Dr. Zachow - Intro To EKG Flashcards
What does. It mean if the PR. Interval Is prolonged?
That there is most likely AV nodal delay of some sort
What happens to the EKG if that portion of the heart has more muscle?
The magnitude of the voltage will be higher.
Which area on the EKG represents SA node depolarization?
The area just prior to the P wave. The P wave is not SA node depolarization.
How does the parasympathetic nervous system affect the SA node?
So as we know it uses acetylcholine as the NT in the postganglionic neuron. It activates the CM receptor, which is coupled to K+ efflux, which will make the neuron less positive and thus less likely to fire an AP. This will slow down heart rate.
Break down the P wave
When looking at lead II, the upstroke in the P wave is the atrial polarization of the right atrium, the downstroke of the P wave is the atrial depolarization of the left atrium. They are not always equal. If you have hypertrophy one side it will not be an equal hump. Likewise, if you look at lead V-1, the upstroke is the right atrial depolarization, the negative portion is the left atrial depolarization.
What is occurring in the Pr segment?
AV nodal relay/delay. Calcium dependent depolarization. Remember, if this is prolonged then we know we have some sort of relay issue with t he AV node.
What is occurring during the QRS complex?
Ventricular depolarization through the bundle branches, purkinje fibers, and the ventricular myocardium. If we see this area is prolonged, we would suspect some sort of bundle branch block.
What are the three things that allow me to say whether or not someone is in sinus rhythm or not?
1) 1 P or QRS 2) P occurs before QRS 3) regular intervals
What would you see in a primary bundle branch block?
Elongated PR interval
- physiology is that there is delayed conduction through the AV node or bundle of His.
WHat would you see in a secondary bundle branch block?
You would see that some P waves are not conducted. For instance, you frequently see. Two P waves in between a T wave and a QRS wave. The one that is before the QRS is the conducted P wave.
- physiology is that not every atrial impulse is conducted through the AV node, His, purkinje
What would you see in a tertiary (complete) bundle block?
You would see that although the QRS waves might be occurring at regular intervals, and the P waves are occurring at regular intervals, there is no coordination between them. So, QRS might be occurring very frequently, while P waves occur very infrequently.
- physiology is that there is just no coordination between the atrial impulses to the ventricles. Complete autonomy of the atrium and ventricle.
- If the ventricles aren’t receiving input from the atria, then these are called escape rhythms.
- If the SA node no longer works, then the AV junction takes over. If the AV junction no longer works then the ventricular pacemaker takes over, which is very slow and wouldn’t cut it for a normal person.
Pathway of contraction of the heart
SA node - causes contraction of the atria
AV node - once impulse from atrium are received by the AV node there is a delay, but the AV node connects the atrium to the ventricle
Bundle of His –> Bundle branches –> purkinje fibers –> ventricular myocytes
