Electrocardiography Flashcards
What does the p wave of an ECG represent?
The conduction of current down atria and internodal pathways
What does the QRS complex of an ECG represent?
Rapid conduction through the left and right bundles -> purkinje fibres -> ventricular contraction
What does the T wave on the ECG represent?
The cardiac muscle relaxing and membrane potential recover/repolarises
What is meant by axis deviation?
Change in heart position or change in the position of electrical condition through the heart
What is the name of the triangle which the ECG leads are placed in on the heart?
Einthovens triangle
Why is lead II the most accurate for following an ECG trace?
Most accurate as lead two measures the conduction through the heart at an angle of 60 degrees, which is the direction of the current from the SA node to the bundle of his and purkinje fibres
What pattern will be seen on an ECG if a patient has atrial fibrillation?
Loss of p wave
What pattern is seen on the ECG if a patient presents with atrial flutter?
Saw tooth pattern
What part of the ECG does a conduction block affect?
The PR interval
What happens to the PR interval when a patient has a conduction block?
Conduction block causes the PR interval to be increased significantly
How do you calculate the heart rate from an ECG?
300/number of large squares between the top of the QRS complexes
How to calculate from an ECG how long the PR interval is?
5 x number of small squares
How to calculate from an ECG how long the QRS interval is?
2.5 x the number of small squares
What is the angle of the heart for Right Axis Deviation?
Between 90 and 180
What angle is the heart at for Left Axis Deviation to occur at?
Between 0 and -90
