Stability Analysis of a Stochastic Model for Prey-Predator System with Disease in the Prey

In this paper we consider a prey-predator system where the prey population is infected by a microparasite. Local as well as global stability properties of the interior equilibrium point are discussed. The stochastic stability properties of the model are investigated, suggesting that the deterministic model is robust with respect to stochastic perturbations.

Cardiac risk in noncardiac surgery

Preoperative risk assessment plays an important role in reducing perioperative morbidity and mortality in patients undergoing noncardiac surgery. In general, evaluation should reflect the circumstances of the consultation and the nature of the surgical illness. If emergent surgery is indicated, it may not allow further cardiac assessment or treatment. Perioperative medical management, surveillance and postoperative risk stratification is appropriate in these cases and may be instrumental to improving long-term outcomes. Successful perioperative evaluation is best achieved with an integrated multidisciplinary approach and good communication between the patient, primary care physician, anesthesiologist, consultant, and surgeon. A thorough history and physical examination is the most important component of a comprehensive preoperative evaluation. In general, indications for further cardiac testing and treatments are similar to those in the nonoperative setting. Coronary revascularization before noncardiac surgery is indicated in only a small subgroup of patients at very high cardiac risk. Finally, the goal of appropriate preoperative evaluation and therapy should be to not only improve immediate periprocedural outcomes but should also be geared towards improved long term clinical outcome.

Platelet glycoprotein IIb/IIIa inhibition in acute coronary syndromes. Gradient of benefit related to the revascularization strategy

AIMS

To assess the efficacy of platelet glycoprotein IIb/IIIa inhibitors in patients with acute coronary syndromes primarily medically managed.

METHODS AND RESULTS

We performed a meta-analysis of the randomized clinical trials of platelet glycoprotein IIb/IIIa inhibitor therapy in the medical management of non-ST-elevation acute coronary syndromes. Among 29570 patients, IIb/IIIa integrin blockade was associated with a reduction in death or non-fatal myocardial infarction at 30 days, from 11.5% to 10.7% (odds ratio 0.91,P =0.02). Patients undergoing percutaneous coronary intervention during index hospitalization sustained a greater reduction in ischaemic events (odds ratio 0.82, P=0.01) than patients medically managed (odds ratio 0.95, P=0.27). Among patients undergoing intervention, the benefit was more pronounced if the procedure was performed during glycoprotein IIb/IIIa inhibitor infusion (odds ratio 0.74; P=0.02), than if revascularization was performed after drug discontinuation (odds ratio 0.87,P =0.17).

CONCLUSION

This analysis, including the entire large-scale trial experience of intravenous glycoprotein IIb/IIIa inhibitors in patients with acute coronary syndromes primarily medically managed, demonstrates an overall significant, albeit moderate, reduction in 30-day death or myocardial infarction associated with therapy. Although not based on a prospectively defined hypothesis, the findings suggest a gradient of benefit conferred by these agents depending on the revascularization strategy used.

Platelet glycoprotein IIb/IIIa inhibitors reduce mortality in diabetic patients with non-ST-segment-elevation acute coronary syndromes

BACKGROUND

Diabetes mellitus is a major risk factor for adverse outcomes after acute coronary syndromes (ACS). Because this disease may be associated with increased platelet aggregation, we investigated whether diabetic patients with ACS derive particular benefit from platelet glycoprotein (GP) IIb/IIIa receptor inhibition.

METHODS AND RESULTS

We performed a meta-analysis of the diabetic populations enrolled in the 6 large-scale platelet GP IIb/IIIa inhibitor ACS trials: PRISM, PRISM-PLUS, PARAGON A, PARAGON B, PURSUIT, and GUSTO IV. Among 6458 diabetic patients, platelet GP IIb/IIIa inhibition was associated with a significant mortality reduction at 30 days, from 6.2% to 4.6% (OR 0.74; 95% CI 0.59 to 0.92; P=0.007). Conversely, 23 072 nondiabetic patients had no survival benefit (3.0% versus 3.0%). The interaction between platelet GP IIb/IIIa inhibition and diabetic status was statistically significant (P=0.036). Among 1279 diabetic patients undergoing percutaneous coronary intervention (PCI) during index hospitalization, the use of these agents was associated with a mortality reduction at 30 days from 4.0% to 1.2% (OR 0.30; 95% CI 0.14 to 0.69; P=0.002).

CONCLUSIONS

This meta-analysis, including the entire large-scale trial experience of intravenous platelet GP IIb/IIIa inhibitors for the medical management of non-ST-segment-elevation ACS, shows that these agents may significantly reduce mortality at 30 days in diabetic patients. Although not based on a randomized assessment, the survival benefit appears to be of greater magnitude in patients undergoing PCI. Therefore, the use of platelet GP IIb/IIIa inhibitors should be strongly considered in diabetic patients with ACS.

Dual antiplatelet therapy with clopidogrel and aspirin after carotid artery stenting

BACKGROUND

Carotid artery stenting is being used as an alternative to carotid endarterectomy, both within the context of clinical trials and in non-surgical candidates. Though stenting is known to activate platelets, the role of antithrombotic therapy in carotid stenting has not been fully characterized.

METHODS AND RESULTS

Consecutive patients (n = 162) were followed in a single-center carotid stent registry. The cumulative rate of 30-day death, stroke, transient ischemic attack and myocardial infarction in those patients receiving a thienopyridine was determined, as were rates of stent thrombosis and intracranial hemorrhage. The mean age of the patients was 70.3 years and there was an extremely high prevalence of cardiovascular comorbidities, including 40% with unstable angina. The carotid lesion was symptomatic in 59% of patients. The average pre-treatment stenosis was 83%. The cumulative 30-day rate of death, stroke, transient ischemic attack and myocardial infarction was 5.6%. Specifically, in the patients who received ticlopidine (n = 23), the rate was 13%, versus 4.3% in the patients who received clopidogrel (n = 139) (p = 0.01). In this series, there were no cases of stent thrombosis and 1 intracranial hemorrhage.

CONCLUSION

Dual antiplatelet therapy with clopidogrel plus aspirin in patients receiving carotid artery stents is associated with a low rate of ischemic events. Furthermore, clopidogrel appears superior to ticlopidine. Thus, our findings lend support to the dual antiplatelet strategy of clopidogrel plus aspirin for patients undergoing carotid artery stenting.

Self-expanding stents for carotid interventions: comparison of nitinol versus stainless-steel stents

BACKGROUND

Angioplasty and stenting are becoming increasingly accepted techniques for the treatment of carotid stenosis. However, the optimal stent for carotid intervention is not known.

METHODS

We compared the short- and intermediate-term results of carotid stenting using either nitinol or stainless-steel self-expanding stents in 178 high surgical risk patients undergoing carotid stenting at our institution. Of these 178 patients, eighty-nine received stainless-steel stents and 89 received nitinol stents. The groups were similar with respect to age, gender, diabetes, hypertension, left ventricular function, and symptom status. There were more patients with contralateral carotid occlusion in the nitinol stent group. Independent neurological evaluation was performed in all patients pre- and post-carotid stenting.

RESULTS

At 6 months, there was a similar incidence of stroke (3.3% versus 2.2%) in the stainless-steel group and nitinol stent group, respectively. There was higher 6-month mortality noted in the stainless-steel stent group, but there were no neurological deaths in either group.

CONCLUSIONS

In a single-center patient cohort with similar baseline characteristics, patients receiving nitinol stents and stainless-steel stents had similar neurological outcomes.

Risk of cardiovascular events associated with selective COX-2 inhibitors

Atherosclerosis is a process with inflammatory features and selective cyclooxygenase 2 (COX-2) inhibitors may potentially have antiatherogenic effects by virtue of inhibiting inflammation. However, by decreasing vasodilatory and antiaggregatory prostacyclin production, COX-2 antagonists may lead to increased prothrombotic activity. To define the cardiovascular effects of COX-2 inhibitors when used for arthritis and musculoskeletal pain in patients without coronary artery disease, we performed a MEDLINE search to identify all English-language articles on use of COX-2 inhibitors published between 1998 and February 2001. We also reviewed relevant submissions to the US Food and Drug Administration by pharmaceutical companies. Our search yielded 2 major randomized trials, the Vioxx Gastrointestinal Outcomes Research Study (VIGOR; 8076 patients) and the Celecoxib Long-term Arthritis Safety Study (CLASS; 8059 patients), as well as 2 smaller trials with approximately 1000 patients each. The results from VIGOR showed that the relative risk of developing a confirmed adjudicated thrombotic cardiovascular event (myocardial infarction, unstable angina, cardiac thrombus, resuscitated cardiac arrest, sudden or unexplained death, ischemic stroke, and transient ischemic attacks) with rofecoxib treatment compared with naproxen was 2.38 (95% confidence interval, 1.39-4.00; P =.002). There was no significant difference in cardiovascular event (myocardial infarction, stroke, and death) rates between celecoxib and nonsteroidal anti-inflammatory agents in CLASS. The annualized myocardial infarction rates for COX-2 inhibitors in both VIGOR and CLASS were significantly higher than that in the placebo group of a recent meta-analysis of 23 407 patients in primary prevention trials (0.52%): 0.74% with rofecoxib (P =.04 compared with the placebo group of the meta-analysis) and 0.80% with celecoxib (P =.02 compared with the placebo group of the meta-analysis). The available data raise a cautionary flag about the risk of cardiovascular events with COX-2 inhibitors. Further prospective trial evaluation may characterize and determine the magnitude of the risk.

Update on peripheral vascular diseases: from smoking cessation to stenting

Newer pharmacologic agents including gene therapy hold promise for the treatment of atherosclerotic peripheral vascular disease (PVD), as do advances in endovascular revascularization techniques. Nonetheless, the two most important treatments remain the same: stopping smoking and starting a walking program.

Clinical outcome of a cohort of patients eligible for therapeutic angiogenesis or transmyocardial revascularization

BACKGROUND

Newer methods of coronary revascularization are being investigated in patients who are not candidates for coronary artery bypass grafting or percutaneous intervention. Our objective was to determine the proportion of patients eligible for newer methods of revascularization and determine their 1-year clinical outcome.

METHODS

Five hundred consecutive charts and angiograms from patients undergoing diagnostic angiography for coronary artery disease from January to May of 1998 were reviewed to assess the suitability for revascularization. Patients ineligible for conventional revascularization were followed up for 1 year.

RESULTS

Fifty-nine patients of the 500 studied were identified who had refractory ischemia but were not candidates for traditional revascularization. The 59 patients ineligible for traditional methods of revascularization had a rehospitalization rate of 128% (76 total hospitalizations), a 25.5% rate of myocardial infarction (15 of 59), and a mortality rate of 16.9% (10 of 59).

CONCLUSIONS

The prognosis of many patients eligible for newer methods of revascularization on maximal medical therapy is poor.

Long-term exposures to higher environmental temperature and body temperature: effect of chlorpromazine in relation to hypothalamic GABA

Treatment with a single dose of chlorpromazine (CPZ; 1 mg/kg, ip) at room temperature (28 degrees +/-0.5 degrees C) significantly reduced body temperature by its anticholinergic action. Long-term exposures to higher environmental temperature (40 degrees +/-0.5 degrees C, 2 h/day, for 30 consecutive days) increased body temperature significantly by reduction of hypothalamic GABAergic activity, but this increase in body temperature was attenuated from that observed with a single exposure to higher environmental temperature (40 degrees C for 2 h). Treatment with a single dose of CPZ on the last day of 30 consecutive days of exposures to higher environmental temperature increased body temperature of rats more than that observed with long-term exposures to higher environmental temperature possibly due to (i) reduction of hypothalamic GABAergic activity, (ii) heat dissipation and (iii) reverse-anticholinergic action of CPZ at higher environmental temperature.

Fas-induced apoptosis in mouse hepatocytes is dependent on C/EBPbeta

Apoptotic cell death in the liver in response to activation of the Fas pathway has been implicated in human disease states as well as liver remodeling and tissue repair. C/EBPbeta, a member of the CCAAT enhancer binding protein family of bZIP transcription factors has been linked to both growth response and apoptotic targets in the liver, and, therefore, is a likely candidate for the regulation of apoptotic liver injury. We investigated differences in apoptotic cell death in the livers of C/EBPbeta-null mice using the Jo-2 agonistic anti-Fas antibody. Apoptotic injury was dramatically reduced in C/EBPbeta -/- livers as shown by a nearly 20-fold reduction in apoptotic hepatocytes 6 hours post-Jo-2 treatment in C/EBPbeta -/- hepatocytes compared with controls (P < .04) and reduced activation of caspase 3. Bid cleavage occurred in Jo-2 treated C/EBPbeta -/- livers indicating a block of Fas-induced injury distal to the death-inducing signaling complex. The level of the antiapoptotic protein bcl-x(L) was increased greater than tenfold in the mutant animals (P < .04), which can, at least in part, account for the protection from Fas-mediated apoptosis. In contrast, bcl-x(L) mRNA levels were unchanged. These observations link C/EBPbeta to Fas-induced hepatocyte apoptosis through a mechanism that likely involves translational or posttranslational regulation of bcl-x(L).