Electrocardiograms Flashcards
What are the frontal plane 6 limb leads and angles?
Inferior leads:
Lead II 60o
Lead III 120o
aVF 90o
Left Lateral Leads:
Lead I 0o
aVL -30o
Right Lateral Lead:
aVR -150o
Which leads belong to the following groups: Anterior Left lateral Inferior Right ventricular
Anterior: V2, V3, V4
Left lateral: I, aVL, V5, V6
Inferior: II, III, aVF
Right ventricular: V1, aVR
Normal T-wave amplitude
1/3 - 2/3 of corresponding R wave
Normal QRS Interval
0.06-0.10 seconds (less than 1/2 a big box)
Normal PR interval
0.12-0.2 seconds (less than one box)
Difference between interval and segment
Segments do not include bumps, intervals include at least one bump (QRS Interval)
Relationship between T wave and R wave
One is repolarization and the other is depolarization. Since repolarization is the opposite direction and opposite change in ions as depolarization, on leads with a positive R wave, expect a positive T wave.
Which interval includes all the ventricular electrical activity
QT interval
What percentage of an R-R interval is a QT interval?
40%
R-R interval is a cardiac cycle
Differentiate between hypertrophy and enlargement of the heart
Hypertrophy: enlargement of muscle mass. Usually from increased after load (more power needed to overcome resistance).
i.e. hypertension or aortic stenosis
Enlargement: aka dilatation; corresponds to a specific chamber. Usually from increased preload (a chamber grows to accommodate more volume).
i.e. valvular disease (mitral insufficiency may cause left atrial enlargement)
3 changes in hypertrophy/enlargement
- Increase in duration
- Increase in amplitude
- Change in electrical axis
If QRS axIs is normal, which 2 leads can you check are important to be positive
Lead 1 and aVF
It is normal for QRS axis to be between 0-90o
8 Steps to reading an ECG
- Rate
- Rhythm
- Axis
- P - wave
- P-R segment
- QRS - width
- QT interval
- T - wave inversions
- STEMI
