What Is Atrial Fibrillation And Atrial Flutter (Heart Fluttering)
What Is Atrial Fibrillation?
Atrial fibrillation and atrial flutter are abnormally rapid contractions of the atria resulting from a series of abnormal electrical impulses stimulating it; and on some impulses reach the ventricles, making them contract abnormally fast as well, reducing their efficiency to pump blood.
- Atrial fibrillation and atrial flutter have their origin in disorders that cause the enlargement of atria.
- Depending on the rate of contraction of the ventricles, the symptoms can range from fatigue and chest pain (angina) to palpitations.
- Diagnosis by physical examination can be confirmed by electrocardiography (ECG).
- Drugs that slow down the contractions of ventricles are used to treat this condition. Application of electric shock (cardioversion) can normalize the heart rhythm.
- Incidence of Atrial fibrillation as well as atrial flutter is more frequent in older people.
Atrial fibrillation or flutter is characterized by an abnormally fast contraction of atria, so fast that the walls of the atria seem to be quivering instead of contracting. This affects the proper functioning of the ventricles and impairs the pumping of blood. In atrial fibrillation, the atrial rhythm is not only fast but irregular also. This, in turn, leads to irregular ventricular rhythm. In atrial flutter, the atrial rhythm is still fast but it is regular but the ventricular rhythm may be either regular or irregular. Since the atrioventricular node conducts electrical impulses at a slower rate, all the impulses do not reach the ventricles. Consequently, the ventricles beat at a lower rate than the atria. Even then, the ventricular contractions are still too fast to allow proper filling of the ventricles with blood, impairing the heart’s capacity to pump adequate quantity of blood. This may result in low blood pressure and heart failure.
Causes OF Atrial Fibrillation
Certain diseases that affect the heart, such as coronary heart disease and high blood pressure, can be the cause of the abnormal enlargement of the atria, which in turn predisposes the heart to atrial fibrillation and flutter. Valve defects, precipitated by rheumatic heart disease resulting from an attack of rheumatic fever, congenital defects in the structure and function of the heart, increased heart rate resulting from high levels of thyroid hormones due to hyperthyroidism etc., are other factors favorable to the development of atrial fibrillation and flutter. Excessive alcohol consumption also can be a contributing factor. But sometimes no underlying heart disorder can be identified.
Complications: Since the rapid and incomplete atrial contractions fail to empty all the blood into the ventricles with each beat, blood gets stagnated in the heart, leading to the formation of blood clots. These clots may break free (emboli) and move out of the heart, especially when the arrhythmia is reversed either automatically or through treatment, often leading to blockage in smaller blood vessels. Life threatening situations can result from this, including stroke, if the blockage occurs in an artery in the brain. That is the reason why stroke is found to be the initial symptom of atrial fibrillation and flutter in some cases.
Symptoms and Diagnosis Of A. Fib
Symptoms are usually dependant on the ventricular rate of contraction. A ventricular rate of up to 120 beats/ min. may not precipitate any noticeable symptoms, though rates higher than that may result in discomfort in the chest and severe palpitations.
Both artrial fibrillation and flutter are fast arrhythmias. But the main difference between these two types of arrhythmias is that; in atrial fibrillation, in addition to being fast, the pulse is also irregular, but in atrial flutter, the pulse is fast but regular.
Fatigue, shortness of breath and fainting bouts are symptoms precipitated by the impaired capacity of the heart to pump adequate amount of blood. Older people may experience pain in the chest or develop heart failure. Extremely low blood pressure due to atrial fibrillation or flutter, when combined with other heart disorders, can occasionally result in shock.
Atrial fibrillation or flutter can be diagnosed from symptoms and physical examination but an electrocardiography (ECG) can confirm the condition.
Treatment Of Atrial Fibrillation
Treatment focuses on reducing the rate of contraction of ventricles as well as bringing down abnormally fast heart rhythms to normal level. The disorders of the heart, which are responsible for the development of atrial fibrillation and flutter, are also treated with appropriate drugs. Hyperthyroidism should be treated when present. Surgical intervention to correct valve defects and congenital heart defects also helps. An integral part of the treatment is anticoagulants and blood thinners such as aspirin, in view of the additional risk of blood clot formation in the heart and the potential for stroke.
Slowing the Heart Rate:
- The first line of treatment is with drugs that slow down ventricular contraction, enabling the heart to pump more efficiently.
- In the treatment of atrial fibrillation or flutter, calcium channel blockers like diltiazem are usually tried first.
- Verapamil is a useful drug that can slow down the transfer of electrical impulses from the atria to the ventricles.
- Beta-blockers like atenolol and propranolol may also prove to be useful.
- Digoxin, one of the oldest drugs for heart failure, is the drug of choice for people who have heart failure too, along with the arrhythmia.
Restoring the Rhythm:
Occasionally, atrial fibrillation or flutter may resolve on its own. But more often, medical intervention is necessary to restore normal heart rhythm. Amiodarone and sotalol are two commonly used antiarrhythmic drugs. Other drugs such as flecainide and propafenone are effective as well. But more effective than any antiarrhythmic drug is the active approach: that of converting the arrhythmia to normal rhythm, by the application of shock directly to the heart (cardiversion).
Arrhythmia should be converted to a normal rhythm as early as possible because, once the atria have become enlarged, as it usually happens in about six months from the onset of the disease, it is very difficult to restore normal rhythm. Even when normal rhythm is restored, recurrence rate becomes very high, in spite of taking antiarrhythmic drugs. Also, with the enlargement of the atria, the heart disorder that causes it too becomes worse.
Destroying the Atrioventricular Node
Destruction of the atrioventricular node, which transmits the abnormally patterned electrical impulse to the ventricles, can stop any abnormal impulse from the atria reaching them, thus preventing the ventricles from contracting. A minimally invasive procedure called radiofrequency ablation, in which electrodes fitted at the tip of catheters are guided into the heart for selective destruction of tissue, is employed to destroy the atrioventricular node. Once this node is destroyed, electric impulses from the atria cannot pass into the ventricles. But the drawback is that, it necessitates the use of an artificial pacemaker to stimulate the ventricles. An alternative is pulmonary vein isolation, in which the atrial tissue around the pulmonary vein is destroyed instead, preserving the atrioventricular node. Since this procedure is riskier, with a lower success rate of only 60 to 80 percent, it is rarely used, except in young patients who are free of any other form of heart disorder.
Ablation with radiofrequency can successfully disrupt the abnormal electrical circuit that is causing the atrial flutter, restoring normal rhythm. This minimally invasive procedure has a very high success rate.
Preventing Blood Clots: The risk of blood clots blocking an artery supplying the brain and causing stroke actually increases significantly on reversing atrial fibrillation or flutter and restoring normal rhythm. The reason is that, when the normal rhythm is restored, the pumping action of the heart improves and the existing blood clots inside the heart break free and start travelling through the blood stream. Because of this, almost all people with atrial fibrillation or flutter are given anticoagulants to prevent clots even after the arrhythmia is brought under control, especially those with additional risk factors such as diabetes, old age and high blood pressure. Some structural disorders such as enlargement of the left atrial chamber and disorders of mitral valve pose extra risk. Unless it is an emergency, doctors usually start patients on anticoagulants three weeks prior to a scheduled cardioversion to correct atrial fibrillation or flutter.
However, doctors have to take into consideration the benefits as well as the potential risks involved in anticoagulant use because anticoagulants are contraindicated in patients with bleeding disorders. People with inadequately treated high blood pressure also should avoid these drugs, since they may result in bleeding complications, excessive blood loss during and after surgery or even hemorrhagic stroke.
Once started, anticoagulants are not discontinued even when proper control of the heart rhythm is achieved. This is because the arrhythmia may come back any time, without the person being aware of it, bringing with it the dangers associated with clot formation.
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Yasser Elnahas
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