Real-Life Communication
You are a cardiovascular technician monitoring a patient's
heart. You are about to perform an electrocardiogram (ECG).
The patient
has spoken to the doctor about her condition and about the test, but she still
wants to know more.
"Cardiovascular technicians have to be familiar
with all the terminology that is related to medicine and cardiology," says
Chandra Varey of the Cardio Echo Lab. "They have to be able to read evaluations
and reports. They must immediately understand the terminology that is used."
Read
the following and answer the patient's questions:
The
electroconduction system of the heart is complicated. It begins in the right
atrium at the sinoatrial (SA) node. The SA node is a small bundle of cells
on the back wall of the right atrium. (The right and left atria are the upper
chambers of the heart). It serves as a pacemaker for the heart.
The
SA node fires an electrical impulse across the right atrium to the left atrium
so that both can contract at the same time. This forces blood from the atria
through the valves to the ventricles. (The ventricles are the two lower chambers
of the heart.)
The impulse then travels to the atrioventricular (AV)
node. The AV node makes sure all the blood from the atria is emptied into
the ventricles before the ventricles contract.
The impulse then travels
from the AV node to the Purkinje fibers. The Purkinje fibers are arranged
in two bundles. One bundle branches to the muscle in the right ventricle.
The other branches to the muscle in the left ventricle.
The impulse
moves through these fibers very rapidly. It spreads throughout the ventricles
at two to four meters per second. This causes the ventricles to pump fast
and hard.
This forces the blood out to the body at an extremely fast
rate. The impulse flowing through the body creates a mass electrical signal
that can be detected by placing electrodes on a patient's chest. This
electrical signal can be plotted by a machine. The plot is called an electrocardiogram
(ECG).
(Excerpted from http://www.bae.ncsu.edu,
bioengineering dept. Authors are: Robert Schoderbek, Heidi Lane, Mike Deaton
and Joanne Deverson)
Questions
- What is the SA node and what does it do?
- What causes the ventricles to pump blood through the body?
- What is an electrocardiogram?