Download Chapter04_Detailed_Answers

Chapter 4
Detailed Answers to Assess Your Understanding
1.
d:
If the QRS complexes are close together the heart rate is fast.
2.
True: Determining the heart rate helps you identify abnormal ECG rhythms. For this reason it
is an important step in assessing the ECG. Begin by quickly checking the ECG monitor or tracing
to see if the rate is slow, normal, or fast. Extremely slow or fast heart rates are a cause for
concern.
3.
c:
A benefit of using a shortcut method for determining the heart rate is that it is faster than
counting the complexes found on a whole minute’s worth of ECG tracing.
4.
a:
The 6-second interval x 10 method can be used to estimate the heart rate in irregular
rhythms. While this method is faster to perform, it is not as accurate as other methods such as
the 300, 150, 100, 75, 60, 50 Method or the 1,500 method.
5.
d:
The 300, 150, 100, 75, 60, 50 method requires you to identify a start point from which
to identify where the next R wave falls. For the starting point, locate an R wave that falls on or
close to a bold line to make counting easier.
6.
a:
To use the 1500 method, count the number of small squares between two consecutive
R waves and divide 1500 by that number.
7.
c:
The 1500 method is the most accurate for determining the heart rate in a regular
rhythm. While the other methods for calculating the heart rate are not as accurate, they are
easier and faster to use.
8.
False: The atrial heart rate is not always the same as the ventricular heart rate. For this reason
both must be measured.
9.
d:
10.
d:
Tachycardia may be brought about by exercise or exertion. It is a dysrhythmia that has a
heart rate greater than 100 beats per minute. It can be produced by stimulation of the sympathetic
nervous system and it can lead to increased myocardial oxygen consumption.
11.
d:
It is unlikely that the patient’s heart rate was actually 320 because she was awake, her
blood pressure was not low and she was able to answer questions. Because cardiac output is
seriously diminished with rates higher than 250, if the patient did in fact have a pulse of 320 she
The average heart rate in the adult patient is between 60 and 100 beats per minute.
would most likely have signs of shock such as an altered level of responsiveness and
hypotension.
12.
a:
The most likely cause of the patient’s fast heart rate was anxiety. Hyperthyroidism
is a condition of excess thyroxin in the blood from an overactive thyroid gland. Thyroxin acts like
a sympathomimetic agent resulting in an elevated heart rate. While anxiety can produce
tachycardia it rarely does so to a level of 160 beats per minute. There is no evidence that the
patient is either hypoxic of abusing amphetamine.