Atrial Fibrillation: A Cardiology Overview

• During atrial fibrillation, the quivering atria can lead to blood pooling in the upper chambers of the heart  
• The symptoms of atrial fibrillation can be subtle and it is important to be aware of these symptoms in order to receive prompt treatment.  
• Treatment options for atrial fibrillation need to be analyzed and reviewed as the best treatment for each individual varies.   

In the United States, those over the age of sixty-five are at risk of developing atrial fibrillation because of cardiovascular aging and it is the most frequent significant arrhythmia.   

Atrial fibrillation or AFib is a serious heart condition that disrupts the electrical signals in the heart, causing an irregular heartbeat and higher association of devastating strokes.  If left untreated, AFib can lead to heart failure, blood clots in the heart, chest pain, and can lead to sudden cardiac death.   

High blood pressure, valvular heart disease, diabetes, obesity, and sleep apnea can increase a patient’s risk of AFib.  Lifestyle contributors include alcohol, caffeine, dehydration, poor sleep patterns, and stress.   

In addition, stress can cause changes in the electrical repolarization of cells, evoked potentials, and increase in T-wave amplitude, promoting cardiac arrhythmogenesis.

Mechanism of Atrial Fibrillation

During atrial fibrillation, the quivering atria can lead to blood pooling in the upper chambers of the heart (LAA – left atrial appendage).  This can lead to blood clots, which can break free and block arteries.  Severe cases may require surgery.   

Depending on the severity of the condition, treatment may include medications to control the heart rate, blood thinners to prevent blood clots, and surgery to remove the damaged part of the heart.   

The most common complication of atrial fibrillation is heart failure.  Classifications of AFib include paroxysmal, persistent, long-standing, and permanent. 

The Cardiac Electrical Pathways

Within the heart, the cardiac electrical pathway is a network of cells that helps the heart to contract in a coordinated manner.  The heart consists up of specialized cardiac myocytes, which send electrical signals throughout the myocardium.   

Regulation of the rate of the electrical  impulse depends on the needs of the body.  Abnormalities in the heart’s conduction can result in arrhythmias, such as atrial fibrillation. 

The cardiac electrical pathway comprises three principal components:  

1. the atrioventricular (AV) node 
2. the sinoatrial (SA) node 
3. the interatrial pathway bundle  

These three components work together to conduct electrical stimulus from the AV node to the atria and vice versa.   

The SA node is an area of special cells in the right upper chamber of the heart, near the superior vena cava.  These cells are the primary pacemaker of the heart and create an electrical signal 60 to 100 times a minute.  These impulses make sure synchronous action potentials in the atrial chambers.  Within a matrix of fibrous tissue, a thin fat pad covers the cells in the SA node.   

The AV node is a smaller version of the SA node.  It is in the middle of the heart (the secondary pacemaker), and it slows the conduction velocity of an action potential.  The AV node is the point of communication between the atria and the ventricles.  It receives blood from the sinoatrial nodal branch of the coronary artery and conducts an electrical signal to the atrioventricular node.

Symptoms of Atrial Fibrillation

The symptoms of atrial fibrillation are often subtle and can include a fast heart rate, chest discomfort, cough, extreme fatigue, shortness of breath, and dizziness.   

Symptoms can be present on their own or can occur due to comorbidities.  The most common symptom of atrial fibrillation is an irregular pulse rate, causing discomfort in the arms and neck. 

Treatment Options for Atrial Fibrillation

Treatment includes lifestyle changes, electricity, medications, and/or surgery.  The ideal treatment depends on the patient’s age, symptoms, and underlying health issues.  Antiarrhythmic medications can control the patient’s heart rate but are effective in only a smaller percentage of patients.  New treatment tools offer a left atrial appendage (LAA) for patients with nonvalvular AFib who cannot tolerate blood thinners.  

Medications to treat AFib include beta blockers, calcium channel blockers, digoxin, and the antiarrhythmic medications:  propafenone (Rhythmol), flecainide (Tambocor), sotalol (Betapace), dofetilide (Tikosyn), amiodarone (Cordarone), and dronedarone (Multaq).  

Surgical ablation is a treatment option. Surgeons create a small circular scar at the source of the abnormal electrical signal. This scar prevents the abnormal signal from spreading to the rest of the heart. The procedure can occur through an open-heart surgery or as a minimally invasive procedure. 

Electrical cardioversion may stop AFib and restore normal sinus rhythm for patients in persistent atrial fibrillation.  The effectiveness of cardioversion to convert to a sinus rhythm is effective, though success is lower when the atrial fibrillation is longstanding or when the patient presents with left atrial enlargement.  Cardioversion is less effective in those patients of the age of eighty. 

The Bottom Line

Atrial fibrillation is commonly seen in many patients and once identified, it is imperative to seek treatment as soon as possible in order to achieve the best possible outcomes.   

Longstanding atrial fibrillation can result in very serious complications and must be addressed in a timely manner before worsening events occur.  

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