Atrial Fibrillation Flashcards
or atrial flutter
Explain to me what happens in atrial fibrillation
Electrical impulses are generated at sites other than the SA Node in the atria. these sites are called ectopic sites. commonly found at base of pulmonary vessels.
This results in random fibrillations of the atria, not all are contractions.
Because of refractory properties of AV Node, not all contractoins of atria pass through.
So it seems the atria and ventricles are contracting at random intervals to each other.
(youtube vid)
Define atrial fibrillation
DEFINITION: characterised by rapid, chaotic and ineffective atrial electrical conduction. Often subdivided into:
Permanent
Persistent
Paroxysmal
What a re the 3 types of atrial fibrillation?
Paroxysmal AF – irregular pulse that occurs sometimes and then stops. AFib stops by itself and the heart returns to normal rhythm. Recurrent episodes that stop on their own in less than 7 days
episodes lasting longer than 30 seconds but less than 7 days (often less than 48 hours) that are self-terminating and recurrent.
Persistent AF – AFib that does not stop by itself. Needs cardioversion. Recurrent episodes that last more than 7 days.
Permanent AF) – AFib that cannot be corrected by cardioversion. long-term episode
Describe HR in atrial fibrillation?
Can be slow; less than 60 bpm
Or fast; more than 100 bpm
Explain the aetiology and risk factors of atrial fibrillation
There may be no identifiable cause
Secondary causes lead to an abnormal atrial electrical pathway that results in AF
Systemic Causes; Thyrotoxicosis Hypertension Pneumonia Alcohol
Heart Causes ; Mitral valve disease Ischaemic heart disease Rheumatic heart disease Cardiomyopathy Pericarditis Sick sinus syndrome Atrial myxoma
Lung Causes;
Bronchial carcinoma
PE
Summarise the epidemiology of atrial fibrillation
VERY COMMON in the elderly
Present in 5% of those > 65 years
May be paroxysmal
Recognise the presenting symptoms of atrial fibrillation
Often ASYMPTOMATIC
Palpitations Syncope (if low output) SOB Chest pain --fatigue Symptoms of the cause of AF
What is the most common arrhythmia?
AF!
What are the signs of atrial fibrillation on physical examination?
Irregularly irregular pulse
Difference in apical beat and radial pulse
Check for signs of thyroid disease and valvular disease
Name appropriate investigations for AF?
ECG
Bloods
Echocardiogram
What would investigations in AF show?
ECG;
Undulating/Uneven baseline with absent p waves
Irregular intervals between QRS complexes
Atrial flutter = saw-tooth
Bloods; Cardiac enzymes TFT Lipid profile U&Es, Mg2+ and Ca2+
Because there is increased risk of digoxin toxicity with hypokalaemia, hypomagnesaemia and hypercalcaemia
Echocardiogram May show: Mitral valve disease Left atrial dilatation Left ventricular dysfunction Structural abnormalities
What is the difference between atrial fibrillation and atrial flutter?
They are both abnormal heart rhythms. … In atrial fibrillation, the atria beat irregularly. In atrial flutter, the atria beat regularly, but faster than usual and more often than the ventricles, so you may have four atrial beats to every one ventricular beat.
Name 4 cardiac enzymes.
Why do we look at cardiac enzymes in investigation for atrial fibrillation?
Troponin, Creatine kinase, Myoglobin, Lactate dehydrogenase
Atrial fibrillation confers a high risk of events i.e. stroke, HF and mortality.
Troponin is involved in myocyte contractility, elevated levels can foreshadow upcoming cardiovascular events.
Give a brief overview of the management plan for atrial fibrillation
First and foremost, try to treat any reversible causes (e.g. thyrotoxicosis, chest infection)
There are TWO main components to AF management:
- RHYTHM CONTROL; involves cardioversion
1b. RATE CONTROL; involves drugs
Then;
2. Manage stroke risk - anticoagualtion
last resort: ablation
In the management plan for atrial fibrillation what does rhythm control involve?
- If > 48 hrs since onset of AF;
- Anticoagulate for 6 weeks ideally (updt 2021) before attempting cardioversion
1a. If < 48 hrs since onset of AF
- Direct Current cardioversion (2 x 100 J, 1 x 200 J)
- Chemical cardioversion: flecainide or amiodarone
- NOTE: flecainide is contraindicated if there is a history of ischaemic heart disease 2. Prophylaxis against AF;
Sotalol - B blocker Amiodarone - antiarrhytmic (class 3) Flecainide - antiarrhythmic (class 1c) Consider pill-in-the-pocket (single dose of a cardioverting drug (e.g. flecainide) for patients with paroxysmal AF) strategy for suitable patients
Prolonged/ unresponsive to rounds of cardioversion and meds:
- Ablation (of bundles leading to AVN)
- should be followed by pacing ; pacemaker placement
In the management plan for atrial fibrillation what does rate control involve?
Used in Chronic (Permanent) AF
Control ventricular rate with - in order:
Beta-blockers - metoprolol, propranolol
Digoxin
Verapamil
Aim for ventricular rate ~ 90 bpm
What is the MOA of digoxin?
It is a cardiac glycoside. these drugs work by;
Increasing the output force of the heart and decrease its rate of contractions by acting on the cellular sodium-potassium ATPase pump
What is the MOA of verapamil?
Verapamil’s mechanism in all cases is to block voltage-dependent calcium channels.
Calcium channel blockers are considered class 4 antiarrhythmic agents.
Since calcium channels are especially concentrated in the SA & AV nodes, these agents can be used to decrease impulse conduction through the AV node, thus protecting the ventricles from atrial tachyarrhythmias.
Which drugs are used to in stroke prophylaxis in AF?
Which score is used to determine risk? Explain it.
Offer anticoagulation with a direct‑acting oral anticoagulant DOAC to people with atrial fibrillation and a CHA2DS2‑VASc score of 2 or above, taking into account the risk of bleeding. Apixaban, dabigatran, edoxaban
This is based on the CHADS-Vasc Score
HAS BLED score
Risk factors include:
Congestive HF Hypertension Age > 75 yrs Diabetes Stroke, TIA or Previous thromboembolic event
Vascular ,Valvular disease
Age 65-74
Sex; female increased risk
1 point for each but 2 points for previouse stroke and age over 75.
Identify the possible complications of atrial fibrillation
THROMBOEMBOLISM
Embolic stroke risk of 4% per year
Risk is increased with left atrial enlargement or left ventricular dysfunction
Worsening of existing heart failure
Summarise the prognosis for patients with atrial fibrillation
permanent AF doesnt return to sinus rhytym
How does the number of ectopic sites on the atria influence ECG results with atrial fibrillation?
Influences how undulating the baseline is! More ectopic sites = flatter baseline
How can AFs cause stroke?
Due to reduced atrial emptying, stagnation of blood in atria can lead to clot formation which can lead to stroke.
What does CHADSVASC tell you?
stroke risk PER YEAR
if you want lifetime risk -> how many more years to life expectancy eg 80 -> so then x by cahdscvacs risk
Indications for rate over rhythm control?
see ALS algorithm but if pt:
- Presents within 48hrs
- 4 adverse signs on bls; shock, etc
which is a non viable treatment in atrial flutter?
pacemaker
when we say rhythm control what do we mean?
these drugs can restore the rhythm eg bring about p waves and qrs complexes either in 1:1 ratio or whatever.
they are unlikely to slow it so will still be fast.
example is fleicanide
Rate comtrol in af is given?
IV
