EKG Interpretation in 3 Easy Steps: An Overview – Part 3

In our part 3 of EKG rhythm interpretation, you will get a quick rundown on the anatomy of the heart and how a typical rhythm malfunctions, progressing to the different types of heart rhythm abnormalities.

The Heart Set-Up

First, we go to the basics – the anatomical parts of the heart mainly involved in transmitting impulses.

  1. Left and right atriums and the left and right ventricles – functioning as the pumping stations of the heart
  2. Tricuspid and bicuspid valves – separates the upper and lower chambers of the heart
  3. Septum – found in between the left and right heart chambers of the heart
  4. SA node and AV node – electrical conductors
  5. Intranodular/Internodal tracts – also known as Bachmann’s bundle
  6. Bundle of His – responsible for transmitting impulses coming from the atrioventricular node to the heart ventricles
  7. Bundle of branches – transmits cardiac activity from the Bundle of His to the Purkinje fibers
  8. Purkinje fibers – responsible for ventricular contraction or the squeezing of the ventricles

The abovementioned parts of the heart are how you expect the heart to function and react. By the way, the SA node has 60 to 100bpm while the AV node has 40 to 60bpm. So, that’s how the heart routinely works.

Heart Rhythm Abnormalities

We have broken down the heart into three parts to give you a clearer view of the irregularities that happens in each section.

  1. Atrium

Here, you have your atrial fibrillation and your atrial flutter. Here’s how you can easily distinguish the two:

  • Atrial Fibrillation. Here, the faulty SA nodes fire rapidly all over the place, kind of like a Fourth of July in your heart or like a machine gun that shoots electrical charges all over the right atrium. Thankfully, the AV node is there to keep the pulses from getting into the ventricles. The AV node serves as your border control that blocks all the erratic and unnecessary impulses to enter the ventricles.

Impulses created by atrial fibrillation: 350 – 650bpm

How it looks at an EKG strip: “Fibbing out” with no P waves

  • Atrial Flutter. This irregularity can be compared to someone lighting up a box of fireworks and have left it inside the left and right atriums; affecting the pacemaker cells. Compared to atrial fibrillation, atrial flutter acts succinctly showing up as saw-tooth figures on an EKG strip. You can think of this as someone sawing wood, then woodchips and wood shavings flutter off in different directions.

Impulses created by atrial fibrillation: 250 – 350bpm

How it looks at an EKG strip: Saw-tooth with intervals of normal QRS waves

  1. AV Node

In your AV node, you have the bundle branch blocks (BBB) which basically refers to the bundle branches extending from the Bundle of His (looks like viper fangs); one of two branches can be blocked for whatever reason. In the BBB, you can have:

  • Right bundle branch block
  • Left bundle branch block
  • 1st-degree block
  • 2nd-degree block
  • 3rd-degree block (deadliest among the three degrees)

That’s just an overview. Detailed discussions of these bundle branch blocks are available in other lectures.

  1. Ventricles

It is in the ventricles where the two deadliest rhythms are occurring – ventricular fibrillation (V-Fib) and ventricular tachycardia (V-Tach). In hindsight, the ventricles squeeze or contract to provide oxygen to the body; the left ventricle pushes the afterload (blood) into to the body through the aorta.

Therefore, if the ventricle is not squeezing, you’re basically suffocating yourself; also known as ventricular flutter. Clients who present with ventricular fibrillation and ventricular tachycardia will have an altered level of consciousness. What do clients manifest?

  1. The alert and oriented is zero, so clients are usually unresponsive.
  2. If they are awake, they will feel extremely lightheaded due to decreased oxygen perfusion.
  3. They will be very anxious and disoriented.

To address the urgency of V-Fib and V-Tach, healthcare practitioners usually result to:

  1. Shock administrations with chest compressions
  2. Pharmacological drugs (i.e., epinephrine) that realigns your ventricular rhythms to normal rhythms

So that’s just an overview of what happens in the heart if in case it goes out of hand. Now, for our next lesson, we’ll be having a comprehensive discussion about atrial fibrillation and atrial flutter.