Improved survival but not left ventricular function with early and prehospital treatment with tissue plasminogen activator in acute myocardial infarction

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.

Retrospective observational case-control study comparing prehospital thrombolytic therapy for ST-elevation myocardial infarction with in-hospital thrombolytic therapy for patients from same area

OBJECTIVES

To compare a system of prehospital thrombolytic therapy, delivered by paramedics under medical guidance, with in-hospital thrombolytic therapy in meeting National Service Framework (NSF) targets for treatment of acute myocardial infarction at a District General Hospital setting in England.

DESIGN

Retrospective observational case-control study comparing patients with suspected acute myocardial infarction (AMI) treated with thrombolytic therapy in the prehospital environment with patients treated in hospital.

SETTING

Wyre Forest District and Worcestershire Royal Hospital, UK.

PARTICIPANTS

(A) All patients who received prehospital thrombolytic therapy for suspected AMI accompanied by electrocardiographic features considered diagnostic.(B) Patients who received thrombolytic therapy after arrival at hospital for the same indication, matched with group A by age, gender and postcode.

MAIN OUTCOME MEASURES

1. Call to needle time. 2. Percentage of patients treated within one hour of calling for medical help. 3. Appropriateness of thrombolytic therapy. 4. Safety of thrombolytic therapy

RESULTS

1. The median call to needle time for patients treated before arriving in hospital (n = 27) was 40 minutes with an inter-quartile range 25-112 (mean 43 minutes). Patients from the same area who were treated in hospital (n = 27) had a median time of 106 minutes with an inter-quartile range 50-285 (mean 126 minutes). This represents a median time saved by prehospital treatment of 66 minutes. 2. 60 minutes after medical contact, 96 % of patients treated before arrival in hospital had received thrombolytic therapy; this compares with 4% of patients from similar areas treated in hospital. 3. Myocardial infarction was confirmed in 92% (25/27) of patients who received prehospital thrombolytic therapy and similarly 92% (25/27) of those given in-hospital thrombolytic therapy. 4. No major bleeding occurred in either group. Group A suffered fewer in-hospital deaths than group B (1 versus 4). Cardiogenic shock (3 patients) and ventricular arrhythmia (5 patients) were seen only in group B.

CONCLUSION

Paramedic-delivered thrombolytic therapy can be delivered appropriately, safely, and effectively. Time gains are substantial and can meet the national targets for early thrombolytic therapy in the majority of 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.

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 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.

Effect of prehospital thrombolysis on aborting acute myocardial infarction

On administering thrombolysis in a prehospital setting, we found a threefold increase in the incidence of abortion of myocardial infarction, compared with the in-hospital program of a nearby hospital. Assessment of aborted myocardial infarction may be a better criterion for the efficacy of early thrombolysis than mortality data.

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.

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.

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.

Early thrombolytic treatment in acute myocardial infarction: reappraisal of the golden hour

BACKGROUND

There is conclusive evidence from clinical trials that reduction of mortality by fibrinolytic therapy in acute myocardial infarction is related to the time elapsing between onset of symptoms and commencement of treatment. However, the exact pattern of this relation continues to be debated. This paper discusses whether or not appreciable additional gain can be achieved with very early treatment.

METHODS

The relation between treatment delay and short-term mortality (up to 35 days) was evaluated using tabulated data from all randomised trials of at least 100 patients (n = 22; 50,246 patients) that compared fibrinolytic therapy with placebo or control, reported between 1983 and 1993.

FINDINGS

Benefit of fibrinolytic therapy was 65 (SD 14), 37 (9), 26 (6) and 29 (5) lives saved per 1000 treated patients in the 0-1, 1-2, 2-3, and 3-6 h intervals, respectively. Proportional mortality reduction was significantly higher in patients treated within 2 h compared to those treated later (44% [95% CI 32, 53] vs 20% [15, 25]; p = 0.001). The relation between treatment delay and mortality reduction per 1000 treated patients was expressed significantly better by a non-linear (19.4-0.6x(+)29.3x-1) than a linear (34.7 - 1.6x) regression equation (p = 0.03).

INTERPRETATION

The beneficial effect of fibrinolytic therapy is substantially higher in patients presenting within 2 h after symptom onset compared to those presenting later.

The European Myocardial Infarction Project: an assessment of pre-hospital thrombolysis

The use of thrombolytic agents in patients with suspected myocardial infarction has been shown to reduce early and long-term mortality by about 20%, and it has been suggested that since time is an important factor, pre-hospital treatment would give better results. However, health deciders need reliable data on which to base future policies concerning this. The European Myocardial Infarction Project was a European Economic Community-supported double-blind study designed to evaluate the efficacy and safety of pre-hospital early thrombolytic treatment in patients with suspected myocardial infarction compared with the same treatment given later in a hospital setting. A total of 5469 patients in 16 countries were randomised by 198 mobile emergency units to receive either pre-hospital treatment with anistreplase, the thrombolytic agent used, followed by placebo after hospital admission (pre-hospital group; 2750 patients), or placebo followed by anistreplase (hospital group; 2719 patients). The median time delay between the injections was 55 min. A non-significant decrease in 30-day mortality was observed in favour of the pre-hospital group (13%: P = 0.08), whereas the decrease in cardiac death observed, also in favour of the pre-hospital group, was on the borderline of significance (16%; P = 0.049). Although some complications occurred more frequently in the pre-hospital group in the pre-hospital period, the overall incidence for serious complications was similar for both groups. These results show that the pre-hospital thrombolytic strategy in patients with suspected myocardial infarction is both effective and safe when performed by well-equipped well-staffed mobile emergency units.

Guidelines for the prehospital use of thrombolytic agents

Recognizing that prehospital thrombolytic therapy may provide benefit to certain subsets of patients, the routine prehospital use of thrombolytic agents should be discouraged pending further scientific delineation and documentation of those subgroups. ACEP encourages further investigation to document feasibility, efficacy, cost-effectiveness, and safety of use of these agents in this environment. Detailed education is needed in such areas as contraindications and the mechanics of drug administration. Online medical direction is paramount to the successful use of these agents in the prehospital setting.

Expanding indications for thrombolytic therapy in acute myocardial infarction. How late is too late, and how early is early: the clinician's view of the first 100 minutes

Proper understanding of the pathologic process of a ruptured plaque followed by thrombus formation, with acute assessment of the deranged pathophysiology of the coronary circulation as a sequel, remains the basis for rational therapy of cardiac ischemia. With the advent of better thrombolytic regimens, improved direct reperfusion via angioplasty, and streamlined recognition/admission procedures, therapeutic strategies for dealing with acute myocardial infarction have once more turned to the options for early therapy. From recent studies of out-of-hospital thrombolysis or immediate percutaneous transluminal coronary angioplasty, the position is reinforced that "early" means the first 100 minutes. It is hoped that the large Global Utilization of Streptokinase and t-PA for Occluded Arteries (GUSTO) study, which specifically analyses the effect of early reperfusion by optimal alteplase and actilyse (recombinant tissue-type plasminogen activator [rt-PA]) versus streptokinase regimens will confirm this essential concept once and for all. Thus, when appropriate therapy--depending in the local availability of facilities--is promptly given, further reductions in myocardial infarction size and ventricular dysfunction can be achieved, resulting in mortality rates < 5%, at substantial savings in ever more expensive healthcare resources. "Early is < 100 minutes; later may be too late or too costly."

Prehospital thrombolysis: beneficial effects of very early treatment on infarct size and left ventricular function

OBJECTIVES

The purpose of this study was to compare the effects of very early (< or = 1.5 h after symptom onset) and later (> 1.5 up to 4 h) thrombolytic therapy on infarct size, left ventricular function and early mortality in patients with acute myocardial infarction. To start thrombolysis at the earliest possible moment, it was performed in the prehospital setting. A cutoff time of 1.5 h was prospectively stipulated.

BACKGROUND

Shortening of ischemic time is crucial within the 1st 2 h. Prehospital thrombolysis can reduce time to treatment and enables very early initiation of therapy for many patients.

METHODS

One hundred seventy patients received 30 mg of anistreplase up to 4 h from symptom onset by a mobile intensive care unit physician. Infarct size was measured from cumulative release of alpha-hydroxybutyrate dehydrogenase, and left ventricular function was assessed by contrast angiograms 10 days after the infarction.

RESULTS

The decision to treat on scene was correct in 98% of patients. There were no bleeding complications or deaths outside the hospital setting. In 28 patients (17%) the ischemic process was interrupted. Findings with thrombolytic therapy initiated < or = 1.5 (96 patients) versus > 1.5 h (74 patients) were the following: initial extent of epicardial injury, 1.6 +/- 0.9 versus 1.4 +/- 0.7 mV, p = NS; infarct size by cardiac enzyme release 646 +/- 634 versus 886 +/- 712 IU/liter, p < 0.05; ejection fraction 57 +/- 14% versus 51 +/- 13%, p < 0.05; regional dyssynergic area 24 +/- 22 versus 33 +/- 24 U, p < 0.05; 21-day mortality 1 of 96 versus 5 of 74 patients (1% vs. 7%, p < 0.05).

CONCLUSIONS

The data suggest that in evolving myocardial infarction up to 4 h in duration, the start of thrombolytic therapy at < or = 1.5 h compared with > 1.5 h limits infarct size, preserves left ventricular function and may save lives.

Illusion of reperfusion. Does anyone achieve optimal reperfusion during acute myocardial infarction?

Thrombolytic therapy significantly improves the natural history of acute myocardial infarction, but recent data suggest that current reperfusion strategies have yet to realize the maximum potential for reduction of mortality and salvage of ventricular function. Coronary patency rates as high as 85% assessed by angiography 90 minutes after initiation of treatment greatly overestimate the efficacy of thrombolytic regimens, as this conventional angiographic "snapshot" view does not satisfactorily reflect the dynamic processes of coronary artery recanalization and reocclusion or the adequacy of myocardial perfusion. In fact, only the unusual patient appears to achieve optimal reperfusion for acute myocardial infarction, with a substantial deterioration of benefit in many patients due to insufficiently early or rapid recanalization, incomplete patency with TIMI grade 2 flow or critical residual coronary stenoses, absence of myocardial tissue reflow despite epicardial artery patency, intermittent coronary patency, subsequent reocclusion, or reperfusion injury. Recently developed techniques to critically assess the quality of reperfusion, coupled with the introduction of novel pharmacological agents and an improved understanding of the roles and mechanisms of existing thrombolytic and adjunctive drugs, have provided the opportunity to overcome many of the present limitations of reperfusion therapy. Emerging strategies to achieve optimal reperfusion are directed at enhancement of the velocity and quality of thrombolysis, amelioration of the adverse effects of reperfusion, and use of alternative pathways to myocardial salvage.

Prehospital thrombolytic therapy in patients with suspected acute myocardial infarction

BACKGROUND

The efficacy of thrombolytic therapy for acute myocardial infarction depends partly on how soon after the onset of symptoms it is administered. We therefore studied the efficacy and safety of thrombolytic therapy administered before hospital admission and thrombolytic therapy administered after admission in patients with suspected myocardial infarction.

METHODS

In a multicenter, double-blind study, patients seen within six hours of the onset of symptoms who had a qualifying 12-lead electrocardiogram were randomly assigned to receive either anistreplase before admission, followed by placebo in the hospital (prehospital group), or placebo before admission, followed by anistreplase in the hospital (hospital group). Prehospital therapy was administered by emergency medical personnel.

RESULTS

A total of 2750 patients were randomly assigned to the prehospital group, and 2719 to the hospital group. The patients in the prehospital group received thrombolytic therapy a median of 55 minutes earlier than those in the hospital group. We observed a nonsignificant reduction in overall mortality at 30 days in the prehospital group (9.7 percent vs. 11.1 percent in the hospital group; reduction in risk, 13 percent; 95 percent confidence interval, -1 to 26 percent; P = 0.08). Death from cardiac causes was significantly less frequent in the prehospital group than in the hospital group (8.3 percent vs. 9.8 percent; reduction in risk, 16 percent; 95 percent confidence interval, 0 to 29 percent; P = 0.049). Particular adverse events occurred more frequently in the prehospital group during the period before hospitalization; among these events were ventricular fibrillation (P = 0.02), shock (P < 0.001), symptomatic hypotension (P < 0.001), and symptomatic bradycardia (P = 0.001). With the exception of symptomatic hypotension, however, the overall incidence of these events was similar for both groups.

CONCLUSIONS

Prehospital thrombolytic therapy for patients with suspected myocardial infarction is both feasible and safe when administered by well-equipped, well-trained mobile emergency medical staff. Although such therapy appears to reduce mortality from cardiac causes, our data do not definitely establish that it reduces overall mortality.

Congestive heart failure in coronary artery disease

Congestive heart failure (CHF) affects approximately 1% of the United States population and its incidence continues to increase. Next to hypertension, coronary artery disease (CAD) is the second most frequent cause of CHF. Important distinction should be made between systolic dysfunction and diastolic dysfunction in CAD. The diagnostic and therapeutic challenges posed by both have stimulated much investigation into the pathophysiologic mechanisms involved and have led to innovative pharmacologic interventions to forestall progression of the disease. The challenge in the 1990s is prevention. In the meantime, results of completed and ongoing randomized controlled trials will determine the most effective forms of therapy, which will not only improve symptoms but also hopefully extend survival.

Acute phase reaction, infarct size and in-hospital morbidity in myocardial infarction patients treated with streptokinase or recombinant tissue type plasminogen activator

We examined the acute phase reaction in myocardial infarction after thrombolytic treatment by streptokinase or tissue plasminogen activator. The magnitude of the acute phase reaction as determined by measurements of serum C-reactive protein and amyloid-A protein did not correlate with infarct size (determined by serial measurements of creatine kinase-MB) in this patient population. On the other hand, the development of acute cardiac failure was more closely associated with the magnitude of the acute phase reaction than with infarct size. The peak serum values of C-reactive protein in patients with and without acute cardiac failure were 128 mg/l (95% confidence intervals 85-170) and 60 mg/l (30-89); P less than 0.01 and concentration time integrals 578 mg/l x days (368-787) and 205 mg/l x days (62-350); P less than 0.01. The corresponding creatine kinase-MB values were 310 U/l (191-429) and 207 U/l (125-289) not significant; and 319 U/l x days (201-437) and 204 U/l x days (124-286) not significant; respectively. Patients requiring medication for cardiac failure on discharge from hospital had higher C-reactive protein and serum amyloid A protein values than those who did not, although the difference did not quite reach statistical significance. The infarct sizes were similar whether the patients needed medication for cardiac failure at discharge or not. Subjectively felt morbidity due to myocardial infarction was linearly associated with serum C-reactive protein peak values (P less than 0.05) and concentration time integrals (P less than 0.05), but not with infarct size. We conclude that thrombolytic treatment of myocardial infarction may reduce hospital inpatient morbidity independently of the limitation of infarct size. This diminished morbidity seems to be associated with modest or low acute phase reaction.