Atrioventricular Block

Basic Facts

  • Atrioventricular Block, also known as "AV block" or simply "heart block". This is when electrical signals between the upper chambers (atria) and lower chambers (ventricles) aren't getting through properly, causing a delay or "block" in the heart's normal rhythm. 
  • It is an electrical issue, not necessarily a plumbing issue.
  • Mild types of heart block can cause the heart to beat more slowly than normal or to skip beats. More serious types can cause the heart to stop beating. Without emergency treatment, serious heart block can be fatal.
Implantable Devices

3 types of heart block: 

  1. 1st degree AV block- delay in signal from atria to ventricles, no symptoms.

  2. 2nd degree AV block [2 types] – partial or intermittent interruption in signal from atria to ventricles; rare symptoms, but could cause lightheadedness, fatigue, shortness of breath, and/or chest pain.

  3. 3rd degree AVB – complete interruption in signal from atria to ventricles; nearly all symptoms of lightheadedness, fatigue, shortness of breath, and/or chest pain, but it can be more severe. In some cases, third-degree heart block can be life-threatening. 


Heart block symptoms can vary according to its type, frequency, duration, and whether underlying structural heart disease is present. Heart block can contribute to a slower than normal heartbeat (bradycardia) People with bradycardia may experience the following: 

  • Dizziness or light-headedness 

  • Low blood pressure 

  • Palpitations (the sensation of skipped beats) 

  • Fatigue 

  • Syncope (fainting) 

  • Sudden death 

Heart block may occur at any age, but half of cases are due to changes as we age. 

  • Some drugs can cause milder forms of heart block:  Beta-blockers 

  • Calcium channel blockers (verapamil more so than diltiazem) 

  • Digoxin 

  • Amiodarone 

  • Adenosine (used at hospitals in emergency situations) 

Certain diseases can cause heart block, including: 

  • Endocarditis (infection inside the heart), 

  • Myocarditis (inflammation of heart muscle tissue) 

  • Lyme disease 

  • Lenegre or Lev disease (degeneration of the conduction system with age, sometimes genetic) 

  • Coronary heart disease/Heart attack

  • Sarcoidosis 

  • Muscular dystrophy 

  • Electrolyte abnormalities 

Some kinds of heart block can be caused by an increased vagal tone. The vagus nerve controls involuntary bodily functions including heart rate. When it is stimulated, such as during nausea, vomiting, or straining with a bowel movement, it can cause an abnormally slow heart rate.  

People who have undergone corrective heart surgery may also develop heart block. 

 

 

Diagnosis can be difficult because heart block may be unpredictable and brief. In addition to taking a person's medical history, listening to the patient describe symptoms, and conducting a physical examination, a provider may also recommend: 

  • ECG – noninvasive test, stickers attached to wires placed on the chest, provides a 6 second “snapshot” of heart’s electrical activity. Can be done at a visit. Can show the block if it is occurring at that time. 

  • Holter/Cardiac ambulatory monitoring – wearable ECG sticker that can record the heart's activity constantly for days to weeks, think of it as a “movie” rather than a “snapshot”. Monitor can be applied at home or at a visit. It is paired with a provided smartphone that stores/sends data. Worn 24/7. Returned via UPS. 

  • Implantable Loop Recorder – used to diagnose patients with recurring or unexplained arrhythmia episodes, syncope, or stroke. Small recorder (flat 2” device) is placed just under skin. It pairs with a “box” on nightstand that sends data. Monitors for 1+ year. Implanted at a hospital by an EP doctor.  

Treatment varies depending on the degree and cause of the heart block, but as a general approach: 

  • Provider may stop or reduce a medication. 

  • Heart block from an electrolyte abnormality or heart attack may resolve with correction of the underlying issue. 

  • Common medications for heart block include atropine and isoproterenol. These may be used in the hospital in the short term to treat a slow heart rate that causes symptoms, but second and third degree heart block may be unresponsive. 

  • Some 2nd and most 3rd degree heart block will need a pacemaker. Because the natural pacemakers in the heart are not communicating, an artificial pacemaker is placed.  

Brief treatment summary: 

  • 1st degree – often benign, no treatment necessary, annual monitoring with an ECG 

  • 2nd degree – stop/reduce any potential meds, monitor to measure frequency/duration and screen for any associated symptoms, screen for structural and/or plumbing issues with echo and stress test; may need a pacemaker inserted.  

  • 3rd degree – same treatment as 2nd degree, but more likely to need a pacemaker inserted.