Brugada Syndrome: A Silent Killer

The Brugada Syndrome

Several news outlets sensationalized an event that probably struck fear in the minds of parents concerning the deadly consequences of the all American Hot Dog.

  • “Boy takes bite of hot dog and his heart stops” – CNN
  • “Child Nearly Dies After Taking Big Bite of Hot Dog” – livescience
  • “Bite of hot dog stops 9-year-old boy’s heart, reveals Brugada syndrome” – USAToday

The last headline gives a clue of the unusual underlying condition, the Brugada Syndrome, and the article describes the scene as “the boy was eating a hot dog and he fainted”.

After resuscitation, Turkish physicians determined that the vagus nerve, the nerve that can affect the heart rate, was stimulated and slowed his heart rate down and caused him to go into cardiac arrest.

What is the Brugada Syndrome?

The Brugada Syndrome, first described in 1992 by the Spanish cardiologists Pedro Brugada (de), Josep Brugada and Ramon Brugada, is a genetic condition that affects the specialized conduction system of the heart. Specifically, it may cause ventricular tachycardia due to abnormalities in the sodium ion channels in the conduction system. Abnormalities that affect the rhythm and the contraction of the heart.

It is suggested that there are some structural differences in the normal conduction system as seen in this image highlighting the left and right bundle branches.


image: Saint Lukes Health System

The detection of Brugada Syndrome is usually determined after an event by employing electrocardiography. Since it is a genetic disorder, most physicians will test other family members as a precaution.

Where It All Starts: The Specialized Conduction System

The specialized conduction system of the heart consists of nerve tissue that initiates and transmits the electrical impulse for cardiac muscle cells to contract.

The heart has a wonderfully developed system that maintains cardiac function throughout a person's life.

To simplify it, the heart is the one organ that, given adequate nutients, and removal of waste, is self-contained and can function on its own outside of the body. New transplant technology popularly termed "heart in a box" supplies these needs to keep the heart beating until it is transplanted.

Anatomy

While the nervous conduction system is nearly impossible to see except by biopsy, the components are:

Action Potentials

The nodes create the impulse by their changing action potentials or ionic states both inside the cell and outside the cell. The normal action potentials of the heart follow a particular series of events that occur in order for myocardium to contract. The exchange of sodium, potassium, and calcium across the cell membrane is required for contraction.

The impulse is initiated and sent through the pathways until it reaches the cardiac muscle which contracts and the cycle begins again.

The specialized conduction system has three components with inherent rates

They are:

These three components are connected by nerve cells to transmit the electrical signals called internodal pathways.

The Action Potentials are composed of 4 stages of ionic exchange. A cell will not trigger an event until the cell threshhold has been reached.

P-Cell (Pacemaker Cell) Activation

P-Cells initiate the impulse through a steady trickle of sodium leaking out of the cell which changes the ionic balance of the nerve cells. Once the threshhold is reached, the nerve cells are triggered and the impulse begins.

The typical action potential of the P-Cells creates a waveform which consists of 3 phases. These cells lack a "plateau" phase and also a stable phase 4 as ions continually leak outside of the cell. This provides the "timing" or "cyclic" characteristic of the heart beat.

Non-P-Cell (Cardiac Muscle Cell) Activation

Non P-Cell potentials remain at nearly -90mv and do not initiate an impulse until the threshhold has been reached.


The miraculous sequence is that each cells has an autonomic rate at which it will stimulate an impulse.

This is the cardiac backup system at work

  • The AV node will wait unless the SA node fails to trigger at a rate between 60 - 100 and the AV node will initiate the impulse
  • The cardiac muscle cell will wait unless there is no activity from the AV node at a rate between 40 - 60 and it initiates an impulse at a rate of around 20 - 40.


The Brugada Syndrome

In Brugada Syndrome, the action potentials of many cells are not in sync and can trigger cardiac arrhythmias.

The profile of the transmural action potentials vary from the norm due to aberrations sodium ion exchange.


Brugada Action Potentials of Cardiac Muscle Non-P (Non-Pacemaker) Cells

The Electrocardiogram

The syndrome is also classified into 3 categories based on the electrocardiogram, they are:

  • Brugada Type I – Coved ST-segment elevation, high J-point amplitude ≥ 2mm, and a negative T wave
  • Brugada Type II – J-point elevation ≥ 2mm, saddleback ST-segment, positive or biphasic T-wave
  • Brugada Type III - Saddleback or coved with St-segment elevation < 1mm, T-wave not as marked

Special Procedures - The Drug Challenge

Under controlled and monitored setting, medications like procainamide or flecanide may be used to observe changes in the electrocardiogram indicating the effects in changing the ionic balance of the conduction system.

Things To Look Out For In Brugada Syndrome

Signs and Symptoms

Similar to most cardiac emergencies, the Brugada Syndrome includes:

  • Palpitations
  • Syncope
  • Seizures
  • Sudden death

Treatment

There are no cures for Brugada Syndrome but treatment methods may include channel blocking agents to minimize abnormal rhythms or an implantable cardiac defibrillator in high-risk patients.

Conclusion

Genetic testing is a trend in heart diseases that may have a familial or genetic origin. The identifications of certain genes may identify the possibility that a patient is at high risk and follow-ups are usually performed for the signs of progression at which an appropriate treatment may be planned.

So, despite the headlines, hot dogs are not to blame for cardiac arrest, however, due to the high levels of bad fats in these tubes of deliciousness, one should eat them only sparingly as part of a healthy diet.

As we always say, "Learn More!",

Richard Keith Howell Duncan, RDCS, RCS, RCIS, BBA

Links for Brugada Syndrome


The Texas Heart Institute - http://www.texasheart.org/HIC/Topics/Cond/brugada.cfm
The British Heart Foundation -
https://www.bhf.org.uk/heart-health/conditions/brugada-syndrome
American Heart Association - http://circep.ahajournals.org/content/5/3/606
Medscape - https://emedicine.medscape.com/article/163751-overview


References:

Management of patients with a Brugada ECG pattern, ESC Council for Cardiology Practice European Society of Cardiology Vol.7,N°24 - 17 Mar 2009
https://www.escardio.org/Journals/E-Journal-of-Cardiology-Practice/Volume-7/Management-of-patients-with-a-Brugada-ECG-pattern


Prof. Josep Brugada

“The Brugada Syndrome In Depth.” The Brugada Syndrome In Depth - Clinics - Stanford Center for Inherited Cardiovascular Disease - familyheart.stanford.edu/clinics/brugada2.html.

“Brugada Syndrome.” Saint Luke's Health System, www.saintlukeshealthsystem.org/health-library/brugada-syndrome.

“Brugada syndrome.” Wikipedia, Wikimedia Foundation, 2 Oct. 2017, en.wikipedia.org/wiki/Brugada_syndrome.

Reporter, Andrea Downey Digital Health. “Boy, 9, nearly dies after one bite of a HOT DOG - after it triggered freak heartbeat.” The Sun, The Sun, 7 Sept. 2017, www.thesun.co.uk/news/4411454/boy-9-nearly-dies-after-one-bite-of-a-hot-dog-after-it-triggered-freak-heartbeat/.

Scutti, Susan. “Boy Takes Bite of Hot Dog -- and His Heart Stops.” CNN, Cable News Network, 7 Sept. 2017, www.cnn.com/2017/09/06/health/hot-dog-cardiac-arrest-brugada-syndrome/index.html.

May, Ashley. “Bite of Hot Dog Stops 9-Year-Old Boy's Heart, Reveals Rare Condition.” USA Today, Gannett Satellite Information Network, 6 Sept. 2017, www.usatoday.com/story/news/nation-now/2017/09/06/bite-hot-dog-stops-9-year-old-boys-heart-reveals-rare-condition/636666001/#.

Nierenberg, Cari. “Child Nearly Dies After Taking Big Bite of Hot Dog.” LiveScience, Purch, 7 Sept. 2017, www.livescience.com/60337-child-rare-heart-disorder-brugada-syndrome.html.

 

 

 

 

 



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