Arrythmias Flashcards
Define Atrial fibrillation
Atrial fibrillation (AF) is a chaotic irregular atrial arrhythmia and is considered a type of supraventricular tachycardia (SVT).
What is atrial fibrillation?
- Atrial fibrillation is an irregular and often very rapid heart rhythm (arrhythmia) that can lead to blood clots in the heart.
- Increases the risk of stroke, heart failure and other heart-related complications.
- Atrial fibrillation is often described as having a ‘rapid ventricular response
‘ once the ventricular rate is > 100 bpm.
What are the types of atrial fibrillation?
- Types of Atrial fibrillation
- First episode
- Paroxysmal: recurrent episodes that stop on their own in less than 7 days (comes and goes)
- Persistent: recurrent episodes that last more than 7 days (last weeks to months without self terminating)
- Permanent: continuous atrial fibrillation that is also refractory to treatment. Management is aimed at rate control and anticoagulation, if appropriate. (last more than 12 months)
What is the aetiology of atrial fibrillation?
The Royal College of Emergency Medicine’sPIRATES
mnemonic describes a few potential underlying causes of Atrial fibrillation.
Pulmonary; PE and COPD
Ischaemic heart disease: including heart failure
Rheumatic heart disease: any valvular abnormality
Anaemia, alcohol, advancing age
Thyroid disease; hyperthyroidism
Electrolyte disturbance e.g. hypo/hyperkalaemia and hypomangnesemia
Sepsis and sleep apnoea
Atrial fibrillation is classically considered a disease of theelderly, however, it often also occurs secondary to other disease states such as sepsis and hyperthyroidism.
What is the pathophysiology of atrial fibrillation?
- Normally, the sinoatrial node produces organised electrical activity that coordinates the contraction of the atria of the heart.
- Atrial fibrillation is where the contraction of the atria is uncoordinated, rapid and irregular.
- This is due to disorganised electrical activity that overrides the normal, organised activity from the sinoatrial node.
- It is theorised that regular, physiological impulses produced in the sinoatrial node are overwhelmed by the presence ofrapid, uncoordinated electrical discharges
produced in the atria.
- This disorganised electrical activity in the atria also leads to irregular conduction of electrical impulses to the ventricles. This results in:
- Irregularly irregularventricular contractions
- Tachycardia
- Heart failuredue topoor fillingof the ventricles duringdiastole
- Risk ofstroke
- The pooling of blood in the atria predisposes patients to thromboembolic events, particularly stroke.
- Atrial fibrillation increases the risk of a stroke by around 5 times.
- Anischemic strokeis the type of stroke most associated with the irregular heartbeat of atrial fibrillation.
AF is usually associated with an abnormal atria as a result of underlying heart disease.
Dilation of the atria with fibrosis and inflammation causes a difference in refractory periods within the atrial tissue and promotes electrical re-entry that results in AF.
What is the epidemiology of atrial fibrillation?
- Atrial fibrillation is the most common cardiac arrhythmia and is estimated to affect approximately 2.5% of the general population
- More common with increasing age
- M>F
- AF affects approximately 5% of patients aged 70-75 years, and 10% of patients aged 80-85 years.
What are the symptoms of atrial fibrillation?
- Chest pain: red flag
- Syncope (fainting): red flag
- Dyspnoea
- Shortness of breath
- Palpitations
- Dizziness
- Fatigue
What are the signs of atrial fibrillation?
- Hypotension:red flag; suggest haemodynamic instability
- Evidence of heart failure:red flag; such as pulmonary oedema
- Irregular irregular pulse
- Tachycardia
What are the primary investigations of atrial fibrillation?
- Primary investigations
-
ECG:irregularly irregular QRS complexes with absent P waves and chaotic baseline
- 24-hour ambulatory ECG monitoring is recommended for those with paroxysmal AF in the community
- Evidence of new myocardial ischaemia warrants immediate DC cardioversion
- KardiaMobile: this is an innovative single-channel cardiac event recorder; as per NICE 2022, it is recommended for detecting suspected paroxysmal AF in people who present with palpitations and are referred for an ambulatory ECG
- Serum urea and electrolytes:in addition to standard electrolytes, serum magnesium, calcium and phosphate should also be assessed
- TFTs (Thyroid function tests): hyperthyroidism is a secondary cause of AF
-
ECG:irregularly irregular QRS complexes with absent P waves and chaotic baseline
What’s are other investigations to consider for atrial fibrillation?
- chest pain is present as this may reflect an myocardial infarction
-
Chest x-ray:if there is suspicion of heart failureto assess for pulmonary oedema
- Heart failure due to Atrial fibrillation is an adverse feature that requires electrical cardioversion
- Transthoracic ECHO:consider if there is a suspicion of underlying structural or functional heart disease; usually performed prior to cardioversion in chronic cases
- Persistent Atrial fibrillation → ECG (irregular p waves with twitching, irregular intervals in QRS complex
- Paroxysmal Atrial fibrillation → Holter monitor (portable device, monitors rhythm and records episodes )
What are the adverse features of atrial fibrillation?
The presence of adverse features guides the decision to undergo DC cardioversion.
- Shock: hypotension (systolic blood pressure <90 mm Hg), pallor, sweating, cold, clammy extremities, confusion or impaired consciousness
- Syncope: transient loss of consciousness
- Myocardial ischaemia: typical ischaemic chest pain and/or evidence of myocardial ischaemia on 12-lead ECG
- Heart failure: pulmonary oedema and/or raised jugular venous pressure
What is the management for atrial fibrillation?
- Lifestyle changes
- Beta blockers
- Medications to control heart rate and reduce clotting
- Implantable pacemaker —> constantly pace atrium
- Radiofrequency catheter ablation —> maze procedure, AV node ablation
- Determine if rate control or rhythm control is more appropriate.
- As per NICE guidelines,rate control is generally preferred, except inspecificcircumstances
- Rate controlaccepts the fact that the patient is not in sinus rhythm, but the aim is to get the heart rate below 100 to extend the time during diastole when the ventricles can fill with blood.
- Rhythm controlaims to restore normal sinus rhythm and is known as ‘cardioversion’, can either be electrical or pharmacological
What is the management for Haemodynamically unstable? Afib
- Emergency electrical synchronised DC cardioversion
- See the ‘adverse features’ above for full indications for synchronised DC cardioversion
What is the management for Haemodynamically stable Afib?
-
Haemodynamically stable
- Onset of AF < 48 hours: 1) rate control or 2) rhythm-control (either pharmacological or electrical)
-
Onset of AF > 48 hours / unknown onset: offer rate-control and anticoagulation (following a risk assessment) for at least 3 weeks, then offer rhythm control (preferably electrical) if appropriate e.g. if rate control is unsuccessful or the patient remains symptomatic
- The switch from rate control to rhythm control is a high-risk period for embolisation resulting in a stroke. This is due to the formation of a thrombus in a fibrillating atrium which can embolise to the brain when sinus rhythm is restored
-
First line: beta-blocker(except sotalol) (e.g. bisoprolol) or arate-limiting calcium-channel blocker (e.g. verapamil)
- Digoxin: may be considered first-line in patients with AF and heart failure, as well as those who do no or very little exercise or other rate-limiting drugs have been excluded
- Non-cardioselective beta-blockers (e.g propranolol) should beavoidedin asthmatic patients due to the risk of bronchospasm
- Avoid calcium channel blockers in patients with heart failure.
-
Second line: (if refractory??) if ongoing symptoms then consider combination therapy withany 2 of the following:
- Beta‑blocker (e.g. bisoprolol)
- Diltiazem
- Digoxin
-
First line: beta-blocker(except sotalol) (e.g. bisoprolol) or arate-limiting calcium-channel blocker (e.g. verapamil)
What is the management for Afib Haemodynamically stable rythmn control?
-
Pharmacological:
- Flecainide or amiodarone: if no evidence of structural/ischaemic heart disease
- Amiodarone: if structural/ischaemic heart disease is present
-
Electrical cardioversion:rapidly shock the heart back into sinus rhythm
- Synchronised DC shock starting at 150J under short-acting general anaesthesia
- Preferred method of rhythm control in patients with AF > 48 hours / unknown onset. Amiodarone should be considered 4 weeks before and up to 12 months after electrical cardioversion to maintain sinus rhythm
