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What is Heart Block?

Electrical signals generated in the heart cause it to contract and beat in order to pump blood throughout the body. An electrical conduction system helps transmit these signals throughout the heart chambers, atria and ventricles. When the heart beats slowly or irregularly as a result of electrical signal interruption, it is called heart block and affects the flow of blood from the heart.

Types of Heart Block

First-degree heart block: The electrical impulses are slowed as they pass through the conduction system, but all signals reach the ventricles. It does not cause any symptoms or problems. First-degree heart block is common in well-trained athletes as they have slow resting heart rates

Second-degree heart block: There are two types.

Type-I: This is also called Mobitz Type I or Wenckebach's AV block. The electrical signals get slower until the heart skips a beat. It is seen in a highly relaxed state and during sleep. It rarely causes adverse symptoms.

Type-II: Some of the electrical impulses are unable to reach the ventricles, resulting in irregular heart rhythm. This condition is less common compared to type I and is more serious. Individuals with type II second-degree heart block may have a slower heartbeat than normal.

Third-degree heart block: It is also called complete heart block as none of the electrical impulses from the upper chambers (atria) reaches the lower chambers (ventricles).

Causes of Heart Block

Heart block can be present from birth(congenital) or may develop over one’s lifetime (acquired). Infants with developmental heart defects or autoimmune conditions have an increased risk of having a heart block from birth.

Causes of acquired heart block include:

  • Surgery that affects the heart’s electrical system
  • Changes in your genes
  • Damage from a heart attack
  • Damage to one of the conducting branch bundles, which can cause uncoordinated ventricular contractions and an abnormal heartbeat
  • Heart problems like clogged arteries, inflammation of the heart muscle, and heart failure
  • Muscle disorders or other diseases
  • Certain medicines


People with first-degree heart block may not experience any symptoms. Common symptoms of heart block include:

  • Fainting (syncope)
  • Dizziness or lightheadedness
  • Shortness of breath
  • Reduced exercise capacity
  • Slow or irregular heartbeat
  • Palpitations
  • Pain or discomfort in the chest

Diagnosis of Heart Block

Your doctor will review your medical history and check your overall health. You will be asked about:

  • Family history of heart disease or heart block
  • Medicines you are taking
  • Any habits of smoking or illegal drugs

A physical examination is performed. Diagnostic tests for heart block include:

  • Electrocardiogram (ECG): This test records the heart’s electrical activity on a graph in a wave pattern. The heart rate, rhythm, and timing of the electrical signals can be determined by studying the wave pattern. It can also identify which branch of your heart’s conducting system is affected.
  • Holter Monitor: A portable device that records your heart rhythm and provides information about the heart’s electrical activity over a period of 1-2 days. The person wears the monitor under their clothing and maintains a diary of his or her activities during this period. Your doctor analyzes the information in order to make a diagnosis.
  • Echocardiogram: This test uses sound waves to create images allowing your doctor to see the heart muscles and valves.
  • Electrophysiology Study: In this test, thin flexible wires are placed into the heart’s surface to accurately record the heart’s electrical activity. This study uses tiny electrical shocks to determine the cause and the origin of the abnormal rhythm.

Treatment for Heart Block

The right treatment for heart block depends on the seriousness of the condition and whether it is associated with any symptoms.

  • First and second-degree heart block does not require any treatment, but some serious cases of second-degree heart block may be treated with a pacemaker. A pacemaker is a small device implanted below the skin beneath the collarbone and connected to a pacing wire positioned inside the heart. This delivers a small electrical impulse to trigger the heart to beat when it is too slow.
  • Third-degree or complete heart block is treated with a pacemaker since the heart is no longer able to rhythmically contract due to the complete blockage of the electrical signals.
  • Your doctor may recommend anti-arrhythmic drugs, which control the electrical signals to the heart and help prevent irregular or rapid heart rhythms.

Prevention of Heart Block

A healthy lifestyle helps overall good health, including that of the heart. You are advised to observe the following:

  • Exercise regularly
  • Eat a well-balanced diet
  • Avoid smoking
  • Understand the risks of your medicines and review them with your doctor to reduce the risk of medicine-induced heart block
  • Talk with your doctor before taking any herbal supplements or new medicines, especially if you have risk factors for heart block


Signet Heart Group
2800 North Highway 75
Sherman, Texas 75090


Tel: | Fax:

Practice Hours: M-F 8am – 5pm

  • American Board of Internal Medicine
  • National Board of Echocardiography
  • Certification Board of Nuclear Cardiology
  • American Board of Vascular Medicine