Atrial fibrillation
Overview
Atrial fibrillation (AF) is a common cardiac arrhythmia, characterized by rapid and irregular beating of the atria. It is a type of supraventricular tachycardia. This condition often leads to a higher risk of stroke, heart failure, cognitive decline, and mortality.
Pathophysiology
The pathophysiology of AF involves multiple mechanisms that promote the arrhythmia's initiation and maintenance. These include triggers, such as premature atrial contractions (PACs), and substrates that sustain the arrhythmia, such as atrial remodeling.
Triggers
The most common triggers for AF are PACs. These are often originated in the pulmonary veins but can also come from the superior vena cava, crista terminalis, and coronary sinus. PACs can initiate AF by creating a wavefront of activation that encounters a vulnerable substrate.
Substrates
Substrates that sustain AF are typically characterized by structural and electrical remodeling of the atria. Structural remodeling involves changes in atrial size, shape, and fibrosis. Electrical remodeling involves changes in atrial refractoriness and conduction.
Clinical Presentation
Patients with AF may present with a variety of symptoms, including palpitations, fatigue, dyspnea, chest pain, and syncope. Some patients may be asymptomatic and their AF may be discovered incidentally during a routine physical examination or electrocardiogram (ECG).
Diagnosis
The diagnosis of AF is typically made based on the clinical presentation and confirmed by an ECG. The ECG in AF shows irregularly irregular rhythm with absence of P waves and variable ventricular response.
Management
The management of AF involves three main strategies: rate control, rhythm control, and stroke prevention.
Rate Control
Rate control is the first-line treatment for most patients with AF. This strategy involves the use of medications, such as beta-blockers and calcium channel blockers, to control the ventricular rate.
Rhythm Control
Rhythm control may be considered in patients who are symptomatic despite rate control or who prefer this strategy. This can be achieved with antiarrhythmic drugs or procedures such as electrical cardioversion or catheter ablation.
Stroke Prevention
Stroke prevention is a critical component of AF management. This is typically achieved with anticoagulation therapy, based on the patient's risk of stroke.
Prognosis
The prognosis of AF depends on the underlying cause of the arrhythmia, the presence of comorbidities, and the effectiveness of the management strategies. In general, AF is associated with a higher risk of stroke, heart failure, cognitive decline, and mortality.
Epidemiology
AF is the most common cardiac arrhythmia, affecting approximately 1-2% of the general population. The prevalence of AF increases with age, with a significant increase in individuals over the age of 65.