Atrial flutter is a supraventricular tachyarrhythmia characterized by rapid and regular atrial activation, with a rate between 240 and 350 impulses/min. It is sustained by a macro-anatomic reentry circuit, resulting in continuous atrial stimulation and variable conduction to the ventricles. Unlike atrial fibrillation, in which atrial activation is chaotic and disorganized, flutter features more organized electrical activity, with regular and repetitive atrial waves.
Its onset is linked to structural and functional factors that disrupt the normal cardiac conduction system. The causes predisposing to the development of this arrhythmia can be divided into three main groups:
Structural heart diseases are the most frequent cause of atrial flutter, particularly mitral valve disease (mitral stenosis and insufficiency), ischemic heart disease, dilated cardiomyopathy and congestive heart failure.
The main pathogenetic mechanism in these cases is chronic atrial overload, due to increased filling pressures and dilation of the left or right atrium. Enlargement of the atrial chamber alters the normal conduction system and promotes the formation of a persistent reentry circuit.
From a pathophysiological perspective, atrial dilation and resulting myocardial fibrosis impair normal electrical impulse propagation. Impulse conduction becomes non-uniform, creating regions with different conduction times. This scenario favors the formation of a stable reentry circuit, which in typical atrial flutter is located at the cavotricuspid isthmus in the right atrium.
The main consequence of this alteration is the loss of effective atrial contraction. The atria do not contract synchronously with the ventricles, resulting in reduced cardiac output, which can precipitate heart failure in predisposed patients. Furthermore, blood stasis in the atrium increases the risk of thromboembolism, with possible thrombus formation in the left atrial appendage.
Chronic pulmonary diseases, such as chronic obstructive pulmonary disease (COPD), pulmonary hypertension and pulmonary embolism, may predispose to atrial flutter through a mechanism of pressure and volume overload of the right atrium.
The pathogenetic mechanism is related to increased pulmonary arterial pressure, which causes chronic right ventricular overload. Over time, this leads to right atrial dilation and alteration of its electrophysiological architecture, facilitating the maintenance of a stable reentry circuit.
From a pathophysiological point of view, atrial flutter associated with pulmonary diseases develops more frequently in the right atrium. The mechanism is similar to that of structural heart diseases: atrial dilation and fibrosis result in abnormal impulse conduction, favoring reentry.
Hemodynamic effects depend on the ventricular response. If AV conduction is high (e.g., with a 2:1 ratio), there is an increase in heart rate, with consequent reduction in ventricular filling time and risk of heart failure. In addition, impairment of right atrial function can aggravate systemic venous congestion, causing peripheral edema and congestive hepatomegaly.
Certain metabolic and pharmacological conditions may predispose to atrial flutter through mechanisms of altered conduction and electrical instability. Among these, the most relevant are hyperthyroidism, electrolyte imbalances (hypokalemia, hypomagnesemia), and use of pro-arrhythmic drugs.
In hyperthyroidism, excess thyroid hormones cause increased automaticity of the SA node and accelerated atrial conduction, favoring the onset of a reentry circuit. Electrolyte imbalances, on the other hand, alter the stability of cardiac cell membranes, predisposing to reentry arrhythmias.
From a pathophysiological perspective, atrial flutter in these conditions occurs in a structurally normal atrial substrate but with conduction abnormalities favoring functional reentry. Unlike forms associated with structural heart disease, myocardial tissue is not necessarily altered, and flutter may resolve with correction of the underlying condition.
Regardless of the cause, atrial flutter occurs more frequently in patients with advanced age, arterial hypertension, heart failure and previous cardiac interventions. Progressive atrial remodeling, with increased fibrosis and altered conduction, promotes arrhythmia chronification.
In many patients, atrial flutter represents an intermediate evolutionary stage towards atrial fibrillation, as both share similar pathogenetic mechanisms. Early management is therefore crucial to prevent disease progression and reduce the risk of complications.
Atrial flutter can be classified based on the morphology of the reentry circuit and the duration of the arrhythmia.
These distinctions are essential for therapeutic management, as some forms respond better to ablation than others.
Based on the location of the reentry circuit, a distinction is made between:
From a clinical point of view, atrial flutter can be divided into:
Atrial flutter develops in the presence of conditions that favor atrial remodeling or alter electrical conduction. In addition to structural and metabolic diseases already discussed, there are predisposing factors that increase the risk of onset or chronification of the arrhythmia.
Advanced age and arterial hypertension are two of the main risk factors. Aging leads to increased atrial fibrosis and reduced integrity of intercellular junctions, facilitating maintenance of the reentry circuit. Hypertension, on the other hand, results in chronic atrial overload that accelerates electrical and structural remodeling.
In patients with obesity and diabetes, the risk is increased by the combination of endothelial dysfunction, increased oxidative stress and chronic inflammation, which contribute to atrial electrical dysfunction. Obstructive sleep apnea, common in obese subjects, has also been associated with increased sympathetic nervous system activity and episodes of intermittent hypoxia, factors that promote electrical instability.
The use of stimulating substances such as alcohol, caffeine, and sympathomimetic drugs can trigger episodes of atrial flutter, especially in predisposed subjects. Alcohol, in particular, has a direct toxic effect on myocardial cells, promoting uncoupling of atrial electrical conduction.
In terms of prevention, management of atrial flutter is based on control of cardiovascular risk factors. Optimization of blood pressure, management of metabolic diseases and treatment of sleep apnea reduce the likelihood of arrhythmia onset and prevent its progression. Smoking cessation, reduced alcohol consumption and regular physical activity help maintain rhythm stability.
The clinical presentation of atrial flutter varies according to ventricular rate and the presence of underlying heart diseases. Some patients are asymptomatic and discover the arrhythmia during a routine examination, while others report symptoms related to altered cardiac function.
Palpitations are the most frequent symptom, presenting as regular and rapid heartbeats, distinct from the irregularity typical of atrial fibrillation. In patients with 2:1 AV conduction, the heart rate remains around 150 bpm, making the arrhythmia clearly perceptible. Dyspnea is common in those with reduced cardiac reserve, since inefficient atrial contraction reduces ventricular filling and cardiac output.
In cases with a particularly high ventricular response or in patients with pre-existing myocardial dysfunction, symptoms of heart failure may occur, such as peripheral edema, orthopnea, and elevated jugular venous pressure. In some patients, reduced myocardial oxygen delivery causes chest pain, especially in the presence of coronary artery disease.
Syncope or presyncope is less common but can occur if AV conduction suddenly becomes very slow or very rapid, reducing cerebral perfusion. This is more frequent in patients with sinus node disease or pre-existing conduction blocks.
On clinical examination, the findings depend on the ventricular response and any hemodynamic compromise. The pulse is usually rapid and regular, typically around 150 bpm in cases of 2:1 conduction. In forms with variable conduction, the rhythm may appear slightly irregular.
Cardiac auscultation shows a tachycardic rhythm, often lacking the normal filling pause due to the loss of effective atrial contraction. In patients with associated mitral stenosis, the diastolic murmur may be more evident due to increased flow across the valve.
In advanced cases, there may be signs of systemic venous congestion, such as jugular vein distention, hepatomegaly, and peripheral edema. If left heart failure is predominant, pulmonary rales and exertional dyspnea may appear.
In patients with reduced cardiac reserve, atrial flutter can induce a picture of hypotension, with reduced peripheral perfusion and prolonged capillary refill time. In these cases, rapid ventricular rate compromises diastolic filling, reducing stroke volume and arterial pressure.
Atrial flutter is suspected based on a suggestive history (regular and rapid palpitations, dyspnea, fatigue) and a compatible physical examination (regular tachycardia with rapid pulse). However, the definitive diagnosis relies on the electrocardiogram (ECG) and may require further investigations to define the type, underlying cause, and thromboembolic risk.
The first diagnostic step is clinical suspicion. In patients with rapid and regular palpitations, especially if the rate is around 150 bpm, atrial flutter should be considered among the main hypotheses. Even in cases of unexplained dyspnea or worsening heart failure, the presence of an arrhythmia should be investigated. In patients with mitral valve disease or heart failure, sudden hemodynamic instability may suggest the onset of flutter with a high ventricular response.
Once arrhythmia is suspected, a 12-lead ECG is the first test to confirm atrial flutter.
The tracing shows specific features:
If the ECG is inconclusive, a drug that temporarily blocks AV conduction (such as adenosine, beta-blockers, or calcium channel blockers) can be administered to unmask the F waves.
If the arrhythmia cannot be documented with a standard ECG, the following tests are used:
Once the diagnosis is confirmed, it is essential to identify the underlying cause and assess the risk of complications.
Transthoracic echocardiography (TTE) is the first-line test to identify predisposing structural heart diseases. It allows assessment of:
In patients who are candidates for cardioversion or ablation, transesophageal echocardiography (TEE) is necessary to exclude thrombi in the left atrial appendage.
If flutter occurs in a patient without evident heart disease, metabolic causes are investigated through blood tests:
In patients with atypical or difficult-to-manage flutter, an electrophysiological study (EPS) may be indicated to map the reentry circuits and guide the therapeutic strategy, especially before catheter ablation.
The management of atrial flutter has three main objectives:
In patients with atrial flutter and high ventricular rate, the first step is to reduce the ventricular response. The drugs of choice are:
These drugs do not convert flutter to sinus rhythm, but prevent sustained ventricular tachycardias, improving symptoms.
Atrial flutter, unlike atrial fibrillation, has a very high success rate with synchronized electrical cardioversion.
Indications for cardioversion are:
A synchronized low-energy shock (50–100 J) is used, with a success rate over 95%.
In patients who cannot undergo electrical cardioversion, pharmacological cardioversion can be attempted with:
Before cardioversion, transesophageal echocardiography (TEE) is required to rule out atrial thrombi, unless the patient has been anticoagulated for at least 3 weeks.
Radiofrequency ablation of the cavotricuspid isthmus is the treatment of choice for typical atrial flutter.
Advantages of ablation:
In patients with atypical flutter or complex circuits, ablation may be more difficult and require detailed electrophysiological mapping.
After a first occurrence of atrial flutter, prevention of recurrences is based on:
In patients with persistent or recurrent atrial flutter, the following can be used:
Atrial flutter, like atrial fibrillation, is associated with an increased risk of ischemic stroke. The need for anticoagulation 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.
Atrial flutter has a better prognosis than atrial fibrillation if treated early with ablation. However, if not managed properly, it can cause:
Prognosis depends on the promptness of treatment and the presence of underlying heart diseases. Ablation represents the definitive solution in most cases, with a high success rate and low risk of recurrence.
Atrial flutter, if untreated or not adequately controlled, can cause a series of complications, some of which may have serious consequences for the patient's health. The main complications include:
Many patients with atrial flutter develop, over time, episodes of atrial fibrillation. This is due to progressive electrical and structural remodeling of the atrium, which makes electrical signal conduction increasingly unstable. Atrial fibrillation is more difficult to control therapeutically and carries a higher thromboembolic risk than flutter.
Elevated ventricular rate, if persistent, can lead to progressive heart failure with left ventricular dysfunction. This phenomenon is known as tachycardiomyopathy, that is, cardiomyopathy induced by chronic tachycardia. In patients with underlying heart disease, the risk of heart failure is even greater, especially if flutter is not quickly controlled.
Like atrial fibrillation, atrial flutter also entails a significant risk of thromboembolism. Blood stasis in the left atrial appendage promotes thrombus formation, which can embolize and cause ischemic events, including cerebral stroke. Thromboembolic risk is particularly high in patients with associated risk factors (advanced age, hypertension, heart failure, prior stroke or TIA).
In patients with already compromised cardiac function, atrial flutter can cause hypotension and reduced systemic perfusion, with possible multiorgan impairment. This condition occurs more frequently in patients with advanced heart disease, severe mitral valve disease, or significant ventricular dysfunction.
One of the main challenges in managing atrial flutter is recurrence after cardioversion. Although electrical cardioversion is highly effective in restoring sinus rhythm, flutter tends to recur in the absence of definitive treatment such as catheter ablation. For this reason, in patients with recurrent flutter, ablation of the cavotricuspid isthmus is considered the definitive therapy of choice.