New research indicates that exposure to extreme heat can significantly increase the likelihood of irregular heart rhythms in individuals with implanted defibrillators. Outdoor temperatures reaching or surpassing 100 degrees Fahrenheit were found to nearly triple the occurrence of atrial fibrillation (AFib) episodes among patients who have electronic devices implanted in their chests designed to monitor and stabilize heart rhythms. This study is set to be presented on November 18 at the American Heart Association’s Scientific Sessions in Chicago and is considered preliminary until it undergoes publication in a peer-reviewed journal.
According to the lead researcher of the study, Dr. Barrak Alahmad, who is a research fellow in environmental health at Harvard T.H. Chan School of Public Health, the incidence of AFib is rising alarmingly both in the United States and worldwide. Co-investigator Dr. Theofanie Mela, a cardiac electrophysiologist at Massachusetts General Hospital, highlighted that gaining a better understanding of the physiological mechanisms behind their findings could aid in the prevention of conditions that trigger AFib, thereby lessening the burden of arrhythmias. Until more information is available, Mela advises patients to avoid extreme temperatures and utilize air conditioning to mitigate the severe stress caused by excessive heat.
Estimates suggest that by 2030, over 12 million individuals could be living with AFib, according to statistics from the American Heart Association (AHA). While risk factors such as heart disease and other health conditions are known to increase the likelihood of developing AFib, the impact of heat-induced stress on this condition remains underexplored. In the recent study, researchers evaluated health records from 2,313 adults across more than 100 U.S. cities who had been implanted with an implantable cardioverter defibrillator (ICD) or a cardiac resynchronization therapy defibrillator (CRT-D) between 2016 and 2023. The average age of participants at the time of device implantation was 71, and the majority were men suffering from cardiomyopathy, a condition that hampers the heart’s ability to pump blood effectively.
The study matched the date of each patient’s first recorded AFib episode to local weather data from the regions where the patients lived. Findings revealed that temperatures between 41 and 46.4 degrees Fahrenheit were associated with the lowest likelihood of AFib episodes. Conversely, when temperatures exceeded 102 degrees Fahrenheit, the odds of experiencing an AFib incident significantly increased. Specifically, at 102.2 degrees, the likelihood was 2.66 times higher; at 104 degrees, it rose to 2.87 times higher, while temperatures of 105.8 degrees led to more than a threefold increase in odds.
Analysis also showed that AFib episodes were less frequent between midnight and 7 a.m. compared to standard working hours, and the frequency was notably higher on weekdays relative to weekends. Dr. Sanjay Rajagopalan remarked that this might be the first study to associate ICD-detected AFib occurrences with temperature fluctuations. As the chair of the AHA’s 2024 policy statement regarding the establishment of heart-healthy environments, he pointed out that heat stress is linked to heightened risks of stroke, heart attack, and cardiovascular mortality. Rajagopalan noted that with increasing age and obesity rates contributing to the growing prevalence of AFib, rising temperatures could add another layer of concern.
He cautioned that those particularly vulnerable in regions at risk of extreme heat should take these findings seriously and adopt measures to remain cool and well-hydrated. Unfortunately, he mentioned that individuals from lower socioeconomic backgrounds may be at heightened risk due to limited access to air conditioning and other resources to cope with high temperatures. Thus, the findings underscore the critical need for public health measures to assist at-risk populations during extreme heat events.