Heart Block Flashcards
What is heart block?
HB = bradyarrhythmia caused by delay / interruption in electrical conduction between Atria + Ventricles
What are the causes of HB? (5 Cardiac, 4 Non-Cardiac, 4 Drug causes)
Cardiac: AV block / SA node dysf / Post MI / Inf End / Fibrosis w age
Non-Cardiac: Vasovagal / Hypothermia / Hypothyroidism / Raised ICP (bc HTN)
Drugs: Amiodarone / Beta blockers / Calcium Ch blockers / Digoxin (HF drugs)
How can a MI cause Heart Block?
AV node supplied by RCA
What is 1st Degree HB in simple terms?
Delayed conduction thru AV node
What is 2nd Degree HB in simple terms?
Progressive delayed conduction / intermittently blocked conduction
What is 3rd Degree HB in simple terms?
TOTAL interruption of conduction between Atria + Ventricles –> complete AV dissociation
What is seen on an ECG for 1st Degree HB?
CONSTANT PR prolongation (200+ ms)
What more srs conditions can 1st Degree HB be a sign of? (3 things)
- Inf End
- BBB
- Aortic Root Abscess
What are the 2 types of 2nd Degree HB?
- Mobitz Type 1 (Wenckebach)
- Mobitz Type 2
What is seen on an ECG of Mobitz Type 1 (Wenckebach)? (4 steps)
- Progressive lengthening of PR interval
- Followed by dropped beat (Wencke Wencke Wencke BACH)
- Followed by a normal conducted beat w shorter PR interval
- Cycle continues
What is seen on an ECG of Mobitz Type 2? (2 things)
- Constant PR interval
- Occasional missing QRS complex after P wave (naked P wave lol)
Why are there occasional missing QRS complexes after P waves in Mobitz Type 2?
Occasionally atrial conduction NOT transmitted to ventricles
What is a Fixed Ratio Block in Mobitz Type 2?
Fixed number of P waves each time before you get a QRS complex
How do you calculate the ratio of the Fixed Ratio Block in Mobitz Type 2?
Count number of P waves before QRS complex
e.g 2 P waves before every QRS complex = 2:1 Block
What is seen on an ECG of 3rd Degree Heart Block?
- Normal constant P waves
- Less + broad QRS complexes happening randomly (not linked w P waves bc complete AV dissociation)
Why are the QRS complexes not linked with P waves in 3rd Degree HB?
The atria and ventricles are not communicatin with each other
Which HB’s are asymptomatic? (2 things)
- 1st Degree HB
- Mobitz Type 1 (Wenckebach)
Which HB’s are symptomatic? (2 things)
- Mobitz Type 2
- 3rd Degree HB
What are the symptoms of HB? (4 things)
- Syncope
- Shock: Hypotension, Sweating, Pale, Increased CRT
- SOB
- Chest Pain
(1st Degree + Mobitz 1 = asymptomatic)
How is the diagnosis of HB made?
ECG
What are the management options for ALL HBs?
Identify reversible causes aka Elec imb / Meds induced causes
What HB’s don’t need treatment? (2 things)
- 1st Degree
- Asymptomatic Mobitz 1 Wenckebach
What is the management options for ASYMPTOMATIC 1st Degree HB?
No treatment
What is the management options for SYMPTOMATIC 1st Degree HB?
Pacemaker
