Transcript ECG Interpretation

ECG Interpretation
What is an ECG
• Electrocardiogram
• Traces the electrical activity of the heart
• 12 lead, 15 lead
Uses of ECG Tracing
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Ischemia/infarct
Arrhythmias
Ventricular and atrial enlargements
Conduction defects
Pericarditis
Effects of some drugs and electrolytes
ECG
How to Conduct an ECG
1.
2.
3.
4.
5.
Patient lies flat on back
Electrodes are placed on
the body
Sites may need to be
shaved or cleaned to
ensure the leads will stick
properly.
Patient will lie as still as
possible, hold breath, or
put hands under bottom to
keep from moving.
The results are then
printed out on paper for
MD to review.
ECG Strip
Lead Placements
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V1 - Junction of the 4th ICS, Right sternal border
V2 - Junction of the 4th ICS, Left sternal border
V3 - Midway between V2 and V4
V4 - Junction of 5th ICS, Mid clavicle
V5 - Anterior aspect of axilla, same line as V4
V6 - Mid axilla, same line a V4
4 limb leads (for grounding etc)
Lead Placements Cont’
Normal Conduction Pattern
Understanding the Waves
Each wave
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P
Q
R
S
T
ECG Strip r/t heart
Understanding the Waves
• One small box = 0.04 seconds
• One large box = 0.2 seconds
• 5 large boxes = 1 second
http://en.wikipedia.org/wiki/File:ECG_principle_slow.gif
Understanding the Waves
• Baseline (what is it?)
• P wave
– Length of time it takes the impulse to pass from
the SA node to the AV node
– Should precede every QRS wave
• PR interval
– Should be no longer than 0.12 – 0.2
Understanding the Waves
• QRS
– Should be no longer than 0.12
– If energy is going towards a positive electrode
(camera), the picture will show a positive QRS complex
– If energy is going away from positive electrode, the
picture will show a negative QRS complex
– If energy is toward the positive electrode and then
passes by it, the QRS will be biphasic
– Ventricle contracting
Understanding the Waves
• T wave
– Should always start from baseline
– Will indicate ischemia
Understanding an ECG
•
Is as easy as…
1.
2.
3.
1. = rate
2. = intervals
3. = rhythm
Step 1 = Rate
• Different ways to calculate a rate:
– a) ECG usually tells you
– b) Locate a QRS that is close to a big line and
count to next big line: 300, 150, 100, 75, 60, 50
– c) take a 6 second strip, count QRS and
multiply by 10 (hint: the middle of V3 on the
lead II strip is 6 seconds)
Step 1 = Rate (cont’)
• Checking the regularity:
– map out QRS’s
Step 2 = Intervals
• We assess intervals to see where the
impulse is coming from (pacemaker beat)
• Remember:
– PR interval: normal is 0.12 - 0.2
– QRS interval: normal is less than or equal to
0.12
Step 3 = Rhythm
The biggest question in relation to rhythm
is…
Is this rhythm affecting
my patient?
(Normal) Sinus Rhythm
• 60-80 bpm
• P preceding each QRS
• Normal intervals
Normal ECG
Other Sinus Rhythms
• Sinus bradycardia
– a sinus rhythm with a rate <60 bpm
Other Sinus Rhythms
• Sinus tachycardia
– a sinus rhythm with a rate >80 bpm
Atrial Arrhythmias
• Atrial fibrillation (A-fib)
– irregular rate
– no discernable P waves
– increased risk of strokes due to clots that might
form due to fibrillation (patients are usually on
anticoagulation therapy)
Atrial fibrillation
Atrial Arrhythmias Cont’
• Atrial flutter
– saw tooth in appearance
– irregular rate
Atrial flutter
Blocks
• 1st degree AV block
– a PR interval that exceeds 0.20 sec
Blocks Cont’
• 2nd degree AV block (Mobitz)
– a) type I (Wenckebach)
• longer and longer PR intervals until a QRS is dropped
Blocks Cont’
– b) type II
• P waves and then suddenly a QRS is dropped
• P’s are regular
Blocks Cont’
• 3rd degree AV block
– HR <40 bpm
– a complete block of electrical activity from
atria to ventricle
– P’s are regular
Ventricular Rhythms
• Ventricular fibrillation
– complete breakdown of all rhythm
– a) course
– b) fine
V-fib
• What’s the first thing to do when coming up
on a patient with this rhythm?
Ventricular Rhythms Cont’
• Ventricular tachycardia (V-tach)
– impulse originates in the ventricle
– always has a wide QRS complex
V-tach
What’s the first thing to do when
coming up on a patient with this rhythm?
Asystole
• Pulseless
Coronary Arteries
MI’s
MI’s
MI’s
• How can you tell on an ECG that your
patient is having a heart attack?
• T waves
• Different views of heart will show different
injured areas of heart
MI’s
• T wave shouldering is classic
MI’s
• How else can you tell that your patient has
had an MI?
• Cardiac Markers
– CK will show in 4-6 hours (starts to come back
down after 1 day)
– Troponin will show in 4-6 hours (may stay
elevated for weeks)
– Others are: LDH, CK-MB, myoglobin, AST
Locating an MI
Area
Leads
Artery
Complications
Inferior
II, III, aVF
Right
coronary
Bradycardia
Anterior
V1, V2, V3, Left anterior Pulm edema,
V4
descending hypotensive
Lateral
I, aVL, V5,
V6
Circumflex
I Lateral (circumflex)
aVR
V1 Anterior (Lt ant desc)
V4 Anterior
II Inferior (Rt coronary)
aVL Lateral
V2 Anterior
V5 Lateral
III Inferior
aVF Inferior
V3 Anterior
V6 Lateral
ECG Tissue Damage Locations
Where is this MI?