4: ECG theory and practice Flashcards
Electrical activity within and between cardiac mycocytes causes current ___.
flow
How do electrical impulses travel between cardiac myocytes?
Gap junctions
The electrocardio___ records the electrocardio___.
graph , gram
What is a dipole?
A charge separation between areas of different charge (e.g in the heart)
The measured potential difference is greatest when the lead is ___ to the direction of the dipole (electrical vector).
parallel
The measured potential difference is zero when the lead is ___ to the dipole (electrical vector).
perpendicular
Depolarisation moving towards the +ve electrode in an ECG lead gives…
upward deflection
Depolarisation moving away from the +ve electrode in an ECG lead gives…
downward deflection
Repolarisation moving towards the +ve electrode in an ECG lead gives…
downward deflection
Repolarisation moving away from the +ve electrode in an ECG lead gives…
upward deflection
How many electrodes are used in a standard ECG?
10
How many leads does a standard ECG have?
12
Where is the V1 chest electrode placed?
Right sternal edge, 4th intercostal space
Where is the V2 chest electrode placed?
Left sternal edge, 4th intercostal space
Where is the V4 chest electrode placed?
Mid-clavicular line, 5th intercostal space
i.e the apex
Where is the V3 chest lead placed?
In between V2 and V4
Where is the V5 chest electrode placed?
Anterior axillary line, same horizontal line as V4
Where is the V6 chest electrode placed?
Mid-axillary line, same horizontal line as V4
Which interval on an ECG represents systole?
ST segment
Which interval on an ECG represents diastole?
TP segment
How would you calculate heart rate using the squares on ECG paper?
Heart rate = 300 / number of large squares in RR interval
What is the ECG rhythm strip?
Prolonged recording of one lead (usually Lead II)
Allows you to detect rhythm disturbances
What type of disease does ST segment / T wave changes indicate?
Ischaemic heart disease
What can voltage criteria changes be used to diagnose?
Chamber hypertrophy
What is the first key step when analysing an ECG?
Verify patient details: name and date of birth
After verifying a patient’s name and DOB, what else should be checked on an ECG?
Date and time ECG was taken
What should you check before trying to determine heart rate / voltage criteria from an ECG?
The calibration of the ECG paper
When working out heart rhythm from an ECG rhythm strip, you should ask yourself seven questions - what are they?
- Is electrical activity present?
- Is the rhythm regular or irregular?
- What is the heart rate?
- P-waves present?
- What is the PR interval?
- Is each P-wave followed by a QRS complex?
- Is the QRS duration normal?
Name three diseases which a normal ECG wouldn’t exclude.
Myocardial infarction
Intermittent rhythm disturbance
Stable angina
