Cardiovascular pharmacology I

Question 1

which ion is responsible for phase 0 of the cardiac action potential - ventricular muscle?

Answer 1

sodium influx

Question 2

calcium is important for which phase of the cardiac action potential - ventricular muscle?

Answer 2

phase 2

Question 3

why is the phase 2 downslope of the cardiac action potential gradual (ventricular muscle)?

Answer 3

balance between influx of calcium and efflux potassium

Question 4

what ion is responsible for the sharp downward slope of phase 3 of the cardiac action potential - ventricular muscle?

Answer 4

potassium efflux

Question 5

how will drugs that block potassium channels change phase 3 of the cardiac action potential?

Answer 5

prolong

Question 6

what is the funny current?

Answer 6

phase 4 of pacemaker tissue - upslope

Question 7

what is the conformation of the sodium channel at rest? upon depolarization? inactivation state?

Answer 7

1. activation gate closed, inactivation gate open
2. activation gate open, inactivation gate open
3. activation gate open, inactivation gate closed

Question 8

what is the result of enhanced late sodium current?

Answer 8

1. increased intracellular sodium
2. sodium exit with calcium entry (NCX)
3. increased intracellular calcium - cellular calcium overload
4. electrical instability, after-depolarizations, arrhythmias
5. mechanical dysfunction, abnormal contraction and relaxation

Question 9

which ion is responsible for phase 0 of the cardiac action potential - SA node?

Answer 9

calcium influx

Question 10

how long does the ERP last in ventricular muscle?

Answer 10

phase 0 - mid-phase 3

Question 11

what does a low ERP/APD ratio mean?

Answer 11

easy to be depolarize by abnormal impulses

Question 12

how does SA node tachycardia manifest on the ECG?

Answer 12

every QRS is preceded by a P wave, but they occur much faster than normal

Question 13

how does atrial tachycardia manifest on the ECG?

Answer 13

some P waves without QRS complexes - 2:1 conduction rate (atria: ventricles)

Question 14

how do early after-depolarization occur?

Answer 14

1. prolonged cardiac AP (slow HR, hypokalemia, drugs)

2. can lead to Torsades de Pointes

Question 15

how do delayed after-depolarizations occur?

Answer 15

1. cytoplasmic or SR calcium overload (ischemia, stress, digitalis overdose, heart failure)
2. normal upstroke followed by abnormal depolarization
3. secondary upstroke
4. abnormal rhythm - spontaneous APs

Question 16

what is the hallmark ECG sign for first degree AV block?

Answer 16

increased PR interval

Question 17

what is the ECG sign for second degree AV block?

Answer 17

not all P waves pass

Question 18

what is the ECG sign for third degree AV block?

Answer 18

1. large QRS complex - ventricular conduction origin

2. no P/QRS relationship (ventricles beat according to their own rhythm)

Question 19

what is the reason for existence of a reentry mechanism?

Answer 19

two pathways, each with different conduction velocities

Question 20

what is the mechanism of atrial premature beat / reentry mechanism?

Answer 20

1. fast pathway encountered during refractory period of normal SA beat
2. premature beat goes through slow pathway
3. once fast pathway repolarizes, loop forms (slow pathway returns back up the fast pathway)

Question 21

what is a hallmark sign of accessory pathway mediated supraventicular tachycardia?

Answer 21

P waves occur after QRS

Question 22

what are the consequences of arrhythmia?

Answer 22

1. decreased efficiency - decreased SV and CO
2. proarrhythmic / arrhythmogenic - conversion of vtac to vfib
3. thrombogenesis