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What is second-degree heart block?

Second-degree atrioventricular (AV) block, or second-degree heart block, is a condition of the cardiac conduction system in which the conduction of atrial impulse through the AV node and/or His bundle is delayed or blocked. Patients with second-degree AV block may be asymptomatic or they may experience variety of symptoms such as lightheadedness and syncope. Mobitz type II AV block may progress to complete heart block, with a related increased risk of mortality.

How common is second-degree heart block?

This condition is actually uncommon and can affect both men and women. Please discuss with your doctor for further information.


What are the symptoms of second-degree heart block?

The common symptoms of this condition are:

  • No symptoms (more common in patients with type I, such as well-trained athletes and persons without structural heart disease)
  • Light-headedness, dizziness, or syncope (more common in type II)
  • Chest pain, if the heart block is related to myocarditis or ischemia
  • A regularly irregular heartbeat
  • Bradycardia may be present
  • Symptomatic patients may have signs of hypoperfusion, including hypotension

There may be some symptoms not listed above. If you have any concerns about a symptom, please consult your doctor.

When should I see my doctor?

If you have any signs or symptoms listed above or have any questions, please consulting with your doctor. Everyone’s body acts differently. It is always best to discuss with your doctor what is best for your situation.


What causes second-degree heart block?

Cardioactive drugs are an important cause of AV block. They may exert negative (ie, dromotropic) effects on the AVN directly, indirectly via the autonomic nervous system, or both. Digoxin, beta-blockers, calcium channel blockers, and certain antiarrhythmic drugs have been implicated in second-degree AV block.

Of the antiarrhythmic medications that may cause second-degree AV block, sodium channel blockers, such as procainamide, cause more distal block in the His-Purkinje system.

Various inflammatory, infiltrative, metabolic, endocrine, and collagen vascular disorders have been associated with AVN block, as follows:

  • Inflammatory diseases such as Endocarditis, myocarditis, Lyme disease, acute rheumatic fever
  • Infiltrative diseases such as Amyloidosis, hemochromatosis, sarcoidosis (AV conduction abnormalities can be the first sign of sarcoidosis.

Risk factors

What increases my risk for second-degree heart block?

There are many risk factors for this condition, such as:

  • Cardiac tumors
  • Trauma (including catheter-related, especially in the setting of preexisting left bundle-branch block)
  • Following transcatheter valve replacement
  • Myocardial bridging
  • Ethanol septal reduction (also called transcoronary ablation of septal hypertrophy for the treatment of obstructive hypertrophic cardiomyopathy)
  • Transcatheter closure of atrial and ventricular septal defects
  • Corrective congenital heart surgery, especially those near the septum
  • Progressive (age-related) idiopathic fibrosis of the cardiac skeleton

Diagnosis & treatment

The information provided is not a substitute for any medical advice. ALWAYS consult with your doctor for more information.

How is second-degree heart block diagnosed?

If your doctor suspects that you may experience this condition, a physical examination will be performed and some tests will be also recommended by your doctor. ECG is employed to identify the presence and type of second-degree AV block.

Diagnostic electrophysiologic testing can help determine the level of the block and the potential need for a permanent pacemaker. Such testing is indicated for patients in whom His-Purkinje (infranodal) block is suspected but has not been confirmed.

Other laboratory studies to identify possible underlying causes are as follows:

  • Serum electrolytes, calcium, and magnesium levels
  • A digoxin level in patients on digoxin
  • Cardiac biomarker testing in patients with suspected myocardial ischemia
  • Myocarditis-related laboratory studies (eg, Lyme titers, HIV serologies, enterovirus polymerase chain reaction [PCR], adenovirus PCR, Chagas titers), if clinically relevant
  • Infection-related studies, apropos a valve ring abscess
  • Thyroid function studies if appropriate

How is second-degree heart block treated?

If you are an adult with second-degree heart block that causes you to have a very slow heart rate, it is likely your doctor will recommend that you have a pacemaker fitted. In case you have second-degree heart block that was caused by a heart attack, you may need only a temporary pacemaker. If a normal heart rhythm hasn’t returned a few weeks after your heart attack, you might need to have a permanent pacemaker fitted. If you are a young person with congenital heart disease with second-degree or third-degree heart block but you don’t have a slow heart rate or any symptoms, you may not need a pacemaker.

Actually second-degree atrioventricular (AV) block in the asymptomatic patient does not require any specific therapy in the prehospital setting. If the patient is symptomatic, standard advanced cardiac life support (ACLS) guidelines for bradycardia, including the use of atropine and transcutaneous pacing, are indicated.

No specific therapy is required in the emergency department (ED) for Mobitz I (Wenckebach) second-degree AV block, unless the patient is symptomatic. Patients with suspected myocardial ischemia should be treated with an appropriate anti-ischemic regimen and worked up. Second-degree block at the level of the atrioventriocular node (AVN) may be due to digoxin, beta-blockers, or calcium channel blockers. Decreasing the dose and/or discontinuing these medications may restore normal AV conduction.

Mobitz II block is more likely to progress to complete heart block and thus requires a different approach. As with Mobitz I block, AV nodal agents should be avoided, and an anti-ischemic regimen should be instituted if ischemia is suspected.

Lifestyle changes & home remedies

What are some lifestyle changes or home remedies that can help me manage second-degree heart block?

The following lifestyles and home remedies might help you cope with this condition:

  • Patients who are discharged from the emergency department with a Mobitz II atrioventricular (AV) block should have prompt follow-up arranged with a cardiologist.
  • If high-grade AV block and, possibly, symptoms due to AV block are present, consider monitoring the patient and then performing Holter monitoring or treadmill testing in the future. If the AV block occurs at night, consider sleep apnea as the cause.

If you have any questions, please consult with your doctor to better understand the best solution for you.

Hello Health Group does not provide medical advice, diagnosis or treatment.


Review Date: September 5, 2017 | Last Modified: September 5, 2017

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