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ECG Interpretation Criteria Review. Left. Right. Axis Deviation. RAD = If R wave in III > R wave in II LAD = If R wave in aV L > I; and deep S wave in III. Axis Deviation Criteria. Axis Deviation. LAD = possible left anterior fasicular block RAD = possible left posterior fasicular block.

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ECG Interpretation Criteria Review

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Ecg interpretation criteria review

ECG Interpretation Criteria Review

Axis deviation



Axis Deviation

  • RAD = If R wave in III > R wave in II

  • LAD = If R wave in aVL > I; and deep S wave in III

Axis deviation criteria

Axis Deviation Criteria

Axis deviation1

Axis Deviation

  • LAD = possible left anterior fasicular block

  • RAD = possible left posterior fasicular block

Right atrial abnormality criteria

Right Atrial Abnormality Criteria

  • Tall P waves in lead II

  • (or III, aVF and sometimes V1)

Left atrial abnormality

Left Atrial Abnormality

  • Lead II (and I) show wide P waves

    • (second hump due to delayed depolarization of the left atrium)

    • (P mitrale: mitral valve disease)

  • V1 may show a bi-phasic P wave

    • 1 box wide, 1 box deep

    • (biphasic since right atria is anterior to the left atria)

Right ventricular hypertrophy criteria

Right Ventricular Hypertrophy Criteria

  • In V1, R wave is greater than the S wave - or - R in V1 greater than 7 mm

  • Right axis deviation

  • In V1, T wave inversion (reason unknown)

Left ventricular hypertrophy criteria

Left Ventricular Hypertrophy Criteria

  • If S wave in V1 or V2 + R wave in V5 or V6 ≥ 35 mm...

  • ...or, R wave > 11 (or 13) mm in aVL or I...

  • ...or, R in I + S in III > 25 mm.

  • Also

    • LVH is more likely with a “strain pattern” or ST segment changes

    • Left axis deviation

    • Left atrial abnormality

Right bundle branch block criteria

Right Bundle Branch Block Criteria

  • V1 or V2 = rSR’ - “M” or rabbit ear shape

  • V5 or V6 = qRS

  • Large R waves

  • Right chest leads: T wave inversion (“secondary changes” since they reflect a delay in depolarization not an actual change in depolarization).

  • Complete RBBB: QRS > 0.12 sec.

  • Incomplete RBBB: QRS = 0.10 to 0.12 sec.

Left bundle branch block criteria

Left Bundle Branch Block Criteria

  • Wide QRS complex

  • V1 = QS (or rS) and may have a “W” shape to it.

  • V6 = R or notched R and may show a “M” shape or rabbit ears

  • Secondary T wave inversion

    • Secondary if in lead with tall R waves

    • Primary if in right precordial leads

Incomplete bundle branch blocks

Incomplete Bundle Branch Blocks

  • RBBB or LBBB where QRS is between .10 and .12 with same QRS features

Left anterior fascicular block

Left Anterior Fascicular Block

  • Limb leads

  • QRS less width less than 0.12 sec.

  • QRS axis = Left axis deviation (-45° or more)

  • if S wave in aVF is greater than R wave in lead I

  • small Q wave in lead I, aVL, or V6

Left posterior fascicular block

Left Posterior Fascicular Block

  • Right axis deviation (QRS axis +120° or more)

  • S wave in lead I and a Q wave in lead III (S1Q3)

  • Rare

Bifascicular block

Bifascicular Block

  • Two of the three fascicles are blocked.

  • Most common is RBBB with left anterior fascicular block.

Ecg interpretation criteria review



Partial occlusion


Infarction (MI)

Complete occlusion

Ecg interpretation criteria review

  • A. Normal ECG prior to MI

  • B. Hyperacute T wave changes - increased T wave amplitude and width; may also see ST elevation

  • C. Marked ST elevation with hyperacute T wave changes (transmural injury)

  • D. Pathologic Q waves, less ST elevation, terminal T wave inversion (necrosis) 

  • E. Pathologic Q waves, T wave inversion (necrosis and fibrosis)

  • F. Pathologic Q waves, upright T waves (fibrosis)



Anterior infarctions

Anterior Infarctions

  • Abnormal Q waves in chest leads

  • Anterior MI can show loss of R wave progression in the chest leads

Inferior infarctions

Inferior Infarctions

  • Abnormal Q waves in leads II, III, and aVF



  • Lateral - V5 and V6

  • High lateral when ST elevation and Q waves localized to leads I and aVL

Posterior mi

Posterior MI

  • Tall R waves in V1,V2

    • R/S ratio > 1 in V1, V2

    • The tall, anterior R waves are mirror images of a pathological, posterior Q waves.

    • Absences of right axis deviation (found with RVH)

  • ST segment depression in V1-V3

  • Often seen with inferior MI

Infarctions or bbb

Infarctions or BBB


    • T wave inversion and ST segment depression in V1 & V2 (RBBB) and V5 & V6 (LBBB)

  • MI

    • T wave inversion and ST segment depression in additional leads

    • Likely loss of R wave progression

Infarctions and bbb

Infarctions and BBB

  • RBBB and MI

    • usual ECG changes in leads other than V1 and V2

    • septal MI - upright T waves in V1 and V2

      • with just RBBB the T waves should be inverted so upright T waves w/ RBBB are “abnormal” and indicated septal MI

Infarctions and lbbb

Infarctions and LBBB

  • Infarctions often damage the left bundle branch leading to a new or recent LBBB

  • expect to see upright T waves in left chest leads

  • septal MI are very difficult to assess with LBBB

Subendocardial ischemia

Subendocardial Ischemia

  • ST Segment depression

    • Anterior leads (I, aVl and V1-V6)

    • Inferior leads (II, III, and aVf)

    • may see ST segment elevation in aVr

  • T wave inversion

  • Poor R wave progression

Subendocardial infarction

Subendocardial Infarction

  • No Q waves (non-Q wave infarction)

  • Persistent ST segment depression

  • T wave inversion

Sinus bradycardia

Sinus Bradycardia

  • HR less than 60 bpm

Sinus tachycardia

Sinus Tachycardia

  • HR > 100 bpm

Premature atrial complexes pac

Premature Atrial Complexes (PAC)

  • Normal conduction

  • Conducted with aberration

    • a fascicles or bundle branch is refractory

    • wide QRS

  • Non-conducted

    • the AV node was still refractory; P wave will be close to the T wave

    • no QRS complex

Atrial tachycardia

Atrial Tachycardia

Av nodal reentrant tachycardia

Figure 14-6

AV Nodal Reentrant Tachycardia

  • Rapid recirculating impluse in the AV node area (140-250 beats/min)

  • No P waves (hidden in QRS complex) or may be just before or after the QRS complex

  • Negative P waves in lead II

Atrial flutter

Atrial Flutter

  • Sawtooth; F waves (easiest seen in II, III, & aVF)

  • Atrial rate of about 300 bpm

  • Ventricular rate150, 100 or 75 beats/min

  • 2:1, 3:1 and 4:1

Atrial fibrillation

Atrial Fibrillation

  • No organized depolarization in atria.

  • Irregular “f waves” can range from looking almost like P waves to a flat line.

  • Atrial rate is about 600 bpm

  • Normal QRS w/ ventricular rate ~110-180 but random & irregular

Junctional rhythm

Junctional Rhythm

Accelerated junctional rhythm

Accelerated Junctional Rhythm

Ecg interpretation criteria review


First degree av block

First Degree AV Block

2nd degree av block type 1

2nd Degree AV Block, Type 1

2nd degree av block type 2

2nd Degree AV Block, Type 2

2rd degree av block

2rd Degree AV Block

Premature ventricular contractions

Premature Ventricular Contractions

  • Characteristics

    • Premature and occur before the next normal beat

    • Wide (> 0.12 ms) and the T wave is usually opposite of the QRS

    • Bizarre looking

  • PVCs usually precede a P wave.

  • A nonsinus P wave may follow the PVC

  • Ecg interpretation criteria review


    • Unifocal (monomorphic) PVCs

      • same appearance in the same lead

      • small focus

      • normal and diseased hearts

    Ecg interpretation criteria review


    • Polymorphic (multifocal and multiform) PVCs

      • different appearance in the same lead

      • multiform = different coupling intervals

      • multifocal = same coupling intervals

      • usually diseased hearts


    Idioventricular rhythm

    Idioventricular Rhythm





    Bigeminy and trigeminy

    Bigeminy and Trigeminy

    Ventricular tachycardia

    Ventricular Tachycardia

    ...more than three PVCs

    Torsades de pointes

    Torsades de Pointes

    Ventricular fibrillation

    Ventricular Fibrillation

    Note the course and fine waves

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