# ECG Interpretation Criteria Review

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ECG Interpretation Criteria Review

Axis Deviation RAD = If R wave in III > R wave in II
Left Right 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 LAD = possible left anterior fasicular block
RAD = possible left posterior fasicular block

Right Atrial Abnormality Criteria
Tall P waves in lead II (or III, aVF and sometimes V1)

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

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
Right axis deviation (QRS axis +120° or more) S wave in lead I and a Q wave in lead III (S1Q3) Rare

Bifascicular Block Two of the three fascicles are blocked.
Most common is RBBB with left anterior fascicular block.

Subendocardial Ischemia Partial occlusion Transmural 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)

Infarction

Anterior Infarctions Abnormal Q waves in chest leads
Anterior MI can show loss of R wave progression in the chest leads

Inferior Infarctions Abnormal Q waves in leads II, III, and aVF

Lateral Lateral - V5 and V6
High lateral when ST elevation and Q waves localized to leads I and aVL

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 RBBB & LBBB
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 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 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
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
No Q waves (non-Q wave infarction) Persistent ST segment depression T wave inversion

Sinus Bradycardia HR less than 60 bpm

Sinus Tachycardia HR > 100 bpm

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

AV Nodal Reentrant Tachycardia
Figure 14-6 Rapid recirculating impluse in the AV node area ( 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 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 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 ~ but random & irregular

Junctional Rhythm

Accelerated Junctional Rhythm

WPW

First Degree AV Block

2nd Degree AV Block, Type 1

2nd Degree AV Block, Type 2

2rd Degree AV Block

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

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

PVC Polymorphic (multifocal and multiform) PVCs
different appearance in the same lead multiform = different coupling intervals multifocal = same coupling intervals usually diseased hearts Multiform

Idioventricular Rhythm

Couplet

Triplet

Bigeminy and Trigeminy

Ventricular Tachycardia
...more than three PVCs