The Link Between COVID-19 and Implantable Cardioverter-Defibrillator Shocks

Selçuk Adabag, MD

COVID-19 can have a devastating impact on the heart. Nearly one-fourth of patients hospitalized with COVID-19 are diagnosed with cardiovascular complications, contributing to about 40% of disease-related deaths. Sicker patients hospitalized with COVID-19 were noted to have cardiac arrhythmias and even cardiac arrests, but there’s also been an uptick in out-of-hospital cardiac arrests during the pandemic.

“It became very clear early in the COVID-19 pandemic that cardiac arrests were increasing,” said Selçuk Adabag, MD, professor in the University of Minnesota Medical School’s Department of Medicine. “We wanted to investigate the mechanism of these cardiac arrests.” 

Dr. Adabag, a cardiac electrophysiologist at the Minneapolis Veterans Affairs Medical Center, wanted to better understand if patients with implantable cardioverter-defibrillators (ICD) in areas with high prevalence of COVID-19 infections experienced an increase in ICD shocks during the outbreak. ICDs are implantable devices that detect arrhythmias (irregular heartbeats) — including ventricular tachycardia or fibrillation – and respond with electrical stimulation to help restore the heart’s natural rhythm, often saving the patient’s life. When the electrical response is triggered, patients usually feel an uncomfortable “shock” in their chest. While patients are encouraged to contact their physician if they experience a shock, the device does so automatically.

“Patients with an ICD have either a structural or an electrical heart disease,” Dr. Adabag said. “They’re also among individuals most vulnerable to viral infections like COVID-19 or influenza.”

Viral Link to Heart Health

Dr. Adabag’s research was possible through a partnership with scientists from Medtronic using its remote monitoring database (Carelink) and was published in the Journal of the American Heart Association. The study team assessed ICD shock frequency during peak COVID-19 activity in New York City, New Orleans and Boston. These metropolitan areas were chosen for having a large number of residents with ICDs and a high incidence of COVID-19 infection, since there was no way to determine if people who experienced a shock were positive for COVID-19. The study found that compared to 2019, there was a marked increase in ICD shocks during peak COVID-19 activity in all three cities and the rate of ICD shocks was two to three times higher depending on the location.

“Viral infections, like influenza and COVID-19, trigger an inflammatory and adrenergic  response,” Dr. Adabag said. “Our bodies get into fight or flight mode. Adrenaline increases clotting and can disrupt otherwise stable coronary blockages, causing heart attack or ischaemia, which is reduction of oxygen in certain areas of the heart.”

Many people who get really sick with COVID-19 or influenza will develop hypoxia, an insufficient blood oxygen level, which can cause ischaemia and trigger a heart attack or other arrhythmic events. 

“I think COVID-19 infections can trigger ICD shocks, but there were also other factors at play,” Dr. Adabag said. “We were in lockdown and felt distress. Many patients delayed medical care, and some may have run out of medications. All these factors could also have increased arrhythmias.”

Changing the Paradigm

Sudden cardiac death kills about 350,000 people annually in the U.S. alone, so it’s a big public health problem accelerated by the pandemic.

“The biggest impact of this research would be a shift in sudden cardiac death risk prediction from a solely substrate-based model to one that takes transient factors into account,” Dr. Adabag said. “When doctors evaluate a patient to see if they’re at a high risk of sudden cardiac death, they assess whether the patient has heart disease, has had a heart attack or has heart failure. These are all markers of abnormal substrate. But, I think the missing link is in the transient factors, like viral infections, which can exacerbate their condition and trigger an arrhythmia.”

While the spike in ICD shocks in relation to COVID-19 cases is pronounced, the research is limited by the fact that it’s unknown if patients who experienced a shock were positive with the virus or not. To better understand this, Dr. Adabag is pursuing National Institutes of Health (NIH) funding to study patients with an ICD who are confirmed COVID-19 positive. Research examining these transient factors would be a paradigm change.  

“We’re hoping to study patients with confirmed influenza, influenza-like illness or COVID-19 infection,” Dr. Adabag said. “If we have sufficient numbers, we’ll also investigate the sub-variants like Delta.”

It’s important for patients with heart disease to remain diligent in protecting themselves from COVID-19 infection because it’s likely that variants could further exacerbate heart conditions.

“Patients with an ICD or heart issues should be more cautious about preventing COVID-19 infection — so wearing masks, social distancing and vaccination are particularly important,” Dr. Adabag said. “Many people get COVID-19 infection, but the patients with heart disease or other chronic illnesses are the sickest.”

Patients with heart disease are cleared to get the COVID-19 vaccine, but on top of that, Dr. Adabag recommends getting the annual flu shot. 

“The flu vaccine has been proven to improve survival for patients with heart disease,” Dr. Adabag said. “Every year we make an extra effort to vaccinate our patients with heart disease. It’s very important.”

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