Atrial fibrillation

Question 1

Explain the pathophysiology of atrial fibrillation

Answer 1

Reentry of depolarising signals in the atria cause the atria to contract out of sync, often at a fast pace, due to ectopic foci or re-entry rhythms

Question 2

What are the three mechanisms of re-entry rhythm?

Answer 2

Something increasing the excitability of the myocytes and decreasing the refractory period, like thyroxine (thyrotoxicosis) or adrenaline

Something slowing the conduction, which in turn would decrease the refractory period (the conduction itself took long enough so the muscles don’t have to wait even longer to transmit another impulse)

A condition that increases atrial volume; lengthens the circuit duration and therefore almost acts like it’s slow conduction, so increases excitability of the muscle

Question 3

Define AF

Answer 3

Supraventricular tachycardia with absent P waves and irregularly irregular pulse

Question 4

Describe the pulse in AF

Answer 4

Weak (as the ventricles aren’t filling enough so they aren’t pumping enough)
Irregularly irregular due to the atrial flutter

Question 5

Where do the re-entry rhythms arise from?

Answer 5

Myocardial sleeves of pulmonary vein usually

Question 6

Classify AF

Answer 6

Paroxysmal (resolves within 7 days)

Persistent (more than 7 days)

Question 7

Describe the ECG changes with AF

Answer 7

Absent P wave
Irregularly irregular rhythm (between RR intervals)
Narrow QRS complexes (as it’s a tachycardia)
f waves on isoelectric line (oscillations)*

NOTE: not capital F for atrial flutter which is creates a regular saw tooth appearance

Question 8

Distinguish between atrial flutter and atrial fib on an ECG

Answer 8

Atrial fibrillation - up and down on isoelectric line; f wave between t and p waves
Atrial flutter - F wave, regular oscillations, saw tooth appearance

Question 9

Symptoms

Answer 9

Palpitations
SOB
Dizziness/faintness

Question 10

Signs

Answer 10

Irregularly irregular pulse

Tachycardia

Question 11

Investigations

Answer 11

ECG
Bloods
Echocardiogram

Question 12

Management is split into how many components and what are they?

Answer 12

Treat any reversible causes e.g. chest infection or thyrotoxicosis 
Then: 
RATE control 
RHYTHM control 
Stroke prophylaxis

Question 13

Rhythm control management

Answer 13

If AF was less than 48hrs ago (acute)
DC cardioversion or oral cardioversion = flecainide (slows electrical signals) or amiodarone (K+ channel blocker)

If AF was more than 48 hours ago, wait 3-4 weeks before DC cardioversion
In the mean time give anticoagulant

Question 14

Rate control management - explain and state which patients this is given to

Answer 14

Pts with permanent AF

Digoxin (Na+/K+ ATPase inhib, so increases FOC and reduces contractility as more Na+ is kept inside the cell)
Verapamil (CCB)
Beta blockers

Question 15

Explain stroke prophylaxis and what score this is based on

Answer 15

CHADS-Vasc score
High risk pts - anticoagulate with warfarin
Low risk - aspirin (antiplatelet, blocks COX-1 and therefore prevents formation of TXA2, needed for platelet aggregation and vasoconstriction)

Question 16

What is the CHADS Vasc score based on?

Answer 16

Age
Sex
Diabetes
HTN
Previous vascular history e.g. MI 
Thromboembolism/stroke/TIA

Question 17

Prophylaxis for AF

Answer 17

Sotalol (beta blocker)
Amiodarone
Flecainide
Consider pill-in-the-pocket (single dose of a cardioverting drug (e.g.
flecainide) for patients with paroxysmal AF)

Question 18

Complications

Answer 18

Thromboembolism

Question 19

Prognosis

Answer 19

Permanent if pt has heart conditions already

Question 20

Risk factors

Answer 20

HTN 
Ischemic heart disease 
Valve problems
Diabetes
Thyroid diseases
COPD/obstructive sleep apnoea (lack of oxygen causes atrial spasm) 
Coronary artery disease
Old age

Question 21

Which scoring system is used?

Answer 21

CHADS Vasc

Question 22

Causes

Answer 22

Thyrotoxcois
hypokaelmia
MI
Pulmonary ??