Background. Patients with cardiac arrest have been excluded from most randomized trials on percutaneous coronary intervention (PCI) for acute myocardial infarction (AMI). Objective. The aim of the study was to evaluate the outcome of patients undergoing primary PCI for acute myocardial infarction who suffered from cardiac arrest prior to the procedure, focusing the study on the influence of immediate paramedical/medical assistance on the outcome. Methods and Results. Sixty-three patients with ST-elevation AMI and previous cardiac arrest underwent primary PCI within 12 hours after symptom onset. Three groups of patients were defined: Group 1: Cardiac arrest before hospital admission, without immediate (< 1 minute) initiation of resuscitation maneuvers (n = 13); Group 2: Pre-hospital cardiac arrest with immediate initiation of resuscitation maneuvers (n = 14); Group 3: Cardiac arrest after hospital admission. The proportion of patients with ventricular tachycardia or fibrillation as documented initial rhythm was similar among the groups (77%, 79% and 83%, respectively), as well as the rate of angiographic success (92%, 93% and 86%, respectively). However, the incidence of cardiac events at 30 days was significantly higher in Group 1 than in Groups 2 or 3 (54%, 29% and 17%, respectively; p = 0.03), as well as the mortality rate at 30 days (46%, 21% and 18%, respectively; p = 0.06). Interestingly, the outcomes were not statistically different between Groups 2 and 3. In multivariate analysis, the independent predictors for mortality at 30 days for Group 1 were: multivessel disease, angiographic failure and cardiogenic shock. Conclusions. Combining immediate initiation of resuscitation maneuvers and primary PCI yields a very good clinical outcome in patients with AMI suffering from cardiac arrest.

       Primary percutaneous coronary intervention (PCI) is the best reperfusion strategy in patients with ST-elevation acute myocardial infarction (AMI).¹ This is mainly because it achieves a very high rate of successful recanalization of the infarct-related artery in a wide variety of clinical and angiographic situations,² but also because it virtually eliminates the risk of intracranial bleeding and reduces the incidence of mechanical complications.³
       Half of the patients who die from AMI do so early, before reaching a hospital, and in most cases because of a fatal ventricular arrhythmia.^4–6 Additionally, patients with previous cardiac arrest comprise a very high-risk subgroup among patients undergoing PCI for AMI.⁷ As PCI has become the first choice reperfusion strategy for AMI, the number of patients undergoing PCI for cardiac arrest secondary to AMI has increased. This constitutes not only an interesting, but also a high resource-consuming subgroup of patients, thus recognizing characteristics associated with clinical outcomes among this population would be of clinical interest. Despite these considerations, patients with prior cardiac arrest have been frequently excluded from trials on PCI for AMI.
       The objective of this study was to evaluate the outcomes of a population of patients undergoing emergent PCI for cardiac arrest secondary to AMI, as well as to identify short- and long-term predictors of mortality among these patients. Specifically, we focused the study on the influence of immediate paramedical/medical assistance on the outcomes of these patients. For this purpose, we conducted a study and long-term follow on 63 patients with AMI and previous cardiac arrest undergoing PCI within 12 hours of symptom onset.

Patients and Methods
       Study population. At our center, all patients with ST-elevation AMI presenting within 12 hours after symptom onset who undergo PCI are included in a prospective database and followed up at long-term. Additionally, some secondary centers refer patients with AMI and failed thrombolytic therapy to our hospital for rescue PCI. Between January 2000 and December 2003, 630 patients were included in this database. The study population is comprised of 63 patients fulfilling the following criteria: 1) cardiac arrest caused prior to PCI; 2) presence of ST-segment elevation > 0.1 mV in at least 2 adjacent leads of the 12-lead electrocardiogram, or presence of presumed new left bundle branch block; and 3) PCI within 12 hours after symptom onset. Patients with cardiac arrest during or immediately following PCI were excluded from the study, but there were no other exclusion criteria.

Cumulative survival in Groups 1, 2 and 3.

In the 27 patients suffering cardiac arrest before hospital admission, cardiac arrest occurred in the ambulance (n = 7), at home (n = 6), on the street (n = 6), at work (n = 5) or in public places (n = 3). Paramedics included no physicians, but were trained in cardiac resuscitation.
       Three groups of patients were defined as follows: Group 1: out-of-hospital cardiac arrest without immediate medical or paramedical assistance (less than or equal to 1 minute from cardiac arrest until initiation of resuscitation maneuvers; n = 13); Group 2: out-of–hospital cardiac arrest with medical or paramedical immediate assistance; (n = 14); and Group 3: cardiac arrest before PCI, but after hospital admission; (n = 36).
       Cardiac catheterization. Cardiac catheterization was performed by the femoral approach using a 6 Fr guiding catheter in most patients. Coronary stents, glycoprotein (GP) IIb/IIIa inhibitors, intra-aortic balloon counterpulsation pump, and thrombectomy and distal protection devices were used at the operator’s discretion. Because all patients were enrolled before 2004, drug-eluting stents were not used. Patients received heparin 100 IU/kg at the beginning of the procedure, and additional doses when necessary to maintain an activated clotting time > 300 seconds. In patients receiving GP IIb/IIIa inhibitors, both the initial bolus of heparin (50–70 IU/kg) and the target activated clotting time (200–250 seconds) were lower. Aspirin (250–500 mg as the initial dose, and 100–300 mg/day afterwards) was given to all patients. After coronary stent implantation, ticlopidine (500 mg as a loading dose and 250 mg b.i.d. for 1 month) or clopidogrel (300–600 mg as a loading dose, and 75 mg/day for 1 month) was also prescribed.
       The nonculprit vessel was catheterized first, followed by the infarct-related artery. In patients with multivessel disease, only the culprit vessel was treated, except in some cases where there was persistent ischemia and hemodynamic instability. Multivessel disease was defined as the presence of > 70% coronary stenosis by visual estimation (> 50% by quantitative coronary analysis) in more than 2 major coronary arteries. Left main disease was also codified as multivessel disease. The angiographic result was considered successful when < 30% residual stenosis associated with TIMI flow grade 2 or 3 was achieved, although the rates of TIMI 3 flow are also provided. The presence or absence of coronary risk factors was codified according to the previously known history provided by the patient and/or relatives. Long-term follow up was performed by outpatient clinic or telephone interview.
       Statistical analysis. The SPSS version 12 statistical package (Chicago, Illinois) was used. Continuous variables are expressed as mean ± standard deviation, and are compared with the Student´s t-test. Qualitative variables are expressed as percentages, and compared using the 2-test and Fisher’s corrections when appropriate. Cumulative survival was estimated using the Kaplan-Meier survival curves, and compared using the Log-Rank and Breslow tests. Associations are considered statistically significant when p < 0.05, though all p-values are provided.

Results
       Of the 630 patients, 63 (10%) had cardiac arrest before PCI secondary to ST-segment elevation AMI. Of those 63 patients, 13 (20.6%), 14 (22.2%) and 36 (57.2%) were included in Groups 1, 2 and 3, respectively, according to the time (less than or equal to 1 minute or > 1 minute) and place (before or after hospital admission) where resuscitation maneuvers were initiated, as described above.
       The proportion of patients in which the documented initial rhythm was ventricular tachycardia or ventricular fibrillation was similar among the Groups (77%, 79% and 83%, respectively). The remaining patients had asystole or electromechanical dissociation.
       Baseline clinical characteristics. Table 1 shows the differences in baseline clinical characteristics among the groups. A statistically significant difference was observed only in the time from symptom onset (p = 0.03), and the time from cardiac arrest to cardiopulmonary resuscitation (CPR) (p > 0.001).
       Angiographic results. There were no significant differences in angiographic features and procedural results (Table 2) among the Groups. Angiographic success was documented in 92%, 93% and 86% of patients included in Groups 1, 2, and 3, respectively, but differences were not statistically significant (p = 0.72). Clinical success was documented in 46%, 57% and 72% of patients included in Groups 1, 2, and 3, respectively (p = 0.21). Coronary stents and GP IIb/IIIa inhibitors were used in a similar proportion of patients among the three groups.
       Clinical outcomes. Clinical outcomes were significantly worse in Group 1 than in Groups 2 or 3, and were rather similar between Groups 2 and 3. The mean follow up period for the study population was 21 ± 19 months.
       Table 3 and Figure 1 show the short- and long-term clinical outcomes of patients included in Groups 1, 2 and 3. At 30 days, the overall mortality rate was 24% (Group 1 = 46%; Group 2 = 21%; Group 3 = 18%; p-value overall = 0.10; p 1 vs. 2–3 = 0.06; p 2 vs. 3 = 0.70), and the incidence of major adverse cardiovascular events (MACE) was 27% (Group 1 = 54%; Group 2 = 29%; Group 3 = 17%; p-value overall = 0.035; p 1 vs. 2–3 = 0.03; p 2 vs. 3 = 0.44). At 21 ± 19 months, overall mortality was 32% (Group 1 = 54%; Group 2 = 29%; Group 3 = 25%; p-value overall l = 0.15; p 1 vs. 2–3 = 0.06; p 2 vs. 3 = 0.58), and the rate of MACE was 38% (Group 1 = 62%; Group 2 = 36%; Group 3 = 31%; p-value overall = 0.07; p 1 vs. 2–3 = 0.03; p 2 vs. 3 = 0.49).
       Of the 20 deaths that occurred during follow up, 13 (65%) were due to cardiac failure and 7 (35%) were due to sepsis. The proportion of patients who died from sepsis was 71% (5/7), 25% (1/4) and 11% (1/9) in Groups 1, 2, and 3, respectively (p = 0.04).
       In the multivariate analysis, the independent predictors for mortality at 30 days in Group 1 (RR = 18.0) were: multivessel disease (RR = 11.6), angiographic failure (RR = 6.9) and cardiogenic shock (RR = 5.7).

Discussion
       Patients with prior cardiac arrest have been frequently excluded from trials on primary PCI for AMI. The main finding of our study is that among patients with AMI and cardiac arrest who are referred for PCI, those who suffer from cardiac arrest before hospital admission but who receive immediate assistance have very favorable clinical outcomes, similar to patients who suffer in-hospital cardiac arrest. Thus, combining immediate paramedical/medical assistance and PCI seems to provide excellent clinical outcomes in patients with cardiac arrest secondary to AMI.
       Each year, millions of patients around the world are evaluated for chest pain in emergency departments.⁸ Of these, approximately half will be classified as having an acute coronary syndrome.^8–9 On the other hand, approximately half of the deaths from AMI occur before hospital admission and within 1 hour of symptom onset.^10–11 In the majority of cases, ventricular tachycardia (VT) or ventricular fibrillation (VF) is the first documented rhythm.^4–6 During the acute phase of a myocardial infarction, 4–18% of patients suffer from VF.^12–16 In our study, patients from Group 1 had a significantly worse prognosis than those from Groups 2 or 3. The reasons are most likely related to the delay in initiating resuscitation maneuvers. Early defibrillation is critical to survival from cardiac arrest. Survival rates after VF secondary to cardiac arrest decrease approximately 7–10% with every minute that defibrillation is delayed,^17–32 and a survival rate as high as 90% has been reported when defibrillation is achieved within the first minute of collapse.^24–27 Basic CPR, however, is unlikely to convert VF to a normal rhythm. Early CPR is the best treatment for cardiac arrest until the arrival of an automatic external defibrillator and advanced cardiovascular life support care. These findings support the need to ensure the availability of automatic external defibrillators in public places.
Another finding of our study is that successful angiographic results were achieved in approximately 90% of cases in all three Groups. This is important, taking into consideration that patients with AMI and previous cardiac arrest are frequently excluded from thrombolytic therapy.

Conclusion
       Among patients who suffer from cardiac arrest secondary to AMI prior to urgent PCI, the prognosis is very favorable in those who had cardiac arrest outside the hospital and received immediate assistance, similar to those who had cardiac arrest in the hospital. In this regard, it is important to mention that aside from the daily effort made for primary prevention and modification of coronary artery disease risk factors, it is necessary to improve public access to defibrillation equipment so that automatic external defibrillators will be in the hands of trained laypersons who can attempt to prevent sequelae from sudden death caused by AMI. Our results show that combining immediate resuscitation and PCI is probably the best approach for these patients.

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