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ECG Basics: Atrial Fibrillation With Rapid Ventricular Response

Dawn's picture
Wed, 06/05/2013 - 22:46 -- Dawn

This is a good basic rhythm strip example of atrial fibrillation with a rapid ventricular response showing the identifying characteristics of atrial fibrillation:  no P waves, an irregularly-irregular rhythm, and a "fibrillatory" baseline.  The wavy baseline will not be seen in all leads in all patients, so it is best to use the first two findings as diagnostic criteria.  Atrial fib often appears initially as a rapid rhythm, as the AV node is being bombarded by many impulses from multiple foci (pacemakers) in the atria.  Depending upon the AV node's ability to transmit these impulses,however, we could see a slow, normal, or rapid ventricular response. 

Atrial fib has very chaotic depolarization of the atrial muscle, resulting in quivering and ineffective pumping of the atria.  This loss of "atrial kick" can severely reduce ventricular filling, and can reduce cardiac output by as much as 25%.  In patients with a very rapid rate, cardiac output can be further reduced, causing CHF.  In addition, the fibrillating atria can form blood clots due to sluggish movement of blood.  These clots can embolize and cause stroke.  For these reasons, patients with atrial fib are anticoagulated and sometimes the atrial fib is stopped by medical, surgical, or electrical therapy.  Recurrence of atrial fib is common after treatment, and for some patients, control of the ventricular rate and anticoagulation become the preferred treatment.

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Comments

ekgpress@mac.com's picture

     Even when the interpreter KNOWS the specific rhythm in question - it is best to approach each arrhythmia by: i) Assessing whether the patient is hemodynamicallly stable enough to allow you the luxury of time to fully assess the rhythm; and ii) Systematic description of what you see along the way toward specifying your diagnosis.

  • We are not told if this patient is stable. We'll assume he/she is ...
  • The rhythm is rapid and irregular. The QRS in this single monitoring lead appears to be narrow - and - there are no definite P waves. This defines the rhythm as AFib (Atrial Fibrillation) - here with a rapid ventricular response.
  • The rate of this rhythm is fast. How fast becomes important given that IF one ever sees AFib with an exceedingly rapid ventricular response (ie, >220-250/minute) - it then becomes likely that the patient has WPW. Treatment of very rapid AFib with WPW is very different from treatment of AFib using the normal AV nodal pathways. Use of the usual AV nodal slowing drugs (verapamil; diltiazem; beta-blockers; digoxin) is contraindicated with WPW - because these agents preferentially facilitate antegrade conduction down the AP (Accessory Pathway) - which may result in deterioration of the rhythm to VFib.
  • We estimate the rate of the AFib seen here at ~180/minute. We count a total of 18 beats within the two 3-second periods (arrows) - and given 60 seconds/minute - this leads to a rate of 18 X 10 = 180/minute.
  • Dawn alludes to a number of clinical points regarding evaluation and management of AFib. For those interested - Please check out this PDF that summarizes Key Aspects of AFib (taken from my ACLS-2013-Arrhythmias-Expanded Version book).

 

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

CardioLimassol's picture

In fact there is evidence that patients who are reverted back to sinus rhythm either chemically or electrically are more likely to have a stroke due to discontinuation of anticoagulation. Cardioversion is more nessecary for symptomatic relief or in the very early stages of developping a.fib which makes it more liklely to sustain sinus rhythm.

Dr Stasinos Theodorou

MB ChB, MRCP(UK)

Interventional Cardiologist

www.cardiolimassol.com

ekgpress@mac.com's picture

     GREAT point by Dr. Theodorou! The AFFIRM Trial showed in effect that it didn't matter re longterm risk of stroke whether patients were converted to sinus rhythm or remained in AFib - as the underlying risk of stroke was similar in both groups. Several potential reasons might explain why:

  1. There is something about "being" in AFib that increases risk - and that something doesn't change even if you get the patient out of AFib ...
  2. Holter monitoring studies suggest that the overwhelming majority (>90%) of AFib episodes in patients with PAF (= Paroxysmal AFib = intermittent AFib) are "silent", with the patient totally unaware that they are in AFib. As medical providers - we tend not to appreciate this, because patients present because of symptoms - but most of the time when they go back-and-forth (in- and out- ) of AFib - they do not know it. This makes it highly problematic to try and follow patients longitudinally. Perhaps the reason why longterm risk of stroke seemingly is unaffected by whether one is converted out of the rhythm or not is that MANY of these patients actually continue to go in- and out- of AFib without being aware (and risk of stroke seems highest if clot has formed when you go back into sinus rhythm - and may then "pump out" the stroke into the peripheral circulation ... ).

     As implied by Dr. Theodorou - the hope is that IF you address AFib when it first presents (before anatomic and physiologic changes have become established in the atria) - that you have the best chance of restoring AND maintaining sinus rhythm (and perhaps also of minimizing longterm risk of stroke).

  • BOTTOM Line: Longterm anticoagulation may be needed in a patient who has been in AFib regardless of whether the rhythm persists - continues to be intermittent - or perhaps, even if ultimately converted to sinus rhythm ....

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

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