Car 12 - Electrocardiography Flashcards
What are all the leads in the ECG?
There are 12: I. II. III. aVL. aVR. aVF. V1. V2. V3. V4. V5. V6.
What are the unipolar limb leads?
aVR (Heart to right). aVF (heart to feet). aVL (heart to left).
What are the bipolar limb leads?
I (right to left). II (Right to feet). III (Left to feet).
Why would aVR normally report a negative deflection(below the line) of the QRS?
Because normal electrical physiology of the heart starts from the top and goes to the left. Since the aVR (the lead on the right) is going to the right, the electrical deflection is going to be negative since its going to the opposite direction.
Why would aVL normally report a positive deflection(above the line) of the QRS?
Because the aVLeft is going to the same direction as the heart depolarization (center to left). Therefore, it will report a positive deflection.
What would a positive deflection of the aVR be called and why?
It is called a left axis deviation because the aVR normally deflects to the right (below the line).
What five things can cause a left axis deviation on the ECG Axis?
Inferior wall myocardial infarction. Left anterior fascicular block. Left ventricular hypertrophy (sometimes). LBBB. High diaphragm.
What five things can cause right axis deviation on the ECG axis?
Right ventricular hypertrophy. Acute right heart strain (ex. Massive pulmonary embolism). Left posterior fascicular block. RBBB. Dextrocardia.
What deflections would be seen in the limb leads in left axis deviation?
I: +. II: -. III: -. aVR: Neutral or +. aVL:+ . aVF:-.
What deflections would be seen in the limb leads in right axis deviation?
I: -. II: +. III: +. aVR: Neutral or +. aVL:- . aVF:+.
What does a tiny box in an ECG represent?
Horizontally: 0.04 seconds (0.2 secs in one huge box).
What is PR interval and what is the normal length?
The PR is from the beginning of P wave to the beginning of the QRS segment. Normally it is less than 200 msecs (less than one big box).
What is the normal length of the QRS complex?
Less than 120 msecs (around 3 boxes).
What do peaked T waves indicate? What do flattened T waves indicated.
Peaked: High potassium levels. Flattened: low potassium.
How does the cause of a narrow QRS complex differ from the cause of a wide QRS complex?
Narrow QRS: Beat is conducted thru the normal conduction pathway. Wide QRS: Premature ventricular contraction (PVC), Ventricular tachycardia, Bundle branch block.
