By Ellie Himyak, PA-S

Atrial fibrillation is the most commonly diagnosed chronic heart arrhythmia in the United States, with prevalence rising due to an aging population¹ . It is characterized by an abnormality in the electrical activity in the top chambers of the heart, or atria, causing the heart muscle to “fibrillate” instead of producing an effective contraction. This uncoordinated electrical activity can lead to very fast atrial heart rates up to 300-500 beats per minute 1 . Due to the lack of effective atrial contraction, the ventricular response is subsequently irregularly irregular and can be rapid in rate as well. Atrial fibrillation is classified based on persistence² :

• Paroxysmal: abnormal rhythm terminates spontaneously or with intervention within 7days of onset
• Persistent: Abnormal rhythm is sustained for 7 days or more
• Long-standing persistent: Abnormal rhythm is continuous for 12 months or more with a rhythm-control strategy pursued
• Permanent: Abnormal rhythm is continuous and the decision has been made by both patient and provider to stop attempts to restore a normal rhythm

Patients with atrial fibrillation experience a wide variety of symptoms. Some people may be completely asymptomatic to the arrhythmia, while others may experience an array of symptoms including fatigue, palpitations, shortness of breath, dizziness, loss of consciousness, and heart failure symptoms. Timely diagnosis of atrial fibrillation is important to mitigate the complications associated with the arrhythmia. One of the main complications that need to be addressed is the increased risk of stroke . Due to the discoordination of atrial electrical activity, blood is not effectively pumped through the heart. Stagnation of blood results in an increased risk of blood clot formation. These can then travel to the brain and cause a stroke. Given this risk, those who are diagnosed with atrial fibrillation are commonly started on anticoagulation (blood thinning) medication to reduce the risk of clot formation. Uncontrolled atrial fibrillation can also increase the risk of heart failure. This is especially common when the arrhythmia is associated with a rapid ventricular heart rate.

There are many etiologies of atrial fibrillation with a mixture of genetic, environmental and metabolic components. Family history, genetic predisposition, and advanced age increase the risk of developing atrial fibrillation, however there are several other environmental and metabolic factors that can contribute to the development of this arrhythmia. Underlying cardiac/structural abnormalities including history of heart failure, coronary artery disease, valvular heart disease, and congenital heart disease can increase the risk of atrial fibrillation. Additional risk factors include hypertension, sleep apnea, obesity, diabetes mellitus, excessive alcohol use, and smoking.

This blog post aims to reflect upon the impact of high altitude on cardiac arrhythmias like atrial fibrillation. Unfortunately, there is very limited data on the direct relationship between atrial fibrillation and residence at high altitude. Current data suggest that high altitude environments do not directly cause atrial fibrillation, but there is evidence that the hypoxicenvironment of high-altitude areas can create strain on the heart and exacerbate underlying heart conditions³. Those who have been previously diagnosed with heart conditions, including atrial fibrillation, should be aware of the effects of traveling to high altitude, especially if they plan to participate in heavy exertion⁴.

To gain some perspective on this topic, Jim Brooks, a member of the Summit County community in Colorado, contributed a personal account of his experience with living with atrial fibrillation at high altitude. Jim moved to Colorado at the age of 56 and was diagnosed with atrial fibrillation 9 years later. Jim explained that he was initially diagnosed while on a trip to Denver, when he noticed something felt “different” in his heart. He presented to the emergency department and was found to be in an abnormal rhythm called “atrial flutter” which is an abnormal heart rhythm with a similar underlying pathophysiological mechanism to atrial fibrillation. The two abnormal rhythms commonly interconvert. Jim was later diagnosed with atrial fibrillation as well.

Following his diagnosis, Jim underwent thorough cardiac evaluation to evaluate the classification of his arrhythmia and to ensure he had maintained stable heart function. Included in this workup was a sleep study which revealed that Jim had been living with severe uncontrolled sleep apnea. Sleep apnea is a very common risk factor for atrial fibrillation. Apneic events are events during the night in which a person’s breathing pauses, which creates hypoxia and ultimately increases strain on the heart. There is evidence that living at altitude increases the risk of developing sleep apnea with an estimated 1.5-fold increase in risk per 1,000m of elevation gain⁵. For those who have a diagnosis of sleep apnea, traveling or moving to higher elevation can exacerbate this issue and require adjustments to treatment.

Jim is doing quite well and states that he does not feel limited by his atrial fibrillation. Jim’s sleep apnea is treated with nocturnal supplemental oxygen, and his atrial fibrillation is controlled with medication. Jim continues to be able to engage in all the activities he enjoys doing including hiking and skiing. When asked what advice he received from his cardiologists regarding living with this heart arrhythmia at altitude, Jim highlighted the importance of hydration. He was told that as we age, especially men, can have a decrease in their sense of thirst, so he is very mindful about pre-emptively hydrating, especially if he plans to engage in activities requiring exertion.

Jim also prioritizes a healthy diet and prefers to avoid alcohol and caffeine as these are known potential triggers to atrial fibrillation.
Upon his closing remarks, Jim highlighted the importance of health monitoring for populations living at altitude, especially oxygen monitoring. He believes that everyone over the age of 50 living at altitude should at the very least own a pulse oximeter to evaluate for low oxygen readings, and importantly, that there is technology available today which can monitor for fluctuations in oxygen levels overnight which may prompt a conversation with a medical provider to pursue formal testing to evaluate for sleep apnea. Jim is grateful for the care he has received here in Summit County. He expressed his support and excitement for on-going high altitude research.

References

1. Baman JR, Passman RS. Atrial Fibrillation. JAMA. 2021;325(21):2218 ↩︎
2. Joglar JA, Chung MK, et al. 2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation: A report of the American College of Cardiology/American Heart Association Joint Committee on Clinicacl Practice Guidelines. J Am Coll Cardiol. 2024;83(1):109-279 ↩︎
3. South Denver Cardiology. Does High Altitude Trigger ATrial Fibrillation (A-fib)? South Denver Cardiology August 6, 2024. Accessed September 29, 2026 ↩︎
4. Cornwell WK, Baggish AL, Bhatta YKD, et al. Clinical implications for exercise at altitude among individuals with cardiovascular disease. J Am Heart Assoc. 2021;10(19):e023225 ↩︎
5. Huang, Y., Jia D., Jiang, Q. et al. Exercise capacity of patients with obstructive sleep apnea at moderate to high altitude. Sleep Breath. 30, 281(2026) ↩︎

Ellie Himyak is currently a Physician Assistant student matriculating this year at Red Rocks Community College. Born and raised in Colorado a 4^th generation Colorado native, she earned a Bachelor of Arts degree from the University of Colorado, Boulder in Integrative Physiology in 2020. She later went on to work as a medical assistant and medical scribe in a cardiology office to earn patient care hours before pursuing PA School. Throughout her clinical year, Ellie has had the opportunity to work clinical rotations in several rural communities across Colorado, and she has enjoyed experiencing all that Colorado has to offer, including its beautiful scenery and numerous hiking trails.