Can atrial fibrillation (AF) cause dyspnea?

Does Atrial Fibrillation Cause Dyspnea?

Yes, atrial fibrillation directly causes dyspnea through multiple pathophysiological mechanisms, and dyspnea is one of the most common presenting symptoms of AF, reported by up to two-thirds of patients. 1, 2

Mechanisms by Which AF Causes Dyspnea

Loss of Atrial Mechanical Function

• The loss of coordinated atrial contraction eliminates the "atrial kick," which normally contributes 5-15% of cardiac output, leading to reduced ventricular filling and decreased overall cardiac performance. 3, 4
• This hemodynamic impairment is particularly pronounced in patients with conditions that depend heavily on atrial contribution to ventricular filling, including mitral stenosis, hypertrophic cardiomyopathy, restrictive cardiomyopathy, and hypertension with left ventricular hypertrophy. 3, 4

Irregular Ventricular Response

• The irregular ventricular rhythm during AF causes hemodynamic impairment even at the same mean heart rate as regular rhythm, with studies demonstrating a 9-15% reduction in cardiac output due to irregularity alone. 3
• Myocardial contractility varies constantly during AF because of force-interval relationships associated with variations in cycle length, further compromising cardiac function. 3

Rapid Ventricular Rate

• AF with rapid ventricular response (typically ≥130 bpm) significantly worsens dyspnea by reducing diastolic filling time and increasing myocardial oxygen demand. 3
• Persistently elevated ventricular rates can produce tachycardia-induced cardiomyopathy, which is potentially reversible with adequate rate control. 3, 5
• Coronary blood flow is adversely affected during AF with rapid ventricular response due to increased coronary vascular resistance and decreased diastolic filling time. 3

Heart Failure Exacerbation

• AF commonly presents with or causes exacerbation of heart failure, creating a bidirectional relationship where each condition worsens the other. 1, 5
• The coexistence of heart failure and AF creates synergistically worse outcomes, with patients having almost 3-fold higher risk for stroke and almost 2-fold higher heart failure-related mortality. 5

Clinical Presentation

Symptom Prevalence

• Dyspnea is reported as a predominant symptom in up to two-thirds of AF patients, making it nearly as common as palpitations. 2
• Other common symptoms include palpitations, chest pain, fatigue, lightheadedness, and syncope, though symptoms vary with ventricular rate, underlying functional status, and duration of AF. 1, 6
• Approximately 10-40% of AF patients are asymptomatic, meaning dyspnea when present is clinically significant. 6, 7

Symptom Variability

• AF may be symptomatic or asymptomatic even in the same patient at different times. 1
• In vagal AF (characterized by slower heart rates), patients more commonly complain of irregularity rather than dyspnea, whereas dyspnea is more prominent with faster ventricular rates. 1

Diagnostic Challenges

Distinguishing AF-Related Dyspnea from Comorbidities

• In clinical practice, it is challenging to determine whether dyspnea represents an AF-related symptom or a symptom of concomitant cardiovascular and non-cardiovascular comorbidities, since common AF comorbidities such as heart failure and chronic obstructive pulmonary disease share similar symptoms. 2
• B-type natriuretic peptide (BNP) testing can help differentiate heart failure-related dyspnea from other causes in AF patients presenting with shortness of breath. 8
• Patients with permanent AF have significantly higher rates of reduced lung function (FEV₁, FVC, TLC) compared to subjects in sinus rhythm, even after adjusting for smoking and obesity. 9

Assessment Approach

• Dyspnea in AF patients correlates with exercise capacity (VO₂ peak) rather than lung function parameters, suggesting a primarily cardiac rather than pulmonary mechanism. 9
• The relationship between dyspnea severity and exercise capacity (r=-0.6) in AF patients indicates that functional impairment is a key contributor. 9

Management Implications

Rate Control as Primary Strategy

• Primary initial management focuses on controlling ventricular rate to prevent tachycardia-induced cardiomyopathy and improve dyspnea, with target heart rates typically <80 bpm at rest and <110 bpm during moderate exercise. 4
• Rate control medications include beta-blockers, non-dihydropyridine calcium channel blockers, and digoxin. 4

Rhythm Control Considerations

• Early rhythm control with antiarrhythmic drugs or catheter ablation should be considered in patients with symptomatic AF, particularly those with persistent dyspnea despite adequate rate control. 6, 7
• Catheter ablation is first-line therapy in patients with symptomatic paroxysmal AF to improve symptoms and slow progression to persistent AF. 6
• In patients with heart failure and reduced ejection fraction, catheter ablation improves quality of life, left ventricular systolic function, and cardiovascular outcomes. 6

Tachycardia-Induced Cardiomyopathy

• Attempting strict rhythm control for at least 6-8 weeks can determine if AF is contributing to ventricular dysfunction and dyspnea, as tachycardia-mediated cardiomyopathy is potentially reversible. 5
• The CAMERA-MRI trial demonstrated left ventricular ejection fraction improvement of +18% in the ablation group versus +4% in rate control, with 58% achieving normalization. 5
• Not only rapid but also normal irregular ventricular responses can cause tachycardiomyopathy, so rate control alone may be insufficient. 5

Clinical Pitfalls to Avoid

• Do not assume dyspnea in AF patients is solely due to pulmonary disease or deconditioning without assessing cardiac function and ventricular rate control. 2, 9
• Avoid using aspirin for stroke prevention in AF patients with dyspnea, as it has poorer efficacy than anticoagulation and is not recommended. 6
• Do not overlook the possibility of tachycardia-induced cardiomyopathy in patients with new-onset or worsening heart failure in the setting of AF with rapid ventricular response. 3, 5
• Remember that patients without previous angina may develop chest discomfort and dyspnea with AF onset due to coronary flow impairment, particularly in those with underlying coronary artery disease. 3