ECG

Question 1

What is the direction of depolarisation?

Answer 1

Endocardium to epicardium

Apex to base

Question 2

What cells are capable of generating their own contraction and at what speed do they contract?

Answer 2

SAN (90-100), AVN, (40-60), Bundle of His (15-30), Purkinje fibres

Question 3

What are the features distinctive to cardiac cells?

Answer 3

Intercalated disks - branching
Gap junctions - fast signalling
Many mitochondria
Large T tubules

Question 4

What is the process of depolarisation and repolarisation?

Answer 4

Action potential arrives
VOCC open and Ca2+ enters
CICR
Ca2+ binds to troponin causing a contraction
Unwind and relax
Ca2+ leaves via: pump into SR, NCX, NaKATPase

Question 5

What do the waves of an ECG represent

Answer 5

P - atrial depolarisation
QRS - ventricular depolarisation
T - ventricular repolarisation

Question 6

Where do leads I, II, III, aVF, aVL and aVR look?

Answer 6

Yeah just know this one

Question 7

What aspect of the heart do leads V1-6 look at?

Answer 7

1-2 septal
3-4 anterior
5-6 lateral

Question 8

What leads look at the inferior, anterior and lateral heart and which artery is likely responsible for damage in these areas?

Answer 8

Inferior - RCA - II, III, aVF
Anterior - LAD - V2,3,4
Lateral - LCx - V5,6, I, aVL

Question 9

What would you see on an ECG for left or right axis deviation?

Answer 9

Left leaving - I and III away. If II is negative it is pathological
Right returning - I and III toward each other

Question 10

What are some causes of LAD and RAD?

Answer 10

LBBB, WPW

RBBB, WPW

Question 11

Which way does an axis deviate towards when there is damaged myocardium and hypertrophy?

Answer 11

Away from damage, towards hypertrophy

Question 12

How can you calculate heart rate?

Answer 12

300 / number of large squares

Question 13

What is the normal range for a P wave?

Answer 13

Between 0.12 and 0.2 seconds

< 0.25mV

Question 14

What is the normal range for QRS complexes?

Answer 14

<0.12s

<35mm

Question 15

What is the normal range for T waves?

Answer 15

0.5-10mm

Positive

Question 16

How long is a normal QT interval

Answer 16

Less than half RRP interval

Question 17

Complications post MI (Darth Vader)

Answer 17

Death
Arrhythmia
Rupture
Tamponade
Heart failure
Valve disease
Aneurysm
Dressler's syndrome
Embolism
Recurrence

Question 18

What is the cut off for bradycardia and tachycardia?

Answer 18

<60bpm

>100pm

Question 19

Recognise AF, atrial flutter, PVC, VT, heart blocks, VF, asystole, STEMI, NSTEMI

Answer 19

As a medical student you should really be able to do this

Question 20

What is the mechanism behind ischaemia causing ST depression?

Answer 20

Ischaemia reduces Na+K+ATPase activity so K+ builds up in cell (questionable mechanism in my opinion) and Na/Ca as well cause depolarisation. Depolarisation generates nearby electrical currents raising the baseline of the ECG. When ventricles depolarise it goes to a seemingly lower level in relation to baseline

Question 21

What is the cutoff for ST depression and elevation?

Answer 21

> 1mm above/below baseline in 2 leads

Question 22

What is the mechanism behind ST elevation?

Answer 22

Injury delays depolarisation due to channels not letting sodium in

Question 23

Why may T wave inversion be present?

Answer 23

Repolarisation occurs endocardium to epicardium

Question 24

What are the criteria for pathological Q waves?

Answer 24

> 2mm deep
1mm wide
V1-3

Question 25

What is the pathway of electrical conduction in the heart?

Answer 25

SAN-AVN-Bundle of His-RBB/LBB-Purkinje Fibres