Description

• Sudden transient loss of consciousness due to decreased cardiac output causing cerebral hypoxia in patients with bradyarrhythmias secondary to advanced heart block and sick sinus syndrome
• It was first described in 1846.
• System(s) affected: cardiovascular, nervous
• Synonym(s): drop attacks; Morgagni, Morgagni-Adams-Stokes; Spens syndrome

Epidemiology

Incidence
Incidence rate of 5–10% for those age >70 years

Prevalence

• Unknown (Overall prevalence of 3rd-degree atrioventricular [AV] block is 0.02%.)
• Predominant sex: male = female

Pediatric Considerations
Rare during pregnancy

Etiology and Pathophysiology

• Medications
  • Digoxin (common)
  • Calcium channel blockers
  • β-Blockers (e.g., sotalol)
  • Clonidine
  • Propafenone (Rythmol), a class IC antiarrhythmic
  • Isoproterenol
• Other causes:
  • Coronary artery disease
  • Congenital heart diseases
  • Valvular diseases involving mitral and aortic valve
  • Infiltrative and connective tissue diseases involving the heart and its conduction system (e.g., systemic sclerosis, amyloidosis, sarcoidosis)
  • Degeneration of the AV node secondary to aging (Lenegre syndrome)
  • Electrolyte disturbances like hyperkalemia
  • Infectious diseases: local infections like acute rheumatic fever, endocarditis, myocarditis, Lyme disease, and systemic infections like infectious mononucleosis
  • Neuromuscular diseases (e.g., myotonic muscular dystrophy or Kearns-Sayre syndrome)
  • Postoperative cardiac damage
• Asystole and torsade de pointes are the two mechanisms underlying Stokes-Adams attacks in patients with bradyarrhythmias.
• The abrupt onset of complete heart block or cessation of tachyarrhythmia in patients with sick sinus syndrome lead to either prolonged asystole or torsade de pointes by prolonging the QT interval.

This in turn reduces the cardiac output reducing blood supply to brain and leading to the attack.

Genetics

• May be associated with congenital complete atrioventricular block (CCAVB)
• Of children with CCAVB, 40% experience syncopal episodes.

Risk Factors

• Use of the medications listed under “Etiology and Pathophysiology”
• Coronary artery disease
• Endocarditis and myocarditis
• Mitral/aortic valve disease
• History of previous AV nodal dysfunction/cardiac surgery
• Bundle-branch and/or fascicular block
• Acute myocardial infarction (MI) (especially acute right coronary artery occlusion)
• Amyloidosis
• Chagas disease
• Lyme disease
• Connective tissue diseases involving the heart (e.g., systemic lupus erythematosus, rheumatoid arthritis, sarcoidosis)
• Hyperkalemia
• Acidosis
• Rheumatic fever
• Chest wall trauma

General Prevention

• Avoid negative chronotropic drugs (e.g., β-blockers, calcium channel blockers, digoxin, clonidine) in at-risk patients.
• Prevention of cardiovascular disease through diet/exercise

Commonly Associated Conditions

• Myocardial ischemia/acute MI
• High-degree AV conduction abnormality
• Atrial standstill
• Right bundle branch block (RBBB)
• CCAVB
• Systemic manifestations of connective tissue disease
• Sick sinus syndrome
• Neuromuscular disease
• Sudden cardiac death
• Heart failure