Acquired causes

• Ischemic heart disease: Damage from a heart attack can scar the conduction tissue.
• Degenerative disease of the conduction system (Lenègre disease) – common with aging.
• Cardiomyopathies (e.g., hypertrophic, dilated).
• Inflammatory/infectious processes:
  • Rheumatic fever
  • Lyme disease (Borrelia burgdorferi)
  • Viral myocarditis (e.g., Coxsackievirus)
• Medications that slow AV conduction:
  • Beta‑blockers
  • Calcium‑channel blockers (verapamil, diltiazem)
  • Digoxin
  • Anti‑arrhythmic drugs (e.g., amiodarone, sotalol)
• Electrolyte disturbances – hyperkalaemia, severe hypomagnesemia.
• Thoracic surgery, especially procedures involving the aortic valve or septal defect repair.
• Congenital heart defects that affect the conduction pathways.

Risk factors

• Age > 65 years.
• History of myocardial infarction or coronary artery disease.
• Structural heart disease (valve disease, cardiomyopathy).
• Chronic use of AV‑node‑blocking drugs.
• Autoimmune disorders (e.g., systemic lupus erythematosus) that can cause myocarditis.
• Family history of congenital heart block.

Diagnosis

Diagnosing AV block relies on a combination of clinical assessment and electro‑diagnostic testing.

Electrocardiogram (ECG)

• First‑line test; records the PR interval, pattern of dropped beats, and ventricular escape rhythm.
• Serial ECGs may be needed because some blocks are intermittent.

Holter monitor (24‑48 hour ambulatory ECG)

• Captures intermittent or exercise‑related blocks that a resting ECG might miss.

Event recorder or implantable loop recorder

• Used when symptoms are infrequent; records rhythm when the patient activates the device.

Exercise stress testing

• Evaluates how conduction changes with increased heart rate; useful for differentiating physiologic versus pathologic block.

Echocardiography

• Assesses structural heart disease (valve lesions, ventricular function) that may underlie the block.

Blood tests

• Electrolytes, thyroid function, cardiac enzymes, and inflammatory markers (CRP, ESR) to rule out reversible causes.

Cardiac MRI or CT (optional)

• Provides detailed imaging of the conduction system in cases of suspected infiltrative disease (e.g., sarcoidosis).

Treatment Options

Treatment is tailored to the type of AV block, symptom severity, and underlying cause.

First‑degree AV block

• Often no treatment needed if asymptomatic.
• Review and possibly discontinue medications that slow AV conduction.
• Correct electrolyte abnormalities.
• Regular follow‑up (e.g., yearly ECG) to monitor progression.

Second‑degree AV block

• Mobitz I (Wenckebach):
  • Observation if asymptomatic.
  • Remove or reduce AV‑node‑blocking drugs.
  • Consider pacemaker if symptoms are present or if block progresses.
• Mobitz II:
  • High risk of progressing to complete block; guidelines recommend permanent pacemaker implantation even if asymptomatic (ACC/AHA 2021 Guideline).

Third‑degree (complete) AV block

• Immediate hospitalization.
• Temporary transvenous pacing if hemodynamically unstable.
• Permanent pacemaker (dual‑chamber preferred) is the definitive therapy.

Medication Management

• Discontinue or adjust dosages of beta‑blockers, calcium‑channel blockers, digoxin, and anti‑arrhythmics if they are the likely cause.
• Treat underlying infection (e.g., doxycycline for Lyme disease) or inflammation.
• Electrolyte correction (IV calcium for hyperkalaemia, magnesium supplementation, etc.).

Lifestyle & Supportive Measures

• Avoid excessive alcohol, which can depress conduction.
• Maintain adequate hydration.
• Monitor heart rate regularly if instructed by a clinician.

Living with Heart Block (AV Block)

Adaptations help maintain quality of life and reduce the risk of sudden events.

• Regular follow‑up: Keep scheduled appointments for ECGs, pacemaker checks, or device interrogations.
• Activity guidance: Most patients can exercise, but avoid extreme exertion that provokes symptoms. Use a heart‑rate monitor if advised.
• Medication awareness: Carry a list of all drugs and dosages; inform any new prescriber about your AV block.
• Medical alert identification: Wear a bracelet or carry a card stating “AV block – may have pacemaker” for emergency personnel.
• Pacing device care:
  • Check the device’s battery status at least annually.
  • Avoid strong magnetic fields (e.g., MRI – only if the device is MRI‑compatible).
• Symptoms diary: Log episodes of dizziness, palpitations, or syncope; share with your cardiologist.

Prevention

While some causes (age‑related degeneration, congenital abnormalities) are unavoidable, many risk factors are modifiable.

• Control cardiovascular risk factors: Manage hypertension, diabetes, and hyperlipidemia.
• Healthy lifestyle: Regular aerobic exercise, a balanced diet rich in fruits, vegetables, and omega‑3 fatty acids, and smoking cessation.
• Medication review: Periodically assess with your physician whether AV‑node‑blocking drugs are still necessary.
• Prompt treatment of infections: Early antibiotics for Lyme disease or other bacterial infections can prevent cardiac involvement.
• Electrolyte balance: Stay hydrated and monitor potassium/magnesium if you have kidney disease or are on diuretics.

Complications

If left untreated, especially higher‑grade blocks, can lead to serious outcomes:

• Syncope and falls – increasing injury risk, especially in older adults.
• Heart failure – chronic low heart rate diminishes cardiac output.
• Sudden cardiac death – rare, but possible when ventricular escape rhythm is unstable.
• Thromboembolic events – slower ventricular rates can predispose to atrial stasis and clot formation in patients with concurrent atrial fibrillation.
• Pacemaker‑related complications – infection, lead dislodgement, or device malfunction (still far safer than untreated complete block).

When to Seek Emergency Care

For non‑emergent symptoms (mild fatigue, occasional palpitations), contact your primary care provider or cardiologist within 24–48 hours for evaluation.

Sources: Mayo Clinic. “Heart block.” 2022; American Heart Association. “AHA/ACC/HRS Guideline for the Management of Patients With Bradycardia and Cardiac Conduction Delay.” 2021; CDC. “Lyme Disease.” 2023; National Institutes of Health. “Cardiac Conduction System.” 2022; Cleveland Clinic. “AV Block.” 2023; World Health Organization. “Cardiovascular diseases.” 2022.