Optimal strategy for administering enoxaparin to patients undergoing coronary angiography without angioplasty for acute coronary syndromes

The optimal strategy for administration of low molecular weight heparin in patients with acute coronary syndrome (ACS) undergoing coronary angiography without percutaneous coronary intervention remains unclear. We studied postangiographic vascular complications in 325 consecutive patients (210 men and 115 women, mean age 63 years) with ACS undergoing diagnostic coronary angiography via a femoral approach followed by immediate sheath removal. At the time of angiography, 44 patients were on intravenous unfractionated heparin (UFH), 229 on subcutaneous enoxaparin, and 52 on no heparin. Enoxaparin was withheld on the morning of angiography in 181 of 229 patients: the no A.M. dose group. Vascular complications were audited, including hematoma development at angiographic puncture sites; these complications were considered significant if >25 cm(2). Major vascular complications requiring transfusion or surgical interventions were infrequent in all groups. Patients receiving enoxaparin on the morning of angiography had a twofold increase in significant hematoma rate compared with the no A.M. dose group (31% vs 16%; p = 0.015). The no A.M. dose group had hematoma rates similar to UFH (20%; p = NS) and no anticoagulation (13.5%; p = NS). No significant increase in ischemic episodes occurred as a result of withholding enoxaparin in the no A.M. dose group. We conclude that omission of enoxaparin on the morning of cardiac catheterization results in vascular complications rates comparable to that of UFH without precipitating rebound ischemia. This is a practical, safe strategy for patients with ACS undergoing coronary angiography, allowing early mobilization for most patients who do not proceed to immediate percutaneous coronary intervention.

Predictors of bacterial meningitis in the era after Haemophilus influenzae

OBJECTIVE

To determine if, in the era after Haemophilus influenzae type b, the cerebrospinal fluid (CSF) white blood cell (WBC) count can be safely used to stratify children suspected of having bacterial meningitis into low- and high-risk groups.

DESIGN

Retrospective analysis of CSF samples.

SETTING

Tertiary care pediatric center in Toronto, Ontario, between January 1, 1992, and October 1, 1996.

PATIENTS

All CSF samples collected on children aged 2 months to 17 years were included. The final database consisted of 1617 atraumatic samples from children without prior neurologic or immunologic disease who underwent a lumbar puncture to assess the possibility of community-acquired bacterial meningitis.

MAIN OUTCOME MEASURES

The predictive values of CSF WBC count, differential, protein, and glucose.

RESULTS

There were 44 cases of bacterial meningitis. Five had 3 CSF WBCs per microliter or less, and 6 had 4 to 30 CSF WBCs per microliter. The negative predictive value of CSF specimens with 30 WBCs per microliter or less for bacterial meningitis was 99.3%. Cerebrospinal fluid samples with greater than 30 WBCs per microliter had a likelihood ratio for bacterial meningitis of 10.3 (95% confidence interval, 8.0-13.1) and a positive predictive value of 22.3%. Other significant predictors of bacterial meningitis included age, CSF glucose, protein, gram stain, CSF-serum glucose ratio, and peripheral blood band count.

CONCLUSIONS

Given the occurrence of bacterial meningitis in children in the absence of CSF pleocytosis, other factors should be considered when managing children with suspected bacterial meningitis. Children older than 6 months with 30 CSF WBCs per microliter or less are at low risk for bacterial meningitis. If clinically stable and without other laboratory markers of bacterial meningitis, hospital admission and empiric antibiotic therapy may be unwarranted.

BACE knockout mice are healthy despite lacking the primary beta-secretase activity in brain: implications for Alzheimer's disease therapeutics

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by accumulation of amyloid plaques and neurofibrillary tangles in the brain. The major components of plaque, beta-amyloid peptides (Abetas), are produced from amyloid precursor protein (APP) by the activity of beta- and gamma-secretases. beta-secretase activity cleaves APP to define the N-terminus of the Abeta1-x peptides and, therefore, has been a long- sought therapeutic target for treatment of AD. The gene encoding a beta-secretase for beta-site APP cleaving enzyme (BACE) was identified recently. However, it was not known whether BACE was the primary beta-secretase in mammalian brain nor whether inhibition of beta-secretase might have effects in mammals that would preclude its utility as a therapeutic target. In the work described herein, we generated two lines of BACE knockout mice and characterized them for pathology, beta-secretase activity and Abeta production. These mice appeared to develop normally and showed no consistent phenotypic differences from their wild-type littermates, including overall normal tissue morphology and brain histochemistry, normal blood and urine chemistries, normal blood-cell composition, and no overt behavioral and neuromuscular effects. Brain and primary cortical cultures from BACE knockout mice showed no detectable beta-secretase activity, and primary cortical cultures from BACE knockout mice produced much less Abeta from APP. The findings that BACE is the primary beta-secretase activity in brain and that loss of beta-secretase activity produces no profound phenotypic defects with a concomitant reduction in beta-amyloid peptide clearly indicate that BACE is an excellent therapeutic target for treatment of AD.

Therapeutic angiogenesis for ischemic cardiovascular disease

In animal models of ischemia, a large body of evidence indicates that administration of angiogenic growth factors, either as recombinant protein or by gene transfer, can augment nutrient perfusion through neovascularization. While many cytokines have angiogenic activity, the best studied both in animal models and clinical trials are vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF). Clinical trials of therapeutic angiogenesis in patients with end-stage coronary artery disease have shown large increases in exercise time and marked reductions in symptoms of angina, as well as objective evidence of improved perfusion and left ventricular function. Larger scale placebo-controlled trials have been limited to intracoronary and intravenous administration of recombinant protein, and have not yet shown significant improvement in either exercise time or angina when compared to placebo. Larger scale placebo-controlled studies of gene transfer are in progress. Future clinical studies will be required to determine the optimal dose, formulation, route of administration and combinations of growth factors, as well as the requirement for endothelial progenitor cell or stem cell supplementation, to provide effective and safe therapeutic myocardial angiogenesis.

Functional gamma-secretase inhibitors reduce beta-amyloid peptide levels in brain

Converging lines of evidence implicate the beta-amyloid peptide (Ass) as causative in Alzheimer's disease. We describe a novel class of compounds that reduce A beta production by functionally inhibiting gamma-secretase, the activity responsible for the carboxy-terminal cleavage required for A beta production. These molecules are active in both 293 HEK cells and neuronal cultures, and exert their effect upon A beta production without affecting protein secretion, most notably in the secreted forms of the amyloid precursor protein (APP). Oral administration of one of these compounds, N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester, to mice transgenic for human APP(V717F) reduces brain levels of Ass in a dose-dependent manner within 3 h. These studies represent the first demonstration of a reduction of brain A beta in vivo. Development of such novel functional gamma-secretase inhibitors will enable a clinical examination of the A beta hypothesis that Ass peptide drives the neuropathology observed in Alzheimer's disease.

A learning deficit related to age and beta-amyloid plaques in a mouse model of Alzheimer's disease

Mice that overexpress the human mutant amyloid precursor protein (hAPP) show learning deficits, but the apparent lack of a relationship between these deficits and the progressive beta-amyloid plaque formation that the hAPP mice display is puzzling. In the water maze, hAPP mice are impaired before and after amyloid plaque deposition. Here we show, using a new water-maze training protocol, that PDAPP mice also exhibit a separate age-related deficit in learning a series of spatial locations. This impairment correlates with beta-amyloid plaque burden and is shown in both cross-sectional and longitudinal experimental designs. Cued navigation and object-recognition memory are normal. These findings indicate that A beta overexpression and/or A beta plaques are associated with disturbed cognitive function and, importantly, suggest that some but not all forms of learning and memory are suitable behavioural assays of the progressive cognitive deficits associated with Alzheimer's-disease-type pathologies.

Interferon-gamma and lipopolysaccharide potentiate monocyte tissue factor induction by C-reactive protein: relationship with age, sex, and hormone replacement treatment

BACKGROUND

Elevated plasma levels of C-reactive protein (CRP) in population studies and in patients with unstable coronary syndromes are predictive of future adverse events, including cardiac death and myocardial infarction, implicating inflammation in pathogenesis. Although CRP is considered a marker of inflammation, it induces monocyte tissue factor (TF) and may play a prothrombotic role in atherosclerosis and its complications.

METHODS AND RESULTS

Peripheral blood mononuclear cells (PBMCs) from 79 healthy men and women aged 26 to 83 years and 21 healthy postmenopausal women taking hormone replacement therapy (HRT) were stimulated with CRP, lipopolysaccharide (LPS), interferon-gamma (IFN), or their combination. Levels of CRP in the normal range (1 to 5 microg/mL) increased basal monocyte TF 4- to 6-fold and 40-fold at higher concentrations (25 microg/mL). Coincubation of LPS with CRP produced a greater-than-additive response. IFN did not induce TF but synergized with CRP to approximately double activity. There was a striking positive correlation between age and monocyte TF induction, with a dramatic rise on monocytes from postmenopausal women that was not apparent on cells from women taking HRT.

CONCLUSIONS

Synergy between CRP and inflammatory mediators may play a direct prothrombotic role in the pathogenesis of coronary atherosclerosis and its acute complications by increasing monocyte/macrophage TF. This may contribute to age and sex differences in coronary events and to the protective effects of HRT.

Vascular risk factors correlate to the extent as well as the severity of coronary atherosclerosis

BACKGROUND

Because most acute coronary events result from thrombosis at sites of minor plaque, the extent of non-obstructive coronary artery disease (CAD), rather than simply the number of severe stenoses, might be clinically relevant.

OBJECTIVE

To examine the relationship between vascular risk factors and a novel extent score for CAD that measures the percentage of the coronary tree involved with atheromatous plaque, as judged by coronary angiography.

METHODS

We assessed the extent and severity of CAD and the presence of vascular risk factors of 429 consecutive eligible patients (296 men, aged 61 +/- 11 years) who presented for elective coronary angiography. Detailed analyses of lipid levels were performed for 126 subjects.

RESULTS

The mean extent score was 54 (range 0-100). The presence of diabetes (P < 0.001), current or former smoking (P < 0.005) and a history of hypertension (P < 0.001) were all strongly associated with the CAD extent score, as was severity of disease. For the 283 patients with one or no severe stenosis, diabetes was associated with a greater extent score (57 versus 41%, P < 0.005), as was smoking (49 versus 34%, P < 0.005). For the 126 patients with detailed data on lipid levels, extent of coronary artery disease was independently correlated to age (P < 0.005), male sex (P < 0.05), presence of diabetes (P < 0.05), hypertension (P < 0.05), level of lipoprotein (a) (P < 0.005) and low-density:high-density lipoprotein ratio (P < 0.01) in multivariable analysis.

CONCLUSIONS

Extent of CAD, as well as its severity, is significantly associated with traditional vascular risk factors. Because most acute coronary events occur at sites of minor plaque, this might explain the mechanism whereby risk factors confer adverse prognostic significance.

Attenuation of anti-ischemic efficacy during chronic therapy with nicorandil in patients with stable angina pectoris

After 2 weeks of nicorandil therapy, time to ischemia on stress testing was significantly less than on day 1 and not different from placebo. These data are consistent with attenuation of the anti-ischemic effects of this drug and suggest that the potassium channel-opening properties do not compensate for development of attenuation to the nitrate component of nicorandil.

Synthesis and sar of 2- and 3-substituted 7-azaindoles as potential dopamine D4 ligands

7-azaindole compounds bearing a cyclic amine moiety linked by a one or two carbon chain attached at the 2- or 3-position were synthesised and evaluated as potential dopamine D4 ligands. Highest affinity and selectivity for the D4 receptor resided in the 3-aminomethyl-7-azaindole series.

Triggers of daily life ischaemia

OBJECTIVE

To determine the usual triggers of silent and symptomatic ischaemia.

DESIGN

Patients wore an ambulatory recorder for 48 hours. The device emitted a tone on detection of ischaemia and patients noted activities, feelings, and symptoms so that ischaemia could be attributed to one of four triggers: physical stress, mental stress, combined physical/mental stress, or no stressor.

SETTING

Home environment.

PATIENTS

Patients (n = 38) with stable coronary disease, positive exercise electrocardiography, and ischaemic episodes on ambulatory electrocardiography.

MAIN OUTCOME MEASURE

Matching ischaemic episodes with perceived triggers.

RESULTS

Altogether 257 ischaemic episodes (53% silent) were documented. Triggers were: physical stress, 56%; mental stress, 5%; combined physical/mental stress, 8%; no identifiable trigger, 31%. Episodes associated with mental or no stress were more often silent (69% and 75%, respectively) than those associated with physical stress (45%, p < 0.01), while combined physical/mental stress episodes were usually symptomatic (10% silent, p < 0.01 v other stressors). Although physical stress was less commonly a trigger of silent ischaemia than angina (47% v 65%, p < 0.01), it was still the predominant trigger of silent ischaemia. There was no identifiable trigger in 45% of silent and only 17% of anginal episodes (p < 0.01). Only nine silent episodes involved mental stress alone as a trigger.

CONCLUSIONS

Daily life ischaemia is usually triggered by physical activity. Mental stress alone is an uncommon trigger of either silent or symptomatic ischaemia, while combined physical/mental stress is a significant but minor trigger of angina. Patients can identify a trigger in 83% of anginal episodes, compared with only half of silent ischaemic episodes.

L-745,870, a subtype selective dopamine D4 receptor antagonist, does not exhibit a neuroleptic-like profile in rodent behavioral tests

This study examined the high-affinity, selective dopamine D4 receptor antagonist, L-745,870 (3-([4-(4-chlorophenyl)piperazin-1-yl]methyl)-1H-pyrrolo[2, 3-b]pyridine) in rodent behavioral models used to predict antipsychotic potential and side-effect liabilities in humans. In contrast to the classical neuroleptic, haloperidol, and the atypical neuroleptic, clozapine, L-745,870 failed to antagonize amphetamine-induced hyperactivity in mice or impair conditioned avoidance responding in the rat at doses selectively blocking D4 receptors. Furthermore, L-745,870 failed to reverse the deficit in prepulse inhibition of acoustic startle responding induced by the nonselective dopamine D2/3/4 receptor agonist apomorphine, an effect which was abolished in rats pretreated with the D2/3 receptor antagonist, raclopride (0.2 mg/kg s.c.). L-745,870 had no effect on apomorphine-induced stereotypy in the rat but did induce catalepsy in the mouse, albeit at a high dose of 100 mg/kg, which is likely to occupy dopamine D2 receptors in vivo. High doses also impaired motor performance; in rats L-745,870 significantly reduced spontaneous locomotor activity (minimum effective dose = 30 mg/kg) and in mice, L-745,870 reduced the time spent on a rotarod revolving at 15 rpm (minimum effective dose = 100 mg/kg). Altogether these results suggest that dopamine D4 receptor antagonism is not responsible for the ability of clozapine to attenuate amphetamine-induced hyperactivity and conditioned avoidance responding in rodents. Furthermore, the lack of effect of L-745,870 in these behavioral tests is consistent with the inability of the compound to alleviate psychotic symptoms in humans.

4-Heterocyclylpiperidines as selective high-affinity ligands at the human dopamine D4 receptor

5-(4-Chlorophenyl)-3-(1-(4-chlorobenzyl)piperidin-4-yl)pyrazole (3) was identified from screening of the Merck sample collection as a human dopamine D4 (hD4) receptor ligand with moderate affinity (61 nM) and 4-fold selectivity over human D2 (hD2) receptors. Four separate parts of the molecule have been examined systematically to explore structure-activity relationships with respect to hD4 affinity and selectivity over other dopamine receptors. It was found that the 4-chlorophenyl group attached to the pyrazole is optimal, as is the 4-substituted piperidine. The lipophilic group on the basic nitrogen is more amenable to change, with the optimal group found to be a phenethyl. The aromatic heterocyle can be altered to a number of different groups, with isoxazoles and pyrimidines showing improved affinities. This heterocycle can also be advantageously alkylated, improving the selectivity of the compounds over D2 receptors. It is hypothesized that the conformation around the bond joining the aromatic heterocycle to the piperidine is important for D4 affinity, based on crystal structures of isoxazoles (29 and 30) and on a conformationally constrained compound (28). Putting all the favorable changes together led to the discovery that 5-(4-chlorophenyl)-4-methyl-3-(1-(2-phenylethyl)piperidin-4-yl)iso xazole (36) is a nanomolar antagonist at human dopamine D4 receptors with > 500-fold selectivity over hD2 and > 200-fold selectivity over hD3. Compound 36 is an antagonist of hD4 receptors with good oral bioavailability of 38%, a half life of 2 h, and brain levels 10-fold higher than plasma levels.

Identification and pharmacological characterization of [125I]L-750,667, a novel radioligand for the dopamine D4 receptor

We identified a novel azaindole derivative, L-750,667, that has high affinity (Ki = 0.51 nM) and >2000-fold selectivity for D4 dopamine receptors compared with its activity at D2 and D3 dopamine receptors. L-750,667 had little affinity for rat D1/D5 dopamine receptors, sigma binding sites, or 5-hydroxytryptamine1A or 5-hydroxytryptamine2 receptors. In functional studies, L-750,667 exhibited high affinity antagonist activity at D4 receptors, reversing dopamine (1 microM)-induced inhibition of cAMP accumulation in human embryonic kidney (HEK) cells expressing the human D4 receptor (hD4 HEK) with an EC50 value of 80 nM. The radioiodinated form of L-750,667 bound specifically to the human dopamine D4 receptor expressed in HEK cells and saturation analysis revealed a single high affinity binding site for [125I]L-750,667 (Kd = 0.16 +/- 0.06 nM). The maximum number of binding sites (Bmax) estimated using [125I]L-750,667 in hD4 HEK cells was 251 +/- 71 fmol/mg, which correlated well with the Bmax value determined using [3H]spiperone (227 +/- 83 fmol/mg) in the same membrane preparations. The pharmacological profile of [125I]L-750,667 binding to hD4 HEK cells was evaluated using known dopamine receptor agonists and antagonists. The rank order of potencies for dopamine receptor agonists was dopamine > quinpirole > 6,7-aminodihydroxytetralin > 5,6-aminodihydroxytetralin. Dopamine receptor antagonists also showed high affinity, with a rank order of haloperidol > chlorpromazine > domperidone > (+)-butaclamol > (-)-sulpiride = (+)-sulpiride > (+)-SCH23390 > (-)-butaclamol. [125I]L-750,667, bound to D4 receptors in a stereoselective manner with (+)-butaclamol showing higher activity than its respective enantiomer (-)-butaclamol. These results show that [125I]L-750,667 is a novel, highly selective radioligand for dopamine D4 receptors and may be used to investigate the dopamine D4 receptor population in the central nervous system.

Angiographic severity of coronary narrowing is a surrogate marker for the extent of coronary atherosclerosis

Most acute coronary events occur because of narrowings at sites of angiographically minor plaque. Despite this, angiograms are reported in terms of the number of coronary arteries with severe narrowings. Disease severity is correlated with prognosis, but this may simply be due to a strong positive correlation between the severity and extent of coronary atheroma. We therefore aimed to assess the relation between the severity and the extent of coronary atherosclerosis. Coronary angiograms of 350 consecutive patients referred for elective cardiac catheterization were analyzed. Two independent observers calculated the number of arteries with > or = 70% stenosis, a disease severity score, and an extent score (percentage of the coronary artery length with any luminal irregularity). There were no obstructive stenoses in 123 patients (35%); 91 (26%) had 1-vessel disease, 81 (23%) had 2-vessel disease, and 55 (16%) had 3-vessel coronary artery disease. The median severity score was 1 (lower, upper quartile 0, 3; range 0 to 8), and the median extent score was 66% (lower, upper quartile 32, 83; range 0% to 100%). There was a strong linear relation between severity score and extent score (r = 0.62, p < 0.001); however, the data were better described by 2 intersecting straight lines, with a steeper increase in disease severity when the extent score was between 80% and 90% (F1;121 = 6.9, p = 0.001). The severity of coronary disease is therefore significantly correlated with disease extent. This may explain the observed relation between the number of arteries with obstructive stenoses and subsequent risk, even though most events occur at sites of minor plaque.

Are radioligand antagonist/agonist binding ratios in rat pancreas predictive of functional efficacy of cholecystokinin receptor agonists and antagonists?

Radioligand binding assays have been previously used to predict the relative efficacy of novel ligands. In the present study we have investigated whether for the cholecystokinin CCK-A receptors in the rat pancreas, the ratio of binding affinities for compounds for antagonist and agonist radioligands are predictive of functional activity. A number of classical cholecystokinin agonists, such as CCK-8S, caerulein, CCK-8DS, pentagastrin and CCK-4 had antagonist/agonist binding ratios of 4-fold or greater. All compounds behaved as full agonists in the stimulation of phosphatidylinositol (PI) turnover and increase in amylase secretion in rat pancreas. In contrast, compounds such as the benzodiazepine derivatives devazepide and L-365,260 had binding ratios of less than one and lacked agonist activity in either functional assay. Interestingly, the dipeptide derivative CI-988, which has been described as a selective CCK-B antagonist, was found to have an antagonist/agonist binding ratio of 1.5 for the CCK-A receptors in rat pancreas which was sufficiently high for this compound to behave as a full agonist in the amylase assay, although CI-988 did not exhibit agonist activity in the PI assay. These results suggest that the effective receptor reserve in the amylase assay is greater than that required to stimulate PI turnover, and that the selective peptoid CCK-B antagonist CI-988 has weak agonist activity at CCK-A receptors.

Correlation between post-ejection shortening and improvement in regional wall motion after revascularization in patients with coronary artery disease

This study investigates the relationship between regional post-ejection shortening and improvement in wall motion after revascularization in patients with severe regional left ventricular contractile dysfunction. Canine studies have documented the phenomenon of post-systolic shortening during acute ischemia, and this predicted recovery of contractile function when ischemia was relieved. This delayed shortening from the ischemic segment would cause regional emptying while the other normal portion of the left ventricle starts to have diastolic relaxation. This was detectable by standard phase analysis of the radionuclide ventriculogram, the abnormal region with delayed emptying being distinguished from the normal portion of left ventricle as an area with a homogeneous phase delay. Twelve patients with successful revascularization and a pre-operative study demonstrating a single homogeneous area of phase delay were identified. The area was demarcated and the regional volume-time curve constructed. The volume-time curve of the abnormal region is analogous to the myocardial segment length versus time relationship in the canine model. We quantitated the amount of delayed (post-systolic) emptying in the demarcated region as the difference between end-systole counts and post-systolic nadir counts, and this was normalised to left ventricular stroke count. After revascularization, regional ejection fraction improved from 44 +/- 10% to 62 +/- 14% (P < 0.001), representing a 47 +/- 50% improvement over baseline. The percentage improvement in regional ejection fraction correlated with post-systolic emptying (r = 0.74, P < 0.05) but not with initial regional ejection fraction. In conclusion, post-ejection shortening causes regional post-systolic emptying and this correlates with post-revascularization improvement in regional wall motion.

Electrocardiographic identification of the infarct-related artery in acute inferior myocardial infarction

Differentiation between left circumflex occlusion and right coronary occlusion in inferior acute myocardial infarction is a common clinical problem. This study investigated new electrocardiographic markers for differentiation, including T wave inversion, and individual inferior and precordial lead ST level, versus the traditional criterion of lateral ST elevation. In 95 angiographically characterised patients, ST elevation in lateral chest lead V5 or V6 had a sensitivity of 56% and specificity of 92% to predict left circumflex related acute myocardial infarction while the absence of lateral T inversion in I and AVL was even more sensitive (89%) though less specific (74%). A criterion of ST depression in V1 > 0.1 mV has a sensitivity of 61% and specificity of 84% whereas a criterion of ST level in III minus II < or = 0.1 mV has a sensitivity of 94% and specificity of 37% in predicting left circumflex related acute myocardial infarction. These criteria were then tested in another 49 patients subsequently recruited with inferior acute myocardial infarction. Useful parameters that discriminated left circumflex related acute myocardial infarction from right coronary related acute myocardial infarction include lateral ST elevation (38% vs. 7%, P < 0.05), absence of lateral T inversion (50% vs. 15%, P < 0.05), and ST depression in V1 of more than 0.1 mV (50% vs. 7%, P < 0.05). The present study revealed new electrocardiographic clues to suggest a left circumflex related inferior acute myocardial infarction other than lateral ST elevation. However, it should be noted that no single electrocardiographic variable or their combinations could identify the infarct-related artery with complete certainty.