CVS - ECG

Question 1

What is special about purkinje cells?

Answer 1

Transmit cardiac APs rapidly due to reduce myofibrils and increased mitochondria

Question 2

What is the order of repeal of cardiac tissue?

Answer 2

Opposite to depol so last to depol is first to repol

Question 3

Where do the bundle branches lay within the myocardium?

Answer 3

Subendocardially in the septum

Question 4

What is the ECG actually recording from the cell?

Answer 4

Records electrical activity from the surface of the myocyte

Question 5

Is a + deflection on an ECG towards or away from electrode?

Answer 5

Towards

Question 6

Why isn’t SAN signal on ECG?

Answer 6

Too small to pick up

Question 7

How does atrial depolarisation travel across atria?

Answer 7

Via atrial muscle fibres and internodal pathways

Question 8

Which antihypertensive drug can cause heart block?

Answer 8

Calcium channel blockers

Question 9

What does the Q wave R wave and S wave denote on an ECG?

Answer 9

Q - Septal depol L-R
R - Depolarisation of apex and free ventricular wall (large and positive as large amount of myocardium and towards electrode)
S - End of depolarisation up towards base of heart - small and away from + electrodes

Question 10

Abnormal rhythms arise from abnormal _______ _______ and/or abnormal ________

Answer 10

Impulse formation

Conduction

Question 11

Where would the P wave be for a high, middle, low junctional beat?

Answer 11

Before QRS
In QRS
After QRS

Question 12

How come only some impulsed from AF arrive at ventricles?

Answer 12

Impulses arrive at AVN at irregular rate - conducted to ventricles when AVN not refractory

Question 13

3 characteristics of AF on ECG

Answer 13

No P wave
Irregularly irregular
Fibrillary F waves

Question 14

3 Causes of heart blocks?

Answer 14

Post MI - most common
Degenerative - fibrotic
Drugs - Ca channel blockers

Question 15

Definition of VT?

Answer 15

3 or more successive beats originating from the ventricles

Question 16

Why is subendocardial tissue more at risk in MI?

Answer 16

Coronaries lie on epicardial surface and sub endocardial muscle is furthest away so most vulnerable to becoming ischaemic

Question 17

Why do you get ST and T wave changes in ischaemia?

Answer 17

Abnormal current during repolarisation

Question 18

What does ST elevation signify, compared to pathological Q waves?

Answer 18

• Epicardial injury

- Myocardial necrosis

Question 19

How do you measure to see if Q waves are normal or pathological?

Answer 19

Pathological if:
>1 small square wide
>2 small squares deep
Depth of more than 1/4 of subsequent R wave

Question 20

What effect on the ECG do you see with hyperkalaemia and hypokalaemia?

Answer 20

Hyper - High T wave, eventually prolonged PR –>atrial standstill –> VF

Hypo - Low T wave high U wave (increases the more hypokalaemic you go)