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Posts Tagged ‘ddd vs vvi pacing’

We have been taught right from first year cardiology residency  how to trouble shoot a pacemaker .It has been a real complex thing for us. Now looking  back ,all the troubles we took to understand seems to be redundant.Here is a summary of my thought process on the issue. It can be approached  with reference  to time, symptoms and ECG features.  With due respects to all those brainy hardworking   EP experts  , I have taken few academic liberties!

pacemaker trouble shooting

Timing

  • Within 24 hours -100% technical or procedural Issues , like lead dislodgement/Screws and nuts.
  • Within 1-2 week – Again technical , Pocket issues , Infections.
  • Within 6 months – Benign pacemaker syndrome ,Threshold settings, Scars
  • After  first year – Generally Issues are rare , Lead issues , Associate disease progression.
  • Beyond 8-10  years /Near end of life – 95% Energy depletion leads issues .( Please note , pacemakers do not stop all of a sudden it has a intrinsic end of life indicators .We have to look for it. May be ,we can expect a  warning siren in the future ? )

Symptoms

  • Vague dizziness – Pacemaker syndrome ? Anxiety ?
  • Near syncope – Show some concern (For many , Impending true syncope is a non existent entity )
  • True syncope  – Real emergency*

* Syncope can be unrelated to pacemaker but always consider  them electrical  unless proved otherwise . Few patients  may continue to have significant symptoms  in-spite of   normal pacemaker parameters. This would  mean , the original symptom for which  pacemaker was put is not related to the Brady-arrhythmia .It could   suggest alternative hemodynamic explanation  like vaso-depressive component of vagal syncope ,autonomic dysfunction , orthostatic intolerance or  a coexisting neurological /systemic condition.

**Never forget syncope is not an exclusive symptom of bradycardia .A new onset  tachycardia  , which is either a part of  brady- tachy syndrome or separate arrhythmia can continue to provoke the symptom.

Gross ECG findings

Bradycardia /Often implies back to original rhythm –  Indicates real trouble . Since ,in a paced patient HR cannot be less than programmed rate of 70.

Tachycardia -No spike.( Not to worry ?) A common  situation if the original indication was  sinus node dysfunction . Many of them are  in own sinus rhythm or AF . Just ensure spikes reappear when the rate falls below 70 . If the rate never goes down , what to do ? Try a carotid massage or observe a nocturnal ECG  or call analyst and increase the rate to document pacing . (In DDD mode we have a rare PM mediated re-entrant tachycardia , which is mainly used to grill cardiology fellows in their board exams with all those PVARP stuff !)

Simple pauses – Any pause more than the pacing interval is a definite concern .

Spikes more than QRS  – Indicate capture failure.

No spikes (Can be so benign  to ultimate danger )

  • No spikes , but  excellent own rhythm – Good  functional  SA node
  • Regular  spikes ,but intermittent own rhythm or only random spikes with good own rhythm – Needs bedside hairsplitting and  EP assistance !
  • “No spikes -No Own rhythm” -Most dangerous .Sudden lead issues or hyper sensing .(Emergency  switch off  by magnet  application before inserting temporary pacing advised )

* Anatomical issues like lead dislodgement , fracture , compression ,  perforation are to be ruled out in every pateitn with intermittent capture or failure .This is done by combinations of imaging as well physiological assessment.Dislodgement must be visualized .The term micro dislodgement may not exist.

Other Investigations

  • X ray
  • Echo for any new structural lesion (RA,RV dilatation , TR RV clots or vegetation )
  • Holter
  • Event monitors ,Loop recorders.

Pacemaker analysis

  • Battery life ( Very important parameter .Usually around 10 -12 years.Unexpected early drain can occur.)
  • Threshold (Most failure to capture associated with high threshold Note :Threshold will be normal in battery depletion Acute threshold can increase marginally .Should be reasonable other wise battery will drain.New protocols like auto capture and managed pacing will help optimal threshold
  • Impedance – Normal in battery depletion , dislodgement and exit block,  Increased in lead fracture and loose screws.Decreased or lost in insulation failure.

Management

The principle of management are simple. Few logical questions ,

  • Is the pacemaker generator is alive and has has enough energy ?
  • Are the  leads okay ?
  • The problem is in the settings ? can it be rectifies by the programmer
  • Or should we replace the pacemaker ?

Technical jargon like  under sensing , over sensing or no sensing  , fusion beats , micro dis-lodgement  etc are important for  academic reasons . We may talk any thing , realistically , what  the ventricle want  is a non stop heart beat  every second or so !

Emergency

Bradycardia – Insert a temporary pacemaker /Call the analyst  /Inform the  electrophysiologist /Senior cardiologists /(Please realise ,  some fellows  can be better than the personnel mentioned above in tackling emergencies !)

Tachycardia : Native or machine induced ?

Native – Mostly safe ,  Ignore  or treat with drugs.

Machine induced :(very rare) Switch of the pacemaker . No off switch available as in a mobile phone ? *What to do ? if unclear about the  whereabouts  tachycardia origin . If hemodynamically unstable no harm in shocking .Nothing will happen .Call the EP  guys on hot line and decide.

Elective symptom guided.

  • Asymptomatic -Normal ECG : Reassure and send home.
  • Vague symptoms   -Do Holter and Observe
  • Syncope -Normal ECG needs extensive all system investigation.
  • Syncope -With pauses /Bradycardia /Asystole  – Ironically ,decision  making is easier. Temporary pacing is the  ultimate savior. Later , check the lead,  generator .One may need to change  either one or both of of them.

** While the above principles apply  for both single  and dual chamber pacemakers , the later doubles our thinking burden . While atrial tracking is a great technological advancement , what to  do with those sensed event can be really  tricky .The response of  ventricles and the AV intervals  can be tentative at times. Cross talks from unexpected atrial and ventricular arrhythmia can occur.  Further , mechanical atrial lead  issues are far  more common . When confronted with recurrent atrial lead related  problems , one  simple solution is  silently convert the mode to  single chamber VVI mode.

Final message

Pacemaker trouble shooting appears complex at the first look .It’s all common sense.Thinking with simple state of mind and  being clear about the intended  goal is vital. Electrical intricacies are tough to understand  but most situations do not require them. However ,If the initial indication was for complete heart block one has  to be very alert.

Principles of medicine argue us to make an exact diagnosis before treating . But,realise  this is rarely  possible or even desirable in emergency .Curiously , most pacemaker troubles can be solved successfully without making a proper trouble shoot !

If  we can summarize in one line  , a prompt emergency  back up temporary pacemaker insertion  is key to  management most of the serious  pacemaker related problems.It ,not only tackles the emergency ,  buys time till we decode the real problem . . .  if we wish to !

Related article.

Role of magnet application in pacemaker trouble shoot

 

 

 

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