Antiplatelet therapy in patients with myocardial infarction without obstructive coronary artery disease

OBJECTIVE

Approximately 10% of patients with myocardial infarction (MI) have no obstructive coronary artery disease. The prognosis and role of intensified antiplatelet therapy in those patients were evaluated.

METHODS

We analysed data from the Clopidogrel and Aspirin Optimal Dose Usage to Reduce Recurrent Events-Seventh Organisation to Assess Strategies in Ischaemic Symptoms trial randomising patients with ACS referred for early intervention to receive either double-dose (600 mg, day 1; 150 mg, days 2-7; then 75 mg/day) or standard-dose (300 mg, day 1; then 75 mg/day) clopidogrel. Outcomes in patients with myocardial infarction with non-obstructive coronary arteries (MINOCA) versus those with obstructive coronary artery disease (CAD) and their relation to standard-dose versus double-dose clopidogrel were evaluated. The primary outcome was cardiovascular (CV) death, MI or stroke at 30 days.

RESULTS

We included 23 783 patients with MI and 1599 (6.7%) with MINOCA. Patients with MINOCA were younger, presented more frequently with non-ST-segment elevation MI and had fewer comorbidities. All-cause mortality (0.6% vs 2.3%, p=0.005), CV mortality (0.6% vs 2.2%, p=0.006), repeat MI (0.5% vs 2.3%, p=0.001) and major bleeding (0.6% vs 2.4%, p<0.0001) were lower among patients with MINOCA than among those with obstructive CAD. Among patients with MINOCA, 2.1% of patients in the double-dose clopidogrel group and 0.6% in the standard-dose group experienced a primary outcome (HR 3.57, 95% CI 1.31 to 9.76), whereas in those with obstructive CAD, rates were 4.3% and 4.7%, respectively (HR 0.91, 95% CI 0.80 to 1.03; p value for interaction=0.011).

CONCLUSIONS

Patients with MINOCA are at lower risk of recurrent CV events compared with patients with MI with obstructive CAD. Compared with a standard clopidogrel-based dual antiplatelet therapy (DAPT) regimen, an intensified dosing strategy appears to offer no additional benefit with a signal of possible harm. Further randomised trials evaluating the effects of potent DAPT in patients with MINOCA are warranted.

TRIAL REGISTRATION NUMBER

NCT00335452.

Perioperative intravenous contrast administration and the incidence of acute kidney injury after major gastrointestinal surgery: prospective, multicentre cohort study

BACKGROUND

This study aimed to determine the impact of preoperative exposure to intravenous contrast for CT and the risk of developing postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery.

METHODS

This prospective, multicentre cohort study included adults undergoing gastrointestinal resection, stoma reversal or liver resection. Both elective and emergency procedures were included. Preoperative exposure to intravenous contrast was defined as exposure to contrast administered for the purposes of CT up to 7 days before surgery. The primary endpoint was the rate of AKI within 7 days. Propensity score-matched models were adjusted for patient, disease and operative variables. In a sensitivity analysis, a propensity score-matched model explored the association between preoperative exposure to contrast and AKI in the first 48 h after surgery.

RESULTS

A total of 5378 patients were included across 173 centres. Overall, 1249 patients (23·2 per cent) received intravenous contrast. The overall rate of AKI within 7 days of surgery was 13·4 per cent (718 of 5378). In the propensity score-matched model, preoperative exposure to contrast was not associated with AKI within 7 days (odds ratio (OR) 0·95, 95 per cent c.i. 0·73 to 1·21; P = 0·669). The sensitivity analysis showed no association between preoperative contrast administration and AKI within 48 h after operation (OR 1·09, 0·84 to 1·41; P = 0·498).

CONCLUSION

There was no association between preoperative intravenous contrast administered for CT up to 7 days before surgery and postoperative AKI. Risk of contrast-induced nephropathy should not be used as a reason to avoid contrast-enhanced CT.

2387Recurrent cardiovascular events and mortality in relation to antiplatelet therapy in patients with myocardial infarction without obstructive coronary artery disease (MINOCA)

Background

Approximately 10% of patients presenting with myocardial infarction (MI) do not have obstructive coronary artery disease (MINOCA). The role of antiplatelet therapy and outcomes in this group remain unclear. We assessed prognosis and the effect of an intensified clopidogrel regimen in MINOCA patients.

Methods

We analyzed data from the CURRENT-OASIS 7 trial, which randomized 25,086 patients with acute coronary syndromes (ACS) referred for early intervention to receive either double-dose (600mg day 1; 150mg days 2–7; then 75mg daily) or standard-dose (300mg day 1; then 75mg daily) clopidogrel. We evaluated clinical outcomes at 30-days in patients with versus without obstructive CAD and in relation to standard versus double-dose clopidogrel.

Results

Overall, 23,783 MI patients were included, of which 1,599 (6.7%) had MINOCA. MINOCA patients were younger, more frequently presented with non-ST-segment elevation MI and had fewer comorbidities. Rates of all-cause mortality (0.7% versus 2.4%, p=0.0046), cardiovascular mortality (0.6 versus 2.2%, p=0.0056), repeat MI (0.5% versus 2.3%, p=0.0009) and major bleedings (0.7% versus 2.5%, p=0.0001) were significantly lower among patients with MINOCA versus those with obstructive CAD. Compared with the standard-dose clopidogrel regimen, the double-dose regimen appeared to increase the risk of cardiovascular death, MI or stroke in MINOCA patients (0.8% versus 2.1%, hazard ratio (HR) 2.74, P=0.033). There was no difference in those with obstructive CAD (4.7% versus 4.4%, HR 0.93, P=0.226; P-for-interaction=0.023) (see Figure 1A). Major bleeding did not occur more frequently in MINOCA patients with double- versus standard-dose clopidogrel regimen (0.7% versus 0.6%, (HR 1.16 (95% CI 0.35–3.80), p=0.805), but their rate was higher In MI patients with obstructive CAD (2.7% versus 2.2% (HR 1.26 (95% CI 1.06–1.49), p=0.008) (Figure 1B).

Figure 1A & B

Conclusions

Compared to MI patients with obstructive CAD, patients presenting with MINOCA represent a distinct cohort, which is generally younger, has a higher NSTEMI prevalence and fewer comorbidities. Their risk for adverse events, especially repeat MI, stroke, death, and bleeding, is low (<1%) at 30 days. Applying an intensified clopidogrel regimen in MINOCA patients appears to be related to a higher risk for CV death, MI and stroke. Accordingly, more potent antiplatelet regimens might be harmful among MINOCA patients and should not be administered routinely. Nevertheless, there is a need for more prospective studies evaluating the role of dual antiplatelet therapies in MINOCA patients.

Acknowledgement/Funding

The CURRENT-OASIS 7 trial was sponsored by Sanofi-Aventis and Bristol-Myers Squibb.

Critical care usage after major gastrointestinal and liver surgery: a prospective, multicentre observational study

BACKGROUND

Patient selection for critical care admission must balance patient safety with optimal resource allocation. This study aimed to determine the relationship between critical care admission, and postoperative mortality after abdominal surgery.

METHODS

This prespecified secondary analysis of a multicentre, prospective, observational study included consecutive patients enrolled in the DISCOVER study from UK and Republic of Ireland undergoing major gastrointestinal and liver surgery between October and December 2014. The primary outcome was 30-day mortality. Multivariate logistic regression was used to explore associations between critical care admission (planned and unplanned) and mortality, and inter-centre variation in critical care admission after emergency laparotomy.

RESULTS

Of 4529 patients included, 37.8% (n=1713) underwent planned critical care admissions from theatre. Some 3.1% (n=86/2816) admitted to ward-level care subsequently underwent unplanned critical care admission. Overall 30-day mortality was 2.9% (n=133/4519), and the risk-adjusted association between 30-day mortality and critical care admission was higher in unplanned [odds ratio (OR): 8.65, 95% confidence interval (CI): 3.51-19.97) than planned admissions (OR: 2.32, 95% CI: 1.43-3.85). Some 26.7% of patients (n=1210/4529) underwent emergency laparotomies. After adjustment, 49.3% (95% CI: 46.8-51.9%, P<0.001) were predicted to have planned critical care admissions, with 7% (n=10/145) of centres outside the 95% CI.

CONCLUSIONS

After risk adjustment, no 30-day survival benefit was identified for either planned or unplanned postoperative admissions to critical care within this cohort. This likely represents appropriate admission of the highest-risk patients. Planned admissions in selected, intermediate-risk patients may present a strategy to mitigate the risk of unplanned admission. Substantial inter-centre variation exists in planned critical care admissions after emergency laparotomies.

Temporospatial fate of bacteria and immune effector expression in house flies fed GFP-Escherichia coli O157:H7

The house fly Musca domestica L. (Diptera: Muscidae) harbours and transmits a variety of human enteropathogens including Escherichia coli (Enterobacteriales: Enterobacteriaceae) O157:H7. Interactions between ingested bacteria and the fly gut directly impact bacterial persistence, survival and ultimately fly vector competence. We assessed the temporospatial fate of green fluorescent protein (GFP)-expressing E. coli O157:H7 (GFP-ECO157) in house flies along with fly antimicrobial responses up to 12 h post-ingestion. In flies fed GFP-ECO157, culture and microscopy revealed a steady decrease in bacterial load over 12 h, which is likely to be attributable to the combined effects of immobilization within the peritrophic matrix, lysis and peristaltic excretion. However, flies can putatively transmit this pathogen in excreta because intact bacteria were observed in the crop and rectum. Quantitative reverse-transcriptase polymerase chain reaction analysis of antimicrobial peptides (AMPs) and lysozyme gene expression showed minimal upregulation in both the gut and carcass of house flies fed GFP-ECO157. However, these genes were upregulated in fly heads and salivary glands, and effector proteins were detected in the gut in some flies. Collectively, these data indicate that house flies can serve as reservoirs of E. coli O157:H7 for up to 12 h, and factors in addition to AMPs and lysozyme may contribute to bacteria destruction in the gut.

Rationale and design of ACTIVE: the atrial fibrillation clopidogrel trial with irbesartan for prevention of vascular events

BACKGROUND

Atrial fibrillation (AF) is the most frequently occurring cardiac arrhythmia with often serious clinical consequences. Many patients have contraindications to anticoagulation, and it is often underused in clinical practice. The addition of clopidogrel to aspirin (ASA) has been shown to reduce vascular events in a number of high-risk populations. Irbesartan is an angiotensin receptor-blocking agent that reduces blood pressure and has other vascular protective effects.

METHODS AND RESULTS

ACTIVE W is a noninferiority trial of clopidogrel plus ASA versus oral anticoagulation in patients with AF and at least 1 risk factor for stroke. ACTIVE A is a double-blind, placebo-controlled trial of clopidogrel in patients with AF and with at least 1 risk factor for stroke who receive ASA because they have a contraindication for oral anticoagulation or because they are unwilling to take an oral anticoagulant. ACTIVE I is a partial factorial, double-blind, placebo-controlled trial of irbesartan in patients participating in ACTIVE A or ACTIVE W. The primary outcomes of these studies are composites of vascular events. A total of 14000 patients will be enrolled in these trials.

CONCLUSIONS

ACTIVE is the largest trial yet conducted in AF. Its results will lead to a new understanding of the role of combined antiplatelet therapy and the role of blood pressure lowering with an angiotensin II receptor blocker in patients with AF.

Pluripotential mesenchymal cells repopulate bone marrow and retain osteogenic properties

Precursor cells, isolated from bone marrow, can develop into various cell types and may contribute to skeletal growth, remodeling, and repair. The D1 cell line was cloned from a multipotent mouse bone marrow stromal precursor and has osteogenic, chondrogenic, and adipogenic properties. The osteogenic phenotype of these precursor cells is relevant to the process of fracture healing and osteointegration of prosthetic implants. The D1 cells were labeled genetically using a replication incompetent retroviral vector encoding beta-galactosidase, an enzyme which is used as a marker. Labeled cells are readily identifiable by staining with 5-bromo-4-chloro-3-indoyl-beta-D-galactoside and by flow cytometry, and retain the desired osteogenic characteristics in vivo as shown by von Kossa staining, alkaline phosphatase assay, an increase in cyclic adenosine monophosphate in response to parathyroid hormone, osteocalcin messenger ribonucleic acid production, and bone formation in diffusion chambers. In addition, the cells cloned from marrow stroma repopulate the marrow of host mice, persist for several weeks, and retain their osteogenic potential ex vivo. The data suggest that such cells may be used to replenish the number of osteoprogenitors in marrow, which appear to decrease with age, thereby leading to recovery from bone loss and improved bone growth and repair. Labeling these cells creates a model in which to study the potential of such cells to participate in fracture repair, ingrowth around prosthetic implants, treatment of osteoporosis, and to explore the possibility of gene delivery to correct mutations or defects in metabolism that are responsible for certain skeletal abnormalities.

Anatomical effects of periosteal elevation

Research that involves harvesting the periosteum is common. The exact technique of harvesting is rarely described; however, it may be of vital importance because techniques may vary in their ability to raise the osteogenic cambial layer, which is reported to be tightly adherent to the underlying cortex. This study was performed to define how the cambial and fibrous layers of the periosteum are affected by different techniques of stripping. The periosteum was raised from the tibia and the humerus of adult rabbits with four stripping techniques. The stripped bone surface was examined histologically and with a scanning electron microscope to determine whether the fibrous and cambial layers of the periosteum had been removed and whether there had been damage to the underlying cortex. The results from the two anatomical sites were the same. Raising the periosteum with cortical bone chips (shingling) or with a periosteal elevator removed both layers of the periosteum and caused considerable damage to the surface of the cortex. Raising the periosteum with a sharp scalpel or by simply pulling it off removed the fibrous layer but left the osteogenic layer intact adherent to the cortex. We conclude that some techniques of periosteal elevation fail to harvest the osteogenic layer and therefore may lead to unexpected experimental results. We suggest that authors describe the exact technique of periosteal stripping that was employed.

Cerebral microembolism in acute myocardial infarction

BACKGROUND AND PURPOSE

This study was undertaken to determine the frequency of cerebral microemboli (high-intensity transient signals; HITS) detected by transcranial Doppler (TCD) in patients with acute myocardial infarction (AMI) and to relate them to the various putative risk factors and clinical embolic events.

METHODS

We investigated 112 consecutive patients within 72 hours of admission to an acute coronary care unit using TCD to monitor for cerebral microemboli. Twelve patients were excluded because of failure of ultrasound insonation. All patients had 2-dimensional echocardiograms within the study period.

RESULTS

HITS were detected in 17% of patients, with significantly higher frequency in patients with reduced (<65%) left ventricular (LV) ejection fraction (P=0. 019), akinetic LV segments (P=0.002), and LV thrombus (P=0.015). A marginally significant (P=0.059) increase of HITS was found in patients with anterior AMI. Stroke was significantly more frequent in patients with cerebral microemboli (P=0.01).

CONCLUSIONS

HITS were detected in 17% of patients in spite of adequate antithrombotic therapy and were increased in patients with reduced LV function, akinetic myocardial segments, and LV thrombus. They were present in all 3 patients with stroke and may represent a predictor of clinical embolic events.

Is colour flow imaging needed to exclude clinically significant valvular regurgitation in adult patients undergoing transthoracic echocardiography?

OBJECTIVE

To establish whether clinically significant aortic and mitral valvular regurgitation can be excluded in adult patients undergoing transthoracic echocardiography without using colour flow imaging.

SETTING

Sunnybrook Health Science Centre, a tertiary referral centre with full cardiovascular services affiliated with the University of Toronto, Toronto, Ontario.

DESIGN

Logistic regression models were developed from a retrospective review of 14,051 unselected consecutive echocardiograms from 1991 through 1994. The dependent variable was more than mild aortic or mitral valvular regurgitation. Independent variables included age, sex and various functional and structural measures obtained during routine two-dimensional echocardiography. The negative predictive values and sensitivity of the models were estimated.

INTERVENTION

The number of patients correctly classified by these models, as well as the proportion for whom the colour flow imaging did not add to the baseline echocardiogram, was determined. Nonparametric bootsrapping was used to obtain confidence intervals for these statistics.

MAIN RESULTS

Ten models were developed, with negative predictive values ranging from 96.2% to 100%. Incorporation of such decision aids into the software of echocardiographic machinery would help echocardiographers to rule out significant aortic or mitral regurgitant lesions. In practices where colour flow imaging is routinely employed, 40% fewer procedures could be performed.

CONCLUSIONS

Models based on simple demographic and two-dimensional echocardiographic variables can reliably exclude significant valvular regurgitation and could potentially reduce the volumes and costs of colour flow imaging. Given the widespread diffusion of colour Doppler imaging, the models may also be helpful to avoid misinterpretation of flow imaging results, by defining subgroups in whom the prior probability of significant aortic or mitral regurgitation is extremely low.

Arthroplasty implant biomaterial particle associated macrophages differentiate into lacunar bone resorbing cells

OBJECTIVE

To study the pathogenesis of aseptic loosening: in particular, to determine whether macrophages responding to particles of biomaterials commonly used in arthroplasty surgery for arthritis are capable of differentiating into osteoclastic bone resorbing cells, and the cellular and hormonal conditions required for this to occur.

METHODS

Biomaterial particles (polymethylmethacrylate, high density polyethylene, titanium, chromium-cobalt, stainless steel) were implanted subcutaneously into mice. Macrophages were isolated from the foreign body granulomas that resulted, cultured on bone slices and coverslips, and assessed for both cytochemical and functional evidence of osteoclast differentiation.

RESULTS

Tartrate resistant acid phosphatase (TRAP) negative macrophages isolated from granulomas containing particles of all types of biomaterial composition were capable of differentiating into TRAP positive cells capable of extensive lacunar bone resorption (assessed by scanning electron microscopy). The presence of both UMR106 rat osteoblast-like cells and 1,25-dihydroxy vitamin D3 was necessary for this to occur.

CONCLUSION

All implant materials produce wear particles that are the focus of a heavy foreign body macrophage response in the fibrous membrane between a loose implant component and the host bone undergoing resorption. These findings underline the importance of biomaterial wear particle generation and the macrophage response to different types of biomaterial wear particles in the pathogenesis of aseptic loosening.

Continuous or intermittent cocaine administration: effects of flupenthixol treatment during withdrawal

Research indicates that chronic daily cocaine injections produce sensitization to, while the chronic continuous infusion of cocaine produces tolerance to, its behavioral and neurochemical effects. The present experiments examined whether flupenthixol administration during withdrawal would attenuate/eliminate the behavioral effects produced by these administration regimens. The rats were pretreated for 14 days with either continuous or intermittent daily injections of cocaine, and were then withdrawn from the pretreatment regimen for 7 days. On days 1-5 of the withdrawal period, subjects received a daily 0.125-2.0 mg/kg IP injection of flupenthixol. Then on day 7 of withdrawal from the cocaine pretreatment, all rats were given a 15.0 mg/kg IP injection of cocaine. Their behavior was rated according to a modified version of the Ellinwood and Balster (6) scale for 60 min. The results indicated that flupenthixol treatment during withdrawal eliminated the tolerance normally associated with the continuous infusion of cocaine. However, this effect of flupenthixol was not dose dependent: the lowest dose had the same effect as the highest dose of flupenthixol. In the cocaine-injection subjects, flupenthixol had a slight but statistically significant reduction in the behavioral effects of cocaine. The same was true in the saline-control rats, except for the highest dose of flupenthixol, which had a significant enhancing effect on the behavioral response to cocaine. The present results suggest that the current procedures may represent an effective screening methodology for potential cocaine pharmacotherapies.

Continuous or intermittent cocaine administration: effects of amantadine treatment during withdrawal

Research indicates that daily cocaine injections produce sensitization to, while the continuous infusion of cocaine produces tolerance to, its behavioral and neurochemical effects. The effects of the continuous infusion of cocaine are consistent with the withdrawal syndrome reported by human cocaine abusers. The present experiment examined whether amantadine administrations during withdrawal from continuous or intermittent cocaine attenuate and/or eliminate the behavioral effects produced by these administration regimens. The rats were pretreated for 14 days with either continuous or intermittent daily injections of cocaine, and were then withdrawn from the pretreatment regimen for 7 days. On days 1-5 of the withdrawal period, half the subjects received a 5.0 mg/kg IP injection of amantadine, and the other half received a 20.0 mg/kg IP injection of amantadine. On day 7 of withdrawal from the cocaine pretreatment, all rats were given a 15.0 mg/kg IP injection of cocaine. Their behavior was rated according to the modified Ellinwood and Balster (6) scale for 60 min. The results indicated that amantadine treatment during withdrawal eliminated the tolerance normally associated with the continuous infusion of cocaine. In contrast, in both the saline control and daily injection subjects amantadine treatment during withdrawal resulted in a slight, but statistically significant, reduction in the behavioral effects of cocaine. The present results therefore indicate that low doses of amantadine should be considered as a potential pharmacotherapy for the early stages of cocaine withdrawal. Furthermore, the present experimental procedures may represent an effective screening methodology for potential cocaine pharmacotherapies.

Technique for the continuous infusion of high doses of cocaine by osmotic minipump

The present article describes a procedure for modifying osmotic minipumps to avoid the local, toxic, necrotic effects of high concentrations of drug at the exit portal during the chronic, continuous infusion of cocaine. The present procedure eliminates the occurrence of necrotic skin lesions otherwise produced by SC administration of cocaine and/or other vasoconstrictive agents. The method of administration will therefore be useful for administration of other chronic drug regimens.

Withdrawal from continuous or intermittent cocaine: effects of NAN-190 on cocaine-induced locomotion

Rats were pretreated with 40 mg/kg/day cocaine for 14 days by either SC injections or osmotic minipumps. Rats were then withdrawn from the pretreatment regimen for 7 days. In Experiment 1, rats received 0- to 2.0-mg/kg IP injections of 1-(2-methoxyphenyl)-4-[4-(2-phthalimido)butyl]piperazine (NAN-190), a putative 5-hydroxytryptamine1A (5-HT1A) receptor antagonist. In Experiment 2, rats received the same doses of NAN-190 in combination with a 15-mg/kg IP injection of cocaine. The results of Experiment 1 indicate that the continuous-infusion group demonstrated a dose-dependent suppression of locomotor behavior by single doses of NAN-190. NAN-190 had no consistent dose-dependent effect on the locomotor behavior of subjects in the other pretreatment groups. The results of Experiment 2 indicate that rats receiving intermittent, daily injections tended to exhibit behavior consistent with 5-HT1A receptor supersensitivity. In contrast, rats receiving continuous cocaine tended to exhibit behavior consistent with 5-HT1A receptor subsensitivity. Changes in 5-HT1A receptor sensitivity may contribute to some of the anxiety and depressive symptoms exhibited by human cocaine abusers.

Two cell lines from bone marrow that differ in terms of collagen synthesis, osteogenic characteristics, and matrix mineralization

Two cloned cell lines were isolated from cultures of mouse bone-marrow cells. One of the lines, D1, exhibited osteogenic properties and synthesized type-I collagen (alpha 1)2 alpha 2. The second cell line, D2, was not osteogenic and produced a collagen homotrimer (alpha 1)3. Whereas the extracellular matrix of the D1 cell cultures contained striated collagen fibrils, presumably composed of type-I collagen, the homotrimer-producing D2 cells did not demonstrate striated collagen fibrils. Instead, they had thin filaments without detectable striations. Sodium ascorbate stimulated collagen synthesis at the transcriptional level in both the D1 and the D2 cells. The bone-producing characteristics of D1 in vitro included high levels of alkaline phosphatase, increased cyclic adenosine monophosphate on treatment with parathyroid hormone, and expression of osteocalcin mRNA. The D1 cells, unlike the D2 cells, produced a mineralized matrix in vitro. Mineralization in the cultures of the D1 cells occurred in nodules of increased cell density, which also contained the cells with the highest concentrations of collagen mRNA, as shown by in situ hybridization. When the D1 cells were implanted in a diffusion chamber in vivo, a mixture of both osteogenic and adipogenic tissues was formed. This indicates that the D1 cell line is derived from an early marrow stromal precursor that is multipotential.

Intermittent and continuous cocaine administration: residual behavioral states during withdrawal

Rats were pretreated with 40 mg/kg/day cocaine for 14 days by either subcutaneous injections or osmotic minipumps. Rats were then withdrawn from the pretreatment regime for 1 or 7 days and given a 20-mg/kg IP cocaine challenge (day 1) or a 0-, 10-, 20-, or 40-mg/kg IP cocaine challenge (day 7). The results indicate that rats receiving intermittent, daily injections exhibited sensitization to the behavioral effects of a cocaine challenge on days 1 and 7 of withdrawal. In contrast, rats receiving continuous cocaine exhibited tolerance to the behavioral effects of a cocaine challenge on days 1 and 7 of withdrawal. The present results support and extend previous research that indicates that the route and temporal pattern of administration influences the effects of chronic cocaine. Furthermore, the present results indicate that the continuous infusion paradigm may represent an alternative animal model of some aspects of high-dose cocaine abuse, as compared to the typical procedure of single, or multiple, daily cocaine injections.

Polymethylmethacrylate-induced inflammatory macrophages resorb bone

Macrophages and their fused products are commonly found at the polymethylmethacrylate cement-bone interface, but it is not known if they contribute directly to the osteolysis associated with loosening of the cemented prosthesis. We isolated mononuclear phagocytes from granulomas formed by subcutaneous implantation of polymethylmethacrylate into mice and incubated them on bone slices in which they formed resorption lacunae after co-culture for seven to 14 days with both marrow stromal cells and osteoblast-like cells (in the presence of 1 alpha,25-dihydroxyvitamin D3 and dexamethasone). Increased numbers of tartrate-resistant acid phosphatase-positive mononuclear and multinucleated cells formed in these cultures. Both in the presence and absence of stromal cells, macrophages produced extensive superficial roughening of the bone surface. Polymethylmethacrylate-induced macrophages are thus capable of low-grade surface and high-grade lacunar osteolysis, the latter requiring the presence of specific hormonal and stromal cell elements. These two forms of bone resorption could account for the pathogenesis and clinical patterns associated with loosening of the cemented prosthesis.

How should results from completed studies influence ongoing clinical trials? The CAFA Study experience

Seven randomized studies during the past 5 years have evaluated or are evaluating the efficacy of warfarin or aspirin or both in decreasing the risk of embolic events in patients with nonrheumatic atrial fibrillation. By March 1990, two of the studies had been published, both of which showed a statistically significant decrease in embolic events in patients treated with warfarin and a low rate of major bleeding events. The investigators associated with the other ongoing studies were forced to consider how these results should affect the decision to recruit and continue follow-up of patients in their own studies. The Steering Committee of the Canadian Atrial Fibrillation Anticoagulation (CAFA) study thought the newly published results from other studies were valid, clinically important, and generalizable. The committee considered the following options for the CAFA study: continue patient recruitment as planned, provide the data available in CAFA to its External Safety and Efficacy Monitoring Committee for analysis to determine whether the CAFA data already showed a benefit of warfarin, stop patient recruitment but continue to follow patients in the group to which they were assigned, stop the trial immediately and perform a final analysis, and attempt to perform a meta-analysis of all data available from all trials. The Steering Committee of CAFA decided that the evidence of benefit with warfarin, from the two published studies, was sufficiently compelling as to stop recruitment into CAFA without any preliminary examination of the CAFA data.

Canadian Atrial Fibrillation Anticoagulation (CAFA) Study

The Canadian Atrial Fibrillation Anticoagulation Study was a randomized double-blind placebo-controlled trial to assess the potential of warfarin to reduce systemic thromboembolism and its inherent risk of hemorrhage. As a result of the publication of two other "positive" studies of similar design and objective, this study was stopped early before completion of its planned recruitment of 630 patients. There were 187 patients randomized to warfarin and 191 to placebo. Permanent discontinuation of study medication occurred in 26% of warfarin-treated and 23% of placebo-treated patients. The target range of the international normalized ratio was 2 to 3. For the warfarin-treated patients, the international normalized ratio was in the target range 43.7% of the study days, above it 16.6% of the study days and below it 39.6% of the study days. Fatal or major bleeding occurred at annual rates of 2.5% in warfarin-treated and 0.5% in placebo-treated patients. Minor bleeding occurred in 16% of patients receiving warfarin and 9% receiving placebo. The primary outcome event cluster was nonlacunar stroke, noncentral nervous systemic embolism and fatal or intracranial hemorrhage. Events were included in the primary analysis of efficacy if they occurred within 28 days of permanent discontinuation of the study medication. The annual rates of the primary outcome event cluster were 3.5% in warfarin-treated and 5.2% in placebo-treated patients, with a relative risk reduction of 37% (95% confidence limits, -63.5%, 75.5%, p = 0.17).(ABSTRACT TRUNCATED AT 250 WORDS)