We performed an observational study of the prospective, national ACI-SEC Infarction Code Registry, which contains data on patients treated at 83 hospitals within Spain's 17 regional STEMI care networks. We analyzed the clinical characteristics of the patients included, times to reperfusion, treatment characteristics, and 30-day mortality rates. The patients in the registry were treated consecutively over a 3-month period (April 1 to June 30, 2019).

Patients for whom an Infarction Code was activated in any of the regional STEMI care networks and who met the following criteria were included in the study: a) diagnosis of acute coronary syndrome with ST-segment elevation, that is, symptoms compatible with acute coronary syndrome with ST-segment elevation on ECG, a new left bundle branch block, or suspected posterior infarction within 24hours of symptom onset; b) recovery from cardiorespiratory arrest of suspected coronary origin, or c) cardiogenic shock of suspected coronary origin.

The study variables were entered into a centralized online database and are shown in the supplementary data. All the variables are defined in the study protocol. Each hospital assigned a person to evaluate and add the data to the registry. The ACI-SEC Infarction Code Working Group also appointed a coordinator for each regional network to act as a liaison and clarify doubts. The statistical analyses were performed by the authors of this article.

The timelines from symptom onset to reperfusion were defined according to the European guidelines on STEMI management.2 For each case, the hospitals were asked to provide a subjective opinion on whether there had been an undue delay between the first medical contact and reperfusion (yes/no) and if so, to offer a reason. Code activations were considered inappropriate when, following evaluation on arrival at the pPCI center, the patient did not meet any of the clinical or electrocardiographic (ECG) criteria for STEMI.12 Appropriate activations were classified as clinical false positives when the definitive diagnosis was a condition other than STEMI and as angiographic false positives when no culprit lesion was detected.12 The study protocol was approved by the Infarction Code Working Group and the lead ethics committee. The committee considered it unnecessary to obtain informed consent as the anonymity of the data was guaranteed.

Continuous variables are expressed as mean ± standard deviation and categorical variables as frequencies and percentages. Between-group baseline variables were compared using the t test or chi-square test as appropriate. Times to reperfusion are expressed as median [interquartile range] and were compared using the Mann-Whitney U test. Statistical significance was set at P<.05. All statistical analyses were performed in STATA version 15IC (Stata Corp., USA).

In the 3-month study period, 5401 patients were treated within Spain's 17 regional STEMI care networks. The flow of patients according to their final diagnosis is shown in figure 1, together with a breakdown of the reperfusion strategy used in those diagnosed with STEMI (4366 patients, 80.8%). Overall, 3792 patients (87.5%) underwent pPCI, 189 (4.4%) underwent fibrinolysis, and 353 (8.1%) received no reperfusion therapy.

Figure 1.

Flowchart showing patients with Spanish Infarction Code activations from April to June 2019 for whom a definitive diagnosis was recorded. Also shown is the reperfusion strategy used in patients diagnosed with STEMI. NSTE-ACS, non–ST-segment elevation acute coronary syndrome; pPCI, primary percutaneous coronary intervention; STEMI, ST-segment elevation myocardial infarction.

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The flow of patients according to treatment decision taken during the first medical contact, treatment administered (pPCI, fibrinolysis, or no reperfusion), and final diagnosis is shown in figure 2.

Figure 2.

Flow chart showing patients with Spanish Infarction Code activations from April to June according to treatment decision during FMC, reperfusion strategy applied, and final clinical diagnosis. FMC, first medical contact; NSTE-ACS, non–ST-segment elevation acute coronary syndrome; pPCI, primary percutaneous coronary intervention; STEMI, ST-segment elevation myocardial infarction.

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The breakdown of code activations according to appropriateness, final diagnoses, and ECG findings is shown in figure 3. ECG findings and final diagnoses were available for 4820 activations and of these, 4571 (94.8%) were classified as appropriate. There were 3901 true positives for STEMI (80.9%), 580 clinical false positives, and 90 angiographic false positives.

Figure 3.

Flowchart showing patients according to appropriateness of code activation together with final clinical diagnosis and electrocardiographic findings in each case. True and false positives were calculated as a percentage of all the codes analyzed. AMI, acute myocardial infarcion; LBBB, left bundle branch block; RBBB, right bundle branch block.

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Code activation was classified as inappropriate in 249 cases; there were 183 true negatives and just 66 false negatives (1.4% of total).

The clinical characteristics of patients with a final diagnosis of STEMI vs another condition are summarized in table 1. STEMI was significantly more common in men, smokers, and patients without hypertension or a history of ischemic heart disease, PCI, or heart surgery. Patients diagnosed with a condition other than STEMI were significantly more likely to have ventricular tachycardia and asystole and to need mechanical ventilation during their first medical contact; mortality rates were also higher at this stage.

The clinical characteristics of patients diagnosed with STEMI are summarized according to reperfusion strategy in table 2, which also shows the characteristics of the first medical contact and the clinical timelines (from symptom onset to reperfusion).

Compared with patients who underwent pPCI, those treated with fibrinolysis (n=189) were younger, more likely to be men, and less likely to be treated at a specialized pPCI hospital. They were also more likely to have ventricular fibrillation and to die during the first medical contact. They had a shorter time from symptom onset to first medical contract. Median time from first medical contact to initiation of fibrinolysis was 36.5 [IQR, 20-68] minutes. Overall, 106 patients (56.1%) treated with fibrinolysis underwent rescue PCI, while 74 (39.2%) underwent deferred revascularization of the culprit lesion. Coronary angiography without revascularization was performed in 7 patients (3.7%); 2 patients (1.1%) did not undergo angiography as they died during the first medical contact. Reasons for performing fibrinolysis rather than pPCI were an estimated time to pPCI of >120minutes in 64% of patients and unavailability of pPCI in 19%. Other reasons were given for 17.3% of patients.

Compared with patients treated with pPCI, those who did not receive reperfusion therapy were older and more likely to be women, have pre-existing heart failure, and present with asystole or cardiogenic shock or die during the first medical contact.

Angiographic and procedure-related characteristics for STEMI patients treated with pPCI are shown in table 3. Radial access was used in >90% of cases; 63% of patients had single-vessel disease, while 28% required mechanical thrombectomy. The mean number of stents implanted was 1.30±0.72 per patient; bare-metal stents were used in just 7% of cases. Plain angioplasty or thrombectomy was used in 4.4% of revascularized patients who did not receive a stent. PCI was used to treat a nonculprit artery during pPCI in 6.8% of patients. Although 7.5% of patients presented with cardiogenic shock, a hemodynamic support device (mainly an intra-aortic balloon pump) was used in just 2.4% of cases. Most patients were treated with aspirin (97.6%) and P2Y12 receptor inhibitors (95.1%). Ticagrelor was the most widely used inhibitor (52.5%).

The timelines from symptom onset to reperfusion in STEMI patients treated with pPCI are shown in figure 4. The median times calculated were 66 [IQR, 30-165] minutes for symptom onset to first medical contact, 107 [IQR, 80-146] minutes for first medical contact to reperfusion, and 193 [IQR, 135-315] minutes for symptom onset to reperfusion. A time of <120minutes from first contact to reperfusion was observed in 71.4% of patients treated by emergency medical services, 48.6% of patients treated at a non-pPCI hospital, and 74.3% of patients treated at a pPCI hospital.

Figure 4.

Timelines from symptom onset to reperfusion in patients with ST-segment elevation myocardial infarction treated with primary percutaneous coronary intervention. IQR, interquartile range.

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Time from symptom onset to first medical contact in patients treated with fibrinolysis was 60 [IQR, 30-120] minutes. The other times were 36.5 [IQR, 20-68] minutes for first medical contact to initiation of fibrinolysis and 120 [IQR, 75-195] minutes for symptom onset to initiation of fibrinolysis. Median time from fibrinolytic administration to revascularization in the 106 patients who required rescue PCI was 165 [130-255] minutes. Coronary angiography was performed within 24hours in 86.4% of the 81 patients who underwent this procedure after effective fibrinolysis.

An undue delay from first medical contact to reperfusion (>120minutes) was reported for 44.7% of patients. The main reason given (in 18.5% of cases) was a delay in the initial diagnosis (figure 5). Time from first medical contact to ECG was >10minutes in 30.8% of patients.

Figure 5.

Reasons for undue delays between first medical contact and reperfusion. Observation of an undue delay between the first medical contact and reperfusion did not necessarily mean that reperfusion was not performed within the recommended 120minutes. In fact, reperfusion was performed within 120minutes of the first medical contact in 53.2% of cases, but 21.5% of these were considered to involve an undue delay. PCI, primary cutaneous intervention.

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Complications during first medical contact, cardiac catheterization, and subsequent hospitalization are shown in table 4.

In-hospital and 30-day mortality rates are shown in figure 4. Mortality was lower in patients diagnosed with STEMI than in those diagnosed with another condition (5.5% vs 7.3% for in-hospital mortality [P=.032] and 7.9% vs 10.7% for 30-day mortality [P=.009]). Respective rates according to the reperfusion strategy employed in the STEMI group were 4.8% and 6.8% for pPCI and 6.4% and 9.6% for fibrinolysis. Mortality was significantly higher in patients who not receiving reperfusion: 12.4% for in-hospital mortality and 18.2% for 30-day mortality (figure 6).

Figure 6.

In-hospital and 30-day mortality rates according to definitive diagnosis (STEMI or other) and reperfusion strategy in patients diagnosed with STEMI. pPCI, primary percutaneous coronary intervention; STEMI, ST-segment elevation myocardial infarction.

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This study has a number of limitations inherent to any multicenter observational study. Inaccuracies and misclassification, for example, can occur when data are collected and evaluated by individual centers, without centralized monitoring. Interventional cardiology data, however, are quite well standardized around the world and the online data entry form was designed to be intuitive and universally applicable. It should also be noted that STEMI patients treated outside the Infarction Code networks are not included in the registry, although the selection bias introduced is probably minimal due to their small number. Patients with subacute myocardial infarction who did not meet the criteria for emergent reperfusion were also not included. Although the data from the registry are from 2019, there have been no major organizational changes that would have affected the functioning of the networks in the last 2 years, or any significant changes to the European STEMI guidelines (published in 2017). In addition, a study conducted during the first wave of the coronavirus 2019 pandemic did not detect any changes to reperfusion strategies or time from first medical contact to reperfusion, although it did find an increase in STEMI-associated mortality, partly attributable to longer ischemia times.25