Creator: Dr. Niharicka Gopalakrishnan
Published: 2022-12-27T18:32:21

A second-degree heart block is a condition in which the atrial impulse conduction is delayed or disrupted. Read the article to know more.

Written by

Dr. Niharicka Gopalakrishnan

Medically reviewed by

Dr. Sapkal Ganeshrao Patilba

December 27, 2022

February 8, 2024

What Is a Heart Block?

A heart is a muscular organ with four chambers, two on the top and the other below. The upper chambers are the right and left atrium, and the lower chambers are the right and left ventricles. The chambers of the heart are wired for electrical conduction, much like the electrical system in a house. The right and left bundle branches, the atrioventricular (AV) node, the bundle of His, Purkinje fibres, and the sinoatrial (SA) node or sinus node make up this system. With the help of highly specialized cells which make up the conduction pathways, the heart contracts rhythmically and pumps out blood with each heartbeat. When an atrial impulse is blocked or delayed within the heart’s conduction pathway, it gives rise to a medical condition, referred to as a heart block or atrioventricular (AV) node block.

What Are the Types of Heart Block?

Based on the severity of the nodal block, there are three degrees of heart block or atrioventricular (AV) block:

1. First-Degree Heart Block or First Degree Atrioventricular (AV) Block: It is technically not a heart block but more of a delay in the conduction of impulses. Every atrial impulse does reach the ventricles, but there is a significant delay in the process. It is the mildest form of heart block.

2. Second-Degree Heart Block or Second-Degree Atrioventricular (AV) Block: It is of two types, namely:

Type I or Mobitz Type I: Also known as Wenckebach’s atrioventricular (AV) block, this type of heart block refers to the state wherein each atrial impulse encounters a longer and longer delay until one of them does not make it through to the ventricles.

Type II or Mobitz Type II: Like in Mobitz I, the heart also drops a beat in Mobitz II, except this time, the conduction through the atrioventricular (AV) node is all or nothing. Either the atrial impulse goes through without delay or does not. Simply put, it means there is no progressive elongation of the PR interval in Mobitz II. In simple words, it means that the atrial impulses are blocked sporadically.

Third-Degree Heart Block: Third-degree AV block is a medical condition in which none of the electrical impulses are conducted through the AV node, leading to a complete heart block. When the ventricles recognize that none of the impulses are traveling to the AV node, they respond by generating an electrical rhythm called the ventricular escape rhythm. This happens because of the intrinsic property of the cardiac cells of automaticity. Since the atria and ventricles each have their own pacemakers, they now contract independently, and this process is known as atrioventricular (AV) dissociation. This desynchronization of the heart chambers reduces the cardiac output significantly, leading to syncope or sudden cardiac death.

How Does a Second-Degree Heart Block Represent Itself on an Electrocardiogram (ECG)?

Type I or Mobitz type I atrioventricular (AV) block demonstrates Wenckebach’s phenomenon. It refers to the progressive increase in the PR interval until all of a sudden: the heart drops a beat. The impulse conduction time extends and is followed by a non-conducted impulse or a dropped beat. Whereas in type II or Mobitz, type II AV block demonstrates a couple of normal PR intervals followed by a dropped beat.

What Are the Causes of Mobitz Type 1 Heart Block?

Causes of Mobitz type I or Wenckebach’s atrioventricular (AV) block are as follows:

Hyperkalemia (electrolyte imbalance which can alter membrane potential).
Medications (like beta-blockers, calcium channel blockers, Digoxin etc.).
Heart attack.
Myocarditis (inflammation of the heart muscles).
Endocarditis (infection to the inner layer of the heart).
Increased vagal tone (seen in athletes).

What Are the Causes of Mobitz Type 2 Heart Block?

Most individuals diagnosed with Mobitz type II heart block have an underlying cardiac disease and a left bundle branch block (LBBB). The most common causes of Mobitz type II are:

Myocardial infarction (heart attack).
Cardiomyopathies.
Myocarditis (inflammation of the heart muscles).
Endocarditis (infection to the inner layer of the heart).
Infiltrative and autoimmune disorders such as amyloidosis and sarcoidosis.
Inflammatory conditions such as Lyme disease and rheumatic fever.
Fibrosis or scarring of the cardiac tissue.
Cardiac surgery (for example, mitral valve repair).

What Are the Signs and Symptoms of Second-Degree Heart Block?

Similar to first-degree heart block, individuals with Mobitz type I do not exhibit any symptoms. Rarely, they might present with the following symptoms:

Lightheadedness.
Fatigue.

Conversely, individuals with Mobitz type II have symptoms associated with decreased cardiac output. They include the following:

Dyspnea (shortness of breath).
Chest pain.
Fatigue.
Heart palpitations.
Hypotension (decrease in blood pressure).
Syncope.

How Is a Second-Degree Heart Block Diagnosed?

A physician would advise for echocardiography (ECG or EKG) to confirm and diagnose an individual with a second-degree heart block. With the help of numerous electrodes (tiny sensors in the form of stickers attached to various parts of the body), an echocardiogram records the electrical signals from the heart, which helps identify the extra heartbeats and helps locate the origin of the extra heartbeat too. It is a rapid and painless test. The heartbeats can also be monitored using portable echocardiography devices, such as the Holter’s or an event monitor. A Holter’s monitor is used for a day or more, whereas an event monitor is worn for at least 30 days.

What Are the Complications Associated With a Second-Degree Heart Block?

Third-degree heart block or complete heart block.
Arrhythmias (irregular heartbeat).
Bradycardia (slow heart rate).
Cardiac arrest.

What Is the Treatment for Second-Degree Heart Block?

Mobitz type I is often benign and rarely progresses to third-degree heart block. On the other hand, Mobitz type II can be dangerous if not treated. Treatment involves identifying the root cause of the heart block. If no treatment modalities help, the physician may advise using a pacemaker. A pacemaker is a small implanted device that sends electrical impulses to keep the heartbeats regular.

Conclusion

Heart blocks can be both asymptomatic and symptomatic. The presentations vary significantly from one individual to another. As long as proper care is given as needed, all forms of heart blocks have a positive outlook.

Frequently Asked Questions

1. Is Second Degree Type 2 Heart Block a Serious Condition?

Yes. Second-degree type 2 heart block is an important and potentially serious condition. It is seen when electrical signals in the heart are partially blocked, leading to an irregular heartbeat. If not treated on time, the condition can progress to a complete blockage and cause symptoms like dizziness, fainting, or even cardiac arrest. It requires medical evaluation and management to minimize the risk of complications and ensure the heart functions properly.

2. Can Heart Block Be Treated with Medication?

Certainly! Heart block can be treated with medication in many cases. The specific medication prescribed depends on the type and severity of the heart block. Medications such as beta-blockers, calcium channel blockers, or cardiac glycosides may regulate the heart's electrical signals and restore a normal rhythm. However, in some instances, if the heart block is severe or medication is ineffective, other interventions like a pacemaker may be necessary to ensure proper heart function. Consulting with a healthcare professional for an accurate diagnosis and appropriate treatment options is important.

3. What Is the Primary Medication for Treating Heart Block?

The primary medication for treating heart block is based on the type and condition. The medications for heart block management include beta-blockers, calcium channel blockers, and cardiac glycosides. Beta-blockers help regulate the heart's electrical signals, calcium channel blockers help to relax and widen blood vessels, and cardiac glycosides strengthen the heart's contractions. However, the choice of medication is determined by the underlying cause and individual patient factors.

4. How Is Second-Degree Heart Block Typically Managed or Treated?

Second-degree heart block is typically managed or treated based on the individual's severity and symptoms experienced by the individual. Close monitoring may be recommended if the heart block is stable and not causing significant symptoms. However, if symptoms are present or the heart block worsens, medical interventions such as a pacemaker may be necessary to regulate the heart's electrical signals and restore a normal rhythm. A healthcare professional will determine The specific treatment approach based on the individual's unique circumstances.

5. What Is Considered a Normal Level of Heart Blockage?

A normal level of heart blockage is typically minimal or nonexistent. Ideally, the electrical signals should travel unimpeded through the heart's conduction system. However, if there is a blockage or delay in transmitting these signals, it can lead to heart rhythm abnormalities. The severity of heart blockage is typically assessed using diagnostic tests such as an electrocardiogram (ECG) or Holter monitor. It is recommended that a person should consult with a specialist who can evaluate the degree of heart blockage and recommend appropriate management strategies based on individual circumstances.

6. Is Engaging in Exercise or Physical Activity with a Heart Block Safe?

Engaging in exercise or physical activity with heart block should be approached with caution and under the guidance of a healthcare professional. Exercise safety depends on the type and severity of the heart block and individual factors. Individuals with heart block may be advised to limit their physical exertion or avoid certain high-intensity activities. However, mild forms of heart block may not pose significant risks during exercise. It is crucial to consult with a heart specialist who can assess your specific condition and provide personalized recommendations regarding exercise and physical activity.

7. What Measures Can Be Taken to Prevent Heart Block?

Various measures can be taken to help prevent heart block. These include maintaining a healthy lifestyle, such as adopting a balanced diet, engaging in regular physical activity, avoiding tobacco and excessive alcohol consumption, and managing underlying conditions contributing to heart blocks, such as high blood pressure and coronary artery disease. Regular check-ups detect any early signs of heart block and ensure prompt intervention. These preventive measures can significantly reduce the risk of developing heart block and promote overall health.

8. Can Regular Walking Help Reduce Heart Blockage?

Regular walking can play a beneficial role in reducing heart blockage. It promotes cardiovascular health by improving blood circulation. It strengthens the heart muscle and reduces the risk of plaque buildup in the arteries. Walking helps maintain a healthy weight, lowers blood pressure, and improves overall heart function. Regular walking into a well-rounded exercise routine can reduce heart blockage and promote heart health.

9. Can Stress Be a Contributing Factor to Heart Block?

While stress may not directly cause heart block, it can exacerbate existing heart conditions and contribute to the development of heart block. Stress increases blood pressure and heart rate, which may strain the heart's electrical system. This can disrupt the normal conduction of electrical signals and contribute to heart rhythm abnormalities, including heart block. Managing stress through relaxation techniques, regular exercise, and seeking support from healthcare professionals or mental health providers can reduce its impact on heart health and potentially decrease the risk of heart block.

10. What Is the Life Expectancy for Someone with Second-Degree Heart Block?

The life expectancy for someone with second-degree heart block varies depending on various factors, including the underlying cause, overall health, and individual circumstances. If the heart block is well-managed and treated appropriately, individuals can live long and fulfilling lives. However, individuals with heart block need to receive regular medical monitoring, follow their prescribed treatment plan, and make necessary lifestyle adjustments to optimize their heart health. Consulting with a healthcare professional is crucial for personalized guidance and addressing any specific concerns related to life expectancy with second-degree heart block.

11. Which Medications Are Known to Cause Mobitz Type 1 Heart Block?

Medications that can cause Mobitz type 1 heart block include certain cardiac medications such as beta-blockers, calcium channel blockers, and antiarrhythmic drugs. These medications affect the heart's electrical conduction system. Not everyone taking these medications will develop Mobitz type 1 heart block, and the risk may vary depending on the individual's overall health, dosage, and duration of medication use. It is crucial to cooperate with a healthcare professional who can monitor the effects of these medications and adjust the treatment plan accordingly.

12. What Is the Most Effective Remedy for Heart Block?

The most effective remedy for heart block depends on the specific type and condition severity. In many cases, the primary treatment for heart block involves using a pacemaker. A pacemaker is a small, surgically implanted device to regulate the heart's electrical signals and ensure a proper heartbeat. The pacemaker sends electrical impulses to the heart when needed, helping maintain a regular rhythm. Pacemakers are highly effective in managing heart block and can significantly improve a person's quality of life. However, the decision to use a pacemaker is made individually, considering the patient's unique circumstances and medical evaluation.

13. Is Mobitz Type 1 Heart Block Curable?

Mobitz Type 1 heart block, also known as Wenckebach block, is characterized by a progressive delay in transmitting electrical signals between the upper and lower chambers of the heart. While it is not typically considered curable, management and treatment options are available to control symptoms and minimize the risk of complications. These may include medication adjustments, lifestyle modifications, and close condition monitoring. In some cases, the placement of a pacemaker may be necessary to regulate the heart's electrical signals and ensure a normal heart rhythm. Consulting with a healthcare professional is essential to determine the most appropriate management approach for Mobitz Type 1 heart block.

14. What Is Another Term Used to Refer to Mobitz Type 1 Heart Block?

Another term for Mobitz Type 1 heart block is "second-degree AV block, Type 1." This condition is characterized by a progressive lengthening of the PR interval on an electrocardiogram (ECG), eventually leading to a dropped beat. The term "Wenckebach block" is also commonly used to describe this specific type of heart block, named after the doctor who first explained it. The terms refer to the same underlying condition of progressive conduction delay and blockage in the heart's electrical system.

15. Is Mobitz Type 1 Heart Block an Indication for a Pacemaker?

Yes, Mobitz Type 1 heart block can indicate a pacemaker. In cases where the heart block is symptomatic, causing significant symptoms or impairing the heart's ability to function properly, a pacemaker may be recommended. A pacemaker is a small, surgically implanted device to regulate the heart's electrical signals and ensure a proper heartbeat. It monitors the heart's activity continuously and delivers electrical impulses to maintain a regular rhythm. The decision to implant a pacemaker for Mobitz Type 1 heart block is based on individual factors.

16. What Are the Treatment Options for Mobitz Type 1 Heart Block?

The treatment options for Mobitz Type 1 heart block depend on the severity of the condition and the presence of symptoms. In mild cases without symptoms, close monitoring may be recommended to assess any progression or changes in the heart's conduction system. If symptoms are present or the heart block is more severe, placing a pacemaker is often considered the primary treatment. A pacemaker helps regulate the heart's electrical signals and ensures a regular heartbeat. The treatment decision is made individually, considering the patient's condition and medical evaluation. Consulting with a healthcare professional is essential to determine the most suitable treatment approach for Mobitz Type 1 heart block.

17. Is It Safe to Exercise with First-Degree Heart Block?

In most cases, individuals with first-degree heart block can safely exercise. First-degree heart block typically does not cause significant symptoms or impair the heart's ability to function. However, consulting with a healthcare professional before starting or modifying an exercise routine is recommended. They can assess your condition, evaluate underlying factors, and provide personalized recommendations. Monitoring your heart rate during exercise and paying attention to any symptoms is also important. If you experience any concerning symptoms during exercise, it is advisable to seek medical attention promptly.

18. Can Individuals with Heart Block Lead a Normal Life?

Individuals with heart block can lead a normal life with proper management and care. The impact of heart block on daily life will depend on the severity and the presence of symptoms. Following a treatment plan prescribed by a healthcare professional, such as taking prescribed medications and undergoing regular check-ups, is crucial for maintaining heart health. Lifestyle modifications, such as adopting a heart-healthy diet, and engaging in regular physical activity within recommended limits, can also contribute to a normal and fulfilling life with heart block.