Antiarrhythmics (review)

Question 1

On an ECG, what is the P wave, QRS and the T wave generated by?

Answer 1

P wave- atrial depolarization

QRS- ventricular muscle depolarization

T wave- ventricular repolarization

Question 2

On an ECG, the PR interval is a measure of what?

Answer 2

a measure of conduction time from atrium to ventricle

Question 3

On an ECG, what does the QT interval reflect?

Answer 3

the duration of the ventricular action potential

Question 4

What are the differnet pumps/channels utilized during an action potention and ion movement

Answer 4

1. Resting potential- Na/K pump
2. Depolarization- voltage gated Na channel
3. Repolarization- Voltage gated K channel
4. Resting potential- Na/K pump

Question 5

In the following picture, which graph shows Ventricular muscle cell action potential vs. SA node cell action potential?

Answer 5

Top: SA node cell

Bottom: ventricular muscle cell

Question 6

What is the ion movement in purkinje fiber action potential at phase 4, 0, 1, 2 and 3?

Answer 6

Phase 4- Na in, K out

Phase 0- Na in and Ca in

Phase 1- Ca in, K out

Phase 2- Ca in, K out

Phase 3- K out

Question 7

In non-pacemaker cells, the outward _______ current during phase 4 is sufficient to maintain a stable negative resting potential

Answer 7

Potassium

Question 8

In pacemaker cells, the _____ current is smaller than in non-pacemaker cells and the depolarizing currents (sodium, calcium, or both) during phase 4 are lrg enough to gradually depolarize the cell during diastole

Answer 8

Potassium

Question 9

Mechanisms of tachyarrhythmias:

What are the two general categories?

Answer 9

1. Abnormality in impulse generation or “automatic” tachycardias
2. Abnormality in impulse conduction or “reentrant” tachycardias

Question 10

What is another name for a tachyarrhythmia whose mechanism is an abnormality in impulse generation?

An abnormality in impulse conduction?

Answer 10

impulse generation= “Automatic” tachycardias

impulse conduction= “reentrant” tachycardia

Question 11

Most antiarrhythmic drugs (AADs) do what?

Answer 11

modulate the activity of ion channels in the plasma membranes

Question 12

Pacemaker cells exhibit automaticity:

SA node= ___-___bpm

AV node and Bundle of His= __-__bpm

Bundle branches, purkinje fibers= ____-____bpm

Answer 12

SA node= 60-100bpm

AV node and Bundle of His= 50-60 bpm

Bundle branches, purkinje fibers= 30-40 bpm

Question 13

nonpacemaker cells in pathologic conditions can acquire ______

Answer 13

automaticity