EXAM #2: CV PHARM 1

Question 1

What is the definition of excitability?

Answer 1

Ability of a cell to respond to an electrical stimulus

Question 2

What is the definition of automaticity?

Answer 2

Ability for a cell or group of cells to initiate an action potential

Question 3

What is the definition of conductivity?

Answer 3

Ability of a cell or region of cells to receive and transmit an action potential

Question 4

What is the definition of dromotropism?

Answer 4

Ability to alter the rate of conduction

Question 5

What is the definition of refractoriness?

Answer 5

Inability of a cell to receive and transmit an action potential

E.g. during portions of the action potential

Question 6

What phases of the cardiac action potential does the QRS complex correspond with?

Answer 6

Phase 0,2, and 3

Question 7

What phases of the cardiac action potential does the p-wave correspond with?

Answer 7

Phase 0 of the atrial

Question 8

What is the rule regarding electrical and mechanical activity of the heart?

Answer 8

Electrical activity ALWAYS comes before mechanical

Question 9

What phase of the cardiac action potential does the T-wave correspond with?

Answer 9

Repolarization

Question 10

Draw and label the phases of the cardiac action potential.

Answer 10

N/A

Question 11

What ion channel mediates phase 0 if the cardiac action potential?

Answer 11

• Na+

Question 12

What is the difference between fast and slow Na+ current?

Answer 12

Fast= initial current for depolarization

Slow= maintained throughout action potential

Question 13

What ion channels mediate phase 2 of the cardiac action potential?

Answer 13

1) Ca++ channels (L-type) inward

2) K+ outward

Question 14

What maintains the plateau of phase 2?

Answer 14

Balance of Ca++ in an K+ out

Question 15

What ion channels mediate phase 3 of the cardiac action potential?

Answer 15

K+ efflux

Question 16

What happens to the cardiac action potential with K+ channel blockers?

Answer 16

AP is prolonged b/c of less efflux for phase 3

Question 17

What ion channel is responsible for phase 4 of the cardiac action potential?

Answer 17

Funny current

Question 18

What locations of the heart normally have phase 4 depolarization?

Answer 18

SA and AV node

Question 19

What are the three phases of the cardiac Na+ channel?

Answer 19

1) Resting
- Activation gate closed
- Inactivation gate open

2) Activated
- Both gates open

3) Inactivated
- Inactivation gate closed

Question 20

What is the effect of increased late Na+ current?

Answer 20

Prolonged cardiac action potential

Question 21

When is a prolonged Late Na+ current seen?

Answer 21

Ischemia
Heart Failure
Arrhythmia
Peripheral arterial disease

Question 22

Outline the pathophysiology associated with enhanced Late Na+ current.

Answer 22

1) Increased Na+ influx leads to elevated intracellular Na+
2) Elevated intracellular Na+ activates the Na+-Ca++ exchanged
- Exchange of Na+ (out)
- Ca++ into the cell
3) This causes increased intracellular Ca++
4) Ca++ overload develops

Question 23

What are the consequences cellular Ca++ overlaod?

Answer 23

1) Electrical instability–>after-depolarizations/ arrhythmia
2) Mechanical dysfunction–>abnormal contraction and relaxation

Question 24

Draw the SA node action potential.

Answer 24

N/A

Question 25

What causes phase 0 in the SA node AP? How does this compare to the ventricular tissue?

Answer 25

- Ca++ current in SA node | - Na+ in ventricular myoctye

Question 26

What phases are missing from the SA node AP?

Answer 26

No phase 1 and 2

Question 27

What do Na+ channel blockers effect more, nodal or ventricular tissue? Why?

Answer 27

Ventricular/ myocyte b/c these tissues have a fast inward Na+ current that causes depolarization

Question 28

What is the ERP/ADP ratio? Why is this important?

Answer 28

This is the ratio of the "effective refractory period" to the "Total action potential duration" ****The LOWER the ratio, the EASIER it is for depolarization by aberrant impulses i.e. the longer the APD is with a shorter ERP-->arrhythmia*****

Question 29

Draw the cardiac action potential and the effective/ relative refractory periods.

Answer 29

N/A

Question 30

What are the two major categories of mechanisms of arrhythmogenesis?

Answer 30

1) Disorders of impulse formation | 2) Disorder of impulse conduction

Question 31

List the disorders of impulse formation.

Answer 31

- No change in pacemaker site e.g. sinus tachy or bradycarida - Ectopic foci - Early and delayed after-depolarizations

Question 32

List the disorders of impulse conduction.

Answer 32

- AV Block - Ventricular re-entry - AV re-entry

Question 33

How is atrial tachycardia manifested on ECG?

Answer 33

Change in shape and rate of p-waves

Question 34

What is an early after-depolarization?

Answer 34

Depolarization in the relative refractory period, during a prolonged plateau phase

Question 35

What is a common consequence of an early-after depolarization?

Answer 35

Torsades De Pointes

Question 36

What is a delayed after-depolarization?

Answer 36

- Occurs in high intracellular Ca++ concentrations - Normal upstroke followed by abnormal depolarization that leads to a secondary uptroke - Abnormal rhythm results

Question 37

What is the difference between a 1st, 2nd, and 3rd degree AV block?

Answer 37

``` 1st= prolonged PR interval 2nd= not all p-waves followed by QRS 3rd= no P/QRS relationship i.e. AV dissociation ```

Question 38

What is AV Nodal Reentrant Tachycardia?

Answer 38

- Patient has 2x conduction paths/velocities in the AV node***** - Ectopic ATRIAL PREMATURE BEAT finds fast pathway in refractory period (via normal SA nodal pathway) - Slow pathway depolarized and enters fast pathway b/c it is fast enough to repolarized enough for stimulation - Circular motion begins Note that this does not have to occur just in the AV node.

Question 39

What are the manifestations of re-entry?

Answer 39

- A-flutter - AVNRT - Accessory SVT - Ventricular re-entry