Health knowledge made personal
Join this community!
› Share page:
Go
Search posts:

Can premature beats (Ectopic beats) occur in SA node ? Yes, it can . It’s called sinus premature systole.

Posted Apr 14 2009 11:50pm

Ectopic beats or premature depolarisations are the commonest  cardiac arrhythmia encountered . Human heart , is a  non stop  electro mechanical organ ,  and it is not surprising   ectopic beats are so common  and can literally originate  from every cell of heart. But , generally it   emanates  primarily from  the special conducting cells . At times  ,  even  other cells (Myocytes, interstitial cells )  can generate abnormal electrical potential.These ectopic electrical potentials  can be compared  to  electrical load shedding when there is excess electrical strain .

Vast  majority of ectopic are benign  in human population. When this occurs ,  in the milieu of underlying heart disease or during ischemic  episodes they become clinically important and initiate a sustained arrhythmia.

Classically and traditionally ectopic beats are described in the

A. Ventricle:      Ventricular premature beats, (VPD)

B. Atrium:             Atrial premature beats(APD)

C. AV junction: Junctional premature beats.(JPD)

If you note , one important structure is missing from the list.

Yes , it is  SA node.  Can it result in premature depolarisation ?

When do you suspect a SPD(Sinus premature depolarisation)

  • It manifests a  an sudden unexpected , sinus beat exactly as the previous sinus beat. Followed by a pause.
  • The P wave morphology exactly is similar to prior p wave.
  • Many times we miss this entity as we tend to over  diagnose APD than SPD.
  • SPDs tend to occur in bigeminy rhythm.

Differential diagnosis

  • Sinus arrhythmia and pause
  • APD
  • SA node echo beats (Part of SA node reentry)
  • SA blocks

How do differentiate  a sinus arrhythmia from sinus premature depolarisation (SPD ) ?

Sinus arrhythmia occurs in a baseline bradycardia environment.

It does not not come as   “on -off ” pattern . It has a gradual onset offset dynamics.

Clinical significance

This is a clinically unimportant arrhythmia* .This  is probably the reason , it is not a popular concept .

*But it can confound in the diagnosis of  , other important rhythm  disorders.it could be a expression of  sinus node dysfunction and a precursor of  inappropriate  sinus tachycardia The significance could be substantial in atrial triggered  based  pace maker rhythm

Final message

When you confront an unexpected , early , sinus beat not accountable to sinus  arrhythmia  or APD

suspect SPD.It is  not rare , it is a  grossly under diagnosed entity.

Reference

Sinus premature systole  http://www.chestjournal.org/content/64/1/111.full.pdf?ck=nck

Post a comment
Write a comment:

Related Searches