Archive for the ‘cardiac electrophysiology’ Category

A 5-minute session: Answers are my own. Please cross-check.

1. Is Brugada syndrome clinical or ECG diagnosis?

Always clinical. Never get confused on this.

2. Spontaneous type 1 vs Induced Type 1 (from type 2) which carries more risk?

Both are risky since they are close cousins. But, spontaneous type 1 is the dreaded devil. 

3. Is Brugada primarily a defect of myocardial depolarization or repolarisation?

Not clear. Often in both. In fact a mismatch between them. (Don’t ask how Na+ Channel defect affects repolarisation !)

4. Is Brugada VT is monomorphic, polymorphic?

Both. What determines morphology is not clear though. (All de-nova monomorphic VT will degenerate to polymorphic en route to cardiac arrest)

5. Should  Fever induced Brugada pattern be investigated further?

Better, it is not to be reported in ECG. May not be important in the majority if there is no adverse family history. (If the patient is well educated and afflicted  by Dr.Google and cardiologists can’t escape from ordering sophisticated tests)     

6. What is the overlap between ERS and Brugada?

It is all about the Idiosyncrasy of the K+ channel phenotypes ( Transmural dispersion heterogeneity )  

7. Is a benign Brugada better than a malignant ERS?

Yes, it would seem so. (Inferior or Infero -lateral ERS prone for primary VF in case they develop ischemic / ? also non-ischemic stress)

8. How important is the link between Brugada and Long QT 3 syndrome?

A rare entity, but It is double jeopardy for VT risk. The entire action potential width is vulnerable right from phase 0 to 3 or 4 A case report Sandhu A Clin Case Rep. 2017;5(8):1315-1319.

9. Is Amiodarone really contraindicated in VT?

Not really. Though Amiodarone unmasks Brugada, it can still be used during episodes of VT in patients with manifest or unmanifest Brugada. Maybe in Long QT 3 overlap, it may perpetuate the VT.

10. How important is the structural myocardial defect in Brugada?

Not important in the majority. Though localized RVOT abnormalities are noted in some..RV abaltion can be succesful in odd case.

11. What happens to the ST segment in Brugada during exercise stress?

ST-segment may normalize in some. A stress test can help to risk stratify.  Subramanian M, J Cardiovasc Electrophysiol. 2017 Jun;28(6):677-683.0

12. Which drug is probably best for Brugada as of now?

Quininde , A fairly specific blocker of Ito current. However, it needs to be used diligently. Management of Brugada Syndrome: Belhassen B, Rahkovich M, Michowitz Y, Glick A, Viskin S Circ Arrhythm Electrophysiol. 2015 Dec; 8(6):1393-402.

13. Is ICD definitive therapy?

Obviously not. But, definitely life-saving in high-risk survivors. I guess definitive therapy is possible for future generations through the science of genetic reprogramming of Na+ channels. (Of course, our planet shouldn’t succumb to man-made climatic arrhythmia, by then ) 

14. Does widespread genetic testing & screening of families help in the management and reduce anxiety?

Cracking the genomic code of cardiac ion channels is the ultimate sophistication (Blueprint of fate ?) However, there is no guarantee this information is going to ease out the family members who harbor a genocopy with or without a phenocopy. 

15. Is Brugada getting undue attention in cardiology literature compared to many other common arrhythmias?

      You can answer this …………………………………….


Further reading

Li KHC, Lee S, Yin C, et al. Brugada syndrome: A comprehensive review of pathophysiological mechanisms and risk stratification strategies [published correction appears in Int J Cardiol Heart Vasc. 2020 Dec 19;32:100699]. Int J Cardiol Heart Vasc. 2020;26:100468. Published 2020 Jan 21. doi:10.1016/j.ijcha.2020.100468


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How many times you have treated cardiac arrhythmia in both emergency & non-emergency situations?

Infinite times.

How many times did you really bother to know the mechanism of a given arrhythmia before ordering medication or shocking?

Hmm,.. let me think. (Except for AVNRT/ AVRT, and few VTs, very rarely I have worried about the mechanism  !)

Why is it so? because treatment takes priority and we are able to tame the arrhythmia even without knowing the real mechanism.

The following slide is a gross summary of the cardiac arrhythmia mechanism

Understanding cardiac arrhythmia is vitally important for a few reasons in a few settings.

  • In acute settings, we need to know automatic tachycardias will not respond to shocks. Reentry tachycardias will respond more promptly. (Of course, we may not know it till we shock ) Calcium blockers like verapamil might block triggered activity in MAT. Overdrive pacing is the answer for many automatic tachycardias and some refractory reentrant tachycardias (ATP protocols in ICD has taught us this ) 
  • In the chronic setting when you contemplate mapping, locating, and ablating arrhythmias, mechanisms are important. The task here is locating slow conduction paths and decoding the diastolic circuit around the scar  (If you plan ICD, knowledge about mechanism  becomes redundant again)

  • Finally, knowing the mechanism of arrhythmia is a fascination by itself to help understand the great subject called cardiac electrophysiology, where 100s of ion channels work nonstop drawing the action potential on a moment to moment basis sustaining our life.

A challenge

Can you localize a VT and find the mechanism in a patient who is Ischemic /hypoxic and acidotic? You can never do it. Please note, most polymorphic VTs can’t be localized. The mechanism is either automaticity, trigger activity, or even micro-reentry. You need to shock and look for the causes.(Link to How does the treatment of monomorphic VT differ from Polymorphic VT? )

Final message

Should we need to know about the mechanism of arrhythmia we treat?  Definitely yes, if you have that passion to know the truth, or else just order Amiodarone or shock and check out of CCU. (Of course, we have a very good option of calling EP consult the next day.)

 A review article on mechannism of cardiac arrhymias

Rev Esp Cardiol. 2012;65(2):174–185

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