Consider for the purposes of this article that you have been having a sensation of your heart beating in your chest, but have otherwise been without any specific symptoms. Upon listening to your heart sounds, your family physician suggested you have an electrocardiogram (ECG), the very minimum test used to evaluate a possible cardiac problem. The electrocardiogram demonstrates what the physician calls premature ventricular contractions (PVCs).
Many people have PVCs and don't even know they are having them. Many times, the finding of this rhythm irregularity is totally benign, or “normal” for your particular ECG signature, but if the ECG shows two or more PVCs, the FAA will find it necessary to obtain from you a cardiovascular evaluation.
PVCs are “extra beats” that originate in the ventricles of the heart. Because they can either be benign or a sign of something more serious with your heart, the FAA wants to know which situation you fall into.
The cardiovascular evaluation will include a thorough personal and family medical history and a thorough cardiac and general physical examination. Most importantly, they will want you to have a stress test. A stress test is a procedure where a technician places electrode patches on your chest, hooks you up to a heart monitoring device, and has you walk on a treadmill. The treadmill is gradually increased in speed and elevation until your heart rate reaches a certain level. This level is called your maximal heart rate. You can calculate your own maximal rate by subtracting your age from 220. The FAA wants you to achieve a heart rate as close to 100 percent of your maximal rate as you can get, but at the very least, 85 percent of the maximum predicted rate. You will also need to exercise for as close to nine minutes as possible. This time demonstrates what the FAA considers good exercise tolerance and is a component of a “normal” stress test.
The combination of exercise tolerance and achieving predicted heart rate evaluates the quality of blood supply through the coronary arteries to the heart muscle. PVCs can be a sign that an area of your heart is not getting enough blood supply and thus there is a set up for what is called an “irritable focus.”
The exercise stress test is often referred to as the Bruce Protocol exercise stress test, after Dr. Robert A. Bruce, who devised the test years ago. Bruce developed the multistage test, consisting of several stages of progressively greater workloads. It was this multistage test, a description of which was first published in 1963, that became known as the Bruce Protocol. Bruce and colleagues demonstrated that exercise testing was useful in screening apparently healthy people for early signs of coronary artery disease. This test is not infallible. Some people who have this test have results that are interpreted as negative or normal, but in fact, have a “positive” finding of disease that compromises blood supply to the heart (termed a “false negative”). Conversely, other patients who test have a “positive” result, suggesting lack of blood supply, but when studied with more specific testing, the result is actually negative (called "false positive").
A more sensitive test can be performed in both cases. This type test is called a radionuclide stress test or nuclear stress test. In this test the technician inserts an intravenous catheter and prior to exercise injects a small amount of radioactive substance. The person lies under a scanner and images of the heart at rest are taken. The person is then exercised on the treadmill and about one minute before the person cannot go any longer, another injection of the same substance is done and the heart is scanned again. This radioactive substance will avoid areas of the heart where there is prior damage or where there is reduced blood flow. The physician who interprets the test will compare the rest pictures with the post exercise images.
In the case of the airman with PVCs, if the PVCs are reduced in frequency or disappear completely with exercise and the stress test does not demonstrate any lack of blood supply (the medical term for this is ischemia), the PVCs are considered to be benign and the airman will not require any more testing. However, if there is ischemia on the stress test, then the airman will be required to have more testing to better identify what is occurring.
The FAA will accept the plain stress test evaluation of pilots applying for third class certification as long as the test does not demonstrate lack of blood supply. For first and second class certificates, the airman will need to have the nuclear exercise stress test performed.