MI and pharm

Question 1

What is the If chanel?

Answer 1

present in SA and AV nodes, pacemaker current; Na+/K+ channel

Question 2

On the pacemaker node phase 0 is marked by the influx of what ion?

Answer 2

Ca2+

Question 3

What inhibitors block the ca2+ current?

Answer 3

calcium channel inhibitors nifedipine verapamil

Question 4

What is the effect of Ach released from the vagus nerve on the SA and AV node?

Answer 4

Decrease Rate of Depolarization (If activity) Decrease max diastolic potential (incrase Ik activity) Increase threshold (decrease ICa activity) Ach decrease If in SA node, reduces steepness of phase 4. As well Ach opens GIRK channels, increasing K+ conductance making the diastolic potential more negative; main effect is to decrease I ca making threshold more positive and also making it more difficult for once cell to depolarize neighbor

Question 5

What is teh effect of norepinenphrine on SA and AV nodes?

Answer 5

increase If Increase Ca steepness increase Ca2+ influx

Question 6

What is teh effect of body temp on SA node firing?

Answer 6

increase increases rate

Question 7

What does hyperkalemia do to heart rythm?

Answer 7

fast inward current; reduce rate and amplitude of AP and slows conduction, tall T wave peaks

Question 8

What does hypokalemia do to heart beat?

Answer 8

can cause AV block, by slowing repolariation and prolongation of AP duration flatten T wave

Question 9

What do beta blokers do?

Answer 9

prevent calcium entry into cell; decrease HR, conduction velocity, strength of contration tx many cVS conditions

Question 10

What do calcium channel blockers do?

Answer 10

decrease entry of calcium and delay of depolarization of nodes

Question 11

How do you measure PR interval?

Answer 11

onset of P to onset of QRS

Question 12

How do you measure QRS interval?

Answer 12

beginning to end of qRS

Question 13

How do you measure QT interval?

Answer 13

onset QRSto end of T wave

Question 14

How do you measure QT corrected?

Answer 14

measured QT/square of RR interval

Question 15

What is the normal mean QRS axis?

Answer 15

normal -30 degrees to positive 90 degrees

Question 16

Abnormalities of the P wave are best seen in what leads?

Answer 16

II and V1; looking at atrial contraction

Question 17

What do you see on an EKG with LVH?

Answer 17

increase amplitude direted to the left, seeen in V6, increased amplitudeand can cause ST-segment depression and T wave inversion

Question 18

What do you see in RVH on an EKG?

Answer 18

Shift teh QRS vector the the right; usually seen in an increase in S, q or decrease R in leav V1,andn increase in S in lead V6

Question 19

What do you see in an EKG in RBBB?

Answer 19

V1 you see an R’ after the S peak and an inverted T wave and in v1 you see a pronounced S wave

Question 20

What do you see in an EKG of someone with LBBB?

Answer 20

notched S wave in V1, or notched R wave in V6 with inverted T wave

Question 21

What are signs of reperfusion injury?

Answer 21

necrosis with contraction bands due to influx of calcium

Question 22

What are the histological changs in MI’s between the 12 and 24 hour mark, startinga s early as 4 hours?

Answer 22

wavy fibers

Question 23

When do arrythmias occur after MI?

Answer 23

early in course of MI

Question 24

When does myocardial rupture occur after MI?

Answer 24

3-7 days after MI