Prehospital thrombolysis in acute myocardial infarction

[Out-of-hospital emergency medicine in Germany, Austria and Switzerland : randomized prospective studies from 1990 to 2012]

BACKGROUND

Only randomized clinical trials can improve the outcome of life-threatening injuries or diseases but observations from England and North America suggest that the number of such randomized clinical trials is decreasing. In this study contributions from German speaking countries with regards to randomized clinical trials in emergency medicine over the last 22 years were investigated.

METHODS

The Medline database was searched from January 1990 to December 2012 for prospective randomized clinical trials in the prehospital setting using the criteria "cardiac arrest", "cardiopulmonary resuscitation", "multiple trauma", "hemorrhagic shock", "head trauma", "stroke" as well as myocardial infarction and emergency medical service. Only studies originating from Germany, Austria or Switzerland were included.

RESULTS

A total of 474 studies were found and 25 studies (5.3 %) fulfilled the inclusion criteria. In the last 22 years German speaking countries have published approximately one prospective, randomized, clinical trial per year on prehospital emergency medicine. The median number of patients included in the trials was 159 (minimum 16, maximum 1,219). Most (80 %) studies originated from Germany and most (64 %) studies were conducted by anesthesiology departments. Cardiac arrest was the most frequent subject of the investigated studies. Approximately 50 % of the studies had financial support from industrial companies.

CONCLUSION

A significant increase or decrease in the number of prospective randomized clinical trials in the out-of-hospital setting could not be found in German speaking countries despite the fact that the absolute numbers of studies had increased. Only about one prospective, randomized clinical trial with an emergency medicine core tracer diagnosis originated from Germany, Austria and Switzerland per year.

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.

Determining the Feasibility of Ambulance-Based Randomised Controlled Trials in Patients with Ultra-Acute Stroke: Study Protocol for the "Rapid Intervention with GTN in Hypertensive Stroke Trial" (RIGHT, ISRCTN66434824)

Background. Time from acute stroke to enrolment in clinical trials needs to be reduced to improve the chances of finding effective treatments. No completed randomised controlled trials of ambulance-based treatment for acute stroke have been reported in the UK, and the practicalities of recruiting, consenting, and treating patients are unknown. Methods. RIGHT is an ambulance based, single-blind, randomised controlled trial with blinded-outcome assessment. The trial will assess feasibility of using ambulance services to deliver ultra-acute stroke treatments; a secondary aim is to assess the effect of glyceryl trinitrate (GTN) on haemodynamic variables and functional outcomes. Initial consent, randomisation, and treatment are performed by paramedics prior to hospitalisation. Patients with ultra-acute stroke (≤4 hours of onset) are randomised to transdermal GTN (5 mg/24 hours) or gauze dressing daily for 7 days. The primary outcome is systolic blood pressure at 2 hours. Secondary outcomes include feasibility, haemodynamics, dependency, and other functional outcomes. A nested qualitative study is included. Trial Status. The trial has all relevant ethics and regulatory approvals and recruitment started on February 15, 2010. The trial stopped recruitment in December 2011 after 41 patients were recruited. Trial Registration. The trial registration number is ISRCTN66434824 and EudraCT number is 2007-004766-40.

Prehospital strategies to expedite myocardial salvage

Recent large-scale clinical investigations have shown the overwhelming importance of early intervention in acute myocardial infarction (AMI), thereby underlining the crucial role of emergency medical technician-paramedics (EMT-Ps) in helping to assess and treat heart attack victims. Some of these studies have included administration of thrombolytic drugs by paramedics. Emergency medical service teams equipped with 12-lead ECGs, diagnostics, checklists, and 2-way communications are becoming the standard in many communities in developed countries and help reduce in-hospital delays in diagnosis. Together with newer diagnostic hardware and software, novel thrombolytics that are rapid and easy to administer will help paramedics overcome current bottlenecks to the expeditious delivery of life-saving care to AMI victims. Public awareness programs as suggested by the American College of Cardiology/American Heart Association (ACC/AHA) guidelines are essential to enlist support for government funding of emergency medical services that can frequently mean the difference between life and death.

The role of fibrinolytics in the prehospital treatment of ST-elevation myocardial infarction (STEMI)

The efficacy of fibrinolytics in the treatment of ST-elevation myocardial infarction is directly related to the time of administration, with the first 2 h after symptom onset seen as a critical period for greatest improvement in cardiovascular parameters and mortality. The American College of Cardiology/American Heart Association recommends a medical contact to treatment time of 30 min for fibrinolysis in patients with ST-elevation myocardial infarction. In selected patients, reperfusion goals may be expedited with prehospital administration of fibrinolytics. In clinical trials, prehospital fibrinolysis markedly reduced the time from symptom onset to treatment, allowed earlier ST-segment resolution, and reduced short- and long-term mortality compared with in-hospital treatment. Prehospital fibrinolysis has become more feasible with the introduction of prehospital 12-lead electrocardiography, improved skills of emergency medical services personnel, improved communication with the Emergency Department, and the advent of bolus fibrinolysis. Rapid and accurate administration of a fibrinolytic is vital for the success of prehospital fibrinolysis.

Time to reperfusion in acute myocardial infarction. It is time to reduce it!

BACKGROUND AND OBJECTIVES

Mortality from ST-segment elevation myocardial infarction remains high, with most deaths occurring before hospital admission. Despite effective pre- and in-hospital reperfusion strategies becoming standard over the past 2 decades, time-to-admission and time-to-treatment remain prolonged. We reviewed temporal trends in these times in published clinical trials.

METHODS

All major randomized clinical trials reporting on reperfusion strategies for acute myocardial infarction published between 1993 and 2003 were evaluated. Strategies included pre- and in-hospital thrombolysis, primary percutaneous coronary intervention (pPCI) with or without transfer, and "facilitated" PCI. We generated overall estimates of time-to-admission, time-to-treatment, door-to-balloon (DTB), and door-to-needle (DTN) times and evaluated temporal trends in the length of time-to-admission and time-to-treatment.

RESULTS

In studies that evaluated only in-hospital thrombolysis, the time-to-admission was 149 +/- 45 minutes; the mean time-to-treatment was 181 +/- 29 minutes. In studies that considered only in-hospital pPCI (without transfer), the mean time-to-admission was 153 +/- 41 minutes; the mean time-to-treatment was 234 +/- 43 minutes. In studies that compared in-hospital pPCI with in-hospital thrombolytic therapy, the mean time-to-admission was 155 +/- 47 and 150 +/- 48 minutes, respectively. The DTN time was 65 +/- 10 minutes, whereas DTB time was 81 +/- 39 minutes. In other trials evaluating in-hospital thrombolysis and pPCI with transfer to a referral center, the time-to-admission in subjects treated with thrombolysis (n = 1345) was 127 +/- 32 minutes vs 131 +/- 36 minutes for pPCI (n = 1528). For in-hospital thrombolysis, time-to-treatment was 151 +/- 23 minutes vs 203 +/- 15 minutes for pPCI patients with transfer. The DTN time in the thrombolysis group was 44 +/- 28 minutes as compared with DTB time of 78 +/- 38 minutes in the pPCI group. Throughout the last decade, time-to-admission decreased significantly (P = .02) but time-to-treatment remained unchanged (P = .38) for patients undergoing thrombolysis. In the pPCI arm, time-to-admission remained unchanged (P = .11) but a insignificant trend toward reduction was demonstrated in time-to-treatment (P = .11).

CONCLUSION

Time-to-admission and time-to-treatment for ST-segment elevation myocardial infarction are still prolonged. Resources should be directed to early recognition of the acute myocardial infarction, improved utilization of emergency services for transportation, and prehospital diagnosis and triaging. Ambulances equipped with wireless capability to transmit electrocardiograms to the on-call cardiologist seem to be promising tools to achieve earlier diagnosis and triaging with high diagnostic sensitivity and specificity.

Diagnostic performance and potential clinical impact of advanced care paramedic interpretation of ST-segment elevation myocardial infarction in the field

OBJECTIVES

Most studies of pre-hospital management of ST-elevation myocardial infarction (STEMI) have involved physicians accompanying the ambulance crew, or electrocardiogram (ECG) transmission to a physician at the base hospital. We sought to determine if Advanced Care Paramedics (ACPs) could accurately identify STEMI on the pre-hospital ECG and contribute to strategies that shorten time to reperfusion.

METHODS

A STEMI tool was developed to: 1) measure the accuracy of the ACPs at diagnosing STEMI; and 2) determine the potential time saved if ACPs were to independently administer thrombolytic therapy. Using registry data, we subsequently estimated the time saved by initiating thrombolytic therapy in the field compared with in-hospital administration by a physician.

RESULTS

Between August 2003 and July 2004, a correct diagnosis of STEMI on the pre-hospital ECG was confirmed in 63 patients. The performance of the ACPs in identifying STEMI on the ECG resulted in a sensitivity of 95% (95% confidence interval [CI] 86%-99%), a specificity of 96% (95% CI 94%-98%), a positive predictive value (PPV) of 82% (95% CI 71%-90%), and a negative predictive value (NPV) of 99% (95% CI 97%-100%). ACP performance for appropriately using thrombolytic therapy resulted in a sensitivity of 92% (95% CI 78%-98%), a specificity of 97% (95% CI 94%-98%), a PPV of 73% (95% CI 59%-85%) and an NPV of 99% (95% CI 97%-100%). We estimated that the median time saved by ACP administration of thrombolytic therapy would have been 44 minutes.

CONCLUSIONS

ACPs can be trained to accurately interpret the pre-hospital ECG for the diagnosis of STEMI. These results are important for the design of regional integrated programs aimed at reducing delays to reperfusion.

Comparison of early mortality of paramedic-diagnosed ST-segment elevation myocardial infarction with immediate transport to a designated primary percutaneous coronary intervention center to that of similar patients transported to the nearest hospital

Speed of reperfusion is critical in ST-segment elevation myocardial infarction (STEMI). We assessed the safety and feasibility of an integrated metropolitan approach in which advanced-care paramedics interpret the prehospital electrocardiogram and independently refer patients with STEMI to a designated center for primary percutaneous coronary intervention (PCI). We developed and implemented a protocol in which paramedics trained in electrocardiographic interpretation bypassed the nearest emergency room and referred patients with suspected STEMI directly to a designated primary PCI center (paramedic-referred primary PCI). Outcomes of these patients were compared with those of a retrospective cohort of 225 consecutive patients with STEMI transported by ambulance to the nearest hospital emergency department. We treated 108 consecutive patients with STEMI using ambulance services according to the paramedic-referred primary PCI protocol. Primary PCI was performed in 93.5% versus 8.9% in the control group, and the median door-to-balloon time was 63 versus 125 minutes in the control group (p <0.0001 for 2 comparisons). Thrombolytic therapy was prescribed to 80.4% of the control group, with a median door-to-needle time of 41 minutes. In-hospital mortality was 1.9% in the paramedic-referred primary PCI group versus 8.9% in the control group (p = 0.017) and remained significantly lower after statistical adjustment for baseline risk. In conclusion, paramedic-referred primary PCI is a safe and feasible strategy for treating STEMI that is associated with rapid and effective reperfusion and very low in-hospital mortality.

Paramedics and pre-hospital management of acute myocardial infarction: diagnosis and reperfusion

In this paper, we discuss and critically analyse pre-hospital management of acute myocardial infarction (AMI). It is clear from several large studies that rapid diagnosis and application of thrombolysis reduces morbidity and mortality rates. Strategies that improve time to treatment in the pre-hospital setting are therefore of fundamental importance in the management of this fatal disease. The advantage of 12 lead electrocardiography use by paramedics to diagnose AMI and reduce time to treatment is discussed. Moreover, paramedic application of thrombolysis in the pre-hospital environment is examined. Several studies conducted worldwide support the notion that ambulance services can play a role in minimising time to treatment for patients with AMI. The contribution of early intervention by paramedics trained in critical care is potentially considerable, particularly in the important chain of survival that is often initiated by pre-hospital intervention.

[Acute coronary syndrome in the prehospital phase]

Cardiovascular diseases are the number one cause of death in Germany. In 2002 about 70,000 people died of acute myocardial infarction (AMI) and of these 37% died before arrival at hospital which underlines the relevance of adequate prehospital care. The generic term acute coronary syndrome (ACS) was introduced because a single pathomechanism accounts for the different forms and comprises unstable angina pectoris (iAP), non-ST-elevation myocardial infarction (NSTEMI), ST-elevation myocardial infarction (STEMI) and sudden cardiac death (SCD). Characteristic features are retrosternal pain, vegetative symptoms and radiation of pain into the adjoining regions. Further differentiation can only be achieved by the 12-lead ECG, as cardiac-specific enzymes do not play a role in prehospital decisions. Prehospital delays should be avoided, history and physical examination should be brief but focused, vital parameters should be assessed and monitored. Basic treatment for ACS should comprise inhalative oxygen, nitrates, morphine, aspirin and beta-blockers. If STEMI is diagnosed, patients with symptoms <12 h should undergo fibrinolytic therapy unless there is primary percutaneous coronary intervention (PCI) available within 90 min or if contraindicated. Heparin should be given to patients with STEMI depending on the choice of fibrinolytic agent, it otherwise results in a higher risk of bleeding, but in patients with iAP or NSTEMI it reduces mortality. All patients must be accompanied by the emergency physician during transportation and should be brought to a hospital with primary PCI, especially those with complicated ACS. Treatment of complications depends largely on the type, persistence and severity.

Quality of life of elderly patients after prehospital thrombolytic therapy

We studied the long-term outcome and quality of life of elderly patients after prehospital thrombolysis to treat acute ST-elevation myocardial infarction. Data of 218 patients after prehospital thrombolytic therapy given by two physician staffed Helicopter Emergency Medical Service (HEMS) units were collected prospectively. Physical and mental status was evaluated at 4--6 months after discharge, and 1-year mortality was determined. Patients older than 65 years were compared with those younger than 65 years. There were 112 elderly and 106 younger patients. The elderly patients had more previous coronary events and more medications. Pain to therapy times between the two groups were equal (<65 years: 108+/-93 min (range 27--500 min) versus >65 years: 108+/-70 min (20-357 min)). After 4--6 months, the Barthel Daily Living Index or the Beck Depression Inventory (BDI) (depression, if BDI >/=10) showed no differences between the two groups (<65 years: 99+/-5 (range 65--100) versus >65 years: 98+/-12 (10--100); BDI>/=10, 18% versus 9%). One-year survival was lower among the elderly (79% versus 93%; p=0.001). No differences in the frequency of arrhythmias, haemodynamic problems during thrombolysis or complications such as intracranial haemorrhage after thrombolysis were detected. We concluded that elderly patients treated with prehospital thrombolysis for acute ST-elevation myocardial infarction recover mentally and physically as well as younger patients.

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.

Beneficial effects of direct call to emergency medical services in acute myocardial infarction

OBJECTIVES

We investigated the impact of an emergency medical services call on the management of acute myocardial infarction, considering time intervals for intervention and revascularization procedures.

METHODS

Data were prospectively collected from January 2001 to October 2002 from 531 patients hospitalized for myocardial infarction with ST segment elevation and a pre-hospital delay of less than 24 h.

RESULTS

Only 26% of patients called the emergency medical services at the onset of symptoms (n=140). Other patients (n=391, 74%) called another medical contact. Baseline characteristics and cardiovascular history were similar in the two groups, except for the percutaneous coronary intervention history (10% in the emergency medical services group versus 4% in the other medical contact group, P<0.05). Time intervals from the onset of symptoms of myocardial infarction to call or to medical intervention, as well as the time interval from medical intervention to hospital admission were significantly shorter in the emergency medical services group. The early reperfusion rate was also significantly greater in the emergency medical services group (77%) compared with the other medical contact group (64%), mainly because of a greater incidence of primary percutaneous coronary intervention (36 versus 26%, P<0.03, respectively). Multivariate analysis adjusted for sex and age showed that less than three medical care providers [odds ratio (OR) 5.042, P<0.001], percutaneous coronary intervention history (OR 2.462, P<0.05), as well as rhythmic disorders (OR 2.105, P<0.05) and complete atrioventricular block (OR 2.757, P<0.05) were independent predictors of emergency medical services care.

CONCLUSION

This study demonstrated that a call to the emergency medical services is underutilized by patients with symptoms of myocardial infarction, and documented the beneficial effects of an emergency medical services call by reducing pre-hospital delays and increasing early revascularization therapies.

Effectiveness of a medical priority dispatch protocol for abdominal pain

OBJECTIVE

Medical Priority Dispatch System (MPDS) protocols are used to determine the appropriate level of emergency medical services (EMS) response that is sent to care for patients in the prehospital setting. The objective of this study was to determine the proportion of patients with abdominal pain who would benefit from advanced life support (ALS) when called for by these protocols.

METHODS

All 9-1-1 calls were processed using MPDS protocols to determine whether the patient required ALS or basic life support (BLS) services. Consecutive patients having an ALS response for a chief complaint of abdominal pain were included. Dispatch decisions that did not follow the MPDS protocols, and cases taken to facilities other than the primary study hospitals, were excluded. EMS run sheets and hospital records were reviewed to determine: 1) whether prehospital ALS interventions were required, 2) emergency department (ED) disposition, 3) hospital course, and 4) final diagnosis. Calls were classified according to the need for ALS and the seriousness of the subsequent diagnosis. Data analysis was performed by determining 95%, confidence intervals (CIs).

RESULTS

Of the 343 patients classified as 1C1 or 1C2 who were transported by ALS during the time period, 227 (67%) were transported to the study hospitals. Nine (4%) were excluded because of inappropriate dispatch, leaving 218 for analysis. Hospital records were available for 186 (86%) cases, of which 12 (6%; CI 3%, 9%) were potentially life-threatening, requiring ALS intervention. Seventeen (9%; CI 5%, 1%) were non-life-threatening, but potentially benefited from ALS intervention. The remaining 157 (84%; CI 79%, 89%) were classified as not requiring ALS.

CONCLUSIONS

Use of age- and gender-specific MPDS protocols for patients with a chief complaint of abdominal pain results in significant overtriage and overuse of ALS. Steps should be taken to develop key questions that provide more accurate classification of these patients that goes beyond age and gender classification alone.

Evaluation of the time saved by prehospital initiation of reteplase for ST-elevation myocardial infarction: results of The Early Retavase-Thrombolysis in Myocardial Infarction (ER-TIMI) 19 trial

OBJECTIVES

The Early Retavase-Thrombolysis In Myocardial Infarction (ER-TIMI) 19 trial tested the feasibility of prehospital initiation of the bolus fibrinolytic reteplase (rPA) and determined the time saved by prehospital rPA in the setting of contemporary emergency cardiac care.

BACKGROUND

Newer bolus fibrinolytics have undergone only limited evaluation for prehospital administration. In addition, as door-to-drug times have decreased, the relevance of findings from prior trials of prehospital fibrinolysis has become less certain.

METHODS

Patients (n = 315) with ST-elevation myocardial infarction (STEMI) were enrolled in 20 emergency medical systems in North America. The time from emergency medical service (EMS) arrival to administration of a fibrinolytic was compared between study patients receiving prehospital rPA and sequential control patients from 6 to 12 months before the study who received a fibrinolytic in the hospital.

RESULTS

Acute myocardial infarction was confirmed in 98%. The median time from EMS arrival to initiation of rPA was 31 min (25th to 75th percentile, 24 min to 37 min). The time from EMS arrival to in-hospital fibrinolytic for 630 control patients was 63 min (25th to 75th percentile, 48 min to 89 min), resulting in a time saved of 32 min (p < 0.0001). By 30 min after first medical contact, 49% of study patients had received the first bolus of fibrinolytic compared with only 5% of controls (p < 0.0001). In-hospital mortality was 4.7%. Intracranial hemorrhage occurred in 1.0%.

CONCLUSIONS

Prehospital administration of rPA is a feasible approach to accelerating reperfusion in patients with STEMI. Valuable time savings can be achieved in the setting of contemporary transport and door-to-drug times and may translate into an improvement in clinical outcomes.

Feasibility and timing of prehospital administration of reteplase in patients with acute myocardial infarction

BACKGROUND

In myocardial infarction patients undergoing thrombolysis, treatment delays negatively impact outcomes. This pilot study was conducted to determine the feasibility and timing of field administration of intravenous double bolus reteplase in patients with ST-elevation myocardial infarction.

METHODS

Sixty three patients with symptoms and EKG changes consistent with acute myocardial infarction of less than six hours duration received the first bolus of reteplase before arriving at the emergency department. A second bolus of reteplase was given in the emergency department. Subsequent resolution of ST-segment elevation was measured. Mean time from symptom onset to paramedic dispatch, and paramedic arrivals to first bolus of reteplase were measured. The mean time from the first bolus of reteplase to heparin bolus in an emergency department was also measured. All patients with evidence of ST-elevation and suspected acute myocardial infarction gave consent for the thrombolytic therapy. There were no refusals of therapy among those candidates eligible for thrombolysis.

RESULTS

The mean times from the first bolus of reteplase to heparin bolus in the emergency department was substantially longer than the in-field times. Resolution of ST-segment elevation was recorded in 52 of the 63 patients and the times of resolution ranged from five minutes after the first bolus dose to 190 minutes after the second bolus of reteplase. Resolution of ST-segment elevation and relief of pain occurred almost simultaneously.

CONCLUSIONS

These results demonstrated that in-field administration of thrombolytic therapy is a viable option to reduce the delay from symptom onset to initiation of thrombolysis. They demonstrated that satisfactory resolution of ST-segment elevation can be recorded in the field. The reduction in mortality observed in this study is comparable to previously published studies on inpatients.

Acute ischemic syndromes. Early response

The optimal treatment of patients with AIS depends on a well-run, integrated system of care involving patients and teams of health care professionals. It begins with patient education and extends to a method for accessing an efficient and effective EMS system. Medics must be well equipped and well trained to evaluate and begin initial treatment during prompt transport to an appropriate hospital. The role of out-of-hospital 12-lead ECGs and thrombolysis is reviewed and may be appropriate for some EMS systems. The initial evaluation and treatment in the ED goes on simultaneously and is a dynamic process. Prompt treatment with oxygen, nitroglycerin, morphine, and aspirin is indicated. Initial risk stratification is based on the first ECG, cardiac biomarkers, and the clinical history and physical exam. Disposition and further evaluation is individualized according to the initial work-up and risk assessment.

[Beneficial effects of direct call to Emergency Medical Services on time delays and management of patients with acute myocardial infarction. The RICO (obseRvatoire des Infarctus de Côte-d'Or) data]

The influence of direct calls to specialized Emergency Medical Services in case of suspected myocardial infarction has not been extensively studied. The RICO registry is an exhaustive registry implemented in all six institutions participating in primary care of patients with acute myocardial infarction in one French administrative department (Côte-d'Or). From January 2001 to October 2001, 322 patients were admitted for acute myocardial infarction, among whom only 57 (18%) had directly called emergency medical services after the onset of symptoms. The baseline characteristics of patients who had directly called the emergency services were not different from those of the patients who had not. However, the time from symptom onset to first medical intervention (48 versus 105 minutes, p = 0.02) and from first medical intervention to hospital admission (60 versus 103 minutes, p = 0.02) were markedly shorter in patients who had directly called the emergency medical services. This resulted in a significant increase in the use of reperfusion therapy (70% versus 38%, p = 0.003), including a higher proportion of primary angioplasty (33% versus 20%, p = 0.04). This study documents the beneficial effect of a direct call to the Emergency Medical Services by the patients themselves. Too few patients, however use this opportunity and actions should be taken for informing the lay public of the benefits of this medical service.

Prehospital thrombolysis in acute myocardial infarction

Efficacy of reperfusion therapy in acute myocardial infarction (AMI) is strictly time-dependent. Most benefit is achieved with initiation of therapy within the first 60-90 min after onset of symptoms. The majority of patients with AMIs are seen within this time window by emergency medical services. Moreover, average time gain of about 60 min is possible by prehospital thrombolysis. Randomized studies yielded a better outcome when a time gain of 90 min and more was achieved. Prehospital diagnosis of AMI is reliable. Moreover, out-of-hospital thrombolysis has no additional specific risks nor is it an obstacle for later percutaneous intervention. Consequently, patients seen within the first 60-90 min after onset of symptoms or for whom a time gain of 90 min or more can be expected should receive immediate prehospital thrombolysis.

Accuracy and clinical effect of out-of-hospital electrocardiography in the diagnosis of acute cardiac ischemia: a meta-analysis

STUDY OBJECTIVE

We sought to evaluate quantitatively the evidence on the diagnostic performance of out-of-hospital ECG for the diagnosis of acute cardiac ischemia (ACI) and acute myocardial infarction (AMI) and the clinical effect of out-of-hospital thrombolysis.

METHODS

We conducted a systematic review and meta-analysis of the English-language literature published between 1966 and December 1998 on the diagnostic accuracy of out-of-hospital ECG and the clinical effect of out-of-hospital thrombolysis. Both prospective and retrospective studies qualified for the assessment of diagnostic performance. For clinical effect, data from prospective nonrandomized studies were synthesized separately from data from randomized trials. Diagnostic performance was assessed by using estimates of test sensitivity, specificity, and diagnostic odds ratios and was summarized by using summary receiver-operating characteristic curves. Measures of clinical effect included time savings, early ventricular function, early mortality, and long-term survival.

RESULTS

Diagnostic accuracy was evaluated in 11 studies with a total of 7,508 patients. Data were available for ACI in 5 studies and for AMI in 8 studies. For ACI, the random-effects pooled sensitivity was 76% (95% CI, 54% to 89%), the specificity was 88% (95% CI, 67% to 96%), and the diagnostic odds ratio was 23 (95% CI, 6.3 to 85). The respective figures for AMI were sensitivity of 68% (95% CI, 59% to 76%), specificity of 97% (95% CI, 89% to 92%), and diagnostic odds ratio of 104 (95% CI, 48 to 224). Both in nonrandomized (n=4, total 1,531 patients) and randomized (n=9, total 6,643 patients) studies, out-of-hospital thrombolysis shortened the time from onset of symptoms to thrombolytic treatment by 40 to 60 minutes. Data on short-term ejection fraction were sparse. Hospital mortality was reduced by 16% (95% CI, 2% to 27%) among randomized trials, and a similar estimate of effect was seen in nonrandomized studies. There was no clear effect on long-term mortality, but data were sparse.

CONCLUSION

Out-of-hospital ECG has excellent diagnostic performance for AMI and very good performance for ACI. Out-of-hospital thrombolysis achieves time savings and improves short-term mortality, but the effect on long-term mortality is unknown.

Medical treatment for acute coronary syndromes

The medical treatment of acute coronary syndromes with thrombolytic, antithrombin, and antiplatelet agents is a major area of research and a vast topic for clinical review. This review summarizes important recent findings on the background of existing pathological and clinical knowledge to provide an understanding of the basis of current therapy and the new therapies that are likely to be introduced in the near future. Current controversies regarding the management of these conditions and the choice between medical, interventional, and combined strategies in different situations are also discussed.

Pre-hospital thrombolysis

The administration of thrombolytic drugs outside hospital by emergency physicians is becoming more common. However, few in Europe live in areas where such a service is provided. The data suggest that the advantages can be appreciable in some circumstances but that the strategy may not be universally applicable.

A matched comparison of the combination of prehospital thrombolysis and standby rescue angioplasty with primary angioplasty

This study sought to assess the rate of acute Thrombolysis In Myocardial Infarction (TIMI) trial grade 3 patency that can be achieved with the combination of prehospital thrombolysis and standby rescue angioplasty in acute myocardial infarction. No large angiographic study has been performed after prehospital thrombolysis to determine the 90-minute TIMI 3 patency rate in the infarct-related artery. Hospital outcome and artery patency were compared to 170 matched patients treated with primary angioplasty. Prehospital thrombolysis was applied 151+/-61 minutes after the onset of pain in 170 patients (56+/-12 years, 86% men), using recombinant tissue-type plasminogen activator, streptokinase, or eminase. Emergency 90-minute angiography was performed in every case. All patients in whom thrombolysis failed underwent rescue angioplasty. After thrombolysis alone, TIMI grade 3 flow in the infarct-related artery was observed in 108 patients (64%), TIMI grade 2 in 12 (7%), and TIMI grade 0 or 1 in 50 (29%). Rescue angioplasty was successful in 47 of 50 attempts. Overall, TIMI 3 patency was achieved in 91%, and additionally TIMI 2 flow in 7% of patients, an average of 113+/-39 minutes after thrombolysis and 55+19 minutes after admission. Therefore, < 2 hours after thrombolysis, only 2% of patients had persistent occlusion (TIMI 0 or 1) of the infarct-related artery. In-hospital mortality was 4% overall (7 of 170), and 3% in the 155 patients in whom TIMI 3 was obtained during the acute phase. Severe hemorrhagic complications occurred in 14 patients (8%) with 2 fatal cerebral hemorrhages (7% of patients required transfusions). The matched comparison with primary PTCA showed no significant difference in hospital outcome. Combined prehospital thrombolysis, 90-minute angiography, and rescue angioplasty yield a high rate of acute TIMI 3 patency rate early after thrombolysis and hospital admission. A randomized, prospective comparison between these 2 reperfusion strategies may be now warranted.

Searching for the evidence in pre-hospital care: a review of randomised controlled trials. On behalf of the Ambulance Response Time Sub-Group of the National Ambulance Advisory Committee

OBJECTIVES

To identify randomised controlled trials (RCTs) which evaluate aspects of pre-hospital care; to perform categorisation by theme; to compare the sensitivity and precision of the search databases.

DATA SOURCES

August 1997 updates of MEDLINE and EMBASE databases, using the Datastar online system. Papers published in 1987 or later were included, with no language restrictions.

STUDY SELECTION

A trial was eligible for inclusion if it was judged, by two independent and blinded assessors, that participants followed up in the trial were definitely or possibly assigned prospectively to one of two or more alternative forms of healthcare with random allocation or a quasi-random method of allocation.

RESULTS

The literature search retrieved 849 papers, of which 569 (67%) were in MEDLINE and 486 (57%) in EMBASE. Forty one (5%) were confirmed as reports of RCTs or quasi-RCTs, and the total number of individual trials was 38. Ten of these trials dealt with thrombolytic drugs; 14 were concerned with other drugs, 12 with equipment, and two with other interventions. Four trials were based on a sample size of more than 1000, and seven reported a statistically significant effect on mortality. All 41 papers were in EMBASE, and all but one were also in MEDLINE.

CONCLUSIONS

Evidence based policy making with respect to the organisation of pre-hospital services cannot depend on RCTs. In the current relative absence of such evidence, practitioners and decision makers must use alternative information sources. A future review could examine a broader range of literature and be based on a wider search of published and unpublished material.

Thrombolysis for acute myocardial infarction

Thrombolytic therapy has been a major advance in the management of acute myocardial infarction. Unfortunately, it continues to be underused or is administered later than is optimal. Thrombolytic therapy works by lysing infarct artery thrombi and achieving reperfusion, thereby reducing infarct size, preserving left ventricular function, and improving survival. The most effective thrombolytic regimens achieve angiographic epicardial infarct-artery patency in only approximately 50% of patients within 90 minutes. Bleeding requiring transfusion occurs in approximately 5% of patients and stroke in approximately 1.8% with these regimens, which include adjunctive aspirin and intravenous heparin. There are several ways in which reperfusion rates and thus patient outcomes might be improved, such as different dosing regimens of established agents; combinations of different agents; improved adjunctive therapy such as direct antithrombin agents, low-molecular-weight heparin, or glycoprotein IIb/IIIa receptor antagonists; or the development of novel thrombolytic agents with enhanced fibrin specificity, resistance to native inhibitors, or prolonged half-lives allowing bolus administration. All of these strategies are being tested in clinical trials. The best approach currently is to administer thrombolytic therapy as soon as possible to all patients without contraindications who present within 12 hours of symptom onset and have ST-segment elevation on the ECG or new-onset left bundle-branch block, unless an alternative reperfusion strategy is planned.

Thrombosis and Hemostasis in Cardiology: Review of Pathophysiology and Clinical Practice (Part I)

The adverse consequences of thrombosis are per haps nowhere more evident than in clinical cardiology. Throm bosis and hemostasis are primary issues in the management of patients with atrial fibrillation, prosthetic heart valves, severe left ventricular dysfunction, and coronary artery disease. Clini cal trials have defined a crucial role for anticoagulation with warfarin in patients with atrial fibrillation to reduce the inci dence of stroke. Anticoagulation with warfarin and aspirin in combination offers significant protection from systemic emboli in patients with mechanical prosthetic valves, without a sub stantial increased risk of hemorrhage. The risk of systemic emboli may also be reduced by anticoagulation in patients with severe left ventricular dysfunction. Disturbance of the normal balance of hemostasis is a major factor in the pathophysiology of coronary artery disease. Antiplatelet therapy, antithrombin agents, anticoagulants, and fibrinolytic agents have been used to prevent and treat acute coronary thrombosis and to prevent reocclusion following thrombolysis and interventional therapy. Guidelines are presented for antithrombotic therapy in the prac tice of clinical cardiology.

Prehospital-initiated thrombolysis

OBJECTIVE

To evaluate the feasibility, safety, and efficacy of prehospital-initiated thrombolysis in decreasing the mortality rate due to acute myocardial infarction.

DATA SOURCES

English-language clinical studies, abstracts, and review articles identified from MEDLINE searches and bibliographies of identified articles. Epidemiologic data were extracted from the Internet.

STUDY SELECTION

Eight randomized clinical trials and two meta-analyses that compared prehospital-initiated thrombolysis with in-hospital-initiated thrombolysis.

DATA EXTRACTION

Pertinent studies were selected and the data were synthesized into a review format.

DATA SYNTHESIS

Early reperfusion of an infarct-related coronary artery is associated with lower mortality rates. Most of the delay in initiating treatment is caused by patient delay rather than transport delay or hospital delay. In addition, more than 30% of eligible patients do not receive thrombolytic therapy. Prehospital initiation of thrombolysis has been evaluated as a means of decreasing hospital delay and increasing the number of eligible patients receiving thrombolysis. Clinical trials document that prehospital-initiated thrombolysis is feasible and safe, and saves time. Of the eight randomized trials, three demonstrated a decrease in either cardiac or total mortality with prehospital thrombolysis. All studies were limited by relatively small sample sizes. Two published meta-analyses suggest a 16-17% reduction in mortality with prehospital thrombolysis. In the US, prehospital thrombolysis is not routinely recommended due to medical issues related to diagnostic accuracy and monitoring, legal concerns, and economic implications. Additional strategies, such as community-wide education and prehospital diagnostic electrocardiograms (ECGs), are being studied.

CONCLUSIONS

In clinical trials, prehospital-initiated thrombolytic therapy was shown to be safe and probably more effective than in-hospital administration of thrombolytic therapy, but this has not proven feasible in the US at this time. Despite time-savings by decreasing treatment delay with prehospital-initiated thrombolysis, patient delay still persists and accounts for the majority of delay. Future investigations will center on increasing the number of patients treated with thrombolytic agents through patient education, in-patient and out-patient programs that rapidly identify eligible patients, as well as prehospital diagnostic ECGs.

The prehospital electrocardiogram in acute myocardial infarction: is its full potential being realized? National Registry of Myocardial Infarction 2 Investigators

OBJECTIVES

This study sought to examine the management and subsequent outcomes of patients with a prehospital electrocardiogram (ECG) in a large, voluntary registry of myocardial infarction.

BACKGROUND

The prehospital ECG has been proposed as a means of rapidly identifying patients with acute myocardial infarction who might be eligible for reperfusion therapy.

METHODS

The characteristics and outcomes of patients with a prehospital ECG were compared with those without a prehospital ECG in the National Registry of Myocardial Infarction 2 data base. Included in the analysis were those patients who presented to the hospital within 12 h of an acute myocardial infarction. Excluded were patients with an in-hospital infarction, transferred-in referrals and self-transported patients.

RESULTS

Prehospital ECGs were obtained in 3,768 (5%) of 66,995 National Registry of Myocardial Infarction 2 patients meeting study criteria. Median time from myocardial infarction symptom onset until hospital arrival was longer among those having a prehospital ECG (152 vs. 91 min, p < 0.001). However, once in the hospital, the prehospital ECG group experienced a shorter median time to the initiation of either thrombolysis (30 vs. 40 min, p < 0.001) or primary angioplasty (92 vs. 115 min, p < 0.001). The prehospital ECG group was more likely to receive thrombolytic therapy (43% vs. 37%, p < 0.001) and to undergo primary angioplasty (11% vs. 7%, p < 0.001). Also, the prehospital ECG group was more likely to undergo coronary arteriography (55% vs. 40%, p < 0.001), angioplasty (24% vs. 16%, p < 0.001) or bypass surgery (10% vs. 6%, p < 0.001). The in-hospital mortality rate was 8% in patients with a prehospital ECG and 12% in those without a prehospital ECG (p < 0.001). After adjusting for baseline covariates utilizing multiple logistic regression analysis, this mortality difference remained statistically significant (odds ratio 0.83, 95% confidence interval 0.71 to 0.96, p = 0.01).

CONCLUSIONS

The prehospital ECG is infrequently utilized for diagnosing myocardial infarction, and among patients with a prehospital ECG, is associated with a longer time from symptom onset to hospital arrival. Despite these shortcomings, the prehospital ECG is a test that may potentially influence the management of patients with acute myocardial infarction through wider, faster in-hospital utilization of reperfusion strategies and greater usage of invasive procedures, factors that may possibly reduce shortterm mortality. Efforts to implement the prehospital ECG more widely and more rapidly may be indicated.

An evaluation of the results of media and educational campaigns designed to shorten the time taken by patients with acute myocardial infarction to decide to go to hospital

OBJECTIVE

To describe the benefits and pitfalls of educational campaigns designed to reduce the delay between the onset of acute myocardial infarction (AMI) and its treatment.

METHODS

All seven educational campaigns reported between 1982 and 1994 were evaluated.

RESULTS

The impact on delay time ranged from a reduction of patient decision time by 35% to no reduction. One study reported a sustained reduction that resulted in the delay time being halved during the three years after the campaign. The use of ambulances did not increase. Only one study reported that survival was unaffected. There was a temporary increase in the numbers of patients admitted to the emergency department with non-cardiac chest pain in the initial phase of educational campaigns.

CONCLUSION

The challenge of shortening the delay between the onset of infarction and the start of treatment remains. The campaigns so far have not been proved to be worthwhile and it is not certain that further campaigns will do better. New media campaigns should be run to establish whether a different type of message is more likely to change the behaviour of people in this life-threatening situation.