Accuracy of computer-interpreted electrocardiography in selecting patients for thrombolytic therapy. MITI Project Investigators.

A prehospital computer-interpreted electrocardiogram (ECG) was obtained in 1,189 patients with chest pain of suspected cardiac origin during an ongoing trial of prehospital thrombolytic therapy in acute myocardial infarction. Electrocardiograms were performed by paramedics 1.5 +/- 1.2 h after the onset of symptoms. Of 391 patients with evidence of acute myocardial infarction, 202 (52%) were identified as having ST segment elevation (acute injury) by the computer-interpreted ECG compared with 259 (66%) by an electrocardiographer (p less than 0.001). Of 798 patients with chest pain but no infarction, 785 (98%) were appropriately excluded by computer compared with 757 (95%) by an electrocardiographer (p less than 0.001). The positive predictive value of the computer- and physician-interpreted ECG was, respectively, 94% and 86% and the negative predictive value was 81% and 85%. Prehospital screening of possible candidates for thrombolytic therapy with the aid of a computerized ECG is feasible, highly specific and with further enhancement can speed the care of all patients with acute myocardial infarction.

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)

Myocardial Infarction Triage and Intervention Project--phase I: patient characteristics and feasibility of prehospital initiation of thrombolytic therapy.

Prehospital initiation of thrombolytic therapy by paramedics, if both feasible and safe, could considerably reduce the time to treatment and possibly decrease the extent of myocardial necrosis in patients with acute coronary thrombosis. Preliminary to a trial of such a treatment strategy, paramedics evaluated the characteristics of 2,472 patients with chest pain of presumed cardiac origin; 677 (27%) had suitable clinical findings consistent with possible acute myocardial infarction and no apparent risk of complication for potential thrombolytic drug treatment. Electrocardiograms (ECGs) of 522 of the 677 patients were transmitted by cellular telephone to a base station physician; 107 (21%) of the tracings showed evidence of ST segment elevation. Of the total 2,472 patients, 453 developed evidence of acute myocardial infarction in the hospital; 163 (36%) of the 453 had met the strict prehospital screening history and examination criteria and 105 (23.9%) showed ST elevation on the ECG and, thus, would have been suitable candidates for prehospital thrombolytic treatment if it had been available. The average time from the onset of chest pain to prehospital diagnosis was 72 +/- 52 min (median 52); this was 73 +/- 44 min (median 62) earlier than the time when thrombolytic treatment was later started in the hospital. Paramedic selection of appropriate patients for potential prehospital initiation of thrombolytic treatment is feasible with use of a directed checklist and cellular-transmitted ECG and saves time. This strategy may reduce the extent and complications of infarction compared with results that can be achieved in a hospital setting.

Gender differences in the treatment and outcome of acute myocardial infarction. Results from the Myocardial Infarction Triage and Intervention Registry.

BACKGROUND: The objective of this study was to compare treatment and outcome of acute myocardial infarction in women and men. METHODS: In this survey, patient hospital records were reviewed, and information about patient characteristics, treatments, and hospital events was entered in the Myocardial Infarction Triage and Intervention Registry. Between January 1988 and June 1990, a total of 4891 consecutive patients, including 1659 women, were hospitalized for acute myocardial infarction in 19 hospitals in the Seattle (Wash) metropolitan area. In-hospital thrombolytic therapy, coronary angiography, angioplasty, and bypass surgery were examined, as were in-hospital complications and death. RESULTS: Women were older and more often had histories previous hypertension and previous congestive heart failure. Thrombolytic therapy was used less often in women, although information about eligibility for treatment was not available to determine if this difference was due to treatment bias or differences in eligibility. Both coronary angiography and coronary angioplasty were used less frequently in women. However, of patients who had coronary angiography, equal proportions of women and men received angioplasty and/or coronary bypass surgery. Hospital mortality was 16% for women and 11% for men, although this difference was diminished by age adjustment. Mortality was higher in women undergoing bypass surgery, but this difference, too, was less apparent after age adjustment. CONCLUSIONS: Despite high levels of risk factors and mortality, coronary angiography and angioplasty were used less often in women, although among those who underwent coronary angiography, there were no gender differences in the use of angioplasty or bypass surgery. Clearly, more needs to be known about decision making for coronary angiography, as this process seems to differ for women and men with acute myocardial infarction.

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.

Influence of early prehospital thrombolysis on mortality and event-free survival (the Myocardial Infarction Triage and Intervention [MITI] Randomized Trial). MITI Project Investigators.

The Myocardial Infarction Triage and Intervention Trial of prehospital versus hospital administration of thrombolytic therapy markedly reduced hospital treatment times, but the 2 groups had similar outcomes. However, patients treated < 70 minutes from symptom onset had better short-term outcomes. The purpose of this study was to determine the long-term influence of very early thrombolytic treatment for acute myocardial infarction. A total of 360 patients were followed for vital status and cardiac-related hospital admissions over a period of 34 +/- 16 months. Patients enrolled in the trial had symptoms for < or = 6 hours, ST-segment elevation on the prehospital electrocardiogram, and no risk factors for serious bleeding. They received aspirin and recombinant tissue plasminogen activator either before or after hospital arrival. Primary end points in this study included long-term survival and survival free of death or readmission to the hospital for angina, myocardial infarction, congestive heart failure, or revascularization. Two-year survival was 89% for prehospital- and 91% for hospital-treated patients (p = 0.46). Event-free survival at 2 years was 56% and 64% for prehospital- and hospital-treated patients, respectively (p = 0.42). In patients treated < 70 minutes from symptom onset, 2-year survival was 98%, and it was 88% for those treated later (p = 0.12). Two-year event-free survival was 65% for patients treated early and 59% for patients treated later (p = 0.80). In this trial, poorer long-term survival was associated with advanced age, history of congestive heart failure, and coronary artery bypass surgery performed before the index hospitalization, but not with time to treatment.

Use of the automatic external defibrillator in homes of survivors of out-of-hospital ventricular fibrillation.

This 57-month study evaluated the use of automatic external defibrillators (AEDs) in the homes of high risk cardiac patients (survivors of out-of-hospital ventricular fibrillation [VF]). The goal was to determine the utility of these devices by trained lay persons in actual cardiac arrest episodes. Ninety-seven survivors of out-of-hospital VF were enrolled in the study; 59 patients received AEDs, and 38 patients served as a control group. During the study period, 7 deaths occurred in the hospital without preceding out-of-hospital cardiac arrest or from noncardiac causes. There were 14 out-of-hospital cardiac arrests, 10 in the AED group and 4 in the control group. There was 1 long-term survivor in the control group. In the AED group, among the 10 cardiac arrests for which the device was available, it was used in 6. Only 2 patients were in VF; 1 was resuscitated with residual neurologic deficits and survived several months. This study observed a small potential for AEDs to save high risk patients.

Characteristics of black patients admitted to coronary care units in metropolitan Seattle: results from the Myocardial Infarction Triage and Intervention Registry (MITI).

Since 1988, 641 black and 11,892 white patients with chest pain of presumed cardiac origin have been admitted to coronary care units in 19 hospitals in metropolitan Seattle. Black men and women were younger (58 vs 66, p less than 0.0001), more often admitted to central city hospitals (p less than 0.0001), and developed evidence of acute myocardial infarction (AMI) less often (19 vs 23%, p = 0.01). In the subset of 2,870 AMI patients, blacks (n = 121) were younger (59 vs 67, p less than 0.0001) and had less prior coronary artery bypass graft surgery (2 vs 10%, p = 0.005) and more prior hypertension (67 vs 46%, p less than 0.0001). During hospitalization, whites (n = 2,749) had higher rates of coronary angioplasty (18 vs 10%, p = 0.03) and coronary artery bypass graft surgery (10 vs 4%, p = 0.04), although thrombolytic therapy and cardiac catheterization were used equally in the 2 groups. Hospital mortality was 7.4% for black and 13.1% for white patients (p = 0.07). However, after adjustment for key demographic and clinical variables by logistic regression, this difference was not as apparent (p = 0.38). Questions about the premature onset of coronary artery disease, excess systemic hypertension, and the differential use of interventions in black persons have been raised by other investigators. Despite differences in age, referral patterns and the use of coronary angioplasty and bypass surgery, black and white patients with AMI in metropolitan Seattle had similar outcomes.

Outcomes in African-American women with suspected acute myocardial infarction: the Myocardial Infarction Triage and Intervention Project.

Increasing attention has been given to the investigation of cardiovascular disease in women, although African-American women have received little attention. This study compares characteristics and outcomes in women admitted to coronary care units for suspected acute myocardial infarction (MI). Between January 1988 and December 1991, a total of 554 (5%) African-American and 9738 (95%) white women with suspected acute MI were admitted to coronary care units in metropolitan Seattle, Washington. Relevant demographic socioeconomic, clinical, and outcome data were abstracted from the medical record and entered in the Myocardial Infarction Triage and Intervention registry. African-American women were younger, more often single and unemployed, and were less likely to have health insurance than their white counterparts. In addition, a higher proportion of African-American women reported a history of hypertension and diabetes mellitus. After adjustment for age, African-American women were equally as likely to develop acute MI and were more likely to die in the hospital. In addition, a higher proportion of African-American women were readmitted to coronary care units for suspected MI. Compared with their white counterparts, African-American women with suspected acute MI were considerably worse off from both socioeconomic and clinical standpoints, and their relative disadvantage was apparent in poor outcomes.

Early recognition and treatment of the patient suffering from acute myocardial infarction. A description of the Myocardial Infarction Triage and Intervention Project.

Involving emergency medical personnel in the evaluation and treatment of the AMI patients is feasible. A standard, organized approach saves time. Obtaining an ECG in the prehospital setting is also feasible and decreases the delay to diagnosis and subsequent treatment for patients after hospital arrival. Early findings from the MITI registry suggests that only 20% to 30% of patients with AMI are currently eligible to receive thrombolytic medications. This seems to indicate that either current treatment guidelines need to be broadened or that thrombolytic therapy is not appropriate for all AMI patients and, therefore, alternative acute treatment approaches need to be investigated further.

Use of direct angioplasty for treatment of patients with acute myocardial infarction in hospitals with and without on-site cardiac surgery. The Myocardial Infarction, Triage, and Intervention Project Investigators.

BACKGROUND: In the Myocardial Infarction, Triage, and Intervention (MITI) registry of acute myocardial infarction, 441 (12%) of 3750 patients had direct angioplasty as initial treatment. Approximately half (233) were performed in hospitals with no on-site surgery. METHODS AND RESULTS: Procedure success rates, use of emergent surgery, and factors influencing outcome were compared in both angioplasty groups as well as with 653 patients treated with thrombolytic therapy in the same hospitals. There was no difference in baseline characteristics between patient groups treated by angioplasty in the two types of hospitals. Patency was established in 88% of patients. Only 1.4% underwent emergent surgery. Overall, survival was 93% but was significantly worse after a failed procedure in all ECG and hemodynamic subsets as well as in those with prior bypass surgery. In a multivariate analysis, age, initial heart rate, blood pressure, and prior bypass surgery but not type of hospital were predictive of survival. Survival rates were similar, but there tended to be fewer strokes (0.6% versus 2.1%, P = .12), shorter hospital stays (7.0 versus 8.1 days, P < .001), and less recurrent ischemia (20% versus 30%, P = .009) in patients treated by angioplasty compared with thrombolysis. Readmission and reinfarction rates were similar for both treatments. CONCLUSIONS: Observations from this community registry suggest that mortality after direct angioplasty is low and the use of emergent surgery is infrequent. Outcome in this registry study was dependent on initial hemodynamic findings and infarct location but not on the presence of on-site surgery. Compared with thrombolytic therapy, the incidence of complications was the same or lower, but this needs confirmation in randomized trials.

Myocardial infarction, thrombolytic therapy, and stroke. A community-based study. The MITI Project Group.

BACKGROUND: Thrombolytic therapy used in patients with acute myocardial infarction may increase the risk of stroke. Scant information is available from community-based studies. SUMMARY OF REPORT: Among 5,635 consecutive patients admitted with acute myocardial infarction to hospitals in Seattle and surrounding suburban King County, Washington, 116 (2.1%) experienced strokes during hospitalization. Of these strokes, 82 (71%) were ischemic and 34 (29%) were hemorrhagic, defined by a patient's having had a computed tomographic scan of the head that showed blood. Thrombolytic therapy was given to 1,413 of these patients (25%) and was associated with increased risk of hemorrhagic stroke but reduced risk of ischemic stroke. The relative risk of stroke with thrombolytic therapy was estimate using multiple logistic regression to adjust for potential confounding factors. The adjusted relative risk for hemorrhagic stroke was 3.6 (95% confidence interval [CI], 1.7-8.0); for ischemic stroke, 0.4 (95% CI, 0.2-0.9); and for overall stroke, 1.0 (95% CI, 0.6-1.7). The adjusted risk for death from any cause following stroke was 3.0 (95% CI, 1.4-6.4). CONCLUSIONS: Although thrombolytic therapy had little effect on the overall occurrence of stroke, thrombolytic therapy increased the risk of stroke death because more patients with hemorrhagic than ischemic strokes died during their hospitalization. The rates of hemorrhagic stroke with thrombolytic therapy reported in the present study are higher than those reported in clinical trials in which treatment is given to select patients under strict protocols.

A method of assigning scores to the components of a composite outcome: an example from the MITI trial.

After obtaining expert opinion to assign weights to the individual components of a composite outcome, scores are assigned in such a way as to reflect these weights as well as to optimize the power for specified alternatives.

Ventilation skills of emergency medical technicians: A teaching challenge for emergency medicine.

We assessed the ability of 64 emergency medical technicians (EMTs) to ventilate a resuscitation manikin with a bag valve mask and with a pocket face mask to determine if their skill levels met the American Heart Association standard of 12 ventilations per minute, each with a tidal volume of 800 mL or more. All ventilation attempts were made during ongoing chest compressions (60 per minute). A successful ventilation was defined as a tidal volume of 800 mL +/- 40 mL. In a preliminary skills assessment, EMTs averaged 4.8 attempts with the bag valve mask and 2.9 attempts with the pocket face mask before a successful ventilation (P less than .01). In a formal skills assessment that lasted two minutes, successful ventilations per minute averaged 8.3 with the bag value mask and 9.9 with the pocket face mask (P less than 0.1). EMTs passed if they averaged ten or more successful ventilations per minute; 67% passed with the bag valve mask and 77% with the pocket face mask (NS). During a ten-minute extended skill assessment the EMTs averaged 9.6 ventilations per minute with the bag valve mask and 9.5 with the pocket face mask (NS). EMTs achieved initial success and maintained continued success better with the pocket face mask, but a reasonably high percentage (67%) met an objective standard when using the bag valve mask. We propose that objective standards be used to test the skills of EMTs for any ventilatory adjunct that they are permitted to use.

Survival of out-of-hospital cardiac arrest with early initiation of cardiopulmonary resuscitation.

Records on 1,297 people with witnessed out-of-hospital cardiac arrest, caused by heart disease and treated by both emergency medical technicians (EMTs) and paramedics, were examined to determine whether or not early cardiopulmonary resuscitation (CPR) initiated by bystanders independently improved survival. Bystanders initiated CPR for 579 patients (bystander CPR); for the remaining 718 patients, CPR was delayed until the arrival of EMTs (delayed CPR). Survival was significantly better (P less than 0.05) in the bystander-CPR group (32%) than in the delayed-CPR group (22%). Multivariate analysis revealed that the superior survival in the bystander-CPR group was due almost entirely to the much earlier initiation of CPR (1.9 minutes for the Bystander-CPR group and 5.7 minutes for the delayed-CPR group; P less than 0.001). There were significantly more people with ventricular fibrillation (VF) in the bystander-CPR group (80%) than in the delayed-CPR group (68%); and, for people in VF, the survival rate was significantly better if they had received bystander-CPR (37% versus 29%). The authors conclude that early initiation of CPR by bystanders significantly improves survival from out-of-hospital cardiac arrest, and they suggest that it may do so by prolonging the duration of VF after collapse and by increasing cardiac susceptibility to defibrillation. The benefit of this early CPR, however, appears to exist within a rather narrow window of effectiveness. It must be started within 4-6 minutes from the time of collapse and must be followed within 10-12 minutes of the collapse by advanced life support in order to be effective.

Out-of-hospital cardiac arrest: significance of symptoms in patients collapsing before and after arrival of paramedics.

The authors retrospectively studied victims of sudden cardiac death who experienced cardiac arrest before and after arrival of emergency personnel in order to define possible etiologic factors. There were 265 patients in the arrest-after-arrival (AAA) group and 414 patients in the arrest-before-arrival (ABA) group. All patients in the AAA group had symptoms prior to cardiac arrest. Approximately half the patients in the ABA group had symptoms. The presence or absence of symptoms prior to cardiac arrest appeared strongly associated with the cardiac rhythm at time of collapse and with discharge. Of patients with symptoms, 61% were in ventricular fibrillation or ventricular tachycardia, as compared with 93% of patients without symptoms (P less than 0.001); 32% of patients with symptoms were discharged, as compared with 57% of patients without symptoms (P less than 0.001). These data suggest two potential etiologies for sudden cardiac arrest; thrombosis/ischemia (associated with symptoms) and electrical (associated with no symptoms). Inasmuch as the AAA group represented 14% of witnessed cardiac arrests, patients with symptoms of myocardial ischemia or infarction should be aggressively treated.

The location of collapse and its effect on survival from cardiac arrest.

Survival from cardiac arrest is higher when the collapse occurs outside the home. Of 781 patients collapsing at home, 101 (13%) survived to hospital discharge. This compared with 66 survivors among 248 (27%) patients arresting outside the home (P less than .001). Patients collapsing outside the home were younger and more frequently were men. Cardiac arrests outside the home were more often witnessed, more likely to have bystander CPR, less often preceded by symptoms, and the collapsing rhythm was more frequently ventricular fibrillation. Mean time to CPR was shorter. Multivariate logistic regression showed that the effect of location on survival was still statistically significant, although diminished, after adjusting for the above variables (P less than .01). We speculate that comorbidity, underlying etiology, and activity level may explain the remaining difference. Because 76% of arrests occur in the home, efforts to increase the frequency of bystander-CPR through targeted and dispatcher-assisted CPR programs are warranted.

Training lay persons to use automatic external defibrillators: success of initial training and one-year retention of skills.

This study was conducted to determine the feasibility of recruitment of lay persons to use automatic external defibrillators (AEDs), the effectiveness of their initial training, and the need for and frequency of retraining over time. Volunteers (n = 146), recruited from a variety of settings, included security personnel and administrative staff from large corporate centers, supervisors from senior care and exercise facilities, and employees in high-rise office buildings. Seven sites for 14 AEDs were recruited. In a single, two-hour class, participants learned to identify and respond to cardiac arrest, to notify emergency personnel, to retrieve and attach the semiautomatic (shock advisory) AED, and to respond to instructions presented on the display screen of the device. A skills check list was used to grade each student on performance of cardiopulmonary resuscitation, operation of the device, and time required to deliver an electric countershock. Retesting was performed one or more times after initial training to assess skill retention. The study lasted 1 year. All age groups, both sexes, and each responder type easily learned to operate the AED, with a trend for lower performance scores in people aged greater than 60 years. Performance time and skills declined significantly after initial training, but returned to satisfactory levels after one retraining session and were even higher after two retraining sessions. With retesting, errors that would have prevented delivery of countershocks to patients in ventricular fibrillation were rare (six of 146 tests, 4%). During the year of this study only three cardiac arrests occurred in the study sites.(ABSTRACT TRUNCATED AT 250 WORDS)