Making my heart race

Atrial fibrillation, more commonly just referred to as AF, is a condition that affects the contraction of the cardiac muscle. Patients present with palpitations, resulting in a frightening feeling for most. AF is where the electrical conduction of the atrial doesn’t cause a coordinated contraction of these collecting chambers, it causes more of a fizzling of the atria. This itself doesn’t cause that much of an issue as blood entering the ventricles to be pumped around the body doesn’t rely on contraction of the atria to move the blood, it’s more of an added benefit to make sure the entire blood content is pushed out of the atria. This is where the problem lies, when blood is left to stand still is easily clots. These clots can then be thrown off around the body resulting in what can be fatal events, such as stroke or mesenteric ischaemia.

AF can be spotted on an ECG. First, understanding how a normal ECG related to the electrical activity within the cardiac muscle is crucial. In the image you can see a single heartbeat on an ECG. The P wave is the electrical impulse travelling across both atria from the sinoatrial (SA) node located in the right atrium, allowing the atrium to contract simultaneously. The electrical impulse then is delayed in the atrioventricular (AV) node at the top of the septum between the two ventricles, the PR segment. The signal then travels down the septum between the ventricles and up the walls through the purkinje fibres, causing the contraction of the ventricles from the bottom (apex), QRS complex. The contraction from the bottom of the ventricles is so that all the blood leaves the ventricles; think of it like squeezing all the toothpaste out of the bottle. The repolarisation and relaxation of the cardiac muscle is represented by the T wave.

AF can be spotted on an ECG as it has an irregularly irregular rhythm of the QRS complexes, as there is not regular activation of the AV node. The other sign is that there are no p waves present as the atria hasn’t got a clear electrical signal across them.

AF can either be a long-term condition or can have a sudden new onset. The new onset AF needs to be investigated for a cause, for example an infection, thyroid problems or mitral value prolapse. New onset can either be rate or rhythm controlled; this will depend on if there was a sudden known onset within the last 24-48 hours depending on hospital guidelines. If there was a clear start to the AF then DC cardioversion can be used as rhythm control, this involves shocking the heart, stopping it for a split second to allow it to reset back to a normal rhythm. Rate control can be achieved with beta-blocker, either orally or IV depending on the severity.

Long term these patients clot risks need to be assessed. This can be done through as scoring system called CHA2DS2-VASc

- C = congestive heart failure history -1pt

- H = hypertension – 1pt

- A = age >75years – 2pts

- D = diabetes mellitus – 1pt

- S = previous stroke/TIA/thromboembolism – 1pt

- V = vascular disease history – 1pt

- A = age >65yrs – 1pt

- S = female sex – 1 pt

If this score is >/= to 1 in a male, or >/= to 2 in a female then putting the patient on a blood thinner such as warfarin needs to be considered as they are at risk of their AF causing a condition such as stroke.

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