Atrial Fibrillation

Question 0

Causes of AF

Answer 0

IHD, RHD, Thyrotoxicosis, HTN, PE, caffeine, Alcohol, Hypokalcemia, Hypomagnesemia

Question 1

Definition of AF

Answer 1

Chaotic, irregular atrial rhythm at 300-600bpm. Loss of effective atrial contraction reduces cardiac output by 10-20%

Question 2

Causes of irregularly irregular pulse

Answer 2

AF or multiple ectopics (distinguish from AF by exercise, ectopics disappear as diastole shortens)

Question 3

INR aims for AF

Answer 3

2-3

Question 4

Determine risk of stroke in AF

Answer 4

SADCHAVS
Stroke/TIA (2)
Age >75 (2)
DM (1)
Cardiac failure (1)
HTN (1)
Age >65 (1)
Vascular hx (1)
Sex female (1)

0: aspirin 1: either 2: warfarin

Question 5

Explain pulse deficit

Answer 5

Difference between radial pulse and apical rate w/ stethoscope

As rate increases diastolic filling time is reduced
Insufficient diastolic filling to create cardiac output (palpable pulse)
Sufficient to move valves (audible heart sound)

Question 6

How to assess control of AF?

Answer 6

Time the apical rate and compare to pulse rate taken at wrist.
If difference - Pulse Deficit

Question 7

Signs and Symptoms of AF

Answer 7

Signs: irregularly irregular pulse, apical rate different to radial pulse rate, 1st HS often variable in intensity, signs of LVF
Symptoms: none, palpitations, chest pain, SOB, faintness

Question 8

AF Investigations

Answer 8

ECG, U&E, cardiac enzymes, TFTs, ECHO

Question 9

Rate Control AF

Answer 9

1st line: beta-blocker, rate limiting Ca2+ blocker
2nd line: digoxin, amidarone

N.B. Don’t mix beta blockers and diltiazem or verapamil (bradycardia risk)

Question 10

Anti coagulation & AF

Answer 10

Acute: Heparin until workup then cardiovert or warfarin
Chronic: Warfarin (INR 2-3) or dabigatran if warfarin declined

Question 11

Cardio version regimen

Answer 11

O2 -> CCU -> IV sedation -> 200J -> 360J -> 360J (biphasic 200J)

Question 12

Drug Cardioversion

Answer 12

IV amiodarone (5mg/kg over 1 hr then ~900mg over 24h via central line or PO (200mg/8h for 1 week, 200mg/12h for 1 week, 100-200mg/24h maintenance)