During the first wave of the COVID-19 pandemic in 2020, emergency departments (EDs) in Germany and worldwide reported decreasing case numbers [1]. These reports were in line with previous observations from the 2003 SARS pandemic in Taiwan where decreased case numbers were especially observed in less urgent cases as well as traumatological presentations and pediatric cases [2]. These findings have been confirmed in other international studies, but primarily have been examined during the onset of the pandemic phase in 2020 [1, 3‐7]. The main decrease in case numbers was again observed predominantly in non-urgent, non-admitted and younger cases [1].

However, also more severe diagnoses seemed to be decreasing along with the first pandemic wave: the phenomenon of decreasing case numbers was also observed for serious cardiovascular events such as myocardial infarction (MI) and stroke [1, 8, 9]. In a survey of the European Society of Cardiology, 70–90 percent of cardiologists worldwide reported having subjectively observed a delay in presentation to the ED or hospital in ST-elevation MI (STEMI) accompanied by a general reduction in cardiovascular presentations [9]. Further investigations confirmed these observations in different countries and additionally illustrated that case reduction was more pronounced in non-STEMI (NSTEMI) as compared to STEMI presentations [1, 10‐12]. Based on the hypothesis of a consistent incidence of STEMI and NSTEMI, the term “cardiac collateral damage of the pandemic” was used and the main concern of cardiologists worldwide was the failure to provide life-saving care for heart attacks due to non-presentation at the hospital.

Even though the above-illustrated evidence might lead to a delayed or avoided presentation to medical services, the assumption of a steady incidence of MIs in the population could be a matter of debate. Even though the evidence is still lacking it could be speculated that change in lifestyle due to pandemic control measures like social distancing, hygiene measures, different working conditions and stress reduction might have led to decreased cardiovascular events in general and thus findings might be influenced also by aforementioned factors. On the other hand, contradictory results have been shown on increasing numbers of out-of-hospital cardiac arrests in specific regions which would further strengthen the hypothesis of “collateral damage” [13‐17]. The first place of hospital-based clinical contact in case of suspected cardiovascular events is in most cases the ED. Thus, ED data might shed some light on the amount and relation of chest pain, suspected and confirmed MI presentations. Furthermore, avoided or postponed presentation during the first wave might have led to an increase of presentations with MI or long-term complications such as acute heart failure (AHF) in a later phase of the pandemic.

In this retrospective routine data analysis study, we aim to investigate the effects of the COVID-19 pandemic on ED visits in the whole year of 2020 as compared to the previous year in all ED presentations and in several subgroups with a special focus on the second pandemic wave in general and specifically in cardiovascular chief complaints and diagnoses.

In total, 2,216,627 presentations from 33 EDs were analyzed, whereof 1,038,157 took place in 2020 and 1,178,470 in 2019. The median case number over all EDs was 694 (IQR: 385-841) in 2019 and 604 (IQR: 348-743) in 2020 (Supplement Table 1). The median deviation in case numbers per clinic between 2019 and 2020 was − 14% (CI – 11–− 16%). After a marked drop in all ED visits in the first COVID-19 wave in spring 2020, case numbers normalized in summer and started to decline again in calendar week 39, 2020. Until the end of the year 2020 case numbers constantly decreased (Fig. 1).

The relative reduction of ED presentations was more pronounced in women and in younger patients. Relative reductions occurred to a lesser extent in older patients (maximum median change in older patients − 34%, 95% CI − 37%–− 32% in CW 14; in younger patients − 42%, 95% CI − 47%–− 40% in CW 14). An earlier re-incline of case numbers was observed in older patients, already starting from calendar week 16, and relative reduction was less pronounced during the second COVID-19 wave in autumn 2020 (maximum median change in older patients of − 18%, 95% CI − 24%–− 9% in CW 52; in younger patients of − 35%, 95% CI − 41%–− 30% in CW 52) (Supplement Figure 1 and 2).

In the entire observation period admissions for chest pain, myocardial infarction and heart failure were less affected but also decreased as compared to the previous year. No clear trend toward increasing case numbers after the reduction of case numbers in the first pandemic wave was observed.

In this observational, retrospective multicenter study analyzing German ED presentations during the SARS-CoV-2 pandemic year 2020 in comparison to the previous year (2019), we were able to illustrate that ED presentations, in general, declined more pronounced during the first pandemic wave in spring 2020 as compared to the second pandemic wave in autumn and winter 2020. The reduction was more pronounced in younger, less-urgent, non-admitted cases and in admissions to normal wards during both pandemic waves. However, more severe cases (older age, urgent and admitted cases) as well as admissions to IMC or ICU increased earlier and were less or even not at all reduced during the second pandemic wave. A further interesting finding was the increase of ICU admissions during the summer months of 2020, which might hint at some sort of collateral damage like postponed elective procedures or aggravation of disease due to delayed treatment.

Our observations are in line with other international data showing a decrease in general ED presentations during the first pandemic wave but shed further light into the trend of ED admissions after the initial reduction and during the second pandemic wave and onwards in 2020 [1, 3‐7, 22‐25].

Regarding cardiovascular diseases, ED presentations for chest pain, unstable angina or MI-exclusion declined slightly. Admissions to hospital with MI decreased during the first pandemic wave but increased again to comparable numbers in 2019 in the following CWs. This could be a sign of postponed ED presentation or collateral damage. These findings are in line with other studies reporting decreased numbers of hospital admissions and ED presentations with acute coronary syndrome and MI during the first pandemic wave [10‐12, 16, 26‐29]. There was no clear trend for a compensatory increase after the initial lockdown in 2020. However, MI numbers in our study also showed some alterations in the following CWs, which illustrates that these results might be caused by smaller case numbers in general and thus should not be over interpreted. Also hospital admissions for AHF, which might have been an indicator for missed MIs during the first pandemic wave, remained constant and thus the current data do not support the hypothesis of massive collateral damage to cardiovascular patients due to COVID-19 [9‐11, 13]. Nevertheless, it has to be taken into account that delayed ED presentations of patients with coronary artery disease might have long-term consequences over years rather than effects that can be seen within several months. In addition, evidence shows increased numbers of out-of-hospital cardiac arrests (OHCA), especially in high COVID-19 incidence regions, while areas with lower COVID-19 incidence were less affected. [13‐16, 30]

Several causative factors have been discussed and it is still unclear, whether the care-seeking behavior of patients was affected by the fear of COVID-19 infection in the hospital, whether social isolation measures triggered the absence of care-giving persons who usually would initiate hospital admission has partly caused this phenomenon, or whether there might also be a direct association between COVID-19 infection and cardiac arrest [17]. Nab et al. investigated reasons for delayed care-seeking behavior in Dutch ED patients and beneath the fear of a COVID-19 infection, also the ‘misperceptions of the accessibility of (ED) services and the legitimacy for seeking emergency care’ in times of sparse health care resources were reported as main drivers for avoiding ED consultancies in the first place [31]. Therefore, further research is necessary to investigate causal factors for non- and delayed care-seeking behavior and monitor cardiovascular morbidity over the following years. Despite that, also out of hospital mortality for other diseases such as neoplasms and endocrine diseases has been increased during the pandemic and warrants further investigation [32]. In the shed of these data it could be recommended that health information, in general, should clearly emphasize seeking care whenever patients experience severe symptoms or aggravation of the disease, also in times of sparse health care resources and high incidence of COVID-19 or other pandemic diseases.

However, it also needs to be mentioned that there is still too little evidence to interpret whether the reduced number of cases, especially of serious diseases as observed by several studies can be explained exclusively by a delayed or absent consultation of utilization of medical care structures [1‐5, 8‐12]. This hypothesis includes the implicit assumption of a constant incidence of cases which needs to be carefully investigated since it remains unclear whether the reduced number of ED visits may also be explained by declining incidences of certain diseases. Favorable environmental conditions and general hygiene measures, for example, most likely have reduced the number of respiratory infections in general [33]. Also infection-driven and other exacerbations of chronic diseases which might have otherwise required urgent treatment may have been reduced.

The moderate increase of ICU admissions from the ED during the summer months of 2020 is uncommon and warrants further investigation. Different factors should be discussed in the context of ICU admissions from the ED: first, there could have been an effect regarding the presenting ED cases (in-flow) but also alterations in hospital and ICU capacities need to be addressed (out-flow). Regarding the “in-flow” of ED cases its important to mention that in general, ED case numbers in the summer period are not much lower than in winter, but the severity of cases is usually lower with, for example, an increase in milder accidents and decreased numbers of severe respiratory infections. This case mix might have been affected by the first pandemic wave which might hint at some sort of collateral damage leading to more severe hospital cases than usually. Little is yet known about the impact of reducing inpatient services to clearing up capacities for COVID-19 cases on patients with other diagnoses than COVID-19 [34]. The elective procedures and prevented inpatient admissions which had to be postponed could also have led to increased use of other care providers, such as EDs, over the long-term and might result in an increase in ICU admissions from EDs.

Furthermore, there might be an effect of “staying at home” (in Germany) during the summer month of 2020, which might have led to alterations in the case mix. While especially some parts of the older population in Germany who tend to travel during the summer months might have reduced traveling in 2020 and could have presented to German EDs, which might have otherwise been treated elsewhere. Still there could also be an effect of non-presentation to EDs with milder symptoms, which might have resulted in disease progression over time and led to more severe cases during the summer months. The “out-flow” from EDs to ICUs is also affected by ICU capacities and should not be confused with overall ICU-admission rates.

Interestingly, data from German ICUs show a decrease in ICU admission and mechanical ventilation in COVID-19 patients in the second pandemic wave in comparison to the first pandemic wave [35]. Thus, the increase in ICU admissions is unlikely to be driven by COVID-19 infections and underlying causes need to be investigated in non-aggregated data allowing for further statistical procedures.

In Germany, the COVID-19 pandemic led to a marked drop in medical presentations to the nation’s EDs in the first and second wave of the pandemic, consistent in the whole country. The drop was more pronounced in less severe ED presentations, especially during the second wave. There were no clear signs of collateral damage regarding cardiovascular diseases even though long-term effects may occur only in the next years and need to be further monitored. In contrast, an unexpected increase in ICU admissions during the summer months of 2020, when COVID-19 admissions were low, could be a sign of collateral damage leading to severe hospital cases but the underlying causes and conditions require further investigation.