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Brugada syndrome p. 301
Brugada syndrome is named after two Spanish brothers, Pedro and Josep Brugada, who recognized a specific pattern of ventricular fibrillation on the electrocardiogram or ECG, of previously healthy individuals who had a sudden death! They identified this as Brugada syndrome and found that some cases could be traced back to a specific genetic cause.
Many individuals with Brugada syndrome don’t have an identifiable genetic cause, but in some individuals, there is one. The most well-known cause is a mutation in the gene SCN5A. The SCN5A mutation is inherited in an autosomal dominant pattern, meaning a single mutation is enough to cause the disease.
The gene codes for sodium ion channels in the cell membranes of cardiac muscle cells, and a faulty sodium ion channel affects the heart cell’s ability to conduct an action potential. So the mutation results in some regions of the heart having abnormal repolarization. In some cases, the heart might have a normal rhythm but then develop into a Brugada syndrome in the presence of certain medications like sodium channel blockers.
On an electrocardiogram, Brugada syndrome typically has ST elevations (which are often a sign of ventricular strain), as well as a right bundle branch block, which indicates that the ventricles aren’t depolarizing normally. As a result, these regions become susceptible to a reentrant loop, which is when a depolarization signal starts going around and around in a loop, causing ventricular tachycardia and sometimes ventricular fibrillation.
Ventricular fibrillation, sometimes called v-fib, means the heart’s muscle fibers start quivering because they’re not contracting at the same time. Normally, an electrical signal spreads fast enough so that all of the muscle fibers in the ventricles contract almost at the same time, which essentially looks like a single, coordinated contraction.
Brugada syndrome is a potentially life-threatening condition that can cause sudden cardiac death. The condition is characterized by abnormal heart rhythms (arrhythmias) on ECG and a predisposition to developing ventricular fibrillation, a particularly dangerous type of arrhythmia. People with Brugada syndrome often have no symptoms, making the condition difficult to diagnose. However, in some cases, people with the condition may experience episodes of palpitations, fatigue, and shortness of breath.
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