Summary of Brugada syndrome
Transcript for Brugada syndrome
Brugada syndrome is named after Pedro and Josep Brugada, two cardiologists (and brothers!) who recognized a specific pattern of ventricular fibrillation on the electrocardiogram readings of previously healthy individuals who died suddenly. They discovered that some of these cases could be traced back to a specific genetic cause, and their findings have since been known as Brugada syndrome.
Many individuals with Brugada syndrome don’t have an identifiable genetic cause, but in some individuals, the role their genes play is very clearly defined. The most well-known of these genetic causes is a mutation in the gene SCN5A. This SCN5A mutation is inherited in an autosomal dominant pattern, meaning that a single mutation is enough to cause the disease. SC5NA codes for sodium ion channels in the cell membranes of cardiac muscle cells, and a faulty sodium ion channel affects the ability of these cells to conduct an action potential. The result, then, is that some regions of the heart end up repolarizing abnormally. In some cases, the heart might have a normal rhythm at first, which can then develop into a Brugada syndrome rhythm 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 what’s called a reentrant loop, which is when a depolarization signal starts circling 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 quickly enough that all the muscle fibers in the ventricles contract at pretty much the same time, which essentially looks like a single, coordinated contraction. If they don’t all contract around the same time, not much gets accomplished. It’s kind of like a rowboat—it works best when everyone rows at the same time, right? Well with v-fib, all the rowers stop rowing together and just row whenever they want, and the rowboat just moves in circles, and eventually sinks. Just like the rowboat, If the heart’s not squeezing anymore, and it’s just squirming around “like a bag of worms”—which is actually the description used to used explain what a heart experiencing v-fib looks like—then you can probably guess that this situation is extremely dangerous. It’s dangerous because your body, and especially your brain, isn’t getting fresh oxygen; because of this, ventricular fibrillation can lead to death within minutes of onset, and this is called sudden cardiac death.