ECG interpretation 1 and 2

P wave

Atrial Depolarization

PR Interval

AV node pause

QRS complex

Ventricular Depolarization

ST segment

Plateau of all ventricular action potentials

T wave

Repolarization of ventricular cells

U wave

After T wave

Normal P wave value

0.12-0.20 secs (3-5 small boxes)

Normal PR interval

0.10-0.20 secs

Normal QRS interval

1st deflection to return to baseline

Normal: <.120 secs (less than 3 boxes)

QT interval

Beginning of QRS to end of T-Wave

Normal <.450 secs

Normal axis values

-30 to +90

RAD values

180 to +90

LAD Values

-90 to -30

Extreme RAD

180 to -90

Causes of Right bundle branch blocks

Coronary artery disease

Pulmonary hypertension

Right ventricular hypertrophy

Pulmonary embolus

Myocarditis or cardiomyopathy

Congenital

Causes of Left bundle branch blocks

Aortic stenosis

Ischemic heart disease/myocardial infarction

Hypertension

Cardiomyopathy

Hyperkalemia

Digoxin toxicity

Primary degenerative disease (fibrosis) of the conducting system

Anterior Hemiblock

Left axis deviation of > -45 with no other explanation

Small q in 1, aVL

Small r in II, III, aVF

Posterior Hemiblock

Right axis deviation > +120 with no other explanation

Small r in 1, aVL

Small q in II, III, aVF

How much time is 1 box worth on EKG paper

.04 secs

How many millivolts is 1 small box

0.1 mv

What leads help with the QRS Axis

Limb leads (I, II, III, aVR, aVL, aVF)

EKG Evaluation

1.) Rate

2.) Rhythm (P-waves and intervals)

3.) Axis

4.) Hypertrophy, bundle branch blocks

5.) Ischemia, injury or infarct

Assess rhythm steps

1. Regular or irregular? (calipers)

2. Assess for p waves (sometimes the rate is so fast it is difficult to assess for p waves)- is there a p wave with every QRS complex?

3. Measure PR interval

4. Measure QRS segment

5. Assess the T wave

What are the 2 most important steps for rhythm analysis

1. Regular or irregular (R-R interval easiest to assess)

2. P wave coupled with every QRS complex

What is normal sinus rhythm

Normal sinus rhythm= Each QRS preceded by a P wave (which is positive in II and negative in aVR) with a regular PR and RR interval and a rate between 60 and 100 beats/min

Normal axis I and aVF

Positive

LAD axis determination I and aVF

I is positive

aVF is negative

RAD axis determination I and aVF

I is Negative

aVF is postive

Extreme right axis deviation determination I and aVF

Both are negative

If LAD possible, what lead do you look at next

II

In potential LAD, If lead II is negative, then axis is

LAD

In possible LAD, if lead II is positive, then axis is

Normal

What leads do you check for RBBB

QRS >.12 secs

V1 and V2

Prominent S waves in 1, aVL

What leads do you check for LBBB

QRS >.12 secs

V5 and V6

Broad R waves in 1, aVL, V6

What are the causes of Right Atrial enlargement

Principal cause is pulmonary hypertension due to:

1. Chronic lung disease (cor pulmonale)

2. Tricuspid stenosis

3. Congenital heart disease (pulmonary stenosis, Tetralogy of Fallot)

4. Primary pulmonary hypertension

5. Dilated cardiomyopathy

Causes of Left Atrial Enlargement

1. Hypertension

2. Mitral valve disease

3. Aortic valve disease

4. Coronary artery disease

5. Dilated cardiomyopathy

6. Diastolic dysfunction

7. Left ventricular hypertrophy

8. Congenital heart disease

Definition of Right Atrial enlargement:

P-wave is tall and peaked in leads II, III and aVF with an amplitude (height) ≥ 2.5 mm (can also see at times in precordial leads) (P-pulmonale)

Definition of Left Atrial Enlargement

The terminal portion (negative deflection) of the biphasic P-wave (best seen in lead V1) is larger than the initial upward deflection (m shaped P wave in II) (m-mitrale)

Causes of right ventricular hypertrophy

1.) Chronic lung disease leading to pulmonary hypertension (cor

pulmonale)

2. Severe tricuspid regurgitation (as opposed to tricuspid stenosis with RAE)

3. Chronic hypoxia

4. Congenital heart disease

5. Cardiomyopathy

6. Hyperthyroidism

Causes of Left Ventricular Hypertrophy

1. Hypertension (by far most common cause)

2. Aortic stenosis

3. Aortic regurgitation

4. Mitral regurgitation

5. Intensive athletic training

6. Hypertrophic obstructive cardiomyopathy (HOCM)

7. Congenital heart disease

What is seen in RVH

Tall R-wave in v1

What is seen in LVH

Sokolow-Lyon criteria

S in v1 + R in V5/V6 >35

Definition of 1st degree AV block

PR interval is >200 ms

Type 1 Second degree AV block definition

Wenckebach: progressive prolongation of PRV interval until a QRS complex is dropped

Type 2 Second degree AV block

More dangerous than type 1, regular P waves with occasional loss of QRS complex

Third degree AV block definition

complete failure of conduction from the atria to the ventricles, atrial rate always faster than ventricular rate

Where do Supraventricular tachycardias originate?

At or above the AV node, typically narrow complex

Where do ventricular tachyarrhythmias originate?

Below the AV node, wide complex

What are some examples of SVTs

Sinus tachycardia

Atrial tachycardia

Multifocal atrial tachycardia (MAT)

Atrial Flutter

Atrial Fibrillation (Afib)

Junctional Tachycardia

What are the most important things with the differential diagnosis of tachydysrhythmias?

1.) Regular or irregular

2.) Narrow or wide QRS?

3.) P-waves: absent or present?

Definition of Supraventricular tachyarrythmias

An umbrella term used to describe tachycardias (ventricular rates >100 bpm at rest), the mechanism of which involves tissue from the His bundle or above

Definition of Sinus Tachycardia

Sinus-driven rhythm (normal-appearing P wave axis on ECG) with rate of >100 bpm

Definition of Focal atrial tachycardia

Regular atrial rhythm that occurs at frequency of >100 bpm (typically very fast 150 bpm) and originates from a single site within the right or left atrium (outside the SA node)

What is the definition of multifocal atrial tachycardia?

Irregular rhythm with HR >100 bpm yielding P waves with three or more different morphologies

What is multifocal atrial tachycardia most associated with?

COPD

Definition of Atrial Flutter

Rapid, regular atrial depolarizations at a characteristic rate of approximately 300 beats/min and a regular ventricular rate of about 150 beats/min (in patients not taking atrioventricular (AV) nodal blockers)

What pattern is seen in Atrial Flutter? What leads?

Sawtooth in leads II, III and aVF