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Wai-Hong Chen

Publications and source records attributed to Wai-Hong Chen.

17 recordsLinked to original sources
PubMed2006

Aspirin resistance or variable response or both?

Numerous clinical trials have demonstrated that aspirin is effective in secondary prevention and in high-risk primary prevention of adverse cardiovascular events. However, a constellation of clinical and laboratory evidence exists that demonstrates diminished or absent response to aspirin in some patients. This has led to the concept of "aspirin resistance," which is a poorly defined, somewhat misleading term. The mechanism for aspirin resistance has not been fully established, but it is almost certainly due to a combination of clinical, biological, and genetic properties affecting platelet function. There are no criteria for distinguishing true resistance from treatment failure, and there is no consensus on whether the definition of aspirin resistance should be based on clinical outcomes, laboratory evidence, or both. Studies in large populations are needed to define antiplatelet resistance using consistent and reproducible assays and correlate the measurements with clinical outcomes. One such prospective randomized trial is completed, and 2 others are under way: the Clopidogrel for High Atherothrombotic Risk and Ischemic Stabilization, Management, and Avoidance (CHARISMA) trial compared clopidogrel and aspirin with placebo and aspirin for high-risk primary or secondary prevention, and the Aspirin Nonresponsiveness and Clopidogrel Endpoint Trial (ASCET) is evaluating whether switching to clopidogrel will be superior to continued aspirin therapy in improving clinical outcomes in aspirin-resistant patients with angiographically documented coronary artery disease. The Research Evaluation to Study Individuals Who Show Thromboxane or P2Y(12) Receptor Resistance (RESISTOR) trial is investigating whether modifying antiplatelet regimens could prevent myonecrosis after percutaneous coronary intervention in patients with aspirin and clopidogrel resistance.

Aspirin↗
PubMed2006

Incidence and predictors of upper gastrointestinal bleeding in patients receiving low-dose aspirin for secondary prevention of cardiovascular events in patients with coronary artery disease.

AIM: The use of low-dose aspirin to prevent cardiovascular disease events is well established. However, the incidence and predictors of upper gastrointestinal bleeding (UGIB) with its use are unknown. We studied prospectively the incidence and outcome of peptic ulceration in low-dose aspirin users. METHODS: A total of 991 patients with coronary artery disease (CAD) on low-dose aspirin were prospectively followed-up for two years for the occurrence and clinical features of first hospitalized episode of UGIB. RESULTS: UGIB had a bimodal presentation with 45% occurring within four months of aspirin initiation and had an overall prevalence of 1.5% per year. There was no UGIB-related death. Hypertension (OR = 4.6, 95%CI 1.5-14.7, P = 0.009), history of peptic ulceration (OR = 3.1, 95%CI 1.1-9.0, P = 0.039), tertiary education (OR = 3.08, 95%CI 1.1-9.0, P = 0.039) and higher lean body mass (P = 0.016) were independent factors associated with UGIB. Use of nitrate did not reduce UGIB. CONCLUSION: The incidence of UGIB in patients with CAD on long-term low-dose aspirin is low, but is accompanied with significant morbidity. With prolonged use of aspirin, UGIB continues to be a problem for those with risk factors and especially in patients with a history of peptic ulcers, in which UGIB tends to occur early after aspirin therapy.

Aged↗
PubMed2006

Antiplatelet resistance with aspirin and clopidogrel: is it real and does it matter?

Platelets play a pivotal role in the pathophysiology of ischemic complications of atherosclerotic cardiovascular disease. Aspirin and clopidogrel are oral antiplatelet drugs that have been shown to reduce adverse clinical events across the wide spectrum of patients with atherothrombotic disease. However, recurrent ischemic events still occur in a significant proportion of patients despite treatment with these antiplatelet drugs. The concept of antiplatelet resistance therefore emerges. Although uniform definitions and standardized assays are not yet available, numerous studies have documented the interindividual variability in platelet responsiveness to oral antiplatelet drugs. Evidence is also accumulating to demonstrate that hyporesponsiveness to antiplatelet drugs in the laboratory (ie, resistance) is associated with adverse clinical events in different patient populations. Clinical application of antiplatelet resistance will require proof from prospective randomized trials that modifications of antiplatelet therapy based on tests of antiplatelet responsiveness will improve the outcomes of patients with antiplatelet resistance.

Aspirin↗
PubMed2006

Prediction of aortic augmentation index using radial pulse transmission-wave analysis.

OBJECTIVE: Current arterial transfer functions have low capability in predicting aortic augmentation index (AIx) from radial pulse contour (RPC), because of the difficulty in accurately identifying the merging point (inflection point) in the derived aortic pulse contour (APC). We hypothesize that the formation time between each characteristic wave in APC is about one-third of ejection duration (ED/3). We sought to assess the accuracy of ED/3 in identifying the merging point in APC as compared to the conventional differential method. In addition, we sought to derive the AIx from RPC based on an arterial transfer function and the ED/3 method. METHODS: APC and RPC sequences were measured digitally and simultaneously in 60 subjects (37 males; aged 60 +/- 10 years). An ensemble-averaged RPC-to-APC transfer function was determined from 30 randomly selected subjects and was used to derive APC sequences in the 30 additional subjects. The accuracy of AIx predicted from RPC was determined. RESULTS: In patients with a clearly identifiable merging point in APC, the ED/3 method identified the merging point of measured APC within 1.97 +/- 0.60 ms of that identified by the conventional differential method, with identical AIx. The AIx and merging point of derived APC using the ED/3 method were also within 0.22 +/- 1.01% and 1.81 +/- 1.64 ms, respectively, of those of the measured APC using the conventional differential method. The accuracy of the predicted AIx was independent of age, sex, body-mass index and presence of hypertension. CONCLUSION: In a quiet resting state, the ED/3 is an alternative method for identifying the merging point in APC. In conjunction with transfer-function technique, AIx can be derived accurately from RPC.

Adult↗
PubMed2005

Relation of aspirin resistance to coronary flow reserve in patients undergoing elective percutaneous coronary intervention.

Previous studies have shown that more complete platelet inhibition improves the coronary flow reserve (CFR), a measure of microvascular integrity, in patients undergoing percutaneous coronary intervention (PCI). We hypothesized that patients with aspirin resistance would have impaired CFR after elective PCI. We used VerifyNow Aspirin to determine the response to aspirin in 117 consecutive patients who underwent elective single-lesion PCI. The assay results are expressed quantitatively in Aspirin Reaction Units based on the degree of platelet aggregation. All patients received a 300-mg loading dose of clopidogrel >12 hours before and a 75-mg maintenance dose the morning of PCI. CFR was estimated using the Thrombolysis In Myocardial Infarction frame count method. Of the 117 patients, 22 (18.8%) were aspirin resistant. The clinical, angiographic, and procedural characteristics of the aspirin-sensitive and -resistant patients were balanced. All patients underwent successful PCI with <50% residual diameter stenosis and Thrombolysis In Myocardial Infarction grade 3 flow after PCI. Aspirin-resistant patients had a lower CFR than the aspirin-sensitive patients (1.42 +/- 0.35 vs 1.80 +/- 0.64, p = 0.018). Univariate correlates of CFR included the Aspirin Reaction Unit (r = -0.227, p = 0.014) and post-PCI creatine kinase-MB elevation (p = 0.048). Multivariate linear regression analysis revealed the Aspirin Reaction Unit to be the only independent determinant of CFR after PCI (r2 = 0.051, p = 0.014). Thus, aspirin resistance was associated with impaired CFR in patients who underwent elective PCI, implicating insufficient aspirin-induced platelet inhibition as a cause of microvascular dysfunction by distal atherothrombotic embolization and/or spasm.

Aged↗
PubMed2005

Morphometric analysis of particulate debris extracted by four different embolic protection devices from coronary arteries, aortocoronary saphenous vein conduits, and carotid arteries.

Different embolic protection devices have been introduced for endovascular interventions: filters or balloon occlusion and aspiration systems. Despite widening use in a variety of vascular beds and clinical syndromes, little is known about the particulate burden liberated from different vascular beds and caught by different protection devices. We performed histologic and morphometric analyses of particulate debris captured during stenting of degenerated saphenous vein bypass grafts and native coronary arteries during acute myocardial infarction or during elective intervention and carotid arteries to assess the relative performance of different protection devices. We analyzed 232 interventions (90 saphenous vein bypass grafts, 77 native coronary arteries, and 65 carotid arteries) with 4 different devices (65 FilterWires, 99 Interceptors, 41 GuardWires, and 27 Proxis catheters) using the RapidVue particle analyzer. No difference in embolic volume retrieved was demonstrated between devices in saphenous vein bypass grafts and carotid interventions. A smaller volume of particulate debris was retrieved by the GuardWire compared with the FilterWire and the Proxis catheter in native coronary artery interventions. The Interceptor and the GuardWire captured more smaller particles than did the FilterWire or Proxis catheter. During saphenous vein bypass graft or carotid intervention, different embolic protection strategies were performed similarly. In native coronary artery stenting, however, proximal embolic protection retrieved larger amounts of debris than did distal filters or occlusion devices. These data may allow greater tailoring of embolic protection device development and application in specific anatomic locales.

Arterial Occlusive Diseases↗
PubMed2005

Low-dose aspirin increases aspirin resistance in patients with coronary artery disease.

PURPOSE: We sought to investigate the association of aspirin dose and aspirin resistance in stable coronary artery disease patients measured by a point-of-care assay. METHODS: We studied 468 consecutive stable coronary artery disease patients in a referral cardiac center who were taking aspirin 80 to 325 mg daily for > or =4 weeks. The VerifyNow Aspirin (Ultegra RPFA-ASA, Accumetrics Inc, San Diego, Calif) was used to determine aspirin responsiveness. An aspirin reaction unit (ARU) > or =550 indicates the absence of aspirin-induced platelet dysfunction, based on correlation with epinephrine-induced light transmission aggregometry. Demographic and clinical data were collected to analyze the predictors of aspirin resistance. RESULTS: Aspirin resistance was noted in 128 (27.4%) patients. Univariate predictors of aspirin resistance include elderly (P = 0.002), women (P <0.001), anemia (P <0.001), renal insufficiency (P = 0.009) and aspirin dose < or =100 mg (P = 0.004). Multivariate analysis revealed hemoglobin (odds ratio [OR] 0.6; 95% confidence interval [CI] 0.51 to 0.69; P <0.001) and aspirin dose < or =100 mg (OR 2.23; 95% CI 1.12 to 4.44; P = 0.022) to be independent predictors of aspirin resistance. Daily aspirin dose < or = 100 mg was associated with increased prevalence of aspirin resistance compared with 150 mg and 300 mg daily (30.2% vs 16.7% vs 0%, P = 0.0062). CONCLUSION: A 100 mg or less daily dose of aspirin, which may have lower side effects, is associated with a higher incidence of aspirin resistance in patients with coronary artery disease. Prospective randomized studies are warranted to elucidate the optimal aspirin dosage for preventing ischemic complications of atherothrombotic disease.

Aged↗
PubMed2005

A randomized, double-blind, placebo-controlled trial of abciximab for prevention of in-stent restenosis in diabetic patients after coronary stenting: results of the ASIAD (Abciximab in Stenting Inhibits restenosis Among Diabetics) Trial.

OBJECTIVES: Coronary stenting is associated with a high incidence of restenosis in patients with diabetes mellitus. Recent data suggest that diabetic patients treated with abciximab have a lower rate of target vessel revascularization (TVR). We sought to investigate whether abciximab can reduce in-stent restenosis after coronary stenting in diabetic patients. METHODS: In this prospective double-blind trial, we randomly assigned 254 patients with type 2 diabetes mellitus undergoing nonurgent coronary stenting to receive abciximab with an initial heparin bolus of 50 U/kg (n = 128) or placebo with an initial heparin bolus of 70 U/kg (n = 126). All patients received aspirin and clopidogrel before the procedure. The primary endpoint was angiographic restenosis by quantitative coronary angiography at 6 months. The secondary endpoint was death, myocardial infarction (MI), or target lesion revascularization (TLR) at 6 months. RESULTS: The clinical, angiographic, and procedural characteristics were matched between the 2 groups. Angiographic follow-up was completed in 226 patients (90%). Angiographic restenosis occurred in 29.1% of the abciximab group, and 24% of the placebo group (p = 0.30). The rates of the secondary endpoint were similar between the 2 groups (23.4% in the abciximab group versus 22.2% in the placebo group; p = 0.88). TLR was performed on 36 (18.4%) lesions in 29 (23.4%) patients of the abciximab group, and 26 (13.6%) lesions in 23 (18.3%) patients of the placebo groups, respectively (p = 0.21 and 0.35, respectively). CONCLUSIONS: Abciximab does not reduce angiographic restenosis or TLR in type 2 diabetic patients undergoing nonurgent coronary stenting.

Abciximab↗
PubMed2004

Aspirin resistance is associated with a high incidence of myonecrosis after non-urgent percutaneous coronary intervention despite clopidogrel pretreatment.

OBJECTIVES: We sought to investigate the effect of aspirin resistance on the incidence of myonecrosis after non-urgent percutaneous coronary intervention (PCI) among patients pretreated with clopidogrel. BACKGROUND: Oral antiplatelet therapy using aspirin and a thienopyridine is the standard of care for preventing thrombotic complications of PCI. The effect of aspirin resistance on the outcomes of patients undergoing PCI is unknown. METHODS: We used the Ultegra Rapid Platelet Function Assay-ASA (Accumetrics Inc., San Diego, California) to determine aspirin responsiveness of 151 patients scheduled for non-urgent PCI. All patients received a 300-mg loading dose of clopidogrel >12 h before and a 75-mg maintenance dose in the morning of the PCI. The incidence of myonecrosis was measured by creatine kinase-myocardial band (CK-MB) and by troponin I (TnI) elevations after PCI. RESULTS: A total of 29 (19.2%) patients were noted to be aspirin-resistant. There was a significantly higher incidence of female subjects in the aspirin-resistant versus aspirin-sensitive groups. The incidence of any CK-MB elevation was 51.7% in aspirin-resistant patients and 24.6% in aspirin-sensitive patients (p = 0.006). Elevation of TnI was observed in 65.5% of aspirin-resistant patients and 38.5% of aspirin-sensitive patients (p = 0.012). Multivariate analysis revealed aspirin resistance (odds ratio [OR] 2.9; 95% confidence interval [CI] 1.2 to 6.9; p = 0.015) and bifurcation lesion (OR 2.8; 95% CI 1.3 to 6.0; p = 0.007) to be independent predictors of CK-MB elevation after PCI. CONCLUSIONS: Despite adequate pretreatment with clopidogrel, patients with aspirin resistance as measured by a point-of-care assay have an increased risk of myonecrosis following non-urgent PCI.

Aged↗
PubMed2004

Safety and feasibility of the use of a distal filter protection device in percutaneous revascularization of small coronary arteries.

The FilterWire EX is one of the filter protection devices developed as alternatives to balloon occlusion system for percutaneous coronary intervention. Its use has been recommended in vessels between 3.5 and 5.5 mm in diameter and no data are available on its use in smaller vessels. We evaluated the safety and feasibility of using FilterWire EX in native coronary arteries smaller than 3.5 mm. We successfully deployed and retrieved the FilterWire EX in 49 coronary arteries with a mean vessel diameter of 2.62 +/- 0.45 mm at device deployment. Reversible vasospasm was observed in 24 (50%) vessels, coronary flow was temporarily reduced in 22 (44.9%), and distal embolization was noted in 2 (4%). There was no vessel dissection induced by the device. These data suggest that it is safe and feasible to use the FilterWire EX in small coronary arteries.

Coronary Angiography↗
PubMed2004

Concomitant coronary and subclavian steal caused by ipsilateral subclavian artery stenosis and arteriovenous fistula in a hemodialysis patient.

Patients with chronic renal failure, because of concomitant conventional cardiovascular and uremia-associated risk factors, are at risk of developing diffuse and accelerated atherosclerosis involving both the coronary and peripheral territories. We report an end-stage renal failure patient with a history of coronary artery bypass surgery who developed both angina and dizziness during hemodialysis via a left forearm arteriovenous fistula. Magnetic resonance imaging diagnosed the presence of significant subclavian artery stenosis. The patient then underwent successful percutaneous stenting of the left subclavian artery. His angina and dizziness symptoms resolved subsequently.

Aged↗
PubMed2003

Initial experience and safety in the treatment of chronic total coronary occlusions with a new optical coherent reflectometry-guided radiofrequency ablation guidewire.

The Safe-Cross wire system, which has optical coherence reflectometry technology for navigating and radiofrequency energy provided at its tip for crossing chronic total occlusions (CTOs), provides a promising means to treat hard, organized CTOs. Using this system, we report on a 60% success rate in patients who had long-standing coronary CTOs that had > or =1 failed attempt using conventional percutaneous coronary intervention.

Aged↗
PubMed2003

Percutaneous recanalization of chronic subclavian artery occlusion using optical coherence reflectometry-guided radiofrequency ablation guidewire.

Subclavian artery lesion that is associated with low complication rate could be treated by percutaneous intervention effectively. However, the success of endovascular therapy for occlusive lesion may be limited by failure to cross with a guidewire. We describe the use of a system using optical coherence reflectometry for navigation and radiofrequency ablation to enable wire passage through subclavian artery occlusion that could not be crossed by conventional guidewires.

Arterial Occlusive Diseases↗
PubMed2003

Advances in antithrombin therapy for ST-elevation myocardial infarction.

Thrombin is a pivotal molecule in acute myocardial infarction (MI) because of its extensive procoagulant and prothrombotic actions. Antithrombin therapy is an important component of the pharmacotherapy for acute MI. The standard agent used in clinical practice, unfractionated heparin (UFH), is associated with the disadvantages of variable anticoagulant effect, inability to inhibit clot-bound thrombin, neutralization by platelet factor 4, and the propensity to cause thrombocytopenic complications. Novel thrombin inhibitors have been developed to overcome these disadvantages. Although possessing the property of inhibiting both fluid-phase and clot-bound thrombin, the direct thrombin inhibitor hirudin has been shown to give marginal benefits over UFH as adjunct to fibrinolysis in ST-elevation MI. Bivalirudin, another direct thrombin inhibitor, is able to reduce reinfarction in patients treated with streptokinase and is a new anticoagulant treatment option in this setting. The pharmacokinetic characteristics of better availability, longer half-life, and dose-independent clearance together with the ability of inhibiting both thrombin generation and activity make the low-molecular-weight heparins (LMWHs) an attractive alternative to UFH. The favorable benefit/risk profile of the LMWHs as adjunct to different generations of fibrinolytic agents is setting the stage for larger clinical trials to confirm their role as the antithrombin agent of choice for STEMI.

Anticoagulants↗
PubMed2002

Stable and optimal anticoagulation is achieved with a single dose of intravenous enoxaparin in patients undergoing percutaneous coronary intervention.

This study assessed the pharmacokinetics, safety and efficacy of intravenous enoxaparin in patients undergoing percutaneous coronary intervention (PCI). Sixty consecutive patients [(age, 62 11 years; female, 16%; diabetes, 18%; hypertension, 53%; prior myocardial infarction (MI), 43%] undergoing PCI (stable angina, 89%; stent, 92%; two-vessel disease, 23%; B2/C lesions, 45%) were administered intravenous enoxaparin 1 mg/kg for procedural anticoagulation. Blood samples for anti-Xa level and activated partial thromboplastin time (aPTT) were assayed from the first 20 patients before and after enoxaparin administration at the following intervals: 5, 30, 60, 90, 120, 150, 180, 210, 240, 360 and 480 minutes. Activated clotting time was assessed 5 minutes after enoxaparin administration. Bleeding complications were classified according to Thrombolysis In Myocardial Infarction (TIMI) criteria. All patients were monitored for adverse clinical events at clinic visit 4 8 weeks after hospital discharge. No TIMI major or minor bleedings occurred during hospitalization for the PCI (median stay post-PCI = 1 day). One patient (2%) developed a non-Q wave MI after the PCI and before hospital discharge. There was no death or urgent revascularization up to clinical follow-up. The peak anti-Xa level was 1.30 0.18 IU/ml (range, 1.03 1.69 IU/ml). The minimum anti-Xa level was 0.55 IU/ml 4 hours after enoxaparin. Thus, the use of intravenous enoxaparin in patients undergoing PCI is associated with a low incidence of ischemic and bleeding complications. A stable therapeutic anticoagulant effect is provided without the need for monitoring within 4 hours of enoxaparin administration.

Aged↗