P2859Low rates of mechanical failures of silicone-polyurethane copolymer-coated ICD leads: 11 years prospective follow-up

Background

High rates of ICD lead mechanical failures (insulation abrasion and conductor fracture) resulted in FDA recalls and substantial design modifications. Most subsequent reports of lead failures of newer generation leads are based upon modest-sized, retrospective cohorts with relatively brief follow-up and may be unreliable. Following lead modifications (including silicone-polyurethane copolymer insulation coating), in 2007, one manufacturer established 3 prospective registries, and engaged a university-based methods center to independently review the registries, to adjudicate all reports of lead failures and to independently analyze lead survival. Up to 11 years of follow-up is now available.

Purpose

To adjudicate all reports of leads inactivated because of possible mechanical failure and to independently calculate rates of mechanical failure overall and by specific type.

Methods

Manufacturer expert staff confirm each lead inactivation by site interrogation. Following formal algorithms which incorporate lead testing and remote monitoring, they designate all-cause mechanical failure (fracture; insulation abrasion; failure at crimp, bond or weld; or uncertain) based upon the finding of electrical noise, very low or very high or rapidly rising impedance or alternatively they designate non-mechanical dysfunction (e.g. no impedance criteria but elevated thresholds, over or under sensing). The results of returned product analyses are incorporated when available (31%). The methods center receives electronic data transfers twice yearly, reviews all documentation, adjudicates all instances of possible lead failure, assigns probable cause (by 2 electrophysiologists) and conducts independent analyses of lead survival.

Results

10,866 patients (73% male, mean age 65.9 yr., LVEF 29.3%, NYHA class II or III 89%) with 11,132 leads had follow-up of 4.6 yr. (median) and 11 yr. (maximum) (Aug 31, 2018). Lead follow-up was censored at the time of lead inactivation, death/transplant or administrative withdrawal. Of leads enrolled, there were 26.6% still in follow-up and of those not the status was 7.4% inactivated, 29.5% death or transplant, 33.8% administrative withdrawal and 3.7% reason missing. Following adjudication, there were 156 all-cause mechanical failures (1.40% total, 0.29%/yr.). Rates of cause-specific mechanical failures were: fracture 1.02% total, 0.22%/yr.; insulation abrasion 0.28% total, 0.06%/yr.; miscellaneous/uncertain 0.12% total, 0.02%/yr.; and externalized conductors 0%. Life-table rates of freedom from lead failure by 11 years were: all-cause mechanical failure 95.9%, conductor fracture 97.0%, insulation abrasion 99.1%, mechanical failure other/uncertain type 99.9%, and externalized conductors 100%.

Conclusions

Up to 11 yr prospective follow-up of silicone-polyurethane-coated ICD leads with independent adjudication and analyses of events shows low rates of all-cause mechanical failure and no externalized conductors.

Acknowledgement/Funding

Abbott

3037The prognostic significance of grade of ischemia in patients with STEMI: a substudy of the randomized trial of primary PCI with or without routine manual thrombectomy (TOTAL trial)

Background

The importance of grade of ischemia (GI) classification in the risk assessment of patients with ST-elevation myocardial infarction has been shown previously. Grade 3 ischemia (G3I) is defined by the Sclarovsky-Birnbaum grading system as ECG with ST-elevation and distortion of the terminal portion of the QRS complex in two or more adjacent leads, while grade 2 ischemia (G2I) is defined as ECG with ST-elevation without QRS distortion.

Methods

In a substudy of the international, multicenter, prospective, randomized Trial of Routine Aspiration Thrombectomy with PCI versus PCI Alone in Patients with STEMI (TOTAL), we studied the prognostic impact of the grade of ischemia classification on the outcome in patients with STEMI (n=7,211). The primary outcome was a composite of death from cardiovascular causes, recurrent MI, cardiogenic shock, or New York Heart Association (NYHA) class IV heart failure within one year.

Results

The primary outcome occurred in 153 of 1,563 patients (9.8%) in the G3I group vs. 364 of 5,648 patients (6.4%) in the G2I group (hazard ratio [HR], 1.55; 95% confidence interval [CI], 1.29 to 1.88; p<0.001). The rates of cardiovascular death (4.8% with G3I vs. 2.5% with G2I; HR, 1.92; 95% CI, 1.45 to 2.54; p<0.001) and all-cause mortality (5.2% with G3I vs. 3.3% with G2I; HR, 1.62; 95% CI, 1.25 to 2.10; p<0.001) were also higher in patients with G3I. The rate of stroke or TIA were similar within the two groups (1.1% with G3I vs. 1.0% with G2I; HR, 1.13; 95% CI, 0.66 to 1.95; p=0.650). The grade of ischemia (G3I vs G2I) was shown to be an independent predictor of primary outcome in adjusted multivariable analysis (adjusted HR, 1.43; 95% CI, 1.18 to 1.74; p<0.001).

Conclusions

STEMI patients with G3I in the presenting ECG proved to have an increased rate of cardiovascular death, recurrent MI, cardiogenic shock, or NYHA class IV heart failure within one year compared to patients with G2I.

Acknowledgement/Funding

Competitive State Research Financing of the Expert Responsibility area of Tampere University Hospital, The unit of Heart Center Co. [Z60064]

Heavy Ion-Induced Characteristic X-Ray Generation as an Analytical Probe

Increasing attention is currently focused on the generation of characteristic x-ray by proton irradiation. This has the advantage of yielding “clean” x-ray- i. e. free from background brerasstrahlung radiation, from even the lightest elements. The disadvantage is that the yields are naturally much lower than those produced by electrons of the same energy. A recent study has extended characteristic x-ray production to a variety of heavy ions and has shown that the cross- sections for the production of clean x-rays are often higher , by as much as several orders of magnitude, than those produced by protons of the same energy. In addition, there has emerged a further advantage, viz. the ability of specially chosen heavy ions to excite characteristic x-ray from a particular element in a selective manner. Since heavy ions penetrate only a few hundred Angstroms in to most solids, the phenomenon can be used as the basis of a technique for the examination of surface deposits, or to measure depth distributions of impurities. For example, Kr ions can be used t o determine the range distribution of antimony which had been implanted in to silicon at 100 keV. The antimony concentration was determined as a function of ∼ 150 Å steps, and was found to exhibit a maximum concentration of ∼ 1 part in 103 of silicon at 450 Å below the surface, falling to zero concentration at ∼2000 Å a depth. In the past, in order to obtain the required degree of sensitivity, such range determinations have relied on radio active tracer techniques.

An entirely new type of proportional counter has been developed during the course of these studies. This instrument, because of its special construction, can be positioned very close to targets in non-dispersive studies, so as to collect the highest possible fraction of emitted x-ray. It incorporates a replaceable anode unit, together with a built- in miniature head amplifier, and exhibits extremely good performance, particularly for ultra-soft x-ray. In addition, rotation of a dial on the end of the counter body allows alteration of the active gas volume during operation, and so permits tuning into x-rays of a particular energy.

Cost-effectiveness of alternative changes to a national blood collection service

Objectives

To evaluate the cost‐effectiveness of changing opening times, introducing a donor health report and reducing the minimum inter‐donation interval for donors attending static centres.

Background

Evidence is required about the effect of changes to the blood collection service on costs and the frequency of donation.

Methods/Materials

This study estimated the effect of changes to the blood collection service in England on the annual number of whole‐blood donations by current donors. We used donors' responses to a stated preference survey, donor registry data on donation frequency and deferral rates from the INTERVAL trial. Costs measured were those anticipated to differ between strategies. We reported the cost per additional unit of blood collected for each strategy versus current practice. Strategies with a cost per additional unit of whole blood less than £30 (an estimate of the current cost of collection) were judged likely to be cost‐effective.

Results

In static donor centres, extending opening times to evenings and weekends provided an additional unit of whole blood at a cost of £23 and £29, respectively. Introducing a health report cost £130 per additional unit of blood collected. Although the strategy of reducing the minimum inter‐donation interval had the lowest cost per additional unit of blood collected (£10), this increased the rate of deferrals due to low haemoglobin (Hb).

Conclusion

The introduction of a donor health report is unlikely to provide a sufficient increase in donation frequency to justify the additional costs. A more cost‐effective change is to extend opening hours for blood collection at static centres.

Laser Induced Fluorescence and Optical Emission Studies of Fluorocarbon Plasmas

Laser induced fluorescence of CF2 has been observed in plasmas of CF4 and its mixtures with O2 and H2. Surface removal rates of the radical in pure CF4 were measured by observing the decay of the radical when the plasma is switched off. The reduction in CF2 concentration, and the increase in F atom concentrations (the latter measured by optical emission spectroscopy) on the addition of O2 is reproduced by a model of the plasma in which gas phase chemical reactions play a dominant role. The increase in CF2 concentration on the addition of H2 to a CF4 plasma is shown to be due to a reduction in the surface removal rate.

Cost-effectiveness of magnetic resonance-guided focused ultrasound surgery for treatment of uterine fibroids

Objective

To estimate the cost-effectiveness of a treatment strategy for symptomatic uterine fibroids, which starts with Magnetic Resonance-guided Focused Ultrasound Surgery (MRgFUS) as compared with current practice comprising uterine artery embolisation, myomectomy and hysterectomy.

Design

Cost-utility analysis based on a Markov model.

Setting

National Health Service (NHS) Trusts in England and Wales.

Population

Women for whom surgical treatment for uterine fibroids is being considered.

Methods

The parameters of the Markov model of the treatment of uterine fibroids are drawn from a series of clinical studies of MRgFUS, and from the clinical effectiveness literature. Health-related quality of life is measured using the 6D. Costs are estimated from the perspective of the NHS. The impact of uncertainty is examined using deterministic and probabilistic sensitivity analysis.

Main outcome measures

Incremental cost-effectiveness measured by cost per quality-adjusted life-year (QALY) gained.

Results

The base-case results imply a cost saving and a small QALY gain per woman as a result of an MRgFUS treatment strategy. The cost per QALY gained is sensitive to cost of MRgFUS relative to other treatments, the age of the woman and the nonperfused volume relative to the total fibroids volume.

Conclusions

A treatment strategy for symptomatic uterine fibroids starting with MRgFUS is likely to be cost-effective.

Please cite this paper as: Zowall H, Cairns J, Brewer C, Lamping D, Gedroyc W, Regan L. Cost-effectiveness of magnetic resonance-guided focused ultrasound surgery for treatment of uterine fibroids. BJOG 2008;115:653–662.

The coxibs and traditional nonsteroidal anti-inflammatory drugs: a current perspective on cardiovascular risks

There is strong evidence from randomized clinical trials that the highly selective cox-2 inhibitors (coxibs), compared with placebo, cause an excess of serious cardiovascular events that are not mitigated by low-dose acetylsalicylic acid. Both Health Canada and the Food and Drug Administration have concluded that the excess cardiovascular events may be a 'class effect' of all the nonsteroidal anti-inflammatory drugs (NSAIDs), including traditional NSAIDs (tNSAIDs) and coxibs, and now require appropriate black box labelling of all these agents. Celecoxib and lumiracoxib are the only coxibs remaining on the market in Canada. The prostanoid pathways, the roles of cox-1 and cox-2, as well as the inhibitory effects of acetylsalicylic acid, traditional tNSAIDs and the coxibs, are briefly reviewed. Current recommendations for the ongoing use of coxibs and the tNSAIDs are summarized.

Inhibitors of mast cell tryptase beta as therapeutics for the treatment of asthma and inflammatory disorders

A survey of the available biological data on tryptase inhibitors suggests that there is considerable interest in tryptase as a therapeutic target particularly for the treatment of allergic asthma and inflammatory disorders. This interest was driven primarily by data from studies carried out on the cellular and in vivo actions of this serine protease over the past decade, all of which have suggested a pro-inflammatory role for tryptase. Tryptase beta is the form of interest in allergic asthma and the data from numerous studies have shown that tryptase cannot only contribute to airway bronchoconstriction and hyperresponsiveness, but may have a key role in fibrosis and ECM turnover, hallmarks of the remodeling process. Hence, inhibitors of tryptase have the potential to make an impact on fibrosis and airway wall remodelling. However, few studies, if any, have been carried out to determine the effect of tryptase inhibitors on airway remodeling and this is an area that warrants further investigation with the appropriate models because the eventual positioning of tryptase inhibitors in asthma therapy will be strengthened by data supporting an impact on airway remodeling in addition to effects on bronchial hyperresponsiveness. This review has focused on tryptase inhibitors in the pipeline and it is clear that with a few exceptions, the majority of these compounds are targeted for inhaled delivery. Finally, judging by the interest from numerous pharmaceutical companies, it appears the stage is set for tryptase inhibitors to make their mark as drugs of the future for allergic asthma and the results from clinical trials is awaited with eager anticipation.

Tryptase and agonists of PAR-2 induce the proliferation of human airway smooth muscle cells

Airway remodeling with smooth muscle cell (SMC) hyperplasia is a feature of chronic asthma. We investigated the potential for tryptase, the major secretory product of human mast cells, to act as a growth factor for human airway SMCs. Because this serine protease can activate proteinase-activated receptor-2 (PAR-2), we also examined the actions of SLIGKV, a peptide agonist of PAR-2. Incubation with lung tryptase provoked a twofold increase in [(3)H]thymidine incorporation; a similar increase in cell numbers was found when we used the MTS assay. The effect was catalytic site dependent, being abolished by the protease inhibitors leupeptin and benzamidine and by heat inactivation of the enzyme. Tryptase-induced DNA synthesis was inhibited by preincubation of the cells with pertussis toxin, calphostin C, or genistein. Transduction mechanisms are thus likely to involve a pertussis toxin-sensitive G protein, protein kinase C, and tyrosine kinase. SLIGKV elicited a response on SMCs similar to that of tryptase. Tryptase could provide an important stimulus for SMC proliferation in asthmatic airways, by acting on PAR-2.

Early asthma prophylaxis, natural history, skeletal development and economy (EASE): a pilot randomised controlled trial

OBJECTIVES

(1) To establish recruitment rates of newly presenting asthmatic children. (2) To establish acceptability of study protocols. (3) To pilot age-specific quality of life (QoL) assessment. (4) To assess short-term (6 months) outcomes of inhaled corticosteroids (ICS) treatment. (5) To refine sample size calculations for a definitive study.

DESIGN

A randomised pragmatic longitudinal trial design was used, with no blinding or placebo, to examine early ICS introduction similar to its use in practice. Subjects were assessed at entry, 3 and 6 months.

SETTING

Subjects were recruited from six general practices. Children under 6 years were assessed at the Craig Research and Investigation Unit, Royal Aberdeen Children's Hospital, or their family home, and subjects 6 years and over were assessed at their general practice.

SUBJECTS

Children (aged 6 months-16 years) with symptoms suggestive of asthma/wheeze that had commenced no longer than 12 months before were identified retrospectively and prospectively from general practices. Subjects were also required to be naïve to prophylactic therapy with no other lung disease/concomitant illness.

INTERVENTIONS

Subjects were randomised to ss2-agonist (ss2-only group) or ss2-agonist and ICS (ICS group) for 6 months. Physicians could later prescribe ICS in controls if needed.

MAIN OUTCOME MEASURES

(1) Pulmonary function. (2) Asthma symptom diary. (3) Symptomatic health status questionnaire. (4) Caregiver's and child's QoL. (5) Growth. (6) Bone mass. (7) Bone turnover. (8) Economic issues.

RESULTS

Of over 15,000 children yielded from general practice records, 11% had symptoms suggestive of asthma/wheeze, and two-thirds of these already used ICS. Of the remaining, 141 subjects met the criterion of early asthma, and 86 were randomised. Two-thirds of those randomised were < 6 years old, the males:females ratio was 2:1, and 67% had a family history of atopy. RESULTS - PHYSIOLOGICAL DEVELOPMENT: Pulmonary function did not significantly improve in the older children. Although tidal breathing measures in the pre-school children were significantly higher at 6 months in the ss2-only group, there was great variability. Incidence of wheeze and night-time cough reduced equally in both groups. Reduction of night-time symptom score and reliever use, and increase in symptom-free days were only significant in the ss2-only group. No significant differences were found in growth and bone mass between the two groups, but bone metabolism was significantly reduced at 6 months in the ICS group. RESULTS - PSYCHOLOGICAL DEVELOPMENT: The caregiver's QoL questionnaire was sensitive to child symptom changes over 3 months, but absolute impact of child symptoms on their QoL varied, whereas the child-centred questionnaire was not sensitive to change. RESULTS - ECONOMICS: There were no significant differences in medical consultation costs between the groups, but, as expected, prescription costs in the ICS group were higher over 6 months. Combined healthcare costs were significantly higher for patients assigned to ICS, but there were no significant differences in any effectiveness measures between the groups.

CONCLUSIONS

Most (96%) of the proposed sample was recruited, and the low drop-out rate (8%) demonstrated acceptability of the study protocol. Most children first presenting with symptoms suggestive of asthma were < 6 years old and represented a group biased towards mild to moderate asthma, or virally induced wheeze. The caregiver's QoL questionnaire was found to better reflect a child's symptom changes than a child-centred instrument. In the short term, no adverse effects were seen on growth, but ICS treatment significantly reduced bone metabolism. Most of the young children with asthma/wheeze improved over time with ss2-agonist treatment alone, and clinical benefits of early ICS intervention amongst these children were not detected; however, there was inadequate power in this pilot study to establish this. (AB

A polymorphic protease-activated receptor 2 (PAR2) displaying reduced sensitivity to trypsin and differential responses to PAR agonists

Protease-activated receptor 2 (PAR2) is a trypsin-activated member of a family of G-protein-coupled PARs. We have identified a polymorphic form of human PAR2 (PAR(2)F240S) characterized by a phenylalanine to serine mutation at residue 240 within extracellular loop 2, with allelic frequencies of 0.916 (Phe(240)) and 0.084 (Ser(240)) for the wild-type and mutant alleles, respectively. Elevations in intracellular calcium were measured in permanently transfected cell lines expressing the receptors. PAR(2)F240S displayed a significant reduction in sensitivity toward trypsin ( approximately 3.7-fold) and the PAR2-activating peptides, SLIGKV-NH(2) ( approximately 2.5-fold) and SLIGRL-NH(2) ( approximately 2.8-fold), but an increased sensitivity toward the selective PAR2 agonist, trans-cinnamoyl-LIGRLO-NH(2) ( approximately 4-fold). Increased sensitivity was also observed toward the selective PAR-1 agonist, TFLLR-NH(2) ( approximately 7-fold), but not to other PAR-1 agonists tested. Furthermore, we found that TLIGRL-NH(2) and a PAR4-derived peptide, trans-cinnamoyl-YPGKF-NH(2), were selective PAR(2)F240S agonists. By introducing the F240S mutation into rat PAR2, we observed shifts in agonist potencies that mirrored the human PAR(2)F240S, suggesting that Phe(240) is involved in determining agonist specificity of PAR2. Finally, differences in receptor signaling were paralleled in a cell growth assay. We suggest that the distinct pharmacological profile induced by this polymorphism will have important implications for the design of PAR-targeted agonists/antagonists and may contribute to, or be predictive of, an inflammatory disease.

Human mast cell tryptase stimulates the release of an IL-8-dependent neutrophil chemotactic activity from human umbilical vein endothelial cells (HUVEC)

Tryptase, the major product of human mast cell activation, is a potent stimulus of vascular leakage and neutrophil accumulation in vivo in animal studies, but the mechanisms of action remain unclear. Using HUVEC cultures we have sought to investigate the potential of tryptase to alter monolayer permeability or induce the release of neutrophil chemotactic activity. Tryptase (1-100 mU/ml) failed to alter the permeability of endothelial cell monolayers as assessed by albumin flux over 1 h. However, supernatants from endothelial cells treated with tryptase (1-50 mU/ml) for a 24-h period induced neutrophil migration across Transwell filters, with maximal migration observed at 10 mU/ml tryptase. Pretreatment of tryptase with the protease inhibitor leupeptin abolished the chemotactic activity, indicating a dependence on the catalytic site. Moreover, this effect was abolished by addition of an IL-8 neutralizing antibody, suggesting that IL-8 release makes an important contribution to the chemotactic activity. The interaction of mast cell tryptase with endothelial cells could be important in stimulating the ingress of neutrophils following mast cell activation in inflammatory disease.

Negative and zero time preference for health

The assumption of positive time preference is seldom challenged in analyses of intertemporal choices, despite considerable evidence of zero and negative discount rates. In this study, the majority of respondents have positive discount rates, but a substantial number have negative or zero discount rates. Using probit regression, the perception of the severity of the health-state, gender, education and perception of the questions in terms of difficulty are shown to influence whether individuals have positive discount rates.

Amiodarone interaction with beta-blockers: analysis of the merged EMIAT (European Myocardial Infarct Amiodarone Trial) and CAMIAT (Canadian Amiodarone Myocardial Infarction Trial) databases. The EMIAT and CAMIAT Investigators

BACKGROUND

Investigations with in vitro and animal models suggest an interaction between amiodarone and beta-blockers. The objective of this work was to explore if an interaction with beta-blocker treatment plays a role in the decrease of cardiac arrhythmic deaths with amiodarone in patients recovered from an acute myocardial infarction.

METHODS AND RESULTS

A pooled database from 2 similar randomized clinical trials, the European Amiodarone Myocardial Infarction Trial (EMIAT) and the Canadian Amiodarone Myocardial Infarction Trial (CAMIAT), was used. Four groups of post-myocardial infarction patients were defined: beta-blockers and amiodarone used, beta-blockers used alone, amiodarone used alone, and neither used. All analyses were done on an intention-to-treat basis. Unadjusted and adjusted relative risks for all-cause mortality, cardiac death, arrhythmic cardiac death, nonarrhythmic cardiac death, arrhythmic death, or resuscitated cardiac arrest were lower for patients receiving beta-blockers and amiodarone than for those without beta-blockers, with or without amiodarone. The interaction was statistically significant for cardiac death and arrhythmic death or resuscitated cardiac arrest (P=0.05 and 0.03, respectively). Findings were consistent across subgroups.

CONCLUSIONS

These findings are based on a post hoc analysis. However, they confirm prior results from in vitro and animal experiments suggesting an interaction between beta-blockers and amiodarone. In practice, not only is the adjunct of amiodarone to beta-blockers not hazardous, but beta-blocker therapy should be continued if possible in patients in whom amiodarone is indicated.

Economic analysis of outreach assessment clinics in breast screening programmes

A model is developed for the economic evaluation of outreach assessment clinics following screening and used to identify the cost-minimizing strategy for assessing women from three island communities in the Scottish Breast Screening Programme (SBSP). There are four options of interest depending on: whether the women are assessed on the mainland or at outreach assessment clinics; and whether all women have two view screening rather than only those being screened for the first time. The benefits of outreach assessment are assumed to be solely in terms of convenience to women and reductions in the time and travel costs of women recalled for assessment. The costs are modelled in order to compare outreach and no outreach options. The results show that for the numbers of women currently screened outreach assessment is the cost-minimizing strategy. The model provides useful guidance with respect to screening policy and is readily applied to the case of outreach assessment in mainland communities outwith major population centres and to breast and other screening programmes in other countries.

Prevention of stroke in patients with nonvalvular atrial fibrillation

OBJECTIVE

To review the risk and pathogenesis of stroke associated with nonvalvular atrial fibrillation (AF) and the efficacies and risks of stroke prevention strategies.

BACKGROUND

About 16% of ischemic strokes are associated with AF; AF is an independent risk factor for stroke.

METHODS

Review of the literature, focusing on 13 randomized trials of antithrombotic therapy.

RESULTS

The overall risk of stroke in AF patients averages about 5%/y, but with wide variation depending on the presence of coexistent thromboembolic risk factors. AF patients with low (about 1% per year), moderate (about 3% per year), and high (about 6% per year) stroke risks have been identified, but the generalizability of risk stratification schemes to clinical practice has not been fully assessed. AF patients with prior stroke or transient ischemic attack, even if remote, are at highest risk (about 12% per year). Adjusted-dose warfarin (target International Normalized Ratio [INR] 2-3) is highly efficacious for preventing stroke in AF patients (about 70% risk reduction) and is safe for selected patients, if carefully monitored. Aspirin has a modest effect on reducing stroke (about 20% risk reduction). The numbers of AF patients that would need to be treated with warfarin instead of aspirin for 1 year to prevent one ischemic stroke are about 200, 70, and 20 for those with low, moderate and high risk, respectively.

CONCLUSIONS

Many patients with nonvalvular AF have substantial rates of ischemic stroke. Stratification of stroke risk identifies AF patients who benefit most and least from lifelong anticoagulation. Warfarin is recommended for high-risk AF patients who can safely receive it. Aspirin may be indicated for those with a low stroke risk and for those who cannot receive warfarin. For AF patients considered to have a moderate risk of stroke, individual bleeding risk during anticoagulation and patient preference should particularly influence the choice of antithrombotic prophylaxis.

Antiarrhythmic therapy in the post-infarction setting: update from major amiodarone studies

Many deaths among hospital survivors of acute myocardial infarction are due to sustained ventricular tachycardia and ventricular fibrillation. This has prompted the evaluation of prophylactic antiarrhythmic drugs and devices. Although it is widely agreed that antiarrhythmic treatment is useful, it is not certain which therapy provides optimal results. Increasing recognition of the efficacy of amiodarone has prompted the design of several trials of the drug. This paper focuses on primary prophylactic antiarrythmic therapy in the post-infarction setting and particularly on recent amiodarone trials.

The role of mast cell tryptase in regulating endothelial cell proliferation, cytokine release, and adhesion molecule expression: tryptase induces expression of mRNA for IL-1 beta and IL-8 and stimulates the selective release of IL-8 from human umbilical vein endothelial cells

Mast cells are found frequently in close proximity to blood vessels, and endothelial cells are likely to be exposed to high concentrations of their granule mediators. We have investigated the proinflammatory actions of the major mast cell product tryptase on HUVEC. Addition of purified tryptase was found to stimulate thymidine incorporation, but induced little alteration in cell numbers, suggesting it is not a growth factor for HUVEC. Expression of ICAM-1, VCAM-1, and E-selectin was not altered following incubation with tryptase, but the potent granulocyte chemoattractant IL-8 was released in a dose-dependent fashion in response to physiologically relevant concentrations, with maximal levels in supernatants after 24 h. The actions of tryptase on HUVEC were inhibited by heat inactivation of the enzyme, or by preincubating with the protease inhibitors leupeptin or benzamidine, suggesting a requirement for an intact catalytic site. Reverse-transcription PCR analysis indicated up-regulation of mRNA for IL-8 as well as for IL-1 beta in response to tryptase or TNF-alpha. However, tryptase was a more selective stimulus than TNF-alpha and did not induce increased expression of mRNA for granulocyte-macrophage CSF or stimulate the release of this cytokine. Leukocyte accumulation in response to tryptase may be mediated in part through the selective secretion of IL-8 from endothelial cells.

The efficient organization of blood donation

This paper models the costs of collecting whole blood in the north of Scotland in order to investigate strategies whereby the annual collection target can be met at lower cost. Data on the costs of the individual sessions held in 1993-1995 are analyzed using multilevel analysis. A new technique, namely the conditioned iterative generalized least squares (CIGLS) estimator is applied. Then the feasibility of collecting increased volumes from particular panels and areas is assessed by examining which factors determine the number of blood donors at a session. Results show that fixed cost and marginal cost vary across panels but marginal cost does not vary by volume. This implies that the cost-minimizing policy is to equalize marginal costs and collect higher volume at fewer panels (those with lower fixed costs). The level of donations can be increased by increasing the number of opportunities to donate and/or increasing the average length of a session. The latter policy is shown to be more cost-effective. Multilevel analysis proves not only to be appropriate but also particularly useful.

When is the 'right' time to initiate an assessment of a health technology?

There is currently no generally accepted formula for the optimal timing of health technology assessments (HTAs). This paper presents some of the relevant issues and then reviews the existing literature on timing of HTAs. It finds that the literature that specifically addresses these issues is limited. There is a consensus that HTAs should be initiated at an early stage of the development of a new health technology, and repeated during the life cycle of the technology. However, the questions of reliably identifying new technologies at an early stage in their development and of deciding on a detectable critical point for starting evaluation are not resolved. It is proposed that a system of categorization and prioritization of health technologies should be developed to allow decisions to be made as to when a strongly precautionary approach is required and how the limited resources available for HTA could be optimally deployed.

When and how to assess fast-changing technologies: a comparative study of medical applications of four generic technologies

OBJECTIVES. To try to identify the optimal time at which to start assessing new and fast-evolving health technologies. To provide insight into factors influencing the timing of assessments and the choice of methods for assessing new and fast-changing technologies. HOW THE RESEARCH WAS CONDUCTED. A series of literature reviews were undertaken covering the general principles involved in the timing of health technology assessments (HTAs). Additionally, the reported assessments of laparoscopic cholecystectomy, chorionic villus sampling (CVS), teleradiology, teledermatology, genetic screening for predisposition to breast cancer, and gene therapy for cystic fibrosis were reviewed to try to identify the factors that influenced the timing of these assessments. Key individuals in each field were also interviewed. The selected technologies allowed comparison between those that were new and evolving and those that were relatively well-established. A bibliometric study of publication trends was also undertaken to see whether these trends would suggest points in the development of a technology that could be used as indicators that assessment should be started. RESEARCH FINDINGS. TIMING. The precise point at which assessment should start was not identified but the bibliometric study suggested that extending this approach might give useful results. For all health technologies, more regular reporting of outcomes and side-effects should be encouraged during the period after initial assessment and, where the technology is fast-changing, reassessment should take place from time to time. The precise intervals were not identified and the problem remains of deciding when a technology has changed enough to warrant reassessment. FACTORS INFLUENCING TIMING. Published reports of assessments did not generally specify the reasons for their timing, but a number of factors appear to have influenced the timing of those assessments, directly or indirectly. Product champions and opinion leaders pioneer the introduction of new technologies into clinical practice, and their reports may lead to the rapid diffusion of such technologies before they have been adequately evaluated, as was the case with laparoscopic cholecystectomy; this diffusion may limit the methods of evaluation that can then be used. It is therefore important to assess new health technologies before diffusion takes place. The extent to which regulatory control is imposed on the introduction of new health technologies can also influence the timing of assessments. Such controls might have helped to restrict the diffusion of laparoscopic cholecystectomy, making a large and widely generalisable randomised controlled trial (RCT) feasible. The source and availability of funding for studies may influence the nature and timing of trials. Many telemedicine evaluations were funded by commercial telecommunications organisations and were thus restricted in their timing (and biased towards the technological aspects of the applications) by the availability of funds. Media coverage undoubtedly has an influence although this influence is not always predictable; it may generate 'favourable' publicity about new health technologies, which can lead to immediate demands for the new technique, as was the case with laparosocpic cholecystectomy with its apparent benefits. Thus assessments should be made before media coverage exerts popular pressure on purchasers to adopt the technology and dissuades patients from participating in RCTs (because of fear they may be randomised to the standard treatment as occurred in a US trial of CVS). Innovators should also be cautious in the claims that they make to the media.(ABSTRACT TRUNCATED)

Saving future lives. A comparison of three discounting models

This paper compares three models of intertemporal choice concerning saving future lives: the constant discounting model, the proportional discounting model and the hyperbolic discounting model. The three models were investigated using data collected from the general public. Since these data have a multilevel structure, ordinary least-squares (OLS) estimates were supplemented by multilevel analysis. There is evidence in favour of the proportional (and to a lesser extent) the hyperbolic model over the constant discounting model. There is clear evidence for this data set that multilevel analysis is more appropriate than OLS.

Mast cell tryptase stimulates the synthesis of type I collagen in human lung fibroblasts

Mast cell activation is a characteristic feature of chronic inflammation, a condition that may lead to fibrosis as a result of increased collagen synthesis by fibroblasts. We have investigated the potential of tryptase, the major protease of human mast cells, to stimulate collagen synthesis in the human lung fibroblast cell line MRC-5. Tryptase was isolated from human lung tissue by ion-exchange and affinity chromatography. At concentrations of 18 and 36 mU/ml, tryptase stimulated both an increase in cell numbers, and a fivefold increase in DNA synthesis as determined by methyl-[3H]thymidine incorporation. Similar concentrations of tryptase resulted in a 2.5-fold increase in collagen synthesis as determined both by incorporation of [3H]proline into collagen, and by assay of hydroxyproline concentrations in the supernatants. There was also a twofold increase in collagenolytic activity in the culture medium after tryptase treatment, indicating that the increase in collagen synthesis was not a consequence of decreased collagenase production. All of these actions of tryptase were reduced in the presence of the protease inhibitors leupeptin and benzamidine hydrochloride, indicating a requirement for an active catalytic site. SDS-PAGE and autoradiographic analysis of the [3H]collagen produced by the cells revealed it to be predominantly type I collagen. Our findings suggest that the release of tryptase from activated mast cells may provide a signal for abnormal fibrosis in inflammatory disease.

Randomised trial of outcome after myocardial infarction in patients with frequent or repetitive ventricular premature depolarisations: CAMIAT. Canadian Amiodarone Myocardial Infarction Arrhythmia Trial Investigators

BACKGROUND

Survivors of acute myocardial infarction with frequent or repetitive ventricular premature depolarisations (VPDs) have higher mortality 1-2 years after the event than those without VPDs. Although there is no therapy of proven efficacy for such patients, previous studies of amiodarone have been encouraging. CAMIAT was a randomised double-blind placebo-controlled trial designed to assess the effect of amiodarone on the risk of resuscitated ventricular fibrillation or arrhythmic death among survivors of myocardial infarction with frequent or repetitive VPDs (> or = 10 VPDs per h or > or = 1 run of ventricular tachycardia).

METHODS

Patients from 36 Canadian hospitals were randomly assigned amiodarone or placebo; a loading dose of 10 mg/kg daily for 2 weeks, a maintenance dose of 300-400 mg daily for 3.5 months, 200-300 mg daily for 4 months, and 200 mg for 5-7 days per week for 16 months. Patients were followed up for 2 years. The primary outcome was the composite of resuscitated ventricular fibrillation or arrhythmic death.

FINDINGS

We recruited 1202 patients (606 in the amiodarone group and 596 in the placebo group). The mean follow-up was 1.79 years (SD 0.44). In the efficacy analysis, resuscitated ventricular fibrillation or arrhythmic death occurred in 39 (6.9%) [corrected] patients in the placebo group and in 25 (4.5%) [corrected] in the amiodarone group (relative-risk reduction 48.5% [95% CI 4.5 to 72.2], p = 0.016). In the intention-to-treat analysis, primary outcome events occurred in 24 (6.9%) patients in the placebo group and in 15 (4.5%) in the amiodarone group (38.2% [95% CI -2.1 to 62.6], p = 0.029). The absolute-risk reductions were greatest among patients with congestive heart failure or a history of myocardial infarction.

INTERPRETATION

Amiodarone reduces the incidence of ventricular fibrillation or arrhythmic death among survivors of acute myocardial infarction with frequent or repetitive VPDs. Treatment decisions for individual survivors should require an assessment of their baseline risk factors and judgments based on the synthesis of our findings with those of related trials.

Angiotensin-converting enzyme inhibition in myocardial infarction--Part 1: Clinical data

There is an increasing body of clinical trial evidence to support the use of angiotensin-converting enzyme (ACE) inhibitors in the management of patients following myocardial infarction (MI). Enthusiasm for the use of ACE inhibitors in the acute phase of MI had previously been tempered by the adverse results of an early trial. However, exciting new information is available from several large, randomized studies that has not only quelled those initial concerns but also attests to the efficacy of using this class of medication in the first 24 h after an acute MI. A Canadian National Opinion Leader Symposium was held in November 1995 to review the results of the major ACE inhibitor clinical trials and to discuss key issues and controversies surrounding their use in acute MI. The focus of this paper, the first of two parts, is on the results of the major ACE inhibitor clinical trials.

Comparison of mortality from acute myocardial infarction between 1979 and 1992 in a geographically defined stable population

This study documents mortality from acute myocardial infarction (AMI), in hospital and at 1 year, for each of 3 selected 1-year periods in a stable community over a 13-year period beginning in 1979 and continuing into the thrombolytic era, to detect any changes occurring in conjunction with the introduction of new therapies. Every patient with AMI occurring in a geographically defined stable community (Hamilton, Ontario, Canada) in 3 1-year periods (1979 to 1980 [n = 816], 1986 to 1987 [n = 816], and 1991 to 1992 [n = 831]) was identified and clinically characterized by standardized criteria. Subsequent in-hospital and 1-year survival were ascertained prospectively. The 3 cohorts were similar in prognostic factors. Mean age was progressively greater over the study period from 63 years in 1979 to 1980, to 67 years in 1991 to 1992 (p = 0.02). There was no change in in-hospital mortality rates from 1979 to 1980 (17%) and 1986 to 1987 (16%). However, from 1986 to 1987 and 1991 to 1992, in-hospital mortality decreased from 16% to 9% (p < 0.001) and 1-year mortality decreased from 26% to 19% (p < 0.001). For patients who survived the hospital phase of AMI, 1-year mortality did not change and was between 11% and 12% in each of the 3 study periods. From 1986 to 1987 and 1991 to 1992, there was an increase in the use of thrombolytic therapy from 5% to 44% of patients. The acute use of aspirin increased from 30% to 88% and the acute use of beta blockers increased from 19% to 48% of patients. The observed increase in use of these agents could account for half of the actual mortality reduction observed. This prospective population-based survey demonstrates improved in-hospital survival after AMI associated with increased use of established effective therapies between 1987 and 1992. The 1-year mortality of hospital survivors of AMI was unchanged throughout the period of study, remaining at 11% to 12%.

Fish oils and low-molecular-weight heparin for the reduction of restenosis after percutaneous transluminal coronary angioplasty. The EMPAR Study

BACKGROUND

Percutaneous transluminal coronary angioplasty (PTCA) is complicated by restenosis within 6 months in > 40% of patients. Theoretical, animal experimental, and human epidemiological and clinical trial findings have suggested that fish oils (n-3) might reduce restenosis. Low-molecular-weight heparin (LMWH) has reduced cellular proliferation and restenosis in several experimental systems.

METHODS AND RESULTS

We randomized 814 patients to fish oils (5.4 g n-3 fatty acids) or placebo a median of 6 days before PTCA and continued for 18 weeks. At the time of sheath removal, 653 patients with at least one successfully dilated lesion were randomized to LMWH (30 mg SC BID) or control for 6 weeks in a 2 x 2 factorial design. Follow-up with quantitative coronary angiography (QCA; target, 18 weeks) was interpretable on 96% of these patients. Restenosis rates per patient were for n-3, 46.5%; placebo, 44.7%; LMWH, 45.8%; and control, 45.4%. Restenosis rates per lesion were for n-3, 39.7%; placebo, 38.7%; LMWH, 38%; and control, 40.4%. At follow-up QCA, mean minimal lumen diameters were (mm) for n-3, 1.12; placebo, 1.10; LMWH, 1.12; and control, 1.10. Fifteen percent of patients permanently discontinued n-3/placebo before study completion, and 21% of patients discontinued LMWH early. There were no significant differences in the occurrences of ischemic events. Bleeding was more common with LMWH, usually was mild, and led to early discontinuation of study medication in only 0.9% of patients. Gastrointestinal side effects were more common in patients receiving n-3 than placebo.

CONCLUSIONS

There is no evidence for a clinically important reduction of PTCA restenosis in this trial by either n-3 or LMWH. Evaluation of the results for n-3 in the context of previously published data on the reduction of PTCA restenosis indicates that n-3 is not efficacious and that further trials are unwarranted.

The acute coronary ischemic syndromes--the central role of thrombosis

The postulate that thrombotic coronary occlusion was the underlying pathophysiologic event in the acute coronary ischemic syndromes was developed over the years 1912-60. This concept prompted the development of anticoagulant and thrombolytic therapies and the use of acetylsalicylic acid in such patients. A central role for coronary thrombus came to be questioned in the 1970s and the use of anticoagulants dramatically decreased and thrombolytic therapy was little used. Coronary angiographic studies among patients during the early hours of evolving myocardial infarction re-established the etiologic role of coronary thrombosis in the acute coronary ischemic syndromes, and were supplemented by careful autopsy studies. The concepts of meta-analysis lead to more accurate interpretations of earlier randomized, controlled trials of anticoagulant, antiplatelet and thrombolytic therapies. Large clinical trials have provided confirmatory evidence and have established the benefits of antiplatelet and thrombolytic agents in the acute ischemic syndromes. The benefit of long term anticoagulation following myocardial infarction has been demonstrated, although the benefit during the acute in-hospital phase of myocardial infarction is still uncertain. Currently, clinical trials are evaluating new antithrombins, antiplatelet agents, and thrombolytic agents and regimens among patients with unstable angina, acute myocardial infarction, and undergoing angioplasty for complex coronary lesions.

Prognostic importance of myocardial ischemia detected by ambulatory monitoring early after acute myocardial infarction

BACKGROUND

After an acute myocardial infarction, it is important to determine the risk of a subsequent coronary event. We studied the prognostic value of myocardial ischemia detected by ambulatory electrocardiographic (ECG) monitoring in patients who had recently had an acute myocardial infarction.

METHODS

Five to seven days after acute myocardial infarction, 406 patients underwent 48-hour ambulatory ECG monitoring, with submaximal exercise testing before discharge and measurement of the left ventricular ejection fraction within 28 days after infarction. Death, nonfatal myocardial infarction, and admission to the hospital because of unstable angina were the principal end points recorded during the one-year follow-up period.

RESULTS

The overall incidence of myocardial ischemia detected by ambulatory ECG monitoring was 23.4 percent. The mortality rates at one year were 11.6 percent among the patients with ischemia and 3.9 percent among those without ischemia (P = 0.009); 3.9 percent among the patients with a positive exercise test, 3.0 percent among those with a negative exercise test, and 16.4 percent among those in whom an exercise test was not performed (P < 0.001); and 3.6 percent among the patients with an ejection fraction greater than 50 percent, 3.5 percent among those with an ejection fraction between 35 and 50 percent, and 18.2 percent among those with an ejection fraction below 35 percent (P = 0.001). Using multiple logistic regression, we found that no diagnostic test performed after myocardial infarction provided additional prognostic information beyond that provided by the standard clinical variables used to predict the risk of death. When nonfatal myocardial infarction and admission to the hospital because of unstable angina were also included as outcome variables, ambulatory monitoring for ischemia was the only test that contributed significantly to the model. For the patients with ischemia detected by ambulatory monitoring, as compared with those who did not have evidence of ischemia, the odds ratio was 2.3 (95 percent confidence interval, 1.2 to 4.5) for death or nonfatal myocardial infarction (P = 0.009) and 2.8 (95 percent confidence interval, 1.6 to 4.8) for death, nonfatal myocardial infarction, or admission to the hospital because of unstable angina (P < 0.001).

CONCLUSIONS

Myocardial ischemia detected by ambulatory ECG monitoring is common early after acute myocardial infarction and provides prognostic information beyond that available from standard clinical information.

Mast cell tryptase is a mitogen for epithelial cells. Stimulation of IL-8 production and intercellular adhesion molecule-1 expression

Tryptase, a protease unique to the mast cell secretory granule, is released in substantial quantities into the respiratory tract of patients with inflammatory disease of the airways. We have investigated the potential of tryptase to act as a mitogen for bronchial epithelial cells and to stimulate release of IL-8 and expression of ICAM-1. Tryptase was isolated from extracts of human lung tissue using ammonium sulphate precipitation, octyl agarose, and heparin agarose chromatography. Purified tryptase stimulated DNA synthesis in the human epithelial cell line H292, as measured by [3H] thymidine incorporation. Maximal growth was observed after 24 h using 25 mU/ml of tryptase (where 1 micron is defined as that which can hydrolyze 1 mumol of the peptide substrate N-alpha-benzoyl-DL-arginine p-nitroanilide hydrochloride per minute at 25 degrees C), a concentration that is likely to be achieved in vivo. Inhibitors of tryptase activity, including leupeptin and benzamidine hydrochloride, significantly decreased tryptase-induced stimulation of DNA synthesis, indicating the requirement for an active catalytic site. Tryptase stimulated a catalytic site-dependent release of IL-8 from epithelial cells after 24 h, and this was associated with up-regulation of ICAM-1 expression, as revealed by FACS analysis. Tryptase may play a critical role in epithelial repair and in the recruitment of granulocytes following mast cell activation.

Mast cell tryptase is a mitogen for epithelial cells. Stimulation of IL-8 production and intercellular adhesion molecule-1 expression

Tryptase, a protease unique to the mast cell secretory granule, is released in substantial quantities into the respiratory tract of patients with inflammatory disease of the airways. We have investigated the potential of tryptase to act as a mitogen for bronchial epithelial cells and to stimulate release of IL-8 and expression of ICAM-1. Tryptase was isolated from extracts of human lung tissue using ammonium sulphate precipitation, octyl agarose, and heparin agarose chromatography. Purified tryptase stimulated DNA synthesis in the human epithelial cell line H292, as measured by [3H] thymidine incorporation. Maximal growth was observed after 24 h using 25 mU/ml of tryptase (where 1 micron is defined as that which can hydrolyze 1 mumol of the peptide substrate N-alpha-benzoyl-DL-arginine p-nitroanilide hydrochloride per minute at 25 degrees C), a concentration that is likely to be achieved in vivo. Inhibitors of tryptase activity, including leupeptin and benzamidine hydrochloride, significantly decreased tryptase-induced stimulation of DNA synthesis, indicating the requirement for an active catalytic site. Tryptase stimulated a catalytic site-dependent release of IL-8 from epithelial cells after 24 h, and this was associated with up-regulation of ICAM-1 expression, as revealed by FACS analysis. Tryptase may play a critical role in epithelial repair and in the recruitment of granulocytes following mast cell activation.