Atrial Fibrillation

Question 1

What is Atrial fibrillation?

Answer 1

Continuous rapid activation of atria due to multiple meandering reentry wavelets often driven by rapidly depolarizing foci, located predominantly within the pulmonary veins.

Question 2

What is the epidemiology of common arrhythmias?

Answer 2

1 - 2% of the general population

5 - 15% of patients over 75 years

Question 3

What principle underlies the cause of atrial fibrillation?

Answer 3

Any condition that results in raised atrial pressure, increases atrial muscle mass, inflammation, fibrosis and infiltration of the atrium can cause atrial fibrillation.

Question 4

Most common cause of atrial fibrillation?

Answer 4

Hypertension

Heart

Question 5

What are the classic causes of hypertension?

Answer 5

1. Alcohol intoxication
2. Rheumatic Heart Disease
3. Thyrotoxicosis

Question 6

What are the types of Atrial fibrillation?

Answer 6

1. First detected - irrespective of duration or severity of symptoms
2. Paroxysmal - stops spontaneously within 7 days
3. Persistent - continuous >7days
4. Long persistent - continuous > 1year
5. Permanent - continuous, with a decision between patient and physician to cease further attempts to regain sinus rhythm
6. Lone AF

Question 7

Why is atrial fibrillation classification important?

Answer 7

Is important in choosing between rhythm restoration and rhythm control

Question 8

Typical history of patients with Afib?

Answer 8

1. Can be asymptomatic
2. Can be so severe they came in with chest pain, dyspnoea, palpitations, fatigue
3. History of consumption of caffeine

Question 8

Typical history of patients with Afib?

Answer 8

1. Can be asymptomatic
2. Can be so severe they came in with chest pain, dyspnoea, palpitations, fatigue
3. History of consumption of caffeine, alcohol, digitalis, theophylline
4. May have +ve Hx of IHD, HTN, RHD, Congenital heart disease (atrial septal defect, ventricular septal defect), COPD

Question 9

What are the complications of Afib?

Answer 9

1. cardiomyopathy
2. stroke
3. embolism to kidneys, liver, muscles etc.

Question 10

What are some of the examination findings in a patient with atrial fibrillation?

Answer 10

1. Irregularly irregular pulse and pulse deficit
2. Warm hands, goitre, pretibial myxoedema: elevated blood pressure from HTN
3. Malar flush if associated with mitral stenosis
4. Elevated JVP without ‘a’ waves
5. Mitral valvotomy scar
6. Varying intensity of first heart sound
7. You can tell examination that to differentiate between multiple ventricular ectopics, patient is asked to exercise (AF can be normal or worse with exercise but Ventricular ectopics diminishes in frequency)

Question 11

What are the components of CHADSVASc scoring system for non-valvular Atrial fibrillation?

Answer 11

Is used in patients with non vulvular atrial fibrillation (absence of mitral stenosis, artificial heart valves, mitral valve repair), this scoring system is used.

C   Congestive Heart failure
H   Hypertension
A2 Age >=75
D   Diabetes mellitus
S2 Stroke/TIA/Thromboembolism
V   Vascular disease (coronary, aorta, peripheral arteries)
A   Age 65 - 74
Sc Sex category: female

Question 12

What is the Annual risk of stroke of CHADVASc scoring system for non-valvular Atrial fibrillation?

Answer 12

0 points = 0%risk. No prophylaxis
1 point = 1.3% risk: Anticoagulant (oral) or aspirin
2+ points = 2.2% risk: Oral anticoagulant

Question 13

What are the components of HAS-BLED Score?

Answer 13

Hypertension
Abnormal renal function
Abnormal liver function
Alcohol intake at same time
Stroke in past
Bleeding
Labile INRs
Elderly: She >=65 years
Drugs as well

Question 13

How would you investigate a patient with AFib?

Answer 13

1. Thyroid function tests to exclude Thyrotoxicosis
2. ECG (transthoracic and transesophageal) is useful to determine left atrial size and left ventricular function and to exclude vulvular heart disease and intracardiac thromboemboli
3. Exercise treadmill (if the patient is not in heart failure) AF is precipitated by exercise.
4. 24 hour ambulatory Holter monitoring

Question 13

What are some causes of irregularly irregular pulse?

Answer 13

1. Atrial flutter
2. Atrial fibrillation
3. Complete heart block
4. Multiple ventricular ectopics

Question 14

What are the ECG findings in Atrial fibrillation?

Answer 14

1. No clear P waves
2. Fine oscillations of the baseline (f waves)
3. The QRS rhythm is rapid and irregular
4. RR interval is irregularly irregular
5. Untreated, the ventricular rate is usually 120 - 180/min but it slows with treatment

Question 15

What are the principles of management of AFib?

Answer 15

1. Control the rate
2. CHAD score and Anticoagulant
3. Cause: look for the cause
4. Correct the rhythm: cardioversion (electrical or chemical) or AF Ablation

Question 17

Long term management of AFib?

Answer 17

1. Rhythm control
   - Class Ia (Procainamide, quinidine) or class Ic (Flecainide, Propafenone) or class III (Sotalol, Amiodarone)
   - left ventricular hypertophy or heart failure only Amiodarone is recommended
   - coronary artery disease class III Sotalol or Amiodarone
   - patients with paroxysmal atrial fibrillation or persistent atrial fibrillation may be treated with left Atrial ablation.
2. Rate control
   Class II and IV
   Digoxin monotherapy may be sufficient for elderly, non-ambulant patients.

In younger patients, effect of catecholamines overwhelms the vagotonic effect of digoxin hence additional AV nodal slowing agents needed.

Ventricular rate considered to be controlled if the resting heart rate is <110bpm but stricter control between 60and 80bpm at rest and <110bpm during moderate exercise.

To assess the adequacy of rate control, an ECG strip may be sufficient in elderly patient but ambulatory 24 hour Holter monitoring and exercise stresytest (treadmill) are needed in younger individuals.

Older patients with poor rate control despite optimal medical therapy should be considered for AV node ablation and pacemaker implantation (ablate and pace strategy). Lifelong anticoagulation.

Anticoagulant
Indicated in patients with AFib related to mitral valve stenosis or mechanical prosthetic valve.
In non vulvular atrial fibrillation, CHADVASc is used as first step in assessing the need for anticoagulation.

Warfarin dose adjusted to maintain INR between 2 and 3
NOACS
- Direct thrombin inhibitors dabigatran
- Direct Factor Xa inhibitors rivaroxaban or apixaban

Advantages of NOACS

• Unlike warfarin which blocks several Vit K-dependent (factors II, VII, IX, X), blocks a single step
• faster onset of action
• shorter half life
• fewer drug and food interactions
• do not require INR testing
• Trial data has shown them to be equally effective as, and safer than warfarin.

NB: dose reduction or avoidance in patients with renal impairment and elderly with low body weight.

Question 19

Acute Management of AFib?

Answer 19

1. When atrial fibrillation is due to an acute precipitating event, such as alcohol toxicity, chest infection or Thyrotoxicosis the provoking cause should be treated.
2. Ventricular rate control using digoxin in combination with B blockers or non-dihydropyridine calcium-channel blockers (verapamil or diltiazem).
3. Cardioversion electrically by DC shock or medically by intravenous infusion of class I (Flecainide or Propafenone) or class III (amiodarone or sotalol).

NB:
- Biphasic vs Monophasic
- Anticoagulant before and after cardioversion
- If urgent, transesophageal echocardiography
then assessed for the need of anticoagulation therapy