Irregularly Irregular

Over the last few months we talked about fast heartbeats, slow heartbeats, delayed heartbeats and extra heartbeats. There’s still one more arrhythmia (abnormal heart rhythm) that we need to cover, irregular heartbeats, since the FAA will also require special issuance and cardiac evaluation if you’re found to have it. 

The most common is called “atrial fibrillation” (“A-fib” or just “AF” for short) and as the name implies it’s a chaotic, irregular heart rhythm that’s generated in the atrium. Docs call it “irregularly irregular” since your pulse, heart rate, and rhythm change from moment to moment. This is different from a heart rhythm that’s “regularly irregular” like having one of those PVCs from a few months ago every few beats in a more or less steady cadence. If you have AF, the workup is going to be a little different than what we’ve covered since this rhythm is always related to a structural heart abnormality. AF has been called a “global epidemic“ as it has become increasingly common. Based on data from one of the longest running health studies, the Framingham Heart Study, the prevalence of AF has increased 3-fold over the last 50 years. There are some population variations but overall, the lifetime risk of AF is estimated to be about 1 in 3 individuals. That means that 25-30% of the population will develop AF at some point in their lives. AF is not good for you, so let’s take a look at exactly what the rhythm is, why it can be bad, where it comes from, and how it can be treated.

AF happens when the atria stop contracting in a coordinated manner and just twitch uncontrollably. Over the last 10 years cardiologists have made a huge amount of progress in understanding that AF arises from chaotic electrical signals in atrial tissue around the big veins returning blood to the left atrium from the lungs (called the “pulmonary veins”). AF starts up in atria that are susceptible to those chaotic currents because there is abnormal heart tissue in the area. There are a number of factors that make a patient more prone to A-fib, including genetics (14 different genetic markers have been identified), advanced age, male sex, sedentary lifestyle, smoking, obesity, diabetes mellitus, obstructive sleep apnea, and high blood pressure. Diseases of the valves between the upper and lower chambers can also lead to A-fib, but that’s a different mechanism. The FAA has a specific category for “non-valvular AF“ when considering a pilot for special issuance.

The fact that the top chambers of the heart are not pumping out much of anything leads to two of the major factors that make AF bad for you. Losing the pumping action of the atrium causes about a 30% loss of volume going to the big chambers and that means there’s 1/3 less blood circulating to your body with each heartbeat. As a result patients in A-fib can, and often do, have heart failure; quite literally failure of your heart to maintain adequate circulation. The other factor that’s dangerous is the blood not being pumped out of the atria just sits around and can clot. Clot in the heart can easily get ejected out and block off a major artery anywhere in the body. Whatever lies beyond the blockage and is dependent on that circulation starts to die within minutes. If it goes up to the head it’s called a “stroke” (cerebrovascular accident or CVA), and A-fib is the leading cause of strokes. Although there are also some population variations, most studies indicate that the risk of stroke is about 5 times higher in patients with AF than regular rhythm. Add that to a 3-fold increase in the risk of heart failure and it means patients with AF have twice the risk of dying than people who have a regular rhythm. The risk of clot and sluggish blood flow is why patients with AF are routinely placed on blood thinners (anticoagulation therapy) so their blood can’t clot in the heart and lead to stroke or other vascular injuries. There are different kinds of anticoagulants and all require special issuance. If your doctor chooses to use one medication called “Coumadin” (warfarin) the FAA will require a 6-week observation period and six blood tests before you can be considered for special issuance to get back to flying. Fortunately there are newer forms of anticoagulation meds that are easier to use and safer so Warfarin is not prescribed as commonly anymore.

There is also a huge volume of information on how to treat it that’s come out over the last 10 years. The two areas your doc will consider are rhythm or rate control—is it better to attempt to convert patients from AF to a normal rhythm or is it OK just to control the rate and prevent very rapid pulse? Short-term rate control is critical since patients with very fast A-fib can faint since the heart doesn’t have enough time to fill or empty, depriving the brain of adequate circulation. There are a variety of medications that are pretty effective for this and your doc will choose one that works best for you. Long term though, data suggests it’s better to try to convert patients back to regular rhythm. There are three main ways to try to convert a patient for AF back into regular rhythm (termed “cardioversion”). The first is with medication (“chemical cardioversion”), and that usually works best in patients who have only been in AF for a short time and whose atria have not been stretched out of shape. Studies show that in general the long-term success rate for chemical cardioversion for patients who have only been in AF for a few days is about 40%.

The second method is electrical; by applying defibrillator paddles, and after adequate sedation, applying a low-voltage, synchronized shock to the heart. This is always the method of choice in a patient who is acutely decompensating with AF due to rapid and inefficient cardiac function. It can also be attempted electively in patients who have only been in the rhythm for a short time and can be pretty effective, sometimes as high as 90%, over a short time frame. As with any medical intervention, there are risks with this procedure that experienced docs will take into account. The third method and most definitive treatment even for patients with long-standing AF is to cut out the area of atrium around those big veins where the abnormal signals come from. The sooner the procedure is done after it’s clear the patient is going to stay in AF the better the success rates. Long-term freedom from AF is in the range of  80-95% in properly selected patients. The technology for this procedure has advanced exponentially over recent years. It involves passing wires through an artery into the heart, mapping the electrical activity in the atrium and ablating (excising) the diseased tissue with radiofrequency or freezing it with “cryoablation” catheters. The results are spectacular and improving steadily. The other cause of AF, from leaky or narrowed valves between the upper and lower chambers (valvular AF), requires a different treatment. The valve has to be repaired or replaced before there is even a chance of curing the arrhythmia. In the operating room we often do the valve repair and tissue ablation at the same time.

The FAA will let you back in the cockpit with AF or after an ablation procedure, but you will have to jump through a lot of hoops and get an AASI (AME assisted special issuance) to do it. You will also need to provide the FAA with periodic AF status reports that are going to oblige you to make a lot of trips to your cardiologist, but you need to do that anyway. The bottom line with all of this is that AF is common but so are the complications, regular rhythm is better but rate control helps too, and the sooner it is treated the better the outcomes. Sorry to keep abusing Neil Armstrong’s quote but it still fits so well—AF is a good way to burn through all your allotted heartbeats way faster than you want. The treatments have advanced incredibly over the last few years and are very effective with low risks, certainly much less than the risks of a stroke or heart failure. So keep your heart rate slow and regular and cherish all those heartbeats you’ve been given and, as Armstrong said, “put them to good use.”

Kenneth Stahl, MD, FACS

Kenneth Stahl, MD, FACS is an expert in principles of aviation safety and has adapted those lessons to healthcare and industry for maximizing patient safety and minimizing human error. He also writes and teaches pilot and patient safety principles and error avoidance. He is triple board-certified in cardiac surgery, trauma surgery/surgical critical care and general surgery. Dr. Stahl holds an active ATP certification and a 25-year member of the AOPA with thousands of hours as pilot in command in multiple airframes. He serves on the AOPA Board of Aviation Medical Advisors and is a published author with numerous peer reviewed journal and medical textbook contributions. Dr. Stahl practices surgery and is active in writing and industry consulting. He can be reached at [email protected].

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