What Are the Different Types of Heart Block?

First-degree heart block is the mildest form of heart block. With this type of heart block, the heart’s electrical signals slow as they travel between the atria and the ventricles. Though the change can be diagnosed with an electrocardiogram (ECG), you may not notice any symptoms.

First-degree heart block seldom progresses to more advanced heart block and does not usually require treatment. There can be a risk of complications such as the development of a heart rhythm disturbance (arrhythmia), which may require medications or devices to treat.

A 2021 study suggested that the risk factors for heart block include:

• being older
• being male
• having a metabolic disorder, such as diabetes
• having hypertension and a high body mass index (BMI)

A diagnosis of second-degree heart block means that there are occasional disruptions in the electrical signals that travel between the atria and ventricles. Second-degree heart block is broken down into two types:

• Mobitz type I: The signals move increasingly more slowly between heartbeats. In time, a beat is dropped.
• Mobitz type II: With this type of heart block, electrical signals may fail to reach the ventricles, resulting in randomly dropped heartbeats. However, there’s no steady slowing of electrical activity leading up to the disruption of signals.

Mobitz type I may have no noticeable symptoms, though you may notice your heart skipping a beat or other changes in your heart rhythm. This type of second-degree heart block usually doesn’t advance to third-degree heart block.

For Mobitz type II, symptoms may include:

• chest pain
• fainting (syncope)
• fatigue
• heart palpitations, or the sense that your heart skips a beat
• shortness of breath

Call 911 or get to an emergency room if you have any of these symptoms.

Mobitz type II usually develops in people with structural heart disease, such as valve disease, or a congenital heart defect, such as atrial septal defect. Mobitz type II often progresses to third-degree heart block, which is sometimes referred to as a complete heart block and requires treatment.

Third-degree heart block is the most serious type of heart block.

Electrical signals no longer move from the atria to the ventricles. This complete loss of communication between the heart’s upper and lower chambers can be fatal. Third-degree heart block is a medical emergency.

Symptoms of third-degree heart block can include:

• chest pain
• dizziness
• extreme tiredness
• an irregular heart rate
• shortness of breath
• fainting

These symptoms can be life threatening and require immediate medical attention.

An ECG records the heart’s electrical activity and is necessary to diagnose and differentiate the different types of heart block. These results could indicate first-degree or second-degree (Mobitz type I) heart block.

An ECG can also reveal whether there are disruptions in electrical activity (Mobitz type II) or whether electrical signals are no longer traveling from the atria to the ventricles (third-degree heart block).

A thorough diagnosis will also include:

• a review of your personal and family medical history
• a review of current symptoms and medications
• physical examination, including listening to the heart and lungs with a stethoscope

If an in-office ECG doesn’t detect changes to the heart’s electrical activity, a 24-hour mobile ECG, such as a Holter monitor, may be necessary. In some cases, an implantable loop recorder may be appropriate. This device is placed in the chest to record electrical activity for up to 3 years.

Treatment options

Regardless of the type of heart block, any medications or reversible causes that could be contributing to heart block should be addressed.

First-degree and Mobitz type I second-degree heart block often do not require treatment. However, if they’re causing significant symptoms or are at risk of progressing, a pacemaker may be recommended.

Third-degree heart block is a medical emergency and may require stabilization with medications such as atropine, dopamine, and epinephrine.

For a temporary solution, transcutaneous pacing is sometimes done. This involves placing electrodes on the chest to deliver electrical signals to the heart. The goal is to restore a regular heartbeat until a more permanent solution is available.

In some cases, a doctor will place a transvenous pacemaker until a reversible cause is addressed or a permanent pacemaker, if needed, can be inserted.

The long-term treatment option for second-degree heart block (Mobitz type II) and third-degree heart block is usually a pacemaker. This small, battery-powered device is implanted in the chest with wires (called leads) that run to your heart and help your heart beat at a normal rate and rhythm.

First-degree heart block and second-degree heart block (Mobitz type I) typically do not lead to any serious complications.

Depending on the type and severity of the conduction disturbance, medications or an implanted device (pacemaker) may be enough to manage the condition.

Because there is a higher risk of fainting with second-degree and third-degree heart block, complications such as head injuries and falls are much more likely.

Sudden cardiac arrest, which is often fatal, is a potential complication of second-degree heart block (Mobitz type II) and third-degree heart block. Third-degree heart block can also lead to low cardiac output. This is a state in which your heart is not able to effectively pump blood to the body.

Heart block usually develops when there has been some damage to the heart, from age-related scarring, a heart attack, or structural heart disease. While you can’t prevent a congenital heart defect, you may be able to lower your risk of heart block by protecting your heart health with some of these strategies:

• Exercise regularly: Get at least 150 minutes per week of moderate-intensity aerobic exercise or 75 minutes a week of vigorous exercise.
• Eat a heart-healthy diet: Follow a heart-healthy eating plan, such as the Mediterranean diet or the Dietary Approaches to Stop Hypertension (DASH) diet.
• Quit smoking: Smoking can negatively affect your heart in many ways. It can raise the risk of hypertension, arrhythmia, and atherosclerosis. Over time, these conditions can lead to heart disease.
• Manage stress: Try to keep your stress levels under control with healthy stress management techniques, such as meditation, breathing techniques, exercise, yoga, or tai chi.
• Prioritize sleep: Get 7 to 9 hours of sleep each night.
• Minimize alcohol consumption: Cut out alcohol or limit your intake to more than one drink per day for women, two drinks for men.
• Keep an eye on important heart health indicators: Work with a healthcare professional to keep your blood pressure, cholesterol, and blood glucose levels within healthy ranges. Also, get your BMI checked to ensure you’re at a moderate weight.

Heart block is an interruption of your heart’s electrical system. This condition can range from having no symptoms and not needing treatment, to a life threatening condition that requires emergency care.

While not all types of heart block are preventable, you can lower your risk and stay on top of your heart health by making lifestyle changes, such as getting regular exercise, eating a heart-healthy diet, and not smoking.

It’s also important to work with your doctor to make sure your blood pressure, cholesterol, blood glucose, and BMI levels stay within a healthy range.