Exam #2: EKG Flashcards
What do waves represent?
Atrial and ventricular depolarization and repolarization
What does a positive deflection represent?
Depolarization
What does a negative deflection represent?
Repolarization
What does the P wave represent?
Depolarization of both atria
What does the PR interval represent?
Atrial depolarization + AV node delay
What does the PR segment represent?
AV node delay
What does the QRS complex represent?
Depolarization of both ventricles
What does the ST segment represent?
Ventricle contraction and emptying (plateau phase)
What does the T wave represent?
Repolarization of both ventricles
What does the QT interval represent?
Ventricular AP (depolarization AND repolarization)
What does the TP interval represent?
Time between end of T wave and start of next P wave – ventricles relaxing and filling
What does the PP internal represent?
Atria to atria
What does the RR internal represent?
Ventricle to ventricle
What might an inverted T wave represent?
LV hypertrophy
What might a peaked T wave represent?
Hyperkalemia
What might a flat T wave represent?
Hypokalemia
For what two events are there no waves?
- Atrial repolarization
- SA or AV node depolarization
What component of the EKG is very dependent on heart rate? What would cause a shortened QT interval?
QT interval
- Inverse relationship, so a shortened QT interval is due to an increased heart rate (more contractions)
What does one small box on the x-axis represent? What does one large box on the x-axis represent?
Small: 1 mm = 0.04 seconds of time
Large: 5 mm = 0.20 seconds of time
- 5 large boxes = 1 second
How do you calculate heart rate using EKG measurements?
Rate (bpm) = beats per 6 seconds x 10
- 6 seconds = 30 large boxes
What are the three causes of LAD?
- LV hypertrophy
- Obesity
- Pregnancy
What are the three causes of RAD?
- RV hypertrophy
- LV infarct
- Tall, thin body type
What does a first degree AV block mean? Electrically, what is this due to?
Prolonged PR interval greater than 200 ms
- Due to slowed conduction through AV node/Bundle of His
What does a second degree AV block mean? Electrically, what is this due to?
Not every P wave is followed by a QRS complex
- Partial dissociation of atria and ventricles
What does a third degree AV block mean? Electrically, what is this due to?
P and QRS act independent of one another
- Complete dissociation of atria and ventricles with no conduction through the AV node
