Phys ECG

Question 1

Why is there a slow rate of rise in the SA node AP?

Answer 1

No Na channels

Question 2

The basis for pacemaker function is ___

Answer 2

Funny channels cause sow, spontaneous DD

Question 3

During the relative refractory period ___ are closed and ___ are open

Answer 3

All m gates are closed

Some h gates are open

Question 4

___ is the neurotransmitter responsible for a negative chronotropic effect

___ is the neurotransmitter responsible for a positive inotropic effect.

Answer 4

ACh

NE

Question 5

3 conditions for reentry

Answer 5

1. Closed loop
2. Unidirectional block
3. Transit time > refractory period

Question 6

The enzyme associated with overdrive suppression is ___

Answer 6

Na-K ATPase

Question 7

Spontaneous DD in the SA node is due to:

Answer 7

1. Funny channels

2. Na entry through Na-Ca antiporter

Question 8

The mechanism for overdrive suppression is ___

Answer 8

Hyperpolarization due to increased Na efflux

Question 9

Refractory period plasticity is related to changes in ___

Answer 9

Phosphorylation of K channels and increased K efflux

Question 10

Decremental conduction refers to ___

Answer 10

Tendency for AP amplitude and conduction velocity to decrease

Question 11

Circus movements progress to fibrillation when ___

Answer 11

Impulses divide and propagate

Question 12

After a heart transplant what happens to heart rate?

Answer 12

It increases slowly because autonomic regulation is missing due to cut nerves during a heart transplant

*epinephrine and NE from the adrenal gland allows it to still increase

Question 13

Conduction velocity of a Purkinje fiber

Answer 13

2-4 m/sec

Question 14

P wave represents ___

Answer 14

Atrial depolarization

Question 15

T wave represents

Answer 15

Ventricular repolarization

Question 16

U wave represents

Answer 16

Purkinje fiber repolarization

*usually only seen in extremely low HRs

Question 17

There is no dipole in which segments on an ECG?

Answer 17

ST and TP (flat lines)

Question 18

Frontal plane leads

Answer 18

Standard limb leads (I, II, III)
*bipolar
Augmented limb leads (aVF, aVL, aVR)
*unipolar

Question 19

Horizontal plane leads

Answer 19

Precotdial or chest leads (V1-6)

*unipolar

Question 20

Frontal plane leads placement

Answer 20

I: + left arm, - right arm
II: + left leg, - right arm
III: + left leg, - left arm

Question 21

Augmented limb leads placement

Answer 21

• aVF: + left leg (w/points on each arm)
• aVL: + left arm (points on left leg and right arm)
• aVR: + right arm (points on left leg and left arm)

Question 22

Einthovens rule

Answer 22

The magnitude of lead II typically equals I + III at the QRS complexity

Question 23

Precotdial chest leads placement

Answer 23

V1: 4th intercostal space right of sternum
V2: 4th intercostal space left of sternum
V4: 5th intercostal space, left mid-clavicular line
V3: between V2 and V4
V6: left midaxillary line, level with V4
V5: level with V4, left of anterior axillary line

Question 24

Leads with negative deflections

Answer 24

V1

aVR

Question 25

The T wave in the ventricles is ___ because ____.

The t wave in the atria is ___ because ___

Answer 25

Positive, it repolarizes in the opposite direction

Negative, same direction