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The end of Warfarin?
The WATCHMAN has arrived. This new, implantable cardiac device aims to reduce the risk of stroke in patients with Atrial Fibrillation (AF), providing them an alternative to the long-term use of blood thinners. The device, offered by a top US hospital, is implanted in the left atrial appendage to prevent any blood clots (that form there) from entering the bloodstream. A potential game changer? In a clinical trial, 9 out of 10 people were able to stop taking Warfarin just 45 days after the WATCHMAN procedure.
What is AF?
AF is an abnormal cardiac rhythm characterised by an irregularly irregular heartbeat secondary to disorganised atrial electrical activity and contraction. It is the most common sustained arrhythmia, occurring in 1-2% of the general population. Serious complications of AF include stroke, congestive cardiac failure/cardiomyopathy, ischaemic limbs and mesenteric ischaemia.
Anticoagulation has been the cornerstone of AF management for many years. AF causes disorganised atrial contraction and blood stasis, increasing the risk of an embolic stroke secondary to thrombus formation in the left atrium. Therefore, anticoagulation guidelines are based on considerations between risk of stroke vs risk of bleeding. Common risk stratification scores, including CHADS2 and CHA2DS2VASc, are used to determine if anticoagulation is required. Current oral anticoagulants include Warfarin (which is the most commonly used), dabigatran, rivaroxaban and apixaban. Absolute contraindications to anticoagulation include intracranial haemorrhage, intracranial mass and end stage liver disease.
Treatment of AF
The other pillars of AF management are rate, and rhythm control, as well as treating the underlying disorder (e.g. hyperthyroidism or hypertension). The AFFIRM trial put to rest the myth that rhythm control was superior to rate control in the treatment of AF. Rate control with anticoagulation is now the mainstay of treatment, with rhythm control reserved for those symptomatic with AF. The most common rate controlling agents include β-blockers (metoprolol, atenolol), calcium channel blockers (diltiazem, verapamil) or cardiac glycosides such as digoxin.
Considering that AF affects approximately 10% of Australians over 75, it is a disease that will become more and more common in hospital settings. We all need a thorough understanding of its treatment options. Due to the prevalence and complications of AF, new innovations such as the WATCHMAN may become widely used, and keeping abreast of these latest innovations is smart practice for all medical students and doctors.
Can you feel the beat tonight?
You are on night shift at a tertiary hospital emergency department when you get urgently called to examine Elton, a 52-year-old male who has arrived via ambulance from the airport. He appears pale and diaphoretic, and continues to complain of light-headedness. Does he need a resus bay? As the nurses set up, you note that he has an irregularly irregular pulse, a HR of 160 and a BP of 80/50. His ECG trace shows that he is in rapid AF, and it’s time for you and your team to get to work!
History and Examination
Patients with AF will often become symptomatic if their HR increases to over 100 (rapid AF). These patients commonly complain of light-headedness, chest tightness, palpitations, lethargy and/or shortness of breath. In addition, they may have symptoms of underlying conditions (e.g. a productive cough if pneumonia is present), and thus a comprehensive examination is required to assess for any underlying causes (e.g. raised JVP and bi-basal crepitations suggesting cardiac failure). If the patient has a low BP, management differs significantly and may involve cardioversion.
The all-important ECG
The most common ECG findings of AF are: absence of P waves, an irregularly irregular rhythm and a variable ventricular rate. A full list of ECG changes in AF can be found here. Other differentials on ECG are atrial flutter with a variable block, multifocal atrial tachycardia, supraventricular tachycardia (SVT), AV nodal re-entry tachycardia (AVNRT) as well as Wolff-Parkinson-White (WPW) syndrome.
Causes of AF
The causes of AF can be placed into two distinct categories. The first category is atrial fibrillation secondary to a pre-existing cardiac condition or damage to the heart. Examples include myocardial infarct, valvular disease, congenital heart defects, congestive cardiac failure and hypertension. The second category encompasses causes found mostly in the younger population and includes hyperthyroidism, pneumonia, and exposure to stimuli (e.g. alcohol, caffeine and drugs). AF can also occur without any pre-existing conditions and this is called lone AF.
It is essential you make an early diagnosis of AF by closely analysing the ECG as well as looking for any underlying causes. Thanks to your prompt intervention, Elton was stabilised with initial treatment and the “Ablate and Pace” technique was used in the next few days. He was even kind enough to come visit you prior to discharge, leaving a personalised autograph: Can you feel the beat tonight? Signed, EJ.