Dawn's picture
Submitted by Dawn on Fri, 09/27/2013 - 13:20

This is a rhythm strip from a NIPS procedure (non-invasive programmed stimulaltion), which is a programming test for an implantable cardioverter defibrillator (ICD).  The test is done under light anesthesia, similar to that used for colonoscopy.   In this example, the patient is in normal sinus rhythm at the beginning of the procedure.  The pacemaker technician overdrives the patient's rate to observe the pacing function, then a stimulus is delivered to cause ventricular fibrillation (V Fib).  Initially, the ventricular rhythm is somewhat organized and coarse (V flutter), but it will rapidly deteriorate if not corrected.  Before it deteriorates, the ICD delivers a shock, and the patient's rhythm is restored.  In this example, bi-ventricular pacing was conducted for a few minutes before the patient resumed NSR.  The patient is then recovered from the anesthesia and discharged home.

For your students, this is a good example of the relative safety of shocking the well-perfused heart.  Although it is possible to put the heart into an intractable V Fib with this test, the ICD usually is able to convert the potentially lethal rhythm easily.  It is a good reminder that we need to perfuse the heart well before performing defibrillation on a person with unwitnessed cardiac arrest.

Related Terms: 
ECG Basics
Rhythm strip
NIPS Procedure
ICD Test
Pacemaker
Cardioversion
Defibrillation
Ventricular fibrillation
VF
Paced rhythm
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ekgpress@mac.com's picture

Submitted by [email protected] on Sun, 09/29/2013 - 12:07

    NICE rhythm strip example of monitored VFib under controlled conditions allowing prompt defibrillation that restores the patient's normal rhythm. This illustrative tracing brings up the issue of Immediate vs Delayed Shock for VFib?

  • Delayed defibrillation of VFib may not work ... It may even be deleterious - by reducing the chance that defibrillation will successfully convert the VFib rhythm. The obvious difficulty lies with determining HOW MUCH DELAY becomes too long for recommending defibrillation as the immediate initial action when VFib is found on EMS arrival.
  • 2005 Guidelines favored delaying defibrillation - IF it was likely that more than 4-5 minutes had passed since onset of cardiac arrest. More recent studies are inconclusive about benefit or not from defibrillating prior to CPR for VFib present more than 4-5 minutes.
  • New Guidelines in the ACLS Provider Manual now allow the option to immediately shock VFib of uncertain duration without a preceding period of CPR.
  • Witnessed VFib should be promptly shocked (as soon as an AED/defibrillator is available).
  • Assuming time until arrival is not excessive - many (if not most) hospital providers routinely shock newly-discovered VFib as soon as they are able to do so.
  • Data are inconclusive for the optimal approach to unwitnessed VFib that occurs out-of-hospital. Current ACLS Guidelines allow for performance of 1.5-to-3 minutes of BLS (~5 cycles of 30:2 CPR) before the 1st shock is given. Alternatively (our preference) - it may be most practical to perform CPR for a brief period just until the defibrillator is ready for shock delivery!

The above excerpted from ACLS-2013-Arrhythmias Expanded Version.

Ken Grauer, MD  www.kg-ekgpress.com   [email protected] 

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