Let’s take a closer look at atrial fibrillation.
There are three main types of atrial fibrillation.
Paroxysmal: which describes transient episodes that stop on their own, and may last anywhere
from seconds or minutes, to hours and up to a week.
The next is persistent atrial fibrillation, and that defines episodes which last more
than a week; or episodes lasting less than a week and are only stopped by either pharmacological
or electrical cardioversion.
The last one is something called “Long-Standing Persistent Atrial Fibrillation” which is
a type of persistent a-fib that lasts longer than one year.
This was formerly known more as chronic or permanent atrial fibrillation.
The nature of atrial fibrillation is where multiple electrical impulses are being generated
in the atria at the same time and therefore cause chaotic myocardial responses which may
diminish the pre-load and effectiveness of the cardiac contraction.
That may also cause the development of micro emboli due to the stagnant blood flow from
the atria, and in some cases, this leads to a rapid ventricular response secondary to
a re-entry problem.
The electrical pattern will have no discernable P-waves but instead, show a fibrillatory wave
between each QRS complex.
Now, because there’s a lack of coordinated electrical impulses generated from the atria
traveling through the AV node and to the ventricles, the result is an irregular ventricular response
which also occurs irregularly.
So now, using that whole system we just talked about, let’s break down the ECG of atrial
fibrillation.
First, let’s look at the rhythm: Is the rhythm regular or irregular?
No, the rhythm is irregularly irregular.
Next, let’s look at rate.
Well,what is the rate?
In this case the rate is still 80 beats per minute.
We ask ourselves, is the rate normal, fast or slow?
The rate is variable because of its irregularity.
Then we evaluate the P-wave: Are they present?
Nope, not in this case.
The P-waves are not present.
Do they occur regularly?
No, because there are no P-waves.
Is there one P-wave for each QRS complex?
No, the answer is that there is no P-wave for each QRS complex.
Are the P-Waves smooth, rounded, and upright?
Again, no.
Only fibrillatory waves are seen.
So in this case, if we were to ask, do all the P-waves have similar shapes?
Again, we would have to say no.
So now we want to know what the PR interval is for this ECG.
Does the PR interval fall within the normal 0.12-0.20 seconds?
Not at all, because there isn’t a PR interval.
Is the PR interval constant?
Again, this doesn’t apply because there isn’t a P-wave.
So next we move on to the QRS complex of the ECG.
Is the QRS interval less than 0.12 seconds?
Yes.
The QRS is within normal range.
Is the QRS wide or narrow?
Well in this case, the QRS is still narrow.
Are the QRS complexes similar in appearance?
Here we can see that each one does look similar.
Now, here’s my cardiac interpretation based on this ECG.
It appears that this patient has atrial fibrillation.
The causes can be many but the following are some of the most common underlying reasons.
Conjestive heart failure patients or those with a previous history where the patient
may have damage to the SA node, the patient has a conduction system dysfunction from a
current or past myocardial infarction or has experienced a traumatic injury.
The patient has a disease process, maybe used or uses harmful drugs or has a metabolic disorder.
Common side effects from atrial fibrillation include but are not limited to, a higher risk
for coronary, cerebral or pulmonary embolism and as a result of the increased potential
for microemboli to develop secondary to the lack of circulation of blood from the atria.
Another complication discussed above is the rapid ventricular response due to the atrial
fibrillation which can accelerate the ventricular rate to above 100 beats per minute.
Atrial fibrillation combined with higher ventricular rates may decrease the amount of blood ejected
from the heart due to the lack of what is sometimes referred to as the preloading atrial
kick.