Brugada syndrome is a condition that causes a disruption of the heart’s normal rhythm. Specifically, this disorder can lead to irregular heartbeats in the heart’s lower chambers (ventricles), which is an abnormality called ventricular arrhythmia. If untreated, the irregular heartbeats can cause fainting, seizures, difficulty breathing, or sudden death. These complications typically occur when an affected person is resting or asleep.
Brugada syndrome usually becomes apparent in adulthood, although it can develop any time throughout life. Signs and symptoms related to arrhythmias, including sudden death, can occur from early infancy to late adulthood. Sudden unexplained nocturnal death syndrome (SUNDS) is a condition characterized by unexpected cardiac arrest in young adults, usually at night during sleep. This condition was originally described in Southeast Asian populations, where it is a major cause of death.
Brugada syndrome can be caused by mutations in one of several genes. The most commonly mutated gene in this condition is SCN5A which is altered in approximately 30 percent of affected individuals. This gene provides instructions for making a sodium channel, which normally transports positively charged sodium atoms (ions) into heart muscle cells. Mutations in the SCN5A gene alter the structure or function of the channel, which reduces the flow of sodium ions into cells. A disruption in ion transport alters the way the heart beats, leading to the abnormal heart rhythm characteristic of Brugada syndrome.
Mutations in other genes can also cause Brugada syndrome. Some of the additional genes involved in Brugada syndrome provide instructions for making proteins that ensure the correct location or function of sodium channels in individual heart muscle cells. Proteins produced by other genes involved in the condition form or help regulate ion channels that transport calcium or potassium into or out of heart muscle cells. Mutations in these genes disrupt the flow of ions, impairing the heart’s normal rhythm.
In affected people without an identified gene mutation, the cause of Brugada syndrome is often unknown. In some cases, certain drugs may be the culprit. Drugs that may induce an altered heart rhythm include medications that treat:
- High blood pressure
- Other mental illnesses
Abnormally high blood levels of calcium (hypercalcemia) or potassium (hyperkalemia), as well as unusually low potassium levels (hypokalemia), also have been associated with acquired Brugada syndrome.
Investigators at the Masonic Medical Research Laboratory (MMRL) have helped identify quinidine as a novel treatment for Brugada syndrome. The research done at the MMRL has developed treatments in conjunction with implantable cardiac defibrillators (ICDs) to protect patients from the arrhythmias that can lead to sudden cardiac death.
MMRL investigators have co-authored a large number of papers and reviews dealing with the Brugada syndrome published in prominent journals and textbooks. In 2003, the MMRL hosted an International Consensus Conference on the Brugada syndrome. The consensus document, highlighting diagnostic criteria and approach to therapy, appeared in Circulation and Heart Rhythm in 2005. A book entitled “The Brugada Syndrome: From Bench to Bedside” was published soon after.