Comparative case fatality analysis of the International Tissue Plasminogen Activator/Streptokinase Mortality Trial: variation by country beyond predictive profile. The Investigators of the International Tissue Plasminogen Activator/Streptokinase Mortality Trial

Adverse event rates following primary PCI for STEMI at US and non-US hospitals: three-year analysis from the HORIZONS-AMI trial

AIMS

To examine outcomes in patients with ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI) at US sites versus sites outside the US (OUS).

METHODS AND RESULTS

In the HORIZONS-AMI trial 3,602 STEMI patients in 11 countries were randomised to primary PCI with bivalirudin versus heparin + glycoprotein IIb/IIIa inhibitors. US patients (n=814) had more diabetes, prior infarction, prior bypass surgery, and renal insufficiency. OUS patients (n=2,788) had longer door-to-balloon times, more radial access, fewer bypass surgeries, and were discharged more often on beta-blockers and statins. At three years US patients had higher mortality (9.7% vs. 6.0%, p=0.0003), reinfarction (10.2% vs. 6.4%, p=0.001), major adverse cardiac events (MACE; 28.2% vs. 20.1%, p<0.0001), major bleeding (16.9% vs. 6.4%, p<0.0001) and net adverse clinical events (NACE; 36.6% vs. 23.8%, p<0.0001), which persisted after adjusting for baseline risk.

CONCLUSIONS

In the HORIZONS-AMI trial, STEMI patients undergoing primary PCI at US versus OUS sites had higher rates of adverse events, which persisted after adjusting for baseline risk. The reasons for these differences are not clear but may be due to unmeasured confounders, different thresholds for event reporting, or valid differences in systems of care and treatments.

Implications of geographical variation on clinical outcomes of cardiovascular trials

Cardiovascular clinical trials are increasingly conducted globally as a means to reduce costs, expedite timelines, provide broad applicability, and satisfy regulatory authorities. Potential problems with trial globalization include regional differences in patient characteristics, medical practice patterns, and health policies which may influence outcomes and limit generalizability. Moreover, concerns have been raised about ethical misconduct and unsatisfactory quality oversight in regions with less trial experience and infrastructure. This article reviews geographical differences in cardiovascular trials in heart failure, acute coronary syndromes, hypertension and atrial fibrillation. It also explores potential explanations for these differences and methods to standardize the presentation of trial results. This review is based on discussions between basic scientists and clinical trialists at the 8th Global Cardio Vascular Clinical Trialists Forum 2011 in Paris, France, from December 2 to 3.

Safety and efficacy of prasugrel compared with clopidogrel in different regions of the world

BACKGROUND

Among patients with acute coronary syndrome (ACS), demographics, procedural characteristics and adjunctive medications differ globally. We examined whether there were differential effects of prasugrel compared with clopidogrel in the multinational TRITON-TIMI 38 study.

METHODS

We divided the enrollment into 5 pre-specified geographic regions. Patients were randomized to prasugrel or clopidogrel without regard to country of enrollment. End points are expressed as Kaplan-Meier failure estimates through 15 months. Heterogeneity was evaluated using Cox proportional hazards model. Additional sensitivity analyses were performed by dividing countries into categories based on the Human Development Index (HDI), which is a composite measure of social and economic development.

RESULTS

13,608 patients were enrolled. Clinical characteristics including age, comorbidities, ACS presentation, stent types, and adjunctive medications differed broadly among regions. Despite these differences, no regional heterogeneity was observed with prasugrel compared to clopidogrel in the reduction of ischemic events (HR range: 0.76-0.87, p(interaction)>0.10 for each) and stent thrombosis (HR range: 0.34-0.72, p(interaction)>0.10 for each) or in the increased rate of non-CABG TIMI major bleeding (HR range: 1.16-1.76, p(interaction)>0.10 for each). There was a consistent trend in net clinical benefit (all cause death/MI/stroke/non-CABG TIMI major bleeding) favoring prasugrel (HR range: 0.81-0.97, p(interaction)>0.10 for each). Consistent results were also observed regarding the safety and efficacy of prasugrel compared with clopidogrel in both developed and developing countries.

CONCLUSIONS

Despite differences in patient demographics, procedural techniques and adjunctive medications, consistent reduction in ischemic events and increased bleeding were seen with prasugrel compared with clopidogrel throughout the world.

Unexplained international differences in clinical outcomes after acute myocardial infarction and fibrinolytic therapy: lessons from the Hirulog and Early Reperfusion or Occlusion (HERO)-2 trial

BACKGROUND

Despite advances in therapy, global mortality due to acute myocardial infarction remains high. The international Hirulog and Early Reperfusion or Occlusion (HERO-2) trial of 17,073 patients with ST-segment elevation myocardial infarction provided the opportunity to explore international differences in outcomes.

METHODS

Patient characteristics, treatment, and outcomes were compared across 5 diverse regions: Western countries, Latin America, Eastern Europe, Russia, and Asia. In addition, a representative sample of 1,743 screened patients was compared with enrolled patients.

RESULTS

Larger percentages of eligible patients were randomized in Eastern Europe, Russia, and Asia than Western countries. These regions enrolled more patients with anterior myocardial infarction, Killip class III or IV, and late presentation (>4 hours). More patients aged >75 years were enrolled from Western countries. Overall risk levels were similar. Eastern Europe and Russia had lower rates than Western countries of coronary revascularization (2% vs 18%) and longer hospital stays (median 18 vs 7 days). Thirty-day mortality was lower in Western countries; 6.7% versus 10.2% to 13.2% elsewhere, whereas reinfarction was more frequent (3.2% vs 1.5% to 3.0%; each, P < .001). Regional mortality differences persisted after adjustment for baseline risk factors, treatments, or national health and economic statistics (each P < .001).

CONCLUSIONS

The variation in mortality and other clinical outcomes across geographic regions was not adequately explained by risk factors, patterns of care, or national health statistics. Nevertheless, large international trials are a better way to assess potential new treatments across many countries than the alternative of separate smaller trials in each region.

Optimizing use of revascularization and clinical outcomes in ST-elevation myocardial infarction: insights from the GUSTO-V trial

AIMS

To examine the relationship between revascularization within 7 days and 1-year mortality among ST-elevation myocardial infarction patients enrolled in GUSTO-V trial (n=13 451). To examine the relative contribution of system and patient level factors to the variation in international revascularization rates, and their impact on mortality outcomes.

METHODS AND RESULTS

Patients from North America (USA, Canada), Australia, and Europe (UK, France, Germany, Italy, Spain, Poland, Norway, The Netherlands, Belgium, Finland) were included in the study. Revascularization was associated with lower 1-year mortality. Norway, Belgium, Spain, Poland, and Italy also had lower than expected revascularization rates but higher than expected mortality rates. France and USA had almost two times the expected rate of 7-day revascularization, which was associated with modest mortality benefits. Patients' propensity for revascularization based on clinical factors alone was associated with lower 1-year mortality (OR 0.97, 95% CI: 0.96-0.99). Country-level factors had an impact on propensity for revascularization but no impact on 1-year mortality.

CONCLUSION

Our study reveals the potential for some countries with lower than expected 7-day revascularization rates to improve their clinical outcomes. Also highlighted is the possibility for more economically efficient delivery of care in USA and France.

'Lost in translation': accounting for between-country differences in the analysis of multinational cost-effectiveness data

Cost-effectiveness analysis has gained status over the last 15 years as an important tool for assisting resource allocation decisions in a budget-limited environment such as healthcare. Randomised (multicentre) multinational controlled trials are often the main vehicle for collecting primary patient-level information on resource use, cost and clinical effectiveness associated with alternative treatment strategies. However, trial-wide cost effectiveness results may not be directly applicable to any one of the countries that participate in a multinational trial, requiring some form of additional modelling to customise the results to the country of interest. This article proposes an algorithm to assist with the choice of the appropriate analytical strategy when facing the task of adapting the study results from one country to another. The algorithm considers different scenarios characterised by: (a) whether the country of interest participated in the trial; and (b) whether individual patient-level data (IPD) from the trial are available. The analytical options available range from the use of regression-based techniques to the application of decision-analytic models. Decision models are typically used when the evidence base is available exclusively in summary format whereas regression-based methods are used mainly when the country of interest actively recruited patients into the trial and there is access to IPD (or at least country-specific summary data). Whichever method is used to reflect between-country variability in cost-effectiveness data, it is important to be transparent regarding the assumptions made in the analysis and (where possible) assess their impact on the study results.

Are international differences in the outcomes of acute coronary syndromes apparent or real? A multilevel analysis

STUDY OBJECTIVE

International variation in the outcomes of patients with acute coronary syndromes (ACS) has been well reported. The relative contributions of patient, hospital, and country level factors on clinical outcomes, however, remain unclear, and thus, was the objective of this study.

DESIGN

Multilevel logistic regression models were developed for death/(re)infarction (MI) at 30 days and death in one year, with patients (1st level) nested in hospitals (2nd level) and hospitals in countries (3rd level).

SETTINGS

The GUSTO IV ACS clinical trial was carried out at 458 hospital sites in 24 countries.

PATIENTS

7800 non-ST segment elevation (NSTE) ACS patients.

MAIN RESULTS

There were substantial variations among countries in the processes and outcomes of care at 30 days, ranging from 5.4% to 50.0% for percutaneous coronary intervention, 4.3% to 21.2% for coronary artery bypass graft surgery, 5.0% to 13.9% for 30 day death/(re)MI, and 4.9% to 14.8% for one year mortality. However, the residual inter-country variations in 30 day death/(re)MI and one year mortality became non-significant and nearly disappeared (p > 0.500 for both) after adjusting for key baseline patient characteristics and hospital factors, which became significant (p < 0.01 for both). Patient level factors accounted for 96%-99% of total variation in these end points, leaving the remaining 1% and 4% of variance attributable to hospital level factors.

CONCLUSION

The international differences in clinical outcomes in this study of NSTE ACS are primarily accounted for by the patient level factors, with hospital level factors playing a minor part, and the country level factors a negligible one. These findings have significant policy and research implications involving international collaboration and comparisons.

Geographic variability in patient characteristics, treatment and outcome in an International Trial of Magnesium in acute myocardial infarction

BACKGROUND

The interpretation of clinical trials and efforts directed at reducing the worldwide burden of coronary disease must take regional differences into account. This study examined the regional differences in baseline characteristics, treatment, and outcome in patients presenting with ST elevation myocardial infarction (STEMI) who were entered into the Magnesium in Coronaries (MAGIC) trial.

METHODS AND RESULTS

MAGIC randomized 6213 patients to standard care with either placebo infusion or infusion of intravenous magnesium sulphate. There was no difference in mortality between these groups. For this analysis, three geographic regions were identified (Region 1=United States and Canada; Region 2=Bulgaria, Georgia, and Russia; Region 3=Austria, Belgium, Chile, Hungary, Israel, the Netherlands, New Zealand, and Venezuela) and compared with respect to baseline characteristics, treatment, and 30-day mortality. Patients in Region 2 had the highest prevalence of adverse risk factors at entry, including history of prior myocardial infarction, heart failure, stroke, and hypertension; anterior location of index acute myocardial infarction; and presence of pulmonary congestion at presentation. Furthermore, Region 2 patients infrequently received reperfusion therapy compared with those in Region 1. Region 3 was intermediate in this regard. Mortality was highest in Region 2, least in Region 1, and intermediate in Region 3.

CONCLUSION

Geographic location, particularly, parts of Eastern Europe, is strongly and independently associated with mortality following STEMI. This geographic variation in mortality confirms prior reports, although adequate explanations continue to be elusive and are beyond the scope of this large simple trial. Future international trials must recognize this variation in design, analysis, and interpretation.

A nodoventricular fiber associated with dual AV nodal conduction, AV nodal reentrant tachycardia, and anterior location of the slow AV nodal pathway

We present a case of a patient with a nodoventricular tract, associated with dual AV nodal conduction and AV nodal reentrant tachycardia, and an anteroseptal location of the slow AV nodal pathway. The remarkable feature of this case is the site of successful ablation, in the anteroseptum just anterior and superior to the His bundle, where both preexcitation and dual AV nodal physiology were abolished.

Adenosine-sensitive atrial reentrant tachycardia originating from the atrioventricular nodal transitional area

INTRODUCTION

Atrial tachycardia shows wide variations in its electrophysiologic properties and sites of origin. We report an atrial tachycardia with ECG manifestations and electrophysiologic characteristics similar to an atypical form of AV nodal reentrant tachycardia (AVNRT).

METHODS AND RESULTS

This supraventricular tachycardia was observed in 11 patients. It was initiated by atrial extrastimulation with an inverse relationship between the coupling interval of an extrastimulus and the postextrastimulus interval. Its induction was not related to a jump in the AH interval, and its perpetuation was independent of conduction block in AV node. Ventricular pacing during tachycardia demonstrated AV dissociation without affecting the atrial cycle length. A very small dose of adenosine triphosphate (mean 3.9 +/- 1.2 mg) could terminate the tachycardia. The earliest atrial activation during tachycardia was recorded at the low anteroseptal right atrium with a different intra-atrial activation sequence from that recorded during ventricular pacing, where the tachycardia was successfully ablated in 9 of 10 attempted patients. Bidirectional AV nodal conduction remained unaffected after successful ablation.

CONCLUSION

There may be an entity of adenosine-sensitive atrial tachycardia probably due to focal reentry within the AV node or its transitional tissues without involvement of the AV nodal pathways. This tachycardia can be ablated without disturbing AV nodal conduction from the right atrial septum.

Electrophysiology of the atrio-AV nodal inputs and exits in the normal dog heart: radiofrequency ablation using an epicardial approach

INTRODUCTION

We studied the effects of selective and combined ablation of the fast (FP) and slow pathway (SP) on AV and VA conduction in the normal dog heart using a novel epicardial ablation technique.

METHODS AND RESULTS

For FP ablation, radiofrequency current (RFC) was applied to a catheter tip that was held epicardially against the base of the right atrial wall. SP ablation was performed epicardially at the crux the heart. Twenty-three dogs were assigned to two ablation protocols: FP/SP ablation group (n = 17) and SP/FP ablation group (n = 6). In 12 of 17 dogs, FP ablation prolonged the PR interval (97 +/- 10 to 149 +/- 22 msec, P < 0.005) with no significant change in anterograde Wenckebach cycle length (WBCL). Subsequent SP ablation performed in 8 dogs further prolonged the PR interval and the anterograde WBCL (117 +/- 22 to 193 +/- 27, P < 0.005). Complete AV block was seen in 1 of 8 dogs, whereas complete or high-grade VA block was seen in 6 of 8 dogs. In the SP/FP ablation group, SP ablation significantly increased WBCL with no PR changes. Combined SP/FP ablation in 6 dogs prolonged the PR interval significantly, but no instance of complete AV block was seen. VA block was found in 50% of these cases. Histologic studies revealed that RFC ablation affected the anterior and posterior atrium adjacent to the undamaged AV node and His bundle.

CONCLUSION

Using an epicardial approach, combined ablation of the FP and SP AV nodal inputs can be achieved with an unexpectedly low incidence of complete AV block, although retrograde VA conduction was significantly compromised.

Difference in countries' use of resources and clinical outcome for patients with cardiogenic shock after myocardial infarction: results from the GUSTO trial

BACKGROUND

Use of aggressive and invasive interventions is more common in the USA than in other countries. We have compared use of resources for patients with cardiogenic shock after myocardial infarction in the USA and in other countries, and assessed the association between use of resources and clinical outcomes.

METHODS

We analysed data for patients with cardiogenic shock after myocardial infarction who were enrolled in the GUSTO-I trial (1891 treated in the USA, 1081 treated in other countries). Patients were randomly assigned combinations of streptokinase, heparin, and accelerated tissue-plasminogen activator (t-PA), then decisions about further interventions were left to the discretion of the attending physician. The interventions included in our analysis were: pulmonary-artery catheterisation, cardiac catheterisation, intravenous inotropic agents, ventilatory support, intra-aortic balloon counterpulsation (IABP), percutaneous transluminal coronary angioplasty (PTCA), and coronary bypass graft surgery (CABG). The primary outcome measure was death from any cause at 30 days of follow-up.

FINDINGS

Patients who were treated in the USA were significantly younger than those treated elsewhere (median 68 [IQR 59-75] vs 70 [62-76], p < 0.001), a smaller proportion had anterior infarction (49 vs 53%, p < 0.001), and they had a shorter time to treatment (mean 3.1 vs 3.3 h, p < 0.001). Aggressive diagnostic and therapeutic procedures were used more commonly in the USA than in the other countries: cardiac catheterisation (58 vs 23%); IABP (35 vs 7%); right-heart catheterisation (57 vs 22%); and ventilatory support (54 vs 38%). 483 (26%) of the patients treated in the USA underwent PTCA, compared with 82 (8%) patients in other countries. Patients who underwent revascularisation had better survival in all countries. Adjusted 30-day mortality was significantly lower among patients treated in the USA than among those treated elsewhere (50 vs 66%, p < 0.001). The difference in mortality remained at 1 year-56% of patients treated in the USA died versus 70% of patients treated elsewhere (hazard ratio 0.69 [95% CI 0.63-0.75], p < 0.001).

INTERPRETATION

30-day and 1-year mortality was significantly lower among patients treated in the USA than among those treated in other countries. This difference in mortality may be due to the greater use of invasive diagnostic and therapeutic interventions in the USA.

Prognostic significance of precordial ST segment depression on admission electrocardiogram in patients with inferior wall myocardial infarction

OBJECTIVES

This study assessed retrospectively the correlation between the pattern of precordial ST segment depression on the admission electrocardiogram (ECG) and hospital mortality in patients with an inferior myocardial infarction treated with intravenous thrombolytic therapy.

BACKGROUND

Previous studies have shown that in acute inferior myocardial infarction, ST segment depression in the precordial leads is associated with increased hospital mortality. However, the significance of the different patterns of precordial ST segment depression has been evaluated in only two previous studies.

METHODS

The study included 1,321 patients (1,020 men) who enrolled in the Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO-I) trial in Israel and received intravenous thrombolytic therapy. Patients with an ST segment elevation > or = 0.1 mV in at least two of the inferior leads were included. Patients were classified into four groups on the basis of their admission ECG: group I = patients with no precordial ST segment depression (n = 346); group II = those for whom the sum of ST segment depression in leads V1 to V3 was greater than that in leads V4 to V6 (n = 700); group III = those for whom the sum of ST depression in leads V1 to V3 was equal to that in leads V4 to V6 (n = 162); group IV = those with maximal ST depression in leads V4 to V6 (n = 113).

RESULTS

The overall hospital mortality rate was 3.6% (48 patients): for groups I, II, III and IV it was 2.9%, 2.8%, 4.3% and 9.7%, respectively. Multivariable logistic regression analysis confirmed that hospital mortality was independently associated with the pattern of precordial ST segment depression. The odd ratios in group IV relative to group I was 2.78 (95% confidence interval 1.26 to 6.13, p = 0.007).

CONCLUSIONS

The risk of mortality is higher in patients with an inferior myocardial infarction and maximal ST segment depression in precordial leads V4 to V6 versus precordial leads V1 to V3 on the admission ECG.

Mechanisms of AV node modulation in AV node reentry tachycardia

Atrioventricular nodal reentrant tachycardia has been recognized for many years as a very common cause of supraventricular tachycardia. First curable by surgery, this tachycardia is now successfully approached by selective radiofrequency current application to the slow pathway of the reentrant circuit. Importantly, these curative treatments brought evidence that the reentrant circuit of this arrhythmia was not confined to the compact atrioventricular (AV) node. These findings stimulate anatomists and basic and clinical electrophysiologists to fundamentally reconsider the atrioventricular junction in order to better understand the mysteries of atrioventricular junctional reentrant tachycardia, as we still do not know exactly what we are doing in AV node region procedures. This article will focus on the different hypotheses regarding the effect of selective slow AV pathway ablation in AV junctional reentrant tachycardia.

Initiating reentry: the role of nonuniform anisotropy in small circuits

Until recently only two types of media have been considered to provide the nonuniformities necessary to initiate cardiac reentry: (1) continuous isotropic media with intrinsic repolarization inhomogeneities; and (2) continuous isotropic media free of inhomogeneities in which repolarization nonuniformities are introduced transiently. The purpose of this article is to establish cellular coupling as a basis for arrhythmias by placing a new type of inhomogeneity, nonuniform anisotropy due to sparse side-to-side coupling between cells, in an overall perspective with the other nonuniformities that lead to reentry. Review of experimental and theoretical models of reentry leads to the following picture: with slowed conduction, reentrant circuits diminish in size and the nonuniformities necessary for reentry are provided by nonuniform anisotropy. Repolarization nonuniformities create functionally different pathways for reentrant circuits of relatively large size (> 30-50 mm2). Nonuniform anisotropic cellular coupling, which is associated with underlying microfibrosis, makes it possible for reentry to occur in small areas (< 10-15 mm2). A general property found in nonuniform anisotropic bundles is the presence of functionally different pathways in the absence of intrinsic repolarization inhomogeneities--one of fast longitudinal conduction with a longer refractory period, and another of "very slow" transverse conduction with a shorter refractory period. Since it is not known if nonuniform anisotropy exists in the AV node, the best known structure with small reentrant circuits, we performed microscopic extracellular measurements in the AV node of the rabbit. The transitional zone of the AV node was found to have markedly nonuniform anisotropic conduction properties. The analysis provides the view that functionally different pathways of small reentrant circuits, including those of the AV node, need to be reevaluated in terms of the role of nonuniform anisotropic cellular coupling.