Brugada syndrome, also known as sudden unexplained nocturnal death syndrome (SUNDS), is a rare heart disease characterized by irregular heartbeat. Other symptoms may include fainting, seizures, breathing problems, nightmares, disrupted sleep, and sudden death. These problems often occur when a person is either sleeping or at rest. There are four types of Brugada syndrome.
Brugada syndrome most often affects people in their thirties. However, symptoms can appear at any age. The average age of sudden death among people with Brugada syndrome is about 40 for all types of the disease.
Brugada syndrome can be classified as type 1, type 2, type 3, or type 4. Type 1, the most studied type, is sometimes caused by mutations or defects in the SCN5A gene. The SCN5A gene provides instructions for making the cardiac sodium channel, which is essential to the normal electrical functioning and rhythm of the heart. Only about one-third of people with Brugada syndrome have been identified as having a mutated copy of this gene. Most SCN5A mutations cause arrhythmias that produce channels that continue to operate late in the cardiac cycle when normal channels are silent; such late activity creates an environment for chaotic rhythms and sudden death. Some researchers believe that some cases of sudden infant death syndrome (SIDS) are also caused by a mutation in the SCN5A gene. In those individuals without a mutated SCN5A gene, the cause of type 1 Brugada syndrome is often unknown. In some cases, a nongenetic form of Brugada syndrome may be caused by certain drugs. Drugs used to treat some forms of arrhythmia (irregular heart beat), angina (chest pain), high blood pressure, and depression and other mental illnesses can cause an altered heart rhythm.
When Brugada syndrome is inherited, or passed down among family members, it follows an autosomal dominant pattern of inheritance. This means that only one copy of the defective gene is needed for the disease to occur.
The prevalence of the syndrome is unknown, but it is estimated to occur in about one in 2,000 people worldwide. Some researchers state that the prevalence of Brugada syndrome may be five in 1,000 in Caucasians worldwide and 14 in 1,000 in Japanese worldwide. Brugada syndrome is more common among people from Japan and Southeast Asia. Known as lai tai in Thailand, bangungut in the Philippines, and pokkuri in Japan, Brugada syndrome is the most common natural cause of death in men under 50 years of age in these countries. Brugada syndrome can affect both males and females. Although the probability of having a mutated gene does not differ by sex, Brugada syndrome is about 8-10 times more common in males. This discrepancy may be linked to testosterone, a male sex hormone.
Brugada syndrome has a very poor prognosis when left untreated. One-third of patients who have suffered from syncopal episodes or have been resuscitated from near sudden death develop ventricular tachycardia within two years. Ventricular tachycardia is a fast heart rhythm that originates in the heart's ventricles. Unfortunately, the prognosis is still poor in individuals who are asymptomatic and have a typical electrocardiogram. One-third of these individuals will display a first polymorphic ventricular tachycardia or ventricular fibrillation within two years of follow-up. The only available treatment is an implantable cardioverter-defibrillator, a device connected to leads positioned inside the heart or on its surface. These leads are used to deliver electrical shocks, sense the cardiac rhythm, and sometimes pace the heart. However, left untreated, the average age of sudden death among people with Brugada syndrome is about 40.
Arrhythmias, Brugada syndrome, CACNA1C, CACNB2, cardiac channelopathy, congenital heart disease, familial arrhythmias, familial heart disease, GPD1L, idiopathic ventricular fibrillation, inherited heart disease, long-QT syndrome, right bundle branch block, SCN5A, ST segment elevation, sudden cardiac death, sudden death syndrome, sudden unexplained nocturnal death syndrome, SUNDS, tachycardia, ventricular arrhythmias.
types of the disease
General/Brugada syndrome type 1: Because Brugada syndrome type 1 (usually referred to simply as Brugada syndrome) is the most common, it is the focus of most of the available information on this disorder. Brugada syndrome type 1 is sometimes caused by mutations or defects in the SCN5A gene. The SCN5A gene provides instructions for making a cardiac sodium channel, a protein essential to the normal electrical functioning and rhythm of the heart.
Brugada syndrome type 2: Brugada syndrome type 2 is caused by a mutation in the GPD1L gene. A mutation in this genedecreases the expression of the sodium channel on the cell surface that is produced by the SCN5A gene, resulting in reduced inward sodium current and abnormal heart function.
Brugada syndrome type 3: Brugada syndrome type 3 is caused by a mutation in the CACNA1C gene. This gene belongs to a family of genes that provide instructions for making calcium channels. These channels, which transport positively charged calcium atoms (ions) into cells, play a key role in a cell's ability to generate and transmit electrical signals.
Brugada syndrome type 4: Brugada syndrome type 4 is caused by a mutation in the CACNB2 gene, which is a subunit of the L-type cardiac calcium channel. A mutation in this gene can lead to a shorter-than-normal QT interval, resulting in a faster heart rate.