How to Identify Heart Blocks
Understand what the term "heart block" refers to., Recognize the symptoms of a heart block., Identify a first degree heart block., Know what causes a second degree heart block., Recognize Mobitz type I., Know how to identify a Mobitz type 2 block...
Step-by-Step Guide
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Step 1: Understand what the term "heart block" refers to.
The term heart block refers to an AV block or an atrio-ventricular block.
This is when there is some obstacle blocking electrical signals between the upper and lower chambers of the heart.
There are three degrees of AV block according to severity
- first degree, second degree and third degree.
Second degree heart blocks have two subtypes. -
Step 2: Recognize the symptoms of a heart block.
First degree heart block usually does not produce any symptoms.
Second and third degree heart blocks may also be asymptomatic.
However, when the condition persists for a long time, heart failure may occur.
Dizziness and fainting may occur due to a temporary interruption in the blood supply to the brain.
In complete heart block, ventricles beat very slowly which may lead to heart failure.
In this case, you may experience fatigue, coughing, shortness of breath, chest pain, leg swelling etc.
These symptoms indicate serious illness and require prompt medical attention. , A first degree heart block occurs when the electrical signals passing between the atria and the ventricles (the upper and lower chambers of the heart) become slower than normal.
A first degree heart block can be identified on on an ECG by a longer, flatter line between the P and R waves.Causes of first degree heart block include drugs (such as beta blockers, calcium channel blockers, digoxin and amiodarone), heart attack (or myocardial infarction), age-related degeneration of conduction system, electrolyte imbalance (particularly potassium), increased parasympathetic activity etc.
First degree heart blocks are usually asymptomatic and do not require treatment. , A second degree heart block occurs when the electrical signals passing between the atria and the ventricles slow down significantly, and some of the signals never even reach the ventricles.
When electrical signals do not reach the ventricles, the ventricles fail to contract.
This prevents blood from being pumped around the body, to the lungs and other important organs.
The are two subtypes of second degree heart blocks
- Mobitz type I and Mobitz type II. , With a Mobitz type 1 heart block, the electrical signals moving from the atria to the ventricles become progressively slower with each heartbeat, until the heart eventually skips a beat.
Mobitz type 1 is identified on an ECG as follows:
As the electrical signals slow, a line appears between the P and QRS waves.
This line is known as a PR interval.
These lines get progressively longer until the heart skips a beat, at which point there is no QRS wave following the next P wave.The causes of a Mobitz type 1 block are the same as for a first degree block.
Sufferers of a type 1 heart block may experience a little dizziness but they usually won't require treatment.
This type of block is less severe than a Mobitz type 2 block. , In a Mobitz type 2 block some of the electrical signals passing from the atria to the ventricles are blocked, resulting in a skipped heart beat.
Unlike with Mobitz type 1, the pattern of blocked electrical signals is unpredictable.
Mobitz type 2 is identified on an ECG as follows:
At first, the ECG will appear normal, as the QRS wave follows the P wave at regular intervals.
However, once an electrical signal fails to pass into the ventricles, the QRS wave will disappear completely.Common causes of this type of heart block are heart attack, heart surgery and age-related degeneration of the conduction system.
Mobitz type 2 is more serious than Mobitz type 1, and in some cases a temporary pacemaker will be required if the patient develops significant bradycardia (heart rate below 60 beats/min). , In a third degree heart block, all of the electrical signals passing between the atria and ventricles are blocked.
When this happens, it is referred to as a complete heart block or a complete AV block.
In order for the ventricles to continue contracting and pumping blood around the body, the heart has a special back-up system of electrical signals which kicks into action in case of blockages.
However, this back-up system operates at a slower pace, which means the contraction of the ventricles isn't in sync with the contraction of the atria.
This lack of co-ordination makes a third degree heart block easier to identify on an ECG, as it interferes with the normal pattern.
The P waves and QRS waves are not coordinated as they normally are, and the P waves show up at more frequent intervals.A third degree heart block is the most serious type of heart block and requires emergency treatment.
If left untreated, it could lead to sudden cardiac arrest.
The treatment for a third degree block involves the insertion of a permanent pacemaker.
A pacemaker is a battery powered device which is attached to the chest.
The device is connected to the heart by wires.
The device discharges rhythmic electrical signals to excite the ventricular muscles, causing them to contract. -
Step 3: Identify a first degree heart block.
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Step 4: Know what causes a second degree heart block.
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Step 5: Recognize Mobitz type I.
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Step 6: Know how to identify a Mobitz type 2 block.
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Step 7: Understand what a third degree heart block involves.
Detailed Guide
The term heart block refers to an AV block or an atrio-ventricular block.
This is when there is some obstacle blocking electrical signals between the upper and lower chambers of the heart.
There are three degrees of AV block according to severity
- first degree, second degree and third degree.
Second degree heart blocks have two subtypes.
First degree heart block usually does not produce any symptoms.
Second and third degree heart blocks may also be asymptomatic.
However, when the condition persists for a long time, heart failure may occur.
Dizziness and fainting may occur due to a temporary interruption in the blood supply to the brain.
In complete heart block, ventricles beat very slowly which may lead to heart failure.
In this case, you may experience fatigue, coughing, shortness of breath, chest pain, leg swelling etc.
These symptoms indicate serious illness and require prompt medical attention. , A first degree heart block occurs when the electrical signals passing between the atria and the ventricles (the upper and lower chambers of the heart) become slower than normal.
A first degree heart block can be identified on on an ECG by a longer, flatter line between the P and R waves.Causes of first degree heart block include drugs (such as beta blockers, calcium channel blockers, digoxin and amiodarone), heart attack (or myocardial infarction), age-related degeneration of conduction system, electrolyte imbalance (particularly potassium), increased parasympathetic activity etc.
First degree heart blocks are usually asymptomatic and do not require treatment. , A second degree heart block occurs when the electrical signals passing between the atria and the ventricles slow down significantly, and some of the signals never even reach the ventricles.
When electrical signals do not reach the ventricles, the ventricles fail to contract.
This prevents blood from being pumped around the body, to the lungs and other important organs.
The are two subtypes of second degree heart blocks
- Mobitz type I and Mobitz type II. , With a Mobitz type 1 heart block, the electrical signals moving from the atria to the ventricles become progressively slower with each heartbeat, until the heart eventually skips a beat.
Mobitz type 1 is identified on an ECG as follows:
As the electrical signals slow, a line appears between the P and QRS waves.
This line is known as a PR interval.
These lines get progressively longer until the heart skips a beat, at which point there is no QRS wave following the next P wave.The causes of a Mobitz type 1 block are the same as for a first degree block.
Sufferers of a type 1 heart block may experience a little dizziness but they usually won't require treatment.
This type of block is less severe than a Mobitz type 2 block. , In a Mobitz type 2 block some of the electrical signals passing from the atria to the ventricles are blocked, resulting in a skipped heart beat.
Unlike with Mobitz type 1, the pattern of blocked electrical signals is unpredictable.
Mobitz type 2 is identified on an ECG as follows:
At first, the ECG will appear normal, as the QRS wave follows the P wave at regular intervals.
However, once an electrical signal fails to pass into the ventricles, the QRS wave will disappear completely.Common causes of this type of heart block are heart attack, heart surgery and age-related degeneration of the conduction system.
Mobitz type 2 is more serious than Mobitz type 1, and in some cases a temporary pacemaker will be required if the patient develops significant bradycardia (heart rate below 60 beats/min). , In a third degree heart block, all of the electrical signals passing between the atria and ventricles are blocked.
When this happens, it is referred to as a complete heart block or a complete AV block.
In order for the ventricles to continue contracting and pumping blood around the body, the heart has a special back-up system of electrical signals which kicks into action in case of blockages.
However, this back-up system operates at a slower pace, which means the contraction of the ventricles isn't in sync with the contraction of the atria.
This lack of co-ordination makes a third degree heart block easier to identify on an ECG, as it interferes with the normal pattern.
The P waves and QRS waves are not coordinated as they normally are, and the P waves show up at more frequent intervals.A third degree heart block is the most serious type of heart block and requires emergency treatment.
If left untreated, it could lead to sudden cardiac arrest.
The treatment for a third degree block involves the insertion of a permanent pacemaker.
A pacemaker is a battery powered device which is attached to the chest.
The device is connected to the heart by wires.
The device discharges rhythmic electrical signals to excite the ventricular muscles, causing them to contract.
About the Author
Sara Sanchez
A seasoned expert in lifestyle and practical guides, Sara Sanchez combines 2 years of experience with a passion for teaching. Sara's guides are known for their clarity and practical value.
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