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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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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 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

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

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


    Ventricular tachycardia
    Ventricular Tachycardia

    ...more than three PVCs

    Ventricular fibrillation
    Ventricular Fibrillation

    Note the course and fine waves