What is atrial fibrillation?
Atrial fibrillation is an abnormal heart rhythm during which the upper
or filling chambers of the heart beat irregularly. Normally the pacemaker
of the heart generates an electrical impulse, which is conducted or carried
to the lower or pumping chambers of the heart via the electrical conducting
tissues (wires) of the heart. This allows a natural sequence of contraction
where the upper chambers (atria) beat first, thus filling the lower chambers
(ventricles). This sequence allows priming of the pumping chambers and
contributes as much as 20% of the output of the heart. In atrial fibrillation,
the hearts natural pacemaker, the sinus node, no longer generates
an electrical impulse. Instead electrical activity occurs irregularly
throughout both left and right atria. This irregular electrical impulse
is conducted erratically to the ventricles, resulting in an irregular
heartbeat which may be excessively fast and vary in volume from beat to
Causes of Atrial Fibrillation
The commonest cause of atrial fibrillation is longstanding high blood
pressure. Other common causes include valvular heart disease, weakened
heart muscle due to coronary artery disease or cardiomyopathy (viral or
unknown cause), degenerative disease of the electrical tissues of the
heart, alcohol, hyperthyroidism or in many cases-idiopathic (no cause
Symptoms of Atrial Fibrillation
When in atrial fibrillation the patient may feel his/her heart beating
rapidly and irregularly (palpitation). Atrial fibrillation may cause chest
pain, shortness of breath, dizziness, weakness or fatigue. In some patients
there are no accompanying symptoms.
Is atrial fibrillation dangerous?
If atrial fibrillation causes chest pain, shortness of breath, dizziness
or congestive heart failure (water in the lungs), the arrhythmia may be
dangerous and need to be corrected promptly. Usually however symptoms
are not that severe and the arrhythmia may be dealt with less acutely.
The major long-term danger of atrial fibrillation is an increased risk
of stroke. The atria of the heart do not contract properly during atrial
fibrillation. Blood flow is sluggish within the atria and this may lead
to clot formation. If one of these clots breaks loose, it may travel to
other parts of the body (embolism) resulting in stroke (cerebral embolism)
or blockage of blood vessels throughout the body. Blockage of vessels
to the limbs may cause inadequate blood supply (ischaemia) and endanger
the limb. Similarly, blockage of a blood vessel in the abdomen may cause
abdominal pain and bowel ischaemia, a condition that is life threatening.
What is the treatment for atrial fibrillation?
In general the treatment of atrial fibrillation consists of:
- Medications to control the heart rate,
- Medications to restore normal sinus rhythm and
- Medications to thin the blood and prevent embolization. The need for
chronic blood thinners can be predicted based on certain risk factors,
which are detailed on the opposite side of this information sheet. Change
to which are detailed in the Atrial Fibrillation