CVS 13: Understanding the ECG Flashcards
What are ECGs used to distinguish?
- Tachyarrhythmia/ Bradyarrhythmia
- Myocardial infarction/ ischaemia
- Cardiomyopathy
- Assessment of pacing
- Electrolyte disturbances
Which plane are the limb leads?
The FRONTAL plane
What are the limb leads used for? Which lead acts as the ground?
- Measure the potential difference between the limbs
- Right leg= neutral/ ground electrode
How is the aVR derived?
The average between the left arm and left leg (-ve) to the right arm (+ve)
How is the aVL derived?
The average between the right arm and left leg (-ve) to the left arm (+ve)
How is the aVF derived?
Average between the right arm and left arm (-ve) to the left leg (+ve)
What does one small 1mm x 1mm block represent?
0.04s (40ms) and 0.1mV amplitude
What are the angles for the 3 main leads?
Lead 1: 0 degrees
Lead 2: 60 degrees
Lead 3: 120 degrees
What are the angles for the three augmented leads?
aVF: 90 degrees
aVL: -30 degrees
aVR: 210 degrees
What is the QRS axis? What is it’s normal range?
The main direction of ventricular depolarisation.
-30 to + 90 degrees (aVL to aVF)
Which pole do the chest leads V1- V6 form?
The positive cathode
Which pole is formed by the negative pole?
Wilson’s central terminal (a composite pole of the right arm, left arm and left leg = average potential of body)
Which two precordial leads give information on the septum?
V1 and V2
Which two precordial leads tie information about the anterior aspect?
V3 and V4
Which two precordial leads give information about the lateral aspect?
V5 and V6
