What causes atrial fibrillation (a fib) or atrial flutter?

Causes of Atrial Fibrillation and Atrial Flutter

Atrial fibrillation and atrial flutter are primarily caused by structural heart disease, with approximately 70% of cases associated with conditions like valvular heart disease, coronary artery disease, hypertension, and cardiomyopathies, while the remaining cases occur without detectable heart disease (lone AF). 1, 2

Structural Heart Disease Causes

Cardiovascular Conditions

• Valvular heart disease: Particularly mitral valve disease 1, 2
• Coronary artery disease: Causes ischemia and scarring 2
• Hypertension: Especially when left ventricular hypertrophy is present 1, 2
• Cardiomyopathies:
  • Hypertrophic cardiomyopathy 1
  • Dilated cardiomyopathy 1
  • Restrictive cardiomyopathies (amyloidosis, hemochromatosis, endomyocardial fibrosis) 1
• Congenital heart disease: Especially atrial septal defect in adults 1
• Other cardiac conditions:
  • Mitral valve prolapse (with or without regurgitation) 1
  • Calcification of the mitral annulus 1
  • Cardiac tumors 1
  • Constrictive pericarditis 1
  • Idiopathic dilation of the right atrium 1

Acute Temporary Causes

• Alcohol intake ("holiday heart syndrome") 1
• Surgery: Particularly cardiac and thoracic surgery 1
• Electrocution 1
• Myocardial infarction: Associated with worse prognosis compared to pre-infarct AF 1
• Pericarditis 1
• Myocarditis 1
• Pulmonary conditions:
  • Pulmonary embolism 1
  • Sleep apnea syndrome 1
  • Chronic obstructive lung disease 2

Metabolic and Other Medical Conditions

• Hyperthyroidism 1
• Other metabolic disorders 1
• Obesity: Associated with left atrial dilation 1, 2
• Diabetes mellitus: Contributes to atrial fibrosis 2
• Chronic kidney disease: Alters electrolyte balance 2

Neurogenic Factors

• Autonomic nervous system imbalance: 1, 2
  • Vagal AF: More common in men, occurs at night/rest/after eating/alcohol, preceded by bradycardia
  • Adrenergic AF: Occurs during daytime, provoked by exercise/stress, associated with polyuria

Drug-Induced Atrial Fibrillation

• Cardiovascular drugs 1
• Non-cardiovascular drugs 1
• Anticancer drugs: Particularly concerning in cancer patients with multiple risk factors 1

Lone Atrial Fibrillation

• Approximately 30-45% of paroxysmal AF and 20-25% of persistent AF cases occur without demonstrable underlying disease 1
• May be isolated or familial 1
• More common in younger patients 1
• Underlying disease may appear over time 1

Pathophysiological Mechanisms

• Atrial dilatation: Creates more space for reentrant circuits 2
• Abnormal calcium handling: Disrupts normal electrical activity 2
• Atrial fibrosis: Makes atria more sensitive to profibrotic signaling 2
• Electrical remodeling: Progressive shortening of atrial effective refractory periods ("AF begets AF") 2
• Ion channel dysfunction: Alters impulse formation and propagation 2
• Aging: Associated with increased atrial fibrosis and stiffness 2

Risk Factors for Progression

• Increasing age: Prevalence increases significantly with age 2
• Atrial enlargement: Significant predictor of AF development 3
• Congestive heart failure 3
• High-endurance exercise: Lifelong high-intensity exercise increases risk 4

Clinical Implications

• The presence of AF increases the risk of stroke 5-fold and doubles all-cause mortality 2
• AF can lead to tachycardiomyopathy, a reversible cause of heart failure 2
• Treatment should target both the arrhythmia and underlying causes when possible 1
• Successful treatment of underlying conditions may eliminate AF in some cases 1

Understanding the diverse causes of atrial fibrillation and flutter is essential for effective management, as treating underlying conditions may eliminate or reduce the arrhythmia burden in many patients.