Basic emergency medical care of patients with acute myocardial infarction: initial prehospital characteristics and in-hospital complications

Prehospital Use of Aspirin Rarely Is Associated with Adverse Events

Introduction:

Aspirin is commonly administered for acute coronary syndromes in the prehospital setting. Few studies have addressed the incidence of adverse effects associated with prehospital administration of aspirin. Objective: To determine the incidence of adverse events following the administration of aspirin by prehospital personnel.

Methods:

Multi-center, retrospective, case series that involved all patients who received aspirin in the prehospital setting from (01 August 1999–31 January 2000). Patient encounter forms of the emergency medical services (EMS) of a metropolitan fire department were reviewed. All patients who had a potential cardiac syndrome (i.e., chest pain, dyspnea) as documented on the EMS forms were included in the review. Exclusion criteria included failure to meet inclusion criteria, and chest pain secondary to apparent noncardiac causes (i.e., trauma). Hospital charts were reviewed from a subset of patients at the participating hospitals. The major outcome was an adverse event following prehospital administration of aspirin. This outcome was evaluated during the EMS encounter, at emergency department discharge, or at six and 24-hours post-aspirin ingestion. An adverse event secondary to aspirin ingestion was defined as anaphylaxis or allergic reactions, such as rash or respiratory changes.

Results:

A total of 25,600 EMS encounter forms were reviewed, yielding 2,399 patients with a potential cardiac syndrome. Prior to EMS arrival, 585 patients had received aspirin, and 893 were administered aspirin by EMS personnel. No patients had an adverse event during the EMS encounter. Of these patients, 229 were transported to participating hospitals and 219 medical records were available for review with no adverse reactions recorded during their hospital course.

Conclusion:

Aspirin is rarely associated with adverse events when administered by prehospital personnel for presumed coronary syndromes.

Early management of acute myocardial infarction: thrombolysis, angioplasty, and adjunctive therapies

Early identification and treatment, including administration of intravenous thrombolytics, coronary angioplasty, and adjunctive therapies, has been shown to benefit patients who present with acute myocardial infarction. However, only a small percentage of these patients receive such therapies because of late presentation, associated risks, and controversies around certain myocardial infarct subsets. The logistics involved in carrying out these treatments have resulted in unnecessary prehospital and in-hospital delays. These issues make essential the availability of a streamlined protocol that should be updated at regular intervals to ensure that these time-dependent therapies are more routinely and rapidly utilized. This article discusses these topics in conceptual format and provides a ready-to-use protocol.

Diuretics in postinfarction heart failure

Severe left ventricular failure, as evidenced by radiographic pulmonary edema or raised left ventricular filling pressure, accompanying acute myocardial infarction, carries a high mortality risk. In this situation, the intravenous loop-diuretic furosemide induces a rapid reduction in the raised left ventricular filling pressure due to an immediate and substantial increase in systemic venous compliance accompanied by increasing diuresis. This diuretic-induced venodilatation is probably due to the release of prostaglandins. The transient systemic arterial constriction and small increase in systemic blood pressure that follows intravenous furosemide probably results from the release of renin and subsequent activation of angiotensin. These diuretic induced hemodynamic changes are accompanied by restoration of the vasodilator reflex, which enables the heart to accommodate an acute volume load. Orally administered loop diuretics achieve slower, but similar, directional hemodynamic changes. There is no information on hemodynamic or neuroendocrine dose-response effects of loop diuretics, and there is no information pertaining to the use of other diuretic groups in this situation. The hemodynamic changes induced by furosemide summate with the changes induced by other anti-heart-failure drugs. In this subset of patients with acute myocardial infarction and severe heart failure, the influence of the diuretics on morbidity incidence and mortality risk remains to be measured.

Patient delay and receipt of thrombolytic therapy among patients with acute myocardial infarction from a community-wide perspective

The duration of patient delay from the time of onset of symptoms of acute myocardial infarction (AMI) to hospital presentation, and the relation of delay time and various patient characteristics to receipt of thrombolytic therapy were examined as part of a community-based study of patients hospitalized with AMI in the Worcester, Massachusetts, metropolitan area. In all, 800 patients with validated AMI hospitalized at 16 hospitals in the Worcester metropolitan area in 1986 and 1988 constituted the study sample. Patients delayed on average 4 hours between noting symptoms suggestive of AMI and presenting to area-wide emergency departments with no significant change observed between 1986 and 1988. The shorter the time interval of delay, the greater the likelihood of receiving thrombolytic therapy; patients arriving at the emergency department within 1 hour of the onset of acute symptoms were approximately 2.5 and 6.5 times more likely to receive thrombolytic agents than were those presenting to the hospital between 4 and 6, and greater than 6 hours, respectively, after the onset of symptoms. Results of a multivariate analysis showed increasing length of delay, older age, history of hypertension or AMI and non-Q-wave AMI to be significantly associated with failure to receive thrombolytic therapy.

Acute myocardial infarction. An updated protocol for thrombolytic therapy

Only a small percentage of patients who have acute myocardial infarction receive the benefit of intravenous thrombolytic therapy, often because logistics result in unnecessary pre-hospital and in-hospital delays. Dr Selig therefore recommends that a streamlined protocol be available and that it be updated at regular intervals to ensure that this time-dependent therapy is more routinely utilized.

Clinical significance of initial systolic hypertension after myocardial infarction

To clarify the clinical significance of acutely raised systolic blood pressure (SBP) after myocardial infarction, 60 patients who were admitted within six hours after onset were studied. Initial systolic hypertension was shown in 26.6% of patients. Time-corresponding plasma epinephrine and norepinephrine levels were abnormally high in 61% and 86% of patients respectively. These high values of catecholamines were not, however, specific to systolic hypertension. On the contrary, an inverse correlation was observed between systolic blood pressure and plasma epinephrine value. It appeared that the anxiety and stress of chest pain do not contribute to raising blood pressure through catecholamine liberation. In the high pressure group (SBP greater than or equal to 160 mmHg), only 3 of 16 patients were classified into severer grades (III or IV) of Killip's classification. This proved to be statistically significant. A similar result was obtained in Lown's grading. Only 1 of 16 patients showed severe ventricular tachyarrhythmia. It appeared obvious from these data that patients who showed initial systolic hypertension are well protected from severe congestive heart failure and from life-threatening ventricular tachyarrhythmia in acute myocardial infarction.

Anatomic substrate differences between black and white victims of sudden cardiac death: hypertension, coronary artery disease, or both?

Despite recent declines in mortality from coronary heart disease (CHD), it remains the major cause of death in the United States for blacks and whites. Although the prevalence of the ischemic syndromes in blacks and whites is similar, cardiac mortality and sudden cardiac death rate are higher in blacks. Recent attempts to explain the excess mortality in blacks have focused on barriers to health care and on sociocultural differences in perceptions of and responses to symptoms of CHD. However, the anatomic substrates of ischemia and sudden cardiac death are also different in blacks and whites. Obstructive coronary artery disease tends to be more severe in whites, while blacks have a greater prevalence of hypertensive heart disease. A body of evidence has recently emerged showing that the presence of left ventricular hypertrophy (LVH) is an important, potent predictor for subsequent cardiac death and that the mortality risk of LVH may be particularly high when underlying coronary disease is present. The greater prevalence and severity of hypertension and LVH in blacks may explain the higher cardiac mortality in blacks, even in the presence of less severe coronary disease. The reason why mortality risk is increased in the presence of LVH has not been established. Evidence suggests that it may be due to the increased predisposition to malignant arrhythmias and the increased frequency of potentially lethal silent ischemic events that occur in hypertensive individuals, particularly those with LVH.

Early versus late hospital arrival for acute myocardial infarction in the western Washington thrombolytic therapy trials

In the 3 Western Washington thrombolytic therapy trials, 54.9% of patients with acute myocardial infarction arrived at the hospital within 2 hours of symptom onset. These early arrivers were younger and more likely to be hypotensive and in cardiogenic shock than were patients arriving later. There were decreases in the time from symptom onset to hospital arrival (p = 0.0002) and in the time from hospital arrival to institution of thrombolytic therapy (p less than 0.0001) in the 8 hospitals that participated in both the Western Washington intravenous streptokinase and tissue plasminogen activator trials from 1983 to 1988. For those patients receiving thrombolysis, early arrival was associated with increased survival (p = 0.031) after adjustment by Cox regression analysis for important clinical predictors of long-term survival. These covariates included pulmonary edema, anterior wall acute myocardial infarction, hypotension and absence of chest pain at hospital arrival. Reductions in barriers to timely administration of thrombolytic therapy can be achieved and can result in improved survival.

A comparison of paramedic versus basic emergency medical care of patients at high and low risk during acute myocardial infarction

This prospective study compares the outcome of patients with acute myocardial infarction managed by mobile intensive care (paramedic phase) with that of similar patients managed by basic emergency medical care (control phase) in the same community before the introduction of paramedics. All paramedic-transported patients were managed according to a standard chest pain protocol with use of prophylactic lidocaine and, as needed, treatment for sinus bradycardia, hypotension and life-threatening ventricular arrhythmia. There were no specific interventions for supraventricular tachyarrhythmia or hypertension. All patients were treated under similar in-hospital protocols. Percent mortality in patients with hypotension, the highest risk subgroup in the control phase, was significantly lowered with paramedic-level care (69 versus 10%, p = 0.01). Patients with hypertension, a relatively low risk subgroup during the control phase (16% mortality), were also at lower risk during the paramedic phase (10% mortality). In fact, there was no mortality in either study phase for patients with an initial systolic blood pressure greater than 180 mm Hg. During the combined study phases, patients with normotension and tachycardia demonstrated a tendency toward higher percent mortality (33%) than either patients with normotension without tachycardia (10%) or those with hypertension and tachycardia (6%). Although the overall percent mortality was reduced by 24% (from 21 to 16%), this decrease was largely due to the improvement of patients with hypotension. Investigation into the feasibility of prehospital interventions for the high risk patient with acute myocardial infarction normotension and tachycardia appears warranted.

Survival rates and prehospital delay during myocardial infarction among black persons

Over a 12-month period, a consecutive series of 111 black patients admitted to a municipal hospital in Chicago was studied. The 2-week mortality rate for the entire group was 19% (95% confidence intervals, 11.7 to 26.3), and the rate was twice as high for women as for men. A history of systemic hypertension was encountered in 75% of the patients, and diabetes mellitus was present in 33%, although they were not significant predictors of mortality within this group. The delay time from onset of symptoms to arrival at the hospital was markedly prolonged compared with studies of predominantly white populations--twice as long at the median and 3 times as long at the mean. Preventive campaigns aimed at this population should include educating patients on the symptoms of coronary artery disease and encouraging them to seek prompt medical care. Attention must also be given to eliminating obstacles to access to care in this group.