ECG

Question 1

Where are leads attached to?

Answer 1

Left leg, left arm, right arm

Question 2

What shape does this form? What name is given to the sides of the triangle?

Answer 2

Standard Limb leads

I,II,III

Question 3

Describe the Standard Limb leads

Answer 3

I= right arm to left arm
II= left leg to right arm
III= left leg to left arm
(i.e. looking from the left leg(+ve) towards the right arm (-ve)

Question 4

What plane do these allow us to see in?

Answer 4

Frontal plane

Question 5

What other plane can we analyse?

Answer 5

The Transverse plane

Question 6

How can we analyse the Horizontal Plane?

Answer 6

Using the precordial probes (V1-V6)

Question 7

How do the readings on the precordial leads vary?

Answer 7

V1= very negative= depolarisation travelling away
v3-v4 = in the middle
V6= very positive= depolarisation approaching

Question 8

Which sll shows the strongest R wave and why?

Answer 8

SLL II shows the strongest because it is on the axis of the approaching depolarisation.

Question 9

Why are there three parts to the QRS complex?

Answer 9

Q= depolarisation left to right of interventricular septum. 
R= cumulative depolarisation of bulk of the ventricles from endocardium to epicardium. resultant vector= towards apex of heart 
S= depolarisation of upper part of the interventricular septum.

Question 10

What forms the P wave?

Answer 10

Atrial depolarisation

Question 11

What forms the QRS wave?

Answer 11

Ventricular Depolarisation

Question 12

What is the T wave?

Answer 12

Ventricular Repolarisation

Question 13

Why is the T wave positive?

Answer 13

Because it is repolarisation travelling away from the electrode- so the remote electrode becomes more negative- so the reference is positive.

Question 14

Which SLL shows the weakest R wave and when might this not be the case?

Answer 14

SLL1 as it is perpendicular to the depolarisation

But if the heart is deviated to the left then SLL 1 will show the strongest signal.

Question 15

Why does the plateau not show up?

Answer 15

Because the ECG can only pick up rapid changes

Question 16

Why can you not see atrial repolarisation?

Answer 16

Because this overlaps with ventricular depolarisation which is a much bigger signal so it occludes the atrial repolarisation.

Question 17

What is the PR interval?

Answer 17

Time between the start of atrial depolarisation and the start of ventricular depolarisation= 0.12-0.2 secs

Question 18

What is the time taken for QRS complex?

Answer 18

around 0.08 seconds shouldn’t be greater than 0.12secs

Question 19

What is the QT interval?

Answer 19

Complete time for ventricle to depolarise and repolarise. Varies with HR but should be 0.42 at 60bpm.

Question 20

What is SINUS RHYTHM?

Answer 20

When every QRS is preceded by a P wave.

Question 21

Define Tachycardia and Bradycardia

Answer 21

Tachycardia= HR over 100bpm (at rest)
Bradycardia= HR under 60 bpm

Question 22

Which leads allow us to read in the frontal plane?

Answer 22

SLL and Augmented Limb Leads

Question 23

Define Augmented Limb Leads

Answer 23

These are stretching from one SLL to the middle of the other two- so give a reference with respect to both of the other SLL.
aVR= from right arm to mid SLL 111
aVL= from left arm to mid SLL11
aVF= from left foot to mid SL1

Question 24

Explain the concept of a rhythm strip and what we can read from it?

Answer 24

Should run at 25mm/sec and each big square = 0.2 sec= 5mm
So if we the number of R-R in 30 squares (6 secs)
HR = R-R waves in 6 secs x 10
Should be around 60-100 bpm

Question 25

What condition is related to the term STEMI?

Answer 25

Myocardial Infarction

A STEMI= st elevated MI

Question 26

Which is more severe- a STEMI or NSTEMI?

Answer 26

STEMI= very severe MI