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:

  • dizziness
  • shortness of breath
  • anxiety
  • fatigue when exercising
  • disproportionate sweating
  • faintness
  • confusion
  • 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.

Arrhythmia Alert

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.*

Heart Diagram

Figure 1. Blood Flow Through the Heart: Oxygen-Poor to Oxygen-Rich Blood

Oxygen-poor blood enters the right atrium via the inferior and superior venae cavae. Pressure from incoming blood forces the tricuspid valve to open, allowing 70% of the blood to flow into the right ventricle. The right atrium then contracts, filling the right ventricle to capacity. The right ventricle then contracts, pumping blood through the pulmonary arteries to be oxygenated in the lungs. The pulmonary veins return the oxygen-rich blood to the left atrium. Blood is sent to the left ventricle passively (70%) and by contraction (30%) through the mitral valve into the left ventricle. The left ventricle powerfully contracts, thrusting oxygen-rich blood through the aorta and throughout the entire body for all life-sustaining needs.

Five Heart Arrhythmia Question and Answers

1. What are PACs and PVCs?

Premature atrial contractions (PACs) and premature ventricular contractions (PVCs) are early beats that originate in the atria (PAC) or ventricles (PVC) of the heart. They briefly disrupt the heart’s autorhythmic beating. It feels like your heart “skips a beat.” Most people have them at some time in their lives, and they are somewhat common and normal in children and teenagers (AHA 2012b). If they become more regular, consult a health professional to determine a cause.

2. What is long QT syndrome?

Long QT syndrome is a defect in which the heart’s electrical cells take longer than normal to recover after each heartbeat. Long QT syndrome can be inherited or can be acquired after taking certain medications (or certain combinations of medications). People with long QT syndrome may be susceptible to ventricular fibrillation (rapid, chaotic quivering of the ventricles). During ventricular fibrillation, the blood pressure falls to zero and the person loses consciousness. An immediate, life-saving shock (defibrillation) must be delivered to the heart to restore a normal rhythm.

3. What is a heart block?

A heart block happens if the electrical impulses from the atria are not properly transmitted to the lower ventricular chambers. Different types of heart blocks may require different treatments, depending on exactly which part of the heart’s electrical-conduction system is faulty. Other symptoms–such as fatigue, lightheadedness or fainting–may develop. In some cases, implanting a permanent pacemaker (a device that artifically stimulates the heart muscle and regulates its contractions) is the primary treatment.

4. What is sick sinus syndrome?

Sick sinus syndrome is a cluster of symptoms that indicate the heart’s natural pacemaker, the SA node, is not functioning properly. The heart rate can switch back and forth between a slow (bradycardia) to fast (tachycardia) heartbeat. The condition may not be diagnosed until it has advanced, usually with age. A permanent pacemaker, sometimes in combination with medication, is the primary treatment.

5. What is sinus bradycardia, and when is it dangerous?

Any heart rate slower than 60 beats per minute is referred to as a sinus bradycardia. Many people, especially exercise enthusiasts and athletes, have a naturally developed sinus bradycardia as a result of their very efficient cardiovascular systems. However, if sinus bradycardia is accompanied by unusual fatigue, shortness of breath, decreased exercise tolerance, and episodes of nearly passing out, it may be necessary to implant a pacemaker.

How Do Heart Attack Symptoms Differ From Atrial Fibrillation Symptoms?

The “thumping” and “quivering” that occur with AFIB are the key difference between this condition and a heart attack. A heart attack is a blockage of blood flow to the heart, often caused by a clot or buildup of plaque in one of the heart’s coronary arteries, which deliver blood to the heart muscle. A heart attack can damage or destroy some part of the heart muscle and may be sudden and intense.

Exercise Professionals Should Always Be Alert to the Symptoms of a Heart Attack

Learn to recognize the following:

  • chest discomfort: uncomfortable pressure, squeezing, fullness or pain
  • discomfort in other areas of the body, such as the arms, back, neck, jaw or stomach
  • shortness of breath with or without chest discomfort
  • cold sweat, nausea or lightheadedness (AHA 2012a)

Fast action can save lives. Don’t wait more than 5 minutes to call 911 or your emergency response number.


AHA (American Heart Association). 2013. Atrial fibrillation (AF or AFib).; accessed Aug. 25, 2013.
AHA. 2012a. Warning signs of a heart attack.; accessed Aug. 25, 2013.
AHA. 2012b. Premature contractions.; accessed Aug. 25, 2013.

Len Kravitz, PhD

Len Kravitz, PhD is a professor and program coordinator of exercise science at the University of New Mexico where he recently received the Presidential Award of Distinction and the Outstanding Teacher of the Year award. In addition to being a 2016 inductee into the National Fitness Hall of Fame, Dr. Kravitz was awarded the Fitness Educator of the Year by the American Council on Exercise. Just recently, ACSM honored him with writing the 'Paper of the Year' for the ACSM Health and Fitness Journal.

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