Patients with acute ST-segment elevation myocardial infarction (STEMI) needing prehospital cardiopulmonary resuscitation (CPR) have a very high adverse-event rate. However, little is known about the fate of these patients and predictors of mortality in the era of early reperfusion therapy. From March 2003 through December 2004, 2,317 patients with prehospital diagnosed STEMI were enrolled in the Prehospital Myocardial Infarction Registry. One hundred ninety patients (8.2%) underwent prehospital CPR and were included in our analysis. Overall 90% of patients were treated with early reperfusion therapy, 56.3% received prehospital thrombolysis and 1/2 of these patients received early percutaneous coronary intervention after thrombolysis, 28.4% of patients were treated with primary percutaneous coronary intervention, and 5.3% received in-hospital thrombolysis. Total mortality was 40.0%. The highest mortality was seen in patients with asystole (63%) or pulseless electric activity (64%). Independent predictors of mortality were need for endotracheal intubation and older age, whereas ventricular fibrillation as initial heart rhythm was associated with survival. In conclusion, in this large registry with prehospital diagnosed STEMI, incidence of prehospital CPR was about 8%. Even with a very high rate of early reperfusion therapy, in-hospital mortality was high. Especially in elderly patients with asystole as initial heart rhythm and with need for endotracheal intubation, prognosis is poor despite aggressive reperfusion therapy.
Acute myocardial infarction is one of the main reasons for out-of-hospital cardiac arrest and need for prehospital resuscitation. Patients with acute ST-segment elevation myocardial infarction (STEMI) and prehospital cardiopulmonary resuscitation (CPR) represent a selected subgroup with a very high adverse-event rate. Predictors of mortality in these patients are of great interest to optimize prehospital and hospital sequences. In patients with STEMI without CPR, primary percutaneous coronary intervention (PCI) and fibrinolysis are most effective within the first golden hour after onset of symptoms. Therefore, especially patients at very high risk, namely patients with STEMI and prehospital CPR, may benefit from an early and aggressive reperfusion strategy. Therefore, we analyzed the Prehospital Myocardial Infarction Registry (PREMIR), which included patients with STEMI diagnosed in the prehospital phase and evaluated the subgroup of patients with need for prehospital CPR.
Methods
The PREMIR was a collaboration of the Arbeitsgemeinschaft Leitende Kardiologische Krankenhausärzte and the Bundesverband der Arbeitsgemeinschaft der Notärzte Deutschlands. The design of the registry is reported in more detail elsewhere. In brief, consecutive patients were included who presented with typical chest pain or equivalent symptoms >20 minutes within 24 hours after symptom onset, prehospital 12-lead electrocardiogram with STE in ≥2 contiguous leads (≥2 mm precordial leads, ≥1 mm limb leads) or left bundle branch block (LBBB) and prehospital diagnosis, and treatment by an emergency physician. The present analysis includes consecutive patients with STEMI and prehospital resuscitation. Data on patients’ characteristics were recorded, including age, gender, cardiovascular risk factors, concomitant diseases, previous MI, previous stroke, and previous cardiovascular interventions and data on onset of symptoms, time to call, time to arrival of ambulance, prehospital delay, and time to start of reperfusion therapy. Major cardiovascular and cerebrovascular adverse events until hospital discharge were also recorded. Those data were analyzed and processed centrally in the Institut für Herzinfarktforschung, Ludwigshafen. Source data verification was performed by comparison of the registry data to ambulance and hospital records in randomly selected 230 patients in randomly selected participating centers. Ambulance protocols of all patients with STEMI and prehospital CPR also were reviewed by 3 independent investigators. Initial heart rhythm, electrocardiograms, duration of cardiac massage, number of defibrillations, use of catecholamines, and need for endotracheal intubation were evaluated in those patients. The registry was approved by the ethical committee of the Landesärztekammer Mainz. STEMI was diagnosed in the presence of the 3 following criteria: persistent angina pectoris for ≥20 minutes, electrocardiographic criteria described earlier or presence of LBBB, and increases of cardiac markers creatine kinase-MB or troponins. Reinfarction was diagnosed in case of recurrent angina pectoris with re-elevation of creatine kinase-MB or angiographic demonstration of occlusion of the infarct vessel. Stroke was defined as the occurrence of persistent specific neurologic deficits. Major bleeding was defined as any intracranial bleeding, bleeding associated with need for blood transfusion, or any other clinically relevant bleeding with need for intervention as judged by the investigator. Data are presented as absolute numbers, percentages, or medians with 25th and 75th percentiles as appropriate. Categorical values were compared by chi-square test and continuous variables were compared by 2-tailed Wilcoxon rank-sum test. A p value <0.05 was considered statistically significant. For identifying independent predictors of mortality, logistic regression analysis was performed using forward parameter selection. All statistical analyses were performed using SAS 9.1 (SAS Institute, Cary, North Carolina).
Results
From March 2003 through December 2004, 2,317 patients with prehospital diagnosed STEMI were enrolled in the PREMIR. One hundred ninety patients (8.2%) needed prehospital CPR. Baseline characteristics and prehospital findings of patients with and without CPR are listed in Table 1 . Patients with STEMI and prehospital resuscitation were younger and more often had an anterior MI or LBBB compared to patients with STEMI without prehospital resuscitation. Table 2 presents adjunctive prehospital medications. Patients with STEMI and prehospital CPR received aspirin less often. Median intervals are listed in Table 3 . Intervals from symptom onset to emergency call and from symptom onset to 12-lead electrocardiography were shorter in patients with STEMI and prehospital CPR. Main reasons for CPR in patients with STEMI were ventricular fibrillation and asystole. Initial therapies applied in the prehospital phase are listed in Table 4 . Planned primary PCI and oral anticoagulation were the main reasons for withholding prehospital fibrinolysis. Figure 1 depicts initial prehospital and hospital reperfusion strategies and prehospital and hospital mortalities according to different reperfusion therapies in patients with STEMI and prehospital CPR. Overall rate of reperfusion therapy in patients with STEMI and CPR was 90%. Prehospital mortality did not differ between patients with STEMI receiving prehospital fibrinolysis and patients not receiving prehospital fibrinolysis (5.6% vs 4.8%, p = 0.81). Overall mortality in patients with STEMI and prehospital resuscitation was 37.1% (66 of 178), reinfarction occurred in 8.5% (15 of 176), stroke in 2.3% (4 of 175), and major bleeding in 3.4% (6 of 175). Figure 2 shows hospital mortality according to initial heart rhythm. To identify predictors for mortality, a stepwise multivariate analysis was performed. Need for endotracheal intubation (odds ratio [OR] 16.8, 95% confidence interval [CI] 2.2 to 131.4) and older age per year (OR 1.037, 95% CI 1.006 to 1.069) were independent predictors for mortality. Ventricular fibrillation (OR 0.313, 95% CI 0.128 to 0.766) as initial heart rhythm was associated with survival, whereas mode of reperfusion therapy had no significant impact on prognosis.
| Baseline Characteristics | Patients With STEMI Receiving Prehospital CPR | Patients With STEMI Not Receiving Prehospital CPR | p Value |
|---|---|---|---|
| (n = 190) | (n = 2,127) | ||
| Demographics | |||
| Age (years) | 64.0 (53–72) | 66.0 (55–75) | <0.05 |
| Men | 74.2% (141/190) | 70.0% (1,489/2,127) | 0.22 |
| Body weight (kg) | 83.0 (75–90) | 80.0 (70–90) | <0.001 |
| Height (cm) | 175 (170–180) | 172 (165–178) | <0.01 |
| Medical history | |||
| Previous myocardial infarction | 14.5% (27/186) | 19.4% (410/2,113) | 0.1 |
| Previous percutaneous coronary intervention | 7.0% (13/186) | 10.0% (211/2,113) | 0.19 |
| Previous coronary artery bypass grafting | 5.4% (10/186) | 4.2% (89/2,113) | 0.45 |
| Coronary risk factors | |||
| Hypercholesterolemia | 24.7% (46/186) | 36.1% (762/2,113) | <0.01 |
| Smoker | 31.7% (59/186) | 39.0% (824/2,113) | 0.05 |
| Hypertension | 53.8% (100/186) | 60.6% (1,281/2,113) | 0.07 |
| Diabetes mellitus | 18.8% (35/186) | 22.9% (484/2,113) | 0.2 |
| Prehospital findings | |||
| Anterior myocardial infarction | 54.3% (102/188) | 44.9% (940/2,093) | <0.05 |
| Posterior myocardial infarction | 37.8% (71/188) | 51.3% (1,073/2,093) | <0.001 |
| Left bundle branch block | 8.5% (16/188) | 4.3% (90/2,093) | <0.01 |
| Patients With STEMI Receiving Prehospital CPR | Patients With STEMI Not Receiving Prehospital CPR | p Value | |
|---|---|---|---|
| (n = 190) | (n = 2,127) | ||
| Aspirin | 81.2% (151/186) | 90.5% (1,924/2,125) | <0.0001 |
| Clopidogrel | 0.6% (1/178) | 2.1% (42/2,045) | 0.17 |
| Heparin | 82.7% (153/185) | 84.9% (1,796/2,116) | 0.43 |
| Glycoprotein IIb/IIIa inhibitors | 4.0% (7/176) | 3.2% (65/2,040) | 0.57 |
| Median Intervals (min) | p Value | ||
|---|---|---|---|
| Patients With STEMI Receiving Prehospital CPR | Patients With STEMI Not Receiving Prehospital CPR | ||
| (n = 190) | (n = 2,127) | ||
| Symptom onset to call | 14.0 (4.0–40.0) | 78.0 (32.0–233.0) | <0.0001 |
| Symptom onset to 12-lead electrocardiography | 45 (30.0–73.0) | 100.0 (51.0–253.0) | <0.0001 |
| Call to arrival of ambulance on scene | 8.0 (6.0–12.0) | 9.0 (6.0–13.0) | 0.18 |
| Electrocardiography until admission to hospital | 35.0 (20.0–51.0) | 32.0 (23.5–45.0) | 0.05 |
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