From The Book

Question 1

Depolarization occurs after the QRS segment and during the ST segment.
QT >450ms is elongated and predisposes to VT
QT VARIES WITH HEART RATE

Answer 1

The ECG must be properly calibrated to 1mv .

1mv moves the stylus 2 large squares or 1cm and is shown at the beginning of the trace

Question 2

What is a lead?

Answer 2

Is an electrical picture of the heart.

Question 3

The ECG is made up of 12 views of the heart:
6 limb leads
6 chest leads

Answer 3

Limb leads look at the heart from vertical plane
1,2, VL: left lateral surface of the heart
3, VF: inferior surface
VR: right atrium

Chest leads look at the heart from a horizontal plane, front and left side
V1-2: right atrium
V3-4: septum and ant wall of LV
V5-6: ant and lat wall of LV

Question 4

The cardiac rhythms is identified from which lead?

Answer 4

The one that shows the P wave the most clearly. USUALLY LEAD 2

Question 5

What is a rhythm strip?

Answer 5

A single lead electrical activity recorded to show the cardiac rhythm. No diagnosis can be made from this.

Question 6

Upward deflection when depolarization wave is moving toward electrode
Downward deflection when depolarization wave is moving away from electrode

Answer 6

When depolarization wave is moving at right angle to the lead the R and S waves are equal size.

Question 7

Depolarization wave normally moves from 11 to 5pm position essentially away from VR (atrium) towards lead 2 (left lat ventricle)

The direction of depolarization is called cardiac axis
Can be worked out from QRS in leads 1,2,3, with predominantly upward deflection greater in lead 2

Answer 7

RV hypertrophy causes axis to shift to the right because the cardiac activity of RV will take dominance over LV

Causes for right shift are:
Pulmonary
Congenital heart disorders e.g tetralogy of fallow