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Epidemiological records suggest that Seattle's drop in out-of-hospital cardiac arrest (OHCA) survival during the pandemic could be largely explained by indirect factors such as treatment delays, not acute SARS-CoV-2 infections.

While instances of EMS-treated OHCA tended to track closely with community SARS-CoV-2 levels and acute SARS-CoV-2 infection in 2020-2021, only approximately 5% of people with OHCA, whether treated or dead on arrival (DOA), actually had evidence of COVID-19, reported researchers led by Jennifer Liu, MPH, of Public Health-Seattle & King County in Washington.

The group estimated that acute infection was responsible for 18.5% of the downturn in OHCA survival rates when comparing prepandemic (2018-2019) versus pandemic (2020-2021) periods. In contrast, 68.2% of the survival decline was mediated by adverse trends in so-called "Utstein elements" such as public location of OHCA, witness status, non-EMS automated external defibrillator use, and EMS response intervals.

"In this cohort study of COVID-19 and OHCA, a substantial proportion of the higher OHCA incidence and lower survival during the pandemic was not directly due to SARS-CoV-2 infection but indirect factors that challenged OHCA prevention and treatment," the investigators concluded from their study, published in .

"Notably, the pandemic challenged multifaceted conventional cardiovascular prevention and discouraged and delayed 911 use because of fear of contracting SARS-CoV-2 during emergency care," Liu and colleagues wrote. "One pandemic phenomenon that has been reported is a decline in acute ST-elevation myocardial infarction, perhaps related to patient reticence to seek emergency care. This behavior might translate to an increase in OHCA as disease progresses from ischemia to terminal arrhythmia resulting from treatment delays."

Excess OHCA mortality may also be attributed to fewer witnessed and public location OHCA events due to social isolation during the pandemic, study authors suggested. They added that local system-level changes in professional response and care likely affected OHCA survival.

"[King County EMS] practitioners added N-95 masks and gowns to eye protection and gloves as part of the updated personal protective equipment protocol for resuscitation. The approach delayed patient access by about a minute and translated to lower survival, highlighting the exquisitely time-sensitive nature of resuscitation," according to Liu's group.

The approach likely aligned with the American Heart Association (AHA)'s interim guidance recommending special precautions when resuscitating people in cardiac arrest with known or suspected COVID-19 infection. In the March 2020 statement, use of personal protective equipment (PPE) was urged during CPR, endotracheal intubation, non-invasive ventilation, and other aerosol-generating procedures.

It wasn't until October 2021 that the AHA's advice shifted to prioritize timely CPR on cardiac arrest patients with known or suspected COVID-19 over resuscitators donning PPE.

The Seattle group acknowledged that King County EMS did not adopt tele-coaching of bystander CPR, transition to mechanical CPR, or modify strategies of advanced airway management in face of the pandemic.

"The overarching goal was to retain practiced choreography that is integral in the teamwork required for successful resuscitation. We were also buoyed by hospital postresuscitation efforts to continue interventional coronary evaluation and temperature management, although there was evidence that the relative timing of these interventions changed between prepandemic and pandemic periods," the authors noted.

The region showed no change in median age of OHCA patients, proportion female, bystander CPR, and presenting arrest rhythm during COVID-19.

In hospitals, the use of targeted temperature management grew during this time to 65.0%, up from 59.3% in 2018-2019. The number of patients undergoing coronary angiogram stayed stable, though fewer patients had this done in the first 24 hours after OHCA during the pandemic.

For their retrospective cohort study, Liu's group analyzed records from Seattle and King County, Washington, covering adults with nontraumatic OHCA attended by EMS from 2018 to 2021. Of the 13,081 patients with OHCA, 7,102 were DOA and 5,979 were treated by EMS.

Among EMS-treated patients (median age 64.0 years, 64.6% men), 17.2% survived to hospital discharge.

Between the prepandemic and pandemic periods, the total number of people with OHCA increased 19.0% from 5,963 to 7,118, corresponding to an incidence increase from 168.8 to 195.3 events per 100,000 person-years. There was a 27.2% increase in patients who were DOA and a 10.8% rise in EMS-treated patients with OHCA during the pandemic, study authors reported.

Odds of survival to hospital discharge fell from 19.2% prepandemic to 15.4% during the pandemic (OR 0.80, 95% CI 0.70-0.92).

Those with OHCA and documented SARS-CoV-2 infection had lower likelihood of survival compared with those without acute infection (6.2% vs 16.0%).

Liu and colleagues acknowledged that COVID testing was not comprehensive in their cohort, so the prevalence of acute infection may have been underestimated. Whether their Seattle-area findings apply to other geographic locations is also unclear.

"A better understanding of the predominant factors is important so that public health, clinical medicine, and emergency response can prioritize efforts," the investigators stressed.

"For example, excess OHCA incidence due directly to SARS-CoV-2 infection would direct resources to more effective prevention and treatment of COVID-19, whereas indirect pandemic factors would emphasize efforts supporting more general cardiovascular prevention and care and encourage persons with warning symptoms not to delay activating 911," the team wrote.

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