What is Heart Arrhythmia?Heart arrhythmia, or cardiac arrhythmia, is a term covering a wide variety of heart rate abnormalities - abnormalities affecting the speed or the regularity of heart rate.. These abnormalities range from being normal variants in the heartbeat through being mere annoyances or even a predisposition to higher mortality to being life-threatening itself.
Understanding cardiac arrhythmia begins with a basic understanding of the physiology of the heart rate. Every beat begins with a minute electrical signal created in what is termed the sinoatrial (or sinus) node - a small area of tissue in the right atrium (one of the four chambers of the heart). This signal causes the atria (that is both upper chambers) of the heart to contract. The signal then passes through the Bundle of His - fibers of specialized cardiac muscle cells - to the atrioventricular node and from there spreads to the ventricles (the lower chambers) through Purkinje fibers - another set of fibers of specialized cells - creating a synchronized contraction of the heart felt as the pulse.
Causes of Heart ArrhythmiaWhile many cardiac arrhythmias are caused by different diseases of the heart including coronary artery disease, heart failure, and high blood pressure, the presence of a heart arrhythmia does not necessarily indicate the presence of heart disease. Indeed, many heart arrhythmias do not have a known cause. Other known causes are fever, emotional or physical stressors, infection, other diseases such as anemia, thyroid condition, and, of course, drugs and stimulants including a number of over-the- counter and prescription medications, as well as caffeine and substances found in tobacco. Finally, certain arrhythmias are known to have at least a genetic component.
Diagnosis of Heart ArrhythmiaOften, an arrhythmia is first discovered through stethoscope or by pulse. However, while discovered, such means will not serve for general diagnosis of cardiac arrhythmia let alone for that of a specific arrhythmia. Indeed, with many cardiac arrhythmias, the signal, manifested as heart beat and pulse, may neither be audible nor felt. The electrocardiogram (ECG/EKG) is the basic diagnostic test. A twenty-four hour ECG/EKG may be required if the arrhythmia is brief or unpredictable.
Arrhythmia ClassificationArrhythmia classification (as in a specific diagnosis) is according to one or more of the following factors: the heart’s rate, the physiology of the arrhythmia, and the site of the arrhythmia’s origin, hence there are many classifications of cardiac arrhythmia.
With arrhythmia classification by heart rate, there are two classes - bradycardia and tachycardia. The normal heart rate for adults is sixty to one hundred beats per minute. A heart rate below sixty beats per minute in an adult is termed bradycardia. What causes arrhythmia when it’s bradycardia are: sinoatrial bradycardia - wherein the signal from the sinoatrial node is slowed; sinus arrest - a pause in the electrical activity of the sinoatrial node; or atrioventricular block - a blocking of the signal from the atria of the heart to the ventricles of the heart.
A heart rate greater than one hundred beats per minute in an adult is termed tachycardia. Tachycardia can result in palpitations, but tachycardia is also a normal response of the heart rate to exercise and stress. This normal response is regulated by the sympathetic nervous system in the sinoatrial node. Further, drugs and stimulants - such as caffeine or cocaine - can affect the sympathetic nervous system causing tachycardia.
Arrhythmia classification by physiological cause, typically for tachycardia not originating in the sinoatrial node, is of three classes: automaticity, re-entry, and triggered activity. Fibrillation, while seemingly a fourth class, is really a specific type of re-entry caused arrhythmia.
Automaticity concerns a signal produced by a cardiac muscle cell of its own accord. While any cardiac muscle cell is capable of producing a signal, only some cells ordinarily produce a regular signal, and those cells are especially found in the sinoatrial and atrioventricular nodes as well as the Bundle of His and the Purkinje fibers.
A re-entry arrhythmia occurs with a signal that, rather than traveling from one end of the heart to the other, actually circuits the heart recurrently. Normally, each cell will transmit a signal once in a certain, short period of time. However, when the signal is transmitted slowly in an area of the heart, it can be treated by the cells as a new signal causing an abnormal rhythm.
Triggered activity is rare though it can be caused by anti-arrhythmic medications. It is a problem within the ionic channels within cardiac muscle cells leading to abnormal transmission of signals and resulting in a sustained abnormal rhythm.
Common arrhythmia classes by the arrhythmia’s origin are: atrial, atrioventricular, junctional arrhythmias, ventricular, and heart blocks. These, in turn are subdivided and are very specific to an area of the heart.
Treatment for ArrhythmiaTreatment for arrhythmia is according to the specific arrhythmia. Many arrhythmias require no treatment at all. Others require immediate emergency treatment - especially in the case of ventricular fibrillation. Other treatment for arrhythmia involve anti-arrhythmic medications, vagus nerve stimulation - vagal maneuvers, electrical intervention, and electrical cautery utilizing specialized catheter labs.
While there are a number of anti-arrhythmic medications, each with its own mechanism for efficacy, nearly all have the potential to cause arrhythmia. Vagal maneuvers involve such activities as holding one’s breath for a few moments, placing one’s face in cold water, and even coughing. Electrical intervention may take the form of external shocks to the chest wall as with cardioversion, or it may be internal via electrodes typically with a pacemaker or an implantable cardioverter-defibrillator. Finally, electrical cautery consists of the accurate discovery of abnormal areas of signal transmission in the heart through fine probes mapping the heart’s electrical activity followed by the destruction of those areas through heat or cold or electrical or laser probes.
How is Heart Arrhythmia Prevented?A number of compounds may prevent cardiac arrhythmia including fish oil and melatonin as well as taurine. As with anti-arrhythmic medications, prevention of arrhythmia is specific to each case and requires a physician’s supervision.
Living With Heart ArrhythmiaCardiac arrhythmia, treated properly by a physician, need not be life-threatening. Treatment for arrhythmia, while as varied as the types of arrhythmias themselves, can be performed, and, indeed, many arrhythmias need not even be treated. As always, especially concerning such an important organ as the heart, always consult a physician for the treatment of arrhythmia.