Exercise 2 Introduction to electrocardiography heart rate and rhythm

What is an electrocardiogram?

A graph of the changes in voltage that occur within heart muscle during different phases of the cardiac cycle.

What does cardiac impulse originate from?

The Pacemaker (SA node)

Where does repolarization start?

Repolarization starts at the apex of the ventricles

What does the P wave represent?

Atrial depolarization

What does the QRS represent?

Ventricular depolarization

What does the t wave represent?

Ventricular repolarization

What is the term used to describe an abnormal rate, shape pattern, or absence of a wave?

Arrhythmia or dysrhythmia

What are the methods to determine heart rate from a ecg?

• 300…150…100 method

• R-R interval

• 6-second method

• 3-second method

• Ruler method

When can you use the 6 second method?

This method can be used with an irregular rhythm to estimate the rate

How many seconds does the yellow square represent

0.04 seconds (1mm)

How many seconds does the yellow square represent?

0.1 seconds

What is the time that is represented on the big square

0.2 seconds

For every 15 large squares what interval do you have?

3 second interval

How do you find the bpm in a 6 second strip

Count the number of R waves in a 6 second strip and multiply is by 10

How do you find the bpm using the R-R method?

Count the number of small squares between 2 consecutive QRS complexes and multiply by 0.04. then divide by 60

How do you find the heart rate using the 300-150-100 method

1. find the R wave that falls on the vertical line

2. count off the dark vertical lines between the r wave and the next one as 300,150,100,75,60,50

Each cardiac cycle is represented by what?

A period of systole and diastole.

How long is the PR interval

0.12-0.20 seconds

How long is the QRS interval

0.11 second or less

Is voltage measured on the horizontal or vertical line?

Vertical line