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Brugada syndrome

Brugada syndrome (also known by some investigators as idiopathic ventricular fibrillation, IVF), is a disease associated with an electrocardiographic abnormality of right bundle branch block with ST-elevation in the right precordial leads. It has been added to the list of possible causes of sudden death in otherwise healthy, young individuals. These patients have a

propensity for life-threatening ventricular tachyarrhythmias, particularly during sleep, but no structural heart abnormalities are found.

The Brugada syndrome is a genetic disease that is manifest by abnormal electrocardiogram (ECG) findings and an increased risk of sudden cardiac death. It is also known as Sudden Unexpected Death Syndrome (SUDS), and is the most common cause of death in the young in Thailand and Laos. Brugada syndrome is due to a mutation in the gene that encodes for the sodium ion channel in the cell membranes of the muscle cells of the heart (the myocytes). The gene, named SCN5A, is located on the short arm of the third chromosome (3p21). In some cases, the disease can be detected by observing characteristic patterns on an electrocardiograph, which may be present all the time, or might be elicited by strenuous exercise, or by the administration of particular drugs. The pattern seen on the ECG is persistent ST elevations in V1-V3 with a right bundle branch block (RBBB) appearance without the terminal S waves in the lateral leads that are associated with a typical RBBB.

Heart-beat is controlled by electrical signals which are generated rhythmically in one part of the heart, and travel around it, triggering the chambers to contract in the correct order. In both muscles (of which the heart is one) and nerves, signals are conveyed by the decay of electrical fields, which have been created by the movement of minerals (particularly sodium, calcium, and potassium) across the cell membranes, creating a voltage difference between the inside and outside of the cell.

The charged mineral atoms (correctly called ions) are moved across cell membranes by protein complexes called ion-channels. These have the structure of tubes which cross the cell membrane, and they can allow, restrict, or actively move, ions of a particular element. Brugada syndrome (at least sometimes) is associated with a disorder of sodium ion channels - they overly restrict the movement of sodium ions into the cell, interfering with the regulation of the electric field, and hence the electrical signaling. There are a number of 'ion channelopathies' known, which can cause arrhythmic heart failure, either (apparently) spontaneously, or as a consequence of physical or emotional stress. Some of these involve potassium ion channels, others, calcium channels.

In some cases, the disease can be detected by observing characteristic patterns on an electrocardiograph, which may be present all the time, or might be elicited by strenuous exercise, or by the administration of particular drugs. Apart from the electrical characteristics, there are no other physical diagnostic features - so it is not detectable post mortem.

There are ethnic and sex differences in the incidence of ion channelopathies. All Italian children who play sport are routinely checked by electrocardiogram. Brugada syndrome, which is mostly seen in males, is believed to be second to traffic accidents as a cause of death to Thai men. For a very few of the ion channelopathies, the causative genetic mutation is known, and so there is the possibility of DNA-based diagnosis.

Treatment for people at high risk of sudden death is with an implantable defibrillator. This small device implanted in your chest continuously monitors heart rhythm and delivers precisely calibrated electrical shocks when needed to control abnormal, rapid heartbeats.

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