Chaotic and disorganized atrial activity produces an irregular heartbeat
Aetiology
Hypertension and heart failure are the most common causes in the developed world
Other causes include MI, hyperthyroidism, rheumatic heart disease, sepsis and electrolyte disturbances
No cause found in 2-10% (idiopathic) - lone AF
Pathophysiology
The exact pathophysiology of AF is unclear, but factors that cause dilation of the atria through inflammation and fibrosis result in discrepancies in the refractory periods within the atrial tissue
This causes electrical re-entrant pathways within the atria, and recurrent uncoordinated atrial contraction
This results in an irregular atrial rhythm between 300-600 bmp
AV is unable to transmit beats as quickly as this and so does so intermittently, resulting in an irregular ventricular rhythm
Filling time is reduced which reduces CO - allows stasis of blood which increases stroke risk
Classification of AF
Acute: lasts less than 48 hours
Paroxysmal: lasts less than 7 days and is intermittent
Persistent: lasts more than 7 days but is amenable to cardioversion
Permanent: lasts longer than 7 days and is not amenable to cardioversion