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

Effect of ambulance 12-lead ECG recording on times to hospital reperfusion in acute myocardial infarction

OBJECTIVE

To review the evidence that recording a prehospital 12-lead electrocardiogram (ECG) reduces time from hospital arrival to initiation of reperfusion therapy for acute myocardial infarction (AMI).

DATA SOURCES

Medline search from 1966 to the present (articles in all languages) and examination of bibliographies.

STUDY SELECTION

Published studies of prehospital 12-lead ECG recording that included control groups and reported time intervals from hospital arrival to start of reperfusion therapy.

DATA EXTRACTION

Eight articles satisfied selection criteria (two randomised controlled trials, four non-randomised interventional studies and two prospective observational studies).

DATA SYNTHESIS

Widely varying study methodologies precluded meta-analysis. All studies had methodological problems, but hospital delays were consistently reduced. Such improvements appear to be small in hospitals where delays are already minimal.

CONCLUSIONS

Little evidence is available to support routine prehospital 12-lead ECG recording if the median hospital time to reperfusion is already less than 30 minutes. Improvement of in-hospital treatment times may be a better initial strategy than prehospital 12-lead ECG recording, as this will benefit more patients and allow ambulance services to better allocate their available resources.

[The clinical management guidelines of the Sociedad Española de Cardiología in acute myocardial infarct]

In the recent years, new possibilities have emerged in the diagnosis and management of acute myocardial infarction with ST segment elevation and its complications. Moreover, a deep transformation has taken place in the health care system organization, particularly in aspects related to care of patients presenting non-traumatic chest pain, both in pre-hospital and hospital areas. All these issues warrant a consensus document in Spain dealing with the role that these important changes should play in the whole management of myocardial infarction patients. This document revises and updates all the main clinical issues of acute myocardial infarction patients from the moment they contact with the health care system outside the hospital until they return home, after staying at the coronary care unit and the general hospitalization ward. All those aspects are considered not only in the uncomplicated myocardial infarction but also in the complicated one. This review also includes a set of recommendations on structural and organisational aspects, mainly referred to the prehospital and emergency levels.

A community hospital's effort to expedite treatment for patients with chest pain

OBJECTIVE

The purpose of this study was to determine treatment times at a community hospital that does not receive prehospital electrocardiogram (ECG) transmission and to determine the effect of time to first hospital ECG on overall door-to-drug time.

DESIGN

Descriptive.

SETTING

238-bed Regional Medical Center in Burlington, North Carolina.

SAMPLE

One hundred four patients with a final diagnosis of acute myocardial infarction were included in this 16-month study.

RESULTS

A median door-to-ECG time of 5 minutes was within the American College of Cardiology/American Heart Association recommendation of 10 minutes. Shorter treatment times to obtain the first ECG and initiate thrombolytic therapy were associated with younger patients and those arriving by ambulance.

CONCLUSIONS

While efficiency in obtaining a first hospital ECG on patients with suspected acute myocardial infarctions was achieved, this did not result in low door-to-drug times. Further streamlining of protocol and the exploration of prehospital initiatives may result in a significant reduction in door-to-drug times.

Prehospital ECG monitoring of chest pain patients

Prehospital electrocardiograms (ECGs) have been shown to decrease the time from onset of pain to onset of treatment. They are obtained prior to treatment while the patient is likely to have his/her most intense pain. With paramedics initiating care in the field, patient assessments may be clinically different by the time the patient reaches the hospital. Thus, obtaining an ECG as early as possible during treatment could aid in the access to treatment for the few patients whose ECGs improve with prehospital care. We present a case in which the prehospital presentation was indicative of an acute myocardial infarction (MI), whereas the presentation to the hospital was not as clear-cut. The patient was taken immediately to the catheterization laboratory based on the prehospital findings and was found to have an acute MI that was treated. Laboratory findings indicated that there was a significant improvement in patient outcome based on this early treatment. This case further illustrates the role of a prehospital ECG.

Evaluation of the efficacy of hand-held computer screens for cardiologists' interpretations of 12-lead electrocardiograms

BACKGROUND

Newly designed computer-based applications and the development of wireless technology have allowed the transmission of 12-lead electrocardiogram (ECG) waveforms from remote locations to the hand-held computers of cardiologists. If these computer ECGs can be reliably interpreted, then the time to treatment for cardiac patients may be reduced.

METHODS AND RESULTS

Twenty classic examples of cardiac abnormalities were chosen to test the efficacy of the hand-held computer's liquid crystal display (LCD) screen in the interpretation of 12-lead ECGs. Ten cardiologists interpreted these 20 ECGs on the hand-held computers and then twice later on traditional printed paper. The control intraobserver agreement between the sets of paper-displayed ECGs was measured against the agreement between each of the paper sets and the LCD-displayed set of ECGs. Eighty-nine percent (178/200) of the ECGs were interpreted identically by the participants between the 2 paper sets. When comparing the interpretations of the LCD-displayed ECGs with those of each of the paper sets of ECGs, 88.0% (176/200) and 87.5% (175/200) of identical diagnoses were noted. These differences of 1.0% and 1.5% in intraobserver agreement between paper-to-paper and each of the 2 paper-to-LCD comparisons were not significant (P =.75 and P =.88, respectively).

CONCLUSIONS

The strong intraobserver agreement shows that cardiologists make the same diagnoses when viewing LCD-displayed ECGs as they do when viewing paper-displayed ECGs. A study to measure the intraobserver agreement of the decision regarding administration of reperfusion therapy after interpretation of ECGs of patients with acute chest pain is now underway.

A comparison of the national registry of myocardial infarction 2 with the cooperative cardiovascular project

OBJECTIVES

This study was performed to evaluate whether or not the simpler case identification and data abstraction processes used in National Registry of Myocardial Infarction two (NRMI 2) are comparable with the more rigorous processes utilized in the Cooperative Cardiovascular Project (CCP).

BACKGROUND

The increased demand for quality of care and outcomes data in hospitalized patients has resulted in a proliferation of databases of varying quality. For patients admitted with myocardial infarction, there are two national databases that attempt to capture critical process and outcome data using different case identification and abstraction processes.

METHODS

We compared case ascertainment and data elements collected in Medicare-eligible patients included in the industry-sponsored NRMI 2 with Medicare enrollees included in the Health Care Financing Administration-sponsored CCP who were admitted during identical enrollment periods. Internal and external validity of NRMI 2 was defined using the CCP as the "gold standard."

RESULTS

Demographic and procedure use data obtained independently in each database were nearly identical. There was a tendency for NRMI 2 to identify past medical histories such as prior infarct (29% vs. 31%, p < 0.001) or heart failure (21% vs. 25%, p < 0.001) less frequently than the CCP. Hospital mortality was calculated to be higher in NRMI 2 (19.7% vs. 18.1%, p < 0.001) due mostly to the inclusion of noninsured patients 65 years and older in NRMI 2.

CONCLUSIONS

We conclude that the simpler case ascertainment and data collection strategies employed by NRMI 2 result in process and outcome measures that are comparable to the more rigorous methods utilized by the CCP. Outcomes that are more difficult to measure from retrospective chart review such as stroke and recurrent myocardial infarction must be interpreted cautiously.

[Stent restenosis: therapy concepts and possibilities for prevention]

BACKGROUND

In-stent restenosis has become a significant problem for interventional cardiologists. Due to different pathogenic causes it remains unclear whether a uniform therapeutic regimen is appropriate.

TREATMENT

Redilatation has predominantly been used for the treatment of instent restenosis, however, in long and diffuse restenotic stents, long-term results are reported to be poor. Therefore, tissue-debulking techniques may have beneficial effects in complex cases of in-stent restenosis. The therapeutic benefit of intracoronary radiation, local drug delivery or gene transfer has not been evaluated so far.

PREVENTION

Therefore, prevention of the iatrogenic entity in-stent restenosis has become more important.

A novel emergency telemedicine system based on wireless communication technology--AMBULANCE

Recent studies conclude that early and specialized prehospital management contributes to emergency case survival. We have developed a portable medical device that allows telediagnosis, long distance support, and teleconsultation of mobile healthcare providers by expert physicians. The device allows the transmission of vital biosignals and still images of the patient from the emergency site to the consultation site using the GSM mobile telephony network. The device can telematically "bring" an expert specialist doctor at the site of the medical emergency, allow him/her to evaluate patient data, and issue directions to the emergency personnel on treatment procedures until the patient is brought to be hospital. Legal reasons mandated the inclusion at the consultation site of a multimedia database able to store and manage the data collected by the system. The performance of the system has been validated in four different countries using a controlled medical protocol and a set of 100 patients per country treated has been collected and analyzed.

Presenting characteristics, treatment patterns, and clinical outcomes of non-black minorities in the National Registry of Myocardial Infarction 2

Data from a national registry (cohort) of myocardial infarction, which has enrolled 275,046 patients from June 1994 to April 1996, were analyzed to compare the baseline demographic and clinical characteristics, treatment patterns, and clinical outcomes among Hispanics, Asian-Pacific islanders, and native Americans with those of white Americans presenting to the hospital with acute myocardial infarction. Non-black minorities were younger, had a higher proportion of men, used the emergency medical services less frequently, and presented later to the hospital after the onset of symptoms (135 vs 122 minutes, p <0.001) than whites. Also, non-black minorities were less likely to receive beta-blocker therapy at discharge (crude odds ratio 0.86, confidence interval 0.82 to 0.90) than whites, but they were generally as likely to receive intravenous thrombolytic therapy (with the exception of Asian-Pacific islanders) and undergo both coronary arteriography and revascularization procedures as their white counterparts. There were no significant differences in hospital mortality for non-black minorities compared with whites.

Utility of the prehospital electrocardiogram in diagnosing acute coronary syndromes: the Myocardial Infarction Triage and Intervention (MITI) Project

OBJECTIVES

We sought to determine whether the prehospital electrocardiogram (ECG) improves the diagnosis of an acute coronary syndrome.

BACKGROUND

The ECG is the most widely used screening test for evaluating patients with chest pain.

METHODS

Prehospital and in-hospital ECGs were obtained in 3,027 consecutive patients with symptoms of suspected acute myocardial infarction, 362 of whom were randomized to prehospital versus hospital thrombolysis and 2,665 of whom did not participate in the randomized trial. Prehospital and hospital records were abstracted for clinical characteristics and diagnostic outcome.

RESULTS

ST segment and T and Q wave abnormalities suggestive of myocardial ischemia or infarction were more common on both the prehospital and hospital ECGs of patients with as compared with those without acute coronary syndromes (p < or = 0.00001). Those with prehospital thrombolysis were more likely to show resolution of ST segment elevation by the time of hospital admission (14% vs. 5% in patients treated in the hospital, p = 0.004). In patients not considered for prehospital thrombolysis, both persistent and transient ST segment and T or Q wave abnormalities discriminated those with from those without acute coronary ischemia or infarction. Compared with ST segment elevation on a single ECG, added consideration of dynamic changes in ST segment elevation between serial ECGs improved the sensitivity for an acute coronary syndrome from 34% to 46% and reduced specificity from 96% to 93% (both p < 0.00004). Overall, compared with abnormalities observed on a single ECG, consideration of serial evolution in ST segment, T or Q wave or left bundle branch block (LBBB) abnormalities between the prehospital and initial hospital ECG improved the diagnostic sensitivity for an acute coronary syndrome from 80% to 87%, with a fall in specificity from 60% to 50% (both p < 0.000006).

CONCLUSIONS

ECG abnormalities are an early manifestation of acute coronary syndromes and can be identified by the prehospital ECG. Compared with a single ECG, the additional effect of evolving ST segment, T or Q waves or LBBB between serially obtained prehospital and hospital ECGs enhanced the diagnosis of acute coronary syndromes, but with a fall in specificity.

[Pathophysiology and therapeutic concepts in coronary restenosis]

Demonstration of a reduced restenosis rate after stent implantation (Benestent, STRESS) has initiated rapid increase in stent implantation rates with widening indications. At present, the majority of stents are implanted in "none-Benestent/STRESS-lesions" with the consequence of a higher restenosis rate as previously expected. Stent restenosis has therefore become a relevant problem in interventional cardiology. In contrast to balloon angioplasty, where acute and subacute recoil represents the major mechanism of restenosis, stent restenosis is exclusively attributed to neointima proliferation. Morphological studies have demonstrated that neointima is caused by early smooth muscle cell ingrowth with a maximum after 7 days which is then gradually replaced by extracellular matrix. Systematic clinical, angiographic and intravascular ultrasound studies have identified several risk factors for increased stent restenosis such as: diabetes mellitus, treatment of restenosis, serial stent implantation, small and calcified vessels, ostial lesions, venous bypass grafts and complex stenosis morphology. In addition, there is increasing evidence that aggressive implantation techniques with high pressures and oversized balloons may also induce higher restenosis rates. Optimal treatment of instent restenosis has not been determined so far. Balloon angioplasty is at present considered the therapeutic option of choice. Several small studies have shown, that in short, discrete lesions (< 10 mm) results of simple PTCA are acceptable with re-restenosis rates between 15 and 35%. The intervention is considered safe with low complication rates. In 10 to 15% additional stent implantation is necessary, usually due to dissections proximal or distal to the treated stent. In long, diffuse stent restenosis (> or = 10 mm), however, PTCA results in high re-restenosis rates up to > 80%. This is most likely due to insufficient early balloon angioplasty results with minimal luminal diameters (MLD) significantly below the previous stent diameter. Therefore, debulking techniques have been used to reduce neointima burden within the stent. At present 3 techniques are available: directional coronary atherectomy (DCA), Excimerlaser angioplasty (ELCA) or high frequency rotablation. All of these techniques achieve a significant reduction in plaque volume within the stent and in combination with balloon angioplasty allow larger MLDs than PTCA alone. Limited experiences with ELCA and rotablation have shown that the techniques are safe without major periinterventional complications. DCA, however, has been accompanied with stent destruction and therefore should be considered with large care, especially in stents with coil design. At present, no randomized controlled trials for the comparison of debulking techniques with or without balloon angioplasty versus balloon angioplasty alone are available. Three multicenter trials have been initiated (LARS, ARTIST and TWISTER) to compare debulking techniques versus balloon angioplasty in diffuse stent restenosis. Adjunct medical treatment after interventions for stent restenosis is usually limited to ASS alone, indications for additional application of Ticlopidine have not been verified so far. Positive results are expected for the use of local radiation therapy either by radioactive stent implantation or afterloading techniques. With increasing stent implantation rates and indications, about 400,000 stents will be implanted in 1997 worldwide. Considering a low restenosis rate of 20%, 80,000 stent restenosis will occur within one year. Final recommendations for optimal treatment of these patients are not yet available.

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.