Summarize the following text to main points and sub-points and make detailed explain for them:

 
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ECG interpretation 
 
 
 
 
 
 
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Anatomy of the heart 
 
          
 
Component of the heart 
1. Four chambers : 
• two atria (right & left)  
• two ventricle  (right & left) 
2. Four valves : 
Atrioventricular valves : tricuspid and  bicuspid valve (mitral valve ) . 
Semilunar valves : aortic and pulmonary valve . 
N.B : 
All cardiac valves are tricuspid in its nature except mitral valve that is bicuspid. 
 
3. Blood Vessels ( arteries , veins and capillaries  ) 
4. Conductive system ( electrical system) . 
 
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cardiac cycle 
              
 
 
Properties of the Cardiac Muscle 
1. Excitability : Is the ability of cardiac muscle to respond to adequate stimuli by 
generating an action potential. 
2. Rhythmicity/Automaticity : In the myocardium, automaticity is the ability of the 
cardiac muscles to depolarize spontaneously, without external electrical stimulation 
from the nervous system. 
3. Conductivity :Is the ability of cardiac muscle fibers to conduct the cardiac impulses 
that are initiated in the SA node (the pacemaker of the heart). 
4. Contractility :It is the ability of the cardiac muscle to convert electrical energy into 
mechanical work. Myocardial fibers have ‘functional syncytium’ and not ‘anatomical 
syncytium’, because they present in contact but not in continuity. 
 
 
 
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Action potential of the heart 
 
 
➢ The cardiac cycle is composed of both the electrical activity due to automaticity and the 
mechanical (muscular) response known as contraction. 
➢ Generation and transmission of electrical impulses depend on the properties of cardiac 
muscles :  automaticity, excitability, conductivity, and contractility of cardiac cells. 
➢ The electrical activity can be divided into two phases called depolarization and 
repolarization.  
• Depolarization is the active phase of electrical activity. 
• Repolarization is the resting phase during which electrical activity is minimal.  
➢ The mechanical response is divided into diastole and systole. 
• Phase of the cardiac cycle when the myocardium contracts is termed systole. 
• Phase of the cardiac cycle when myocardium is relaxed is termed diastole. 
 
 
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conductive system 
 
             
 
 
Phases of conductive system : 
1. SA Node : 
Under normal conditions, electrical activity is spontaneously generated by the SA node, the 
physiological pacemaker. This electrical impulse is propagated throughout the right atrium, and 
through Bachmann’s bundle to the left atrium, stimulating the myocardium of both atria to 
contract. As the electrical activity is spreading throughout the atria, it travels via specialized 
pathways, known as internodal tracts, from the SA node to the AV node. 
3. Internodal Tracts : 
They comprise of three namely, anterior bundle of Bachmann, middle-Wenkebach, and 
posterior bundle of Thorel. 
4. AV Node : 
The AV node functions as a critical delay in the conduction system. Without this delay, the atria 
and ventricles would contract at the same time, and blood would not flow effectively from the 
atria to the ventricles. 
 
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5. Bundle of His : 
The distal portion of the AV node is known as the bundle of His. The bundle of His splits into 
two branches in the interventricular septum, the left bundle branch and the right bundle branch. 
The left bundle branch activates the left ventricle, while the right bundle branch activates the 
right ventricle. The left bundle branch is short, splitting into the left anterior fascicle and the left 
posterior fascicle. 
6. Purkinje Fibers/Ventricular Myocardium : 
The two bundle branches taper out to produce numerous Purkinje fibers, which stimulate 
individual groups of myocardial cells to contract. 
 
Types of ECG recording 
There are two types of ECG recording are : 
1. 
 12-Lead ECG                                    
The 12-Lead ECG sees the heart from 12 different views. 
The leads of the 12 lead ECG are divided into 6 Limb Leads and 6 Precordial or Chest Leads . 
  
 
 
 
 
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2. 
Single lead ECG  
The rhythm strip is only 1 of these 12 views. 
  
ECG Paper 
 
                     
 
 
 
 
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ECG wave 
            
 
P wave : represent atrial depolarization. 
P-R interval : brief delay of AV node . 
Logically , it should be called  P-Q interval , but common usage is P-R interval. 
QRS complex :Represent ventricular depolarization. 
T wave : represent ventricular repolarization . 
ST segment : isoelectrical period (no electrical activity ). 
QT interval : represent period from the beginning of the ventricular depolarization 
to the end of the ventricular repolarization . 
R-R interval : represent period between two R wave . 
N.B 
Where is atrial repolarization representation ??? 
Because of the atrial repolarization produced at the same time of the ventricular 
depolarization , the atrial repolarization disappeared under it . 
 
 
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Golden rule of ECG interpretation 
 
                      
 
 
 
ECG leads location of heart 
   
 
        
 
 
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To interpret ECG you should follow this points : 
1. Rhythm 
2. Heart rate  
3. Axis 
4. Voltage 
5. Three waves  
• P wave  
• QRS complex 
• T wave  
6. Three intervals 
• P-R interval 
• S-T segment 
• Q-T interval 
 
1. Rhythm: 
See if the rhythm of ECG regular or irregular 
Normally rhythm must be regular, if it is not regular, you should think about the 
following arrhythmia:  
1) Atrial Fibrillation (AF). 
2) Premature contractions (PMC). 
• Atrial premature contractions (APCs). 
• Ventricular premature contractions (VPCs) OR (PVCs). 
 
 
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1) Atrial Fibrillation (AF) : 
 this mean that there are many foci in the two atria generate impulses rather than 
SA node . 
Main criteria of AF :  
o Absent P wave ( fibrillatory wave ) 
o Irregular rhythm. 
o Tachycardia. 
o Normal QRS complex . 
 
 
 
 
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2) Premature contractions ( PMC )  
 
 
A. Atrial premature contractions (APCs): 
This mean that one P wave occurred before its normal period, and because of this 
the irregularity in the rhythm and abnormal P wave shape occur.  
• Main criteria of APCs: 
o Irregular rhythm. 
o Normal QRS complex. 
o Presence of P wave but it is abnormal or bizarre shape. 
               
 
 
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B. Ventricular premature contractions (VPCs) OR ( PVCs ): 
          Main criteria of PVCs: 
o Irregular rhythm. 
o Wide bizarre QRS complex. 
 
                  
 
 
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2. Heart rate 
 
If the rhythm is regular, there are two formula: 
1.  300/ number of big squares between two QRS complex. 
2. 1500/ number of small squares between two QRS complex. 
 
If the rhythm is irregular, there are four formula: 
1. Number of QRS complex in 10 big squares x 30  
2. Number of QRS complex in 30 big squares x10 
3. Number of QRS complex in 20 big squares x15 
4. Number of QRS complex in 15 big squares x20 
Regular Tachycardia 
1. Sinus tachycardia 
Criteria: 
• regular 
• Increasing HR up to 120 b/min. 
• Normal P wave  
• Normal QRS complex  
 
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2. Supra ventricular tachycardia (SVT)  
Criteria: 
• regular 
• Tachycardia  
• Unusual shape P wave  
• Normal QRS complex  
 
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3. Ventricular tachycardia (V tach) 
Criteria: 
• regular 
• Tachycardia 
• Wide bizarre QRS complex  
 
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4. Atrial flutter  
Criteria: 
• regular 
• tachycardia  
• saw teeth appearance  
• more than P wave for each QRS complex (2: 1), (3: 1) or even (4: 1). 
 
 
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regular Bradycardia 
1. 
sinus bradycardia 
criteria:  
• regular 
• bradycardia less than 60 b/min  
• normal P wave  
• normal QRS complex  
 
 
2. 
A.V nodal rhythm  
Criteria: 
 
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• regular 
• bradycardia 
• Normal QRS complex 
• Inverted P wave or absent P wave or occurring after QRS complex 
 
 
 
   
3. 
Idioventricular rhythm (IVR) 
A.V node does not allow electricity to go up to the atrium  
Criteria: 
• regular 
• bradycardia 
• Wide bizarre QRS complex  
• P-P interval different from R-R internal ( Idio ventricular dissociation ). 
 
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4. 
Sick sinus syndrome (SSS): 
Is a disease in which the Pace maker (SA node) becomes damaged and unable 
longer to generate normal heartbeats at the normal rate. 
 
 
 
 
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Ventricular Fibrillation 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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Summary :