Atrial fibrillation

See also the article about atrial fibrillation for Altrincham and Sale Advertiser:
Reduce Your Risk of Stroke (05/06/2013)

Atrial fibrillation (AF) is the most common type of arrhythmia with irregular and often fast heartbeat, affecting 500,000 people in the United Kingdom. Normally, heart beats approximately 60-100 times per minute; however, in untreated AF it may be 100-150 beats per minute. Depending upon the duration and severity, AF can be classified in several types:

  • Paroxysmal atrial fibrillation - with sudden onset of symptoms that come and go. In other words, suddenly it starts and suddenly it stops. Paroxysmal AF terminates within 7 days (usually in 48 hours) without any treatment.
  • Persistent atrial fibrillation - lasts for more than 7 days and does not revert back to normal heart rhythm (cardioversion) without treatment. It may recur after successful treatment.
  • Longstanding persistent atrial fibrillation - lasts for more than a year.
  • Permanent atrial fibrillation - as the name indicates, is irreversible, the heart does not revert back to the normal rhythm and there are no further attempts on cardioversion.

What happens in atrial fibrillation?

Normally, when heart contracts the oxygenated blood is pushed into the blood vessels to reach all the body parts. Then, the heart relaxes to get filled again with oxygenated blood and this process is repeated again and again at regular intervals. In AF, the upper two chambers of the heart (called atria) contract randomly and so fast that they do not allow the heart to be filled properly. This affects the performance of the heart which is like an engine running half-empty. Symptoms of AF include dizziness, tiredness, shortness of breath and sometimes unpleasant awareness of heart beats (palpitations). But, some patient may be asymptomatic with no subjective problems and unaware of their fast and irregular heart beat.

Why it happens

AF occurs when sudden and abnormal electrical impulses override the natural beating of the heart. Thus, natural pacemaker (sinus node) loses its control over the heart leaving it to beat irregularly. Gradually, over time the electric and mechanical properties of the heart muscle change (remodeling) perpetuating the arrhythmia.

Who is at risk?

AF can affect any adult at any age. Men are more prone to suffer from AF than women. Atrial fibrillation is more common in elderly people and affects 10% of population above 75 years of age. AF is common in people with high blood pressure and atherosclerosis. Usually it does not affect the young; however, it may occur in the young people with certain heart conditions such as valvular heart disease. AF triggered by excessive alcohol intake especially in combination with heavy physical exercise. AF is common in people with hyperactive thyroid gland (hyperthyroidism, thyrotoxicosis) and interestingly also among endurance sportsmen.

Possible complications

Stroke is the major complication of AF. Irregular heart beat in AF leads to sluggish blood flow in the upper heart chambers. The stagnation of blood predisposes to the formation of small bloods clots. If the blood clots get dislodged from heart and enter circulation, they may end up stuck in the small vessels of the brain. The stuck blood clot blocks vessel and the blood supply to the brain, causing ischemic stroke. AF through the lack of coordination of heart contraction and resulting reduced cardiac output may precipitate heart failure and angina.

Prognosis

AF is not an immediately life-threatening condition; however, it can cause unpleasant symptoms, increases risk of stroke and long-term mortality. People with atrial fibrillation need blood tests and usually echocardiogram (heart ultrasound). Medicines, such as beta blockers and calcium channel blockers are used to control rate and rhythm of the heart and warfarin and new anticoagulant drugs (dabigatran, apixaban, rivaroxban) are used to thin blood and thus decrease the risk of stroke.