Cardiac Rhythm Interpretation

depolarization

transmission of the electrical impulse that achieves a contraction of the heart

repolarization

heart relaxes + prepares to receive the next electrical impulse

P Wave

atrial depolarization

PR interval

related to the rate of cardiac impulse transmitted from the AV node 

QRS Complex

ventricular depolarization

ST segment

follows ventricular depolarization + occurs prior to the start of ventricular repolarization 

T wave

ventricular repolarization is occuring

QT Interval

time for ventricular repolarization is complete

Normal Sinus Rhythm

normal conduction of the cardiac electrical

1. SA node

2. AV node

3. Bundle of HIS

4. R+L bundle branches

5. Purkinje fibers 

Sinus Bradycardia

Occurs when SA node sends an electrical impulse slower than 60bom 

Sinus Tachycardia

Occurs when SA node sends a faster electrical impulse greater than 100 bpm

Premature Ventricular Contractions (PVCs)

occur when early electrical impulses, originating from irritated ventricular cells are transmitted before the next normal impulse is expected from the SA node

Premature Atrial Contractions

occur when irritated atrial tissue fires an early electrical impulse before the next normal impulse is expected from the SA node

causing the heart’s electrical conduction system to activate an early heartbeat or impulse from one of the two atrial chambers 

First Degree Heart Block

occurs when cardiac conduction system is delayed in transmitting an electrical signal through the right atrium to the AV node, resulting in a PR interval greater than 0.20 seconds 

Atrial Fibrillation

occurs when the SA node is not firing appropriately

• electrical impulses are rapid, chaotic, and irregular

• blood clots can form 

Atrial Flutter

occurs when the atria are beating in a regular rhythm + increased rate

• caused by multiple rapid electrical impulses being sent from the atrial too quickly for the AV node to process before the transmission to the ventricles 

Supraventricular Tachycardia 

originates in AV node and can cause excessive excitability of the atrial tissue resulting in an increased HR

• occurs abruptly and suddenly ends without warning