1. ECG Basics

2. Anatomy of the Heart
Sinus Node (SA node) – the primary pacemaker of the heart;
Atrioventricular Node (AV node) – slows and transmits electrical signal from atria to ventricles.
Bundle of His – rapidly sends electrical signal through ventricles
Right and Left Bundle branches – carry fast electrical signals through the ventricles
Bundle Branches (bundles of Purkinje fibers)

3. Where is the Rate Determined?
SA node – pacemaker of the heart; rate of bpm if SA node fails, then the Atrial foci will pace the heart; rate of bpm If the Atrial foci fail, then the AV node (Junctional foci) will pace the heart, send electrical activity up through the atria and down through the ventricles; rate of bpm If the Junctional foci fail, then the Purkinje fibers (ventricular foci) will pace; rate of bpm

4. Breaking Down an EKG – What It All Means

5. P wave – Atrial Depolarization (atrial contraction)
< 0.11 seconds
PR interval – Time from atria to Purkinje fibers
seconds
QRS complex – Ventricular Depolarization (ventricular contraction)
First negative deflection – Q wave
First Positive deflection – R wave
Negative following the R wave – S wave
0.05 – 0.10 seconds
ST segment – Ventricle remains depolarized
0.04 seconds
T wave – rapid ventricular repolarization
QT interval – repolarization
Ventricular contraction last from Q wave to end of T wave
< 0.42 seconds
U wave – Purkinje fibers repolarization -usually present with post-MI patients
R-R interval – duration of one heart beat

6. What else to consider? What is the heart rate?
Atrial HR – number of P waves
Ventricular HR – number of QRS complexes
Normally – should be equal
Is the rhythm regular or irregular?
Are the R-R interval equally spaced?
Is there a P wave for every QRS?
Yes – sinus rhythm
No – more information needed

7. It’s all about the paper
Each small square is 1 mm tall by 1 mm wide
Time x amplitude
Between two thick black lines is 0.20 seconds, therefore 5 thick line boxes equal 1 minute.
Can use a 6 second strip to calculate rate and rhythm.

8. Let’s Practice! P wave = ________ PR interval = ________
QRS interval = _________
ST segment = ________
T wave = ________
P wave = * PR interval = * QRS interval = * ST segment = * T wave = 0.18

9. More Practice! What is the heart rate?
Is this rhythm regular or irregular?
Is there a P wave for every QRS complex?
Is this a sinus rhythm?
What is the heart rate? 60 bpm * Is this rhythm regular or irregular? Regular * Is there a P wave for every QRS complex? Yes * Is this a sinus rhythm? Yes

10. Strip of the Month