ECG and Arrhythmias

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Transcript of ECG and Arrhythmias

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    ECG and Arrhythmias

    Dec, 1st 2014

    Doctor Mohammad Jarrah

    References: - Lecture and Slides - ECG Made Easy - Davidson Principles of Medicine - First Aid Cases for the USMLE Step 1 - Mini-OSCE Archive

    ECG stands for electrocardiogram; its a record of the hearts electrical activity. its a

    very important tool that can provide evidences to support a specific diagnosis.

    Remember that most abnormalities in the ECG are amenable to reason.

    The Basics:

    The quality of an ECG is determined by the presence of PATIENTS NAME, DATE/TIME, the 12 LEADS and a RYTHEM STRIP at the bottom.

    The paper moves in a speed of 25mm/s (horizontal). ?If faster (50mm/s) itll give a false impression of slow HR

    And a caliberation of 1cm or 10mm/mV (vertical). ?if >1mm/mv gives a false impression of Left Ventriuclar Hypertrophy

    1 small square (Ssq) = 1 mm, 1 large square (Lsq) = 5 Ssq = 5 mm.

    P: Atria Depolarization (220: Block,

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    Normal ECG Positive deflection: If a wave of depolarization passing through the heart is moving toward a surface electrode Negative deflection: If a wave of depolarization passing through the heart is moving away from the electrode. Biphasic wave: If a wave of depolarization passing through the heart is moving perpendicularly to the electrode.

    The 12-Lead ECG

    6 limb leads: I between right arm and left arm. II between right arm and left leg. III between left arm and left leg. aVR: right arm, aVL: left arm, aVF: left leg I, II, aVL: Left lateral surface. III, aVF: Inferior surface. aVR: Right surface.

    In a normal cardiac axis (about 60 degrees): Lead II and aVF have the highest positive deflection.

    I and II are normally both positively deflected. Lead II is usually the long rhythm strip, with the most obvious P wave.

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    6 chest leads: V1 and V2: Parasternal at 4th intercostals space. V3 is in between V2 and V4. V4, V5 and V6 at the 5th intercostal space: V4: Midclavicular line V5: Anterior axillary line V6: Middle axillary line. V1, V2, V3, V4: Anteriospetal surface. V5,V6: Lateral surface

    In a normal cardiac axis (about 60 degrees): - V1: Small R, Deep S - V2: R increases, S decreases - V3/V4: R=S - V5/V6: Large R, S disappears in normal

    people If the R is poorly enlarging (poor progression R wave sign of ischemia)

    The Cardiac Axis: Normally, between -30 and +90

    Right Axis Deviation/RAD (>+90): Right ventricular hypertrophy

    -ve Lead I +ve Lead II

    Left Axis Deviation/LAD (

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    Normal ECG Record:

    12 leads with a rhythm strip (II)

    Good Voltage (2 Lsq or 1cm vertical)

    HR = 300/5 = 60 bpm

    Regular Sinus Rhythm: P wave precedes each QRS with good relation between them

    PR interval is between 3-5 Ssq, P voltage is less than 2.5 Ssq

    QRS complex is less than 3 Ssq

    QT isnt prolonged (

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    ECG Record with some abnormalities:

    12 leads with a rhythm strip (II)

    Good Voltage (2 Lsq or 1cm vertical)

    HR > 60 bpm

    Regular Sinus Rhythm: P wave precedes each QRS with good relation between them

    PR interval is between 3-5 Ssq, P voltage is less than 2.5 Ssq

    QRS complex is slightly widened is some leads

    Left axis deviation (+ve Lead I and ve Lead II)

    Poor progression R wave Ischemia

    S wave in V6 ? Abnormality

    The abnormally looking complex in aVF is just an artefact (not significant)

    Abnormalities due to machine or human error:

    Paper speed 12.5 mm/s false rapid heart rate

    Patient is shivering

    Remember: ECG must be individualized: Male vs Female, Old vs Young, Chest Pain vs Normal

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    The Abnormalities of the waves, complexes and intervals:

    P wave abnormalities Absence Not Sinus

    P Pulmonale: Pointy; >2.5 Ssq vertical in Lead II

    Right Atrial dilatation/hypertrophy due to cor pulmonale/COPD/...

    P Mitral: Bifid in Lead II

    Left Atrial dilatation/hypertrophy due to Mitral stenosis (MS) or sometimes MR

    PR Interval Abnormalities Too short (1Lsq) Heart block/AV block (1st, 2nd and 3rd degrees)

    Spot on Arrhythmias:

    Preexcitation syndromes (WPW Syndrome):

    Preexcitation is a condition characterized by an accessory pathway of conduction,

    which allows the heart to depolarize in an atypical sequence.

    In Wolfe-Parkinson-White (WPW) syndrome, theres a direct atrioventricular

    connection allows the ventricles to begin depolarization while the standard action

    potential is still traveling through the AV node.

    ECG Characteristics of WPW:

    1. Short PR interval 2. QRS prolongation

    3. Delta Wave 4. Followed by tachycardia

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    In fact, the PR interval isnt shortened, but it looks so due to the emergence of the

    delta wave.

    Heart Block (AV block):

    1st degree Heart block: - Prolongation of the

    PR interval, which is constant

    - All P waves are conducted

    2nd degree Heart block (Mobitz 1)/Wenckebach:

    - Progressive prolongation of the PR interval until a P wave is not conducted.

    - As the PR interval prolongs, the RR interval actually shortens

    2nd degree Heart block (Mobitz 2): Constant PR interval with intermittent failure to conduct

    Third degree Heart block (Complete): No relationship between P waves and QRS complexes, Relatively constant PP intervals and RR intervals and Greater number of P waves than QRS complexes

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    QRS complex Abnormalities

    Generally, if QRS > 0.12 ms Bundle Branch Block (Rt vs Lt) Accepted Q waves: V1, aVR and III Pathological Q waves: >25% of

    subsequent complex and unusual location on leads previous infarction.

    Sum of the S wave (-ve deflection) in V1 and the biggest R wave in V5 or V6 >35mm (> 5Lsq) Left Ventricular Hypertrophy (LVH)

    If LVH is presented with ST depression and T inversion on the left leads indicates LVH induced infarction (blood supply isnt enough for the hypertrophied muscle tissue (LVH with Strain)

    LVH with Strain, Normal sinus rhythm

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    Spot on LBBB and RBBB:

    RBBB LBBB Common causes - Normal variant

    - Right ventricular hypertrophy or strain

    - ASD

    - CAD - HTN - Aortic valve disease - Cardiomyopathy

    ECG changes QRS > 3 Ssq RSR (M shaped QRS complex) in V1, V2 and deep S in V6.

    - May present with RAD (usually) or LAD (Atrial septal defect, severe conducting problem)

    QRS > 3 Ssq RSR (M shaped QRS complex) in V5, V6, I and deep S in V1

    - Usually associated with LAD


    Mnemonic MaRRoW: M first letter = M in V1

    WiLLiaM: M last letter = M in V6


    RBBB with LAD:

    Bifascicular rhythm

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    ST segment Abnormalities These are usually in territories eg. anterior/lateral/inferior etc. and will be present in

    contiguous leads (III,aVF or I,aVL,V5,V6 ...)

    ST depression: - Downsloping or horizontal =

    abnormal - Ischaemia (coronary stenosis):

    Chest pain association - If lateral (V4-V6), consider LVH

    with strain or digoxin toxicity

    ST elevation - Infarction (coronary occlusion) - Pericarditis (widespread) - Prinzmetal spasm - Post ventricular aneurysm - Early embolization

    Normal rhythm (P wave in II) and axis, ST elevation is V2-V6, and minimally in aVL, Q

    wave also present: Acute MI in the proximal Left Anterior Descending Artery.

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    Sinus rhythm

    ST depression Lead I, aVL, ST elevation V5, V6 Lateral MI (acute over chronic)

    ST elevation in III and aVF Inferior MI

    reciprocal ST depression in V1, V2 Posterior MI

    InferioPosterioLateral MI

    Super-dominant Right coronary artery, proximal occlusion.

    ask for Right ventricular leads

    Right Ventricular Infarction Cardiogenic Shock Hypotension IV fluids

    Pericarditis: Sinus tachycardia with Diffuse ST elevation in all leads except:

    V1: Normal or depression, aVR: ST depression

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    T wave Abnormalities Peaked hyperkalaemia or normal young man

    Inverted/biphasic ischaemia, previous infarct

    Small hypokalaemia

    What is the rate, rhythm and axis for these patients, and is there any other abnormalities?

    Not sinus (ectopic) and irregular rhythm, rate = 120, right axis deviation?, LVH due to

    deep S and huge R, T inversion can be seen laterally. LVH Right atrial abnormality and fibrillation

    P wave present, Sinus tachycardia and LVH (whats the rate?)

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    Bradycardia, and obvious delta wave in V1 WPW Syndrome

    ST elevation in inferior leads and No relation between P and QRS complete Heart Block

    P wave present, Sinus bradychardia (whats the rate?)

    Recall that the NORMAL SINUS RHYTHM shows Regular narrow-complex rhythm

    Rate 60-100 bpm, Each QRS complex is proceeded by a P wave P wave is upright in lead II & downgoing in lead aVR

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    QT interval Abnormalities QT interval must be corrected because its affected by the HR:

    Long QT (>450ms) can be genetic (long QT syndrome) or secondary due to drugs (amiodarone, sotalol)

    Associated with risk of sudden death due to Torsades de Pointes (