Pre-Hospital Reduced-Dose Fibrinolysis Coupled With Urgent Percutaneous Coronary Intervention Reduces Time to Reperfusion and Improves Angiographic Perfusion Score Compared With Prehospital Fibrinolysis Alone or Primary Percutaneous Coronary Intervention

Pre-hospital versus in-hospital thrombolysis for ST-elevation myocardial infarction

BACKGROUND

Early thrombolysis for individuals experiencing a myocardial infarction is associated with better mortality and morbidity outcomes. While traditionally thrombolysis is given in hospital, pre-hospital thrombolysis is proposed as an effective intervention to save time and reduce mortality and morbidity in individuals with ST-elevation myocardial infarction (STEMI). Despite some evidence that pre-hospital thrombolysis may be delivered safely, there is a paucity of controlled trial data to indicate whether the timing of delivery can be effective in reducing key clinical outcomes.

OBJECTIVES

To assess the morbidity and mortality of pre-hospital versus in-hospital thrombolysis for STEMI.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OVID), EMBASE (OVID), two citation indexes on Web of Science (Thomson Reuters) and Cumulative Index to Nursing and Allied Health Literature (CINAHL) for randomised controlled trials and grey literature published up to June 2014. We also searched the reference lists of articles identified, clinical trial registries and unpublished thesis sources. We did not contact pharmaceutical companies for any relevant published or unpublished articles. We applied no language, date or publication restrictions. The Cochrane Heart Group conducted the primary electronic search.

SELECTION CRITERIA

We included randomised controlled trials of pre-hospital versus in-hospital thrombolysis in adults with ST-elevation myocardial infarction diagnosed by a healthcare provider.

DATA COLLECTION AND ANALYSIS

Two authors independently screened eligible studies for inclusion and carried out data extraction and 'Risk of bias' assessments, resolving any disagreement by consulting a third author. We contacted authors of potentially suitable studies if we required missing or additional information. We collected efficacy and adverse effect data from the trials.

MAIN RESULTS

We included three trials involving 538 participants. We found low quality of evidence indicating uncertainty whether pre-hopsital thrombolysis reduces all-cause mortality in individuals with STEMI compared to in-hospital thrombolysis (risk ratio 0.73, 95% confidence interval 0.37 to 1.41). We found high-quality evidence (two trials, 438 participants) that pre-hospital thrombolysis reduced the time to receipt of thrombolytic treatment compared with in-hospital thrombolysis. For adverse events, we found moderate-quality evidence that the occurrence of bleeding events was similar between participants receiving in-hospital or pre-hospital thrombolysis (two trials, 438 participants), and low-quality evidence that the occurrence of ventricular fibrillation (two trials, 178 participants), stroke (one trial, 78 participants) and allergic reactions (one trial, 100 participants) was also similar between participants receiving in-hospital or pre-hospital thrombolysis. We considered the included studies to have an overall unclear/high risk of bias.

AUTHORS' CONCLUSIONS

Pre-hospital thrombolysis reduces time to treatment, based on studies conducted in higher income countries. In settings where it can be safely and correctly administered by trained staff, pre-hospital thrombolysis may be an appropriate intervention. Pre-hospital thrombolysis has the potential to reduce the burden of STEMI in lower- and middle-income countries, especially in individuals who have limited access to in-hospital thrombolysis or percutaneous coronary interventions. We found no randomised controlled trials evaluating the efficacy of pre-hospital thrombolysis for STEMI in lower- and middle-income countries. Large high-quality multicentre randomised controlled trials implemented in resource-constrained countries will provide additional evidence for the efficacy and safety of this intervention. Local policy makers should consider their local health infrastructure and population distribution needs. These considerations should be taken into account when developing clinical guidelines for pre-hospital thrombolysis.

Comparison of outcomes for patients ≥75 years of age treated with pre-hospital reduced-dose fibrinolysis followed by percutaneous coronary intervention versus percutaneous coronary intervention alone for treatment of ST-elevation myocardial infarction

A coordinated system of care for patients with ST-segment elevation myocardial infarctions that includes prehospital administration of reduced-dose fibrinolytic agents coupled with urgent percutaneous coronary intervention (PCI), termed FAST-PCI, has been shown to be at least as effective as primary PCI (PPCI) alone. However, this reduced-dose fibrinolytic strategy could be associated with increased bleeding risk, especially in elderly patients. The purpose of this study was to examine 30-day outcomes in patients aged ≥75 years with ST-segment elevation myocardial infarctions treated with either strategy. Data from 120 patients aged ≥75 years treated with FAST-PCI were compared with those of 94 patients aged ≥75 years treated with PPCI. The primary comparator was mortality at 30 days. Stroke, reinfarction, and major bleeding were also compared. The groups were well matched for age, cardiac risk factors, and ischemic times. At 30 days, mortality was lower with FAST-PCI than with PPCI (4.2% vs 18.1%, p <0.01). Rates of stroke, reinfarction, and major bleeding (4% vs 2%) were similar in the 2 groups. The FAST-PCI cohort had lower rates of cardiogenic shock on hospital arrival (15% vs 26%, p = 0.05) and completely occluded infarct arteries (Thrombolysis In Myocardial Infarction [TIMI] grade 0 flow, 35% vs 61%, p <0.01). In conclusion, for patients aged ≥75 years with ST-segment elevation myocardial infarctions, a FAST-PCI strategy in a coordinated system of care was associated with reduced 30-day mortality, earlier infarct artery patency, and lower incidence of cardiogenic shock at arrival compared with PPCI, without apparent bleeding, stroke, or reinfarction penalties.

Prehospital treatment of ST-segment elevated myocardial infarction patients

Providing optimal care to patients with ST-segment elevated myocardial infarction is challenging. If a patient experiences chest pain and calls the emergency number, a cascade of actions is initiated that should lead to a diagnosis, start of treatment and reperfusion of the infarcted myocardium. This should all happen within 90 min after first medical contact, irrespective of the location of the patient or the time of day. The complex organization that is needed to achieve this goal in every ST-segment elevated myocardial infarction patient accounts for a fascinating interplay between prehospital and in-hospital care, in a situation when every minute counts. State-of-the-art care should be provided according to the latest insights and guidelines.

Prehospital 12-Lead Electrocardiogram within 60 Minutes Differentiates Proximal versus Nonproximal Left Anterior Descending Artery Myocardial Infarction

Introduction

Acute anterior myocardial infarctions caused by proximal left anterior descending (LAD) artery occlusions are associated with a higher morbidity and mortality. Early identification of high-risk patients via the 12-lead electrocardiogram (ECG) could assist physicians and emergency response teams in providing early and aggressive care for patients with anterior ST-elevation myocardial infarctions (STEMI). Approximately 25% of US hospitals have primary percutaneous coronary intervention (PCI) capability for the treatment of acute myocardial infarctions. Given the paucity of hospitals capable of PCI, early identification of more severe myocardial infarction may prompt emergency medical service routing of these patients to PCI-capable hospitals. We sought to determine if the 12 lead ECG is capable of predicting proximal LAD artery occlusions.

Methods

In a retrospective, post-hoc analysis of the Pre-Hospital Administration of Thrombolytic Therapy with Urgent Culprit Artery Revascularization pilot trial, we compared the ECG findings of proximal and nonproximal LAD occlusions for patients who had undergone an ECG within 180 minutes of symptom onset.

Results

In this study, 72 patients had anterior STEMIs, with ECGs performed within 180 minutes of symptom onset. In patients who had undergone ECGs within 60 minutes (n = 35), the mean sum of ST elevation (STE) in leads V1 through V6 plus ST depression (STD) in leads II, III, and aVF was 19.2 mm for proximal LAD occlusions and 11.7 mm for nonproximal LAD occlusions (P = 0.007). A sum STE in V1 through V6 plus STD in II, III, and aVF of at least 17.5 mm had a sensitivity of 52.3%, specificity of 92.9%, positive predictive value of 91.7%, and negative predictive value of 56.5% for proximal LAD occlusions. When the ECG was performed more than 60 minutes after symptom onset (n = 37), there was no significant difference in ST-segment deviation between the 2 groups.

Conclusion

The sum STE (V1-V6) and STD (II, III, aVF) on a 12-lead ECG can be used to predict proximal LAD occlusions if performed within the first hour of symptom onset. This should be considered a high-risk finding and may prompt prehospital direction of such patients to PCI-capable hospitals.

Prehospital fibrinolytic therapy followed by urgent percutaneous coronary intervention in patients with ST-elevation myocardial infarction

In patients with ST-segment elevation myocardial infarction (STEMI) the shorter the reperfusion time, the better the outcome is, regardless of the reperfusion method. Effective, early and rapid reperfusion is the most important goal in the treatment of patients with STEMI. In majority cases of STEMI, transport or transfer to a percutaneous coronary intervention (PCI)-capable center will occur, sometimes bypassing the closest hospital facilities that are not PCI centers. The timely optimal reperfusion strategy might be a prehospital initiated pharmacological reperfusion with subsequent PCI. Reduced-dose prehospital fibrinolysis allows safe transport of STEMI patients to PCI centers for urgent culprit artery PCI, and may be a superior approach compared with transporting patients to the closest non-PCI hospital for fibrinolytic therapy. In this review we will discuss the evidence regarding reperfusion strategies in STEMI patients.

Unresolved issues in myocardial reperfusion injury

While the basic pathobiology of myocardial ischemic injury and reperfusion has been determined over the last 50 years, there are important, unresolved, or at least not completely elucidated, issues in the field. These include the relative contributions of different modes of cell injury and death to evolving myocardial infarcts; interactions of phenomena produced by reperfusion, including stunning and preconditioning; and potential new approaches for successfully combining adjuvant therapy with coronary artery opening. A model of myocardial ischemic and reperfusion injury is proposed involving the potential expression of apoptotic and oncotic pathways in the same perturbed cardiomyocytes. Promising new cardioprotective strategies for reducing lethal reperfusion injury are discussed, including ischemic postconditioning, activators of the reperfusion injury salvage kinase (RISK) pathway, inhibitors of protein kinase c-delta, and inhibitors of the mitochondrial membrane permeability transition pore (PTP). Major outstanding clinical challenges are also discussed, including the development of clinical care systems that can routinely deliver very timely coronary opening and reperfusion, perhaps combined with adjuvant therapy, and the development of strategies to retard adverse remodeling and congestive heart failure in patients with significant myocardial infarction and scarring, perhaps by refinements in stem cell therapy.