Atrial flutter

Atrial flutter is a common type of tachycardia (rapid heart beat) that has many similarlites to atrial fibrillation, but also a few important differences that are relavent when planning treatment options. Although there are different varieties of flutter, the most frequent sort is typical flutter, also known as common flutter. Typical flutter results from a short-circuiting of the electrical heart beat so that the eletrical impuse starts circling rapidly around the tricuspid valve in the right atrium. This circle of electricity rotates at approximately 300 times a minutes and the atriums try to squeeze with each rotation, which makes them appear as if they are "fluttering". This has similar consequences to atrial fibrillation in that the atriums do not have time to fill and empty and the flow of blood through the atriums slows down considerably. This slow flow means there is less blood available to fill the ventricles and therefore less to be pumped around the body. The slow flow may also result in blood clot formation in the left atrium, in particular in the left atrial appendage.

Although the atriums beat at 300 bpm, the ventricles are usually proteted by the filtering effect of the AV node.If the rapid but regular atrial rate of 300 bpm is filtered in a 2 to 1 ratio (i.e. alternate beats are allowed through to the ventricles) then the ventricular rate and the pulse rate will be a steady and regular 150 bpm, which is a classic finding in typical flutter. If there is a greater degree of filtering, either through the use of rate-fontrolling drugs or a older, more sluggish AV node, there may be a 4 to 1 ratio and a heart rate of 75 bpm. It is even possible for the filtering effect to vary almost on a beat by beat basis between 2 to 1 and 4 to one resulting in an irregular pulse. Finally, in younger people, particularly when adrenaline levels are high (e.g. with exercise), there may be no filtering and the ventricles briefly pump at 300 bpm. This extremely fast rate often causes people to collapse. Heart rates greater than 100 bpm may lead to symptoms of palpitations, breathlessness (particularly on exertion), chest tightness and dizzy spells.

Typical flutter may occur in people with otherwise healthy and normal hearts but it is often associated with high blood pressure, previous heart surgery and respiratory disease. It may come and go intermittently, stopping on its own after minutes, hours or even days (paroxysmal flutter) or carry on indefinitely once it has started, unless a treatment if performed (persistent or permanent flutter). It may cause no symptoms or limitations and be discovered by chance (asymptomatic) or cause a variety of symptoms dictated by the impact of losing normal atrial contraction and/or having a rapid ventricular rate (symptomatic). A small number of individuals who have very few or no symptoms may develop tachycardia cardiomyopathy as a result of their ventricles pumping at 150 bpm hour after hour, day after day, causing the ventricular muscle to stretch and weaken until heart failure develops. Fortunately this is reversible if a normal rate or rhythm can be restored.

Typical atrial flutter is closely linked to atrial fibrillation. Some people have the ability to have both arrhythmias and switch from one to the other. Some have fibrillation which converts to flutter when prescribed antiarrhythmic drugs. Others start with flutter, have this successfully treated but subsequently go on to develop fibrillation at a later stage. Certainly, having one increases the chances of developing the other.

People with atrial flutter should see a Heart Rhythm Specialist for a thorough assessment to look for underlying heart disease and associated conditions and also to discuss the different treatment options.

Symptoms may be addressed in a number of ways. In common with atrial fibrillation, there are two strategies - rate control or rhythm control. In a rate control strategy the atriums are allowed to continue to flutter and beat at 300 bpm and drugs such as betablockers, calcium channel blockers and digoxin try to increase the filtering through the AV node and thus slow the ventricular rate and the pulse. If the ratio of conducted impulses from atrium to ventricle can be increased from 2 to 1 to 4 to 1 the pulse rate will drop from 150 bpm to 75 bpm which may abolish symptoms arising a rapid ventriclar rate such as palpitations, exertional breathlessness and dizziness. Any symptoms that result from the inability of the rapidly beating atriums to fill and empty efficiently, such as fatigue and general tiredness, will remain. It can be very challenging to filter the ventricular rate down to 75 bpm and often large doses of drugs, usually in combination, are required.

In a rhythm control strategy the aim is to stop the flutter from occuring. If drugs are going to be tried it usually requires more potent medication such as sotalol or amiodarone. Drugs may reduce the frequency and duration of attacks, making the problem more bearable, but it is unusual for them to completely abolish atrial flutter. If someone is in persistent flutter a cardioversion is often required to restore normal rhythm, although this may only be a temporary respite.

Radiofrequency catheter ablation for atrial flutter is a relatively simple and safe invasive procedure that can abolish atrial flutter permanently with a very high success rate and low risk of complications. It is a treatment option that should be considered in any patient with atrial flutter even if there has only been one episode. Find out more about catheter ablation of atrial flutter by clicking here.

Atrial flutter increases the risk of having a stroke through the same means as atrial fibrillation. The very rapid fluttering of the atriums may result in blood clot formation in the left atrial appendage and if some or all of the clot is pumped out of the heart it may end up in the brain (causing a TIA or stroke) or damage another organ. The risk of blood clot formation is influenced by a persons health and age and can be calculated using the CHADS2 scoring system. It is recommended that higher risk patients should be protected by taking oral anticoagulants such as warfarin.

For a detailed description of the mechanism of thromboembolic stroke, risk assessment and treatment options in atrial flutter and fibrillation, click here.

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