វិធីសាស្ត្របកប្រែECG យ៉ាងលឿន

Rapid ECG Interpretation lectured by Dr. Matt Strehlow and translated by Mr. Somontha Koy in Seminar on Essential Medicine Care Cambodia (SEECC) in May 2012, organized by URC in collaboration with Stanford Emergency International, USA, supported by USAID.
Objectives
• Discuss a systematic approach to ECG evaluation
• Identify critical findings on ECG
o Ventricular rhythms
o Complete heart blocks
o ST elevation
o New left bundle branch block
Cardiac Electrical Conduction Pathways
• Electrical activity initiates in the SA node (primary pacemaker of the heart)
• Through the atria to the AV node
• Pauses in AV node and then into the ventricles via the Right and Left Bundles.
Components of the ECG
• P wave - depolarization of atria
• QRS - depolarization of ventricles
• T wave - repolarization of ventricles
Anatomic Lead Groupings
• When evaluating for ischemia/infarction you should look at the anatomic
lead groups (which leads go together)
• Inferior Leads – II, III, AVF
• Anterior Leads – V1, V2, V3, V4
• Lateral Leads – V5, V6
• High Lateral Leads – I, AVL
Systematic Approach to Basic ECG Interpretation
• Rate
• Rhythm
• QRS
• ST segments & T wavs
Determining the Heart Rate
• Rule of 300 – number of large boxes between QRS complexes divided by the
counted number
o Use for regular rhythms only.
Rhythm Determination
• Questions used to determine the rhythm
1. QRS wide or narrow?
2. Regular or irregular?
3. P waves present?
4. P waves before every QRS?
5. P wave from the sinus node?
• Notes on determining the rhythm
o Ventricular tachycardia is greater than 120bpm
o Atrial fibrillation is the cause of most narrow complex, irregular
rhythms.
o If a QRS does not follow every p wave, a heart block is likely
present.
• Heart Blocks
o Slow or blocked conduction from the atria to the ventricle
o Second and third degree heart blocks can be life threatening and
cardiology consultation is recommended
§ First degree
• Prolonged PR interval
§ Second degree
• Type 1 (Weinchebach) - gradually increasing PR
interval until a beat (QRS) is dropped
• Type 2 - randomly dropped beat
§ Third degree
• Complete heart block
Wide QRS
• Can be a sign of a life threatening condition
• 6 Causes of a Wide QRS
o Ventricular rhythm
o Bundle branch block
o Paced rhythm
o Electrolyte abnormality (High K+)
o Drugs (TCAs)
o Wolfe Parkinson White (WPW)
Bundle Branch Blocks (BBB)
• Terminal portion (last part) of the QRS
• V1 Positive Deflection - RBBB
• V6 or I Positive Deflection - LBBB
Q Waves
• Small Q waves (less than1mm height and less than 1mm width) may be normal in leads
o V5 or V6
o Inferior leads (II, III, AVF)
• Q waves are always abnormal in leads
o V1, V2, and V3
ST Segment Elevation and Depression
• Measure ST segment elevation or depression from the J point to the level
of the T-P segment
• J point is where there is a sudden change in the slope of the QRS
complex.
• 8 Causes of ST Elevation
o Acute myocardial infarction
o Benign early repolarization
o Bundle branch block
o Brugada syndrome
o Prinzmetal’s angina (vasospasm)
o Pericarditis
o Left ventricular aneurysm
o Left ventricular hypertrophy
• 8 Causes of ST Depression
o Myocardial ischemia/infarct
o Reciprocal changes
o Ventricular strain
o Bundle branch blocks
o Digitalis effect
o Hyperkalemia
o Hypokalemia
T Waves
• Deep, symmetric T wave inversion suggests ischemia
• Tall, peaked T waves are concerning for
o Early infarction
o Hyperkalemia
Summary
• Use a systematic approach when reading ECGs
o Rate
o Rhythm
o QRS
o ST segments and T waves
• Focus on critical findings
QRS Axis
Note: If the QRS is predominantly positive in I and II then it is a normal QRS axis.
P Waves
• Peaked p waves = cor pulmonale (right HF), enlarged right atrium suggestive
of right heart failure
• Wide, large p waves are a sign of an enlarged left atrium likely due to left
heart failure