What are the causes of atrial fibrillation (afib) in an adult patient with a possible history of cardiovascular disease, hypertension, heart valve disorders, coronary artery disease, or thyroid disease?

Causes of Atrial Fibrillation

Atrial fibrillation is predominantly caused by underlying cardiovascular disease in 70-80% of cases, with hypertension, coronary artery disease, heart failure, and valvular heart disease being the most common culprits, while only 20-30% of cases occur without identifiable structural heart disease ("lone AF"). 1, 2

Cardiovascular Causes (Most Common)

Structural Heart Disease

• Hypertension is a leading cause, particularly when left ventricular hypertrophy is present, creating substrate through atrial pressure elevation and diastolic dysfunction 1
• Coronary artery disease promotes AF through atrial ischemia, structural remodeling, and increased left atrial pressure; when AF develops during acute MI, it signals particularly poor prognosis 1, 3
• Heart failure with systolic or diastolic dysfunction causes atrial pressure elevation and is strongly associated with AF development 1, 2
• Valvular heart disease, especially mitral valve disease (stenosis or regurgitation), is common regardless of severity but correlates with left atrial enlargement 1, 2

Cardiomyopathies

• Hypertrophic cardiomyopathy and dilated cardiomyopathy both create arrhythmogenic substrate 1
• Restrictive cardiomyopathies including amyloidosis, hemochromatosis, and endomyocardial fibrosis 1, 2

Congenital Heart Disease

• Atrial septal defect is the most common congenital cause in adults 1

Acute/Reversible Causes

Metabolic and Systemic

• Hyperthyroidism and other metabolic disorders can trigger AF that resolves with treatment 1
• Alcohol intake ("holiday heart syndrome") is a well-recognized acute precipitant 1

Acute Cardiac Events

• Acute myocardial infarction, pericarditis, and myocarditis can trigger AF 1
• Postoperative AF commonly occurs after cardiac or thoracic surgery 1
• Pulmonary embolism and other acute pulmonary diseases 1

Medical Conditions and Risk Factors

Modifiable Risk Factors

• Obesity is an important risk factor, promoting AF through progressive left atrial dilation that correlates with increasing body mass index 1, 4
• Diabetes increases risk, particularly in women 2, 5
• Sleep apnea syndrome is commonly associated with AF, though the exact mechanism (hypoxia, autonomic changes, or systemic hypertension) remains unclear 1

Other Cardiac Conditions

• Mitral valve prolapse with or without regurgitation 1, 2
• Mitral annular calcification 1, 2
• Cardiac tumors and constrictive pericarditis 1
• Cor pulmonale and idiopathic right atrial dilation 1, 2

Lone/Idiopathic Atrial Fibrillation

• 30-45% of paroxysmal AF and 20-25% of persistent AF occur in younger patients without demonstrable underlying disease 1
• Familial AF is more common than previously recognized, with increased likelihood among offspring of parents with AF, suggesting genetic susceptibility 1
• The term "idiopathic AF" requires exclusion of hyperthyroidism, chronic lung disease, sinus node dysfunction, and Wolff-Parkinson-White syndrome 2, 5

Autonomic and Electrophysiological Mechanisms

• Autonomic imbalance plays an important role in AF initiation, with some patients showing vagal predominance (typically nocturnal or postprandial) and others sympathetic predominance (daytime) 1
• Associated arrhythmias including atrial flutter, WPW syndrome, and AV nodal reentrant tachycardia can predispose to AF; treating the primary arrhythmia reduces AF recurrence 1

Critical Clinical Pitfalls

Never dismiss new-onset AF as coincidental in patients with known cardiovascular disease—it represents active disease interaction requiring aggressive management of both conditions. 3 The ACC/AHA/ESC guidelines emphasize searching for predisposing conditions in every patient presenting with AF, as successful treatment of underlying causes (particularly acute/reversible ones) often eliminates the arrhythmia 1. Age-related cardiac structural changes (increased myocardial stiffness, atrial fibrosis) may be associated with AF even in "apparently healthy" elderly patients 1.