Conduction disorder

Question 1

What would you see on RBBB + LBBB

• Pathophysiology, Causes + MX?

Answer 1

BBB= QRS complex >120ms

RBBB: heart block in right bundle branch of electrical conduction system
- Causes: RVH, Cor pulmonale, PE, MI, ASD, Cardiomyopathy, myocarditis
- ECG changes: MARROW = ‘M’ in V1, ‘W’ in V6

LBBB: heart block in left bundle branch of electrical conduction system
- Causes: IHD, HTN, Aortic Stenosis, Cardiomyopathy
- ECG changes: WILLIAM = ‘W’ in V1, ‘M’ in V6
- Note: new LBB is pathological and sign of MI

Management
- Pacemaker

Question 2

AF: causes, syx, ix, mx inc acute mx

Answer 2

Causes (SMITH):
- Sepsis, Mitral valve disease, IHD, Thyrotoxicosis, HTN
- Others: caffeine, hypokalaemia

Syx
- ASyx
- CP, Palpitations, SoB, Syncope

Ix
(1.) Bloods: FBC, UE, cardiac enzymes, TFT
(2.) ECHO
(3.) ECG
- Irregularly irregular ventricular rhythm
- Absent p waves
- Narrow QRS complex
- Tachycardia

Mx
Acute mx if shock, MI, syncope, HF
- ABCDE
- Senior input
- Heparin
- DC cardioversion
- Correct electrolyte: K+, Mg, Ca

AF Mx
(1.) Rate control: Bb or CCB (1st line), dual combination of CCB, BB, digoxin (2nd line)
- do not rate control if: reversible cause, new onset <48hrs, HF

(2.) Rhythm control: cardioversion
- Immediate: syx <48hr, unstable
- Delayed: syx >48hrs, stable, hi risk of emboli requires antcoag for 3w
- Electrical or pharm (flecanide, amiodarone) cardioversion

(3.) Life-long anticoagulation: DOAC (1st), Warfarin (2nd line)
- CHADSVASC: assess if pt with AF needs anticaog. Higher the score, the higher the risk of stroke or TIA and thus greater benefit from anticoag.
- ORBIT/HASBLED assess risk of major bleed whilst on anticoag

Question 3

Atrial flutter - what is it? , ECG pattern? Mx

Answer 3

• Arrythmia due to atria and ventricles beat to different speeds
• There is rapid atrial depolarisation
• Associate conditions: HTN, IHD, Cardiomyopathy, Thyrotoxicosis

ECG - saw tooth pattern

Mx, similar to AF
1. If unstable -> cardioversion
2. If stable -> Rx reversible cause (e.g. sepsis, thyrotoxicosis) or rate control with BB, CCB or cardio version
3. Radiofrequency ablation of re-etrant rhythm

Question 4

what is Paroxysmal AF?

Answer 4

Af episodes terminate spontaneously usually <24hrs but can be <7d.

Question 5

What are the types of AV block + mx?

Answer 5

Impaired electrical conduction between atria and ventricles.

1st degree HB
- PR interval >0.2s
- Asyx do not need rx

2nd degree HB
- Mobitz 1/Wenckeback – prolongation of PR until dropped beat
- Mobitz 2 – constant PR interval + dropped beat

3rd degree HB/complete hb
- No association between P wave + QRS complex

Mx
(1.) Stable – observe
(2.) Unstable or risk of asystole (Mobitz 2, 3rd degree)
- IV atropine
- If hi risk = temporary transvenous cardiac pacing
- Permanent pacemaker

Question 6

SVT: causes, types, mx

Answer 6

• Narrow complex tachycardia caused by the electrical signal re-entering the atria from the ventricles
• Paroxysmal SVT describes a situation where SVT reoccurs and remits in the same patient over time

Types
(1.) AVN re-entrant tachycardia = re-entry point is back through AV node.
(2.) AV re-entrant tachycardia e.g. WPW = re-entry point is an accessory pathway
- WPW = extra pathway is known as the Bundle of Kent.
- ECG: short PR, delta wave i.e. slurred upstroke on QRS
(3.) Atrial tachycardia = electrical signal originates in the atria somewhere other than SAN. Abnormally generated electrical activity from ectopic

Acute mx
(1.) Continuous ECG monitoring
(2.) Valsalva manoeuvre – ask pt to blow hard against resistance
(3.) Carotid sinus massage
(4.) IV Adenosine (CI asthma/COPD/HF/heart blocks/hypotension – use verapamil), warn pt of impending doom
(5.) DC cardioversion if above fails

Chronic/recurrent episodes Mx
- Bb, CCB, amiodarone
- Radiofrequency ablation

WPW Mx
- Radiofrequency ablation

Question 7

What is VT + VF? Ix + Mx?

Answer 7

VT
- Broad complex tachycardia originating from ventricular ectopic foci. It has the potential to lead to VF.

Ix:
- Bloods: FBC, UE, cardiac enzymes, TFT, drug toxicology screen
- CXR
- ECG: tachycardia, absent P waves, board QRS

Mx: ABCDE + ECG
(1.) VT + no adverse signs – IV Amiodarone
(2.) VT + Adverse signs (BP <90, Ischemia, Shock, Syncope, HF) – synchronised DC shock
(3.) VT + pulseless – ALS, unsynchronised shock, CPR, adrenaline, amiodarone

VF
- Irregular broad complex tachycardia, always a pulseless rhythm

IX
- Bloods: FBC, UE, cardiac enzymes, TFT, drug toxicology screen
- Imaging: CXR, ECHO, Coronary angiogram
- ECG: QRS complexes are polymorphic and irregular

Mx
- ABCDE, BLS
- Unsynchronised cardioversion
- CPR
- Adrenaline + amiodarone