session 8 pptx - طلاب كروب D

ELECTROCARDIOGRAM (ECG or EKG)

Dr. Ahmed Moyed Hussein
M.B.Ch.B- FIBMS(med)
CABMS(med)- FIBMS(cardiol)

What is an ECG?

The electrocardiogram (EKG) is a representation of the electrical events of the cardiac cycle.
Each event has a distinctive waveform
the study of waveform can lead to greater insight into a patient’s cardiac pathophysiology.

With EKGs we can identify

• Arrhythmias
• Myocardial ischemia and infarction
• Pericarditis
• Chamber hypertrophy
• Electrolyte disturbances (i.e. hyperkalemia, hypokalemia)
• Drug toxicity (i.e. digoxin and drugs which prolong the QT interval)

Depolarization

Contraction of any muscle is associated with electrical changes called depolarization

These changes can be detected by electrodes attached to the surface of the body

Conductive system of the heart
SA Node - Dominant pacemaker with an intrinsic rate of 60 - 100 beats/minute.

AV Node - Back-up pacemaker with an intrinsic rate of 40 - 60 beats/minute.

Ventricular cells - Back-up pacemaker with an intrinsic rate of 20 - 45 bpm.

The ECG Paper
Horizontally
One small box - 0.04 s
One large box - 0.20 s
Vertically
One large box - 0.5 mV

EKG Leads

which measure the difference in electrical potential between two points
1. Bipolar Leads: Two different points on the body

2. Unipolar Leads: One point on the body and a virtual reference point with zero electrical potential, located in the center of the heart

EKG Leads

The standard EKG has 12 leads:
3 Standard Limb Leads(I,II,III)
3 Augmented Limb Leads (aVR, aVL, aVF)
6 Precordial Leads (V1-6)

Extra leads:
Right sided ECG leads
Posterior leads

Extra leads

Lead I

extends from the right to the left arm
Lead II
extends from the right arm to the left foot
Lead III
extends from the left arm to the left foot
Einthoven’s Triangle

+
-
+

-

Leads II, III, aVF

Looks at inferior heart wall
Anatomy of a 12-Lead EKG
View of Inferior Heart Wall

Looks from the left leg up

Leads I and aVL
Looks at lateral heart wall
Looks from the left arm toward heart
Anatomy of a 12-Lead EKG (cont.)
View of Lateral Heart Wall
*Sometimes known as High Lateral*

Leads V5 & V6

Looks at lateral heart wall
Looks from the left lateral chest toward heart
Anatomy of a 12-Lead EKG (cont.)
View of Lateral Heart Wall
*Sometimes referred to as Low Lateral or Apical view*

Leads V3, V4
Looks at anterior heart wall
Looks from the left anterior chest
Anatomy of a 12-Lead EKG (cont.)
View of Anterior Heart Wall

Leads V1, V2

Looks at septal heart wall
Looks along sternal borders
Anatomy of a 12-Lead EKG (cont.)
View of Septal Heart Wall

Arrangement of Leads on the EKG

for any givenviewing (positive)electrode:

An approaching train of muscle fiber depolarizations (or repolarizations moving away) is seen as an upward trace on the recording (opposite movement = downward trace)
Interpreting the view from an electrode

Note: the normal average direction for the heart’s electrical activity is from the upper right, in the right atrium, to the lower left.

ECG wave

ECG wave(cont.)

The 8-step method

Step 1: Determine rhythm
Step 2: Calculate rate
Step 3: Evaluate the P wave
Step 4: Calculate the PR interval
Step 5: Evaluate the QRS complex
Step 6: Evaluate the T wave
Step 7: Calculate the duration of the QT interval
Step 8: Evaluate other components

Speed= 25mm/sec

Height 10mm = 1 mV
Note

Reversal limb connection

Dextrocardia

Step 1: Determine rhythm

Step 2: Calculate rate
If the heart rate is regular: Count the number of large squares between R waves i.e. the RR interval in large squares Rate = 300 RR e.g. RR = 4 large squares 300/= 75 beats per minute
If the rhythm is irregular it may be better to estimate the rate using the rhythm strip at the bottom of the ECG (usually lead II) The rhythm strip is usually 25cm long (250mm i.e. 10 seconds) If you count the number of R waves on that strip and multiple by 6 you will get the rate

Step 3: Evaluate the P wave

When examining a rhythm strip for P waves, ask yourself:
Are P waves present?
Do the P waves have a normal configuration?
Do all the P waves have a similar size and shape?
Is there one P wave for every QRS complex?

Atrial Waves

Right Atrial Enlargement

P wave voltage is 4 boxes or 4 mm

Left Atrial Enlargement
36

P wave duration is 4 boxes-0.04 x 4 = 0.16

P wave abnormalities

Step 4: Calculate the PR interval

To measure the PR interval, count the small squares between the start of the P wave and the start of the QRS complex; then multiply the number of squares by 0.04 second.
After performing this calculation, ask yourself:
Does the duration of the PR interval fall within normal limits, 0.12 to 0.20 second (or 3 to 5 small squares)?
Is the PR interval constant?

WPW

WPW Orthodromic tachycardia

WPW Antidromic tachycardia

Long PR Interval

First degree Heart Block

Step 5: Evaluate the QRS complex

When determining QRS-complex duration, make sure you measure straight across from the end of the PR interval to the end of the S wave, not just to the peak.
To calculate duration, count the number of small squares between the beginning and end of the QRS complex and multiply this number by 0.04 second. Then ask yourself:
Does the duration of the QRS complex fall within normal limits, 0.06 to 0.10 second?
Are all QRS complexes the same size and shape? (If not, measure each one and describe them individually.)
Does a QRS complex appear after every P wave?

Q wave

A small Q wave may be normal in lead III, and is often associated with an inverted T wave. Q waves are also normal in lead aVR.
Q waves in other leads are likely to be abnormal or ‘pathological’, particularly if they are:
2 small squares deep, or
25 per cent of the height of the following R wave in depth, and/or
1 small square wide.

Right Ventricular Hypertrophy

Left Ventricular Hypertrophy

ST Segment
ST segments can be abnormal in one of three ways, so the questions you need to ask about the ST segments when you review them are:
Are the ST segments elevated?
Are the ST segments depressed?
Are J waves present?
Causes of ST segment elevation:
acute coronary syndrome(STEMI)
left ventricular aneurysm
Prinzmetal’s (vasospastic) angina
Pericarditis
high take-off (early repolarization)
left bundle branch block
Brugada syndrome.

Acute pericarditis

• Wide spread ST segment elevation (concave )
• PR depression

Early Repolarization

• Young pt with non specific chest

• Wide spread ST elevation with notched J point
• No reciprocal changes

LBBB

• ST elevation with negative QRS

• ST depression with positive QRS

Brugada syndrome

* Partial RBBB, ST elevation in V1-3, with T inversion

Step 6: Evaluate the T wave
Examine the T waves on the ECG strip. Then ask yourself:
Are T waves present?
Do all of the T waves have a normal shape?
Could a P wave be hidden in a T wave?
Do all T waves have a normal amplitude?
Do the T waves have the same deflection as the QRS complexes?

T wave

Normal T wave is asymmetrical, first half having a gradual slope than the second

Should be at least 1/8 but less than 2/3 of the amplitude of the R

T wave amplitude rarely exceeds 10 mm

Abnormal T waves are symmetrical, tall, peaked, biphasic or inverted.

T wave follows the direction of the QRS deflection.

T wave

Hyperkalemia

Hypokalaemia

Step 7: Calculate the duration of the QT interval

To determine the duration of the QT interval, count the number of small squares between the beginning of the QRS complex and the end of the T wave, where the T wave returns to the baseline. Multiply this number by 0.04 second. Ask yourself:
Does the duration of the QT interval fall within normal limits, 0.36 to 0.44 second?

Long QT

Short QT

Step 8: Evaluate other components

Note the presence of ectopic beats or other abnormalities such as aberrant conduction.
look for the presence of a U wave.
Now, interpret your findings by classifying the rhythm strip according to one or all of the following:
Origin of the rhythm: for example, sinus node, atria, AV node, or ventricles
Rate: normal (60 to 100 beats/minute), bradycardia (fewer than 60 beats/minute), or tachycardia (greater than 100 beats/minute)
Rhythm interpretation: normal or abnormal—for example, flutter, fibrillation, heart block, escape rhythm, or other arrhythmias

ST- segment changes

Cardiac Arrhythmia

Conductive system of the heart

SA Node - Dominant pacemaker with an intrinsic rate of 60 - 100 beats/minute.

AV Node - Back-up pacemaker with an intrinsic rate of 40 - 60 beats/minute.

Ventricular cells - Back-up pacemaker with an intrinsic rate of 20 - 45 bpm.

Sinus Node

Rhythm

130 bpm
Rate?
Regularity?
regular
normal
0.08 s
P waves?
PR interval?
0.16 s
QRS duration?
Interpretation?
Sinus Tachycardia

Rhythm

30 bpm
Rate?
Regularity?
regular
normal
0.10 s
P waves?
PR interval?
0.12 s
QRS duration?
Interpretation?
Sinus Bradycardia

Sinus Arrhythmia

Sick Sinus Syndrome(SSS)

Supraventricular Arrhythmias

Atrial Tachycardia
Atrial Fibrillation

Atrial Flutter

Paroxysmal Supraventricular Tachycardia

Rhythm
70 bpm
Rate?
Regularity?
occasionally irreg.
2/7 different contour
0.08 s
P waves?
PR interval?
0.14 s (except 2/7)
QRS duration?
Interpretation?
NSR with Premature Atrial Contractions

Premature Atrial Contractions

Deviation from NSR
These ectopic beats originate in the atria (but not in the SA node), therefore the contour of the P wave, the PR interval, and the timing are different than a normally generated pulse from the SA node.

Premature Atrial Contraction

Atrial Tachycardia

Rhythm

100 bpm
Rate?
Regularity?
irregularly irregular
none
0.06 s
P waves?
PR interval?
none
QRS duration?
Interpretation?
Atrial Fibrillation

Atrial Fibrillation

Deviation from NSR
No organized atrial depolarization, so no normal P waves (impulses are not originating from the sinus node).
Atrial activity is chaotic (resulting in an irregularly irregular rate).
Common, affects 2-4%, up to 5-10% if > 80 years old

Atrial Fibrillation

Rhythm

70 bpm
Rate?
Regularity?
regular
flutter waves
0.06 s
P waves?
PR interval?
none
QRS duration?
Interpretation?
Atrial Flutter

Atrial Flutter 4:1 block

Rhythm

74 148 bpm
Rate?
Regularity?
Regular  regular
Normal  none
0.08 s
P waves?
PR interval?
0.16 s  none
QRS duration?
Interpretation?
Paroxysmal Supraventricular Tachycardia (PSVT)

PSVT

Deviation from NSR

The heart rate suddenly speeds up, often triggered by a PAC (not seen here) and the P waves are lost.

PSVT

Effect of Adenosine

Ventricular Arrhythmias

Premature Ventricular Contractions
Ventricular Tachycardia

Ventricular Fibrillation

Rhythm

60 bpm
Rate?
Regularity?
occasionally irreg.
none for 7th QRS
0.08 s (7th wide)
P waves?
PR interval?
0.14 s
QRS duration?
Interpretation?
Sinus Rhythm with 1 PVC

92
Ventricular Bigeminy

Normal

VPC
VPC
Normal

Rhythm

160 bpm
Rate?
Regularity?
regular
none
wide (> 0.12 sec)
P waves?
PR interval?
none
QRS duration?
Interpretation?
Ventricular Tachycardia

Ventricular Tachycardia

Deviation from NSR
Impulse is originating in the ventricles (no P waves, wide QRS).

Rhythm

none
Rate?
Regularity?
irregularly irreg.
none
wide, if recognizable
P waves?
PR interval?
none
QRS duration?
Interpretation?
Ventricular Fibrillation

Ventricular Fibrillation

Deviation from NSR
Completely abnormal.

Asystole

AV Nodal Blocks

1st Degree AV Block

2nd Degree AV Block, Type I

2nd Degree AV Block, Type II

3rd Degree AV Block

Rhythm
60 bpm
Rate?
Regularity?
regular
normal
0.08 s
P waves?
PR interval?
0.36 s
QRS duration?
Interpretation?
1st Degree AV Block

1st Degree AV Block

Etiology: Prolonged conduction delay in the AV node or Bundle of His.

Rhythm

50 bpm
Rate?
Regularity?
regularly irregular
nl, but 4th no QRS
0.08 s
P waves?
PR interval?
lengthens
QRS duration?
Interpretation?
2nd Degree AV Block, Type I

2nd Degree AV Block, Type II

Deviation from NSR
Occasional P waves are completely blocked (P wave not followed by QRS).

Rhythm

40 bpm
Rate?
Regularity?
regular
nl, 2 of 3 no QRS
0.08 s
P waves?
PR interval?
0.14 s
QRS duration?
Interpretation?
2nd Degree AV Block, Type II

3rd Degree AV Block

Deviation from NSR
The P waves are completely blocked in the AV junction; QRS complexes originate independently from below the junction.

Rhythm

40 bpm
Rate?
Regularity?
regular
no relation to QRS
wide (> 0.12 s)
P waves?
PR interval?
none
QRS duration?
Interpretation?
3rd Degree AV Block

Complete RBBB

Complete LBBB

108

CPR

DC Cardioversion

Acute coronary syndrome

ACUTE CORONARY SYNDROMES
No ST Elevation
ST Elevation
Unstable Angina
NSTEMI STEMI
Myocardial Infarction
NSTEMI

Pathogenesis of ACS
Sequence of events
Plaque Rupture
Platelet Adhesion
Platelet Activation
Platelet Aggregation
Thrombotic Occlusion
Anti-platelet drugs
Platelet rupture
Platelet Adhesion
Platelet Activation
Platelet Aggregation
Thrombotic Occlusion

MI

Thrombus Formation and ACS

UA
NSTEMI

Plaque Disruption/Fissure/Erosion

Thrombus Formation

Non-ST-Segment Elevation Acute Coronary Syndrome (ACS)
ST-Segment Elevation Acute Coronary Syndrome (ACS)

Terminology:

High Serum Troponin

Ischemia and Infarction

118

TRANSMURAL Injury ST Elevation

ST Segment Depression

• Upward sloping depression of ST segment is not indicative of IHD
• It is called J point depression or sagging ST seg
• Downward slopping or Horizontal depression of ST segment leading to T↓is significant of IHD
119

ST depression

Deep symmetric inverted T waves

In more than 2 precardial leads
85% of the patients with such T wave↓had > 75% stenosis of the coronary artery
T wave ↓are significantly associated with MI or death during follow up
T Wave Inversion