Atrial Fibrillation: Causes, Pathophysiology and Treatment

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Atrial fibrillation (AF) is a cardiac arrhythmia. It is the most common arrhythmia and it has implications for patients and anaesthetists alike. The anaesthetist must take into consideration the physiological and pharmacological implications of this common arrhythmia.
In a healthy individual receiving a general anaesthetic, the anaesthetist must be aware of the causes and treatment of acute onset AF, both intra-operatively and peri-operatively. Patients with AF often develop a decline in left ventricular performance and other hemodynamic instabilities including reduced diastolic filling and tachycardia mediated cardiomyopathy1, all of which can reduce cardiac output and pose difficulties for the anaesthetist.
One of the
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Atrial remodeling, both structural and electrical, can facilitate reentrant circuits for electrical current, which can then lead to permanent fibrillations. The main mechanism proposed for electrical remodeling leading to permanent AF is shortening of the refractory period7.

Postoperative atrial fibrillation (POAF) is a common problem seen by anaesthetists and patients who develop POAF have a worse outcome8. Developing POAF puts patients at risk of hemodynamic derangements, postoperative stroke, perioperative myocardial infarction, ventricular arrhythmias, and heart failure8.

In cardiothoracic surgical patients, an incidence of as high as 16-46% has been reported8. This is related to a number of factors that can be encountered during surgery. Mechanical factors like manipulating the heart, pain and sympathetic stimulation can all induce POAF. It can also be related to systemic inflammatory processes, hypotension, hypoxia, anemia and metabolic alterations. These situations can all be expected during anaesthesia. Volatile agents used during anaesthesia may also have antifibrillatory action8.

Another interesting cause of AF is a familial cause. Olson et al (2006) investigated a hereditary predisposition to AF involved a nonsense mutation in the KCNA5 gene. This gene encodes kv1.5. kv1.5 is an atrial specific potassium channel. The group reported a novel genetic basis for idiopathic AF seen in patients lacking traditional risk
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