Transcript Normal Sinus Rhythm

Normal sinus rhythm
Debs Farr
2011
Course Objectives
• To recognize the normal rhythm of the
heart - “Normal Sinus Rhythm.”
• Understand normal conduction of the heart
http://caribbean.scielo.org/img/revistas/wimj/v54n3/a12fig03.jpg
R.E.Mason.,I.Likar ( 1966)
Impulse Conduction & the ECG
Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers
The “PQRST”
• P wave - Atrial
depolarization
• QRS - Ventricular
depolarization
• T wave - Ventricular
repolarization
The PR Interval
Atrial depolarization
+
delay in AV junction
(AV node/Bundle of His)
(delay allows time for
the atria to contract
before the ventricles
contract)
Qt Inteval
• QT – Represents time for both ventricular
Depolarisation and repolarisation.
Pacemakers of the Heart
• SA Node - Dominant pacemaker with an
intrinsic rate of 60 - 100 beats/minute.
• AV Node - Back-up pacemaker with an
intrinsic rate of 40 - 60 beats/minute.
• Ventricular cells - Back-up pacemaker with
an intrinsic rate of 20 - 45 bpm.
The ECG Paper
• Horizontally
– One small box - 0.04 s
– One large box - 0.20 s
• Vertically
– One large box - 0.5 mV
The ECG Paper (cont)
3 sec
3 sec
• Every 3 seconds (15 large boxes) is
marked by a vertical line.
• This helps when calculating the heart rate.
Calibration
Normal Sinus Rhythm
• “Normal sinus rhythm occurs when the
impulse originates in the sino Atrial node
and travels through the conduction system
in a normal sequence ,at a normal and
regular rate”
American Heart
Association,(2000).homepage:Availablehtt
p:/www.americanheart.org/warning.
Normal Sinus Rhythm
ECG Interpretation
• A mystery?
• An enigma?
• Confusing?
• Difficult?
Criteria - P wave
An upright rounded P-wave in leads II, III
and AVF, and an inverted P-Wave in
AVR which precede each QRS
Complex.
• The P wave does not exceed 2.5mm in
height.
• It does not exceed 3mm in width.
• A biphid P wave is seen in lead V1.
Criteria - PR interval
• PR Interval
• 0.12 - 0.20seconds.
• Delay at AV node
»Protect ventricles
»Allow for ventricular filling
Criteria QRS complex
• Should not exceed 0.12 seconds in
duration.
• Should not exceed 27mm in height.
• Sharp narrow complex
• RS in V1, QRS in V6
Criteria T wave
• The deflection produced by repolarisation
of the ventricles.
• No clearly defined range
• General rule - T wave should not be more
than 1/2 the height of the preceding QRS
Criteria - QT interval
• QTc Interval
• Should not exceed 0.42 seconds
(QTc).
• QT interval corrected to the heart
rate.
Correction Calculation
QTc =
interval
measured Qt
 cycle length
Criteria U wave
• The origin is uncertain
• May represent repolarisation if the IVS
• May represent slow conduction of
ventricular myocardium
• Prominent U waves are abnormal
• Usually most visible in V1-V4
Nomenclature - QRS
• The 1st negative deflection - Q
• The 1st positive deflection - R
• The 2nd negative deflection or If a
negative follows a positive - S
Nomenclature -QRS
Nomenclature - QRS
Nomenclature - QRS
• Waves > 0.5mv (5mm) high
• Capital letters e.g. QRS
• Waves < 0.5mv (5mm) high
• Lower case e.g. qrs
Intervals
• P wave duration measured?
• PR interval measured?
• QRS interval measured?
• QT interval measured?
Amplitudes
• P wave height measured?
• QRS height measured?
Segments
• PR segment measured?
• ST segment measured?
Limb leads
• Measurements - lead II
• QRS Axis
• P wave Axis
Chest Leads
• Progression of R waves throughout the
chest leads
• Transitional Zone
• Phases of Activation
Depolarisation Stages
1
2
3
Typical complexes in the Precordial leads
RV
V1
RV
V2
IVS
V3
IVS
LV
V4
V5
LV
V6
Progression of R waves
throughout the chest leads
• Size of the R wave should increase from
V1 to V6.
• V4 Usually at the Apex (Transitional Zone
where the first negative wave appears).
R Wave Progression
Practical Challenges
Sinus Rhythms
• Sinus Bradycardia
• Sinus Tachycardia
• Sinus arrhythmia
NSR Parameters
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Rate
Regularity
P waves
PR interval
QRS duration
QT interval
• U wave
60 - 100 bpm
regular
normal
0.12 - 0.20 s
0.04 - 0.12 s
not exceed 0.42
seconds.
Sinus Bradycardia
- Rate
< 60 b pm
Etiology: SA node is depolarizing slower than normal,
impulse is conducted normally (i.e. normal PR and
QRS interval).
Sinus Tachycardia
- Rate
> 100 bpm
• Etiology: SA node is depolarizing faster than
normal, impulse is conducted normally.
• Remember: sinus tachycardia is a response to
physical or psychological stress, not a primary
arrhythmia.
Sinus arrythmia
• Rate – variable
Etiology: SA node is depolarizing t a variable rate ,
impulse is conducted normally (i.e. normal PR
and QRS interval).
Normal Rhythms !!!
• *Sinus Arrest*
• Considered a ‘Sinus rhythm’ but is
abnormal
Rhythm 1
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Rate?
Regularity?
P waves?
PR interval?
QRS duration?
130 bpm
regular
normal
0.16 s
0.08 s
Interpretation? Sinus Tachycardia
Rhythm 2
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Rate?
Regularity?
P waves?
PR interval?
QRS duration?
30 bpm
regular
normal
0.12 s
0.10 s
Interpretation? Sinus Bradycardia
ECG INTERPRETATION
• If the normal ECG is
known then
interpretation of
abnormals becomes
easier
EASY ?
References/Bibliography
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www.ecglibrary.com
www.acc.org
www.cardionetics.com
www.coheadquarters.com
www.RNCEUS.com
www.tmc.edu/thi/arrhythm.html
ctmed