Causes of Atrial Fibrillation in Older Adults
In elderly patients, atrial fibrillation results primarily from age-related structural cardiac changes combined with cardiovascular comorbidities, most commonly hypertension with left ventricular hypertrophy, coronary artery disease, heart failure, and valvular disease—particularly mitral valve pathology. 1
Age-Related Structural Changes as the Foundation
The aging heart undergoes progressive atrial fibrosis, replacing approximately 0.5-1.0% of cardiomyocytes per year with fibrous tissue, which disrupts electrical coupling and creates heterogeneous conduction patterns that sustain AF 1. This process occurs even in elderly patients without demonstrable heart disease, as increased myocardial stiffness and left atrial dilation develop as consequences of aging-related structural remodeling 2, 1. These changes create the substrate for sustained AF, explaining why the arrhythmia prevalence exceeds 10% in patients aged 85 years or older 3.
Cardiovascular Diseases: The Primary Triggers
Hypertension and Left Ventricular Hypertrophy
Hypertension, particularly when left ventricular hypertrophy is present, represents one of the most common causes of AF in elderly patients 1. The combination creates increased left atrial pressure and structural remodeling that promotes arrhythmia development 4.
Coronary Artery Disease
Coronary artery disease promotes AF through atrial ischemia, structural remodeling, and increased left atrial pressure 1. In elderly patients with coronary disease, AF occurs predominantly in those with left ventricular dysfunction 4.
Heart Failure
Heart failure both promotes AF and is worsened by AF, with the 3-year incidence of AF approaching 10% in patients treated for heart failure 1. The bidirectional relationship makes heart failure a critical consideration in elderly AF patients 2.
Valvular Heart Disease
Mitral valve disease represents the most common valvular etiology of AF, with occurrence more common in patients with enlarged left atrium and congestive heart failure 1. Approximately 70% of AF patients have associated chronic organic heart disease 4.
Cardiomyopathies and Structural Heart Disease
Cardiomyopathies—including hypertrophic cardiomyopathy, dilated cardiomyopathy, and restrictive cardiomyopathies (amyloidosis, hemochromatosis)—predispose to AF 2, 1. Congenital heart disease, especially atrial septal defect in adults, carries high AF incidence 2, 1.
Reversible and Acute Causes Requiring Immediate Evaluation
Hyperthyroidism and other metabolic disorders must be ruled out in every instance of newly discovered AF 1. Acute conditions that can trigger AF include 2, 1:
- Acute myocardial infarction (portends particularly poor prognosis) 5
- Alcohol intake ("holiday heart syndrome") 2
- Pulmonary embolism 2
- Pericarditis and myocarditis 2
- Postoperative state after cardiac or thoracic surgery 2
- Acute infections, particularly pneumonia 6
Medical Comorbidities
Obesity is an important risk factor for AF, with excess risk mediated by left atrial dilation that increases progressively as body mass index rises 2. Sleep apnea syndrome is commonly encountered in AF patients, though the mechanism remains undetermined 2, 1. Chronic kidney disease contributes to AF through maladaptive mechanisms 1.
Drug-Induced Atrial Fibrillation
Drug-induced AF from cardiovascular, non-cardiovascular, and particularly anticancer drugs represents an increasingly recognized cause, especially in elderly patients on polypharmacy 1.
Lone Atrial Fibrillation: Less Common in the Elderly
Approximately 20-25% of persistent AF cases occur without demonstrable underlying disease, though this percentage is lower in elderly compared to younger patients 2, 1. A critical pitfall is that a causal underlying disease may appear over time in patients initially classified as having lone AF, making the distinction less clear in elderly populations 2, 1.
Critical Clinical Pitfall
The longer time period during which risk factors operate in elderly patients allows cumulative structural changes that ultimately manifest as AF, partially explaining the strong age-AF association 1. Women over age 75 with AF face particularly high stroke risk, making recognition and anticoagulation decisions especially critical 1.