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Atrial Tachycardia; is the name for an arrhythmia caused by a disorder of the impulse generation in the atrium or the AV node. An area in the atrium sends out rapid signals, which are faster than those of the sinus node, these signals then become the primary pacemaker in the heart. Sustained tachycardia can occur but more often the arrhythmia occurs in short bursts. See Paroxysmal Supraventricular Tachycardia PSVT.

Accessory AV Pathway or Bypass Tract; an extra (in addition to the AV node) electrical connection called the bypass tract is present between the atria and the ventricles. AV Reentry Tachycardia is frequently caused by the presence of the bypass tract. Where the bypass tract causes the QRS complex to become abnormal this condition is referred to as Wolff-Parkinson-White (WPW) Syndrome.

Arrhythmias; abnormal heart rhythm. Disturbances of the hearts electrical system can cause several different heart rhythm problems. Slow rhythms generally occur when the electrical signal is blocked. Fast rhythms normally occur when the electrical signal takes the wrong path or the signal continues to travel in a circular path around the heart. The most serious arrhythmias cause the ventricle fibrillation (quiver, flutter) such that the heart cannot pump blood.

Arrhythmogenic Right Ventricular Dyplasia ARVD; a familial cardiomyopathy. Progressive damage to the right ventricle muscle tissue giving rise to potentially life threatening tachycardia originating from the right ventricle.

Atria; The upper chambers in the heart, they receive blood from the veins and store it prior to each heartbeat.

Atrial fibrillation (also known as A Fib or AF); the electrical signals to the atrium become rapidly circulating waves continuously stimulating the atrium. The heart beat becomes very rapid. It is an example of supraventricular tachycardia.

Atrial flutter; the electrical activity around the atrium causes a very fast heartbeat (250-350), the electrical activity is not disorganised.

Atrial Premature Beats, APBs; an abnormal electrical signal in the atrium causes premature heartbeats. A fluttering feeling may be noted in the chest.

Atrioventricular Nodal (AV) Reentry Tachycardia AVNRT; an arrhythmia caused by the electrical signal travelling in a circular path around the heart. This happens due to extra tissue near to the AV node providing a bypass or short circuit. AV nodal reentrant tachycardia is the most common type of Paroxysmal Supraventricular Tachycardia PSVT & SVT.

Atrioventricular Nodal (AV) Reentry Tachycardia; see WPW and PSVT

Atrioventricular Node (AV node); the connection point between the atrium and the ventricles of the group of fibres that conduct the electrical signal controlling the heartbeat. See his-Purkinje system.

AV Block, Heart Block or Bundle Block; this is not a physical blockage of blood flow, it is a blockage of the electrical signals. AV block occurs when the AV Node fails to properly conduct the impulses from the atria to the ventricles. AV block causes an abnormally slow heart rhythm.


Bradycardia; an arrhythmia that causes abnormally slow heart rhythm, the heart beat is less than 60 bpm.

Brugada Syndrome; idiopathic ventricle fibrillation with right bundle branch block and ST segment elevation. This syndrome is more common in Japan and South East Asia.

Bundle of His; see His-Purkinje system.


Cardiac cycle; the cycle of events the heart valves and muscles go through in one heart beat.

Cardiomyopathy; the heart muscle is abnormal without any apparent cause.

Congestive Cardiomyopathy; loss of pumping efficiency due to dilation, normally caused by alcoholism, diabetes or drug toxicity.

Congestive Heart Failure; the heart still functions but its ability to pump becomes reduced.


Dilated Cardiomyopathy DCM; fatal ventricular or bradycardia arrhythmia may be caused by diseased damaged heart tissue. Dilated means enlarged.

Dysrhythmias; are abnormal heart rhythms that can decrease the heart’s pumping effectiveness. Normally the heart beats at a rate of 60-100 times a minute. If left untreated, a dysrhythmia can lead to more serious cardiovascular problems and can be life-threatening. There are basic atrial, junctional, ventricular and sinus dysrhythmias.


Electrocardiogram, ECG, EKG; the electrical signals controlling the heart rhythm are measured on the surface of the skin, the trace produced is used by doctors to see if an arrhythmia is present.

Endocarditus; refers to inflammation of the endocardium (inner layer of the heart wall).

Epicarditus; refers to inflammation of the epicardium (external visceral layer of the heart wall).


Familial; familial may be used with many of these terms when the condition is inherited.


His-Purkinje system; the fibres that the electrical signal that controls the heart beat travel along, the pass over the atrium, through the AV node and over the ventricles.

Hypertrophic Cardiomyopathy HCM; heart muscle thickening occurs without any apparent cause.


Idiopathic Dilated Cardiomyopathy; idiopathic means unknown cause, thus the reason for the enlarged heart is unknown.

Idiopathic Ventricular Tachycardia; differs from ventricular tachycardia because the fast heart rhythm does not arise from an underlying heart problem. With Idiopathic VT, disturbances in the electrical signal cause the ventricular tachycardia, this can occur due to exercise.

Impulse Conduction; the ability of the electrical signals to flow through the various tissues of the heart. An inability to correctly conduct the signals will result in an arrhythmia such as AV block.

Impulse Generation; the electrical signal controlling the rhythm is generated in the heart tissue. A disorder may cause a slow rhythm or a fast rhythm.

Intra-atrial Reentry Tachycardia; the electrical signal travels in a circular path around the atrium. See Paroxysmal Supraventricular Tachycardia PSVT.

Ions; the atoms of potassium, sodium and calcium have very small charges of electrical energy, the charge may be positive or negative. With the electrocardiogram we measure the movement of these ions in the heart tissue cells. The movement of calcium cells within the AV node are responsible for the impulse generation. Most of the hearts tissue cells are sodium dependant.


Myocarditis (viral) is an inflammatory disease of the heart. This is usually the heart muscle but it can involve other tissues in the heart. Viral myocarditis has been demonstrated to be induced primarily by at least two types of viruses, enteroviruses and adenoviruses.

Myocarditus; refers to inflammation of the myocardium (middle layer of the heart wall).


Normal heart rate; between 60 to 100 beats per minute.


Palpitation; the patient feels an abnormal heart rhythm in the chest, this may be racing, fluttering fast arrhythmia or a slow heavy rhythm. Paroxysmal; a temporary disturbance.

Paroxysmal Supraventricular Tachycardia PSVT; this term can cover a number of arrhythmias caused by problems with the electrical signals conduction path. Reentry is normally present and is caused by a short circuit in the signals path near the AV node, this causes the signal to travel continuously in a circular path around the heart. Severe symptoms of palpitations, lightheadedness, shortness of breath, sweating, and chest pain may be present. See SVT.

Pericardium; Heart enclosed in pericardial sack which confines heart to its position in medistinum, but still allows vigorous movement during exercise.


Reentry (reentrant): is a common cause of tachycardia, it results if the electrical signal travel continuously around the heart in a circular pathway.


SADS (Sudden Arrhythmic Death Syndrome): Sudden arrhythmic death syndrome, or SADS, is when someone dies suddenly following a cardiac arrest and no obvious cause can be found. This affects around 500 people in the UK every year.

SCA (Sudden Cardiac Arrest); the abrupt loss of heart function, breathing and consciousness. The condition usually results from an electrical disturbance in your heart that disrupts its pumping action, stopping blood flow to your body.

Sinoatrial or SA node or Sinus node; these cells are situated in the right atrium, the electrical signal controlling the heartbeat starts from these cells.

Sinus Bradycardia; the sinus node, which normally controls the overall heart rate, is generating the electrical signals too slowly reducing the heart rate to less than 60bpm.

Sinus tachycardia; the sinus node is producing rapid electrical signals increasing the heart rate. Palpitations, lightheadedness and fatigue are often experienced.

Sudden Arrhythmic Death Syndrome (SADS); Sudden arrhythmic death syndrome, or SADS, is when someone dies suddenly following a cardiac arrest and no obvious cause can be found. This affects around 500 people in the UK every year.

Sudden Cardiac Arrest (SCA); the abrupt loss of heart function, breathing and consciousness. The condition usually results from an electrical disturbance in your heart that disrupts its pumping action, stopping blood flow to your body

Supraventricular arrhythmias; supra means above, this is thus an arrhythmia produced in the tissues above the ventricles.

Supraventricular tachycardia SVT; a rapid heartbeat starting from above the ventricles ie. in the sinus node, the atrium or the AV node. See AVNRT & Atrial tachycardia.

Syncope; sudden and temporary loss of consciousness.


Tachycardia; a fast heart rhythm, arrhythmias that cause the heart to beat above 100 bpm.


Ventricles; The lower chambers of the heart that do main pumping work.

Ventricular arrhythmias; arise from the lower chambers of the heart.

Ventricular fibrillation VF or V-Fib; a disorganised fast rhythm of the lower chambers, it is often the cause of sudden death.

Ventricular premature beats VPBs; rise from the ventricles. The ventricles contract before the atria causing palpitations.

Ventricular tachycardia VT or V-Tach; this arrhythmia causes a high (200/300bpm) heart beat which prevents the ventricles filling correctly, this effectively stops the heart pumping and is potentially life threatening. The tachycardia generally starts from the edge of scar tissue from a previous heart attack.


Wolff-Parkinson-White (WPW) Syndrome; this is a particular form of PSVT that can be life-threatening, the electrical signal short-circuits and bypasses the AV node, this causes the QRS complex to become abnormal. The WPW Syndrome has been associated with sudden death in young people.

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