Cardiac Channelopathies

Question 1

What are two syndromes associated with Cardiac channelopathies

Answer 1

long QT and short QT

Question 2

What is affected in long and short QT syndromes

Answer 2

changes to ventricular myocyte APs

Question 3

What interval of the cardiac cycle do LQT and SQT affect

Answer 3

QRS wave to T wave

Question 4

Which wave changes in QT syndromes

Answer 4

T wave changes

Question 5

What is the effect of the T wave changing in QT syndromes

Answer 5

repolarisation is accelerated or delayed

Question 6

What is the ventricular action potential plateau phase mediated by

Answer 6

voltage gated calcium channels

Question 7

What is the T wave in ventricular APs associated with

Answer 7

repolarisation phase

Question 8

What is ventricular tachycardia

Answer 8

additional beat - number of contractions in ventricles is increased

Question 9

What is ventricular fibrillation

Answer 9

fatal - completely un co-ordinated contraction of ventricular myocytes

Question 10

What can occur in long QT

Answer 10

ectopic beat

Question 11

What are the implications of QT syndromes

Answer 11

signals dont spread where they should

Question 12

What is a form of tachycardia highly associated with ventricular fibrillation - death

Answer 12

torsades de pointes

Question 13

What is torsases de pointes associated with in an ECG

Answer 13

twisting motion

Question 14

Mutations in what channels cause Long QT

Answer 14

KCNQ1, SCN5A, KCNE1, CACNA1C

Question 15

What is KCNQ1

Answer 15

voltage gated potassium channel

Question 16

What mutation affects KCNQ1 in Long QT

Answer 16

loss of function

Question 17

What is SCN5A

Answer 17

sodium channel

Question 18

What does SCN5A mediate

Answer 18

depolarisation of ventricular action potentials

Question 19

What mutation affects SCN5A in long QT

Answer 19

gain of function

Question 20

What is KCNE1

Answer 20

protein - potassium channel regulator

Question 21

What is the function of KCNE1

Answer 21

makes sure KCNQ1 is working properly

Question 22

What mutation affects KCNE1 in long QT

Answer 22

loss of function

Question 23

What is CACNA1C

Answer 23

main L type calcium channel

Question 24

What is the function of CACNA1C

Answer 24

maintains plateau phase of APs

Question 25

What mutation affects CACNA1C in long QT syndrome

Answer 25

gain of function mutations

Question 26

Where do the majority of mutations occur in KCNQ1 in long QT

Answer 26

transmembrane spanning domains, pore region

Question 27

What other organ can be affected by mutations in Q1

Answer 27

ear

Question 28

Where are stria vascularis found

Answer 28

epithelial cells in the ear

Question 29

What is the function of stria vascularis

Answer 29

secrete potassium into the endolymph

Question 30

What is the affect of mutated Q1 E1 complex in the ear

Answer 30

deafness - Reissner's membrane collapses due to no endolymph

Question 31

Describe the 3 key mutations in Long QT

Answer 31

gain of function in sodium and calcium channels, loss of function in potassium channels

Question 32

What is delayed in long QT

Answer 32

start of repolarisation

Question 33

How is long QT treated

Answer 33

B blockers, Atenolol

Question 34

What is atenolol

Answer 34

B1 selective antagonist

Question 35

What is the effect of atenolol

Answer 35

reduces strength of contraction and rate of firing at SA node

Question 36

What puts you at higher risk of arthymia

Answer 36

increases heart rate

Question 37

What are the symptoms of short QT

Answer 37

reduced QT interval, arrhythmias, palpitations, fainting, death

Question 38

Describe the genes mutated in short QT

Answer 38

same as long QT but mutated in opposite ways

Question 39

What is the effect of loss of function mutations in calcium channels

Answer 39

plateau in action potential is not maintained - repolarisation occurs fastr

Question 40

What is the effect of gain of function mutations in potassium channels

Answer 40

channels overactive - drive repolarisation faster and earlier

Question 41

What mutations are associated with short QT

Answer 41

loss of function in calcium channels, gain of function in potassium channels

Question 42

What do the mutations associated with short QT cause

Answer 42

accelerated timing of repolarisation

Question 43

What is the treatment for short QT

Answer 43

implant defibrillator, quinidine