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Brugada syndrome

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Brugada syndrome

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Brugada syndrome

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USMLE® Step 1 style questions USMLE

2 questions
Preview

A 24-year-old male presents to the emergency department after a witnessed syncopal episode. The patient’s parents report they had just finished dinner when their son spontaneously passed out. The patient does not recall the event and had no prodromal features. He is otherwise healthy and does not take any medications, use alcohol, tobacco, or illicit substances. Vital signs are within normal limits, and physical examination is unremarkable. Electrocardiogram is demonstrated below:


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If left untreated this patient is at risk for which of the following complications?  

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Transcript

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.

Summary

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.

Sources
  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "Brugada syndrome: Diagnosis, risk stratification and management" Archives of Cardiovascular Diseases (2017)
  5. "Brugada Syndrome" Methodist DeBakey Cardiovascular Journal (2014)