AHA 2024: High Temperatures Linked to Irregular Heartbeat in Individuals With Implanted Defibrillators

Exposure to temperatures of 100° Fahrenheit or higher could double or triple the risk of irregular heart rhythm for individuals with implanted defibrillators, according to new research to be presented at the American Heart Association (AHA) 2024 Scientific Sessions.¹

In addition to increasing the risk of heat exhaustion and heat stroke, high heat also stresses the cardiovascular system, forcing the heart to work harder. This heightens the risk for heart attacks, heart arrhythmias, and heart failure. This is a growing concern as many part of the US are facing historic heat waves and unseasonally warm weather.²

Thermometer showing hot weather | Image credit: © vladischern | stock.adobe.com

According to the National Oceanic and Atmospheric Administration, the global temperature has risen by an average of 0.11° Fahrenheit per decade since 1850, or about 2 degrees in total. However, the rate of warming since 1982 is more than 3 times as fast, at 0.36° per decade. Additionally, 2023 was the warmest year on record since global records began in 1850.³

In findings from one study in Kuwait, where daytime temperatures can reach triple digits during the hotter months, investigators identified associations between rising temperatures and the risk of cardiovascular deaths. Most of these deaths occurred between 95° and 109° Fahrenheit.²

“[Atrial fibrillation] is becoming more prevalent both in the US and globally, with its incidence rising at an alarming rate,” Barrak Alahmad, MD, PhD, MPH, author of the new study being presented at AHA, said in a news release.¹

Experts estimate that more than 12 million individuals will be living with atrial fibrillation by 2030. Although it is known that heart disease and other medical conditions increase the risk of developing atrial fibrillation, the role of heat-induced stress is understudied.¹

In the study, investigators examined health data from more than 2000 adults in the US with an implanted cardioverter-defibrillator (ICD) or cardiac resynchronization therapy defibrillator (CRT-D) device implanted between 2016 and 2023. These devices are inserted into a patient’s chest to monitor and regulate the heartbeat.¹

For each patient, the first episode of atrial fibrillation detected by the device was matched to hourly outdoor temperature data on the day of the episode for the location of the hospital where they received the device. Investigators then categorized the atrial fibrillation episodes for each study participant by the time of day and day of the week, with corresponding outdoor temperatures. The relationship between outdoor heat and episodes of atrial fibrillation was determined for the entire study population.¹

According to the study findings outdoor temperatures between 41° and 46.4° Fahrenheit had the lowest odds of causing an episode of atrial fibrillation, whereas odds were significantly higher for hotter temperatures. Specifically, temperatures of 102.2°, 104°, and 105.8° Fahrenheit had odds 2.66 times, 2.87 times, and 3.09 times higher, respectively.¹

Additionally, fewer atrial fibrillation episodes occurred in the early morning hours between 12 AM and 7 AM, compared with standard working hours (8 AM to 5 PM). Episodes were also more common on weekdays than weekends, and an analysis evaluating episodes that lasted longer than 30 minutes found similar results.¹

“We need to understand the physiological processes underlying these findings and concentrate on preventing conditions that trigger [atrial fibrillation] to minimize the burden of arrhythmias,” Theofanie Mela, MD, a cardiac electrophysiologist at Massachusetts General Hospital in Boston, said in the news release. “In the meantime, we recommend patients avoid extreme temperatures and use air conditioners so that they do not expose their bodies to the severe stress of extremely high heat.”¹

Pharmacists can play a key role in advising patients about how to stay safe in hot weather. Small steps such as drinking plenty of water; lowering consumption of alcohol; wearing loose, light-colored clothing; and reducing strenuous activity can make a significant difference. Pharmacists should also identify patients who may be more at risk during extreme heat events, including those with implanted defibrillators.⁴

“Susceptible individuals living in areas at risk for markedly increased temperatures should take note of these findings and ensure that they take appropriate precautions to stay cool and hydrated,” Sanjay Rajagopalan, MD, MBA, FAHA, chief of cardiovascular medicine at University Hospitals Harrington Heart and Vascular Institute in Cleveland, said in the news release. “Unfortunately, the most vulnerable people may be those in lower socioeconomic groups who may not have access to air conditioning and other means of sheltering during warm days.”¹

Importantly, the authors noted that the study cannot draw definitive conclusions for several reasons, including the fact that local weather stations measured temperatures where the patients received their ICDs, although this may not be the same as where they lived. As a result, it is impossible to ascertain whether the participants were exposed to the high temperatures recorded by the local weather stations.¹

REFERENCES

1. 100°F temps may be linked to irregular heartbeat in those with implanted defibrillators. News release. American Heart Association. November 11, 2024. Accessed November 14, 2024. https://newsroom.heart.org/news/1000-f-temps-may-be-linked-to-irregular-heartbeat-in-those-with-implanted-defibrillators?preview=070d&preview_mode=True

2. Solan M. Heart problems and the heat: What to know and do. Harvard Health Publishing. June 21, 2022. Accessed November 14, 2024. https://www.health.harvard.edu/blog/heart-problems-and-the-heat-what-to-know-and-do-202206212765

3. Lindsey R, Dahlman L. Climate Change: Global Temperature. National Oceanic and Atmospheric Administration. January 18, 2024. Accessed November 14, 2024. https://www.climate.gov/news-features/understanding-climate/climate-change-global-temperature

4. Extreme heat and human health: for pharmacists and pharmacist technicians. Government of Canada. 2024. Accessed November 14, 2024. https://www.canada.ca/en/health-canada/services/publications/healthy-living/extreme-heat-human-health-pharmacists-technicians.html