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Biomedical subjects

D Fitzgerald

Publications and source records attributed to D Fitzgerald.

At least 37 records · Page 2Linked to original sources
PubMed2001

Amelioration of arterial properties with a perindopril-indapamide very-low-dose combination.

BACKGROUND: Epidemiological studies have shown that increased arterial stiffness and wave reflections, major determinants of systolic and pulse pressure, are associated with morbidity and mortality. Therapeutic trials based on cardiovascular mortality have recently shown that reduction of systolic blood pressure (SBP) requires normalization of both large-artery stiffness and wave reflections. AIMS: To compare the antihypertensive effects of the very-low-dose combination of perindopril (2 mg) and indapamide (0.625 mg) (one or two tablets per day) with the beta-blocking agent atenolol (50 mg; one or two tablets per day) in order to determine whether the combination decreased SBP and pulse pressure more than did atenolol, and whether this decrease occurred in relation to a reduction in arterial stiffness [aortic pulse wave velocity (PWV)] or a decrease in the intensity of, or delay in, wave reflections (augmentation index, measured by applanation tonometry) or a combination of both. MATERIAL AND METHODS: This was a double-blind randomized study in 471 individuals with essential hypertension followed for 12 months. Arterial pressure was measured in the brachial artery (mercury sphygmomanometer) and in the carotid artery (applanation tonometry). RESULTS: For the same reduction in diastolic blood pressure (DBP), the combination of perindopril and indapamide decreased brachial SBP and pulse pressure significantly more than did atenolol (adjusted differences between groups -6.2 +/- 1.5 and -5.5 +/- 1.0 mmHg, respectively; P < 0.001). This difference was even more pronounced for the carotid than for the brachial artery. Whereas both antihypertensive agents similarly decreased PWV, only the combination significantly attenuated wave reflections. CONCLUSION: Normalization of SBP, pulse pressure and arterial function--a haemodynamic profile known to improve survival significantly in hypertensive populations at high cardiovascular risk--was achieved to a greater extent with a very-low-dose combination of perindopril and indapamide than with atenolol.

Antihypertensive Agents↗
PubMed2000

Acute psychological stress decreases plasma tissue plasminogen activator (tPA) and tissue plasminogen activator/plasminogen activator inhibitor-1 (tPA/PAI-1) complexes in cardiac patients.

Tissue plasminogen activator (tPA) promotes fibrinolysis, and impaired fibrinolysis is associated with atherosclerosis and thrombosis. Plasminogen activator inhibitor-1 (PAI-1) inhibits t-PA expression. The effects of acute laboratory stressors on tPA and tPA/PAI-1 complexes were assessed in a sample of 11 cardiac patients. Participants were randomly assigned to either a stress or relaxation condition at time 1, and the alternative condition at time 2. Blood samples were taken before (pre) and after (post) each session and participants completed a battery of psychological questionnaires. Two-way repeated-measures analysis of variance revealed a statistically significant decrease in tPA (P = 0.01) and tPA-PAI-1 complexes (P = 0.04) during the mental stress condition. Anger-in had a strong relationship to decreases in tPA/PAI-1 levels in the stress condition (r = 0.68, P < 0.05). Relaxation had no significant effect on tPA and tPA/PAI-1 levels. These data suggest that decreased fibrinolysis mediates the relationship between mental stress and atherosclerosis.

Coronary Disease↗
PubMed2000

Metal complexes of salicylhydroxamic acid (H2Sha), anthranilic hydroxamic acid and benzohydroxamic acid. Crystal and molecular structure of [Cu(phen)2(Cl)]Cl x H2Sha, a model for a peroxidase-inhibitor complex.

Stability constants of iron(III), copper(II), nickel(II) and zinc(II) complexes of salicylhydroxamic acid (H2Sha), anthranilic hydroxamic acid (HAha) and benzohydroxamic acid (HBha) have been determined at 25.0 degrees C, I=0.2 mol dm(-3) KCl in aqueous solution. The complex stability order, iron(III) >> copper(II) > nickel(II) approximately = zinc(II) was observed whilst complexes of H2Sha were found to be more stable than those of the other two ligands. In the preparation of ternary metal ion complexes of these ligands and 1,10-phenanthroline (phen) the crystalline complex [Cu(phen)2(Cl)]Cl x H2Sha was obtained and its crystal structure determined. This complex is a model for hydroxamate-peroxidase inhibitor interactions.

Copper↗
PubMed2000

Argatroban and alteplase in patients with acute myocardial infarction: the ARGAMI Study.

ARGAMI was designed to assess safety and efficacy of argatroban compared with heparin as adjunctive treatment to alteplase in the treatment of patients with acute myocardial infarction. ARGAMI consisted of an open-dose finding study (35 patients) followed by a placebo-controlled study with double dummy technique and 2:1 (argatroban:heparin) randomization. An argatroban dosage of 100 microg/kg bolus plus 3 microg/kg/min infusion for 72 hours was selected for the randomized study in which 82 patients were allocated to argatroban and 45 to heparin (5000 U intravenous bolus, 1000 U/h infusion). Patency of the infarct-related artery (Thrombolysis in Myocardial Infarction [TIMI] grade 2 or 3 flow) after 90 minutes was obtained in 62 patients (76%) allocated to argatroban versus 37 patients (82%) allocated to heparin (p=ns). Angiograms after 24 hours and 5 to 10 days showed low reocclusion rates in both groups. Bleeding complications were observed in 16 patients allocated to argatroban (19.5%) and in 9 patients allocated to heparin (20.0%). One patient allocated to heparin suffered from hemorrhage stroke. Argatroban, given as adjunctive treatment to alteplase, is tolerated well in patients with acute myocardial infarction. Safety and efficacy of the combination alteplase and argatroban (with this dose regimen) are similar to those of alteplase and heparin.

Aged↗
PubMed2000

Design of the blockade of the glycoprotein IIb/IIIa receptor to avoid vascular occlusion (BRAVO) trial.

BACKGROUND: Platelets play a key role in the pathogenesis of atherosclerosis, thrombosis, and acute coronary and cerebrovascular syndromes. Inhibition of platelet function by acetylsalicylic acid (aspirin) has been shown to reduce the incidence atherothrombotic events in patients with coronary, cerebrovascular, or peripheral vascular disease. Thienopyridine agents, however, including ticlopidine and clopidogrel, inhibit the adenosine diphosphate receptor and have modestly superior effects compared with aspirin on reduction of death, myocardial infarction, and stroke among a broad group of patients with vascular disease. More effective antithrombotic agents are still required to treat patients at high risk for recurrent vascular events. METHODS: Lotrafiban, a selective, nonpeptide antagonist of the human platelet fibrinogen receptor (glycoprotein [GP] IIb/IIIa [alphaIIb/beta3 integrin]), blocks the binding of fibrinogen to the GP IIb/IIIa receptor, which is the final common pathway of platelet aggregation. Lotrafiban at doses of up to 50 mg twice daily was well-tolerated in a 12-week, double-blind, placebo-controlled, dose-ranging study in patients with recent myocardial infarction, unstable angina, transient ischemic attack, or stroke when added to aspirin therapy. On the basis of these results, a dosing regimen was selected for the phase III Blockage of the Glycoprotein IIb/IIIa Receptor to Avoid Vascular Occlusion (BRAVO) trial based on pharmacodynamics and drug tolerability. In the pivotal BRAVO study, lotrafiban therapy is being evaluated in patients who have had a recent myocardial infarction, unstable angina, transient ischemic attack, or ischemic stroke, or who present at any time after a diagnosis of peripheral vascular disease combined with either cardiovascular or cerebrovascular disease. RESULTS: The efficacy evaluation will be based on a composite end point of clinical events (death by any cause, myocardial infarction, stroke, recurrent ischemia requiring hospitalization, or urgent ischemia-driven revascularization). The target enrollment is 9200 patients worldwide. Approximately 700 centers will participate and will be distributed within 30 countries across North America, Europe, Australia, and Asia.

Administration, Oral↗
PubMed2000

Comparison of antihypertensive and metabolic effects of losartan and losartan in combination with hydrochlorothiazide--a randomized controlled trial.

INTRODUCTION: Losartan is an angiotensin II receptor blocker indicated for treatment of hypertension. It also inhibits platelet agreggation through blockade of thromboxane A2/ prostaglandin H2 receptors, and has a uricosuric effect We determined the effect on ambulatory blood pressure (ABP) of 100 mg losartan monotherapy (L100) versus 50 mg losartan/12.5 mg hydrochlorothiazide (HCTZ) combination therapy (L50H12.5C), in patients uncontrolled on 50 mg losartan. We also assessed the effects of losartan on platelet aggregation and serum urate at these clinically relevant doses. METHODS: This was a randomized, double-blind trial of L100 versus L50H12.5C, in moderate hypertensives (sitting diastolic blood pressure (DBP) >or = 95 mmHg and < 120 mmHg). After 4 weeks of placebo run-in, patients received 50 mg losartan for 6 weeks; patients uncontrolled (sitting DBP > or = 95 mmHg) were randomized to L100 or L50H12.5C for a further 6 weeks. Platelet function was assessed by measuring percentage inhibition of platelet aggregation, and serum uric acid was also measured. RESULTS: Monotherapy with 50 mg losartan reduced ABP by 16.0/9.9 mmHg during the day and 9.8/5.5 mmHg at night However, 16 out of 24 (66%) patients had uncontrolled blood pressure on this treatment L50H12.5C further reduced daytime ABP by 10.7(10.7)/8.4(6.5) mmHg mean (SEM) compared with L100 (-5.3(9.7)/-2.3(4.8), P = 0.013). 50 mg losartan and L100 did not affect platelet function or uric acid levels beyond placebo values; treatment with L50H12.5C was associated with a significant rise in serum urate above levels obtained on 50 mg losartan (366.9(67.6) versus 331.6(65.0), P=0.006), to levels similar to placebo (358.8(80.9)). CONCLUSION: L50H12.5C is an effective antihypertensive regimen in patients with moderate hypertension that is uncontrolled on 50 mg losartan monotherapy, and is the preferred treatment option in these patients compared with increasing the dose of losartan. The additional benefit of losartan on platelet inhibition was not evident in our population at these doses; however, there was evidence to suggest that the uricosuric effects of losartan might ameliorate the uric acid retention effects of therapy with hydrochlorothiazide.

Antihypertensive Agents↗
PubMed2000

ICD waveform optimization: a randomized, prospective, pair-sampled multicenter study.

The theoretical tissue model-based estimates of phase 1 and phase 2 duration of biphasic waveforms are considerably shorter than the pulse widths currently used in ICDs with standard tilt. This study used a tissue resistance/capacitance (RC) model to identify optimal biphasic pulse widths. By paired step-down defibrillation threshold (DFT) testing, the efficacy of standard versus "tuned" biphasic waveforms was evaluated in 91 patients. Standard waveforms consisted of a phase 1 set to 65% tilt and phase 2 = phase 1. The tuned waveform was based on an RC model of membrane characteristics with a time constant of 3.5 ms. The optimal phase 1 truncation point is at the peak of membrane response. The optimal phase 2 duration ends with a membrane response near or just below 0. In paired analysis, no significant differences were found in DFT or impedance between standard and tuned waveforms. In patients with DFTs > 400 V, the tuned waveform lowered the DFT by an average of 38 V (P < 0.05). Multivariate analyses showed a significant inverse relationship between DFT and impedance (P < 0.001). As impedance increased, the tuned waveform was associated with DFTs comparable to the standard waveform with shorter pulse duration and lower delivered energy. No single tilt value allowing an easy calculation of delivered energy was related to ICD waveform efficacy. The use of ICDs with tuned optimal pulse durations offer a greater flexibility of choice for patients with high DFTs.

Aged↗
PubMed2000

Acronymophilia: an update.

The history, epidemiology, clinical features, and treatment of the epidemic infection, acronymophilia, a sinister scourge of modern medicine are described.

Abbreviations as Topic↗
PubMed1999

Optimization of an enzyme immunoassay for 11-dehydro-thromboxane B(2) in urine: comparison with GC-MS.

The urinary excretion of stable metabolites of thromboxane A2, such as 11-dehydro-thromboxane B2, reflects platelet activity in vivo. Efficient sample purification is required before analysis of thromboxane metabolites, due to the presence of large amounts of interfering material in urine. Analysis by gas chromatography-mass spectrometry after extensive sample work-up procedures provides the most reliable data, but detection by enzyme immunoassay may be reliable if sample cleanup is adequate. We describe an improved immunoassay procedure for 11-dehydro-thromboxane B2, which is based on a simple one-step solid phase extraction, by using Bond-Elut Certify II columns, followed by enzyme immunoassay by using commercially available reagents. 11-Dehydro-thromboxane B2 exists in two forms, with different chemical and immunological characteristics, which are in pH-dependent equilibrium. We kept 11-dehydrothromboxane B2 in its open ring form throughout the assay, by incubating and handling samples at pH 8.6. The extraction step achieved a recovery of 83% (95% confidence interval 74-92%), the sensitivity of the enzyme immunoassay was doubled, and the reproducibility of the assay improved under these conditions. Intra- and interassay coefficients of variation were 3 and 13.8%, respectively. A single 500-mg dose of aspirin reduced the excretion of 11-dehydro-thromboxane B2 by 77+/-14%, suggesting good specificity. Comparison with gas chromatography-mass spectrometry in 28 urine samples showed excellent agreement between the two methods (r2 = 0.94; p<0.0001), and a regression line with a slope close to 1.0. The presently modified enzyme immunoassay for 11-dehydro-thromboxane B2 is suitable for clinical studies evaluating platelet function in vivo and has the advantage of being simpler and less expensive to use than gas chromatography-mass spectrometry.

Aspirin↗
PubMed1999

Quantifying GPIIb/IIIa receptor binding using 2 monoclonal antibodies: discriminating abciximab and small molecular weight antagonists.

BACKGROUND: Dosing of glycoprotein (GP) IIb/IIIa receptor antagonists is frequently based on the inhibition of platelet aggregation, which may be influenced by the agonist used or concurrent medications. Here we describe a monoclonal antibody-based technique to quantify total and ligand-occupied GPIIb/IIIa receptors. METHODS AND RESULTS: In vitro binding of monoclonal antibodies, LYP18 (Mab1) and 4F8 (Mab2), to the GPIIb/IIIa complex, was characterized using purified receptor and to platelets by flow cytometry. Patients undergoing coronary angioplasty received a single 20 mg dose of the oral GPIIb/IIIa antagonist, xemilofiban, or matching placebo, and antibody binding was compared with inhibition of platelet aggregation. Mab1 and Mab2 were bound to purified GPIIb/IIIa and to unoccupied, inactivated receptor on platelets. Mab2 identified the beta3 subunit, whereas Mab1 was complex-specific. Neither antibody interfered with the other's binding, suggesting that they identified distinct sites. Mab1 identified 53 300+/-5423 GPIIb/IIIa sites per platelet, whereas Mab2 identified 50 120+/-5066 sites per platelet. Mab1 binding was inhibited by abciximab in a dose dependent manner (IC50, 0.85+/-0.1 microg/mL), whereas Mab2 binding was unaffected. In contrast, the 2 small molecular weight antagonists, SC-57101A (IC50, 0.22+/-0.06 micromol/L) and eptifibatide (IC50, 0.35+/-0.14 micromol/L) inhibited Mab2 but not Mab1 binding. In patients treated with xemilofiban, Mab1 binding was unaltered but Mab2 binding decreased from 37 930+/-2061 sites per platelet at baseline to 8318+/-870 sites per platelet 6 hours after dosing (P<0.0001). Platelet aggregation to adenosine diphosphate (20 micromol/L) fell to 3+/-3% of baseline in line with the inhibition of Mab2 binding (correlation coefficient 0.8, P<0.0001). CONCLUSIONS: Mab1 and Mab2 bind to GPIIb/IIIa and are differentially displaced by abciximab and small molecular weight antagonists. These antibodies may be used to monitor receptor number and occupancy during administration of a GPIIb/IIIa antagonist.

Abciximab↗
PubMed1999

Quality of care for Medicare patients hospitalized with heart failure in rural Georgia.

BACKGROUND: It is not known whether quality of care for congestive heart failure (CHF) at rural hospitals is similar to that in larger, urban hospitals. METHODS: We reviewed hospital charts for 310 Medicare patients hospitalized with CHF at six hospitals in rural Georgia. RESULTS: Of the 310 patients, 101 (33%) had left ventricular systolic dysfunction, and 60 (19%) had preserved systolic function. Information on left ventricular function was not available for 48% (range, 29% to 87% across the six hospitals). Among patients with systolic dysfunction, 77% were prescribed an angiotensin converting enzyme (ACE) inhibitor at discharge, and 73% were prescribed digoxin. However, the mean daily ACE inhibitor dose was only 48% of the recommended target dose. Only 30% of all patients with atrial fibrillation were prescribed warfarin. CONCLUSIONS: Overall quality of care for CHF at rural hospitals appears similar to that in other settings, though many patients may not receive evaluation of ventricular function.

Aged↗
PubMed1998

Comparison of left ventricular function during interval versus steady-state exercise training in patients with chronic congestive heart failure.

This study sought to assess the safety of interval exercise training in patients with chronic congestive heart failure (CHF) with respect to left ventricular (LV) function. For effective rehabilitation in CHF, both aerobic capacity and muscle strength need to be improved. We have previously demonstrated in both coronary artery bypass surgery and patients with CHF that interval exercise training (IET) offers advantages over steady-state exercise training (SSET). However, because LV function during IET has not yet been studied, the safety of this method in CHF remains unclear. To assess LV function during IET and SSET, at the same average power output, 11 patients with stable CHF were compared with 9 stable coronary patients with minimal LV dysfunction (control group). Using first-pass radionuclide ventriculography, changes in LV function were assessed during work versus recovery phases, at temporally matched times between the fifth and sixteenth minute of IET and SSET. In CHF during IET, there were no significant variations in the parameters measured during work and/or recovery phases. During the course of both IET and SSET, there was a significant increase in LV ejection fraction (5 vs 4 U; p <0.05 each), accompanied by increased heart rate (6 vs 8 beats/min; p <0.05 each) and cardiac output (2.4 vs 1.8 L/min; p <0.01 and p <0.05). In CHF, the magnitude of change in LV ejection fraction during IET was similar to that seen in controls. Both LV ejection fraction and the clinical status in patients with CHF remained stable during IET. Because IET appears to be as safe as SSET with respect to LV function, IET can be recommended for exercise training in CHF to apply higher peripheral exercise stimuli and with no greater LV stress than during SSET.

Exercise Therapy↗
PubMed1998

A sequence within the cytoplasmic tail of GpIIb independently activates platelet aggregation and thromboxane synthesis.

All integrin alpha subunits contain a highly conserved KXGFFKR motif in their cytoplasmic domains that plays a crucial role in the regulation of integrin affinity for their ligands. We show that a lipid-modified peptide corresponding to the cytoplasmic region, 989-995, of the platelet integrin subunit glycoprotein GpIIb (alphaIIb), palmitoyl-KVGFFKR (Ppep; 10 microM), but not a similarly modified scrambled peptide (palmitoyl-FKFVRGK), can specifically induce platelet activation and aggregation equivalent to that of strong agonists such as thrombin. Ppep-induced aggregation is also associated with indices of platelet activation including thromboxane A2 (TXA2) synthesis (EC50 = 45 +/- 5 microM), secretion of alpha-granules detected as enhanced surface expression of P-selectin (EC50 = 52 +/- 8 microM), and conformational changes in GpIIb/IIIa measured by the monoclonal antibody, PAC-1 (EC50 = 3.7 +/- 1 microM). The TXA2 receptor antagonist, SQ29548, PGE1, and the ADP scavenger, apyrase, differentially inhibit the aggregation response and TXA2 synthesis in response to Ppep. Similarly, GpIIb/IIIa antagonists (RO-449883 and integrelin), which inhibit aggregation by greater than 90%, have little effect on peptide-induced TXA2 synthesis, suggesting that this event is independent of fibrinogen binding to GpIIb/IIIa. Alanine-stepping of the Ppep sequence identifies GFFK(991-994) as the critical residues in all peptide-mediated events. We conclude that this peptide can imitate the cytoplasmic domain of GpIIb and initiate parallel but independent signaling pathways, one leading to ligand binding and platelet aggregation and the other to intracellular signaling events such as TXA2 synthesis and secretion.

Acetates↗