Decoding Heart Blocks: Understanding ECG Reports

Medically Reviewed by Dr. Aman Priya Khanna
Written by Sparshi Srivastava, last updated on 3 January 2024| min read
Decoding Heart Blocks: Understanding ECG Reports

Quick Summary

  • An electrocardiogram (ECG or EKG) is a helpful diagnostic instrument for recording the electrical activity of the heart. Heart block ECG is one of the various cardiac conditions that doctors detect with this tool.
  • Early and accurate detection of heart block can lead to appropriate healthcare measures and improved outcomes.
  • In this blog, we will understand heart block ECG findings and information about the interpretation of the changes.

An electrocardiogram (ECG or EKG) is a helpful diagnostic instrument for recording the electrical activity of the heart. Heart block ECG is one of the various cardiac conditions that doctors detect with this tool. 

Early and accurate detection of heart block can lead to appropriate healthcare measures and improved outcomes. In this blog, we will understand heart block ECG findings and information about the interpretation of the changes. Want to know what the procedure and prominent cardiac issues are? Then, continue reading.

About ECG

ECG is a non-invasive examination in which electrodes are placed on the chest to observe the electrical impulses generated by the heart. The conductive activity regulates cardiac rhythm, and changes in the same can indicate various cardiovascular problems.

Doctors can analyse the condition of the heart by examining the graphical representation of the impulses in a standard ECG report. The key elements of an ECG report for evaluating the electrical activity are:

  1. P Wave: It is the initial wave on an ECG that indicates atrial depolarisation (contraction). It reflects the electrical activity in the atria. A duration of around 0.06 to 0.12 seconds (60-120 ms) is considered normal.
  2. QRS Complex: This represents ventricular depolarisation (contraction). It is the biggest and most noticeable wave on the ECG. It should have a duration of less than 0.12 seconds (120 ms).
  3. PR Interval: This indicates the time it takes for the electrical impulse to move from the atria to the ventricles (duration between the start of the P wave and QRS complex).  It should be between 0.12 to 0.20 seconds (120-200 ms).
  4. T Wave: This wave type represents ventricular repolarisation (relaxation). It reflects the ventricle restoration. They should be upright in most leads and not excessively peaked or inverted.
  5. ST Segment: It is the line that connects the QRS complex to the T wave, denoting the early repolarisation of the ventricle.
  6. Heart Rate: The number of heartbeats per minute is calculated from the R-R interval. The average heart rate for adults at rest ranges from 60 to 100 beats per minute (bpm). For children and athletes, it can be lower. 
  7. Rhythm Analysis: Determines the consistency of the electrical activity of the heart.

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What is a Heart Block?

The electrical system of the heart helps in significantly coordinating the contraction of the atria and ventricles. This allows blood to flow effectively through the heart. 

When the normal electrical signalling between the upper (atria) and lower (ventricles) cardiac chambers is disrupted. It leads to a heart block, also known as an atrioventricular (AV) block.

Identifying Heart Blocks on an ECG Report

To understand heart block ECG findings, doctors look for specific ECG patterns and changes in the PR interval. Here's what to watch for in each type of heart block:

First-Degree Heart Block ECG:

A delay in the transmission of cardiac impulses from the atria to the ventricles characterises a first-degree heart block. Specifically, it is seen as a prolonged PR interval on the ECG.

  1. The heart block ECG finding shows that PR intervals consistently increased.
  2. The PR interval is significantly longer than the typical range.
  3. Every atrial impulse is eventually transferred to the ventricles. However, there is a delay in transmission.

Second-Degree Heart Block ECG:

Partial conduction blocks between the atria and ventricles characterise second-degree heart blocks. There are two main subtypes of second-degree heart block: Mobitz I (Wenckebach) and Mobitz II.

In Mobitz I (Wenckebach):

  1. Observe the PR interval gradually increasing with each beat until a heartbeat is dropped.
  2. The PR interval stretches then gets shortened abruptly, resulting in a missed ventricular rhythm.
  3. Multiple P waves with a single QRS complex resemble a "group beating" illustration.

In Mobitz II:

  1. The PR interval remains steady. However, there are a few missing beats here and there.
  2. It is distinguished by a constant PR interval and irregularly absent ventricular beats.

Third Degree Heart Block (Complete Heart Block ECG):

The most severe form of heart block is referred to as complete or third degree block. There is a complete dissociation between the atrial and ventricular electrical activity. 

  1. The atria and ventricles beat independently, with no rhythmic link.
  2. The electrocardiogram (ECG) may reveal two different and independent rhythms: atrial and ventricular.
  3. The ventricular pace could be significantly slower than the atrial rate.

Note: First-degree heart blocks usually do not require treatment. However, third-degree heart blocks may need a pacemaker to regulate the cardiac rhythm (by improving atrioventricular coordination). 

Lifestyle Changes Post Heart Block Detection on ECG

After detecting a heart block through ECG, it's essential to consider lifestyle changes to ensure better heart health and manage the symptoms. Here are some general lifestyle changes to consider:

  1. Regular Medical Follow-ups: Schedule consultations with an expert cardiologist to consistently monitor cardiac functioning. It also helps in preventing the progression of heart block.
  2. Medication Adherence: If recommended, take medicines as directed to regulate heart rate and rhythm.
  3. Healthy Diet: Consume a heart-healthy diet rich in fruits, vegetables, whole grains, proteins, and low-fat dairy products. Limit your salt intake to help control your blood pressure.
  4. Weight Control: Individuals must maintain a healthy weight. This helps prevent heart strain and the development of severe health complexities.
  5. Exercise Regularly: Engage in moderate-intensity physical activities regularly, as directed by your doctor. Overexertion and high-intensity workouts should be avoided.
  6. Limit Caffeine and Alcohol: These should be reduced or eliminated as they can cause or aggravate arrhythmias.
  7. Smoking Cessation: If you smoke, quitting is important. Such toxic substances get deposited on the atrial lining,  promoting plaque formation and cardiovascular constriction. Thus increasing the risk of heart disease and arrhythmias.


ECGs remain a cornerstone in the diagnosis and management of cardiac conditions, including heart blocks. To reduce the risk of heart blocks and related complications, regular check-ups and a heart-healthy lifestyle are necessary.

If you ever receive an ECG report or are concerned about your cardiac health, consult HexaHealth. Professionals at HexaHealth can explain the findings and recommend appropriate treatment or further tests. Get in touch now!

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Frequently Asked Questions

A heart block appears on an ECG as a prolonged PR interval. It is the time it takes for electrical impulses travelling from the atria to the ventricles.

A complete heart block shows on an ECG as a clear dissociation between the atrial and ventricular rhythms. The P waves (atrial activity are not synchronised with the QRS complexes. This indicates that the atria and ventricles are beating independently, causing irregularity in the heartbeats.

ECG patterns that indicate a heart block include:

  1. First-Degree Heart Block: Prolonged PR interval.
  2. Second-Degree Heart Block (Mobitz I/Wenckebach): Progressive prolongation of PR interval leading to a dropped beat (group beating).
  3. Second-Degree Heart Block (Mobitz II): Intermittent dropped beats with a constant PR interval.
  4. Third-Degree (Complete) Heart Block: Complete dissociation between atrial and ventricular rhythms, leading to two unrelated rhythms.

An AV (Atrioventricular) block is confirmed via ECG by observing a prolonged PR interval in the ECG waveform. The PR interval represents the time it takes for electrical impulses to travel from the atria to the ventricles.

To read a heart block on an ECG:

  1. First-Degree Heart Block: Observe a prolonged PR interval.
  2. Second-Degree Heart Block (Mobitz I): Notice a gradually increasing PR interval until a heartbeat is missed.
  3. Second-Degree Heart Block (Mobitz II): Identify intermittent dropped beats without PR interval changes.
  4. Third-Degree (Complete) Heart Block: Recognize complete dissociation between atrial and ventricular rhythms with no coordination.

No, ECG (Electrocardiogram) is a diagnostic tool for detecting heart blocks. However, confirmation and further evaluation often require additional tests, such as a coronary angiogram.

Yes, different degrees of heart blocks are visible on an ECG. It can show distinct patterns and changes in the PR interval and rhythm. This allows doctors to identify and classify the type and severity of the heart block.

First-degree heart block on an ECG appears as a consistently prolonged PR interval. This indicates a delay in transmitting electrical impulses from the atria to the ventricles.

A third-degree (complete) heart block is identified on an ECG by the complete dissociation between the atrial and ventricular rhythms. This results in two separate and unrelated rhythms on the ECG with no coordination between them.

The key difference between left and right bundle branch blocks on an ECG is in the QRS complex.

  1. Left Bundle Branch Block (LBBB): Widened QRS complex and slurred S waves in the lateral leads.
  2. Right Bundle Branch Block (RBBB): A characteristic "rabbit ears" pattern in V1 and V2, where the RSR waves appear.

In heart block cases, ECG intervals, particularly the PR interval, are indicative of the degree and severity of the block:

  1. First-Degree Heart Block: PR interval is consistently prolonged.
  2. Second-Degree Heart Block (Mobitz I): PR interval progressively lengthens until a beat is dropped.
  3. Second-Degree Heart Block (Mobitz II): PR interval remains constant, with intermittent dropped beats.
  4. Third-Degree (Complete) Heart Block: No correlation between the atrial and ventricular rhythms, as they beat independently.

Yes, heart blocks can be temporary and may not always appear on an ECG. This is because they can come and go, making them challenging to detect during a single ECG recording.

When reviewing an ECG report for heart block severity, look for the following key indicators:

  1. PR Interval Duration, Consistency, and Elongation
  2. Number of Dropped Beats
  3. Atrioventricular (AV) Dissociation
  4. Relationship Between Atrial and Ventricular Rhythms

Yes, specific ECG leads, such as PR interval exceeding 0.20 without interrupting with atrioventricular conduction are indicative of heart blocks.

An ECG alone may suggest the presence of a heart block. However, a definitive diagnosis typically requires additional clinical evaluation and testing.

ECGs can provide information about heart blocks and their type, but they may not always reveal the underlying cause. Further tests and medical evaluation are often needed to determine the cause of heartblocks.

Professionals differentiate heart blocks from other ECG issues by analysing the pattern of PR interval prolongation. Also, they check the relationship between atrial and ventricular rhythms. Heart blocks exhibit specific PR interval changes and disruptions in this relationship.

A normal heart should not have any block in the electrical conduction system. Thus, a "0% block" is considered normal.

Treatment for heart block based on ECG findings may include:

  1. First-Degree Heart Block: Typically, no specific treatment, but underlying causes are addressed.
  2. Second-Degree Heart Block (Mobitz I): Usually no treatment, close monitoring.
  3. Second-Degree Heart Block (Mobitz II): May require a pacemaker if symptoms or high-degree block.
  4. Third-Degree (Complete) Heart Block: Almost always requires a pacemaker due to complete atrioventricular dissociation.

Yes, an ECG can monitor the effectiveness of heart block treatment. This is done by assessing changes in the cardiac electrical conduction and rhythm over time.

After heart block detection on an ECG, consider the following precautions and lifestyle changes:

  1. Medication Adherence
  2. Regular Medical Check-ups
  3. Heart-Healthy Diet
  4. Weight Management
  5. Controlled Blood Pressure
  6. Moderate Exercise
  7. Stress Reduction

The results of a heart block can include:

  1. Bradycardia (slow heart rate)
  2. Fainting or syncope
  3. Dizziness or lightheadedness
  4. Fatigue
  5. Chest pain or discomfort
  6. Shortness of breath


All the articles on HexaHealth are supported by verified medically-recognized sources such as; peer-reviewed academic research papers, research institutions, and medical journals. Our medical reviewers also check references of the articles to prioritize accuracy and relevance. Refer to our detailed editorial policy for more information.

  1. Introduction to ECG [Internet].
  2. Top strategies to prevent heart disease [Internet]. Mayo Clinic. link
  3. Kashou AH, Amandeep Goyal, Nguyen T, Lovely Chhabra. Atrioventricular Block [Internet]. StatPearls Publishing;
  4. Levis J. ECG Diagnosis: Complete Heart Block. The Permanente Journal. 2011 Apr 1;15(2).link

Updated on : 3 January 2024

Disclaimer: The information provided here is for educational and learning purposes only. It doesn't cover every medical condition and might not be relevant to your personal situation. This information isn't medical advice, isn't meant for diagnosing any condition, and shouldn't replace talking to a certified medical or healthcare professional.


Dr. Aman Priya Khanna

Dr. Aman Priya Khanna

MBBS, DNB General Surgery, Fellowship in Minimal Access Surgery, FIAGES

12 Years Experience

Dr Aman Priya Khanna is a well-known General Surgeon, Proctologist and Bariatric Surgeon currently associated with HealthFort Clinic, Health First Multispecialty Clinic in Delhi. He has 12 years of experience in General Surgery and worke...View More


Sparshi Srivastava

Sparshi Srivastava

B.Tech Biotechnology (Bansal Institute of Engineering and Technology, Lucknow)

2 Years Experience

An ardent reader, graduated in B.Tech Biotechnology. She was previously associated with medical sciences secondary research and writing. With a keen interest and curiosity-driven approach, she has been able to cont...View More

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