The heart does remarkable work. Roughly the size of a human fist, the heart pumps blood every second of every day, delivering nutrients and oxygen to organs and tissues, and sending waste to filters in the kidneys, liver and lungs.
Yet not every heart works well. A healthy heart relies on a self-generating electrical signaling system to keep it pumping at the right pace; heart maladies that disrupt the signals can dramatically impact a client’s health. Collectively, we call these maladies heart arrhythmias. Being able to understand and recognize the symptoms of key heart arrhythmias is essential for exercise professionals working with a broad range of healthy and unhealthy clients.
The SA Node: Where Heartbeats Come From
The beats of the heart are autorhythmic. That means the heart produces pulses through electrochemical stimuli originating within the heart, specifically from the sinoatrial node (or SA node), a small group of cells in the wall of the heart’s right atrium.
The SA node is often called the heart’s pacemaker because it controls heart rate in healthy people. In a healthy heart, specialized autorhythmic cells in the SA node send electrical signals at a constant pace along specific pathways in the heart muscle; these impulses trigger contractile cells in the heart, causing it to pump blood throughout the body (see Figure 1).
What Are Arrhythmias, and Why Are They Potentially Dangerous?
As noted earlier, the SA node is the heart’s primary pacemaker, as it excites autorhythmic cells at the fastest rate. With arrhythmias (or dysrhythmias as they’re sometimes called), the SA node may
- fail to generate electrical impulses at its normal rate;
- stop functioning entirely; or
- malfunction because of some other heart abnormality
When the SA node malfunctions, autorhythmic cells in other parts of the heart take over the role of pacemaker. The result is an arrhythmia, or an irregular signal pathway in the heart. Some arrhythmias occur just briefly, and the SA node quickly reestablishes its pacemaker role. Other arrhythmias, depending on their origin in the heart or how long they last, may dramatically impair the flow of blood through the heart and to the body.
Atrial, or Supraventricular, Arrhythmia
Atrial (or supraventricular; meaning above the ventricles) arrhythmias are fast heart rate rhythms that originate in the atria. With these arrhythmias, electrical signals in the heart’s upper chambers, the atria, fire abnormally, interfering with electrical signals coming from the SA node. These rapid heartbeats do not allow enough time for the heart’s ventricles to fill appropriately with blood (see Figure 1) before they contract; as a result, blood flow to the rest of the body is compromised.
Personal trainers should note that some clients put themselves at risk of atrial arrhythmia if they drink large amounts of coffee or alcohol, suffer high anxiety or take in nicotine from tobacco. Atrial arrhythmia symptoms include dizziness, lightheadedness, rapid pulse, shortness of breath and sometimes some chest pain. Under medical supervision, a combination of cutting coffee and alcohol intake, giving up tobacco and getting proper rest can be an effective treatment.
Atrial Fibrillation: The Most Common Arrhythmia
Perhaps the most well-known and most common heart arrhythmia is atrial fibrillation, or AFIB, which affects 2.7 million Americans (AHA 2013). This is one of the supraventricular arrhythmias. In AFIB, the atria quiver in a very rapid, irregular pattern. The heartbeat (determined by the lower, ventricular pumping chambers) often becomes irregular and rapid. AFIB can lead to health problems, including excessive fatigue, congestive heart failure or stroke. According to the American Heart Association, people with AFIB are five times more likely to have a stroke than people with a normal heart rhythm, and AFIB-related strokes are more deadly then non-AFIB-related strokes.
Personal trainers should note that a common symptom of AFIB is a sudden, fast (>100 beats per minute) or irregular resting heart rate. While some people with AFIB show no symptoms, any of these symptoms are usual:
- shortness of breath
- fatigue when exercising
- disproportionate sweating
- chest pressure/pain
- “thumping” or “palpitations” in the chest
The three main types of AFIB are paroxysmal fibrillation, persistent AFIB and permanent AFIB (AHA 2013). In paroxysmal fibrillation, a person may have brief episodes during the course of a year when the atria quiver for a matter of minutes and then the heart returns to a normal rhythm on its own. These symptoms are very unpredictable, but eventually they can turn into a permanent form of atrial fibrillation (AHA).
Persistent AFIB is an irregular rhythm that lasts longer than 48 hours and will not return to a normal rhythm on its own, thus requiring medical treatment. Permanent AFIB occurs when the condition lasts indefinitely and can no longer be managed with medications.
If a client mentions any of the symptoms discussed above or suspects she has a heart rhythm problem, encourage her to see a medical professional immediately. Medical specialists have a number of effective ways to manage arrhythmias, especially if treated early. As personal trainers work more with the aging population, where arrhythmias are more common, being able to recognize the symptoms of common arrhythmias may help prevent a life-threatening situation.*