Atrial fibrillation is caused by an abnormality in the heart’s electrical conduction system. It’s common — around 9 percent of people 65 and over have it. To understand A fib, as it’s often called, it’s important to understand heart basics.
The heart is a specialized muscle that is made up of two smaller, upper chambers — the right and left atrium — and two larger, lower chambers — the right and left ventricle. Blood that has released oxygen to muscles, tissues and organs throughout the body returns through veins to the right atrium, which pumps it into the right ventricle, which then pumps it through the lungs, where it gets rid of carbon dioxide waste and takes on oxygen. Blood then enters the left atrium, which pumps it into the left ventricle, which then pumps it out through miles and miles of arteries. Each time the heart pumps, valves prevent backflow.
In an average person the heart beats approximately 4,800 times an hour, 115,200 times a day, over 42 million times a year, and over 3 billion times over an 80-year lifespan. All these heartbeats are driven by the heart’s built-in electrical system with its own pacemaker. The sinoatrial (S-A) note, located in the right atrium, serves as the heart’s pacemaker, which every second or so initiates an impulse that spreads across the two atria, causing them to contract, then passes to the ventricles, causing them to contract.
A fib is caused by an abnormality (“short circuit”) in the electrical conduction system, resulting in weak, irregular, chaotic contractions of the atria (like a fish out of water), instead of regular, rhythmic, strong beats. The lack of normal blood flow through the atria can lead to sludging and clots —which can go to the brain and cause strokes. The ventricles in A fib beat irregularly and often rapidly, and if this goes on for a long time, the heart muscle is damaged and heart failure results.
Some of the common risk factors for developing A fib are: overactive thyroid; atherosclerosis of the coronary (heart) arteries; sleep apnea; valvular heart disease (such as that caused by rheumatic fever); high blood pressure; pericarditis; chest trauma; thoracic or cardiac surgery; pulmonary disease such as pneumonia or pulmonary embolism; certain medications; acute alcohol excess; and alcohol withdrawal. There is also evidence that overexercise, such as training for and competing in ultramarathons, repeated marathons or full triathlons, can cause scarring of the electrical conduction system, causing A fib and other cardiac arrhythmias (read “The Haywire Heart”).
Symptoms from A fib include racing heart, palpitations, weakness, light-headedness, fainting, shortness of breath and chest pain. Some people have no symptoms. A fib can last from minutes to weeks. It can be just a one-time event, be intermittent or be permanent. If you are experiencing any of the aforementioned symptoms, check your pulse by gently placing the tips of your index and middle fingers on your radial artery, on the thumb side of the under-surface of your wrist, about 2 inches back from your palm. You can also check your pulse by placing the same two fingers on the carotid artery on either side of your trachea (windpipe). Count the number of beats for 15 seconds and multiply by four to get the number of beats per minute. Normal rate is 60 to around 75 (well-conditioned athletes often have pulse rates less than 60).
If your pulse is over 100, or if it’s irregular, you should see your primary care doctor as soon as possible to see if you have A fib. If an EKG confirms A fib, your doctor may want to put you on an anticoagulant for stroke prevention. If your ventricular rate is extremely rapid, you might need medication to slow it down to prevent heart failure.
A fib sometimes goes away on its own. If it doesn’t, one option is cardioversion, where a cardiologist applies a brief electrical current to your heart to get it back in a regular rhythm. In some cases, medications to maintain a normal rhythm are indicated. Another option that became available several years ago is ablation, where an electrophysiologist (cardiologist who specializes in the electrical conduction system of the heart) cauterizes the abnormal circuitry in the heart that is causing the A fib. Fortunately, well-trained cardiologists and an electrophysiologist are available at Valley View Hospital.
Greg Feinsinger, M.D., is a retired family physician with a special interest in heart disease and diabetes prevention and reversal, ideally through lifestyle changes. He’s available for free, one-hour consultations — call 970-379-5718.