Anatomy Of The Heart
The heart consists of two sides, a right side that pumps deoxygenated blood from the body to the lungs and a left side that pumps oxygenated blood from the lungs to the body. Each side of the heart has two chambers, a small one called the atrium and a large one called the ventricle. When the heart contracts it happens in a coordinated fashion where the atria contract first and then the ventricles follow so the blood is pushed through the heart out into either the vascular system in the lungs or the body. One of the cardiologists I saw told me that the heart not only contracts but kind of wrings itself like a dishcloth to get the most out of every beat every second of your life. It is amazing to experience how the body develops efficiency in every aspect.
Sudden cardiac death is in general very rare, but it happens and is the cause of most deaths during sport activities. In some cases it can be due to heart attack — or myocardial infarction — caused by lifestyle diseases such as atherosclerosis, but in other cases where the person is young and otherwise healthy it is most often related to an undiscovered congenital heart condition. Typically your physician can rule out most of these by screening your family history, lifestyle and the various acute symptoms related to cardiac events such as sudden breathlessness, chest pains and incidents of fainting. In addition, it is possible to do more advanced screening using EKGs and echocardiograms if the doctor suspects something is not right or you want it for your own safety.
Congenital heart malfunctions such as the hole in Chris Legh’s heart or the bicuspid valves in Normann Stadler’s and my own heart are present from birth and, as such, not caused by endurance sports. Doing sports at a high level can in some cases make an existing condition worse or it may be dangerous to compete with certain heart conditions. This needs to be assessed by a cardiologist who has experience with athletes. In most cases guidelines developed by expert panels are available with respect to how much and what kinds of athletic activities are safe to do when you have a heart condition.
Conditions that are not present from birth and develop over time, such as various forms of arrhythmia (abnormal heart rhythms), are trickier. They may have a genetic component, but can also be influenced by stress and intense training. Arrhythmias are a general label for a condition where the heart rhythm is disturbed from its common pattern in various parts of the heart. They can be more or less dangerous depending on their speed, how long they last and which part of the heart they affect.
Ventricular tachycardia, or V-Tach, is a rare form of arrhythmia that causes one of the ventricles to contract upward of 170 beats per minute. Another arrhythmia is ventricular fibrillation in which the electrical activity of the heart becomes so disorganized that the blood simply stands still within the heart. Needless to say, V-Tach can be dangerous and may in some cases result in sudden death, if not discovered and treated as in the cases of Greg Welch and Emma Carney.
Other forms of arrhythmia, where the rhythm is disorganized in the smaller atria, are rarely as dangerous, but nevertheless clearly felt through chest discomfort, breathlessness and a reduced work capacity. These kinds of arrhythmia can last hours or even days and can most often be treated. Arrhythmias are more common in the elderly. By age 70, according to cardiologists, 15 percent of us can expect to develop some sort of arrhythmia.
When we train intensively for an endurance event such as the Ironman, several adaptations occur to our hearts. The most common is that our resting heart rate goes down due to our improved heart function. Many endurance athletes will experience the sensation of skipping a beat. Actually, this is most often due to premature beats: a premature ventricular contraction (PVC) if it originates in the ventricle or a premature atrial contraction (PAC) if it originates in the atrium. Both PACs and PVCs are quite common in well-trained athletes and often are not dangerous.