November 5th, 2020
Atrial fibrillation (AF) is an arrhythmia characterized by irregular and rapid atrial contractions. This leads to excessive signalling of the ventricles and therefore, a rapid heart rate. AF remains one of the major causes of stroke, heart failure, and cardiovascular morbidity in the world.
Patterns of atrial fibrillation
AF can be paroxysmal i.e. occur as arrhythmia episodes that terminate spontaneously or are resolved within 7 days of onset. If an AF episode does not terminate spontaneously and lasts >7 days it is referred to as persistent AF; and if it lasts continuously for over one year it is classified as long-standing persistent AF. AF is permanent only if a decision has been made jointly by the physician and patient to stop any attempts at restoring sinus rhythm.
Patients with AF may present with palpitations or increased awareness of rapid, irregular or uncomfortable heartbeat.
Shortness of breath
AF can cause shortness of breath with or without exercise. This is due to left atrioventricular asynchrony or ventricular dysfunction.
Chest pain can often be a symptom of an AF episode. It may be nonspecific or it may resemble angina pectoris.
When AF causes circulatory insufficiency in a person, they will present with dizziness, syncope or presyncope.
Reduced functional capacity
Over half of people living with AF have reduced functional capacity due to non-specific symptoms such as fatigue and lethargy, or have some degree of disability as a result of their intolerance to physical activities.
About one-third of people with AF remain completely asymptomatic.
AF episodes may be triggered by various precipitating factors such as alcohol and caffeine intake, exercise, infection, surgery, thyrotoxicosis, electrolyte imbalance, and underlying cardiovascular conditions which affect the atrium.
The more risk factors that an individual has, the more likely they are to develop AF and the more likely it is to be persistent. AF risk factors include increasing age, hypertension, heart failure, coronary artery disease, valvular heart disease, obesity, diabetes mellitus, chronic kidney disease (CKD), alcohol consumption, obstructive sleep apnea (OSA), congenital heart defects, hyperthyroidism, channelopathies (abnormal QT and Brugada syndromes) and genetic predisposition to abnormal atrial excitation.
Most AF patients are at risk of developing thromboembolism due to stasis, endothelial dysfunction, and hypercoagulability at the level of the atrium. This can lead to a systemic embolic event with symptoms of stroke, transient ischemic accident (TIA), mesenteric ischemia or peripheral ischemia.