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Arrhythmias (heart)

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Cardiac dysrhythmia
ICD-10 I47 - I49
ICD-9 427
OMIM [1]
DiseasesDB 15206
MedlinePlus 001101
eMedicine /
MeSH {{{MeshNumber}}}



Some arrhythmias are life-threatening medical emergencies and can result in cardiac arrest. Cardiac arrythmias are one of the most common causes of death when travelling to a hospital. Others cause symptoms such as an abnormal awareness of heart beat (palpitations) and may be merely uncomfortable. These palpitations have also been known to be caused by atrial/ventricular fibrillation, wire faults, and other technical or mechanical issues in cardiac pacemakers/defibrillators. Still others may not be associated with any symptoms at all, but may predispose the patient to potentially life threatening stroke or embolism.

The term sinus arrhythmia refers to a normal phenomenon of mild acceleration and slowing of the heart rate that occurs with breathing in and out. It is usually quite pronounced in children and steadily decreases with age. This can also be present during meditation breathing exercises that involve deep inhaling and breath holding patterns. Proarrhythmia is a new or more frequent occurrence of pre-existing arrhythmias, paradoxically precipitated by antiarrhythmic therapy, which means it is a side effect associated with the administration of some existing antiarrhythmic drugs, as well as drugs for other indications. In other words, it is a tendency of antiarrhythmic drugs to facilitate emergence of new arrhythmias. Some arrhythmias are minor and can be regarded as normal variants. In fact, most people will on occasion feel their heart skip a beat or give an occasional extra strong beat; neither of these is usually a cause for alarm.[3]


Arrhythmia may be classified by rate (normal sinus rhythm, tachycardia, bradycardia) or mechanism (automaticity, reentry, junctional, fibrillation).

It is also appropriate to classify by site of origin:


Junctional arrhythmiasEdit


Heart blocks Edit



SADS, or sudden arrhythmic death syndrome, is a term (as part of, Sudden unexpected death syndrome) used to describe sudden death due to cardiac arrest brought on by an arrhythmia in the absence of any structural heart disease on autopsy. The most common cause of sudden death in the US is coronary artery disease.[citation needed] Approximately 180,000 to 250,000 people die suddenly of this cause every year in the US. SADS occurs from other causes. There are many inherited conditions and heart diseases that can affect young people and subsequently cause sudden death. Many of these victims have no symptoms before dying suddenly.[citation needed]


Signs and symptomsEdit


The most common symptom of arrhythmia is an abnormal awareness of heartbeat, called palpitations. These may be infrequent, frequent, or continuous. Some of these arrhythmias are harmless (though distracting for patients) but many of them predispose to adverse outcomes.





Differential diagnosisEdit

Normal electrical activityEdit

Main article: Electrical conduction system of the heart

Each heart beat originates as an electrical impulse from a small area of tissue in the right atrium of the heart called the sinus node or Sino-atrial node or SA node. The impulse initially causes both atria to contract, then activates the atrioventricular (or AV) node which is normally the only electrical connection between the atria and the ventricles (main pumping chambers). The impulse then spreads through both ventricles via the Bundle of His and the Purkinje fibres causing a synchronised contraction of the heart muscle and, thus, the pulse.

In adults the normal resting heart rate ranges from 60 to 80 beats per minute. The resting heart rate in children is much faster. In athletes though, the resting heart rate can be as slow as 40 beats per minute, and be considered as normal.


File:Sinus pause.PNG




Tachycardia that is not sinus tachycardia usually results from the addition of abnormal impulses to the normal cardiac cycle. Abnormal impulses can begin by one of three mechanisms: automaticity, reentry or triggered activity. A specialised form of re-entry problem is termed fibrillation.

Although the term "tachycardia" is known over one hundred year, basis for the classification of arrhythmias are still being discussed.[B: 2]

Heart defects causing tachycardiaEdit

Congenital heart defects are structural or electrical pathway problems in the heart that are present at birth. Anyone can be affected with this because overall health does not play a role in the problem. Problems with the electrical pathway of the heart can cause very fast or even deadly arrhythmias. Wolf-Parkinson-White syndrome is due to an extra pathway in the heart that is made up of electrical muscle tissue. This tissue allows the electrical impulse, which stimulates the heartbeat, to happen very rapidly. Right Ventricular Outflow Tract Tachycardia is the most common type of ventricular tachycardia in otherwise healthy individuals. This defect is due to an electrical node in the right ventricle just before the pulmonary artery. When the node is stimulated, the patient will go into ventricular tachycardia, which does not allow the heart to fill with blood before beating again. Long QT Syndrome is another complex problem in the heart and has been labeled as an independent factor in mortality. There are multiple methods of treatment for these including cardiac ablations, medication treatment, or altering your lifestyle to have less stress and exercise. It is possible to live a full and happy life with these conditions.






Re-entrant arrhythmias occur when an electrical impulse recurrently travels in a tight circle within the heart, rather than moving from one end of the heart to the other and then stopping.[A: 2][A: 3]

Every cardiac cell is able to transmit impulses of excitation in every direction but will only do so once within a short time. Normally, the action potential impulse will spread through the heart quickly enough that each cell will only respond once. However, if there is some essential heterogeneity of refractory period or if conduction is abnormally slow in some areas (for example in heart damage) so the myocardial cells are unable to activate the fast sodium channel, part of the impulse will arrive late and potentially be treated as a new impulse. Depending on the timing, this can produce a sustained abnormal circuit rhythm.

As a sort of re-entry, the vortices of excitation in the myocardium (autowave vortices) is considered to be the main mechanism of life-threatening cardiac arrhythmias. [B: 1] In particular, the autowave reverberator is a typical in thin walls of the atria, with the atrial flutter producing. Re-entry are also responsible for most paroxysmal supraventricular tachycardia, and dangerous ventricular tachycardia. These types of re-entry circuits are different from WPW syndromes in which the real pathways existed.

Although omega-3 fatty acids from fish oil can be protective against arrhythmias, in the case of re-entrant arrhythmias, fish oil can worsen the arrhythmia.[A: 4]


When an entire chamber of the heart is involved in a multiple micro-reentry circuits and, therefore, quivering with chaotic electrical impulses, it is said to be in fibrillation.




Triggered beatsEdit


Diagnostic approachEdit



A more advanced study of the heart's electrical activity can be performed to assess the source of the aberrant heart beats. This can be accomplished in an Electrophysiology study. A minimally invasive procedure that uses a catheter to "listen" to the electrical activity from within the heart, additionally if the source of the arrhythmias is found, often the abnormal cells can be ablated and the arrhythmia can be permanently corrected.


The method of cardiac rhythm management depends firstly on whether or not the affected person is stable or unstable. Treatments may include physical maneuvers, medications, electricity conversion, or electro or cryo cautery.

Physical maneuversEdit


Antiarrhythmic drugsEdit

Main article: Antiarrhythmic agents


Other drugsEdit

A number of other drugs can be useful in cardiac arrhythmias.









Electrical cauteryEdit



See alsoEdit


  • Books
  1. 1.0 1.1 (1995) Cardiac Arrhythmias: Their Mechanisms, Diagnosis, and Management, 3, Lippincott Williams & Wilkins.
  2. (2012) "Tachycardia as “Shadow Play”" Tachycardia, 97–122, Croatia: InTech.
  • Papers
  1. (2008). Epidemiology of Sudden Cardiac Death: Clinical and Research Implications. Progress in Cardiovascular Diseases 51 (3): 213–28.
  2. (1946). The mathematical formulation of the problem of conduction of impulses in a network of connected excitable elements, specifically in cardiac muscle. Archivos del Instituto de Cardiología de México 16 (3): 205–65.
  3. (1976). Circus movement in rabbit atrial muscle as a mechanism of tachycardia. II. The role of nonuniform recovery of excitability in the occurrence of unidirectional block, as studied with multiple microelectrodes. Circulation Research 39 (2): 168–77.
  4. (2007). Pro- and antiarrhythmic properties of a diet rich in fish oil. Cardiovascular Research 73 (2): 316–25.
  • Web-sources

External linksEdit


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