Written by Joshua Phua, Pharmacist.
In loving memory of the late Madam Lim Guat Kooi.
What is atrial fibrillation?
Atrial fibrillation (also known as AF) is a heart condition in which there is an irregular and often abnormally fast heart rate. A normal heartbeat should be regular and between 60 to 100 beats per minute when a person is at rest.
Some people with atrial fibrillation have no symptoms and are unaware of their condition until it’s discovered during a physical examination. Others may experience signs and symptoms such as:
- Palpitations (uncomfortable sensations of a racing, irregular heartbeat)
- Reduced ability to exercise
- Shortness of breath
- Chest pain
When the heart beats normally, its 4 chambers (left and right atria and ventricles) tighten and squeeze (contract) to force blood out and around the body. They then relax so the heart can refill with blood again. This process is repeated every time the heart beats.
The cluster of nerves known as the sinus node help to generate and regulate the heartbeat. As shown in the diagram below, there is a flow of electrical impulses which start at the sinus node and travel along the heart muscle to create a normal heartbeat (seen in the leftmost electrocardiogram or ECG).
In atrial fibrillation, there are disruptions to the regular electrical impulses which control the contraction of the heart’s upper chambers (atria). These abnormal impulses cause the atria of the heart to contract at random intervals and sometimes so fast that the heart muscle cannot relax properly between contractions (seen in the rightmost ECG). This reduces the efficiency and performance of the heart because the chambers do not have sufficient time to refill with blood.
AF can be categorised according to severity:
1. Paroxysmal Atrial Fibrillation – Episodes of irregular heartbeat come and go, and usually stop within 48 hours without any treatment.
2. Persistent Atrial Fibrillation – Each episode lasts for longer than 7 days (or less when it’s treated).
3. Long-Standing Atrial Fibrillation – Where the person has had continuous atrial fibrillation for a year or longer.
4. Permanent Atrial Fibrillation – Where atrial fibrillation is present at all times.
To diagnose atrial fibrillation, a doctor may review signs and symptoms, examine the patient’s previous medical history, and conduct a physical examination. There are also a few tests that are typically used, such as:
- Electrocardiogram (ECG). An ECG uses small sensors (electrodes) attached to the patient’s chest and arms to sense and record electrical signals as they travel through the heart. This test is a primary tool for diagnosing atrial fibrillation.
- Blood tests. These help doctors rule out hormones or other substances in your blood that may contribute to atrial fibrillation.
- Stress test. Also called exercise testing, stress testing involves testing the heart while undergoing physical activity and exercise.
- Chest X-ray. X-ray images help doctors see the condition of a patient’s lungs and heart. Doctors can also use an X-ray to rule out conditions other than atrial fibrillation that may have similar signs and symptoms.
Treatment of AF may involve prescribing medicines and/or surgical procedures.
- Patients with AF will normally be prescribed medicines to control the heart rate or rhythm such as beta-blockers (e.g. atenolol, bisoprolol), amiodarone, or digoxin. Doctors will also add on medicines which thin the blood such as warfarin, apixaban or rivaroxaban. These blood-thinning agents help to prevent secondary complications like a stroke (people with atrial fibrillation are more at risk of having a stroke).
- Surgical procedures can include cardioversion in which the heart is given a controlled electric shock to “reset” the sinus node and restore normal cardiac rhythm. For more severe cases, cardiologists may consider catheter ablation. This is where the area inside the heart that’s causing the abnormal heart rhythm is destroyed using radiofrequency energy. Thereafter, the patient may then need to have an artificial pacemaker fitted to help maintain their heartbeat.
The most life-threatening complication that can arise from untreated AF is the occurence of a cerebral infarction (stroke). This is because there is a greater risk of blood clots forming when the atria of the heart are not working normally. These blood clots may get pumped into the blood supply to the lungs or the general blood circulation, and subsequently lead to blockage of arteries in the brain, causing a stroke.
Untreated AF can also lead to heart failure because the persistent, irregular contractions of the heart muscle will lead to progressive weakening of the heart’s ability to pump blood properly.
If you suspect you may have atrial fibrillation, please consult a doctor for more information and advice.