Download File - Barbara Jones, BSN

ECG Basics
Anatomy of the
Heart
1. Sinus Node (SA node) – the primary
pacemaker of the heart;
2. Atrioventricular Node (AV node) –
slows and transmits electrical signal
from atria to ventricles.
3. Bundle of His – rapidly sends
electrical signal through ventricles
4. Right and Left Bundle branches –
carry fast electrical signals through
the ventricles
5. Bundle Branches (bundles of
Purkinje fibers)
Where is the Rate Determined?
SA node – pacemaker of the heart; rate of 60- 100 bpm
if SA node fails, then the Atrial foci will pace the
heart; rate of 60-80 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 40-60
bpm
If the Junctional foci fail, then the
Purkinje fibers (ventricular foci)
will pace; rate of 20-40 bpm
Breaking Down an EKG –
What It All Means
• P wave – Atrial Depolarization (atrial
contraction)
•
< 0.11 seconds
• PR interval – Time from atria to Purkinje fibers
•
0.12 - 0.20 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
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
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.
Let’s Practice!
 P wave = ________
 PR interval = ________
 QRS interval = _________
 ST segment = ________
 T wave = ________
P wave = 0.10 * PR interval = 0.16 * QRS interval = 0.04 * ST segment = 0.14 * T wave = 0.18
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
 Is there a P wave for every QRS complex?
 Is this a sinus rhythm?
 Is this rhythm regular or irregular?
 What is the heart rate?
More Practice!
Strip of the Month