Brugada syndrome is a heart condition that affects the way electrical signals travel through the heart, leading to abnormal heart rhythms. These abnormal rhythms, especially in the lower chambers of the heart called the ventricles, can be dangerous and sometimes cause sudden cardiac arrest. The root cause of Brugada syndrome lies primarily in genetic mutations that affect the heart’s electrical system.
At the core of Brugada syndrome are problems with the ion channels in heart cells. Ion channels are tiny protein structures embedded in the cell membranes that control the flow of charged particles like sodium, potassium, and calcium. These charged particles generate the electrical impulses that make the heart beat regularly. In Brugada syndrome, mutations usually affect the sodium channels, particularly the one encoded by the SCN5A gene. When this sodium channel does not work properly, the electrical signals in the heart become disrupted, especially in the right ventricle’s outflow tract, which is a critical area for maintaining a normal heartbeat.
Because the sodium channels are less effective, the heart cells cannot conduct electrical impulses smoothly. This leads to a delay or block in the electrical signals, which can cause the heart to beat irregularly or too fast. These irregular rhythms, known as ventricular arrhythmias, can be life-threatening because they prevent the heart from pumping blood effectively. The most dangerous arrhythmia associated with Brugada syndrome is ventricular fibrillation, where the heart quivers instead of contracting properly, leading to sudden cardiac death if not treated immediately.
Brugada syndrome is inherited in an autosomal dominant pattern, meaning that a person only needs to inherit one copy of the mutated gene from one parent to be at risk. However, not everyone who carries the mutation will show symptoms or have abnormal heart rhythms. This variability is due to other genetic factors, environmental influences, and possibly unknown triggers that affect how the disease expresses itself.
Besides genetic mutations, certain factors can unmask or worsen the electrical abnormalities in people with Brugada syndrome. These include fever, certain medications that affect heart rhythm, electrolyte imbalances, and excessive alcohol intake. Fever is particularly important because it can change the way ion channels function, making the heart more prone to dangerous arrhythmias in susceptible individuals. Some drugs, especially those that block sodium channels or affect other ion channels, can also trigger arrhythmias in people with Brugada syndrome.
It is important to distinguish Brugada syndrome from conditions that mimic its electrical pattern on an electrocardiogram (ECG) but are caused by other reversible factors. These are called Brugada phenocopies and can result from metabolic disturbances like high potassium levels, heart inflammation (myocarditis), or mechanical compression of the heart. Unlike Brugada syndrome, these phenocopies are not genetic and usually resolve once the underlying cause is treated.
In summary, Brugada syndrome is caused by inherited mutations that impair the function of sodium ion channels in the heart, leading to abnormal electrical activity and increased risk of dangerous heart rhythms. Environmental triggers and other health conditions can influence the severity and expression of the syndrome, but the fundamental cause remains a genetic defect in the heart’s electrical system.
