Comparison of double bolus urokinase versus front-loaded alteplase regimen for acute myocardial infarction. Thrombolysis in Myocardial Infarction in Korea (TIMIKO) study group

The recanalization after thrombolysis as surrogate for clinical outcomes in patients with ST-segment elevation acute myocardial infarction: A systematic review and meta-regression analysis of data from randomized controlled trials

AIMS

Thrombolytic therapy has been known to be effective in reducing clinical outcomes and increasing recanalization rate among patients with ST-segment elevation acute myocardial infarction (STEMI). However, whether post-thrombolysis recanalization could be used as a surrogate for clinical outcomes is unknown.

METHODS

We systematically searched PubMed, EMBASE and the Cochrane Library database to identify randomized controlled trials (RCT) that examined effects of thrombolytic agents in STEMI. Recanalization was defined as TIMI grade 2 or 3 flow. The primary outcome was in-hospital all-cause mortality. Secondary outcomes included in-hospital and 30-day recurrent myocardial infarction (re-MI), composite of death and re-MI, major bleeding and all bleeding. Random-effects meta-regression was used for analysis.

RESULTS

We identified 111 eligible study arms and 52 eligible comparisons from 58 RCTs involving 16 536 patients. Our analyses showed that among study arms recanalization rate was significantly inversely associated with the incidence of in-hospital all-cause mortality (β: -0.07, 95% confidence interval [CI]: -0.13 to -0.02), re-MI (β: -0.09, 95%CI: -0.18 to -0.01) and the composite of death and re-MI (β: -0.17, 95%CI: -0.28 to -0.05), and positively associated with in-hospital all bleeding but not with major bleeding. Among paired comparisons, the difference in recanalization rate was associated with the corresponding difference in incidence of in-hospital all-cause mortality (β: -0.15, 95%CI: -0.28 to -0.01) but the relationship was not significant for any other outcome.

CONCLUSION

Pooled evidence from RCTs suggest the potential use of recanalization as a surrogate for clinical outcomes in evaluating the efficacy of thrombolysis among patients with STEMI.

Meta-analysis of randomized phase II trials to inform subsequent phase III decisions

BACKGROUND

If multiple Phase II randomized trials exist then meta-analysis is favorable to increase statistical power and summarize the existing evidence about an intervention's effect in order to help inform Phase III decisions. We consider some statistical issues for meta-analysis of Phase II trials for this purpose, as motivated by a real example involving nine Phase II trials of bolus thrombolytic therapy in acute myocardial infarction with binary outcomes.

METHODS

We propose that a Bayesian random effects logistic regression model is most suitable as it models the binomial distribution of the data, helps avoid continuity corrections, accounts for between-trial heterogeneity, and incorporates parameter uncertainty when making inferences. The model also allows predictions that inform Phase III decisions, and we show how to derive: (i) the probability that the intervention will be truly beneficial in a new trial, and (ii) the probability that, in a new trial with a given sample size, the 95% credible interval for the odds ratio will be entirely in favor of the intervention. As Phase II trials are potentially optimistic due to bias in design and reporting, we also discuss how skeptical prior distributions can reduce this optimism to make more realistic predictions.

RESULTS

In the example, the model identifies heterogeneity in intervention effect missed by an I-squared of 0%. Prediction intervals accounting for this heterogeneity are shown to support subsequent Phase III trials. The probability of success in Phase III trials increases as the sample size increases, up to 0.82 for intracranial hemorrhage and 0.79 for reinfarction outcomes.

CONCLUSIONS

The choice of meta-analysis methods can influence the decision about whether a trial should proceed to Phase III and thus need to be clearly documented and investigated whenever a Phase II meta-analysis is performed.

Thrombolysis for restoration of patency to haemodialysis central venous catheters: a systematic review

Urokinase, previously used to restore patency to thrombosed haemodialysis catheters, is now unavailable in North America. We performed systematic reviews of four questions related to the safety and efficacy of alternative agents for catheter thrombolysis, searching Medline and the Cochrane Controlled Clinical Trials Register. In dialysis patients, large case series have documented that urokinase is safe and effective (>70 % efficacy for catheter instillation, and >80 % for systemic lysis). Experience with streptokinase is limited and allergic complications develop with repeated use. Studies of catheter instillation with 1--2 mg of tPA per lumen reported short-term success in 83--98 % of uses. One non-peer-reviewed study described 44--59 % success using systemic tissue plasminogen activator (tPA), 2.5 mg through each of 2 lumens, over 1 h. Meta-analysis of randomized comparisons of urokinase and tPA as full-dose thrombolytic agents suggested that 1 mg tPA was likely equivalent in thrombolytic potency to 36,000 units urokinase. In nondialysis populations, four case series suggested that catheter instillation with 0.5--2 mg tPA was effective and safe in reestablishing patency, and a randomized controlled trial found 2--4 mg tPA more effective than 5,000--10,000 units urokinase. No complications have been reported in any patient treated with systemic or local tPA for catheter thrombolysis. In studies of fistula thrombolysis with 5--50 mg tPA major complications occurred in one episode in 130 patients treated. This review suggests that 1--2 mg/lumen tPA is a suitable dose for catheter instillation and likely to be more effective than 5000 units/lumen urokinase. Systemic lysis with 5--10 mg tPA is likely to be safe and effective in suitably selected patients. Further studies are needed.

Risk of intracranial haemorrhage with bolus versus infusion thrombolytic therapy: a meta-analysis

BACKGROUND

Although thrombolytic therapy given by bolus injection seems to be as effective as infusion over 60-90 min, no single trial has been adequately powered to detect clinically important safety differences between the two strategies. We did a meta-analysis to find out whether bolus administration of thrombolytics is associated with an increased frequency of intracranial haemorrhage.

METHODS

We identified randomised trials comparing bolus with infusion thrombolytic therapy by a search of electronic databases, reference lists, and conference proceedings. Odds ratios for primary intracranial haemorrhage, non-haemorrhagic stroke, mortality, and reinfarction were calculated for each trial and were combined in a fixed-effects model.

FINDINGS

Seven trials, involving a total of 103,972 patients, met our inclusion criteria. Bolus treatment was associated with an increased risk of intracranial haemorrhage compared with infusion (0.8 vs 0.6%; odds ratio 1.25 [95% CI 1.08-1.45]; p=0.003). The increased risk was most striking in trials comparing bolus with infusion administration of the same agent (1.75 [1.32-2.33], p=0.0001), but was also evident in trials comparing a newer-generation bolus agent with standard infusion therapy (1.25 [1.03-1.50]; p=0.02). The rates of non-haemorrhagic stroke (0.94 [0.81-1.09]), 30-day mortality (1.01 [0.97-1.06]), or reinfarction (1.04 [0.97-1.11]) did not differ between the two strategies.

INTERPRETATION

The increased risk of bolus thrombolytic treatment seems to be primarily associated with the method of administration rather than properties of the agents. Although the increased risk of intracranial haemorrhage is small, physicians should balance this risk against the putative benefits of easier administration with no difference in mortality or reinfarction.