Introduction to an ECG

Question 1

What planes may a standard limb lead perceive events in?

Answer 1

Forntal or vertical

Question 2

What structures are associated with the following SLLs:

SLL1
SLL2
SLL3

Answer 2

SLL1 - Left arm with respect to right arm

SLL2 - left leg with respect to right arm

SLL3 - left leg with respect to left arm

Question 3

What two basic principles are essential to understanding an ECG blip?

Answer 3

Approaching depolarisation causes and upward blip (visa versa)

Fast events are transmitted better than slow events

Question 4

What is the most important SLL and why?

Answer 4

SLL2 - records from right arm to left leg - the main wave of depolarisation passes down the axis of ventricles

Question 5

ECG recordings are always represented in from the LL relative to the RA

Answer 5

Thats not a question - just learn it

Question 6

What is represented by a P wave?

Answer 6

atrial depolarisation

Question 7

What is represented by the QRS complex?

Answer 7

Ventricular depolarisation

Question 8

What is represented by the T wave?

Answer 8

Ventricular repolarisation

Question 9

What is the PR interval and what is its typical duration?

Answer 9

The length of time between atrial and ventricular depol. - usually 0.12-0.2 seconds

Question 10

What is the typical duration of the QRS complex?

Answer 10

0.08 seconds

Question 11

What is the QT interval and what is its typical duration?

Answer 11

Time spend while ventricles are depolarised - normally about 0.42 seconds

Question 12

Why can’t we see atrial repolarisation?

Answer 12

It coincides with ventricular depol. - a much faster event that masks the atrial repol.

Question 13

Outline the components of the QRS complex

Answer 13

Q - inter-ventricular septum depol. from left to right

R- bulk of ventricle depolarises from the endocardinal to epicardial surfaces arising from the apex

S - the upper part of the inter-ventricular septum

Question 14

What pathologies may cause axis deviation of the heart?

Answer 14

Rotation, hypertrophy of left/atrophy of the right side of the heart

Question 15

What do augmented limb leads tell you?

Answer 15

Gives you other perspectives of the heart

Question 16

What do precordial leads give you?

Answer 16

Look at the same event but in the horizontal plane

Question 17

What kind of blips do the precordial chest leads produce?

Answer 17

Negative in V1 and positive in V6 - will flip somewhere in between

Question 18

What does the rhythm strip tell you?

Answer 18

Heart rate?
PR duration?
QRS complex width?
QT interval too long?
QRS complex preceded by a P wave

Question 19

STEMI vs NSTEMI

Answer 19

(non) ST elevated myocardial infarction - good classification f MI severity - STEMI is worse