AV Blocks

Question 1

Types of AVN heart blocks

Answer 1

First degree
Second degree type 1
Second degree type 2
Third degree - complete

Question 2

Rhythm of first degree heart block

Answer 2

Regular

Question 3

PR interval of first degree heart block

Answer 3

Prolonged

Question 4

P wave and QRS complex in first degree heart block

Answer 4

Normal

Question 5

History of patient with first degree heart block

Answer 5

Asymptomatic and unremarkable exam

Question 6

Management of first degree heart block

Answer 6

Leave or stop AVN blocking drugs

Question 7

What is the difference between type 1 and type 2 second degree heart block

Answer 7

Type 1 has PR interval which gradually lengthen but type 2 has consistently normal PR interval.

Question 8

Rhythm of Mobitz type 1

Answer 8

Irregular

Question 9

Rhythm of Mobitz type 2

Answer 9

Irregular in 3:1 or 4:1 pattern

Question 10

P wave and QRS complex in Mobitz type 1

Answer 10

QRS complexes are occasionally dropped, not all P waves followed by QRS

Question 11

P wave and QRS complex in Mobitz type 2

Answer 11

More P waves than QRS complexes, intermittently dropped QRS

Question 12

What does a broad QRS complex tell you in Mobitz type 2

Answer 12

Broad rather than normal if conduction abnormality is located distal to bundle of His

Question 13

History of Mobitz type 1

Answer 13

Some can develop symptomatic bradycardia and present with pre-syncope and syncopal episodes

Question 14

History of Mobitz type 2

Answer 14

May have palpitations, pre-syncope and syncope

Question 15

Examination findings in Mobitz type 2

Answer 15

Regularly irregular pulse where there is a pattern of how many atrial depolarisations P waves lead to ventricular depolarisation QRS waves

Question 16

Examination findings in Mobitz type 1

Answer 16

Bradycardia

Question 17

Management of Mobitz type 1

Answer 17

AV blocking drugs stopped, pacemaker if symptomatic

Question 18

Management of Mobitz type 2

Answer 18

Cardiac monitor, underlying cause investigated, temporary pacing or isoprenaline may be required if the patient is haemodynamically compromised due to bradycardia

Question 19

P wave and PR interval in complete heart block

Answer 19

P waves present but not associated with QRS, PR interval absent as no AV dissociation

Question 20

QRS complex in complete heart block

Answer 20

Narrow or broad, depending on site of escape rhythm

Question 21

History of patient with complete heart block

Answer 21

Palpitations, pre-syncope, syncope, confusion, SOB, chest pain, sudden cardiac death

Question 22

Examination findings of patient with complete heart block

Answer 22

Irregular pulse, bradycardia, haemodynamic compronmise

Question 23

Management of complete heart block

Answer 23

Cardiac monitor.
Transcutaneous pacing/temp pacing wire or isoprenaline infusion may be required. Some rhythms may respond to atropine.
Permanent pacemaker may be required.

Question 24

Causes of right bundle branch block

Answer 24

Atrial septal defect, Brugada syndrome, RV hypertrophy, PE, rheumatic heart disease, myocarditis, cardiomyopathy, HTN

Question 25

Causes of left bundle branch block

Answer 25

Aortic stenosis, dilated cardiomyopathy, acute MI, extensive coronary heart disease, primary disease of cardiac electrical conduction system, aortic root dilatation/regurg, lyme disease, side effects of some surgeries

Question 26

ECG changes in right bundle branch block

Answer 26

QRS duration <120m/s, RSR pattern ('M' shape) in V1-3, wide slurred S wave in I, aVL and V5-V6

Question 27

ECG changes in left bundle branch block

Answer 27

QRS duration of <120m/s, dominant S wave in V1, broad monophasic R wave in I, aVL, V5-6, absense of Q waves in I, aVL, V5-6, R wave >60 in V5-6

Question 28

Complications of second degree type 2 heart block

Answer 28

Risk of progressing to symptomatic complete AV block and asystole

Question 29

Complications of third degree heart block

Answer 29

Sudden cardiac death from ventricular arrhythmias

Question 30

Causes of third degree heart block

Answer 30

Structural heart disease, Lev's and Lenegre's disease, MI, ischaemic CM, calcific aortic stenosis, dilated CM, amyloidosis, sarcoidosis, surgery, drugs, endocarditis, lyme disease, chagas disease, SLE, RA, thyroid dysfunction

Question 31

Causes of second degree heart block type 2

Answer 31

MI, fibrosis of conducting system, surgery, SLE, sclerosis, inflammatory conditions, infiltrative myocardial disease, hyperkalaemia, drugs, thyroid dysfunction,

Question 32

Causes of second degree heart block type 1

Answer 32

Increased vagal tone in athletes, drugs, inferior MI, myocarditis, surgery

Question 33

Complications of second degree type 1 heart block

Answer 33

May be haemodynamically compromised but this is rare

Question 34

Causes of first degree heart block

Answer 34

Enhanced vagal tone in athletes, post-MI, lyme disease, SLE, congenital, myocarditis, electrolyte derrangements, drugs and thyroid dysfunction

Question 35

Complication of first degree heart block

Answer 35

Does not usually progress to higher grade, may increase risk of AF