|Heart Arrhythmias: An Exercise Professional's Primer
Len Kravitz, Ph.D.
The heart, a muscle about the size of a clenched fist, is responsible for pumping blood throughout the body, every second of every day. This circulating blood delivers nutrients and oxygen to the body's organs and tissues. It also picks up waste products, which will be filtered out by the kidneys, liver and lungs. The heart's ability to keep pumping is a result of its self-generating electrical signaling system. Heart maladies may occur to this messaging system, which will dramatically impact a client's health status. These disorders are collectively known as heart arrhythmias. Understanding and recognizing the symptoms of the key heart arrhythmias is essential for exercise professionals working with a broad range of healthy and unhealthy clients.
Heartbeats 101: How the Heart Beats on Its Own
The heartbeats of the heart are autorhythmic, which means the heart produces its own pulses through electrochemical stimuli originating from a small group of cells in the wall of the right atrium, known as the sinoatrial node (or SA node). The SA node controls heart rate in healthy persons, and thus is called the pacemaker of the heart. The specialized autorhythmic cells of the SA node initiate cell messages to contract at a constant rate because their membrane charges are systematically drifting towards an electrical threshold (or trigger point) that leads to a rhythmic activation of the hearts autorhythmic system, telling the heart muscle to contract. These autorhythmic cells have organized pathways through the heart, stimulating a contraction in the contractile cells of the heart, which drives the blood through the heart (See Figure 1) and to the rest of the body.
Focus Point. Blood Flow Through the Heart: Oxygen-Poor to Oxygen Rich Blood
Oxygen-poor blood enters the right atrium via the inferior and superior vena cava. The pressure from this 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 the oxygen-rich blood through the aorta and throughout the entire body for all life-sustaining needs.
What are Arrhythmias and why are they Potentially Dangerous?
As noted earlier, the SA node is the primary pacemaker of the heart, as it possesses the fastest rate of excitation of autorhythmic cells. With arrhythmias (often interchangeably referred to as dysrhythmias), the SA node may fail to generate its electrical impulse at its normal rate, or it may stop functioning in entirety, or some other heart abnormality may be present. Consequently, autorhythmic cells in other parts of the heart will take over the role of pacemaker. This is referred to as an arrhythmia, or an irregular signally pathway in the heart. Sometimes arrhythmias occur just briefly, with the SA node quickly re-establishing its pacemaker role. Other arrhythmias, depending on their origin in the heart or how long they last, may dramatically impair the passage of blood flow through the heart and to the body. In the following sections two common arrhythmias will be explained and discussed.
Atrial Fibrillation: The Most Common Arrhythmia
Perhaps the most well-known and common heart arrhythmia is atrial fibrillation, often called AFIB. According to the American Heart Association (AHA), AFIB affects 2.7 million Americans (AHA, 2013). In AFIB, the top atria chambers of the heart 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 AHA, people with AFIB are 5 times more likely to have a stroke, and AFIB-related strokes are mote deadly then non-AFIB-related strokes. Personal trainers should note that a common symptom of AFIB is a client who reports experiencing a sudden, fast (>100 beats/ min) or an irregular resting heart rate. Some people with AFIB may not have any symptoms, but according to the AHA usual symptoms include dizziness, shortness of breath, anxiety, fatigue when exercising, disproportionate sweating, faintness, confusion, chest pressure/pain and a 'thumping' or 'palpitations' in the chest.
The three main types of AFIT 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 where the atria chambers 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 can turn into a permanent form of atrial fibrillation (AHA). Persistent AFIB is defined as an irregular rhythm that lasts for longer than 48 hours. This type of AFIB will not return to a normal rhythm on its own, requiring some form of medical treatment. Permanent AFIB occurs when the condition lasts indefinitely and is no longer manageable with medications.
Atrial or Supraventricular Arrhythmia
Atrial (or supraventricular; meaning above the ventricles) arrhythmias are fast heart rate rhythms that originate in the atria chambers of the heart. With these arrhythmias electrical signals in the heart's upper chambers fire abnormally, interfering with electrical signals coming from 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, so blood flow to the rest of the body is compromised. Personal trainers should be aware that many lifestyle conditions of some clients put the client at risk to atrial arrhythmias including: drinking large amounts of coffee, heavy alcohol drinking, high anxiety, and nicotine intake from tobacco use. Similar to AFIB, a person will complain of dizziness, lightheadedness, rapid pulse, shortness of breath and sometimes some chest pain. Under medical supervision, usually cutting down on coffee, less alcohol intake, and tobacco cessation combined with proper rest is an effective treatment.
If a client indicates any of the symptoms discussed above, or suspects he/she has a heart rhythm problem, encourage the client to see a medical professional immediately. Medical specialists have a number of effective interventions to manage arrhythmias, especially if treated early. As personal trainers expand more into the aging population, where arrhythmias are more common, being able to recognize the symptoms of common arrhythmias may help to prevent a life-threatening situation from occurring.
Side Bar 1. Four 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 ventricular (PVC) chambers 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 life, and they are somewhat common and normal in children and teenagers (AHA, 2012b). If they become more regular a health professional should be consulted to determine a cause.
2) What is Long QT Syndrome?
Long QT Syndrome is a defect of the electrical system in which the heart's electrical cells take longer than normal to recover after each heartbeat. Long QT Syndrome can be inherited or acquired after taking certain medications, or caused by a combination of medications. Persons with Long QT Syndrome may be susceptible to ventricular fibrillation (rapid, chaotic quivering of ventricles). During ventricular fibrillation, the blood pressure falls to zero, and the person falls unconscious. An immediate, life-saving shock (defibrillation) must be delivered to the heart to restore a normal rhythm.
3. What is a Heart Block?
If the electrical impulses from the upper atria chambers of the heart are not properly transmitted to the lower ventricular chambers, the condition is known as a heart block. Different types of heart block may require different treatments, depending on exactly which part of the conduction system is faulty. Other symptoms such as fatigue, lightheadedness, or fainting may develop. In some cases a permanent pacemaker 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.
Side Bar 2: How are Heart Attack Symptoms Different from Atrial Fibrillation Symptoms?
The 'thumping' and 'quivering' that occur with AFIB are the key difference from a heart attack. A heart attack is a blockage of blood flow to the heart, often caused by a clot or build-up of plaque lodging in one of the heart's coronary artery (that deliver blood to the heart muscle). A heart attack can damage or destroy some part of your heart muscle and may be sudden and intense.
Exercise Professionals Should Always be Alert to the Signs and Symptoms of a Heart Attack:
1) Chest discomfort: Uncomfortable pressure, squeezing, fullness or pain.
2) Discomfort in other areas of the body such as the arms, the back, neck, jaw or stomach.
3) Shortness of breath with or without chest discomfort.
4) Cold sweat, nausea or lightheadedness.
Fast action can save lives. Don't wait more than five minutes to call 9-1-1 or your emergency response number.
Source: American Heart Association (2012). Warning Signs of a Heart Attack
American Heart Association (2013). Atrial Fibrillation (AF or AFib)
Accessed August 25, 2013
American Heart Association (2012b). Premature Contractions
Accessed August 25, 2013
Len Kravitz, PhD, is the program coordinator of exercise science and a researcher at the University of New Mexico, Albuquerque, where he won the Outstanding Teacher of the Year award. He has received the prestigious Can-Fit-Pro Lifetime Achievement Award and American Council on Exercise Fitness Educator of the Year.