The IBERICA registry was designed as a prospective, population-based, continuous multicenter study of AMI involving individuals between 25 and 74 years of age residing in different areas of the Balearic Islands, Castilla-La Mancha, Catalonia, Murcia, Navarra, the Basque Country and Valencia. The study period was from 1 July 1996 to 31 December 1998. During this period there were no consensus-based protocols, and the hospital intervention strategy was fundamented upon the recommendations of the clinical practice guides of the American Heart Association.18 Quality control was established, guaranteeing homogeneity of the methods and of the data collected. The variables were recorded using non-electronic case report forms. The investigators were trained and certified in the study coordinating center.

The CI-IB17 is a prospective, community-based, continuous multicenter registry involving patients diagnosed with STE-ACS presenting an evolution of less than 24h, with activation of the Infarction Code, and seen in any setting of the public healthcare network. Within the intervention strategy, a primary percutaneous coronary intervention model was defined, establishing agreement of the protocols according to the clinical practice guides19 with all the implicated physicians and Departments. This registry was started on 1 March 2008. The variables are recorded in electronic format in a core database managed by the public Ib-Salut service of the Balearic Islands. In order to guarantee quality and homogeneity of data collection, all the investigators participating in the field work were trained and placed in charge of follow-up, data quality control and logistic support in the data monitoring processes. No new variables have been added in either registry.

The Autonomous Community of the Balearic Islands has a population of 1,106,049 inhabitants. A single reference hospital is available, with a hemodynamics laboratory, operating 24h a day, every day of the year. The Coronary Unit, ascribed to the Department of Intensive Care Medicine, has 8 beds. Up until November 2010, the reference center was Son Dureta University Hospital, which was replaced by Son Espases University Hospital, opened in December 2010.

The IBERICA study only included patients between 25 and 74 years of age. In order to allow comparison of the two cohorts, inclusion was limited to those patients with STE-ACS of anterior and inferior location that met electrocardiographic reperfusion criteria in both periods,18,19 limiting the age to 25–74 years, and comprising patients attended in the same reference hospital with a definitive diagnosis of AMI defined by myocardial enzyme values (e.g., creatine kinase) over twice the upper limit of normal, and with a follow-up period of 28 days from the time of the event. Patients from other centers were excluded.

The study variables were stratified into 5 groups:

• 1.

  Demographic characteristics: age, gender, cardiovascular risk factors (hypertension, smoking, dyslipidemia, insulin-dependent diabetes mellitus, non-insulin-dependent diabetes mellitus), history of ischemic heart disease (previous infarction or chest pain) and Killip class20 upon admission.

• 2.

  Reperfusion treatment: fibrinolysis and PA. The administration of aspirin, beta-blockers and angiotensin converting enzyme inhibitors (ACEIs) was also documented. The criteria for fibrinolysis in the IBERICA group were atypical chest pain for over 20min, with ST-segment elevation >1mm on two or more consecutive leads and within the first 24h of evolution.18 The CI-IB registry considered activation of the Infarction Code with the aim of performing mechanical reperfusion when the ECG tracing showed an ST-segment elevation of >1mm on at least two limb leads, or an elevation of at least 2mm on two or more contiguous chest leads, accompanied by typical chest pain for over 20min within the first 12h of evolution.19 Each patient was individualized after between 12 and 24h. In cases with an evolution of under three hours, with non-availability of the hemodynamics room, pre-hospital fibrinolysis was carried out in the medicalized ambulance (061), in the Emergency Care Department, on in the Department of Intensive Care Medicine.

• 3.

  The following time intervals were defined: time from symptoms onset until the first diagnostic ECG, and time from the first diagnostic ECG to reperfusion treatment.

• 4.

  Surgery was included as follow-up procedure 28 days after the event.

• 5.

  The complications studied during follow-up were: severe arrhythmias (ventricular fibrillation or sustained ventricular tachycardia), Killip class,20 stroke (hemorrhagic and/or ischemic) and mechanical complications (interventricular communication, mitral valve rupture and free wall rupture). Survival 28 days after the event was analyzed. Discharged patients were contacted in the outpatient clinic or by telephone.

The Research Ethics Committee did not consider the obtainment of informed consent to be necessary, since the registries were anonymous. Data dissociation was carried out to ensure anonymity, eliminating any link capable of identifying the patient. Confidentiality of the information was observed at all times as specified by Organic Act 15/1999 of 13 December, referred to Personal Data Protection, and Act 41/2002 of 14 November, regulating patient autonomy and the rights and obligation referred to clinical documentation and information.

A descriptive analysis was made of the variables, calculating the mean and standard deviation (SD) in the case of quantitative variables with a normal distribution, and the median and quartiles in those with a non-normal distribution. Qualitative variables in turn were reported as frequencies and percentages, with the corresponding 95% confidence interval (95%CI). The contrasting of hypotheses was based on the Student t-test, Mann–Whitney U-test and the chi-squared/Fisher exact test, respectively. Survival was analyzed based on the Kaplan–Meier method for estimating the curves after 28 days, and the log-rank test was used to compare both periods. Multivariate analysis was also performed based on a Cox proportional hazards model to explore the relationship between the most relevant variables, the prognostic and all the potentially confounding parameters, and mortality up to 28 days. In sum, patient age, gender, diseases associated to cardiovascular risk and their treatment, time from symptoms onset to first monitoring, initial reperfusion treatment received, severity upon admission (Killip class), and complications were analyzed. The results were expressed as hazard ratios with the corresponding 95%CI. Statistical significance was considered for p<0.05. The IBM® SPSS® version 22.0 statistical package was used throughout.

A total of 889 cases of AMI were recorded during the IBERICA-Mallorca study period, and of these 442 met the inclusion criteria. In the CI-IB registry we selected 847 consecutive patients with STE-ACS. Of these, 498 were included in the comparative analysis. The demographic and clinical characteristics are summarized in Table 1. The median age was 64 years in the IBERICA period and 58 years in the CI-IB period, with a predominance of males in both periods. There was a greater proportion of patients with hypertension and dyslipidemia, and a lesser proportion with previous angina and previous AMI, in the group of patients corresponding to the CI-IB period. No differences were observed in terms of the site of AMI or in Killip class upon admission.

In the patients subjected to reperfusion treatment, the introduction of the CI-IB led to shortening of the intervention times versus the IBERICA cohort. A significant decrease was observed in the median interval between symptoms onset and first ECG (90 vs 120min, respectively; p<0.001) and in the interval between first ECG and fibrinolysis treatment (35 vs 60min; p<0.001).

The percentage of patients that received no reperfusion treatment was lower in the CI-IB than in the IBERICA cohort (9.2% vs 45.9%; p<0.001). In the CI-IB group we observed an increase in the use of beta-blockers (76.1% vs 58.5%; p<0.001), ACEIs (67.5% vs 39.5%; p<0.001) and aspirin, though in the latter case statistical significance was not reached.

The in-hospital complications, including malignant ventricular arrhythmias and the poorest Killip classes (III–IV) were similar in both periods (Table 1).

The mortality rate after 28 days of follow-up was lower in the CI-IB cohort (7.2% vs 12.2%; hazard ratio 0.560; 95%CI 0.360–0.872; p=0.010). The survival curves are shown in Fig. 1. A Cox model was developed with the variables associated to mortality up to 28 days after the event (Table 2).

Figure 1.

Kaplan–Meier survival analysis after 28 days.

(0.11MB).

We also constructed Cox proportional hazards models referred to survival after 28 days corresponding to the CI-IB cohort versus the IBERICA group. The hazard ratio for the period was 0.658 (95%CI 0.429–1.009; p=0.055) on adjusting for age and gender, and 1.597 (95%CI 0.429–1.009; p=0.156) on introducing revascularization with fibrinolysis or PA (Table 3).

Comparisons between registries have important limitations, due to differences in the populations involved and in the inclusion criteria used. One of the important aspects of our study is that both registries represented exhaustive and consecutive cohorts of patients admitted alive to intensive care with ST-segment elevation. This has been an observational single-center study, and although the variables were documented on a prospective basis in both periods, certain differences in definition may have conditioned the results obtained. We consider that the findings of both registries illustrate the care process in the studied periods, though their comparative analysis may be conditioned by some limitations. On one hand, we cannot rule out the existence of bias referred to both the patient screening criteria and the exclusion criteria, fundamentally referred to the electrocardiographic reperfusion criteria used in the two periods. On the other hand, there may have been confounding variables related to the evolution of infarction from symptoms onset, or to the care process used, in the comparative analysis. Likewise, we do not know the efficacy of fibrinolytic treatment, particularly in the IBERICA cohort. These considerations mean that interpretation of the clinical results must be made with caution. Nevertheless, we believe that introduction of the invasive strategy program in STE-ACS produced the greatest difference in results between the two study periods.