Reviewed by Pedro R. Guevara, MDAn interruption in the normal beating rhythm of the heart or an irregularity in its pattern is called an arrhythmia. Almost everyone experiences arrhythmias in the form of a mild palpitation or a skipped heartbeat at some point in his or her life. Arrhythmias are common, especially as you get older, and they affect millions of people. Isolated incidences are usually innocuous, but a physician should look at a recurrent arrhythmia or arrhythmias accompanied by symptoms listed below.
Many types of heart disease cause arrhythmia. Coronary artery disease, which can cause a heart attack, produces scar tissue that can disrupt the transmission of electrical signals; this is caused by insufficient blood flow to the heart muscle due to sclerotic obstruction in the coronary artery. Other causes of arrhythmia include congenital heart disease, heart valve disorders, lung disease (smoking, congenital and acquired), thyroid conditions (both over active and under active thyroid), anemia, fever, alcohol, drugs such as cocaine, cigarette smoking and electrolytes abnormalities.There are many types of arrhythmias: the most common ones are tachycardia, bradycardia and an irregular heartbeat. Tachycardia is defined as a heartbeat of more than 100 beats per minute, and bradycardia is defined as a heartbeat of less than 60 beats per minute. Normally, the heart beats between 60 and 100 times per minute when someone is at rest. However, well-trained athletes achieved heart beats less than 60 beats per minutes when resting and this represents a normal physiological adaptation due to intense training activity like swimming, running, bicycling, etc.
Arrhythmias can begin in the left ventricle (the pumping part of the heart that supplies oxygenated blood to the body’s organ and tissues), right ventricle (the pumping part of the heart that supplies non-oxygenated blood to the lungs) or the left and right atria (the chamber in where the blood enters prior to being pumped into the ventricles.
Most arrhythmias are of the tachycardia type (tachyarrhythmia). Tachyarrhythmia that starts in the ventricle is usually more serious than one that starts in the atria. Ventricular arrhythmias are more serious because the ventricles are reduced to twitching, and almost no pumping takes place, thus the blood cannot get to other parts of the body. Atrial tachyarrhythmia can be serious, because again, the atrial is reduced to twitching and clots may build up in the atria. If the clot breaks loose from the atria, an embolus (small clot) can be sent to various parts of the body, and may cause an artery occlusion, resulting in a compromised blood supply to tissues and vitals organ such the brain, kidneys, gastrointestinal track as well as fingers, hands, legs or toes. This last phenomenon is defined as ischemia and if the deficiency is in the brain tissue, it is commonly recognized as an embolic stroke.
Bradycardias (Bradyarrhythmias) are sometimes caused by problems or defects with the nerves that control the speed your heartbeat (the sinus node, where the electrical impulse that controls the heart beat originates), or the transmission of those impulses through the heart. Atrial bradyarrhythmias occur when the sinus node is not functioning correctly. This can be due to an injury associated with, aging, coronary artery disease secondary to elevated cholesterol or other conditions that can cause problems in the conducting system of the heart.
Ventricular arrhythmias occur when the electrical conducting system (the wiring) from the sinus node to the heart does not function properly. The ventricle itself has its own intrinsic beat of about 45 beats per minute that it generates by itself if the conducting system from the atrium fails. However, if it becomes chaotic due to lack of regulation from the sinus node or conditions that can trigger a catecholamine surge, heart rates of greater than 120 beats per minute can be generated. These conditions are associated with heart muscle injury such as Myocardial Infarction (MI), thyroid diseases, high fever, anemias, and response to toxic substances such cocaine, caffeine or medications.
Irregular heartbeats occur when there is some problem with the electrical system of the heart or when the atria send out too many signals (i.e. other parts of the atrium other than the sinus node send out a signal for the ventricles to contract).
Symptoms of tachycardia include:
Recurrent palpitations that may feel like a strong neck pulse or a fluttering, pounding, or racing beat in the chest
Chest discomfort
Weakness, fainting, shortness of breath, dizzinessSymptoms of bradycardia include:
Fatigue
Shortness of breath
LightheadednessSymptoms of an irregular heartbeat may be all of the symptoms for either tachycardia or bradycardia.
Related is Brugada syndrome, an abnormality in the heart's electrical system that causes arrhythmia. It is most common in young people and Asians, but the cause is unclear. During a Brugada episode, decreased oxygen flows to the brain, causing fainting. Chaotic heart beat and/or death can ensue - unless the heart receives an immediate electrical shock from a defibrillator.
Diagnosis:
A thorough history of symptoms suggesting irregular heart beats, medical problems, alcohol, tobacco, drug use and a physical exam that includes oscultating heat sounds, and palpating pulses are all primordial in assessing arrhythmias.
An ECG of the heart is the initial and gold standard test to detect an arrhythmia; it is a cost-effective and non-invasive procedure. If an arrhythmia is suspected in a patient and it is not detected at the doctor’s office, patients may be sent home with a Holter monitor. This portable device can record the heart’s activity over a 24-hour period.
A stress test may provoke arrhythmia, so running on a treadmill as part of an assessment may make the diagnosis easier. Echocardiogram, or ultrasound of the heart, can detect an accompanying heart muscle or valve disease.
To determine if arrhythmias are caused by coronary artery disease, a cardiac catheterization may be performed. The doctor inserts a catheter into a blood vessel and guides it to the heart via X-ray. Contrast dye is injected so that the heart can be viewed.
Other diagnostic guidelines includes: Thyroid function test, toxicology and evaluation of electrolytes disorders.
Treatment of arrhythmias varies from patient to patient and to the type of the arrhythmia. Very important is also to evaluate and treat any underlying disorder responsible for the arrhythmia such as thyroid disease, psychiatric disorder or agents like drugs or alcohol. In some cases, no treatment is necessary. These are the so-called benign arrhythmias. Physicians usually advise limiting your intake of caffeine, quitting smoking, and limiting your alcohol consumption. You should also consider relieving stress with exercise, meditation, or counseling. For people with more serious arrhythmias, your physician will discuss various treatment options. Antiarrhythmic drugs are available, such as Quinidine and Admidarone. Your doctor may prescribe one for you, depending upon the type of arrhythmia and medical, drug and social history.
Another form of treatment is an implanted pacemaker, especially for people with bradycardia. People with ventricular tachycardias may use an implantable cardioverter defibrillator, which provides shock therapy when needed. This resource is usually applied to patients who present with a compromised clinical situation such as chest pain, hymodinamically instability or heart failure.
Another option is catheter ablation. In this procedure, the part of the heart causing the interference is purposefully damaged to prevent it from sending electrical impulses.
In more serious cases, open-heart surgery may be necessary to treat heart valve disease that may cause arrhythmias.
In an emergency situation, arrhythmia is treated with electric shock.
