Monday, December 28, 2015

Atrial fibrillation

I was reading Atrial fibrillation today and thought I'd write a small quick review blog on it.

A patient with atrial fibrillation will usually present with palpitations or fatigue.

On physical examination, irregularly irregular pulse is characteristic.

ECG is diagnostic.

Extra tip: Your patient may have his rhythm well controlled when you see him in the wards and you might not have the characteristic physical finding of an irregular pulse or have an ECG in hand. In that case and especially during vivas, do mention that you would like to rule out other causes of fatigue by ordering CBC, SE & LFT.
CBC: Complete blood count
SE: Serum electrolytes
LFT: Liver function tests

In an acute setting, you must provide symptom relief through rate control. Beta blockers, calcium channel blockers are preferred. Digoxin is considered if blood pressure is low.

Fun fact: Why isn't Digoxin an awesome drug for rate control in exercise and anxiety?
Because the increased rate in exercise and anxiety is primarily due to adrenergic stimulation and Digoxin works through Vagal stimulation.

You need to rule out reversible causes of atrial fibrillation like electrolyte imbalance, thyrotoxicosis, fever, alcohol and drugs. Always order TSH levels.
Extra tip: Also ask for a history of snoring since sleep apnea is a treatable cause of atrial fibrillation.

Rate control is usually done first since it mitigates symptoms. Rhythm control is preceded by measures to reduce stroke, which includes either 3 weeks of anticoagulation by dabigatran / warfarin or clot exclusion by TEE.

CHADS2 score is used to decide whether anticoagulation is required. It is based on risk stratification.

Dabigatran is preferred over warfarin because INR monitoring isn't required. However, it is expensive, contraindicated in renal failure and there is no reversal in major bleeding.

Electric cardioversion or chemical cardioversion may be done depending on patient symptoms.

Drugs used for chemical cardioversion are: Flecainide, Ibutelide, Procainamide, Amiodarone.

Curative catheter ablation may be tried in patients who have recurrent atrial fibrillation and in whom antiarrhythmic drug trial has failed.

Cool fact: Propafenone is "pill in pocket" drug used by patients when they feel onset of palpitations. It is used in conjunction with beta blockers to prevent fast dysrhythmias.

Here are a few mnemonics I got online:

Precipitants / causes of Atrial fibrillation: PIRATES
PE, Ischemia, Respiratory diseases like COPD, Atrial enlargement or myxoma, Thyroid, Ethanol, Sepsis or Sleep Apnea

Mnemonic for determining major risk of bleeding: HAS BLED
HTN, abnormal LFT / RFT, Stroke, Bleeding history, Liable INR, Elderly, Drugs that predispose to bleeding.
If score >3, higher risk of major bleeding.

That's all!


Related post: Antiarrhythmic drug classes mnemonic


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