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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.



Partial occlusion


Infarction (MI)

Complete occlusion

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
  • Unifocal (monomorphic) PVCs
    • same appearance in the same lead
    • small focus
    • normal and diseased hearts
  • 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