Atrial Fibrillation (AF)
Atrial Fibrillation (AF) is seen a lot in clinical practice, its kind of the common cold of cardiac dysthymias (or it would be if the common cold had the potential to be life threatening....). As such, it's useful for all of us who work in health care to know at least some basics about AF.
As always with ECG's, I would highly recommend learning a little about the pathophysiology of AF before you start working on interpreting it on an ECG.
The Pathophysiology of Atrial Fibrillation
'Over Simplified'
The top chambers (Atria)
An electrical impulse should flow across the heart muscle in an orderly fashion causing the top chambers to squeeze and push blood into the lower chambers (ventricles). In AF, electrical impulses in the atria surge chaotically around causing the muscle to 'shudder' rather than squeeze.
The Bottom Chambers (Ventricles)
Electricity continues to flow through the bottom chambers of the heart in an orderly and organised fashion. However, to get to the bottom chambers it first must pass through the chaos in the top chambers! The net result is that the bottom chambers continue to squeeze, but at irregular intervals as they get inconsistent stimulation from above!
Atrial Fibrillation (pathophysiology and implications for care) made easy!
Consequences!
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As the Atria aren't effectively squeezing blood into the ventricles the effectiveness of the heart as a whole is reduced. This has the potential to reduce blood pressure within the body.
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Blood can end up remaining trapped in the atria for longer (rather than being continually pushed round body). This makes it more likely that it will clot. Many of these clots then travel out of the heart and end up lodged in small blood vessels in the lungs causing blockages (pulmonary embolisms)!
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AF can cause the electrics in the ventricles to become 'over-stimulated' leading them to beat very rapidly (fast AF!). This can result in the ventricles not having enough time to fill with blood between contractions. This can lead to a significant, sometimes life threatening, reduction in blood pressure!
Recognising Atrial Fibrillation
on an ECG
Oversimplified
There are a couple of diagnostic features that make AF fairly easy to identify. A more thorough systematic process for interpreting an ECG is cover in the interpreting a normal sinus rhythm section. Here we'll focus on aspects specific to AF.
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Irregular QRS complex's! A complication of AF is the irregular activation of the ventricles. As the QRS complex's represent the ventricles contracting, we can therefore expect the complex's to be at irregular intervals across the ECG .
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A bumpy wavy line instead of 'p-waves'
Atrial Fibrillation: 5 simple steps for interpretation (made easy with animation)
A typical 'p-wave' represents the contraction of the atria. In AF this doesn't happen! Instead the atria 'fibrillate' or 'shake'. These irregular and disorganised contractions lead to an irregular bumpy line instead of regular p-waves.
* Always remember to get an ECG reviewed by some one competent in interpretation before making a diagnosis!