An arrhythmia refers to an abnormal rhythm of the heartbeat. Arrhythmias can happen if the heart beats too fast, too slow, or beats with an irregular rhythm, as is the case with atrial fibrillation, the most common arrhythmia in the United States.
Most arrhythmias are harmless, but some can be serious or even life threatening. When the heartbeat is too fast, too slow, or irregular, the heart may not be able to pump enough blood to the body. Lack of blood flow can damage the brain, heart, and other organs.
Everyone has felt their heart "skip" a beat or two and speed up in times of fear or excitement or during exercise. Too much caffeine and certain medications also can cause heart palpitations in some people. These types of arrhythmias are generally harmless.
However, if irregular heartbeats are frequent or chronic, they can be serious — and sometimes life threatening. The consequences of having an arrhythmia usually depend not only on symptoms they can cause (such as faintness) but also on the presence of important abnormal structural conditions of the heart and/or heart disease.
The Heart’s Natural Electrical System
The normal rhythm of the heart is a tightly regulated but dynamic phenomenon that changes according to the metabolic needs of the body. The heart has built-in pacemakers and "wiring" that coordinate contractions in the organ's upper chambers (the atria) and lower chambers (the ventricles).
First, the electrical signal from the heart's master pacemaker, the sinoatrial (SA) node located in the atria, travels to the part of the heart that connects the atria with the ventricles, reaching another natural pacemaker known as the atroventricular (AV) node. From the AV node, the electrical signal travels down a structure called “the bundle of HIS” (sometimes referred to as the AV bundle); this is the first part of the heart's "wiring" system that conducts electrical activity into the ventricles.
The bundle of HIS enters the intraventricular septum (the wall between the heart's chambers), where it subdivides into the wire-like structures called bundle branches that carry the electrical impulse to Purkinje fibers, thin filaments that continue distributing the electrical signal to the ventricles' cells. This causes the heart to contract, pumping oxygen and nutrient-rich blood into the arteries and moving it throughout the body. But what happens if there is a glitch in the heart's complicated "wiring" system causing it to "misfire"? The result can be an abnormal heart rhythm, an arrhythmia.
A heartbeat that is too fast is called tachycardia. A heartbeat that is too slow is called bradycardia.
Atrial Fibrillation (A-Fib)
Atrial Fibrillation is a rapid, irregular heart rhythm originating in the atria that can cause symptoms such as palpitations, rapid heartbeat, chest discomfort, shortness of breath and dizziness. In some individuals, atrial fibrillation increases the risk of stroke.
Ventrical fibrillation can result in an arrhythmia that originates in the pumping chambers, or ventricles, and usually occurs in people who have a damaged heart. Damaged hearts can be the result of a heart attack or structural abnormalities, like an enlarged heart. Because ventricular fibrillation is so rapid and is occurring in a damaged heart, the heart may not function properly or efficiently, and this arrhythmia can be fatal.
AV Node Re-entry Tachycardia
AV Node Re-entry Tachycardia is a rapid heart rhythm and the most common form of paroxysmal supraventricular tachycardia or PSVT, also referred to as SVT. Patients with this arrhythmia do not have structural problems with their heart, but have two pathways that can channel impulses to and from the AV node. Under certain conditions, usually following a premature beat, these pathways can form an electrical circuit, which starts a rapid (over 100 beats per minute) heart rhythm.
Wolffe-Parkinson-White Syndrome is an arrhythmia caused by an extra electrical pathway from the atria to the ventricles. Although some people with WPW do not have any symptoms, others include experience palpitations, dizziness, and chest discomfort. Rarely, WPW can be life threatening.
The following are common arrhythmia symptoms:
- Shortness of breath
- Chest pain
- Palpitations or rapid thumping in your chest
- Feeling tired or light-headed
- Passing out
Call your doctor if you have any of the above symptoms of arrhythmia, especially if you have heart disease or have had a heart attack.
The heart has four compartments, or chambers. The walls of the heart squeeze together (contract) to push blood through the chambers. The contractions are controlled by an electrical signal that begins in the heart's natural "pacemaker" (called the sinoatrial node). The rate of the contractions is influenced by nerve impulses and hormones in the blood. A problem in any of these can cause an arrhythmia.
Minor arrhythmias may be caused by excessive alcohol use, smoking, caffeine, stress or exercise. The most common cause of arrhythmias is heart disease, abnormal heart valve function and heart failure. However, arrhythmias can occur for no known reason.
Diagnosing arrhythmias involves many factors, including a careful history. People with arrhythmias may not feel any symptoms at all, or they may report symptoms that can seem unrelated to the heart, such as dizziness, fainting or shortness of breath. Some arrhythmias in otherwise healthy people can be caused by factors such as medications, diseases (including thyroid problems), diet and stress.
Emory Heart & Vascular Center arrhythmia specialists take these factors into account and conduct appropriate tests, including the ones listed below to uncover the true cause of an arrhythmia.
This test uses a machine attached to legs, arms and chest via 10 electrodes to record the heart's electric signals that create heart rhythms.
This non-invasive imaging technique creates a videotaped image of heart structures that reveals the heart's four chambers, valves and movements.
To detect irregular heart rhythms that can be fleeting, a patient wears a small phone-sized device (attached to their chest by five adhesive electrode patches) which records the heart rhythm for 24-48 hours.
This small, phone-sized recording device can detect and record arrhythmias with or without the patient experiencing any symptoms. It may be worn up to a month.
Tilt Table Test
This test helps evaluate blood pressure-related reasons for fainting (syncope). Heart rhythm and blood pressure are carefully monitored while a patient rests on a special table that tilts the patient upright at a 70-80 degree angle for 30-45 minutes. A fainting episode can indicate a person has vasovagal or neurocardiogenic fainting, which is not life threatening.
An EP study involves inserting a catheter — a narrow, flexible tube — attached to electricity monitoring electrodes, into a blood vessel, often through a site in the groin or neck. The catheter wire is guided into the heart while the patient is sedated. An X-ray-like machine provides "live" images of the catheter and heart muscle. The catheter's electrodes gather data and a variety of electrical measurements are made. During an EP study, an electrophysiologist may provoke arrhythmias and collect data about the events. This helps the doctor assess the need for an implantable device (such as a pacemaker), predict the risk of future cardiac events, and evaluate the effectiveness of certain medications in controlling heart rhythm disorders. If a heart arrhythmia is amenable to treatment by ablation, that procedure is often performed at the time of the EP study.
Electrophysiology is the cardiology specialty that diagnoses and treats heart arrhythmias, or problems related to the heart’s electrical system.
The human heart has three main components:
- The Pump - main muscular mass of the heart
- The Plumbing - all the arteries through which the blood flows
- The Electrical System - generates and regulates the heart rhythm.
The heart has a normal flow of electrical impulses from one part of the heart to another. These impulses cause the heart to contract and relax, which pumps blood to the body and vital organs.
Electrical impulses in the heart are generated by two main “pacemakers” and conducted by certain electrical “cables” or pathways. Abnormal electrical impulses cause the heart to beat too slowly, too fast, or irregularly. These electrical heart rhythm abnormalities are called arrhythmias.
An arrhythmia is any deviation from or disturbance of the heart's normal rhythm. Arrhythmias may be harmless or serious and even life threatening. The consequence of an arrhythmia depends primarily on the structural condition of the heart and the presence of heart disease.
At SoutheastHEALTH, cardiology specialists called electrophysiologists use the most advanced technology to detect, diagnose and treat arrhythmias. Today, many arrhythmias can be completely cured through a minimally invasive procedure called cardiac ablation. Others are treated and controlled by medication, implanted heart devices and/or surgical procedures.