Dawn's picture

Atrial fibrillation with a controlled ventricular response is often considered to be atrial fib that has been controlled with medication.  While this is often true, it is possible to see atrial fib with a ventricular rate between 50 and 100 bpm in a patient who has not been treated.  The hallmark signs of atrial fib are:  no P waves and irregularly-irregular rhythm.

Multiple, simultaneous leads are advised to be sure there are no P waves, and a long rhythm strip is often needed to prove the irregularly-irregular rhythm.  Remember, even though this rate is adequate (about 90 bpm), the loss of P waves means no "atrial kick".  The atria are not filling the ventricles with a forceful pumping action. Patients can lose a significant percentage - up to 25% - of their cardiac output because of this.  Coupled with the risk of stroke from the formation and embolization of blood clots from the sluggish circulation in the atria, it is much preferable to have sinus rhythm at the same rate.

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ekgpress@mac.com's picture

Full description of AFib is incomplete without reference to the ventricular response. AFib is either:

  • Rapid (ie, usually over 120-130/minute).
  • Controlled (between ~ 70-110/minute).
  • Slow (under 50-60/minute).

As per Dawn - the example of AFib shown here is with a controlled ventricular response - as determined by the presence of R-R intervals between ~ 3-to-4.5 large boxes in duration.

  • By far - the most common ventricular response to new AFib is rapid. As a result - slowing the rate of new-onset AFib is a primary goal of initial treatment.
  • The presence of new AFib with a slow ventricular response should prompt the clinician to rule out: i) drug effect; ii) hypothyroidism; and/or iii) recent ischemia or an event (infarct). IF none of these 3 causes is operative and the patient is "older" - then the diagnosis of new slow AFib is SSS (Sick Sinus Syndrome).

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

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