Incidence of cardiac arrest during self-transport for chest pain

STUDY OBJECTIVE

To assess the incidence of cardiac arrest among patients who use self-transport to seek medical care for chest pain.

METHODS

This was a retrospective cohort study of patients admitted to a CCU for suspected acute myocardial infarction (AMI) and patients experiencing out-of-hospital cardiac arrest preceded by symptoms in King County, Washington, between January 1, 1992, and July 31, 1994. Participants were identified through use of the databases compiled by the Myocardial infarction Triage and intervention Trial, which reviewed medical records in all area hospitals, and the Cardiac Arrest Surveillance System, which tracks all incidences in which CPR is performed by EMS personnel in King County. Patients whose sudden cardiac arrests were not preceded by symptoms were excluded. Hospital records were abstracted to find the means of transport for patients admitted to CCUs. For cardiac arrest patients, the medical history, presence of symptoms, means of transport, and prehospital death information were abstracted from paramedic field reports. Outcome (admission, discharge, or in-hospital death) was obtained from hospital records. An event cause (cardiac or other) was determined from death certificates, hospital records, or consultation with private physicians.

RESULTS

During the 30-month study period, 13,187 patients sought help for cardiac symptoms and were either admitted to a CCU or died before admission after calling 911. A majority, 7,393 (59%), were transported by emergency medical services, and 5,182 (41%) used private transportation to obtain medical care; the means of transport could not be determined for 612 patients. Of the EMS group, 6,978 were admitted to the hospital without experiencing prehospital cardiac arrest, and 415 (5.6%) arrested before arriving at the hospital. Of the group using private transportation, 5,164 were admitted without arresting and 18 (.35%) arrested before arrival, after which 911 was called (P < .001).

CONCLUSION

The incidence of cardiac arrest among patients who attempted to reach the hospital by private transportation was very low compared with the incidence among those who chose the EMS system for transport. This suggests that patient self-selection occurs, with the more seriously ill patients more commonly calling 911 for transport.

The revolution and evolution of prehospital cardiac care

Prehospital cardiac care, first established in Belfast, Northern Ireland, in 1966, may be called revolutionary in that it was a radical break from existing practices. The Belfast program "moved" the coronary care unit into the community by treating the early complications of acute myocardial infarcation. The program staffed a mobile coronary care unit with a physician and nurse and demonstrated that patients with out-of-hospital sudden cardiac arrest could be resuscitated. The idea of prehospital cardiac care spread to other countries after publication of the Belfast experience in the Lancet. The first program in the United States, stationed at St Vincent's Hospital in New York, NY, began in 1968 and was modeled after the Belfast program. The physician-staffed model, however, was not widely imitated in the United States. Rather, beginning in 1969, programs using specially trained personnel, know as paramedics, began in Miami, Fla, Seattle, Wash, Columbus, Ohio, Los Angeles, Calif, Portland, Ore, and Nassau County, New York. Paramedic-staffed programs were designed not only to treat early complications of acute myocardial infarction, but also to attempt resuscitation for primary cardiac arrest. Most of the early paramedic programs were based in fire departments. Other programs used private ambulance or police personnel. Prehospital cardiac care has evolved significantly in the past 3 decades. Some notable developments include the tiered response system, training of the general public in cardiopulmonary resuscitation, low-energy defibrillators, automatic external defibrillators, and 12-lead electrocardiographic telemetry. The basic lesson of prehospital cardiac care is that the timely provision of cardiopulmonary resuscitation and defibrillation saves lives.

Reasons patients with chest pain delay or do not call 911

STUDY OBJECTIVE

To determine the reasons patients with suspected acute myocardial infarction (AMI) delay seeking medical care or do not call 911.

DESIGN

Telephone interview of patients hospitalized with suspected AMI.

SETTING

Nine hospitals in King County, Washington.

PARTICIPANTS

Patients admitted to a CCU or ICU between October 1, 1986, and December 31, 1987, with suspected AMI occurring out-of-hospital. Spouses of patients who met criteria but died during the hospitalization also participated.

INTERVENTIONS

Hospital records were reviewed, and a 20-minute telephone interview was conducted of patients who reside in King County but do not live in an extended care facility.

MEASUREMENTS

Patient demographics, cardiac history, symptoms, time of acute symptom onset, time of emergency department arrival, method of transportation, discharge diagnosis, and hospital outcome were abstracted from hospital records. Circumstances leading to the hospitalization, reasons for delay in seeking care, and reasons for not calling 911 were determined in the telephone interview.

RESULTS

In a 15-month period, 5,207 patients were hospitalized for suspected AMI in King County, Washington. Twenty-seven percent had AMI. Median patient delay between symptom onset and hospital arrival was 2 hours. Paramedics transported 45% of all patients. A representative subset of patients (2,316) were interviewed. The main reasons for delay were because the patient thought that the symptoms would go away, because the symptoms were not severe enough, and because the patient thought that the symptoms were caused by another illness. The main reasons for not calling 911 were because the symptoms were not severe enough, because the patient did not think of calling 911, and because the patient thought that self-transport would be faster because of his or her close location to the hospital.

CONCLUSION

Maximal benefit from thrombolytic therapy is not realized in a substantial proportion of patients with AMI because of delays in seeking medical care. Knowledge of the reasons patients delay or do not call 911 can help focus efforts on achieving more rapid treatment of patients with AMI.

Utilization of emergency medical services for symptoms of acute myocardial infarction

OBJECTIVE

To examine patient characteristics and situational and clinical factors that affect utilization of Emergency Medical Services (EMS) for symptoms of acute myocardial infarction (AMI).

DESIGN

Telephone interview of patients hospitalized with suspected AMI.

SETTING

Nine hospitals in King County, Washington.

PATIENTS

Patients admitted to a coronary or intensive care unit between October 1, 1986, and December 31, 1987, with suspected AMI occurring out of hospital. Spouses of patients who met criteria but died during the hospitalization also participated.

OUTCOME MEASURES

Patient demographics, coping strategies, situational factors, prior cardiac history, perceived symptom severity, belief about the nature of condition, and method of transportation.

RESULTS

Descriptive statistics showed that although few patients called EMS as a "first thing" in response to symptoms, almost half of all patients called EMS before being hospitalized. Stepwise logistic regression analyses revealed that being older, the belief that one was experiencing a heart attack, the presence of other people (including the spouse), and the lack of physical activity at time of symptom onset, were related to both greater and quicker utilization of EMS. Additionally, education, medical history of angina, and severity of symptoms also were related to utilization of EMS.

CONCLUSION

The findings are discussed in a theoretical context, using Leventhal's self-regulatory model to suggest avenues for future research and interventions.

Impact of direct mail intervention on knowledge, attitudes, and behavioral intentions regarding use of emergency medical services for symptoms of acute myocardial infarction

This study evaluated a direct mail intervention called the "Call Fast, Call 911" campaign designed to increase use of emergency medical services for symptoms of acute myocardial infarction. The campaign was targeted at individuals over the age of 50. Persons over 50 years of age (N = 130,000) in King County, Washington, were randomly assigned to intervention or control groups. Individuals in the intervention groups received six direct mail pieces over a 1-year period encouraging them to call 911 quickly in response to chest pain. A postintervention telephone survey of a random sample of households (N = 434) assessed the impact of the campaign on knowledge, attitudes, and behavioral intentions regarding use of emergency medical services for symptoms of acute myocardial infarction. The results showed no significant differences between intervention and control groups in terms of knowledge of AMI. However, there were significant differences in beliefs and behavioral intentions to call 911 in a cardiac emergency.

Increasing the efficiency of emergency medical services by using criteria based dispatch

STUDY OBJECTIVES

To determine whether criteria based dispatch (CBD) improved the efficiency of the emergency medical services system.

DESIGN

A before and after design was used to measure effects of CBD. Data were reviewed from medical reports from January 1986 through June 1992.

SETTING

King County, Washington, excluding the city of Seattle.

PARTICIPANTS

Residents who called 911 to report a medical emergency.

INTERVENTIONS

Emergency medical dispatching (EMD), basic life support (BLS), and advanced life support (ALS).

RESULTS

Findings show a decrease in ALS responses for two tracer conditions that medical control physicians determined not require ALS intervention. The percentage of febrile seizures in which paramedics responded decreased from 41% to 21% (P < .001). The percentage of cerebrovascular accidents in which paramedics responded decreased from 41% to 28% (P < .001). CBD led to a decrease, from 4.7% to 3.8% (P < .001), in frequency of requests by BLS units for dispatch of ALS units. There was no increase in the time required to dispatch each call.

CONCLUSION

CBD increased the efficiency of the EMS system by significantly reducing ALS responses to incidents not requiring ALS intervention and reducing requests by BLS units for dispatch of ALS units while maintaining a consistent time from receipt of call to dispatch.

911 and emergency department use for chest pain: results of a media campaign

STUDY OBJECTIVE

We evaluated the effects of a community public education campaign that encouraged patients to quickly call 911 after the onset of acute myocardial infarction (AMI) symptoms.

SETTING AND PARTICIPANTS

The media campaign focused on residents 50 years of age or older in King County, Washington, which has a population of 1.5 million (1990 census).

DESIGN

We determined 911 responses for chest pain, emergency department visits for AMI symptoms, the number of patients admitted to a CCU with an admitting diagnosis of rule-out MI, and the number of confirmed AMIs before and after the campaign.

RESULTS

The number of emergency medical services (EMS) responses (911 runs) for patients 50 years of age or older experiencing AMI symptoms increased significantly during the media campaign. ED visits for chest pain also increased significantly during the campaign, as did the number of patients 50 years of age or older admitted to a King County CCU with an admitting diagnosis of rule-out MI. Each of the above increases tapered--with time after the media campaign but remained above baseline.

CONCLUSION

An intense public education campaign can significantly increase EMS use, ED visits, and CCU admissions for AMI symptoms. However, these effects taper off with time after the campaign.

Predicting survival from out-of-hospital cardiac arrest: a graphic model

STUDY OBJECTIVE

To develop a graphic model that describes survival from sudden out-of-hospital cardiac arrest as a function of time intervals to critical prehospital interventions.

PARTICIPANTS

From a cardiac arrest surveillance system in place since 1976 in King County, Washington, we selected 1,667 cardiac arrest patients with a high likelihood of survival: they had underlying heart disease, were in ventricular fibrillation, and had arrested before arrival of emergency medical services (EMS) personnel.

METHODS

For each patient, we obtained the time intervals from collapse to CPR, to first defibrillatory shock, and to initiation of advanced cardiac life support (ACLS).

RESULTS

A multiple linear regression model fitting the data gave the following equation: survival rate = 67%-2.3% per minute to CPR-1.1% per minute to defibrillation-2.1% per minute to ACLS, which was significant at P < .001. The first term, 67%, represents the survival rate if all three interventions were to occur immediately on collapse. Without treatment (CPR, defibrillatory shock, or definitive care), the decline in survival rate is the sum of the three coefficients, or 5.5% per minute. Survival rates predicted by the model for given EMS response times approximated published observed rates for EMS systems in which paramedics respond with or without emergency medical technicians.

CONCLUSION

The model is useful in planning community EMS programs, comparing EMS systems, and showing how different arrival times within a system affect survival rate.

Hospital mortality in acute myocardial infarction in the era of reperfusion therapy (the Myocardial Infarction Triage and Intervention Project)

This study was conducted in 19 hospitals in the metropolitan Seattle area and included 6,270 unselected patients who had acute myocardial infarction (AMI) between January 1988 and April 1991. Hospital mortality was determined and related to patient demographic and clinical characteristics, the use of reperfusion therapies, and to complications after AMI. Thrombolytic therapy or direct coronary angioplasty < 6 hours from symptom onset was used to treat 1,185 (19%) and 524 (9%) patients, respectively. There were 629 (10%) hospital deaths; most occurred during the first 3 days of hospitalization. Factors affecting mortality after admission included: recurrent chest pain, recurrent AMI, development of heart failure, and the occurrence of stroke. After adjustment for age, treatment with thrombolytic therapy or direct angioplasty had no independent effect on reducing the overall mortality rate. Hospital mortality rates for AMI have improved considerably since 1970, although recurrent myocardial ischemic events continue to have an adverse effect on outcome. The current use of reperfusion treatments has had minimal causal impact on overall mortality rates, principally because less than one third of patients, who are relatively "low risk," are eligible and receive these treatments.

Prehospital delay interval for patients who use emergency medical services: the effect of heart-related medical conditions and demographic variables

STUDY OBJECTIVE

To investigate the effect of heart-related medical conditions and demographic variables on patients' tendency to delay contacting emergency medical services for symptoms of acute myocardial infarction.

TYPE OF PARTICIPANTS

A sample of 2,947 patients with acute myocardial infarction but no cardiac arrest, transported by paramedics to the coronary care units of 19 hospitals in King County, Washington, between January 1988 and April 1991.

MEASUREMENTS

Patient record abstracts contained information on medical history, age, gender, delay interval, and means of transportation.

RESULTS

Multiple regression analyses showed that prehospital delay interval was significantly greater for individuals who were older and female and who had a history of angina, congestive heart failure, or diabetes.

CONCLUSION

It is important to investigate further how people interpret and evaluate their symptoms in light of other medical conditions. It is also critical to find out why women delay longer than men and why older individuals delay longer than younger people before they contact emergency medical services. Interventions need to be developed that are targeted at populations at risk for delaying use of emergency medical services for acute myocardial infarction symptoms. These interventions must legitimize the use of emergency medical services and encourage patients to act quickly when confronted with acute myocardial infarction symptoms.

The association between on-site cardiac catheterization facilities and the use of coronary angiography after acute myocardial infarction. Myocardial Infarction Triage and Intervention Project Investigators

BACKGROUND

During the past decade the use of coronary angiography after acute myocardial infarction has substantially increased. Among the possible contributing factors, the increasing availability of cardiac catheterization facilities was the focus of our investigation.

METHODS

We investigated whether the availability of cardiac catheterization facilities at an admitting hospital was associated with the likelihood that a patient would undergo coronary angiography. After adjusting for age, sex, cardiac history, and cardiac complications during hospitalization, we evaluated this association in 5867 consecutive patients with acute myocardial infarction admitted to 19 Seattle-area hospitals. We also assessed the association between the presence of on-site cardiac catheterization facilities and in-hospital mortality.

RESULTS

Patients admitted to hospitals with on-site cardiac catheterization facilities were far more likely to undergo coronary angiography (odds ratio, 3.21; 95 percent confidence interval, 2.81 to 3.67) than patients admitted to hospitals where transfer to another institution would be required to perform cardiac catheterization. Admission to a hospital with on-site facilities was more strongly associated with the use of coronary angiography than any characteristic of the patient. Although our study had limited power to detect differences in mortality, the availability of coronary angiography had no discernible association with in-hospital mortality rates (odds ratio for mortality among patients admitted to hospitals with on-site facilities vs. patients admitted to hospitals without such facilities, 0.88; 95 percent confidence interval, 0.71 to 1.09).

CONCLUSIONS

In this community-wide study, the availability of on-site cardiac catheterization facilities was associated with a higher likelihood that a patient would undergo coronary angiography. However, admission to hospitals with these facilities did not appear to be associated with lower short-term mortality.

Thrombolytic therapy

All patients with symptoms and ECG findings suggestive of acute myocardial infarction (AMI) should be considered for treatment with thrombolytic agents. The decision to use thrombolytic therapy is a clinical judgment based upon a weighing of the potential benefits versus the possible risks. The physician must take into account relative contraindications, age of the patient, area of jeopardized myocardium, and duration of symptoms. Health professionals involved in the care of AMI patients should develop written plans and protocols addressing the following matters: identification of patients with chest pain in the prehospital setting (this applies to hospitals that receive patients from emergency medical services systems), triage of patients in the emergency department, obtaining the 12-lead electrocardiogram, determination of contraindications, authority for ordering thrombolytic therapy, and consultation for atypical cases. There also should be agreed standards for the time interval from arrival in the ED to administration of the thrombolytic agent, as well as a commitment to the prospective monitoring of procedures and times to assure continuous improvement. A time interval for treatment (arrival in ED to administration of drug) of 30 to 60 minutes should be achievable for patients who present with typical symptoms and ECG findings.

Incidence of agonal respirations in sudden cardiac arrest

STUDY OBJECTIVE

To discover the frequency of agonal respirations in cardiac arrest calls, the ways callers describe them, and discharge rates associated with agonal respirations.

DESIGN

We reviewed taped recordings of calls reporting cardiac arrests and emergency medical technician and paramedic incident reports for 1991. Arrests after arrival of emergency medical services were excluded.

SETTING

King County, Washington, excluding the city of Seattle.

PARTICIPANTS

Four hundred forty-five persons with out-of-hospital cardiac arrests receiving emergency medical services.

INTERVENTIONS

Telephone CPR, emergency medical technicians-defibrillation, and advanced life support by paramedics.

MEASUREMENTS AND MAIN RESULTS

Any attempts at breathing described by callers were identified, as well as whether agonal respirations could be heard by dispatcher, emergency medical technicians, or paramedics. Agonal respirations occurred in 40% of 445 out-of-hospital cardiac arrests. Callers described agonal breathing in a variety of ways. Agonal respirations were present in 46% of arrests caused by cardiac etiology compared with 32% in other etiologies (P < .01). Fifty-five percent of witnessed arrests had agonal activity compared with 16% of unwitnessed arrests (P < .001). Agonal respirations occurred in 56% of arrests with a rhythm of ventricular fibrillation compared with 34% of cases with a nonventricular fibrillation rhythm (P < .001). Twenty-seven percent of patients with agonal respirations were discharged alive compared with 9% without them (P < .001).

CONCLUSION

There is a high incidence of agonal activity associated with out-of-hospital cardiac arrest. Presence of agonal respirations is associated with increased survival. These findings have implications for public CPR training programs and emergency dispatcher telephone CPR programs.

The epidemiology of cardiac arrest in young adults

STUDY OBJECTIVE

To describe the epidemiology of cardiac arrest in young adults and to determine if there are characteristics unique to this group in terms of etiology, rhythm, and outcome.

DESIGN

Retrospective, case review.

SETTING

King County, Washington.

TYPE OF PARTICIPANTS

All out-of-hospital victims of cardiac arrest who received emergency aid.

MEASUREMENTS

The etiology, cardiac rhythm, and outcome were identified for each case.

MAIN RESULTS

During the 13-year period from 1976 to 1989, there were 8,054 cardiac arrests; 252 of these were among young adults 18 to 35 years of age. Of those 252 cases, 61 (24%) were caused by ischemic heart disease, and 60 (24%) were caused by overdose. Asystole was the most common rhythm (48%), followed by ventricular fibrillation or tachycardia (31%). Long-term survival following these rhythms was 4% and 28%, respectively. In terms of age, etiology, and rhythm, young adults appear to represent a transitional group between children and older adults. There were no unique characteristics specific to young adults. Long-term survival is dependent more on rhythm than on age.

CONCLUSION

In terms of age, etiology, and rhythm, young adults appear to represent a transitional group between children and older adults.

Multiple-dose sodium polystyrene sulfonate in lithium intoxication: an animal model

Previous work in our laboratory has demonstrated that sodium polystyrene sulfonate (SPS) significantly lowered serum lithium (Li) concentrations when administered in a single oral dose after an oral dose of lithium in a mouse model. The present study was designed to determine whether: 1) repetitive doses of SPS are effective in lowering serum lithium concentrations, 2) the effect of SPS on lithium concentration is dose related and 3) SPS enhances the elimination of lithium. Mice (N = 144) were given orogastric LiCl (250 mg/kg) and then divided into 4 groups: Controls received water 0, 30, 90, 180, and 360 min. after LiCl; the Full-Dose SPS Group received SPS (5 g/kg/dose) at equivalent times; the Half-Dose SPS Group received SPS (2.5 g/kg/dose) at the same times; and the Elimination Group received water at 0 and 30 min. after LiCl and SPS at 90, 180 and 360 min. after LiCl. Subgroups of each group were sacrificed at 1, 2, 4 and 8 hr post-treatment and serum analyzed for lithium concentrations. Statistical analyses revealed that, when compared to Controls: 1) SPS significantly lowered serum lithium concentrations; 2) this effect was dose-related; 3) repetitive dosing of SPS appears to enhance the elimination of lithium.

Numerators, denominators, and survival rates: reporting survival from out-of-hospital cardiac arrest

This study demonstrates the effect of different denominators on the survival rate from out-of-hospital cardiac arrest. We retrospectively analyzed data from a cardiac arrest surveillance system in King County, Washington during the years 1976 to 1988, and calculated survival rates using eight different definitions of denominators. The eight survival rates ranged from 16% to 49% discharge from hospital. The denominator for the lowest survival rate included all cases of cardiac arrest for whom emergency medical services personnel started cardiopulmonary resuscitation. The denominator for the highest survival rate included: all cases of presumed cardiac etiology; first recorded rhythm was ventricular fibrillation; collapse witnessed; cardiopulmonary resuscitation started by bystanders within 4 minutes; and definitive care provided within 8 minutes. The definition of cases included in the denominator can dramatically effect the resultant survival rate. There must be national and international agreement about definitions of denominators for valid cross community comparisons.

Effect of age on use of thrombolytic therapy and mortality in acute myocardial infarction. The MITI Project Group

The findings in 3,256 consecutive patients hospitalized for acute myocardial infarction were tabulated to assess the history, treatments and outcome in the elderly; 1,848 patients (56%) were greater than 65 years of age, including 28% who were aged greater than or equal to 75 years. The incidence of prior angina, hypertension and heart failure (only 3% of patients less than 55 years of age had a history of heart failure compared with 24% greater than or equal to 75 years old) was found to increase with age. Twenty-nine percent of patients less than 75 years of age were treated with a systemic thrombolytic drug compared with only 5% of patients older than 75 years. Mortality rates increased strikingly with advanced age (less than 2% in patients less than or equal to 55, 4.6% in those 55 to 64, 12.3% in those 65 to 74 and 17.8% in those greater than or equal to 75 years). Both the incidence of complicating illness and a nondiagnostic electrocardiogram (ECG) increased with age. In a multivariate analysis of outcome in older patients (greater than or equal to 65 years), adverse events were related to both prior history of heart failure (odds ratio 3.9) and increasing age (odds ratio 1.4 per each decade of age). Outcome was not improved by treatment with thrombolytic drugs, but these agents were prescribed to only 12% of patients greater than 65 years of age, thereby reducing the power for detecting such an effect.(ABSTRACT TRUNCATED AT 250 WORDS)