ECG Flashcards
Abnormalities in which leads shows patholgy in which areas of the heart?
What are the individual leads of an ECG measuring?
During the cardiac cycle different regions of the heart are depolarized, or polarized, creating a charge separation, or dipole. The dipole generates an electrical field (lines of isopotential) that are measurable with the two electrodes.
What determines the magnitude of the electrical dipole?
Tthe mass of cardiac muscle that is involved in the generation of the signal (Ventricles make a bigger signal that the atria)
What determines the direction of the electrical dipole?
Determined by the overall activity of the heart any instant in time and varies during the cardiac cycle
Is the positive limb electrode the recording or the reference electrode?
Recording
Is the negative limb electrode the recording or the reference electrode?
Reference
At which angle does each of the limb leads look at the heart?
- Lead I looks at the heart at 0 degrees (3 o’clock) - Lead II looks at the heart at +60 degrees (5 o’clock) - Lead III looks at the heart at 120 degrees (7 o’clock)
**Einthoven’s Triangle
Formed by the 3 limb leads, which ensure no area of the heart is undetected
Which part of the cardiac cycle is represented by the PR interval?
AV nodal delay between atrial and ventricular contraction
Which part of the cardiac cycle is represented by the TP interval?
Diastole
**Goldberger’s method
In augmented limb leads, - uses one electrode as the recording electrode (+ve), but uses two others as the reference electrodes (-ve
Electrical Axis of the Heart
Mean direction of the action potentials traveling through the ventricles during ventricular activation (depolarization).
What is normal axis deviation and what does it look like on an ECG?
QRS axis between -30 and +90 degrees On ECG: Both leads I and II are pointing up
What is left axis deviation and what does it look like on an ECG?
QRS axis less than -30 degrees On ECG: Lead I is pointing up and II is pointing down (‘leaving’ each other)
What is right axis deviation and what does it look like on an ECG?
QRS axis more than +90 degrees On ECG: Lead I is pointing down and Lead II is pointing up (‘reaching’ for each other)
How long is a normal PR interval (AV nodal delay) on ECG?
0.12-0.2 secs (3-5 small squares)
How long is a normal P wave on ECG?
0.08-0.1 secs
What is the standard speed of ECG paper?
25 mm/sec
What time length does one small ECG box represent?
0.04secs
What time length does one large ECG box represent?
0.2secs
How many large boxes are there in a second and a minute on ECG?
5 in a second and 300 in a minute
How do you determine heart rate on ECG?
300/number of large boxes between beats or 300/numer of large boxes between R-R interval
How many leads are the and how many wires are there for ECG?
12 leads but only 10 wires. - Wires = connect the electrodes to the ECG machine Leads = the imaginary lines between the electrodes
What steps would you go through when approaching an ECG?
- Verify patient details: name and DOB
- Check date and time in which ECG was taken
- Check the calibration of the ECG paper
- Look at the rhythm strip
* a. Is electrical activity present?
* b. Is the rhythm regular or irregular? Spaces between the QRS complexes are uniform
* c. What is the heart rate? (300/number of large squares/number of QRS in 30 large x10)
* d. P-waves present?
* e. What is the PR interval?
* f. Is each P-Wave followed by a QRS complex?
* g. Is the QRS duration normal?
- Look at the rhythm strip
- Look at individual leads for voltage criteria changes or any ST or T wave changes
