Chapter 4: Rate

Question 1

Sinus bradycardia most often results from…

Answer 1

…parasympathetic excess, as seen in conditioned athletes at rest.
(p. 67)

Question 2

There are focal areas of ____________ in the heart known as _____________ ____, or _______ ____.
They are _________ pacemakers that are capable of pacing in _________ __________.
Under normal circumstances, these foci are ____________ ______.

Answer 2

automaticity, automaticity foci, ectopic foci
potential, emergency situations
electrically silent
(p. 68)

Question 3

The ectopic or automaticity foci are located in the…

Answer 3

…atria, ventricles, and AV junction.

p. 69

Question 4

The ectopic foci in the atrium are located in the…

Answer 4

…atrial conduction system and are known as “atrial automaticity foci”.
(p. 69)

Question 5

The AV node has foci in the…

Answer 5

…middle and distal regions of the AV node, known as “junctional automaticity foci”
(p. 69)

Question 6

The ventricles have automaticity foci in the…

Answer 6

…His bundle and bundle branches; these are known as ventricular automaticity foci.
(p. 69)

Question 7

The automaticity foci of each level (i.e. the atria, AV Junction, and the ventricles) have a general range of rate at which they pace. The atria pace at…
The AV junction paces at…
The ventricles pace at…

Answer 7

…60 - 80 beats/min.
…40 - 60 beats/min.
…20 - 40 beats/min.
(p. 70)

Question 8

Specifically, each individual automaticity focus has its own…

Answer 8

…precise inherent rate at which it paces.

p. 70

Question 9

Rapid automaticity suppresses slower automaticity. This concept is known as…

Answer 9

…overdrive suppression

p. 71

Question 10

Once an automaticity focus actively begins pacing, it will overdrive-________ all lower (______) foci, including slower foci at ___ ____ _____, eliminating any ___________.

Answer 10

suppress, slower, the same level, competition

p. 71

Question 11

Without SA Node pacing, an atrial automaticity focus can emerge as an ______ ______ _________, and it becomes the ________ _________ by overdrive-suppressing all lower levels of foci, since they have slower ________ rates.

Answer 11

active backup pacemaker
dominant pacemaker
inherent
(p. 73)

Question 12

A junctional focus actively pacing at its inherent rate of (40 - 60 beats/min) produces an ______________ rhythm.

Answer 12

idiojunctional

p. 74

Question 13

What is the AV junction?

Answer 13

The portion of the AV node that has foci of automaticity.

p. 74

Question 14

The prefix “idio” is of _____ origin and means “_____ ___”.

Answer 14

Greek
one’s own
(p. 74)

Question 15

All ventricular automaticity foci are composed of…

Answer 15

…Purkinje fibers

p. 76

Question 16

Without overdrive suppression from above, a ventricular automaticity focus emerges to actively pace at its inherent rate range of __ to __ per min.
This is known as an _______________ rhythm.

Answer 16

20 - 40
idioventricular
(p. 76)

Question 17

Idioventricular rhythms can appear for two reasons:
if all __________ _______ above it have failed,
OR,
if there is a ________ _____ of conduction below the __ ____, that prevents any pacing stimulus above it.

Answer 17

pacemaking centers
complete block, AV Node
(p. 76)

Question 18

In a physiological or pathological emergency, an irritable automaticity focus may suddenly discharge at a rapid rate. This emergency rate (___ to ___ per minute) is approximately the same for foci of ___ ______.

Answer 18

150 - 250
all levels
(p. 77)

Question 19

To rapidly calculate the heart rate, memorize the following numbers:
Locate an R wave, and assign the above numbers to the heavy black lines that follow.

Answer 19

300, 150, 100, 75, 60, 50

p. 81

Question 20

How much time is represented by the distance between two heavy black lines?
What fraction of a minute is this?

Answer 20

0.2 sec, or 200 msec

1/300th of a minute
p. 88

Question 21

The small marks at the top of every EKG strip mark the…

Answer 21

…three second intervals.

p. 91

Question 22

To calculate the rate for a patient in bradycardia…

Answer 22

…look at a 6 second strip, count the number of R to R cycles (not total R waves), and multiply by 10.
(p. 94)