Effect of prehospital thrombolysis on aborting acute myocardial infarction

Prehospital tirofiban increases the rate of disrupted myocardial infarction in patients with ST-segment elevation myocardial infarction: insights from the On-TIME 2 trial

AIMS

In patients with ST-segment elevation myocardial infarction (STEMI), prehospital tirofiban significantly improved myocardial reperfusion. However, its impact on the rate of disrupted myocardial infarction (MI), particularly in the context of high-sensitivity cardiac troponin (hs-cTn) assays, is still unclear.

METHODS AND RESULTS

The On-TIME 2 (Ongoing Tirofiban In Myocardial infarction Evaluation 2) trial randomly assigned STEMI patients to prehospital tirofiban or placebo before transportation to a percutaneous coronary intervention (PCI) centre. In this post hoc analysis, we evaluated STEMI patients that underwent primary PCI and had measured hs-cTn levels. Troponin T levels were collected at 18-24 and 72-96 h after PCI. Disrupted MI was defined as peak hs-cTn T levels ≤ 10 times the upper limit of normal (≤140 ng/L). Out of 786 STEMI patients, 47 (6%) had a disrupted MI. Disrupted MI occurred in 31 of 386 patients (8.0%) in the tirofiban arm and in 16 of 400 patients (4.0%) in the placebo arm (P = 0.026). After multivariate adjustment, prehospital tirofiban remained independently associated with disrupted MI (odds ratio 2.03; 95% confidence interval 1.10-3.87; P = 0.027). None of the patients with disrupted MI died during the 1-year follow-up, compared with a mortality rate of 2.6% among those without disrupted MI.

CONCLUSION

Among STEMI patients undergoing primary PCI, the use of prehospital tirofiban was independently associated with a higher rate of disrupted MI. These results, highlighting a potential benefit, underscore the need for future research focusing on innovative pre-treatment approaches that may increase the rate of disrupted MI.

The Canadian Cardiovascular Society Classification of Acute Atherothrombotic Myocardial Infarction Based on Stages of Tissue Injury Severity: An Expert Consensus Statement

Myocardial infarction (MI) remains a leading cause of morbidity and mortality. In atherothrombotic MI (ST-elevation MI and type 1 non-ST-elevation MI), coronary artery occlusion leads to ischemia. Subsequent cardiomyocyte necrosis evolves over time as a wavefront within the territory at risk. The spectrum of ischemia and reperfusion injury is wide: it can be minimal in aborted MI or myocardial necrosis can be large and complicated by microvascular obstruction and reperfusion hemorrhage. Established risk scores and infarct classifications help with patient management but do not consider tissue injury characteristics. This document outlines the Canadian Cardiovascular Society classification of acute MI. It is an expert consensus formed on the basis of decades of data on atherothrombotic MI with reperfusion therapy. Four stages of progressively worsening myocardial tissue injury are identified: (1) aborted MI (no/minimal myocardial necrosis); (2) MI with significant cardiomyocyte necrosis, but without microvascular injury; (3) cardiomyocyte necrosis and microvascular dysfunction leading to microvascular obstruction (ie, "no-reflow"); and (4) cardiomyocyte and microvascular necrosis leading to reperfusion hemorrhage. Each stage reflects progression of tissue pathology of myocardial ischemia and reperfusion injury from the previous stage. Clinical studies have shown worse remodeling and increase in adverse clinical outcomes with progressive injury. Notably, microvascular injury is of particular importance, with the most severe form (hemorrhagic MI) leading to infarct expansion and risk of mechanical complications. This classification has the potential to stratify risk in MI patients and lay the groundwork for development of new, injury stage-specific and tissue pathology-based therapies for MI.

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.

Aborted myocardial infarction after primary percutaneous coronary intervention: magnetic resonance imaging insights from the Assessment of Pexelizumab in Acute Myocardial Infarction (APEX-AMI) trial

BACKGROUND

Aborted myocardial infarction (AbMI) in patients with ST-elevation MI defined by ST resolution with less than 2-fold elevation in biomarkers has been previously reported. We examined the association among AbMI, other metrics of infarct size, and left ventricular (LV) function defined by cardiac magnetic resonance (CMR).

METHODS

A total of 5745 patients with ST-elevation MI enrolled in the APEX-AMI trial, and 73 who were part of the CMR substudy within 3 to 5 days of randomization were evaluated. Core laboratories analyzed electrocardiograms, angiograms, and CMR images.

RESULTS

Aborted MI (peak creatine kinase/creatine kinase MB <2× upper limit of normal) with typical evolutionary electrocardiogram changes was observed in 11% (437/3938) overall and in 19% (14/73) of patients within the CMR study. Patients with AbMI were older (62 vs 60 years, P = .003) and tended to achieve complete STE-resolution post-percutaneous coronary intervention (≥70% resolution: 64% vs 32%; P = .076) compared with patients with MI. Cardiac magnetic resonance revealed that patients with AbMI had a smaller infarct size (4.7% vs 14.9% LV, P < .001), less "no reflow" (0.9% vs 1.7% LV, P = .017), enhanced LV function (ejection fraction 54.4% vs 46.5%, P = .064), smaller LV end-systolic volumes (46.5 mL vs 67.2 mL, P = .009), and less transmurality (21.4% vs 50.9% with at least 1 segment with >75% wall thickness, P = .046) when compared with patients with MI.

CONCLUSIONS

Patients with AbMI had smaller subendocardial infarcts with enhanced LV size and function. Cardiac magnetic resonance provides corroborative evidence of AbMI and insights into its pathophysiology, specifically rapid successful reperfusion leading to limitation of the "wavefront" of infarct to the subendocardium.

Setting Up a Population-Based Program to Optimize ST-Segment Elevation Myocardial Infarction Care

The development of ST-segment elevation myocardial infarction (STEMI) systems of care at the city, region, or nation levels has not only improved the speed of reperfusion but also enhanced the reach of primary angioplasty to areas far from percutaneous coronary intervention (PCI) centers. Setting up a STEMI system of care is a sophisticated process that requires a solid PCI hospital and emergency medical services infrastructure, disciplined collaboration, and a focus on outcomes measurement and continuous quality improvement. This article reviews the accumulated evidence supporting the development of STEMI systems of care and offers practical insights into this process.

Abortion of myocardial infarction by primary angioplasty mainly depends on preprocedural TIMI flow

AIMS

To define frequency and predictors of aborted myocardial infarctions (MI) after primary angioplasty.

METHODS AND RESULTS

We analysed 196 consecutive patients with the clinical diagnosis of ST-elevation acute coronary syndrome (ST-ACS) admitted for primary angioplasty to one interventional facility between October 2005 and September 2006. Aborted MI was defined as a creatine increase of less than two times the upper limit of normal, combined with typical evolutionary electrocardiographic changes. Masquerading MI was diagnosed if evolutionary changes were missing or could be attributed to other causes. Thirty-four patients (17,3%) had an aborted and nine (4,6%) a masquerading MI. The main predictor of abortion was Thrombolysis In Myocardial Infarction (TIMI) flow 2 or 3 prior to procedure. The in-hospital mortality of aborted MI was 0%, the one year mortality 2.9%. Sixteen patients without prior or inter-current myocardial infarction had a preserved ejection fraction on cardiac MR at 12 months; in six patients even without any detection of late enhancement.

CONCLUSIONS

There is a substantial proportion of aborted myocardial infarction after primary angioplasty, corresponding to a small or even non detectable scar formation in terms of late enhancement on cardiac MR. Preprocedural TIMI flow 2 or 3 is the main predictor of aborted MI.

Prognostic significance and magnetic resonance imaging findings in aborted myocardial infarction after primary angioplasty

BACKGROUND

Aborted myocardial infarction (MI) is defined by major (> or =50%) ST-segment resolution and a lack of subsequent cardiac enzyme rise > or =2 the upper normal limit. This ultimate myocardial salvage has been observed in approximately 15% of ST-elevation MI (STEMI) patients after fibrinolysis. So far, the prognostic significance and magnetic resonance imaging (MRI) findings of an aborted MI after primary angioplasty have not been evaluated appropriately.

METHODS

We examined 420 consecutive STEMI patients undergoing primary angioplasty within 12 hours after symptom onset. All patients underwent MRI within 1 to 4 days. Clinical end points were major adverse cardiovascular events within 6 months after the index event.

RESULTS

Of the 420 STEMI patients, 58 (14%) fulfilled aborted MI criteria. As compared with true MI, patients with aborted MI had a significant lower infarct size, shorter pain-to-balloon time, and better left ventricular ejection fraction (P < .001, respectively). Aborted MI patients had a 6-month major adverse cardiovascular event rate of 1.7% versus 19.6% of true MI patients (P = .001). In aborted MI patients, MRI detected no myocardial scar in 30 (56%), and a minor necrosis/scar formation in 24 patients (44%).

CONCLUSION

The proven prognostic relevance of aborted MI makes it a meaningful end point and therapeutic target in future MI studies. MRI can further distinguish between true aborted MI with absence of myocardial scar and aborted MI with scar formations.

Aborted myocardial infarction: is it real in the troponin era?

BACKGROUND

Cardiac troponins are the markers of choice for the diagnosis of acute myocardial infarction. The objective of this study was to compare the frequency of "aborted myocardial infarction" (no detectable myocardial injury) determined by measurement of troponin versus that determined by creatine kinase (CK) and creatine kinase-muscle brain (CK-MB) measurement criteria among patients with ST-elevation myocardial infarction (STEMI) who received reperfusion therapy.

METHODS

Since 2004, the Mayo Clinic (Rochester, MN) has had a standard reperfusion protocol for the treatment of patients with STEMI. During the study period, 767 patients presented with new or presumed new ST elevation or left bundle block.

RESULTS

The diagnosis of STEMI was confirmed in 765 (99.7%) patients. Using the 99th percentile cutoff value, troponin T elevations occurred in 765 (100%) of 765 patients when serial samples were available. Creatine kinase-MB levels of twice or more the upper limit of normal occurred in 681 (90.1%) of 749 patients with serial samples for CK-MB, and CK equal or greater than twice the gender-specific upper limits of normal occurred in 521 (78.8%) of 661 patients with serial samples for CK available.

CONCLUSION

The frequency of aborted myocardial infarction is 0% when using troponin at the 99th percentile cutoff as recommended by contemporary guidelines from the European Society of Cardiology (Nice, France) and American College of Cardiology (Washington, DC).

The use of biomarkers for the evaluation and treatment of patients with acute coronary syndromes

The advent of inexpensive, highly accurate, and predictive markers of myocardial injury, inflammation, and hemodynamic stability has revolutionized the evaluation and treatment of patients who have acute coronary syndromes (ACSs). These blood biomarkers require small sample volumes, can be run expeditiously, and provide important information concerning the diagnosis, risk stratification, and treatment of these patients. To understand the use of these markers, one must have some knowledge about what elevations in these markers imply, how they have to be collected and measured to provide reliable information, when to suspect analytic confounds, and what the key values are that impart the diagnostic, prognostic, and therapeutic information. This article discusses these issues, emphasizing what clinicians must know for optimal test use, and then addresses the practical use of these markers in patients who have ACS.

Aborted myocardial infarction: a new target for reperfusion therapy

Reperfusion therapy for ST-elevation acute coronary syndromes aims at early and complete recanalization of the infarct-related artery in order to salvage myocardium and improve both early and late clinical outcomes. Myocardial necrosis is usually confirmed and quantified by myocardial enzyme release in plasma. However, over 10% of patients treated with reperfusion therapy fail to develop an enzyme rise, but do exhibit transient ECG changes, which are consistent with an aborted myocardial infarction. The earlier the reperfusion therapy is instituted, the higher the incidence of aborted infarction. Treatment within an hour after symptom onset may result in 25% of aborted infarction and is in combination with complete (70%) ST-segment resolution associated with better survival. This endpoint is easy to define and occurs promptly in time. The faster that effective treatment is initiated, the more likely aborted infarction will occur. Given that mortality, re-infarction, and stroke are declining in incidence, we suggest the introduction of aborted infarction as an endpoint in clinical trials of ST-elevation acute coronary syndromes.

Aborted myocardial infarction in patients with ST-segment elevation

OBJECTIVES

The investigators undertook a systematic, comprehensive analysis of the therapeutic response and clinical outcomes of reperfusion therapy for acute ST-segment elevation myocardial infarction (STEMI) in 5,470 patients from the Assessment of the Safety and Efficacy of a New Thrombolytic Regimen (ASSENT)-3 trial.

BACKGROUND

Prompt effective reperfusion therapy for acute STEMI may attenuate major myocardial necrosis.

METHODS

We prospectively collected sequential electrocardiographs and clinical data. Aborted myocardial infarction (MI) was defined as maximal creatine kinase < or =2x upper limit of normal coupled with typical evolutionary electrocardiographic changes.

RESULTS

Of the patients, 727 (13.3%) had an aborted MI, with the highest frequency (25%) occurring in patients treated <1 h after symptom onset. As compared with MI patients, patients with aborted MI more often had complete ST-segment resolution at 60 min (56.3% vs. 30.2%, p < 0.001) and 180 min (61.5% vs. 53%, p < 0.001); they also had smaller infarct sizes based on QRS score at discharge (2.37 vs. 4.62, p <0.001). Mortality in aborted MI patients compared with those who had true MI was 3.9% versus 4.6% at 30-day and 7.0% versus 7.4% at 1-year. The baseline-adjusted mortality was significantly lower in patients with aborted MI (odds ratio [OR] 0.76, 95% confidence interval [CI] 0.63 to 0.92, p = 0.005 for 30-day and OR 0.70, 95% CI 0.50 to 0.98, p = 0.035 for one year). A very low-risk subset was identified with > or =70% ST-segment resolution at 60 min whose 30-day and 1-year mortality was 1.0% and 2.7%, respectively, compared with 5.9% and 9.3% in aborted MI patients with <70% ST-segment resolution at 60 min (all p < or = 0.002).

CONCLUSIONS

Prompt fibrinolytic treatment improved the likelihood of aborted MI. The subgroup with complete 60-min ST-segment resolution had the best clinical outcomes.

Variations in pre-hospital fibrinolysis process of care: insights from the Assessment of the Safety and Efficacy of a New Thrombolytic 3 Plus international acute myocardial infarction pre-hospital care survey

The Assessment of the Safety and Efficacy of a New Thrombolytic 3 (ASSENT 3 PLUS) Plus trial (n=1639) was an international trial of pre-hospital fibrinolysis with tenecteplase randomly assigned to enoxaparin or unfractionated heparin, involving 106 sites in 12 countries. Given the potential impact of process of care delivery in various healthcare systems, we undertook a comprehensive validated survey of population demographics, geographical factors, emergency medical services, methods of electrocardiogram interpretation and pre-hospital fibrinolysis administration. The potential study population was 42.4 x 10(6) with 70% urban. The land areas of individual emergency medical services sites varied from 6 to 20000/km(2). Three emergency medical services personnel (range 2-5) attended each ambulance with the highest level of training, consisting of a physician (65%), registered nurse (20%) or paramedic. Before the initiation of the study, 72% of sites administered pre-hospital fibrinolysis (range 1-20 years). Electrocardiograms were interpreted on the scene in 60% and transmitted for physician's interpretation in the remainder; 41% of patients (679/1639) were enrolled at sites without a physician at the scene. The ASSENT 3 Plus trial incorporated a wide variation in population density, emergency medical services resources, and physician's interpretation of ECG and administering pre-hospital fibrinolysis. Understanding this diversity will help in evaluating the general applicability and feasibility of pre-hospital fibrinolysis in various health systems, as well as the pre-hospital care of ST elevation myocardial infarction patients regardless of reperfusion strategies.

Prehospital thrombolysis--calculated health benefit for catchment population of one hospital

The health benefit of thrombolysis in acute myocardial infarction is greatest when patients are treated soon after onset of symptoms. One approach to reducing treatment delay is to give thrombolysis before the patient reaches hospital. When an ambulance trust proposed a prehospital thrombolysis service, local commissioners requested an estimate of its possible health impact. Clinical audit and ambulance trust data were obtained for 165 patients who received thrombolysis for acute myocardial infarction in the coronary care unit of a local hospital in one year. This information was then used to estimate the health impact of prehospital thrombolysis in the local population in a mathematical model derived from the results of trials comparing prehospital and hospital thrombolysis. The best predicted local health benefit from the proposed prehospital thrombolysis service is that, if 45 minutes can be cut off the call-to-needle time, 61 cases of acute myocardial infarction need to be treated to save one additional life at 35 days. By use of published research data, the health benefits of prehospital thrombolysis can be estimated for a local population. Variables in the treatment population and ambulance service will influence the size of the health benefit that can be achieved.

Prehospital Thrombolysis—Calculated Health Benefit for Catchment Population of One Hospital

The health benefit of thrombolysis in acute myocardial infarction is greatest when patients are treated soon after onset of symptoms. One approach to reducing treatment delay is to give thrombolysis before the patient reaches hospital. When an ambulance trust proposed a prehospital thrombolysis service, local commissioners requested an estimate of its possible health impact. Clinical audit and ambulance trust data were obtained for 165 patients who received thrombolysis for acute myocardial infarction in the coronary care unit of a local hospital in one year. This information was then used to estimate the health impact of prehospital thrombolysis in the local population in a mathematical model derived from the results of trials comparing prehospital and hospital thrombolysis.

The best predicted local health benefit from the proposed prehospital thrombolysis service is that, if 45 minutes can be cut off the call-to-needle time, 61 cases of acute myocardial infarction need to be treated to save one additional life at 35 days.

By use of published research data, the health benefits of prehospital thrombolysis can be estimated for a local population. Variables in the treatment population and ambulance service will influence the size of the health benefit that can be achieved.

Preprocedural TIMI flow and mortality in patients with acute myocardial infarction treated by primary angioplasty

OBJECTIVES

The aim of the study was to evaluate the impact of preprocedural Thrombolysis In Myocardial Infarction (TIMI) flow on one-year mortality in patients with ST-segment elevation myocardial infarction (STEMI) treated by primary angioplasty.

BACKGROUND

Although there is an excellent outcome conferred by primary angioplasty in patients with STEMI, the prognostic role of early recanalization in these patients has yet to be investigated.

METHODS

Our population is composed of 1,791 patients with acute myocardial infarction treated by primary angioplasty at our institution from 1994 to 2001. All angiographic, clinical, and follow-up data were prospectively collected. According to the TIMI risk score, patients were stratified in low- and high-risk groups.

RESULTS

Preprocedural TIMI flow was related to postprocedural TIMI flow grade 3 (p = 0.002), myocardial blush grade 2 to 3 (p < 0.001), enzymatic infarct size (p < 0.001), predischarge ejection fraction (p < 0.001), and one-year mortality (p < 0.05). Multivariate analysis showed that preprocedural TIMI flow grade 3 was an independent predictor of one-year survival in high-risk patients (p < 0.05).

CONCLUSIONS

This study shows that preprocedural TIMI flow grade 3 is an independent predictor of one-year survival in high-risk patients with acute myocardial infarction treated by primary angioplasty. These data suggest that all efforts should be made to obtain early and optimal restoration of antegrade flow, particularly in high-risk patients and when transportation to tertiary centers, with a conceivable further time delay, is required.

Prehospital versus hospital fibrinolytic therapy using automated versus cardiologist electrocardiographic diagnosis of myocardial infarction: abortion of myocardial infarction and unjustified fibrinolytic therapy

BACKGROUND

This study investigated the incidence of abortion of myocardial infarction and of unjustified fibrinolysis by using automated versus cardiologist-assisted diagnosis of acute ST-elevation myocardial infarction. The results of prehospital diagnosis and treatment (2 cities in the Netherlands) were compared with those of inhospital treatment. Unjustified fibrinolysis must be differentiated from justified thrombolysis resulting in aborted myocardial infarction. Both have the absence of a significant rise in cardiac enzymes in common. In aborted myocardial infarction, this is a result of timely reperfusion; in unjustified thrombolysis, this is the result of an incorrect diagnosis.

METHODS

In the city of Rotterdam, 118 patients were treated before hospitalization for myocardial infarction, diagnosed through the use of a mobile computer electrocardiogram; in the city of Nijmegen, 132 patients were treated before hospitalization with the use of transtelephonic transmission of the electrocardiogram to the coronary care unit and judged by a cardiologist. Their data were compared with those of 269 patients treated inhospital in the city of Arnhem, using the same electrocardiographic criteria. Abortion of myocardial infarction was diagnosed as the absence of a significant rise in cardiac enzymes and the presence of resolution of chest pain and 50% of ST-segment deviation within 2 hours after onset of therapy. Lacking these, the diagnosis of unjustified fibrinolytic therapy was made.

RESULTS

Unjustified treatment occurred in 8 (3.2%) prehospital-treated patients (4 in Rotterdam and 4 in Nijmegen). Of the inhospital-treated patients in Arnhem, 5 (1.9%) were treated unjustifiably (P =.49). Aborted myocardial infarction occurred in 15.3% and 18.2% in Rotterdam and Nijmegen, respectively, against 4.5% in inhospital treatment in Arnhem (P <.001).

CONCLUSIONS

Abortion of myocardial infarction is associated with prehospital thrombolysis. Unjustified fibrinolysis for acute myocardial infarction occurs in prehospital fibrinolysis as frequently as in the inhospital setting. The use of different electrocardiographic methods for diagnosing acute myocardial infarction does not appear to make any difference.

Prehospital thrombolysis with reteplase: the Nijmegen/Rotterdam study

OBJECTIVE

The objective of this observational study was to assess time from electrocardiogram diagnosis to treatment and time from pain onset to treatment with double bolus reteplase compared to current therapy with streptokinase or bolus anistreplase in 2 cities (Rotterdam and Nijmegen) in the Netherlands, where prehospital thrombolysis is an established way of treatment of acute myocardial infarction.

METHODS

Prehospital thrombolysis is performed using electrocardiogram diagnosis by the ambulance service as well as bolus anistreplase for treatment in Nijmegen, and streptokinase infusion in Rotterdam. Reteplase or anistreplase/streptokinase was assigned open label to patients according to order of presentation on a 1-to-1 basis. All patients were treated with nitrates sublingually and aspirin orally. Time intervals were recorded by the ambulance staff.

RESULTS

In total, 250 patients were treated between April 1, 1999 and August 1, 2000. Reteplase was used in 120 patients and anistreplase/streptokinase in 130 patients. Using double bolus reteplase resulted in a significantly shorter time to treatment: a median of 81 minutes compared to a median of 104 minutes with the established therapy (P <.0001). There were no differences in mortality, aborted myocardial infarction, hemorrhagic stroke or the need for rescue angioplasty between the groups.

CONCLUSION

In prehospital thrombolysis, double bolus reteplase is associated with a shorter time to treatment than bolus anistreplase or infusion of streptokinase.

Safety and delay time in prehospital thrombolysis of acute myocardial infarction in urban and rural areas in Sweden

Sixteen hospitals in Sweden, including those in urban and more sparsely populated areas, and the associated ambulance organizations were enrolled in a prospective evaluation of the feasibility of treating patients with a ST-elevation infarction with a thrombolytic agent (reteplase) before hospital admission. A physician staffed the ambulances in 1% of cases, a nurse in 67%, and a staff nurse in 32% of cases. In all, 64 patients in urban areas and 90 patients in rural areas were included. The occurrence of complications before hospital admission was low and similar in the 2 groups. The median interval between the onset of symptoms and the start of thrombolysis was 1 hour 44 minutes in urban areas versus 2 hours 14 minutes in rural areas (P = 0.03). The median arrival time (interval between onset of symptoms and arrival of the ambulance) tended to be shorter in urban areas (1 hr 10 min vs 1 hr 33 min; not significant) and the median interval between the arrival of the ambulance and the start of thrombolysis was shorter in urban areas (27 min vs 36 min; P < 0.0001). When comparing urban areas with the least-populated rural areas, differences in various delay times became even more marked. Patients in urban areas had a higher ejection fraction and fewer symptoms of heart failure after 30 days and a lower 1-year mortality.

Prehospital ECG transmission: comparison of advanced mobile phone and facsimile devices in an urban Emergency Medical Service System

OBJECTIVE

To compare the speed and reliability of electrocardiogram (ECG) transmissions from the prehospital setting to a conventional table facsimile device and to an advanced mobile phone in a Helicopter Emergency Medical Service System (HEMS).

METHODS

Eighteen authentic ECGs stored in the memory module of a monitor defibrillator were used. The ECGs were (1) sent directly from the monitor defibrillator to a table fax and an advanced mobile phone at the HEMS base; (2) printed out and sent from a mobile fax connected to an ordinary mobile phone to the table fax and the advanced mobile phone at the HEMS base; (3) printed out and sent from an ordinary table fax as well as from a table fax connected to a satellite phone system to the receiving devices at the HEMS base.

RESULTS

When the ECGs were sent from the table fax via satellite, the transmission times were longer to the advanced mobile phone than to the table fax at the HEMS base (1 min 54 s+/-0 min 21 s vs. 1 min 37 s+/-0 min 20 s, (mean+/-SD), (P<0.01). Regarding transmission from the other fax devices, there were no differences in transmission times between the two receiving devices. The fastest way to transmit ECGs to the advanced mobile phone was to send it from conventional table fax (1 min 22 s+/-0 min 18 s) and the longest transmission times were with mobile fax connected to mobile phone (5 min 23 s+/-3 min 5 s). In all ECGs transmitted except one the cardiac rhythm and ST-changes could be recognised.

CONCLUSION

An advanced mobile phone is as fast and reliable as a conventional table fax in receiving ECGs. A mobile phone with advanced features is a practical tool for HEMS physicians who need to evaluate ECGs in the prehospital setting.

Abortion of acute ST segment elevation myocardial infarction after reperfusion: incidence, patients' characteristics, and prognosis

OBJECTIVES

To study the incidence and patient characteristics of aborted myocardial infarction in both prehospital and in-hospital thrombolysis.

DESIGN

Retrospective, controlled, observational study.

SETTING

Two cities in the Netherlands, one with prehospital thrombolysis, one with in-hospital treatment.

PATIENTS

475 patients with suspected acute ST elevation myocardial infarction treated before admission to hospital, 269 patients treated in hospital.

MAIN OUTCOME MEASURES

Aborted myocardial infarction, defined as the combination of subsiding of cumulative ST segment elevation and depression to < 50% of the level at presentation, together with a rise of creatine kinase of less than twice the upper normal concentration. A stepwise regression analysis was used to test independent predictors for aborted myocardial infarction.

RESULTS

After correction for "unjustified" thrombolysis, 17.1% of the 468 prehospital treated patients and 4.5% of the 264 in-hospital treated patients fulfilled the criteria for aborted myocardial infarction. There was no difference in age, sex, risk factors, haemodynamic status, and infarct location of aborted myocardial infarction compared with established myocardial infarction. Time to treatment was shorter in the patients with aborted myocardial infarction (86 versus 123 minutes, p = 0.05). A shorter time to treatment, lower ST elevation at presentation, and higher incidence of preinfarction angina were independent predictors for aborted myocardial infarction. Aborted myocardial infarction had a 12 month mortality of 2.2%, significantly less than the 11.6% of established myocardial infarction.

CONCLUSION

Prehospital thrombolysis is associated with a fourfold increase of aborted myocardial infarction compared with in-hospital treatment. A shorter time to treatment, a lower ST elevation, and a higher incidence of preinfarction angina were predictors of aborted myocardial infarction.

Implementation of prehospital thrombolysis in Sweden: components of delay until delivery of treatment and examination of treatment feasibility

OBJECTIVE

To evaluate the feasibility of prehospital thrombolysis in Sweden in terms of safety and to examine the various components of the delay between onset of symptoms and start of treatment.

SETTING

A total of 16 hospitals in Sweden in both urban and less populated areas and the associated ambulance organisations.

DESIGN

Prospective evaluation of patients with an ST-elevation infarction treated with reteplase. An ECG was recorded and transmitted to hospital. The ambulances were staffed by a physician in 1% of cases, a nurse in 67% and a staff nurse in 32%.

RESULTS

Of the 148 patients who received treatment prior to hospital admission, six (4%) had a cardiac arrest prior to hospital admission and two (1%) died prior to arrival at hospital. One patient was given treatment despite an exclusion criterion (previous stroke) and died on the 1st day in hospital due to a cerebral haemorrhage. The overall 30-day mortality was 7.1% and 1-year mortality 9.8%. Treatment was initiated within 2 h after the onset of symptoms in 53% of patients and within 1 h in 17% of patients. The median interval between the arrival of the ambulance and sending an ECG was 13 min and the median interval between sending an ECG and the start of thrombolysis was 18 min. The delay was similar regardless of ambulance staff.

CONCLUSION

Implementation of prehospital thrombolysis on a national basis in Sweden appears to be safe. More than half the patients can be given treatment less than 2 h after the onset of symptoms. There is potential for reducing this time still further.

Acute myocardial infarction

Acute myocardial infarction is a common disease with serious consequences in mortality, morbidity, and cost to the society. Coronary atherosclerosis plays a pivotal part as the underlying substrate in many patients. In addition, a new definition of myocardial infarction has recently been introduced that has major implications from the epidemiological, societal, and patient points of view. The advent of coronary-care units and the results of randomised clinical trials on reperfusion therapy, lytic or percutaneous coronary intervention, and chronic medical treatment with various pharmacological agents have substantially changed the therapeutic approach, decreased in-hospital mortality, and improved the long-term outlook in survivors of the acute phase. New treatments will continue to emerge, but the greatest challenge will be to effectively implement preventive actions in all high-risk individuals and to expand delivery of acute treatment in a timely fashion for all eligible patients.

Evaluation of emergency medical services systems: a classification to assist in determination of indicators

Emergency medical services (EMS) systems, and prehospital care are difficult to evaluate. Accordingly, the true efficacy and value of such systems are difficult to determine. The multitude of variations and combinations of involved factors makes standardisation and comparison difficult, and universal indicators are hard to develop. Various attempts have been made to determine valid indicators of effectiveness, but there has been little success. Prehospital care has been seen by some as a single entity. As a result, experience from well resourced first world trauma centres has been taken, by many, to be applicable to all prehospital situations. This article attempts to assist in the development of valid EMS indicators of performance and effectiveness by categorising prehospital scenarios into a classification reflecting the reality of their conditions of practice.

Elevation of biochemical markers for myocardial damage prior to hospital admission in patients with acute chest pain or other symptoms raising suspicion of acute coronary syndrome

OBJECTIVES

To evaluate the occurrence of elevation of serum biochemical markers for myocardial damage in the prehospital setting amongst patients who called for an ambulance due to a suspected acute coronary syndrome (ACS).

DESIGN

Prospective observational study.

SUBJECTS

All the patients who called for an ambulance due to suspected ACS.

SETTING

South Hospital's catchment area in Stockholm and in the Municipality of Göteborg, Sweden between January and November in the year 2000, were included.

INTERVENTIONS

On arrival of the ambulance crew, a blood sample was drawn for bedside analysis of serum myoglobin, creatine kinase MB and troponin I. A 12-lead electrocardiogram (ECG) was simultaneously recorded.

MAIN OUTCOME MEASURES

Elevation of biochemical markers prior to hospital admission.

RESULTS

In all, 511 patients participated on 538 occasions. Elevation of any biochemical marker was observed in 11% of all patients. The corresponding figure for patients developing myocardial infarction was 21%; for patients with myocardial ischaemia 8%; for patients with a possible myocardial ischaemia 4% and for patients with other diagnoses 5%. Amongst those who had a final diagnosis of acute myocardial infarction (AMI), 47% had ST-elevation on initial ECG and 57% had either ST-elevation or elevation of any biochemical marker.

CONCLUSION

Bedside analysis of biochemical markers in serum is already feasible prior to hospital admission amongst patients with a suspected ACS. About 20% of patients with AMI have elevated biochemical markers at that stage. When found this data might increase the possibility of diagnosing an AMI very early in the course. However, false positives were found and whether this strategy will improve the triage of these patients in the prehospital setting remains to be proven.

Improved prognosis of patients presenting with clinical markers of spontaneous reperfusion during acute myocardial infarction

OBJECTIVE

To describe the clinical features, management, and prognosis of patients presenting with clinical markers of spontaneous reperfusion (SR) during acute myocardial infarction (AMI).

DESIGN

Cohort study.

SETTING

National registry of 26 coronary care units.

PATIENTS

2382 consecutive patients with AMI.

MAIN OUTCOME MEASURES

Patient characteristics, management, and mortality.

RESULTS

The incidence of SR was 4% of patients (n = 98) compared with thrombolytic treatment (n = 1163, 49%), primary angioplasty (n = 102, 4%), and non-reperfusion (n = 1019, 43%). SR patients were more likely to develop less or no myocardial damage as indicated by a higher percentage of non-Q wave AMI (58% v 32%, 47%, and 44%, respectively, p < 0.0001), aborted AMI (25% v 9%, 8%, and 12%, p < 0.001), and lower peak creatine kinase (503 v 1384, 1519, and 751 IU, p < 0.0001). SR patients, however, were more likely to develop recurrent ischaemic events (35% v 17%, 12%, and 16%, respectively; p < 0.001) and subsequently were more likely to be referred to coronary angiography (67%), angioplasty (41%), or bypass surgery (16%, p < 0.001). Mortality at 30 days (1% v 8%, 7%, and 13%, respectively, p < 0.0001) and one year (6% v 11%, 12%, and 19%, p < 0.0001) was significantly lower for SR patients than for the other subgroups. By multivariate analysis, SR remained a strong determinant of 30 day survival (odds ratio (OR) 0.16, 95% confidence interval (CI) 0.01 to 0.74). At one year, the association between SR and survival decreased (OR 0.49, 95% CI 0.18 to 1.13).

CONCLUSIONS

Clinical markers of SR are associated with greater myocardial salvage and favourable prognosis. The vulnerability of SR patients to recurrent ischaemic events suggests that they need close surveillance and may benefit from early intervention.

Early identification of patients with an acute coronary syndrome as assessed by dispatchers and the ambulance crew

This study was performed to evaluate the possibility of early identification of patients with an acute coronary syndrome who are transported by ambulance. All patients in the community of Göteborg who were transported by ambulance over a period of 3 months owing to symptoms raising any suspicion of an acute coronary syndrome were studied. In all 930 cases that were included in the survey, 130 (14%) had a final diagnosis of acute myocardial infarction (AMI) and 276 (30%) had a final diagnosis of an acute coronary syndrome. Independent risk indicators for development of AMI were: male sex (odds ratio 1.70; 95% confidence limits 1.02-2.84), cold and clammy on admission of the ambulance crew (odds ratio 2.07; 95% confidence limits 1.23-3.49) and showing electrocardiogram (ECG) signs of myocardial ischemia on admission to the emergency department (odds ratio 8.78; 95%confidence limits 5.28-14.61). Independent predictors for development of an acute coronary syndrome were: male sex (odds ratio 1.97; 95% confidence limits 1.30-2.99), a history of angina pectoris (odds ratio 3.41; 95% confidence limits 2.24-5.26), cold and clammy on admission of the ambulance crew (odds ratio 1.95; 95% confidence limits 1.21-3.15), and ECG signs of myocardial ischemia on admission to the emergency department (odds ratio 5.55; 95% confidence limits 3.63-8.58). Among patients seen by the ambulance crew with symptoms raising any suspicion of an acute coronary syndrome, predictors for that diagnosis included male sex, a history of angina pectoris, patients being cold and clammy on admission of the ambulance crew, and ECG signs of myocardial ischemia on admission to the emergency department.