Atrial fibrillation (AFib) is a common heart rhythm disorder where the upper chambers of the heart beat rapidly and irregularly. This chaotic electrical activity causes the heart to pump inefficiently, leading to poor blood flow. While AFib is characterized by symptoms like palpitations, fatigue, or shortness of breath, a persistent cough is not typically a direct manifestation of the arrhythmia. However, a cough can be a significant symptom in a patient with AFib, pointing to one of two distinct underlying causes: fluid buildup or medication side effects.
Impaired Circulation and Pulmonary Congestion
The primary mechanism linking AFib to a cough involves the heart’s inability to effectively move blood forward, often leading to heart failure. When the atria quiver, the ventricles beat quickly and irregularly, compromising pumping efficiency. This inefficiency causes blood to back up into the pulmonary veins, creating elevated pressure in the lungs. This pressure forces fluid to leak into the air sacs and surrounding tissue, a condition known as pulmonary congestion or edema. The presence of this fluid triggers a protective reflex, commonly called a “cardiac cough,” to clear the airways.
This congestion-related cough is typically wet or productive, as the body attempts to expel the accumulated fluid. It may be accompanied by wheezing or labored breathing. The cough often becomes noticeably worse when the person lies flat, as gravity allows more fluid to settle in the lungs.
Medication-Induced Cough as a Separate Factor
A second common cause of cough in people with AFib is a side effect of necessary cardiovascular medications, entirely unrelated to heart function. Angiotensin-Converting Enzyme (ACE) inhibitors are frequently prescribed to manage high blood pressure or heart failure, conditions often coinciding with AFib. These medications work by relaxing blood vessels to improve blood flow and reduce the heart’s workload.
The mechanism involves the medication preventing the breakdown of bradykinin in the respiratory tract. The accumulation of this peptide irritates nerve endings in the airways, stimulating a cough reflex. This cough is characteristically dry, persistent, and often described as a tickle in the throat.
This recognized side effect can occur in up to 35% of patients taking an ACE inhibitor, sometimes developing weeks or months after starting the drug. This medication-induced cough is a localized reaction to the drug itself, not a sign that the heart condition is worsening. If the side effect is bothersome, a healthcare provider may switch the patient to an alternative, such as an Angiotensin Receptor Blocker (ARB), which carries a much lower risk of causing a cough.
Differentiating Symptoms and Urgent Warning Signs
Differentiating between a congestion-related cough and a medication-related cough is crucial for proper treatment. A cough caused by pulmonary congestion tends to be wet, potentially producing white, pink, or blood-tinged phlegm. This cough may intensify when lying down at night (orthopnea) or worsen with physical exertion. Conversely, an ACE inhibitor cough is usually dry, non-productive, and constant, lacking positional changes. If the cough began shortly after starting a new medication, it strongly suggests a drug side effect.
Urgent Warning Signs
A cough accompanied by certain symptoms must be treated as a medical emergency, regardless of its suspected cause. Urgent warning signs indicate a rapidly worsening heart condition, such as acute pulmonary edema, and require immediate medical attention. These signs include severe shortness of breath that comes on suddenly, especially when accompanied by a bubbling or gurgling sensation in the chest. Coughing up pink, frothy sputum is a particularly severe red flag, signaling a significant amount of fluid and blood flooding the lungs. Other serious symptoms warranting an immediate call to a doctor include chest pain, lightheadedness, or sudden, significant weight gain over a few days, which suggests rapid fluid retention.