Pre-hospital electrocardiogram in patients with acute myocardial infarction during the COVID-19 pandemic

Primary percutaneous coronary intervention (PCI) represents the preferred revascularization strategy among patients with acute ST-segment elevation myocardial infarction (STEMI). A decline in the rates of primary PCI has been observed globally during the outbreak of coronavirus disease 2019 (COVID-19).¹ Fear of exposure to in-hospital infection has been hypothesized, as the main mechanism of this phenomenon and in conjunction with a late response of an overcharged emergency medical service (EMS) may have contributed to a delayed presentation of patients with STEMI.² However, a formal assessment of initial electrocardiograms (ECGs) among patients with STEMI during the COVID-19 pandemic is still lacking. We therefore compared pre-hospital ECGs of patients with STEMI hospitalized in Italy after the first reported case of COVID-19 on 21 February 2020 with data from the same period in 2019 to identify potential changes between the two periods.

Pre-hospital ECGs were obtained from the STEMI care network in the Campania region covering an area of about 5.8 million residents. Patients with STEMI were identified in the field through the EMS using a 12-lead ECG equipment available in the ambulance systems. A wireless transmission of pre-hospital ECGs for physician interpretation was performed by the EMS at the scene. De-identified ECGs were analysed by two expert reviewers who were blinded to date of recording. Pathological Q-waves were defined as a Q-wave with a duration ≥40 ms and/or depth ≥25% of the R-wave in the same lead or the presence of a Q-wave equivalent.³ These criteria have been shown to be associated with final infarct size at cardiac magnetic resonance.³ For all conventional STEMI, the timing of STEMI onset was estimated with the Anderson–Wilkins (AW) acuteness score, ranging from 1 (least acute) to 4 (most acute)⁴ (see Supplementary Methods).

Continuous data are reported as mean ± standard deviation and compared using Student’s t-test. Categorical data are reported as frequencies and percentages and compared using the χ² test or Fisher’s exact test as appropriate. Agreement between reviewers was estimated by Cohen’s kappa. Statistical analysis was performed with Stata 14.2 (StataCorp, College Station, TX, USA).

From 21 February 2020 to 16 April 2020, a total of 3239 pre-hospital ECGs were recorded by the emergency medical system and 167 (5.15%) were classified as STEMI. During the same period in 2019, 3505 pre-hospital ECGs were recorded and 196 (5.59%) were classified as STEMI. There was no difference between the two study periods in terms of age, gender, type (conventional vs. non-conventional), and location of STEMI. Pathological Q-waves were present in 54.5% of ECGs recorded during the COVID-19 period compared with 22.1% of ECGs recorded in the same period in 2019 (risk difference 32.3, 95% confidence intervals 21.2–43.5 percentage points; Figure 1, Panel A). There was also an increase in the mean number of Q-waves during the COVID-19 compared with the control period (1.4 vs. 0.9; P < 0.001; Figure 1, Panel B). These findings remained similar when QS and qR complexes were analysed separately. Consistently, the AW score was significantly lower during the COVID-19 period (2.4 vs. 2.8; P < 0.001; Figure 1, Panel C). The agreement between reviewer for pathological Q-waves and the AW score was good (kappa 0.95 and 0.86, respectively).

Figure 1.

Main characteristics of prehospital ECGs in patients with STEMI before and after COVID-19 outbreak.

Our data indicate that pre-hospital ECGs of patients with STEMI during the COVID-19 pandemic presented more frequently with signs of late ischaemia compared with the equivalent period in 2019. Approximately, one of two patients had already pathological Q-waves in the initial ECG. The AW acuteness score is superior to patient history (historical timing) in predicting myocardial salvage and mortality after reperfusion in patients with STEMI, thus explaining the higher mortality rate and the increased risk of infarct-related complications observed during the COVID-19 pandemic.⁵

The main limitations of our analysis are related to the short observational period, lack of information about time from symptoms onset to first medical contact, and clinical follow-up outcomes. However, a substudy of the DANAMI-2 trial showed that ECG estimated duration of ischaemia is superior to subjective patient history in predicting myocardial salvage and prognosis after reperfusion therapy for STEMI.⁶ To date, this is the first study to provide analytical information on ECG characteristics in patients with STEMI after the outbreak of COVID-19.

Our findings support the hypothesis that COVID-19 outbreak was associated with a deferral of first medical contact among patients with STEMI, prompting the continuous need for public campaigns to increase awareness of ischaemic symptoms and confidence in the hospital organization to preserve their safety.

Supplementary material

Supplementary material is available at European Heart Journal: Acute Cardiovascular Care.

Conflict of interest: The authors reported no conflict of interest. Attilio Leone is supported by a reseacrh grant provided by the Cardiopath PhD program.