Biomedical subjects

Charles Chan

Publications and source records attributed to Charles Chan.

14 recordsLinked to original sources

PubMed2006

Twelve-month outcomes with a paclitaxel-eluting stent transitioning from controlled trials to clinical practice (the WISDOM Registry).

The WISDOM Registry tracked clinical outcomes in patients receiving a slow-release, polymer-based, paclitaxel-eluting stent during the transition from randomized trials to commercial use in everyday interventional cardiology practice. Although randomized trials of drug-eluting stents have demonstrated the safety and effectiveness of these devices in less complicated, de novo lesions, observation of long-term clinical outcomes is required to monitor safety as use of this revolutionary technology expands to broader patient populations. In total, 778 patients were enrolled at 22 sites in 9 countries where the TAXUS paclitaxel-eluting stent first received market approval. Patients with de novo or restenotic coronary lesions eligible for stenting were enrolled. Clinical follow-up was conducted by telephone at 3, 6, 9, and 12 months after the procedure to capture reported stent thrombosis and major cardiac events (death, myocardial infarction, and reintervention on the target lesion). Clinical follow-up at 12 months was completed for 92% of patients. The 12-month rate of physician-reported major cardiac events was 5.2%, with a target lesion reintervention rate of 2.0%. The low overall stent thrombosis rate of 0.6% included no stent thromboses >30 days after the index procedure. Low target lesion reintervention rates were also observed in the high-risk subgroups: patients with diabetes (4.0%), vessels <2.5 mm (2.5%), lesions >20 mm (3.6%), and multiple stents in a lesion (1.4%). In conclusion, the paclitaxel-eluting TAXUS slow-release stent exhibits long-term safety and efficacy in uncomplicated and higher risk patients and lesions seen in everyday clinical practice.

Coronary Disease↗

PubMed2006

Musashi1 antigen expression in human fetal germinal matrix development.

Musashi1 is a highly conserved protein found in neural progenitor cells. We examined the expression dynamics of Musashi1 in conjunction with other representative neural progenitor antigenic determinants (Ki-67 and nestin) during 8 different stages of the developing human fetal germinal matrix. Our results indicate that Musashi1 is a useful marker for immature cells in periventricular areas inhabited by stem cells, progenitor cells, and differentiating cells.

Brain↗

PubMed2005

CpG Island microarray probe sequences derived from a physical library are representative of CpG Islands annotated on the human genome.

An effective tool for the global analysis of both DNA methylation status and protein-chromatin interactions is a microarray constructed with sequences containing regulatory elements. One type of array suited for this purpose takes advantage of the strong association between CpG Islands (CGIs) and gene regulatory regions. We have obtained 20,736 clones from a CGI Library and used these to construct CGI arrays. The utility of this library requires proper annotation and assessment of the clones, including CpG content, genomic origin and proximity to neighboring genes. Alignment of clone sequences to the human genome (UCSC hg17) identified 9595 distinct genomic loci; 64% were defined by a single clone while the remaining 36% were represented by multiple, redundant clones. Approximately 68% of the loci were located near a transcription start site. The distribution of these loci covered all 23 chromosomes, with 63% overlapping a bioinformatically identified CGI. The high representation of genomic CGI in this rich collection of clones supports the utilization of microarrays produced with this library for the study of global epigenetic mechanisms and protein-chromatin interactions. A browsable database is available on-line to facilitate exploration of the CGIs in this library and their association with annotated genes or promoter elements.

Base Sequence↗

PubMed2005

Low microsatellite instability is associated with poor prognosis in stage C colon cancer.

PURPOSE: The significance of low microsatellite instability (MSI-L) in colorectal cancer is poorly understood. No clear biologic distinction has been found between MSI-L and microsatellite stable (MSS) colorectal cancer, and these two phenotypes are usually combined when analyzed against the well-defined high MSI (MSI-H) phenotype. Evidence is emerging that an O(6)-methylguanine DNA methyltransferase (MGMT) gene defect is associated with MSI-L. Therefore, to further define this phenotype, we undertook a detailed analysis of the prognostic significance of MSI-L and loss of MGMT expression in colon cancer. PATIENTS AND METHODS: The study cohort was 183 patients with clinicopathologic stage C colon cancer who had not received adjuvant therapy. We analyzed MSI status, MGMT, and mismatch repair protein expression, as well as MGMT and p16 promoter hypermethylation. RESULTS: We showed that MSI-L defines a group of patients with poorer survival (P = .026) than MSS patients, and that MSI-L was an independent prognostic indicator (P = .005) in stage C colon cancer. Loss of MGMT protein expression was associated with the MSI-L phenotype but was not a prognostic factor for overall survival in colon cancer. p16 methylation was significantly less frequent in MSI-L than in MSI-H and MSS tumors and was not associated with survival. CONCLUSION: MSI-L characterizes a distinct subgroup of stage C colon cancer patients, including the MSI-L subset of proximal colon cancer, who have a poorer outcome. Neither the MGMT defect nor p16 methylation are likely to contribute to the worse prognosis of the MSI-L phenotype.

Adult↗

PubMed2005

Cardiogenic shock caused by severe coronary artery spasm immediately after coronary stenting.

Coronary artery spasm is common during percutaneous coronary intervention and is easily relieved by intracoronary administration of vasodilators. We report the case of a patient who had severe, protracted, generalized spasm of the entire left coronary artery system during coronary artery stenting. The spasm, which was unresponsive to intracoronary vasodilators administered via guiding catheter, resulted in pulmonary edema and cardiogenic shock. Local injection of nitroglycerin via a transit catheter in the coronary artery eventually resolved the spasm and reversed the cardiogenic shock. To our knowledge, this is the 1st report of such a case in the English-language medical literature.

Aged↗

PubMed2004

Six- and twelve-month results from first human experience using everolimus-eluting stents with bioabsorbable polymer.

BACKGROUND: Everolimus, an active immunosuppressive and antiproliferative agent of the same family as sirolimus (rapamycin), has demonstrated significant reduction of neointimal proliferation in animal studies. The First Use To Underscore restenosis Reduction with Everolimus (FUTURE) I trial was the first in-human experience to evaluate the safety and efficacy of everolimus-eluting stents (EES), coated with a bioabsorbable polymer, compared with bare metal stents (BMS). METHODS AND RESULTS: FUTURE I was a prospective, single-blind, randomized trial that enrolled 42 patients with de novo coronary lesions (EES 27, BMS 15). Patient and lesion characteristics were comparable between the groups. Major adverse cardiac event rates were low at 30 days and 6 months, without any early or late stent thrombosis for either group (P=NS). Between 6 and 12 months, there were no additional reports of major adverse cardiac events. The 6-month angiographic in-stent restenosis rate was 0% versus 9.1% (1 patient) (P=NS), with an associated late loss of 0.11 mm versus 0.85 mm (P<0.001), and the in-segment restenosis rate was 4% (1 patient) and 9.1% (1 patient) (P=NS) for EES and BMS, respectively. Intravascular ultrasound analysis revealed a significant reduction of percent neointimal volume in EES compared with BMS (2.9+/-1.9 mm3/mm versus 22.4+/-9.4 mm3/mm, P<0.001). There was no late stent malapposition in either group. The safety and efficacy of the EES appeared to be sustained at 12 months. CONCLUSIONS: In this initial clinical experience, EES with bioabsorbable polymer demonstrated a safe and efficacious method to reduce in-stent neointimal hyperplasia and restenosis.

Aged↗

PubMed2004

The NUGGET study: NIR ultra gold-gilded equivalency trial.

This study should clarify whether the gold-coated NIROYAL stent is equivalent to the stainless steel NIR stent. Patients were randomized to either NIR stent (n = 298) or a NIROYAL stent (n = 305). The primary endpoint was the minimum lumen diameter of the target lesion at 6 months postprocedure. Secondary endpoints focused on clinical events. At 30 days, adverse events were similar in both groups. At 6 months, the minimal lumen diameter was 1.83/1.64 mm (P < 0.001; 95% CI = 0.08-0.30) and the angiographic restenosis rate was 20.6%/37.7% (P < 0.001; 95% CI = -24.7 to -9.3) for NIR/NIROYAL. The 6-month MACE rates were NIR 7.4% and NIROYAL 10.5% (95% CI = -7.7 to 1.4). Compared to stainless steel stent, the NIROYAL stent demonstrated a smaller minimal lumen diameter, a higher late loss (i.e., higher neointimal hyperplasia in spite of a significantly better initial gain), with higher restenosis and similar MACE rates at 6 months.

Aged↗

PubMed2004

Acute and long-term clinical and angiographic outcome after S-Stent implantation: S-Stent multicenter safety and efficacy trial.

The purpose of this study is to demonstrate safety and effectiveness of the S-Stent in de novo coronary lesions treated with conventional percutaneous coronary balloon angioplasty. Between January 2000 and June 2001, 120 patients were prospectively enrolled at four study centers. Patients were treated with coronary stenting in a total of 137 lesions. Procedural success was achieved in 100% of 137 attempted lesions. Clinical success was 99.8%. In-hospital mortality was 0.8%; myocardial infarction occurred in 0.8% and stent thrombosis in 0.8%. After stent implantation, the minimal lumen diameter increased from 0.92 +/- 0.43 to 2.74 +/- 0.36 mm (P < 0.0001) and the percent diameter stenosis decreased from 68.0 +/- 16.2 to 4.5 +/- 12.0 (P < 0.0001). At 6-month follow-up, the percent diameter stenosis was 33.5 +/- 21.3 and the angiographic restenosis rate was 16.5%. Target lesion revascularization was required in 12 patients (10.1%). We conclude that the use of S-Stent for coronary intervention resulted in a high procedural success rate and low angiographic restenosis at 6 months after implantation.

Aged↗

PubMed2004

Combined fibrinolysis using reduced-dose alteplase plus abciximab with immediate rescue angioplasty versus primary angioplasty with adjunct use of abciximab for the treatment of acute myocardial infarction: Asia-Pacific Acute Myocardial Infarction Trial (APAMIT) pilot study.

We conducted a randomized feasibility pilot study comparing combined fibrinolysis with immediate rescue angioplasty vs. primary angioplasty with adjunctive abciximab in patients with acute myocardial infarction (AMI). Seventy patients with ST segment elevation AMI of </= 6 hr were randomized to either 50 mg of alteplase and abciximab (n = 34) or primary angioplasty with adjunctive abciximab (n = 36). Coronary angiography was performed at 60 min in the combined lytic group and TIMI 3 flow was present in 65% of patients as compared to 25% (P = 0.001) in the primary angioplasty group prior to intervention. Treatment success, defined as TIMI 3 flow, was achieved in 83% of patients in the primary angioplasty group (P = 0.075 compared to 65% in combined lytic group before rescue angioplasty). There was no difference in overall treatment success between primary angioplasty and combined lytic group with rescue angioplasty (83% vs. 94%; P = NS). Major adverse cardiac events at 1 month were not significant (15% vs. 11%; P = NS), but there was a trend toward more events in the combined lytic group at 6 months (32% vs. 14%; P = 0.066), particularly in target vessel revascularization. In this feasibility pilot study, high rate of TIMI 3 flow was attained in patients with AMI with both combined fibrinolysis and primary angioplasty with adjunctive abciximab. A larger randomized trial is currently ongoing to compare these two strategies.

Abciximab↗

PubMed2003

Chronic arterial responses to polymer-controlled paclitaxel-eluting stents: comparison with bare metal stents by serial intravascular ultrasound analyses: data from the randomized TAXUS-II trial.

BACKGROUND: Polymer-controlled paclitaxel-eluting stents have shown a pronounced reduction in neointimal hyperplasia compared with bare metal stents (BMS). The aim of this substudy was to evaluate local arterial responses through the use of serial quantitative intravascular ultrasound (IVUS) analyses in the TAXUS II trial. METHODS AND RESULTS: TAXUS II was a randomized, double-blind study with 536 patients in 2 consecutive cohorts comparing slow-release (SR; 131 patients) and moderate-release (MR; 135 patients) paclitaxel-eluting stents with BMS (270 patients). This IVUS substudy included patients treated with one study stent who underwent serial IVUS examination after the procedure and at 6-month follow-up (BMS, 152 patients; SR, 81; MR, 81). The analyzed stented segment (15 mm) was divided into 5 subsegments in which mean vessel area (VA), stent area (SA), lumen area (LA), intrastent neointimal hyperplasia area (NIHA), and peristent area (VA-SA) were measured. NIHA was significantly reduced in SR (0.7+/-0.9 mm2, P<0.001) and MR (0.6+/-0.8 mm2, P<0.001) compared with BMS (1.9+/-1.5 mm2), with no differences between the two paclitaxel-eluting release formulations. Longitudinal distribution of neointimal hyperplasia throughout the paclitaxel-eluting stent was uniform. Neointimal growth was independent of peristent area at postprocedure examination in all groups. There were progressive increases in peristent area from BMS to SR to MR (0.5+/-1.7, 1.0+/-1.8, and 1.4+/-2.0 mm2, respectively; P<0.001). The increase in peristent area was directly correlated with increases in VA. CONCLUSIONS: Both SR and MR paclitaxel-eluting stents prevent neointimal formation to the same degree compared with BMS. However, the difference in peristent remodeling suggests a release-dependent effect between SR and MR.

Angioplasty↗

PubMed2003

GI complications after lung transplantation in patients with cystic fibrosis.

STUDY OBJECTIVE: Lung transplantation is now available for patients with cystic fibrosis (CF) and end-stage lung disease. While pulmonary graft function is often considered the major priority following transplantation, the nonpulmonary complications of this systemic disease also continue. We examined the GI complications in a cohort of patients who underwent transplantation. DESIGN: This was a retrospective study of all patients with CF who underwent transplantation between March 1988 and December 1998 in Toronto. Medical records were reviewed, and a short questionnaire was mailed to patients who were alive as of December 1998. RESULTS: There were 80 bilateral lung transplants performed in 75 patients. The questionnaire was distributed to 43 patients, of whom 27 patients (63%) responded. Pancreatic insufficiency requiring enzyme intake was evident in 72 of 75 patients (96%) at the time of surgery. Of three pancreatic-sufficient patients (4%), pancreatic insufficiency was diagnosed in two patients later. Biliary cirrhosis was diagnosed in three patients prior to transplantation. Distal intestinal obstruction syndrome (DIOS) was recorded for 15 patients (20%). Ten patients had a single episode, of which eight episodes occurred early in the postoperative period. Five patients had recurrent episodes. All were medically treated, except for two patients who underwent surgery. Other complications included cholecystitis (n = 3), mucocele of the appendix (n = 1), peptic ulcer disease (n = 3), and colonic carcinoma (n = 1). CONCLUSION: GI complications after lung transplantation are common in patients with CF, and attention should be paid to the risk for DIOS in the early postoperative period. Prevention and early medical treatment are important in order to avoid acute surgery. Close collaboration with the CF clinic, in order to diagnose and treat CF-related complications, is recommended.

Adult↗

PubMed2003

Coronary intervention with a heparin-coated stent and aspirin only.

OBJECTIVES: To determine the safety and efficacy of a post-stenting anti-platelet regimen of aspirin without additional ticlopidine or clopidogrel after successful heparin-coated stent implantation. METHODS: A prospective, non-randomized, multi-center pilot study of patients undergoing percutaneous coronary intervention, including those with acute coronary syndromes and small vessels with one-month clinical follow-up, was undertaken. Patients received a heparin-coated stent and were treated with aspirin only. RESULTS: Over a period of 6 months, a total of 122 patients were recruited in 6 centers. Their mean age was 57.2 10.0 years, 79% were male and 31% had unstable angina. Most (75%) had single-vessel disease, predominantly of the left anterior descending artery (51%), with a mean reference diameter of 2.44 mm 0.44 mm at baseline and 2.48 0.41 mm post stenting. At a 1-month clinical follow-up, no major adverse cardiovascular events (including subacute stent thrombosis) had occurred. Five patients were readmitted to hospital for symptoms unrelated to the interventional procedure. CONCLUSIONS: Heparin-coated stent implantation using an antiplatelet regimen of aspirin only, appears to be safe and feasible. A randomized trial of a larger number of patients appears warranted.

Adult↗

PubMed2002

Six-month angiographic and 12-month clinical follow-up of MultiLink long (25 to 35 mm) stents for long coronary narrowings in patients with angina pectoris.

There are limited prospective angiographic data on stent deployment for long coronary lesions. This multicenter prospective study enrolled 120 patients with a single de novo stenosis >20 mm in length, in a native vessel > or =3 mm diameter, suitable for a MultiLink stent 25 to 35 mm in length with additional stent deployment if required. Quantitative angiography before and immediately after stenting and at 6-month follow-up assessed restenosis for the complete lesion and for 5-mm segments of the stented and adjacent nonstented vessel. By 1 year, myocardial infarction had occurred in 3% and target vessel repeat revascularization in 12% of patients. The mean stented length (35.8 +/- 14.6 mm) closely matched mean lesion length (30.1 +/- 13.5 mm). Restenosis to > or =50% diameter loss occurred in 32% of patients, but to > or =70% in only 8%. Of the 147 segments (5 mm in length) with baseline stenosis <25%, only 3 patients (2%) developed restenosis of > or =50%, and only in 1 of these was it > or =70%. Stenting of long narrowings is associated with good clinical outcome and a low rate of severe restenosis. Mildly diseased segments of long lesions covered by a stent rarely became severely narrowed and had negligible influence on the overall restenosis rate. These data support a strategy of full lesion coverage by stent deployment.

Adult↗

PubMed2002

Thrombin generation and fibrinolytic activities among patients receiving reduced-dose alteplase plus abciximab or undergoing direct angioplasty plus abciximab for acute myocardial infarction.

The purpose of this study was to determine the impact of these 2 reperfusion strategies (reduced-dose alteplase plus abciximab or direct angioplasty plus abciximab) on fibrinolytic and thrombin generation activities. The effect of reduced-dose alteplase plus abciximab and direct angioplasty plus abciximab on hemostatic factors is unknown. Of 70 patients with acute myocardial infarction of < or = 6 hours, 34 were randomized to reduced-dose alteplase (35 to 50 mg in 1 hour) and 36 to direct angioplasty. A standard bolus and infusion dose of abciximab was administered to all patients. Blood specimens were collected at baseline, and at 1, 4, 12, and 24 hours. The following parameters were assayed: fibrinogen, plasminogen and antiplasmin activities, tissue plasminogen activator antigen, D-dimer, prothrombin fragments F1 + 2, and thrombin/antithrombin III complexes. Among patients treated with reduced-dose alteplase plus abciximab, the fibrinogen level decreased by 28.4% in the first hour (11.7 +/- 3.4 vs 7.8 +/- 2.5 micromol/L, p <0.001). Correspondingly, plasminogen and antiplasmin activities decreased by 43.8% (p <0.001) and 59.1% (p <0.001), respectively. Prothrombin fragments F1 + 2 increased from 2.2 +/- 1.7 to 4.2 +/- 1.6 nmol/L (1 hour) (p <0.001) and thrombin/antithrombin III increased from 16.3 +/- 15.0 to 33.5 +/- 19.9 microg/L (1 hour) (p <0.001). Conversely, in the direct angioplasty group, there was a marginal elevation in fibrinogen level at 1 hour (10.2 +/- 2.4 vs 10.6 +/- 2.0 micromol/L, p = 0.064) despite a significant reduction in plasminogen and an increase in tissue plasminogen activator levels. There was no significant change in prothrombin fragments F1 + 2 and thrombin/antithrombin III levels. Thus, there was considerable fibrinolytic activity with reduced-dose alteplase plus abciximab; thrombin generation was not prevented. Among patients treated with direct angioplasty, there was some endogenous fibrinolytic activity, but there was no significant thrombin generation.

Abciximab↗