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Posts Tagged ‘ers pattern’

J point is a critical point in the  ECG  when the ventricles hand over the baton in  the  electrical relay race from depolarization to repolarization .This the time the sodium  channels extinguish itself  and the potassium current begins its activity  from Phase 0 to 1 .

If the  potassium channels  activate little early and snatch the baton prematurely from sodium , we get early repolarization pattern .When this happens , the J point of ECG show a conspicuous wave  called J wave , originally  denoting  Junctional wave between QRS/ST segment  (Now  perceived as  Jitter waves ?) The other implication of premature K+ activity is , lifting up of  ST segment , making it the most common cause of non ischemic ST elevation.

* J wave in hypothermia is referred to as Osborne wave and  may not be  not related to ERS(Ref.4)

J wave and J point early repolarisation syndrome

Image source.www.cardiology.org

The Ito current is responsible for the phase  1 of action potential (AP), where a rapid outward k + ion flux take place and draws the dome of AP . The dynamics of Ito is complex .It depends  upon the density of epicardial K + channels , which are  clustered in a heterogeneous manner .There seems to be a concentration gradient   along the epicardium and endocardium , making the wave appear prominent in some. This is especially true in healthy, athletic  male population  where we have some evidence for androgen  to  play a role on how  these channels will behave.Here comes the overlap between Brugada  syndrome and ERS as well.

The subset of patients with J wave pattern were recently shown to have increased risk of primary VF due to phase 2 reentry ,  when they develop ACS. (Rather J wave pattern was more common in patients who had primary VF following STEMI(Ref 1).This resulted in a spate of worrying articles .Now we know , the  fear is  largely unfounded ,the risk is far less.

Current thinking is,  persons who have asymptomatic ERS pattern with prominent J waves should not be investigated electro-physiologically . (Please remember , every human  heart can be induced  to VF in EP lab  if appropriately  stimulated ! )

In fact , I used to tell the  young men  who  harbor  prominent J wave , as a marker of healthy heart  rather. Let us not  fear them with a remote risk  that could be as  negligible as risk of  intercontinental flight crashing into the ocean  !

References

1.Haissaguerre M, Derval N, Sacher F, et al. Sudden cardiac arrest associated with early repolarization. N Engl J Med. 2008;358:2016–2023.

2.Idiopathic Ventricular Fibrillation “Le Syndrome d’Haïssaguerre” and the Fear of J Waves , Sami Viskin, J Am Coll Cardiol. 2009;53(7):620-622. 11

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In the last few decades  we have  understood a major concept in the genesis of cardiac arrhythmia.Slowing in the propagation of cardiac impulse is a key  trigger to precipitate a reentry circuit and initiate a tachy- arrhythmia.Still , many conditions like first degree AV block, chronic RBBB or even LBBB are  benign entities  as along as the heart is structurally normal .They seem never increase the incidence or life time risk of  cardiac arrhythmia . Longevity is unaffected.( Or do we assume many things ?)

How is this possible ? or is the theory of slow conduction triggering reentry is flawed ?

Think again . . . if these patients who later on develop a structural heart disease , with an episode of ACS , myocardial or valvular disease,  the original slow conduction substrates these people were harboring ,  will it become important ?

Surprisingly , we have no answers in literature.When Haissaguerre et al found preexisting ERS pattern could be a trigger for primary  VF in case they develop ACS  , he opened up a huge debate as it involved converting  a vast number of normal population electrically anxious.

Now ,is it possible the so called  benign  blocks of heart like first degree AV blocks , RBBB , LAHBa , would be important  at times of ACS  and possibly make them prone for for primary ischemic arrhythmia .

Is bundle branch re-entry possible in structurally normal heart ?

We need answers. Some one , (Any EP fellow) somewhere  could take up the issue and enlighten us !

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Often general practitioners refer  ECGs  with abnormal resting  ST/T wave patterns  to cardiologists .

Following are few of them

  • ST elevation
  • ST depression
  • T wave inversion
  • Tall T waves
  • A relatively uncommon  finding is  a flat ST segment  , which  is discussed here.

The commonest( benign) abnormality   is  T wave inversion  in women and tall ST /T waves   reflecting  early repolarisation  pattern in men. A flat ST segment is an occasional finding in general population.

ST segment is inscribed  during the most important  time  of  cardiac cycle.This is the period the ventricle is doing its prime function , namely ejecting the blood in systole .Hence it is subjected to maximum stress . During times of ischemia  ST segment  gets elevated or depressed depending upon the severity of ischemia. For the same reason , even  subtle changes in this segment is  frowned upon by cardiologists. Most of them would receive a EST.

It is ironical to note  , few normal people  show almost silent electrical activity during this  crucial  phase of   their  ECG .ST segment is often  a flat line  in them . This is a ECG of a women referred as CAD. She was asymptomatic . Echocardiogram  was normal . She was asked to do  a EST.

This asymptomatic women was refered for ECG opinion

The peculiar thing about T waves  are ,   a 10 mm upright  as well as  5 mm inverted T wave ,  both can be normal. So .  there is no element of surprise  to note absent  T waves  or a flat  T wave  to be called as normal .

The curious case of lost ST segment !

* T waves are recorded when K+ efflux occur rapidly out of cells . Hypokalemia  can be an important cause of flat T waves.

It is still a  mystery to me  why some people inscribe a tall T when  potassium comes out  of cell and  an equal number (Esp women)  record a down ward T wave  for the same event !  I wish  I get an answer  to this  lingering  question from  any of the readers !

Is a flat T wave represent  a T wave in  transition  to become inverted T wave  later ?

Possible .But we  are not sure ! A static T wave is safer than a dynamic T wave .

Final message

Flat ST segment and absent T waves  represent a same spectrum of ECG  findings  which  are  referred to as  non specific ST segment changes in  clinical practice .Generally , they have  little clinical significance.* In our experience we have found , female patients, Anemia  hypothyroidism  are  often associated with flat ST segments  . If CAD is suspected exercise stress test  should be done. Some believe a flat ST segment  is more likely to  result in EST positivity (Not necessarily true positive !)

* Non specific ST/T changes by itself is a  huge topic.  Ideally the term non specific ST /T changes should be avoided , as it  primarily came into vogue  to denote non ischemic ST segment (Still , other pathologies are very much  possible) It is estimated there are about  50 causes for non specific ST/T changes , right from a  benign situation  like deep   respirations , to significant  myocardial disorders. However , it still makes   good clinical sense for a  general practitioner  , to refer to a cardiologist , whenever ST  segment deviates  without any reason .

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