Atrial fibrillation (AF) is the most common cardiac arrhythmia and is characterized by chaotic and disorganized atrial electrical activation, with rates exceeding 350 impulses/min. This irregular atrial activity results in an unpredictable ventricular rhythm, leading to hemodynamic inefficiency and increased thromboembolic risk.
Unlike atrial flutter, where the electrical circuit is organized and repetitive, AF features continuous and fragmented depolarization of the atria, with loss of effective atrial contraction. This phenomenon is associated with a high risk of complications, including heart failure and ischemic stroke.
Atrial fibrillation is frequently associated with structural heart diseases, particularly valvular diseases, heart failure and ischemic heart disease. Arterial hypertension is one of the main risk factors, as chronic pressure overload leads to progressive remodeling of the left atrium, with dilation and fibrosis.
The pathogenetic mechanism is related to a combination of structural changes (fibrosis, inflammation) and electrophysiological alterations (reduced atrial refractory period). These factors facilitate the development of ectopic foci and multiple micro-reentries, which fragment the propagation of the electrical impulse.
From a pathophysiological perspective, loss of atrial contraction results in reduced ventricular filling, with decreased cardiac output. In addition, blood stasis in the left atrial appendage favors thrombus formation, with an increased risk of embolic events.
Chronic lung diseases, such as COPD and pulmonary hypertension, contribute to atrial fibrillation through pressure overload of the right atrium. Increased pulmonary pressure leads to atrial dilation and altered electrical propagation, predisposing to the development of multiple reentry circuits.
In these patients, AF is often persistent or permanent, with a higher risk of heart failure and severe pulmonary hypertension. Loss of atrioventricular synchrony further impairs right heart function, promoting systemic venous congestion.
In addition to structural heart disease, atrial fibrillation can be triggered by metabolic alterations and genetic dysfunctions that influence atrial electrical stability. Hyperthyroidism, for example, increases sympathetic stimulation, shortens the atrial refractory period, and facilitates the initiation of ectopic foci.
Electrolyte imbalances, particularly hypokalemia and hypomagnesemia, may also increase atrial excitability and promote fragmentation of the electrical signal. Some forms of AF may also have a genetic basis, with mutations affecting ion channels and electrical signal transmission.
Atrial fibrillation can be classified according to the duration of the arrhythmia and the underlying causes. This distinction is essential to guide therapeutic strategy and long-term management.
Atrial fibrillation (AF) is a multifactorial arrhythmia, whose development is favored by pathological conditions and both modifiable and non-modifiable risk factors. Early identification of these factors is essential to prevent the onset of arrhythmia and limit its complications.
Advanced age is the main risk factor: the prevalence of AF increases with age due to progressive atrial remodeling and degeneration of the conduction tissue. In subjects over 75 years of age, the risk of developing AF is particularly high.
Arterial hypertension is one of the most common causes of AF. Chronic pressure overload on the left ventricle leads to myocardial hypertrophy and increased stress on the atrial wall, resulting in fibrosis and conduction abnormalities.
Structural heart diseases are another fundamental predisposing factor. Valvular diseases, especially mitral stenosis, create atrial pressure overload that favors the development of arrhythmia. Ischemic heart disease and heart failure also predispose to AF, as they alter myocardial perfusion and propagation of the electrical impulse.
Metabolic factors play a crucial role in the genesis of AF. Hyperthyroidism accelerates the automaticity of the sinus node and increases the excitability of atrial tissue, predisposing to arrhythmias. Electrolyte imbalances, particularly hypokalemia and hypomagnesemia, may destabilize cardiac electrical activity and facilitate the onset of AF.
An unhealthy lifestyle contributes to disease progression. Obesity is an important risk factor, as it promotes hypertension, chronic inflammation and obstructive sleep apnea, all of which increase the probability of AF. Excessive alcohol consumption (holiday heart syndrome), caffeine, and smoking also have a pro-arrhythmic effect by stimulating the sympathetic nervous system and altering the cardiac ionic balance.
Prevention of AF is based on management of risk factors. Control of arterial hypertension reduces atrial remodeling and the risk of developing arrhythmia. Early treatment of valvular disease and heart failure can prevent the development of irreversible structural alterations. Management of sleep apnea and correction of metabolic imbalances are also fundamental strategies to prevent AF.
Atrial fibrillation may present with a wide range of symptoms, depending on ventricular rate and the presence of underlying heart disease. Some patients are asymptomatic and discover the arrhythmia only during a routine check-up, while others experience marked and debilitating symptoms.
The most common symptom is palpitation, perceived as irregular and rapid heartbeats. Unlike atrial flutter, in which palpitations are regular, in AF the patient reports a sensation of “irregular and unpredictable heartbeat”. Dyspnea is another frequent symptom, due to reduced cardiac function and decreased ventricular filling resulting from the loss of atrial contraction.
In patients with a very high ventricular response, reduced cardiac output may cause asthenia and decreased exercise tolerance. In subjects with ischemic heart disease, irregular tachycardia may precipitate angina pectoris due to increased myocardial oxygen demand. In more severe cases, AF can cause syncope or presyncope episodes, especially if there is highly irregular ventricular conduction or intermittent AV block.
On physical examination, the characteristic finding of atrial fibrillation is an irregular pulse. Unlike atrial flutter, in which tachycardia is regular, AF shows a completely irregular rhythm with no constant conduction pattern.
Cardiac auscultation reveals a chaotic and irregular heartbeat, with variable intensity of heart sounds depending on AV conduction. In patients with mitral insufficiency or mitral stenosis, the characteristic murmur may be accentuated by loss of effective atrial contraction.
In cases of AF with very high ventricular rate, signs of low cardiac output may appear, such as cold skin and sweating. In subjects with heart failure, signs of venous congestion may be observed, including peripheral edema, jugular venous distension and bilateral pulmonary rales.
In hyperthyroid patients with AF, systemic signs of hyperthyroidism may be present, such as tremor, profuse sweating and hyperactivity. Conversely, in subjects with AF secondary to heart failure, the patient may appear hypoperfused, with cold extremities and dyspnea even at rest.
In some cases, the radial pulse may be lower than the actual rate found on cardiac auscultation (pulse deficit), due to variability in the strength of ventricular contractions.
Atrial fibrillation (AF) should be suspected in the presence of an irregular pulse and suggestive symptoms such as palpitations, dyspnea and fatigue. However, diagnostic confirmation requires an electrocardiogram, while further tests are used to define the cause and clinical implications.
The first step in diagnosis is clinical suspicion, which arises from the presence of an irregular cardiac rhythm on physical examination. In patients with hypertension, ischemic heart disease or heart failure, AF should always be considered among the possible causes of symptoms such as fatigue and exercise intolerance.
A completely irregular pulse during radial palpation, associated with variable heart rate, is highly suggestive of AF and warrants immediate ECG for diagnostic confirmation.
A 12-lead ECG is the key test to diagnose atrial fibrillation. The tracing shows the following characteristics:
These elements allow certain diagnosis of AF. However, when ECG is not immediately available, pulse monitoring with portable devices or smart devices can be used to confirm rhythm irregularity.
If AF is intermittent and not documentable with standard ECG, the following can be used:
Once AF is confirmed, it is essential to identify any underlying causes and assess thromboembolic risk and cardiac function. First-level tests include:
In patients with difficult-to-manage AF or young patients with isolated AF, an electrophysiological study (EPS) may be performed to identify possible focal triggers and assess the indication for catheter ablation.
Management of atrial fibrillation (AF) is based on three fundamental goals:
In patients with AF and rapid ventricular response, the first step is to reduce heart rate to improve cardiac function. First-line drugs include:
The goal is to maintain a resting ventricular rate below 110 bpm in asymptomatic patients, while in patients with heart failure or persistent symptoms, lower values are targeted.
Restoration of sinus rhythm is indicated in patients with recent and symptomatic AF. Electrical cardioversion is the most effective method:
Pharmacological cardioversion is an alternative in stable patients:
Before cardioversion, a transesophageal echocardiogram (TEE) is necessary to rule out atrial thrombi, unless the patient has been anticoagulated for at least 3 weeks.
In patients with symptomatic recurrent AF, catheter ablation is an effective strategy. The goal is electrical isolation of the pulmonary veins, which often act as AF triggers.
Main indications for ablation:
Maintenance of sinus rhythm may require long-term antiarrhythmic therapy:
Lifestyle management is essential to prevent recurrence of AF:
Thromboembolic risk in AF is high and is assessed using the CHA₂DS₂-VASc score:
The most widely used drugs are DOACs (apixaban, rivaroxaban, edoxaban, dabigatran), preferred over warfarin for their better safety profile.
The prognosis of AF depends on the timeliness of diagnosis and management of risk factors. If treated early, the risk of complications can be reduced, but AF tends to recur over time. The main prognostic implications include:
In suitable patients, catheter ablation improves quality of life and reduces recurrences, representing the most effective strategy in patients with symptomatic paroxysmal AF.
Atrial fibrillation (AF) is associated with numerous complications that can have a significant impact on patient prognosis and quality of life. The risk of adverse events depends on arrhythmia duration, ventricular rate, and the presence of cardiac or systemic comorbidities.
The most feared complication of AF is ischemic stroke. Loss of effective atrial contraction promotes blood stasis, especially in the left atrial appendage, predisposing to thrombus formation. If an embolus migrates to the cerebral circulation, it can cause a cardioembolic stroke, which is larger and more disabling than strokes of other origin.
Thromboembolic risk is assessed using the CHA₂DS₂-VASc score and, in patients with high scores, anticoagulant therapy is necessary to reduce the risk of embolic events.
The high and irregular ventricular rate typical of AF can cause chronic overload of the left ventricle, reducing its contractile capacity. This can lead to heart failure, with signs of pulmonary and systemic congestion.
In patients with AF and uncontrolled rapid ventricular response, tachycardiomyopathy can develop, characterized by a reversible reduction in ejection fraction once rate control is achieved.
AF tends to become progressively persistent and eventually permanent, due to electrical and structural atrial remodeling. The concept that “AF begets AF” describes this phenomenon: the longer the atrium remains in fibrillation, the harder it is to restore sinus rhythm.
Numerous studies have demonstrated an increased risk of dementia in patients with AF, even in the absence of clinical stroke. The underlying mechanism is probably related to silent cerebral microemboli and reduced cerebral perfusion secondary to hemodynamic instability.
In patients with structural heart disease, AF may predispose to episodes of torsades de pointes or ventricular fibrillation, especially in the presence of proarrhythmic drugs or electrolyte abnormalities. Although rare, sudden cardiac death can occur in subjects with Wolff-Parkinson-White (WPW) syndrome and abnormal conduction.