A Primer on Atrial Fibrillation
By Alan Bragman, D. C.
It was a warm picture perfect day in early October and a group of us were going to do hill intervals on Pebblebrook Road. This road has about 350-400 feet of steady elevation gain over 2 miles, and is about 10 miles from my home. As I rode to meet the other riders I was having trouble catching my breath and attributed this to mild seasonal allergies and the fact that I had not used my inhaler prior to the ride. As we headed over to do the hill workout at a moderate pace, I was having difficulty keeping up with the group and was feeling lousy. I realized that any type of intense workout would not be possible due to the way I was feeling, and I told the other riders to go ahead while I rode home at a leisurely pace. I seemed to be alright spinning home at an easy pace, when I began experiencing tremendous pressure and pain in my chest with palpitations and difficulty breathing. I took a drink, tried to calm down, and then I began having difficulty staying upright on the bike. I got off the bike and laid down on someone’s lawn, certain this was “The Big One”.
Fortunately, as I was losing consciousness a runner and a neighbor came out to assist me, and they immediately called an ambulance. The neighbor that came out to assist happened to be a doctor and he ran to his house to get me some aspirin. Luckily for me Piedmont Hospital was only a few miles away and the ambulance was there before the doctor returned with the aspirin. They took me to the ER, got an IV started and hooked me up to a cardiac monitor. As soon as I saw the EKG I noticed with relief the P wave was missing and realized it was atrial fibrillation and not a myocardial infarction. The P wave on an EKG represents the depolarization or contraction of the atrium. It took a full day for my heart to return to a normal sinus rhythm and I spent two days in the hospital, where they put me through extensive cardiac testing. The conclusion was I had a lone episode of atrial fibrillation without clinical or electrocardiographic findings of other cardiovascular disease, related pulmonary disease, or cardiac abnormalities.
They did tell me I had a typical athletes heart with cardiomegaly (an enlarged heart), bradycardia (low resting pulse rate) and hypotension (low blood pressure), which I was well aware of. The cardiologist told me to take 325 mg of aspirin/day, cut down on caffeine and other stimulants and that I could continue to exercise as before, but to avoid interval training for a few weeks. After my discharge from the hospital I reduced my training intensity and distance, but still had two short episodes of atrial fibrillation and flutter about three weeks later. During the winter I did a lot of moderate intensity base and strength training without incident for several months.
Then in early March while on a long, hilly training ride in cold and windy conditions I began to experience atrial fibrillation and flutter again, so I turned around and rode home easily. The following week while riding, I had episodes of atrial fibrillation and flutter every time I rode up a sizable hill. The situation was getting out of control and my internist referred me to a cardiac electro physiologist. This is a cardiologist that specializes in diagnosing and treating electrical activity abnormalities affecting the heart. After a comprehensive discussion and examination, including an EKG, he placed me a minimal dose of Metoprolol, a beta blocker. It has been almost two months on the Beta blocker with periods of intense training and thus far the medication has prevented additional episodes of atrial fibrillation or flutter. The true test of this medications effectiveness will come when I go riding in the North Georgia Mountains, with thousands of feet of elevation gain and long steady climbs.
Being a doctor and a serious endurance athlete I was very familiar with atrial fibrillation, however this incident took me totally by surprise. I am 58 years old and have been a healthy competitive and fitness cyclist since I was a teenager. After personally experiencing this problem, I have been contacted by numerous fellow athletes and acquaintances suffering with this disorder. It amazes me how many endurance athletes have issues with cardiac conduction disorders.
Atrial fibrillation is the most common cardiac arrhythmia and it involves the two upper chambers of the heart, the right and left atrium. Arrhythmia is defined as a condition caused by abnormal electrical activity in which the heart beat is too fast, slow or irregular. Atrial flutter is similar to fibrillation and consists of an abnormal heart rhythm (arrhythmia) occurring in the atria of the heart, and it is associated with an increased heart rate. The right atrium receives deoxygenated blood from the inferior and superior Vena Cava and sends it to the right ventricle, which sends it to the lungs for oxygenation. Oxygenated blood from the lungs is sent to the left atrium by the Pulmonary veins to the left ventricle where it is sent through the aorta to the body.
The Pulmonary veins are unique, because they are the only veins in the body that carry oxygenated blood. During atrial fibrillation normal electrical impulses generated by the sinoatrial node are overwhelmed by disorganized impulses originating from the pulmonary vein and atria. This results in the heart muscles of the atria contracting in a highly irregular fashion and this causes an erratic disorganized heartbeat which greatly reduces blood flow and oxygen to the body. An episode of atrial fibrillation can last from minutes to weeks and in some cases it can become permanent. Atrial fibrillation itself is generally not life-threatening; however it greatly increases the risk of stroke due to blood pooling and clots forming in the poorly contracting atria. The signs and symptoms of atrial fibrillation include; elevated heart rate (tachycardia) palpitations, chest pain, shortness of breath, dizziness, light headedness, and syncope (loss of consciousness)
The incidence of atrial fibrillation is 2-10 times higher in athletes participating in extreme endurance sports, and this increases as they age. The possible mechanisms explaining this association remains speculative, however, some possible explanations include increased atrial size, bradycardia (low pulse rate), inflammatory changes and ectopic beats (small variations in the normal heartbeat causing an irregular pulse).
The treatment for endurance athletes experiencing atrial fibrillation and flutter without underlying pathology, consists of preventing circulatory instability and stroke. For preventing and lowering stroke risk aspirin is initially used for anticoagulation. Other medications used for anticoagulation in patients with a higher stroke risk includes Warfarin (Coumadin) and Heparin. Preventing circulatory instability is achieved by rate and rhythm control of the heart utilizing several possible methods. The most common method to control cardiac arrhythmia is with various medications such as Beta-Blockers, calcium channel blockers, Digoxin and Dofetilide. Cardioversion is a noninvasive method of converting an irregular heartbeat to a normal sinus rhythm through the use of electrical shock or medications. If control of atrial fibrillation cannot be maintained by medication or cardioversion, pulmonary vein Ablation may be attempted. Pulmonary vein ablation is an invasive technique that attempts to block abnormal electrical signals which normally begin at the pulmonary veins at their attachment to the left atrium. This is done by inserting a catheter that is guided through vessels into the atrium where energy is applied to block impulses which scars the targeted areas of the pulmonary veins. Hopefully, this procedure will block or electrically disconnect abnormal electrical impulses which disturb the normal sinus rhythm.
As my father who is now 87 always tells me, “getting old is not for the timid”, unfortunately he’s right!
About the Author
Alan Bragman is a chiropractor living in Atlanta, Georgia. He is a former Cat 3 cyclist and nationally ranked inline speed skater. He was on the medical advisory board at Bicycling magazine for 10 years and has written for other sports publications.
In addition to the articles mentioned above, Dr. Bragman’s RBR eArticles include: