic; the mean degree of carotid stenosis was 85% +/- 10% (range 70%-95%). An independent neurological specialist assessed perioperative neurological complications before and after treatment. The patients were followed prospectively for at least 12 months by clinical examination and serial duplex ultrasound scanning. Restenosis was defined as a diameter reduction >50%. RESULTS Of 18 stent procedures attempted (2 staged), 1 was abandoned owing to failure to pass the guidewire across a tight lesion (94% technical success by intent to treat). In the 17 successfully completed procedures, 17 Wallstents and 4 SMART stents were deployed with satisfactory anatomical results. One postoperative stroke occurred as a result of thromboembolism to the ipsilateral middle cerebral artery and led to hospital death (5.9% combined stroke and death rate). One transient ischemic attack occurred (11.6% neurological event rate). With a median 30-month follow-up (range 5-55), 3 (17.6%) recurrent stenoses (>50%) were detected on duplex scan; 1 repeat angioplasty was performed. No new neurological event has been detected. CONCLUSIONS Carotid stenting may be performed in patients with irradiation-induced carotid stenosis with acceptable risks and midterm durability.

A computational fluid dynamic study of stent graft remodeling after endovascular repair of thoracic aortic dissections

OBJECTIVES Significant stent graft remodeling commonly occurs after endovascular repair of thoracic aortic dissections because of continuing expansion of the true lumen. A suboptimal proximal landing zone, minimal oversizing, and lack of a healthy distal attachment site are unique factors affecting long-term stent graft stability. We used computational fluid dynamic techniques to analyze the biomechanical factors associated with stent graft remodeling in these patients. PATIENTS AND METHODS A series of computational fluid dynamic models were constructed to investigate the biomechanical factors affecting the drag force on a thoracic stent graft. The resultant drag force as a net change of fluid momentum was calculated on the basis of varying three-dimensional geometry and deployment positions. A series of 12 patients with type B aortic dissections treated by thoracic stent graft and followed up for more than 12 months were then studied. Computed tomography transaxial images of each patient shortly after stent graft deployment and on subsequent follow-up were used to generate three-dimensional geometric models that were then fitted with a surface mesh. Computational fluid dynamic simulations were then performed on each stent graft model according to its geometric parameters to determine the actual change in drag force experienced by the stent graft as it remodels over time. RESULTS The drag force on the stent graft model increases linearly with its internal diameter and becomes highest when the deployment position is closer to the proximal arch. Aortic curvature is not a significant factor. Serial computed tomography scans of patients showed an increase in mean inlet area from 1030 mm(2) to 1140 mm(2), and mean outlet area from 586 mm(2) to 884 mm(2) (increase of 11% and 58%, respectively; P = .05, .01). These increases are associated with a change in resultant drag force on the stent graft from 21.0 N to 24.8 N (mean increase, 19.5%; range, 0%-63.2%; P = .002). There is a positive relationship between increase in drag force and increase in stent-graft area. CONCLUSION The drag force on thoracic stent grafts is high. A significant change in stent-graft diameter occurs after endovascular repair for type B dissections, which is associated with an increase in hemodynamic drag force. These stent grafts may be subjected to a higher risk of distal migration, and continuing surveillance is mandatory.

Epidemiology and outcome of aortic aneurysms in Hong Kong.

Abstract The objective of this study was to determine epidemiology and mortality statistics for abdominal aortic aneurysms (AAAs) in Hong Kong. Data from three sources were obtained and analyzed: (1) Hong Kong Hospital Authority discharge statistics for 1999 and 2000; (2) a survey on aortic aneurysms in public hospitals conducted by the Working Group of Vascular Surgery; and (3) the Department of Surgery, University of Hong Kong Medical Center aortic aneurysm database. The disease pattern, distribution, and operative mortality were determined. The annual incidence of AAA in Hong Kong is 13.7 per 100,000 population and 105 per 100,000 for those aged 65 and above. About 10% of the AAAs that presented were ruptured. The mean age of the AAA patients was 74 years, with 84% of them over age 65. The operative repair rate for AAAs was low, being only 8% for intact aneurysms and 54% for ruptured ones. Overall, 45% of all aneurysm repairs were performed for a ruptured AAA. There is diverse practice between major vascular centers and smaller regional hospitals. The territory-wide operative mortality rates for intact and ruptured aneurysms were 10% (range 4–24%) and 70% (range 38––100%), respectively. There was no gender bias in the rupture and operative rates. The overall mortality was 17% for intact AAAs and 78% for ruptured AAAs. The average length of hospital stay was 19 days for elective AAA surgery and 13 days for ruptured AAAs. The number of operations in high-volume centers is increasing with a concomitant decrease in operative mortality. There are no definitive data to indicate that the incidence of AAAs is rising, but a trend toward an increasing number of operations in referral centers is noted. The low repair rates for intact AAAs and the high proportion of repairs for ruptured aneurysms suggest that AAAs are undertreated in Hong Kong.