ECG2 Flashcards
What is the clinical relevance of ECG?
- Conduction abnormalities
-
structural abnormalities
- perfusion abnormalities
What are the advantages of using ECGs?
- cheaper
- easy to under take
- reproducible between people and centres
- quick turn around on results
What are leads in ECGS?
representation of electrical activity from a specific heart perspectic
What are cardiac vectors?
Represented by an arrow in the net direction of movement, size reflecting the magnitude
What does the steepness of the line denote?
The velocity
What are downward deflections towards?
Negative electrode
What does the isoelectric line represent?
no change in net voltage i.e vectors are perpendicular to lead
What does the width of the deflection show?
duration of event
What are upward deflections towards?
the positive electrode
Unipolar vs bipolar?
Number of physical electrodes
How are ECGs reported?
- rate and rhythm
- P-wave and PR interval
- QRS duration
- QRS axis
- ST segment
and cardiac axis
How is lead II positioned?
From Right Arm to Left Leg
Right arm being the negative electrode and left leg being the positive electrode
Why on a typical ECG is QRS wave an upwards deflection? (Lead II)
Because it represents electrical stimulation travelling through purkinje fibres towards apex ( downwards towards positive electrode ) = positive deflection
Where is lead I positioned?
Negative E = right arm
Positive E = left arm
Where is lead III positioned?
Negative E = Left arm
Positive E = left leg
Where is the aVR psotioned?
- augmented vector right (unipolar)
Negative E = n/a
Positive E = right wrist
Where is the aVL positioned?
- augmented vector left (unipolar)
Positive E = left wrist
Where is the aVF positioned?
- augmented vector foot
Positive electrode = Left foot
What is the rhythm strip on an ECG?
Lead II along the bottom for comparison
How many chest electrodes are there?
6
Where is V1 electrode placed?
Right sternal border
In the 4th intercostal space
Where is V2 electrode placed?
Left sternal border
In the 4th intercostal space
Where is V3 electrode placed?
Halfway between V2 and V4
Where is V4 electrode placed?
Mid-clavicular line
In the 5th intercostal space
