LECTURE 2 (ECG) Flashcards
What is an Electrocardiogram (ECG)?
A measurement of the electrical activity of the heat during the cardiac cycle and can be used to identify if there are any issues with the normal functioning of the heart
Why might you need an electrocardiogram?
- To look out for the cause of chest pain
- To evaluate problems which might be heart related
- To identify irregular heartbeats
- Before surgery + after myocardial infarction
- To determine how well certain heart medicines are working
- To determine baseline
Where are V1-V6 placed?
- V1 = 4th intercostal space on the right sternum
- V2 = 4th intercostal space at the left sternum
- V3 = Midway between V2 and V4
- V4 = 5th intercostal space at midclavicular line
- V5 = Anterior axillary line on the same horizontal level as V4
- V6 = Mid-axillary line on the same horizontal level as V4 and V5
Where are the Limb leads placed?
- RA (Right arm) = anywhere between right shoulder and right elbow
- RL (Right leg) = anywhere below the right torso and above the right ankle
- LA (Left arm) = anywhere between the left shoulder and left elbow
- LL (Left leg) = anywhere below the left torso and above the left ankle
What are the parts of the cardiac conduction system?
- Sinoatrial (SA) node
- Atrioventricular (AV) node
- Bundle of his
- Bundle branches
- Purkinje fibers
What is the P wave?
The first deflection and indicated atrial depolarisation
What is the QRS complex?
Followed the P wave and represents ventricular depolarisation and contraction
What is the T wave?
Represents ventricular depolarisation
What is the U wave?
Indicates the recovery of the Purkinje conduction fibers
What is the eight-step procedure for interpreting ECGs?
- Rhythm
- Rate
- P wave
- PR Interval
- QRS Interval
- T wave
- QT Interval
- ST segment
What do you need to examine ventricular and atrial rhythms?
Ventricular rhythms = R to R intervals
Atrial rhythms = P to P intervals
What is Asystole?
When there is no electricity or movement in your heart
How do you determine heart rate from ECG?
METHOD 1
1) Count the number of QRS complexes over a 6-second interval
2) Multiply by 10 to determine heart rate
METHOD 2
1) Count the number of small boxes for a typical R-R interval
2) Divide 1500 by this number to determine HR
What is the difference between Sinus Tachycardia and Sinus Bradycardia?
Sinus tachycardia = A heart rate greater than 100 bpm that originated from the sinus node
Sinus bradycardia = A heart rate less than 60 bpm and originates from the sinus node
What are the properties of a normal P wave?
- Atrial depolarisation
- Generated by SA node and conducted across atria
- +ve in leads aVL, avF, I, V4-V6 and -ve in aVR
- Normal duration is 0.06-0.12 seconds
