Atrial fibrillation

Atrial fibrillation (AF or AFib) is a cardiac arrhythmia (an abnormality of heart rate or rhythm) originating in the atria. Abnormal electrical impulses in the atria cause the ventricles to contract erratically. AF is the most common cardiac arrhythmia. If rapid, it may compromise blood flow and cause fainting, orthostatic hypotension (low blood pressure on standing up) or low blood pressure. In addition, it predisposes to thrombosis and embolism to the brain, being a prime risk factor for stroke.

Diagnosis

Electrocardiogram

Atrial fibrillation is diagnosed on an electrocardiogram, an investigation performed routinely whenever irregular heart beat is suspected. Characteristic findings are (a "rhythm strip" of lead II is shown):

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• absence of P waves
• unorganized electrical activity in their place
• irregularity of R-R interval due to irregular conduction of impulses to the ventricles

Other investigations

While many cases of AF have no definite cause, it may be the result of various other problems (see below). Hence, renal function and electrolytes are routinely determined, as well as thyroid-stimulating hormone (commonly suppressed in hyperthyroidism and of relevance if amiodarone will be administered) and a blood count. A chest X-ray is generally performed. In acute-onset AF associated with chest pain, cardiac troponins or other markers of damage to the heart muscle may be ordered. Coagulation studies (INR/aPTT) are usually performed, as anticoagulant medication may be commenced.

Related Topics:
Renal function - Electrolyte - Thyroid-stimulating hormone - Hyperthyroidism - Amiodarone - Blood count - Chest X-ray - Chest pain - Cardiac troponins - Coagulation - Anticoagulant

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