Introduction to the ECG Flashcards
What does the P wave correspond to?
Atrial depolarisation
What does the QRS complex correspond to?
How long should it take?
Ventricular depolarisation
Less than 0.12s
What does the T wave correspond to?
Ventricular depolarisation
What does the PR interval correspond to?
How long should it take?
Time from atrial depolarisation to ventricular depolarisation
0.1-0.2s
Which points does the PR interval occur between?
The start of the P wave and the start of the QRS complex (Q)
What does the QT interval correspond to?
Time spent during which ventricles are depolarised
About 0.42s at 60bpm
Which points does the QT interval occur between?
Start of the QRS complex (Q) to the end of the T wave
Which points does the ST segment occur between?
The end of the QRS complex (S) and the start of the T wave
Which points does the PR segment occur between?
The end of the P wave and the start of the QRS complex (Q)
What is the significance of the ST segment?
If elevated in myocardial infarction indicates MI more severe
How is depolarisation represented on an ECG?
Upward going blip
Are fast or slow events transmitted better?
Fast events
What plane are standard limb leads in?
Frontal/vertical
What does SLL 1 represent?
Left arm with respect to right arm (
What does SLL 2 represent?
Left leg with respect to right arm (
What does SLL 3 represent?
Left leg wrt left arm (^I)
Is depolarisation towards a lead positive or negative?
Positive
Is depolarisation away from a lead positive or negative?
Negative
Is repolarisation towards a lead positive or negative?
Negative
Is repolarisation away from a lead positive or negative?
Positive
Why is there a downward going blip towards Q?
The interventricular septum is being depolarised from LEFT to RIGHT so depolarisation is away from the lead.
Why is there an upward going blip towards R?
The bulk of the ventricle is depolarised from endocardium from epicardium from right to left so depolarisation is towards the lead
Why is there a downward going blip towards S
Because the upper ventricular system is depolarised from left to right so depolarisation is away from the lead
Why is the R wave biggest on SLL 2?
Because the main vector is depolarisation is in line with axis recording from the left leg to the right arm
What would left heart hypertrophy or right heart atrophy cause on an ECG?
Right axis deviation
What are augmented limb leads?
Recording from 1 lead with respect to 2 other leads. Giving 3 perspectives and 6 in total of frontal and vertical plane.
What is aVR?
Right arm with respect to left arm and left leg
What is aVL?
Left arm with respect to right arm and right leg
What is aVF?
Left leg with respect to left arm and right arm
What are the precordial chest leads?
What direction to the move in in what plane?
Move from right to left ventricle in transverse plane
How does the direction of the QRS complex change as the precordial chest leads move across the chest?
Negative going blip from V1 but flips to a positive going blip at V3 or V4
How fast does the paper run on the rhythm strip?
25mm/s
What is the calibrating pulse of the rhythm strip?
How does this correspond to boxes?
0.2sec (5mm) = 1 large box
How do you calculate HR from an ECG?
Count the R waves over 30 large squares (6 seconds) and multiply by 10.
List the key points that the rhythm strip tells you
Whether each QRS complex is preceded by a P wave
Whether the PR interval is to short (<0.12s) or long (>0.2sec)
Whether the QRS is too wide (>0.12s)
Whether the QT interval is too long (>0.42s at 60bpm)
