Tutorial in ECG Dr. Chew Keng Sheng Emergency Medicine Universiti Sains Malaysia http://emergencymedic.blogspot.com

The Basics Standard calibration 25 mm/s 0.1 mV/mm Electrical impulse that travels towards the electrode produces an upright (“positive”) deflection relative to the isoelectric baseline

Standard calibration

25 mm/s

0.1 mV/mm

Electrical impulse that travels towards the electrode produces an upright (“positive”) deflection relative to the isoelectric baseline

Vertical and horizontal perspective of the ECG Leads Leads Anatomical II, III, aVF Inferior surface of heart V1 to V4 Anterior surface of heart I, aVL, V5, and V6 Lateral surface of heart V1 and aVR Right atrium

Location of MI and Affected Coronary Arteries Location of MI Affected Artery Lateral Left circumflex Anterior LAD Septum LAD Inferior RCA Posterior RCA Right Ventricle RCA

Right Sided & Posterior Chest Leads

Sinus Rhythm The P wave is upright in leads I and II Each P wave is usually followed by a Q The heart rate is 60­99 beats/min

The P wave is upright in leads I and II

Each P wave is usually followed by a Q

The heart rate is 60­99 beats/min

Normal Sinus Rhythm

Instant Recognition of Axis Deviation

Cardiac Axis Normal Axis Right Axis deviation Left Axis Deviation Lead I Positive  Negative  Positive  Lead II Positive  Positive  Negative  Lead III Positive Positive Negative

Calculating Cardiac Axis

P wave Always positive in lead I and II in NSR Always negative in lead aVR in NSR < 3 small squares in duration < 2.5 small squares in amplitude Commonly biphasic in lead V1 Best seen in leads II

Always positive in lead I and II in NSR

Always negative in lead aVR in NSR

< 3 small squares in duration

< 2.5 small squares in amplitude

Commonly biphasic in lead V1

Best seen in leads II

Right Atrial Enlargement Tall (> 2.5 mm), pointed P waves (P pulmonale

Tall (> 2.5 mm), pointed P waves (P pulmonale

Left Atrial Enlargement Prominent terminal P negativity (biphasic) in lead V1 (i.e., &quot;P-terminal force&quot;) duration >0.04s, depth >1 mm

Prominent terminal P negativity (biphasic) in lead V1 (i.e., &quot;P-terminal force&quot;) duration >0.04s, depth >1 mm

Notched/bifid (‘M’ shaped) P wave (P ‘mitrale’) in limb leads with the inter-peak duration > 0.04s (1 mm) Left Atrial Enlargement

Notched/bifid (‘M’ shaped) P wave (P ‘mitrale’) in limb leads with the inter-peak duration > 0.04s (1 mm)

P Pulmonale and P Mitrale

RAH and LAH Right Atrial Hypertrophy Left Atrial Hypertrophy

Short PR Interval WPW (Wolff-Parkinson-White) Syndrome Accessory pathway (Bundle of Kent) allows early activation of the ventricle (delta wave and short PR interval)

WPW (Wolff-Parkinson-White) Syndrome

Accessory pathway (Bundle of Kent) allows early activation of the ventricle (delta wave and short PR interval)

QRS Complexes Non­pathological Q waves are often present in leads I, III, aVL, V5, and V6 The R wave in lead V6 is smaller than the R wave in V5 The depth of the S wave, generally, should not exceed 30 mm Pathological Q wave > 2mm deep and > 1mm wide or > 25% amplitude of the subsequent R wave

Non­pathological Q waves are often present in leads I, III, aVL, V5, and V6

The R wave in lead V6 is smaller than the R wave in V5

The depth of the S wave, generally, should not exceed 30 mm

Pathological Q wave > 2mm deep and > 1mm wide or > 25% amplitude of the subsequent R wave

QRS In Hypertrophy

RVH Changes A tall positive (R) wave instead of the rS complex normally seen in lead V1 an R wave exceeding the S wave in lead V1 in adults the normal R wave in lead V1 is generally smaller than the S wave in that lead Right axis deviation (RAD) Right ventricular &quot;strain&quot; T wave inversions

A tall positive (R) wave

instead of the rS complex normally seen in lead V1

an R wave exceeding the S wave in lead V1

in adults the normal R wave in lead V1 is generally smaller than the S wave in that lead

Right axis deviation (RAD)

Right ventricular &quot;strain&quot; T wave inversions

Conditions with Tall R in V1

Right Atrial and Ventricular Hypertrophy

COPD

Left Ventricular Hypertrophy Sokolow & Lyon Criteria (Am Heart J, 1949;37:161) S in V1+ R in V5 or V6 > 35 mm An R wave of 11 to 13 mm (1.1 to 1.3 mV) or more in lead aVL is another sign of LVH Others: Cornell criteria (Circulation, 1987;3: 565-72) SV3 + R avl > 28 mm in men SV3 + R avl > 20 mm in women

Sokolow & Lyon Criteria (Am Heart J, 1949;37:161)

S in V1+ R in V5 or V6 > 35 mm

An R wave of 11 to 13 mm (1.1 to 1.3 mV) or more in lead aVL is another sign of LVH

Others: Cornell criteria (Circulation, 1987;3: 565-72)

SV3 + R avl > 28 mm in men

SV3 + R avl > 20 mm in women

Hypertrophy Strain Pattern vs ACS

ST Segment Normal ST Segment is flat (isoelectric) Same level with subsequent PR segment Elevation or depression of ST segment by 1 mm or more, measured at J point IS ABNORMAL “ J” (Junction) point is the point between QRS and ST segment

Normal ST Segment is flat (isoelectric)

Same level with subsequent PR segment

Elevation or depression of ST segment by 1 mm or more, measured at J point IS ABNORMAL

“ J” (Junction) point is the point between QRS and ST segment

Variable Shapes Of ST Segment Elevations in AMI Goldberger AL. Goldberger: Clinical Electrocardiography: A Simplified Approach. 7th ed: Mosby Elsevier; 2006.

T wave The normal T wave is asymmetrical, the first half having a more gradual slope than the second half The T wave should generally be at least 1/8 but less than 2/3 of the amplitude of the corresponding R wave T wave amplitude rarely exceeds 10 mm Abnormal T waves are symmetrical, tall, peaked, biphasic or inverted.

The normal T wave is asymmetrical, the first half having a more gradual slope than the second half

The T wave should generally be at least 1/8 but less than 2/3 of the amplitude of the corresponding R wave

T wave amplitude rarely exceeds 10 mm

Abnormal T waves are symmetrical, tall, peaked, biphasic or inverted.

T wave As a rule, the T wave follows the direction of the main QRS deflection. Thus when the main QRS deflection is positive (upright), the T wave is normally positive. Other rules The normal T wave is always negative in lead aVr but positive in lead II. Left-sided chest leads such as V4 to V6 normally always show a positive T wave.

As a rule, the T wave follows the direction of the main QRS deflection. Thus when the main QRS deflection is positive (upright), the T wave is normally positive.

Other rules

The normal T wave is always negative in lead aVr but positive in lead II.

Left-sided chest leads such as V4 to V6 normally always show a positive T wave.

QT interval QT interval decreases when heart rate increases A general guide to the upper limit of QT interval. For HR = 70 bpm, QT<0.40 sec. For every 10 bpm increase above 70 subtract 0.02 sec. For every 10 bpm decrease below 70 add 0.02 sec As a general guide the QT interval should be 0.35­ 0.45 s, and should not be more than half of the interval between adjacent R waves (R­R interval).

QT interval decreases when heart rate increases

A general guide to the upper limit of QT interval. For HR = 70 bpm, QT<0.40 sec.

For every 10 bpm increase above 70 subtract 0.02 sec.

For every 10 bpm decrease below 70 add 0.02 sec

As a general guide the QT interval should be 0.35­ 0.45 s, and should not be more than half of the interval between adjacent R waves (R­R interval).

QT Interval

Long QT Syndrome

QT Interval The QT interval increases slightly with age and tends to be longer in women than in men. Bazett's correction is used to calculate the QT interval corrected for heart rate (QTc): QTc = QT/ Sq root [R­R in seconds]

The QT interval increases slightly with age and tends to be longer in women than in men.

Bazett's correction is used to calculate the QT interval corrected for heart rate (QTc): QTc = QT/ Sq root [R­R in seconds]

U wave Normal U waves are small, round, symmetrical and positive in lead II, with amplitude < 2 mm (amplitude is usually < 1/3 T wave amplitude in same lead) U wave direction is the same as T wave direction in that lead More prominent at slow heart rates and usually best seen in the right precordial leads. Origin of the U wave is thought to be related to afterdepolarizations which interrupt or follow repolarization

Normal U waves are small, round, symmetrical and positive in lead II, with amplitude < 2 mm (amplitude is usually < 1/3 T wave amplitude in same lead)

U wave direction is the same as T wave direction in that lead

More prominent at slow heart rates and usually best seen in the right precordial leads.

Origin of the U wave is thought to be related to afterdepolarizations which interrupt or follow repolarization

Calculation of Heart Rate Method 1: Count the number of large (0.2-second) time boxes between two successive R waves, and divide the constant 300 by this number OR divide the constant 1500 by the number of small (0.04-second) time boxes between two successive R waves. Method 2: Count the number of cardiac cycles that occur every 6 seconds, and multiply this number by 10.

Method 1: Count the number of large (0.2-second) time boxes between two successive R waves, and divide the constant 300 by this number OR divide the constant 1500 by the number of small (0.04-second) time boxes between two successive R waves.

Method 2: Count the number of cardiac cycles that occur every 6 seconds, and multiply this number by 10.

Calculation of Heart Rate

Question Calculate the heart rate

Calculate the heart rate

RBBB and LBBB RBBB = MaRroW LBBB = WiLLiaM

RBBB = MaRroW

LBBB = WiLLiaM

Rhythm Disturbances

Cardiac Arrest & Peri-arrest Rhythms Cardiac Arrest Shockable VF, Pulseless VT Non Shockable Asystole, PEA Peri arrest rhythms Tachyrrhythmias Bradyarrhythmias Drugs to control rate Drugs to revert the rhythms

Cardiac Arrest

Shockable

VF, Pulseless VT

Non Shockable

Asystole, PEA

Peri arrest rhythms

Tachyrrhythmias

Bradyarrhythmias

Drugs to control rate

Drugs to revert the rhythms

Note that by this time, if 3 rd shock is required, it is the DRUG ->SHOCK-> CPR sequence. It is the same sequence thereafter The drugs to be given at this stage are vasopressors Cardiac Arrest

After the 3 rd sequence and giving adrenaline/vasopressin, consider giving antiarrhythmics like amiodarone for VF or magnesium for torsades de pointes. The sequence is still the same DRUG->SHOCK-> CPR. At any time, if rhythm becomes non-shockable, follow the non-shockable algorithm Cardiac Arrest

For cardiac arrest, the first thing to know is whether the rhythm is shockable or not shockable. In periarrest rhythms (bradyarrhythmias and tachyarrhythmias, the first thing to know is whether it STABLE or NOT STABLE

When The Arrhythmias Is Unstable Four main signs Signs of low cardiac output – systolic hypotension < 90 mmHg, altered mental status Excessive rates: <40/min or >150/min Chest pain Heart failure If unstable, electrical therapy: cardioversion for tachyarrhythmias, pacing for bradyarrhythmias

Four main signs

Signs of low cardiac output – systolic hypotension < 90 mmHg, altered mental status

Excessive rates: <40/min or >150/min

Chest pain

Heart failure

If unstable, electrical therapy: cardioversion for tachyarrhythmias, pacing for bradyarrhythmias

Atropine 0.5 mg each bolus up to 3 mg. Atropine as temporizing measure only. Needs transcutaneous/transvenous pacing

Four Rhythms At Risk Of Developing Asystole Recent asystole Mobitz II 2 nd degree AV Block Complete Heart Block (especially with broad QRS or initial heart rate <40/min) Ventricular standstill more than 3 sec For these, consider also electrical therapy Only mentioned in European Resuscitation Council Guidelines 2005

Recent asystole

Mobitz II 2 nd degree AV Block

Complete Heart Block (especially with broad QRS or initial heart rate <40/min)

Ventricular standstill more than 3 sec

For these, consider also electrical therapy

Only mentioned in European Resuscitation Council Guidelines 2005

Bradyarrhythmias 2 nd degree Mobitz type 1 the block is at AV Node Often transient Maybe asymptomatic 2 nd degree Mobitz type 2 Block most often below AV node, at bundle of His or BB May progress to 3 rd degree AV block

2 nd degree Mobitz type 1

the block is at AV Node

Often transient

Maybe asymptomatic

2 nd degree Mobitz type 2

Block most often below AV node, at bundle of His or BB

May progress to 3 rd degree AV block

* For polymorphic VT – if patients become unstable, perform defibrillation rather than cardioversion. If ever in doubt whether to perform cardioversion or defibrillation, then perform DEFIBRILLATION Rule of thumb – if your eye cannot synchronize to each QRS complex, neither can the machine!

Tachyarrhythmias For stable tachyarrhythmias, we need to further decide whether it is NARROW QRS or WIDE QRS For each type, further divide into Regular Irregular

For stable tachyarrhythmias, we need to further decide whether it is NARROW QRS or WIDE QRS

For each type, further divide into

Regular

Irregular

Tachyarrhythmias Narrow QRS tachyarrhythmias Regular Sinus Tachycardia, PSVT, atrial flutter with regular AV conduction Irregular Atrial Fibrillation, Atrial flutter with variable AV Block Wide (Broad) QRS tachyarrhythmias Regular Ventricular Tachycardia, SVT with BBB Irregular Polymorphic VT, AF with BBB

Narrow QRS tachyarrhythmias

Regular

Sinus Tachycardia, PSVT, atrial flutter with regular AV conduction

Irregular

Atrial Fibrillation, Atrial flutter with variable AV Block

Wide (Broad) QRS tachyarrhythmias

Regular

Ventricular Tachycardia, SVT with BBB

Irregular

Polymorphic VT, AF with BBB

Narrow complexes and regular – attempt vagal maneuver and adenosine; Narrow complexes but not regular- likely AF. Don’t give adenosine. May attempt rate control using beta blocker or diltiazem

Amiodarone can be given for both regular and irregular broad complexes

Recommended Resources ABC of Clinical Electrocardiography www.bmj.com Goldberger: Clinical Electrocardiography: A Simplified Approach, 6th edition. Access via www.mdconsult.com ECG Learning Center http://medstat.med.utah.edu/kw/ecg/index.html ECG Library http://www.ecglibrary.com/ecghome.html

ABC of Clinical Electrocardiography

www.bmj.com

Goldberger: Clinical Electrocardiography: A Simplified Approach, 6th edition.

Access via www.mdconsult.com

ECG Learning Center

http://medstat.med.utah.edu/kw/ecg/index.html

ECG Library

http://www.ecglibrary.com/ecghome.html

Thank You Contact me: Dr. K.S. Chew [email_address] http://emergencymedic.blogspot.com