Ecg interpretations. How to analyze a rhythm. Normal sinus rhythm. Heart arrhythmias. Diagnosing a myocardial infarction

Course Objectives

To recognize the normal rhythm of the heart - “Normal

Learning Modules

ECG Basics
How to Analyze a Rhythm
Normal Sinus Rhythm
Heart Arrhythmias
Diagnosing a

Normal Impulse Conduction

Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers

Impulse Conduction & the ECG

Sinoatrial node
AV node
Bundle of His
Bundle Branches
Purkinje fibers

The “PQRST”

P wave - Atrial depolarization

T wave - Ventricular repolarization

The PR Interval

Atrial depolarization
+
delay in AV junction
(AV node/Bundle of

Pacemakers of the Heart

SA Node - Dominant pacemaker with an intrinsic

The ECG Paper

Horizontally
One small box - 0.04 s
One large box -

The ECG Paper (cont)
Every 3 seconds (15 large boxes) is marked

ECG Rhythm Interpretation

Really Very Easy How to Analyze a Rhythm

Rhythm Analysis
Step 1: Calculate rate.
Step 2: Determine regularity.
Step 3: Assess the P waves.
Step 4: Determine

Step 1: Calculate Rate
Option 1
Count the # of R waves in

Step 1: Calculate Rate
Option 2
Find a R wave that lands

Step 1: Calculate Rate
Option 2 (cont)
Memorize the sequence:
300 - 150

Step 2: Determine regularity
Look at the R-R distances (using a caliper

Step 3: Assess the P waves
Are there P waves?
Do the P

Step 4: Determine PR interval
Normal: 0.12 - 0.20 seconds.
(3 -

Step 5: QRS duration
Normal: 0.04 - 0.12 seconds.
(1 - 3

Rhythm Summary
Rate 90-95 bpm
Regularity regular
P waves normal
PR interval 0.12 s
QRS duration 0.08 s
Interpretation?

Normal Sinus Rhythm

NSR Parameters

Rate 60 - 100 bpm
Regularity regular
P waves normal
PR interval 0.12 - 0.20 s
QRS duration 0.04

Arrhythmia Formation

Arrhythmias can arise from problems in the:
Sinus node
Atrial cells
AV junction
Ventricular

SA Node Problems

The SA Node can:
fire too slow
fire too fast
Sinus Bradycardia
Sinus

Atrial Cell Problems

Atrial cells can:
fire occasionally from a focus
fire continuously

Atrial Cell Problems

Atrial cells can also:
• fire continuously from multiple foci

Teaching Moment

Multiple micro re-entrant “wavelets” refers to wandering small areas of

AV Junctional Problems

The AV junction can:
fire continuously due to a looping

Ventricular Cell Problems

Ventricular cells can:
fire occasionally from 1 or more foci
fire

Arrhythmias

Sinus Rhythms
Premature Beats
Supraventricular Arrhythmias
Ventricular Arrhythmias
AV Junctional Blocks

Sinus Rhythms

Sinus Bradycardia
Sinus Tachycardia
Sinus Arrest
Normal Sinus Rhythm

Rhythm #1

30 bpm

Rate?

Regularity?

regular

normal

0.10 s

P waves?

PR interval?

0.12 s

Sinus Bradycardia
Deviation from NSR
- Rate < 60 bpm

Sinus Bradycardia
Etiology: SA node is depolarizing slower than normal, impulse is

Rhythm #2

130 bpm

Rate?

Regularity?

regular

normal

0.08 s

P waves?

PR interval?

0.16 s

Sinus Tachycardia
Deviation from NSR
- Rate > 100 bpm

Sinus Tachycardia
Etiology: SA node is depolarizing faster than normal, impulse is

Sinus Arrest
Etiology: SA node fails to depolarize and no compensatory mechanisms

Premature Beats

Premature Atrial Contractions (PACs)
Premature Ventricular Contractions (PVCs)

Rhythm #3

70 bpm

Rate?

Regularity?

occasionally irreg.

2/7 different contour

0.08 s

P waves?

Premature Atrial Contractions
Deviation from NSR
These ectopic beats originate in the atria

Premature Atrial Contractions
Etiology: Excitation of an atrial cell forms an impulse

Teaching Moment

When an impulse originates anywhere in the atria (SA node,

Rhythm #4

60 bpm

Rate?

Regularity?

occasionally irreg.

none for 7th QRS

0.08 s (7th

PVCs
Deviation from NSR
Ectopic beats originate in the ventricles resulting in wide

PVCs
Etiology: One or more ventricular cells are depolarizing and the impulses

Teaching Moment

When an impulse originates in a ventricle, conduction through the

Ventricular Conduction

Normal
Signal moves rapidly through the ventricles

Abnormal
Signal moves slowly through the

Supraventricular Arrhythmias

Atrial Fibrillation
Atrial Flutter
Paroxysmal Supra Ventricular Tachycardia (PSVT)

Rhythm #5

100 bpm

Rate?

Regularity?

irregularly irregular

none

0.06 s

P waves?

PR interval?

none

Atrial Fibrillation

Deviation from NSR
No organized atrial depolarization, so no normal P

Atrial Fibrillation

Etiology: due to multiple re-entrant wavelets conducted between the R

Rhythm #6

70 bpm

Rate?

Regularity?

regular

flutter waves

0.06 s

P waves?

PR interval?

none

Atrial Flutter
Deviation from NSR
No P waves. Instead flutter waves (note “sawtooth”

Atrial Flutter
Etiology: Reentrant pathway in the right atrium with every 2nd,

Rhythm #7

74 ?148 bpm

Rate?

Regularity?

Regular ? regular

Normal ? none

0.08 s

PSVT: Paroxysmal Supra Ventricular Tachycardia
Deviation from NSR
The heart rate suddenly speeds up,

AV Nodal Blocks

1st Degree AV Block
2nd Degree AV Block, Type I
2nd

Rhythm #10

60 bpm

Rate?

Regularity?

regular

normal

0.08 s

P waves?

PR interval?

0.36 s

1st Degree AV Block
Deviation from NSR
PR Interval > 0.20 s

1st Degree AV Block
Etiology: Prolonged conduction delay in the AV node

Rhythm #11

50 bpm

Rate?

Regularity?

regularly irregular

nl, but 4th no QRS

0.08 s

2nd Degree AV Block, Type I
Deviation from NSR
PR interval progressively lengthens,

2nd Degree AV Block, Type I
Etiology: Each successive atrial impulse encounters

Rhythm #12

40 bpm

Rate?

Regularity?

regular

nl, 2 of 3 no QRS

0.08 s

2nd Degree AV Block, Type II
Deviation from NSR
Occasional P waves are

Rhythm #13

40 bpm

Rate?

Regularity?

regular

no relation to QRS

wide (> 0.12 s)

3rd Degree AV Block
Deviation from NSR
The P waves are completely blocked

3rd Degree AV Block
Etiology: There is complete block of conduction in

Remember

When an impulse originates in a ventricle, conduction through the ventricles

Ventricular Fibrillation

Rhythm: irregular-coarse or fine, wave form varies in size and

Ventricular Tachycardia

Ventricular cells fire continuously due to a looping re-entrant circuit

Asystole

Ventricular standstill, no electrical activity, no cardiac output – no pulse!
Cardiac

IdioVentricular Rhythm

Escape rhythm (safety mechanism) to prevent ventricular standstill
HIS/purkinje system takes

Diagnosing a MI

To diagnose a myocardial infarction you need to go

The 12-Lead ECG

The 12-Lead ECG sees the heart from 12 different

The 12-Leads

The 12-leads include:

3 Limb leads (I, II, III)

3 Augmented leads

Views of the Heart

Some leads get a good view of the:

Anterior

ST Elevation

One way to diagnose an acute MI is to look

ST Elevation (cont)

Elevation of the ST segment (greater than 1 small

Anterior View of the Heart

The anterior portion of the heart is

Anterior Myocardial Infarction

If you see changes in leads V1 - V4

Putting it all Together

Do you think this person is having a

Interpretation

Yes, this person is having an acute anterior wall myocardial infarction.

Other MI Locations

Now that you know where to look for an

Views of the Heart

Some leads get a good view of the:

Anterior

Other MI Locations

Second, remember that the 12-leads of the ECG look

Other MI Locations

Now, using these 3 diagrams let’s figure where to

Anterior MI

Remember the anterior portion of the heart is best viewed

Lateral MI

So what leads do you think the lateral portion of

Inferior MI

Now how about the inferior portion of the heart?

Limb

Putting it all Together

Now, where do you think this person is

Inferior Wall MI

This is an inferior MI. Note the ST elevation

Putting it all Together

How about now?

Anterolateral MI

This person’s MI involves both the anterior wall (V2-V4) and

Reading 12-Lead ECGs

The best way to read 12-lead ECGs is to

Rate Rhythm Axis Intervals Hypertrophy Infarct

In Module II you learned