ECG Interpretation

Criteria Review

ECG Interpretation

Criteria Review

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

Left

Right

Axis Deviation Criteria

LEAD I LEAD II (or Lead aVF or III)

Normal Positive Positive

LAD Positive Negative

RAD Negative Positive

Intermediate axis Negative Negative

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

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

2.Right axis deviation

3. 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.

SubendocardialIschemia

Partial occlusion

TransmuralInfarction (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)

1. Normal conduction

2. Conducted with aberration

✦ a fascicles or bundle branch is refractory

✦ wide QRS

3. 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

✦ 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

Figure 14-6Figure 14-6

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 ~110-180 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

1.Premature and occur before the next normal beat

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

3.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

Torsades de Pointes

Ventricular Fibrillation

Note the course and fine waves