Dr Kevin McVaney was attending a daily operational briefing last April when a lieutenant told him there were “a lot of cardiac arrests last night”.
Another lieutenant chimed in and said they had seen a large number of cardiac arrests the night before.
McVaney, the medical director of the Denver paramedics in Colorado, was concerned. He looked at that week’s numbers and found that cardiac arrests were double their normal rate.
He told Al Jazeera that he recalled thinking: “Is this something really big happening or just a coincidence?” Cases of COVID-19 were on the rise and in a month they would peak.
This pattern was repeating across the United States, Europe, and elsewhere: a rise in cardiac arrests and then a rise in reported COVID cases.
A new study, published this month, collected data from 50 US cities as well as from major cities in the United Kingdom, France, Italy, New Zealand and Australia. The study showed that rises in out-of-hospital cardiac arrests were linked to rising COVID cases.
The study was based on data provided by the Metropolitan EMS Medical Directors Global Alliance, a surveillance network of emergency medical services (EMS) staff who voluntarily share data.
Dr Paul Pepe is global coordinator of the alliance and also a co-author of the study.
He told Al Jazeera that normally a 10 percent increase in cardiac arrests would be a cause for concern. But during last spring in the US, two-thirds of US cities in the study saw increases between 20 and 50 percent. In cities particularly hit hard, the rate doubled. New York’s rates went up on average 250 percent in April and on a single day, April 6, New York’s rate of cardiac arrests was 10 times the rate from the previous year.
Scientists noticed that both the COVID cases and cardiac arrests increased at a similar rate. Then, as cases dropped over the summer, so too did the number of cardiac arrests. In the cities relatively untouched by COVID in the spring, the rate of cardiac arrests had remained normal. But, in the summer, as epicentres shifted, those cities saw their COVID rates surge and so too did their rates of cardiac arrests.
A more accurate death toll?
There is no way to definitively prove the connection since almost none of those who had cardiac arrests were tested for COVID. But since this trend was seen in city after city, country after country, the study concludes the link is highly probable.
Doctors in Lombardy, Italy, were some of the few who did test those who had cardiac arrests for COVID, even after they had died. They looked at the data and concluded that while some were caused by indirect effects of the pandemic such as fear of going to the hospital, the vast majority of these excess cardiac arrests were likely caused by COVID itself.
Pepe explained that just as some people develop a cough or fever, or lose their sense of taste and smell, others may suffer a cardiac arrest.
“It’s one of the myriad of the chimeric presentations,” he said.
Since many of those who had cardiac arrests were not counted among COVID deaths, the data could potentially help to calculate a more accurate death toll.
Across the entire US, for example, the number of cardiac arrests in April increased 59 percent compared to previous years. As a result, it could add 4,307 people to the US COVID death toll for April alone. The authors of the new study estimate that the death toll from COVID could increase by 10 or 15 percent globally if excess cardiac arrests are included.
“It shows how grossly underestimated the death rate from COVID-19 truly is,” said Dr Aileen Marty, an outbreak response expert. “It’s important to put into perspective the risk of the virus.”
Early warning for COVID
Just as McVaney, who also co-authored the new study, noticed an increase in cardiac arrests in Denver before COVID cases began to spike, scientists have found that the surges in cardiac arrests were often noticeable before the surges in COVID cases.
This may be because of the delay in some symptoms or test results. Sometimes cardiac arrests surged only a few days before the COVID cases. In other instances it happened a week or more earlier.
An early warning could give EMS time to prepare. Responding to cardiac arrests uses up a lot of time, resources and can be traumatic for the medical staff.
“When you plan a strategy for the health system,” said Dr Simone Savastano, a cardiologist at Fondazione IRCCS Policlinico San Matteo in Pavia, Italy, “you have to take into account a possible increase in out-of-hospital cardiac arrests to strengthen the emergency system.”
Using EMS data in real time may also have wider benefits. A spike in cardiac arrests could provide an early warning for the virus itself. If an unusual jump in cardiac arrests indicates an impending surge in COVID cases, cities and EMS could respond accordingly.
“It may only give us a few days advance notice but maybe that would save some lives if we shut down earlier or tell people that we’re getting hit hard,” said Pepe.
EMS’s data could provide useful real-time insights and some scientists think it could be a tool for spotting clusters and waves as well as following how vaccine rollouts are affecting the population. It may even be part of a strategy to spot future pandemics.
“It’s very important to follow up the situation day by day, looking for signals, looking for a nominal increase of cardiac arrests,” said Savastano. He hopes that the Lombardia Cardiac Arrest Registry, to which his hospital provides data, will be used to spot impending waves. “In the near future we will have sufficient power to be predictive.”