USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 20-year-old man who recently immigrated from Thailand is brought to the emergency department for palpitations beginning thirty minutes ago beginning when he awoke from sleeping. He says that the palpitations were accompanied by shortness of breath and an episode of near-syncope. His medical history is non-contributory. An EKG is performed and shows slight ST elevation that is declining and is accompanied by an inverted T-wave. Within five minutes, the patient passes away and cannot be successfully resuscitated. Which of the following is the most likely cause of death?
Content Reviewers:Rishi Desai, MD, MPH
Contributors:Sam Gillespie, BSc
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.