ECG interpretation Flashcards
What’s the normal adult heart rate?
60-100 bpm
How do you calculate the heart rhythm on an ECG if it is regular?
count the number of large squares present within one R-R interval, then divide 300 by this number
How do you calculate the heart rhythm on an ECG if it is irregular?
count the number of complexes on the rhythm strip, and then multiply this number by 6 to give you the average number of complexes in 1 minute
what are the 2 types of heart rhythm an individual can display?
regularly irregular or irregularly irregular
how can you see if the heart rhythm is regular or irregular?
mark out several consecutive R-R intervals on a piece of paper, then move them along the rhythm strip to check in the subsequent intervals are similar
what is a good tip to do if you are suspicious of an AV block?
map out the atrial rate and the ventricular rhythm separately, as you move along the rhythm strip you can see if the PR interval changes, if QRS complexes are missing or if there is complete dissociation between the two
what is the cardiac axis?
the overall direction of electrical spread within the heart
what is the cardiac axis in a healthy individual?
11 o’clock to 5 o’clock
what are the typical ECG findings for normal cardiac axis?
lead II has the most positive deflection compared to leads I and III
what are the typical ECG findings for right axis deviation?
lead III has the most positive deflection and lead I should be negative
what is right axis deviation associated with?
right ventricular hypertrophy
what are the typical ECG findings for left axis deviation?
lead I has the most positive deflection, leads II and III are negative
what has left axis deviation associated with?
heart conduction abnormalities
what are the 4 steps you should take when looking at the P waves?
- are the p waves present?
- is the p wave followed by a QRS complex?
- do the p waves look normal? - duration, direction and shape
- if the p waves are absent, is there any atrial activity
what would absent p waves and an irregular rhythm indicate a diagnosis of?
atrial fibrillation
How long should the PR interval be?
between 120-200ms (3-5 small squares)
how many milliseconds is a small square?
40ms, 0.4 s
what does a prolonged PR interval suggest?
A PR interval >0.2s suggests the presence of a atrioventricular delay (AV block)
What would be seen on an ECG with a first-degree heart block?
A fixed prolonged PR interval >200 ms
what would you see on an ECG with a second-degree heart block (type 1)?
Progressive prolongation of the PR interval until eventually the atrial impulse is not conducted and the QRS complex is dropped. This repeats
what would you see on an ECG with a second-degree heart block (type 2)?
a consistent PR interval duration with intermittently dropped QRS complexes due to the failure of conduction, typically repeating cycle of every 3rd (3:1) or 4th (4:1) P wave