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Biomedical subjects

Todd J Anderson

Publications and source records attributed to Todd J Anderson.

At least 37 records · Page 2Linked to original sources
PubMed2004

Coronary flow velocity reserve does not correlate with TIMI frame count in patients undergoing non-emergency percutaneous coronary intervention.

OBJECTIVES: The purpose of this research was to compare the Thrombolysis In Myocardial Infarction (TIMI) frame count (CTFC) with coronary flow velocity reserve (CFVR) in patients undergoing percutaneous coronary intervention (PCI). BACKGROUND: The relationship between CTFC and CFVR has not been adequately assessed in patients with coronary artery disease. METHODS: We studied 62 patients who underwent successful non-emergent PCI. All patients had Doppler evaluation of CFVR, CTFC, and quantitative coronary angiography. In an additional 17 patients, a frame count reserve was calculated as baseline CTFC/CTFC at peak hyperemia, induced by intracoronary adenosine after PCI. RESULTS: The CTFC decreased from 27 +/- 13 to 18 +/- 8, and CFVR increased from 1.5 +/- 0.4 to 2.6 +/- 0.7 (both p < 0.0001). The pre-PCI CTFC and the CFVR were closely related to minimal lumen diameter (p < 0.0001). After PCI, there was no correlation between CFVR and CTFC. In addition, no relationship was observed between CFVR and the frame count reserve. CONCLUSIONS: There was no significant correlation between CFVR and CTFC in patients undergoing coronary intervention. The relative utility of these measures in predicting outcomes in this setting requires further evaluation, but CTFC (or frame count reserve) does not appear to be an adequate surrogate measure of Doppler-derived CFVR.

Adenosine↗
PubMed2004

Cross-sectional evaluation of brachial artery flow-mediated vasodilation and C-reactive protein in healthy individuals.

AIMS: The present study was designed to (a) examine the interrelationship between endothelial function and CRP in healthy individuals and (b) evaluate the relationship of each biomarker towards global Framingham risk scores. METHODS AND RESULTS: Brachial artery flow-mediated vasodilatation (FMD), CRP, and traditional cardiovascular risk factors were measured in the Firefighters and Their Endothelium (FATE) study, which recruited 1154 male participants (mean age 47.4+/-9.8 years) with no known history of cardiovascular disease. No relationship was observed between FMD and CRP (p = 0.96). FMD and the Framingham risk score tended to correlate but not significantly (p = 0.07). A lower FMD was related to a higher systolic and diastolic blood pressure (p < 0.001 and p = 0.002, respectively) in the univariate analysis, and higher systolic blood pressure (p = 0.001) in the multivariate analysis. Elevated CRP levels independently correlated most closely with overall Framingham risk score (r = 0.36, p < 0.001) and a weaker although statistically significant relationship was seen with individual traditional cardiovascular risk factors (p < 0.005). CONCLUSIONS: The current study provided evidence that brachial artery FMD had no relationship to CRP in a large cohort of healthy subjects. These observations suggest that the predictive value of CRP may be largely independent of abnormalities in endothelial function. The additive prognostic value of endothelial vasodilator testing remains to be established.

Blood Flow Velocity↗
PubMed2004

The endothelium in health and disease: a discussion of the contribution of non-nitric oxide endothelium-derived vasoactive mediators to vascular homeostasis in normal vessels and in type II diabetes.

Endothelial dysfunction is considered as a major risk factor of cardiovascular complications of type I and types II diabetes. Impaired endothelium-dependent vasodilatation can be directly linked to a decreased synthesis of the endothelium-derived nitric oxide (NO) and/or an increase in the production of reactive oxygen species such as superoxide. Administration of tetrahydrobiopterin, an important co-factor for the enzyme nitric oxide synthase (NOS), has been demonstrated to enhance NO production in prehypertensive rats, restore endothelium-dependent vasodilatation in coronary arteries following reperfusion injury, aortae from streptozotocin-induced diabetic rats and in patients with hypercholesterolemia. Tetrahydrobiopterin supplementation has been shown to improve endothelium-dependent relaxation in normal individuals, patients with type II diabetes and in smokers. These findings from different animal models as well as in clinical trials lead to the hypothesis that tetrahydrobiopterin, or a precursor thereof, could be a new and an effective therapeutic approach for the improvement of endothelium function in pathophysiological conditions. In addition to NO, the endothelium also produces a variety of other vasoactive factors and a key question is: Is there also a link to changes in the synthesis/action of these other endothelium-derived factors to the cardiovascular complications associated with diabetes? Endothelium-derived hyperpolarizing factor, or EDHF, is thought to be an extremely important vasodilator substance notably in the resistance vasculature. Unfortunately, the nature and, indeed, the very existence of EDHF remains obscure. Potentially there are multiple EDHFs demonstrating vessel selectivity in their actions. However, until now, identity and properties of EDHF that determine the therapeutic potential of manipulating EDHF remains unknown. Here we briefly review the current status of EDHF and the link between EDHF and endothelial dysfunction associated with diabetes.

Animals↗
PubMed2004

Endothelial function: ready for prime time?

The strategic location of the endothelium allows it to detect changes in hemodynamic forces and blood-borne signals, and to respond by releasing a number of autocrine and paracrine substances. The balanced release of these bioactive factors facilitates vascular homeostasis. If disrupted, endothelial cell dysfunction ensues. This predisposes the vessel wall to vasoconstriction, leukocyte adherence, platelet activation, thrombosis, vascular inflammation and atherosclerosis. Given the central role of the endothelium in the development and progression of atherosclerosis, endothelial function testing may serve as a useful biomarker of atherosclerotic disease. The present review highlights the current modalities used in assessing endothelial function, explores how endothelial function may serve as a biomarker for atherosclerosis, comments on the prognostic relevance of endothelial function and describes its use in the clinical setting.

Biomarkers↗
PubMed2004

Rationale and design of the Glitazones and the Endothelium (GATE) study: evaluation of rosiglitazone on endothelial function in patients with diabetes.

The vascular endothelium has emerged as a critical determinant of cardiovascular health and disease, and improving endothelial function is an important target for therapy. Accumulating evidence suggests that insulin resistance in patients with diabetes and the metabolic syndrome may impair endothelial function, uncovering a proinflammatory, proatherosclerotic vascular phenotype. The rationale and design of the Glitazones and the Endothelium (GATE) study is presented. The GATE study is a randomized, double-blind study for the evaluation of the effects of rosiglitazone versus placebo on endothelial function when used as an add-on therapy in patients with diabetes currently treated with oral therapy. It is hypothesized that the peroxisome proliferator-activated receptor-gamma agonist rosiglitazone will improve endothelium-dependent vasodilation, and that this effect will be related to improvements in insulin sensitivity, with concomitant reductions in whole-body insulin resistance. Furthermore, the beneficial effects of rosiglitazone will be additive to those of existing oral therapies that may modulate endothelial function. Because endothelial dysfunction plays a pivotal role in the development and progression of atherosclerosis, the GATE study may provide the rationale and impetus for the aggressive treatment of insulin-resistant patients with glitazone therapy.

Administration, Oral↗
PubMed2003

Effects of left ventricular contractility and coronary vascular resistance on coronary dynamics.

Wave-intensity analysis, which separates upstream from downstream events and defines their interaction, has been used to study the effects of changes in left ventricular (LV) contractility (E(max)) and left circumflex coronary artery resistance (R(LCx)) on the coronary systolic flow impediment (CSFI). In 10 anesthetized, open-chest dogs, we measured coronary, aortic, and LV pressures, coronary velocity (Flowire), and flow. E(max) was increased by paired pacing and R(LCx) was modulated by intracoronary infusions of vasodilators (adenosine and nitroglycerin) and a vasoconstrictor (phenylephrine). When both E(max) and R(LCx) were varied, CSFI and the energy of the backward-going compression wave (I(W-)) were greatest at the highest levels of E(max) and the lowest levels of R(LCx). I(W-) was proportional to the CSFI. We conclude that contractility and coronary resistance change CSFI by modulating the backward-going compression wave.

Algorithms↗
PubMed2003

Catalase has negligible inhibitory effects on endothelium-dependent relaxations in mouse isolated aorta and small mesenteric artery.

1. The current study examined the hypothesis that endothelial production of hydrogen peroxide (H2O2) mediates relaxations to acetylcholine (ACh) in aorta and small mesenteric arteries (SMA) from mice. 2. Relaxations to ACh (0.01-10 microM) and H2O2 (0.1-1000 microM) were produced in aorta and SMA isolated from wild-type C57BL/6 mice and type II diabetic mice (db/db). In SMA, relaxations to ACh were produced in the presence of N omega-nitro-L-arginine methyl ester (100 microM) and indomethacin (Indo, 10 microM). 3. 1-H[1,2,4]oxadiazolo[4,3-]quinoxalin-1-one (10 microM) significantly reduced ACh-induced relaxations in SMA, abolished responses in aorta, but had no effect on relaxations induced by H2O2. Catalase (2500 U ml-1) abolished responses to H2O2, but did not alter relaxations to ACh in the SMA and only caused a small rightward shift in responses to ACh in the aorta. 4. ACh-, but not H2O2-, mediated relaxations were significantly reduced by tetraethylammonium (10 mM), the combination of apamin (1 microM) and charybdotoxin (100 nM), and 25 mm potassium chloride (KCl). Higher KCl (60 mM) abolished relaxations to both ACh and H2O2. Polyethylene glycolated superoxide dismutase (100 U ml-1), the catalase inhibitor 3-amino-1,2,4-triazole (3-AT, 50 mM) and treatment with the copper chelator diethyldithiolcarbamate (3 mM) did not affect relaxations to ACh. 5. H2O2-induced relaxations were endothelium-independent and were not affected by ethylene diamine tetraacetic acid (EDTA 0.067 mM), 4-aminopyridine (1 mM), ouabain (100 microM) and barium (30 microM), 3-AT or Indo. 6. Although the data from this study show that H2O2 dilates vessels, they do not support the notion that H2O2 mediates endothelium-dependent relaxations to ACh in either aorta or SMA from mice.

Acetylcholine↗
PubMed2003

Effect of chelation therapy on endothelial function in patients with coronary artery disease: PATCH substudy.

OBJECTIVES: The purpose of this study was to evaluate the effect of chelation therapy with ethylenediamine tetraacetic acid (EDTA) on endothelium-dependent vasomotor responses in patients with documented coronary artery disease (CAD). BACKGROUND: Oxidative stress plays an important role in the dysfunction of endothelium and development of atherosclerosis. Modification of cardiac risk factors and employment of antioxidants have been shown to improve endothelial function. Ethylenediamine tetraacetic acid chelation therapy is considered to be a complementary therapy for patients with CAD and is proposed to have antioxidant properties. METHODS: A total of 47 patients enrolled in the Program to Assess Alternative Treatment Strategies to Achieve Cardiac Health (PATCH) participated in this substudy and had complete data. High-resolution ultrasound was used to assess endothelium-dependent brachial artery flow-mediated vasodilation (FMD) in patients with CAD in a randomized, double-blind, and placebo-controlled fashion. Patients were randomized to chelation therapy or placebo. The primary end point was the absolute difference in FMD after the first and 33rd treatments (6 months) of study groups compared with their baselines. RESULTS: At the baseline, the study population had mild impairment of FMD (7.2 +/- 3.4%). The first chelation treatment did not change FMD as compared with placebo (chelation 6.5 +/- 3.5% vs. placebo 7.4 +/- 2.9%; p value = 0.371). The brachial artery studies at six months did not demonstrate significant differences in FMD between study groups (placebo 7.3 +/- 3.4% vs. chelation 7.3 +/- 3.2%; p value = 0.961). CONCLUSIONS: Our results suggest that EDTA chelation therapy in combination with vitamins and minerals does not provide additional benefits on abnormal vasomotor responses in patients with CAD optimally treated with proven therapies for atherosclerotic risk factors.

Aged↗
PubMed2003

Nitric oxide, atherosclerosis and the clinical relevance of endothelial dysfunction.

The endothelium plays a key role in vascular homeostasis through the release of a variety of autocrine and paracrine substances, the best characterized being nitric oxide. A healthy endothelium acts to prevent atherosclerosis development and its complications through a complex and favorable effect on vasomotion, platelet and leukocyte adhesion and plaque stabilization. The assessment of endothelial function in humans has generally involved the description of vasomotor responses, but more widely includes physiological, biochemical and genetic markers that characterize the interaction of the endothelium with platelets, leukocytes and the coagulation system. Stable markers of inflammation such as high sensitivity C-reactive protein are indirect and potentially useful measures of endothelial function for example. Attenuation of the effect of nitric oxide accounts for the majority of what is described as endothelial dysfunction. This occurs in response to atherosclerosis or its risk factors. Much remains to be learned about the molecular and genetic pathophysiological mechanisms of endothelial cell abnormalities. However, pharmacological intervention with a growing list of medications can favorably modify endothelial function, paralleling beneficial effects on cardiovascular morbidity and mortality. In addition, several small studies have provided tantalizing evidence that measures of endothelial health might provide prognostic information about an individual patient's risk of subsequent events. As such, the sum of this evidence makes the clinical assessment of endothelial function an attractive surrogate marker of atherosclerosis disease activity. The review will focus on the role of nitric oxide in atherosclerosis and the clinical relevance of these findings.

C-Reactive Protein↗
PubMed2003

Working heart function in diabetes is not improved by spironolactone treatment.

Aldosterone antagonism has emerged as an important strategy for end-stage congestive heart failure. To evaluate the potential contribution of aldosterone towards the cardiac complications of diabetes, this study examined the effects of chronic aldosterone receptor blockade (with spironolactone) on isolated working heart function in streptozotocin (STZ) - induced diabetic rats. Wistar rats were divided into four groups: control, control spironolactone-treated, diabetic, and diabetic spironolactone-treated. Following chronic spironolactone treatment (8 weeks), cardiac function was assessed in terms of the rate of contraction (+dP/dT), rate of relaxation (-dP/dT), and left ventricular developed pressure (LVDP). Untreated diabetic rats exhibited marked cardiac dysfunction when compared with age matched controls (p < 0.001). Long-term spironolactone treatment did not improve these parameters. These data demonstrate the lack of beneficial effects of aldosterone receptor blockade on isolated working heart function in diabetes.

Animals↗
PubMed2003

The endothelium in health and disease--a target for therapeutic intervention.

In this review we discuss the contribution of NO, prostacyclin and endothelium-derived relaxing factor--endothelium-derived hyperpolarizing factor, or EDHF, to vascular function. We also explore the hypotheses (1): that tissues can store NO as nitrosothiols (RSNOs) and (2) that such RSNO stores can be modulated by physiological and pathophysiological processes. Notably in the microcirculation, EDHF appears to play an important role in the regulation of vascular tone. Leading candidates for EDHF include extracellular potassium (K+), an epoxygenase product, hydrogen peroxide and/or a contribution from myoendothelial gap junctions. Data from our laboratory indicate that in mouse vessels, different endothelium-dependent vasodilators, such as acetylcholine and protease-activated receptor (PAR) agonists, release different endothelium-derived relaxing factors. The combination of two K-channel toxins, apamin and charybdotoxin, inhibits EDHF activity in most protocols. Endothelial dysfunction is considered as the major risk factor and a very early indicator of cardiovascular disease including the cardiovascular complications of type I & types II diabetes. Impaired endothelium-dependent vasodilatation results primarily from a decreased synthesis of endothelium-derived nitric oxide (NO) and/or an increase in the production of reactive oxygen species such as superoxide. We have shown that the administration of tetrahydrobiopterin, an important co-factor for nitric oxide synthase (NOS) partially restores endothelial function (1) in leptin-deficient mice (db/db) with spontaneous type II diabetes, as well as (2) in human vascular tissue harvested for coronary artery bypass grafting (CABG). These data suggest that a deficiency in the availability of tetrahydrobiopterin plays an important role in vascular dysfunction associated with Type II diabetes. In addition, changes in the contribution of EDHF occur in vascular tissue from the db/db mice suggesting a compensatory increase in EDHF production; whether this alteration in EDHF production is physiological or pathophysiological remains controversial.

Animals↗
PubMed2003

The fate of endothelial function testing: rationale and design of the Firefighters And Their Endothelium (FATE) study.

Endothelial dysfunction plays a pivotal role in the development and progression of atherosclerotic vascular disease. The endothelium is strategically located between blood and vascular smooth muscle, making it both vulnerable to a variety of injurious stimuli but also available for interrogation as a marker of vascular health. Firefighters And Their Endothelium (FATE) is a prospective, longitudinal cohort study designed to assess the relationship between endothelial function, emerging cardiovascular risk factors and ultimately atherosclerotic vascular disease. It is hypothesized that participants with impaired endothelial function will be at increased risk of atherosclerotic complications. This Canadian initiative will recruit 1600 middle-aged participants with no known history of cardiovascular disease to be followed for cardiovascular events over the next decade. Quantitative B-mode ultrasound will be employed to assess endothelial function and subclinical atherosclerosis. This research is designed to redefine the approach to the primary prevention of atherosclerosis.

Adult↗
PubMed2002

Abciximab attenuates coronary microvascular endothelial dysfunction after coronary stenting.

BACKGROUND: Platelet glycoprotein IIb/IIIa receptor blockade with abciximab decreases ischemic events after percutaneous coronary intervention (PCI); however, the mechanism of this benefit has not been fully elucidated. The present study was designed to assess endothelium-dependent vasomotion after coronary stenting and to determine if abciximab alters this response. METHODS AND RESULTS: The study group consisted of 48 patients (59+/-10 years of age) with discrete coronary stenoses who underwent stenting alone (n=28) or stenting plus abciximab (n=20). A control group consisted of 31 additional patients who had vasomotor testing on a non-PCI vessel. Coronary blood flow (CBF) was measured (0.014-inch Doppler wire) 30 minutes after uncomplicated PCI and in response to the intracoronary infusion of acetylcholine (Ach) (10(-7), 10(-6) mol/L Ach) and adenosine (24 microg). Ach-mediated increase in CBF was impaired after stent insertion when compared with the control group (41+/-52% versus 70+/-48%; P<0.05). The stenting plus abciximab group demonstrated a superior CBF response to Ach compared with the stenting alone group (83+/-93% versus 41+/-52%; P<0.05), with no difference between groups in the peak flow or percent change in flow to adenosine. By multivariate analysis, concomitant administration of abciximab was strongly predictive of the change in CBF to Ach (P<0.005). CONCLUSIONS: Abciximab preserves the CBF response to Ach after coronary stenting. The preservation of microvascular endothelial function may help explain the beneficial clinical effect of this agent in patients undergoing PCI.

Abciximab↗
PubMed2002

Guidelines for the ultrasound assessment of endothelial-dependent flow-mediated vasodilation of the brachial artery: a report of the International Brachial Artery Reactivity Task Force.

Endothelial function is thought to be an important factor in the pathogenesis of atherosclerosis, hypertension and heart failure. In the 1990s, high-frequency ultrasonographic imaging of the brachial artery to assess endothelium-dependent flow-mediated vasodilation (FMD) was developed. The technique provokes the release of nitric oxide, resulting in vasodilation that can be quantitated as an index of vasomotor function. The noninvasive nature of the technique allows repeated measurements over time to study the effectiveness of various interventions that may affect vascular health. However, despite its widespread use, there are technical and interpretive limitations of this technique. State-of-the-art information is presented and insights are provided into the strengths and limitations of high-resolution ultrasonography of the brachial artery to evaluate vasomotor function, with guidelines for its research application in the study of endothelial physiology.

Brachial Artery↗