Download Electrocardiogram Analysis

ELECTROCARDIOGRAPH
ANALYSIS
Reported by:
AGNES Purwidyantri
BIOMEDICAL ENGINEERING DEPT
ECG interpretation - step-by-step
•
•
•
•
•
•
•
•
•
Rate
Rhythm
Cardiac Axis
P – wave
PR - interval
QRS Complex
ST Segment
QT interval (T & U wave)
Other ECG signs
ELEMENTS OF ECG
Cardiac
Electrophysiology
• Electrical activity is
governed by multiple
transmembrane ion
conductance changes
• 3 types of cardiac cells
– 1. Pacemaker cells- SA
node, AV node
– 2. Specialised conducting
tissue – (Purkinjee Fibers)
– 3. Cardiac myocytes
Pacemakers of
Heart
•SA Node - Dominant
pacemaker -intrinsic rate
of 60 - 100 beats/minute.
•AV Node - 40 - 60
beats/minute.
•Ventricular cells - 20 - 45
beats/minute.
S Allen 2003
The Normal Conduction System
Electrocardiogram
• Is a recording of electrical activity of heart conducted
through ions in body to surface
13-60
EKG Distributions
•
•
•
•
•
•
Anteroseptal: V1, V2, V3, V4
Anterior: V1–V4
Anterolateral: V4–V6, I, aVL
Lateral: I and aVL
Inferior: II, III, and aVF
Inferolateral: II, III, aVF, and V5
and V6
Rate
•
•
•
•
HR of 60-100 per minute is normal
HR > 100 = tachycardia
HR < 60 = bradycardia
Rule of 300- Divide 300 by the number of boxes
between each QRS = rate
Number of Rate
big boxes
1
300
2
150
3
100
4
75
5
60
6
50
Differential Diagnosis of Tachycardia
Tachycardia Narrow Complex
ST
Regular
Irregular
SVT
Atrial flutter
A-fib
A-flutter w/
variable conduction
MAT
Wide Complex
ST w/ aberrancy
SVT w/ aberrancy
VT
A-fib w/ aberrancy
A-fib w/ WPW
VT
What is the heart rate?
www.uptodate.com
(300 / 6) = 50 bpm
Rhythm
• Sinus
– Originating from SA
node
– P wave before
every QRS
– P wave in same
direction as QRS
What is this rhythm?
Normal sinus rhythm
Normal Intervals
• PR
– 0.20 sec (less than one
large box)
• QRS
– 0.08 – 0.10 sec (1-2 small
boxes)
• QT
– 450 ms in men, 460 ms in
women
– Based on sex / heart rate
– Half the R-R interval with
normal HR
Waveforms & Intervals
P Wave
Depolarization of both atria
• Relationship b/w P & QRS distinguish various arrhythmias
• Shape & duration of P - indicate
atrial enlargement
PR INTERVAL
Onset of P wave to onset of QRS
• Normal = 0.12 - 2.0 sec
• Represents A to V conduction time (via His
bundle)
• Prolonged PR interval indicate AV block
Short PR Interval
•WPW Sx
Accessory pathway (Bundle of Kent) - early activation
of the ventricle (delta wave & short PR interval)
Long PR Interval
• 1st degree Heart Block
Ventricular Depolarization
Includes
• Bundle of His
• Bundle Branches
– Right
– Left
• Septal
• Anterior
• Posterior
• Terminal Purkinjie fibers
What is the axis?
Normal- QRS up in I and aVF
Hypertrophy
 Add the larger S wave of V1 or V2 in mm, to
the larger R wave of V5 or V6.
 Sum is > 35mm = LVH
Ischemia
• Usually indicated by ST changes
– Elevation = Acute infarction
– Depression = Ischemia
• Can manifest as T wave changes
• Remote ischemia shown by q waves
Lead Placement
aVF
All Limb Leads
Precordial Leads
QRS COMPLEX
Ventricular depolarization
• Is > P wave d/t > Ventricular mass
• Normal duration = 0.08 - 0.12 secs
Q wave >1/3 the height of R wave, >0.04 sec –
abnormal; may represent MI
ST Segment
• Connects QRS complex & T wave
• Duration = 0.08 - 0.12 sec
T Wave
–“small to moderate” size +ve deflection wave after
QRS complex,
–Ht is 1/3rd - 2/3rd that of corresponding R wave
U Wave
–Septal repolarization (not always seen on ECG)
QT Interval
•Beginning of QRS to end of T wave
• Normal QT is usually about 0.40 sec
• QT varies based on HR- faster HR ,shorter QT .
•Hence QTc.
Bazett’s formula: QTC = QT / √ RR
Fredericia’s formula: QTC = QT / RR 1/3
Framingham formula: QTC = QT + 0.154 (1 – RR)
Hodges formula: QTC = QT + 1.75 (HR– 60)
CALCULATING RATE
Eg
Rate = 300
3
or
Rate = 100 beats/minute
Rate =
1500
15
CALCULATING RATE
Rhythm irregular- # of beats in a 6-sec X by 10
1
2
3
4
5
6
7
8
There are 8 waves in this 6-seconds strip.
Rate
= (Number of waves in 6-sec strips) x 10
= 8 x 10
= 80 bpm
References
• The EKG made easy-John R. Hampton
• An Introduction to Electrocardiography – Leo
Schamroth
• Marriot’s Practical Electrocardiography.
• www.ambulancetechnicianstudy.co.uk
• www.learntheheart.com