Chapter 13 : Premature Atrial Contraction

Question 1

What is a PAC?

Answer 1

An impulse or complex that occurs earlier than expected and originates in an atrial focus, not in the SA node.

Question 2

PAC’s are normally clinically…

Answer 2

Insignificant

Question 3

Frequent PAC’s, valvular disorders, and heart failure will do what to the ventricles?

Answer 3

Inappropriate filling of the ventricles caused by early complexes can cause alterations in cardiac output

Question 4

The normal pacemaking function of the atrial tissue is set at what rate?

Answer 4

55 - 60 BPM

Question 5

The impulse of the PAC moves in a…..direction and route than that taken by sinus impulse.

Answer 5

Different

Question 6

After the PAC, the….should once again take over its primary role as the main pace maker.

Answer 6

SA node

Question 7

The ventricular portion of the impulse proceeds….along the electrical conduction system of the heart once it reaches the….

Answer 7

Normally, AV node

Question 8

Each….in the ventricles forms its own small electrical vector.

Answer 8

Myocyte

Question 9

The…..of the heart is the main vector that remains when all of those individual small vectors are added together.

Answer 9

Electrical Axis

Question 10

Electrodes see vectors traveling towards it as a….

Answer 10

Positive Wave

Question 11

Electrodes see vectors traveling away from it as a…..

Answer 11

Negative Wave

Question 12

The P-wave axis is…

Answer 12

The sum of all the individual vectors the atrial myocytes form

Question 13

Note*

Answer 13

If the P wave is not upright in leads I, II, aVF, v1, and v5-6, and negative in avR, then the P wave has to have originated in some ectopic focus

Question 14

If the pacemaker site is close to the AV node, the time it takes for the depolarization wave to reach the AV node is….

Answer 14

Shorter

Question 15

If the pacemaker site is farther from the AV node, the time it takes for the depolarization wave to reach the AV node is….

Answer 15

Longer

Question 16

If the SA node were depolarized and reset, the time frame during which a PAC and the pause occurred would not be an exact multiple of the P-P interval. That type of pause is known as….

Answer 16

Noncompensatory pause

Question 17

If the SA node was not reset, the pause would be an exact multiple of the regular P-P interval, and then you know the SA node was not reset. That type of pause is known as…

Answer 17

Compensatory pause

Question 18

Compensatory pauses usually occur with PJCs or PVCs, not with….

Answer 18

PACs

Question 19

The most common pattern of aberrancy is a….

Answer 19

RBBB pattern

Question 20

RBB has the longest refractory period. Once an impulse hits an area of refractoriness, it needs to continue its march through the ventricles using a slow…..means of conduction.

Answer 20

Cell-to-Cell

Question 21

Once in awhile the P wave of a PAC will fall right over the….of the previous complex

Answer 21

T wave