Heart Block

Question 1

How long is a normal QRS in seconds?

Answer 1

0.06-0.12 seconds

Question 2

How long can a normal QT interval be?

Answer 2

0.44 seconds

Question 3

What normally causes a heart block?

Answer 3

Abnormal conductance of the action potential at the AVN

Question 4

What is a first degree heart block?

Answer 4

An extended PR interval of over 0.20, requires no treatment

Question 5

Second degree mobitz type 1 heart block is?

Answer 5

Progressive prolongation of the PR interval culminating in a non-conducted P wave. Doesn’t usually require any intervention either

Question 6

Second degree mobitz type 2 heart block is?

Answer 6

Constant PR interval with intermittently non-conducted P waves and is caused by a conduction disorder in the bundle of Hiss. Always SINISTER and requires pacemaker

Question 7

Third degree heart block is?

Answer 7

Complete AV node dissociation causing a ventricular escape rhythm at around 30BPM. Results in narrow QRS if from the bundle of Hiss and broad if it’s originating in the ventricles. Requires pacemaker

Question 8

What are bundle branch blocks

Answer 8

Abnormal conduction patterns causing the QRS to become longer than 0.12 as bundles conduct slowly and late

Question 9

What does it mean for those reading the ECG of someone with a LBBB?

Answer 9

No interpretations can be made about the ST segment or T wave

Question 10

Signs of RBBB

Answer 10

QRS >0.12 seconds and secondary R wave and slurred S wave. Results in M appearance in V1-3 and W appearance in V6

Question 11

Signs of LBBB?

Answer 11

QRS >0.12 seconds M pattern in V5 and inverted T waves in leads I, aVL, V5-V6

Question 12

Causes of RBBB

Answer 12

PE and pulmonary heart disease

Question 13

Causes of LBBB

Answer 13

IHD, cardiomyopathy, idiopathic fibrosis

Question 14

What is the normal length of a PR interval in seconds?

Answer 14

0.12-0.20 seconds