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Biomedical subjects

P H Lin

Publications and source records attributed to P H Lin.

At least 19 recordsLinked to original sources
PubMed2006

Carotid artery stenting--current status and future directions.

Carotid endarterectomy has been the standard of therapy for carotid occlusive disease in stroke prevention. More recently, carotid angioplasty and stenting became an important alternative in the treatment of carotid occlusive disease. The widespread use of cerebral protection devices has substantially decreased the morbidity of the procedure. As the experience with carotid stenting increases, so does the enthusiasm for the potential of this minimally invasive carotid intervention to become the main treatment option for the high risk patients, as well as for the average asymptomatic patient. Although current available data indicate that the results regarding success and complication rates are similar between carotid stenting and endarterectomy, several prospective clinical trials are currently in progress to evaluate the efficacy of carotid artery stenting in different patient populations and definitively establish its role in the treatment of carotid disease. This paper reviews the current status of carotid stenting, including results from clinical trials, technical aspects and controversial issues and strategies to provide cerebral protection from embolization.

Angioplasty, Balloon↗
PubMed2005

Fabrication and characteristics of bioactive sodium titanate/titania graded film on NiTi shape memory alloy.

A bioactive sodium titanate/titania graded film was formed in situ on NiTi shape memory alloy (SMA) by oxidizing in H(2)O(2) solution and subsequent NaOH treatment and characterized by scanning electron microscopy, Raman spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). The bioactivity of the film was investigated using a simulated body fluid (SBF) soaking test. A titania (TiO(2)) layer was first found on NiTi substrate after oxidized in H(2)O(2) solution, and then a porous sodium titanate (Na(2)TiO(3))/titania film with many Ti--OH groups and a trace of Ni(2)O(3) was formed by the reaction of partial TiO(2) phase with NaOH solution. After immersion in SBF for 12 h, apatite was observed to nucleate and grow on the film. With longer soaking time, more apatite appeared on its surface but our control experiments didn't reveal any apatite formation on the chemically polished NiTi SMA, which indicates the bioactivity of NiTi implants could be improved by the formation of the bioactive film. Moreover, XPS depth profiles of O, Ni, Ti, and Na show the bioactive film possesses a smooth graded interface structure to NiTi substrate, which is in favor of sufficient mechanical stability of apatite layer by subsequent deposition in SBF.

Biocompatible Materials↗
PubMed2003

Epidural analgesia in patients with chronic obstructive pulmonary disease undergoing transperitoneal abdominal aortic aneurysmorraphy--a multi-institutional analysis.

INTRODUCTION: Patients with chronic obstructive pulmonary disease (COPD) are more likely to develop pulmonary morbidity following major abdominal surgery. The purpose of this study was to examine the utility of epidural analgesia in patients with COPD who underwent elective transperitoneal abdominal aortic aneurysm (AAA) repair. METHODS: During a 7-year period, all patients diagnosed with COPD undergoing elective AAA repair (n=425) from three hospitals were reviewed. Inclusion criteria were an FEV(1)/FVC ratio <75% and/or a PaCO(2)>45 mmHg. Clinical outcomes were compared between those who received epidural analgesia (epidural group) and those who did not (control group). Primary endpoints measured were duration of intubation, ICU stay, hospital days, and pulmonary complications. RESULTS: Strict inclusion criteria were met by 131 patients, which included 86 patients in the epidural group and 45 patients in the control group. When comparing the epidural vs. control group, the mean AAA size was 6.3+/-0.9 cm vs. 6.0+/-1.5 cm (NS), FEV(1) was 57.2+/-24.7% vs. 49.0+/-10.3% (NS), and the mean FEV(1)/FVC ratio was 52.0+/-11.4% vs. 50.6+/-6.7% (NS), respectively. The epidural group had a significantly lower incidence of post-operative ventilator dependency and ICU stay (p<0.05), as well as a decreased trend in pulmonary complications when compared to the control group. The overall hospital stay remained similar between the two groups. The relative risk of developing a pulmonary complication in the absence of epidural analgesia was 2.3. CONCLUSIONS: Perioperative epidural analgesia is beneficial in patients with COPD undergoing AAA repair by reducing both the post-operative ventilator duration and ICU stay. Epidural analgesia should be considered in all COPD patients undergoing elective transperitoneal AAA repair.

Aged↗
PubMed2003

Endovascular management of abdominal aortic aneurysms.

An estimated 1.5 million people in the United States have abdominal aortic aneurysms (AAAs) with more than 200000 American diagnosed each year. The natural history of AAAs is to expand and rupture, accounting for an estimated 15000 deaths per year. Thus, the major impetus for AAA repair is for prophylaxis against aneurysm-related death. The standard open surgical repair of AAAs is a well-established and durable procedure. However, as with all other major abdominal surgical operations, associated significant morbidity and mortality exist, along with prolonged recovery and various late complications. Furthermore, both mortality and morbidity increase significantly with advanced patient age and associated co-morbid disease states. Endovascular AAA repair using covered stent-grafts offers a significantly less invasive alternative to conventional open-surgical repair. A considerable reduction in hospital stay has been demonstrated, with early return to preoperative levels of activity. Patients previously considered unsuitable for open repair can often receive treatment for aneurysms with endovascular techniques. Current estimates are that more than 1/2 all infrarenal AAAs will be repaired using endovascular approach in the future. Despite the minimally-invasiveness of this new treatment, there are unanswered questions as to the durability and efficacy of devices, which results in concerns about their ability to successfully protect the patient from subsequent rupture. Three devices are commercially available and have been extensively used for implantation in the United States with a 4th device recently receiving approval from the Food and Drug Administration (FDA). In this review article, endovascular management of AAAs with these devices is described, as are the design and deployment techniques of the currently available endografts.

Aortic Aneurysm, Abdominal↗
PubMed2001

Characterization of metabolic activation of pentachlorophenol to quinones and semiquinones in rodent liver.

Pentachlorophenol (PCP), a widely used biocide, induces liver tumors in mice but not in rats. Metabolic activation of PCP to chlorinated quinones and semiquinones in liver cytosol from Sprague-Dawley rats and B6C3F1 mice was investigated in vitro (1) with microsomes in the presence of either beta-nicotinamide adenine dinucleotide phosphate (NADPH) or cumene hydroperoxide (CHP), (2) with CHP in the absence of microsomes, and (3) with horseradish peroxidase (HRP) and H2O2. Mono-S- and multi-S-substituted adducts of tetrachloro-1,4-benzoquinone (Cl4-1,4-BQ) and Cl4-1,2-BQ and their corresponding semiquinones [i.e. tetrachloro-1,4-benzosemiquinone (Cl4-1,4-SQ) and tetrachloro-1,2-benzosemiquinone (Cl4-1,2-SQ)] were measured by gas chromatography-mass spectrometry (GC-MS). Qualitatively, the metabolites of PCP were the same in both rats and mice for all activation systems. Induction of PCP metabolism by either 3MC or PB-treated microsomes was observed in NADPH- but not in CHP-supported systems. In rats, the amount of induction was comparable with either 3MC or PB. 3MC was a stronger inducer than PB in mice and also induced a greater amount of metabolism than in rats. This suggests that induction of specific P450 isozymes may play a role in the toxicity of PCP to mice. Both HRP/H2O2 and CHP led to production of the full spectrum of chlorinated quinones and semiquinones, confirming the direct oxidation of PCP. CHP (with or without microsomes) converted PCP into much greater quantities of quinones and semiquinones than did microsomal P450/NADPH or HRP/H2O2 in both species. This implies that, under conditions of oxidative stress, endogenous lipid hydroperoxides may increase PCP metabolism sufficiently to enhance the toxicity and carcinogenicity of PCP.

Animals↗
PubMed2001

Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. DASH-Sodium Collaborative Research Group.

BACKGROUND: The effect of dietary composition on blood pressure is a subject of public health importance. We studied the effect of different levels of dietary sodium, in conjunction with the Dietary Approaches to Stop Hypertension (DASH) diet, which is rich in vegetables, fruits, and low-fat dairy products, in persons with and in those without hypertension. METHODS: A total of 412 participants were randomly assigned to eat either a control diet typical of intake in the United States or the DASH diet. Within the assigned diet, participants ate foods with high, intermediate, and low levels of sodium for 30 consecutive days each, in random order. RESULTS: Reducing the sodium intake from the high to the intermediate level reduced the systolic blood pressure by 2.1 mm Hg (P<0.001) during the control diet and by 1.3 mm Hg (P=0.03) during the DASH diet. Reducing the sodium intake from the intermediate to the low level caused additional reductions of 4.6 mm Hg during the control diet (P<0.001) and 1.7 mm Hg during the DASH diet (P<0.01). The effects of sodium were observed in participants with and in those without hypertension, blacks and those of other races, and women and men. The DASH diet was associated with a significantly lower systolic blood pressure at each sodium level; and the difference was greater with high sodium levels than with low ones. As compared with the control diet with a high sodium level, the DASH diet with a low sodium level led to a mean systolic blood pressure that was 7.1 mm Hg lower in participants without hypertension, and 11.5 mm Hg lower in participants with hypertension. CONCLUSIONS: The reduction of sodium intake to levels below the current recommendation of 100 mmol per day and the DASH diet both lower blood pressure substantially, with greater effects in combination than singly. Long-term health benefits will depend on the ability of people to make long-lasting dietary changes and the increased availability of lower-sodium foods.

Blood Pressure↗
PubMed2001

Endovascular revascularization of renal artery stenosis in the solitary functioning kidney.

The treatment of renal artery stenosis by angioplasty and stenting is an effective and accepted alternative to surgery for the treatment of renovascular hypertension and preservation of renal function. We report the technical and clinical outcomes of renal artery stenting in patients with a solitary functioning kidney and renal artery stenosis. From October 1993 to November 1999, 30 stents were placed in the renal arteries of 27 patients (mean age 72+/-8 years) with a solitary functioning kidney and azotemia. The mean diameter renal artery stenosis was 86+/-14%. The mean preprocedure serum creatinine (Cr) level was 3.0+/-1.5 mg/dL (range 1.5-7.5 mg/dL), arterial blood pressure was 171+/-29/85+/-13 mmHg, and the number of antihypertensive drugs was 2.9+/-1.1. Indications for stenting were suboptimal balloon dilation (n = 16), intimal dissection (n = 6), and restenosis following angioplasty (n = 5). Atherosclerotic ostial lesions were present in 25 (93%) of 27 renal arteries. This represents the largest series of renal artery stenting in patients with a solitary functioning kidney, and demonstrates this treatment modality to be a relatively safe alternative to conventional surgery in this high-risk patient group. Most (74%) of the patients in this series had improved or stabilized renal function. Further efforts to define preprocedural indicators of success are necessary to identify the patients who may benefit from revascularization of their solitary kidney.

Aged↗
PubMed2001

Evaluation of thrombolysis in a porcine model of chronic deep venous thrombosis: an endovascular model.

PURPOSE: The advancement of catheter-based interventions for vascular recanalization has underscored the need for an experimental animal model of vascular thrombosis that can be used for the evaluation of interventional therapies. In this model, a porcine model of deep venous thrombosis with a novel endovascular technique was described, and the efficacy of thrombolytic therapy with urokinase was evaluated. METHODS: An endovascular device that consisted of a tapered polytetrafluoroethylene graft attached within a self-expanding nitinol stent was delivered to bilateral common iliac veins in 20 pigs. Venous thrombosis occurred as a result of flow stasis created by the intrastent stenosis. Catheter-directed pulse-spray thrombolysis with urokinase (250,000 units) and heparin (5000 IU) was performed on one limb while the contralateral limb received control saline solution. Thrombolysis was performed in 1 hour (n = 4), 8 hours (n = 4), 3 days (n = 4), 7 days (n = 4), and 14 days (n = 4) after the stent-graft deployment. Venography and intravascular ultrasound were used to evaluate the efficacy of thrombolysis. Light microscopy was used for histologic analysis of the thrombus. RESULTS: Complete thrombolysis was achieved in groups with deep vein thrombosis that were younger than 1 day. Angioplasty of the tapered stent-grafts in the completely thrombolysed iliac vein was successful in restoring venous flow. The efficacy of thrombolysis in 3-day, 7-day, and 14-day groups was 86% +/- 7%, 73% +/- 13%, and 42% +/- 23%, respectively. The thrombolytic efficacy was enhanced to 92% +/- 16% and 86% +/- 18% (P <.05) in 3-day and 7-day groups, respectively, when doses of the pulse-spray thrombolysis were doubled. Increased dosages of the thrombolytic agent, however, did not significantly enhance the thrombus dissolution in the 14-day group. CONCLUSION: The thrombolytic efficacy of urokinase correlated with the chronicity of deep venous thrombosis in our model. An increased dose of urokinase may be used to enhance the efficacy of thrombolysis in a 1-week-old thrombus.

Animals↗
PubMed2001

Endovascular revascularization of renal artery stenosis: technical and clinical results.

PURPOSE: The natural history of renal artery stenosis is progression with subsequent deterioration of kidney function and development of renovascular hypertension. Percutaneous transluminal renal angioplasty is effective in the treatment of nonostial lesions but less effective for ostial stenoses. Because of the poor technical success experienced with percutaneous transluminal renal angioplasty, stenting of ostial stenoses is becoming the standard of endovascular care. In this retrospective study we analyzed the technical and clinical outcomes after renal artery stenting in 73 consecutive patients. PATIENTS AND METHODS: From July 1992 to January 1999, 88 Palmaz stents were deployed in 85 renal artery stenoses in 73 patients, with a mean age of 67.9 +/- 9.4 years. Twelve patients (16%) underwent bilateral stent placement. Atheromatous lesions were the most prevalent (99%: 82% ostial, 16% nonostial). Most stents were implanted for suboptimal balloon dilation (52%) or dissection (24%). Mean percent stenosis was 86% +/- 12%. Renal insufficiency (creatinine level > or = 1.5 mg/dL) was present in 50 (68%) patients, and uncontrolled hypertension (systolic > or = 160 mm Hg or diastolic > or = 90 mm Hg with more than two medications) was present in 57 (78%). RESULTS: Primary technical success was achieved in 89%. At the initial procedure, three additional stents were placed for residual stenoses, and urokinase was used to treat one intraprocedural stent thrombosis, resulting in an assisted primary technical success rate of 94%. Major complications occurred in 9.1% of stents placed: access artery thrombosis (n = 4), renal artery extravasation (n = 1), renal artery thrombosis (n = 1), and hematoma requiring operation (n = 2). Long-term clinical data were available on 69 (95%) patients at 20 +/- 17 months. Overall, a significant decrease in systolic and diastolic pressures (P <.001) and reduction of medication (P <.01) were noted without a change in renal function (P = NS). Angiography was performed on 22 patients at 11.3 +/- 10.3 months for persistent or worsening renal function or hypertension or for other reasons; 10 patients had significant restenoses in 14 renal arteries. CONCLUSION: Our retrospective analysis demonstrates that endovascular stenting of renal artery stenosis in patients with poorly controlled hypertension or deteriorating renal function is a safe and effective alternative treatment to surgical management.

Adult↗
PubMed2001

Early experience with the bifurcated Excluder endoprosthesis for treatment of the abdominal aortic aneurysm.

PURPOSE: This report describes our initial experience with the modular, bifurcated Excluder endoprosthesis and its safety and efficacy in the primary endovascular repair of infrarenal abdominal aortic aneurysms (AAAs). METHODS: AAAs (mean diameter, 58.2 +/- 14.3 mm) were repaired in 19 patients with this device between March 1999 and January 2000. The mean age of patients was 71.8 +/- 8.4 years (range, 57-86 years). This modular device was inserted through an 18F introducer sheath placed in one femoral artery, and the contralateral artery was cannulated with a 12F introducer sheath. All procedures were performed in a standard operating room with angiographic capabilities. RESULTS: Endograft deployment was successful in all patients. The average surgical time was 135 +/- 37 minutes, with a mean blood loss of 229 +/- 138 mL. In eight patients, the use of either aortic or iliac extenders was required for enhanced sealing or additional length. An external iliac artery dissection occurring at the time of endograft insertion was successfully treated with a Wallstent. Type II leaks initially found to be present by means of intraoperative completion angiography had spontaneously thrombosed by the 1-month follow-up computed tomography scan. There was one perioperative death (5.3%). Complications included superficial wound infections (n = 3) and a nonfatal myocardial infarction (n = 1). The mean length of hospital stay was 2.9 +/- 1.2 days, and only six patients required intensive care. Endoleaks were seen in four patients (21%) by means of the 30-day computed tomography scan; three of these endoleaks had spontaneously sealed at the time of the 6-month follow-up examination (5.5% 6-month endoleak rate). Aneurysm size did not increase in the patients with leaks. CONCLUSION: The Excluder endoprosthesis was an effective means of excluding an infrarenal AAA from the systemic circulation in this selected group of patients. The smaller sheath sizes may increase the pool of potential candidates. Further study of this device is warranted, and continued assessment of the long-term durability of the device will be necessary.

Aged↗
PubMed2001

Intra-arterial thrombin injection of an ascending aortic pseudoaneurysm complicated by transient ischemic attack and rescued with systemic abciximab.

Thrombin injection as a means of inducing thrombus formation has recently received wide attention as an alternative treatment for pseudoaneurysm. We present a case of a 67-year-old man in whom a large mycotic pseudoaneurysm developed in the ascending aorta because of sternal osteomyelitis and mediastinitis after coronary artery bypass grafting. Transcatheter intra-arterial thrombin injection was performed, and it successfully induced pseudoaneurysm thrombosis. However, the procedure was complicated by a sudden transient ischemic attack caused by thrombus propagation into the cerebral circulation. Complete thrombus dissolution in the cerebral circulation with the resolution of neurologic symptoms was achieved by means of intravenous abciximab.

Abciximab↗
PubMed2001

Sloughing of the scrotal skin and impotence subsequent to bilateral hypogastric artery embolization for endovascular aortoiliac aneurysm repair.

Sloughing of the scrotal skin is an extremely rare event due to pelvic ischemia. We report herein one case of scrotal skin sloughing and impotence after bilateral hypogastric artery embolization for endoluminal aortoiliac aneurysm repair. Postoperative penile plethysmography demonstrated a 75% reduction in the penile brachial index, suggesting that pelvic ischemia is the main culprit for this complication. The devastating morbidity in our patient underscores the importance of maintaining pelvic collateral circulation when planning for endovascular aortoiliac aneurysm repair.

Aged↗
PubMed2001

Detection of isolated hook fractures 36 months after implantation of the Ancure endograft: a cautionary note.

Two cases of delayed (36-month) Ancure hook fracture are reported in patients who experienced a decrease in aneurysm size and no evidence of endoleak. Both devices used redesigned hooks and are otherwise identical to those devices currently used in clinical practice. Notably, hook fractures were not visualized on all abdominal radiographic views, nor were they noted on the final "institutional" report by the reviewing radiologist. Careful clinical follow-up with multiple-view abdominal radiographs remains essential for all patients treated with an endovascular graft, with particular attention directed to the integrity of the metal components. The broader clinical significance of this observation with respect to the Ancure endograft remains to be defined.

Aged↗
PubMed2001

Colonic necrosis subsequent to catheter-directed thrombin embolization of the inferior mesenteric artery via the superior mesenteric artery: a complication in the management of a type II endoleak.

The optimal management of endoleaks after endovascular repair of abdominal aortic aneurysms remains to be established. In this report, we describe a persistent side-branch, or type II, endoleak 1 year after endograft implantation treated with catheter-directed embolization of the aneurysm sac and the inferior mesenteric artery via the superior mesenteric artery, with embolization agents including thrombin, lipiodol, and gelfoam powder. Shortly after the embolization procedure, colonic necrosis developed in the patient, manifested by peritonitis, which necessitated a partial colectomy. This case underscores the devastating complication of colonic ischemia as a result of catheter-directed embolization of the inferior mesenteric artery in the management of an endoleak.

Aged↗
PubMed2001

Surgical intervention for complications caused by femoral artery catheterization in pediatric patients.

PURPOSE: This study evaluated the risk factors and surgical management of complications caused by femoral artery catheterization in pediatric patients. METHODS: From January 1986 to March 2001, the hospital records of all children who underwent operative repairs for complications caused by femoral artery catheterization were reviewed. A prospective cardiac data bank containing 1674 catheterization procedures during the study period was used as a means of determining risk factors associated with iatrogenic femoral artery injury. RESULTS: Thirty-six operations were performed in 34 patients (age range, 1 week-17.4 years) in whom iatrogenic complications developed after either diagnostic or therapeutic femoral artery catheterizations during the study period. Non-ischemic complications included femoral artery pseudoaneurysms (n = 4), arteriovenous fistulae (n = 5), uncontrollable bleeding, and expanding hematoma (n = 4). Operative repairs were performed successfully in all patients with non-ischemic iatrogenic femoral artery injuries. In contrast, ischemic complications occurred in 21 patients. Among them, 14 patients had acute femoral ischemia and underwent surgical interventions including femoral artery thrombectomy with primary closure (n = 6), saphenous vein patch angioplasty (n = 6), and resection with primary anastomosis (n = 2). Chronic femoral artery occlusion (> 30 days) occurred in seven patients, with symptoms including either severe claudication (n = 4) or gait disturbance or limb growth impairment (n = 3). Operative treatments in these patients included ileofemoral bypass grafting (n = 5), femorofemoral bypass grafting (n = 1), and femoral artery patch angioplasty (n = 1). During a mean follow-up period of 38 months, no instances of limb loss occurred, and 84% of children with ischemic complications eventually gained normal circulation. Factors that correlated with an increased risk of iatrogenic groin complications that necessitated surgical intervention included age younger than 3 years, therapeutic intervention, number of catheterizations (>or= 3), and use of 6F or larger guiding catheter. CONCLUSION: Although excellent operative results can be achieved in cases of non-ischemic complications, acute femoral occlusion in children younger than 2 years often leads to less satisfactory outcomes. Operative intervention can provide successful outcome in children with claudication caused by chronic limb ischemia. Variables that correlated with significant iatrogenic groin complications included a young age, therapeutic intervention, earlier catheterization, and the use of a large guiding catheter.

Acute Disease↗