ECG Flashcards
What are the steps of evaluating an ECG?
Step 1 - Heart rate
Step 2 - Heart rhythm
Step 3 - Cardiac axis
Step 4 - P-waves
Step 5 - PR interval
Step 6 - QRS complex
Step 7 - ST segment
Step 8 - T waves
How is heart rate calculated on an ECG?
Regular rhythm - 300/number of large boxes between subsequent R waves
Irregular rhythm - The number of QRS complexes along entire rhythm strip, then multiply the number by 6
How can the heart rhythm be assessed on an ECG?
Mark off several R-R intervals on a piece of paper and check if they match up along the rhythm strip
How is cardiac axis assessed on an ECG?
Use the limb leads I, II, III
The lead with the most positive blip on the ECG indicates the direction in which the heart is depolarising strongest
How are P-waves assessed on an ECG?
1 - Check that they are present along the rhythm strip
2 - Check the width of the P waves
3 - Checl the general appearance of the P waves (saw tooth etc.)
4 - Is each P wave followed by a QRS complex
How is the PR interval assessed on ECG’s?
A PR interval which is prolonged and does not change throughout the rhythm strip = 1st degree heart block
A PR interval which gets progressively longer until a QRS complex is dropped = Mobitz Type I 2nd degree heart block
A PR interval which is fixed but there are dropped beats = Mobitz Type II 2nd degree heart block
P waves and QRS waves are completely unrelated = 3rd degree heart block
How is the QRS complex assessed on ECG’s?
Width (should be less than 3 small boxes)
Height
Morphology
How is the ST segment assessed on an ECG?
ST segment = part of ECG between end of S wave and start of T wave
In health it should neither be elevated or depressed in relation to the isoelectric line
ST elevation = > 1 small square elevation in 2 more contiguous leads and indicates MI
ST depression = Myocardial ischaemia
How are T waves assessed on an ECG?
Tall T waves
Inverted T waves
Biphasic T waves
Flattened T waves
