EXAM #2: CV PHARM 1 Flashcards Preview

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Flashcards in EXAM #2: CV PHARM 1 Deck (39):
1

What is the definition of excitability?

Ability of a cell to respond to an electrical stimulus

2

What is the definition of automaticity?

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

3

What is the definition of conductivity?

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

4

What is the definition of dromotropism?

Ability to alter the rate of conduction

5

What is the definition of refractoriness?

Inability of a cell to receive and transmit an action potential

E.g. during portions of the action potential

6

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

Phase 0,2, and 3

7

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

Phase 0 of the atrial

8

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

Electrical activity ALWAYS comes before mechanical

9

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

Repolarization

10

Draw and label the phases of the cardiac action potential.

N/A

11

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

- Na+

12

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

Fast= initial current for depolarization

Slow= maintained throughout action potential

13

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

1) Ca++ channels (L-type) inward
2) K+ outward

14

What maintains the plateau of phase 2?

Balance of Ca++ in an K+ out

15

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

K+ efflux

16

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

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

17

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

Funny current

18

What locations of the heart normally have phase 4 depolarization?

SA and AV node

19

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

1) Resting
- Activation gate closed
- Inactivation gate open

2) Activated
- Both gates open

3) Inactivated
- Inactivation gate closed

20

What is the effect of increased late Na+ current?

Prolonged cardiac action potential

21

When is a prolonged Late Na+ current seen?

Ischemia
Heart Failure
Arrhythmia
Peripheral arterial disease

22

Outline the pathophysiology associated with enhanced Late Na+ current.

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

23

What are the consequences cellular Ca++ overlaod?

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

24

Draw the SA node action potential.

N/A

25

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

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

26

What phases are missing from the SA node AP?

No phase 1 and 2

27

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

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

28

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

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*****

29

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

N/A

30

What are the two major categories of mechanisms of arrhythmogenesis?

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

31

List the disorders of impulse formation.

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

32

List the disorders of impulse conduction.

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

33

How is atrial tachycardia manifested on ECG?

Change in shape and rate of p-waves

34

What is an early after-depolarization?

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

35

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

Torsades De Pointes

36

What is a delayed after-depolarization?

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

37

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

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

38

What is AV Nodal Reentrant Tachycardia?

- 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.

39

What are the manifestations of re-entry?

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

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