Paul E. Litwin

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.

The Association between On-Site Cardiac Catheterization Facilities and the Use of Coronary Angiography after Acute Myocardial Infarction

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.

Delay Between Onset of Chest Pain and Seeking Medical Care: The Effect of Public Education

Thrombolytic therapy for acute myocardial infarction (AMI) is now routinely given in the emergency department and is being considered for pre-hospital care. Its effectiveness is dependent on how early it can be given after the onset of AMI. Maximal benefit, however, is not realized in many patients due to delay in seeking care. The effect of a public media education campaign (message) to shorten patient delay and increase use of emergency medical services (EMS) was evaluated prospectively in King County, Washington. We interviewed 401 patients admitted with possible AMI in the premessage period (4.5 months) and 489 in the postmessage period (4.5 months). The two groups were comparable in all factors except for discharge diagnosis of AMI (premessage, 34%; postmessage, 25%; P less than .01) and history of myocardial infarction or angina (premessage, 52%; postmessage, 43%; P less than .01). The proportion of patients who heard new information on AMI increased significantly in the postmessage period (premessage, 53%; postmessage, 74%; P less than .0001). The campaign, however, did not significantly shorten patient delay in seeking care (median delay: premessage, 2.6 hours; postmessage, 2.3 hours) or alter the distribution of patients in the less-than-two-hour, two-to-four-hour, and more-than-four-hour intervals. The rate of EMS use also was not significantly changed (premessage, 42%; postmessage, 44%). We conclude that a short-duration education campaign may increase AMI knowledge but does not seem to significantly alter patient behavior.

Effect of age on use of thrombolytic therapy and mortality in acute myocardial infarction

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)

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.

Accuracy of computer-interpreted electrocardiography in selecting patients for thrombolytic therapy☆

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.

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.

BackgroundIn 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 ResultsProcedure 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. ConclusionsObservations 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.

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.

Lay person use of automatic external defibrillation

The ability of lay persons to learn and retain defibrillation skills using an automatic external defibrillator (AED) was assessed. Thirty-four family members of cardiac arrest survivors were trained in CPR techniques and defibrillation, and evaluated for performance of skills immediately following training and at six-week and three-month follow-ups. All but two were successfully trained to complete three cycles of CPR interspersed with three defibrillatory shocks in an average of four minutes with the first shock delivered in an average of two minutes. Although there were decrements in the speed and quality of performance at each follow-up period (P less than .01), we conclude that most lay persons can learn to operate an AED safely and under simulated conditions provide defibrillatory shocks an average of eight minutes faster than typical response times of emergency medical technicians. These results suggest that AEDs can be placed in many homes of patients at high risk for cardiac arrest.