12 Lead ECG in Acute Coronary Syndromes 3rd Edition Phalen Test Bank
Chapter 01: Reviewing the Basics
TRUE/FALSE
- Approximately one third of the heart lies to the left of the midline of the sternum. The
remaining two thirds lie to the right of the sternum.
ANS: F
Approximately two thirds of the heart lie to the left of the midline of the sternum. The remaining third lies to the right of the sternum.
OBJ: Describe the location of the heart.
- Depolarization is the same as contraction.
ANS: F
Depolarization is not the same as contraction. Depolarization (an electrical event) is expected to result in contraction (a mechanical event). It is possible to see organized electrical activity on the cardiac monitor, yet evaluation of the patient reveals no palpable pulse. This clinical situation is called pulseless electrical activity (PEA).
OBJ: N/A
- The base, or lower portion, of the heart is formed by the tip of the left ventricle.
ANS: F
The base of the heart is its uppe N r U p R or S ti I on N a G n T d B is .f C or O m M ed mainly by the left atrium, with a small amount of right atrium. It lies at approximately the level of the second intercostal space, immediately in front of the esophagus and descending aorta. The heart’s apex, or lower portion, is formed by the tip of the left ventricle. The apex lies just above the diaphragm at approximately the level of the fifth intercostal space in the midclavicular line.
OBJ: Describe the location of the heart.
- The period of time during the cardiac cycle when cells cannot respond to a stimulus, no matter
how strong, is called the relative refractory period.
ANS: F
During the absolute refractory period (also known as the effective refractory period), the cell will not respond to further stimulation. This means that the myocardial working cells cannot contract and the cells of the electrical conduction system cannot conduct an electrical impulse—no matter how strong the stimulus.
OBJ: N/A
- Blood pressure is the result of cardiac output and peripheral vascular resistance.
ANS: T 1 / 4
Blood pressure is equal to cardiac output peripheral vascular resistance. Blood pressure is the force exerted by the circulating blood volume on the walls of the arteries. Peripheral vascular resistance is the resistance to the flow of blood determined by blood vessel diameter and the tone of the vascular musculature.
OBJ: Identify and define the components of cardiac output.
MULTIPLE CHOICE
- The heart is divided into chambers but functions as a -sided pump.
- 2; 4
- 3; 2
- 4; 2
- 4; 3
ANS: C
The heart has four chambers — two atria and two ventricles. The right and left sides of the heart are separated by an internal wall of connective tissue called a septum. The interatrial septum separates the right and left atria. The interventricular septum separates the right and left ventricles. The septa separate the heart into two functional pumps. The right atrium and right ventricle make up one pump. The left atrium and left ventricle make up the other.
OBJ: Identify and describe the chambers of the heart and the vessels that enter or leave each.
- In the heart's conduction system, the receive(s) an electrical impulse from the right and
- atrial pacemaker cells
- Purkinje fibers
- atrioventricular (AV) node
- sinoatrial (SA) node
left bundle branches and relay(s) it to the ventricular myocardium.
ANS: B
The right and left bundle branches divide into smaller and smaller branches and then into a special network of fibers called the Purkinje fibers. These fibers spread from the interventricular septum into the papillary muscles. They continue downward to the apex of the heart, making up an elaborate web that penetrates about one third of the way into the ventricular muscle mass. The fibers then become continuous with the muscle cells of the right and left ventricles.
OBJ: Describe the normal sequence of electrical conduction through the heart.
- Blood flows from the left atrium through the valve into the left ventricle.
- mitral
- aortic
- pulmonic
- tricuspid
ANS: A
Blood flows from the left atrium through the mitral (bicuspid) valve into the left ventricle.
OBJ: Beginning with the right atrium, describe blood flow through the normal heart and lungs to the 2 / 4
systemic circulation.
4. The anterior surface of the heart consists primarily of the:
- left atrium.
- right atrium.
- left ventricle.
- right ventricle.
ANS: D
The front (anterior) surface of the heart lies behind the sternum and costal cartilages. It is formed by portions of the right atrium and the left and right ventricles. However, because the heart is tilted slightly toward the left in the chest, the right ventricle is the area of the heart that lies most directly behind the sternum.
OBJ: N/A
5. The intrinsic rate of the atrioventricular (AV) junction is:
- 20 to 40 beats/min.
- 40 to 60 beats/min.
- 60 to 80 beats/min.
- 80 to 100 beats/min.
ANS: B
The AV junction has pacemaker cells capable of firing at a rate of 40 to 60 beats/min.
OBJ: State the intrinsic rates of the SA node, AV junction, and Purkinje fibers.
6. The base of the heart is found aNt UapRpSroIxNimGaTteBly.tCheOlMevel of the:
- first rib.
- second rib.
- fourth rib.
- fifth and sixth ribs.
ANS: B
The base of the heart is its upper portion and is formed mainly by the left atrium, with a small amount of right atrium. It lies at approximately the level of the second rib, immediately in front of the esophagus and descending aorta.
OBJ: Describe the location of the heart.
- Thin strands of fibrous connective tissue extend from the AV valves to the papillary muscles
and prevent the AV valves from bulging back into the atria during ventricular systole. These
strands are called:
- cardiac cilia.
- Purkinje fibers.
- papillary muscles.
- chordae tendineae.
ANS: D 3 / 4
Chordae tendineae are thin strands of connective tissue. On one end, they are attached to the underside of the AV valves. On the other end, they are attached to small mounds of myocardium called papillary muscles. Papillary muscles project inward from the lower portion of the ventricular walls. When the ventricles contract and relax, so do the papillary muscles. The papillary muscles adjust their tension on the chordae tendineae, preventing them from bulging too far into the atria.
OBJ: N/A
8. The myocardium is thickest in the:
- right atrium.
- right ventricle.
- left atrium.
- left ventricle.
ANS: D
The thickness of the myocardium varies from one heart chamber to another. This variation in thickness is related to the amount of resistance that must be overcome to pump blood out of the different chambers. For example, the atria encounter little resistance when pumping blood to the ventricles. As a result, the atria have a thin myocardial layer. On the other hand, the ventricles must pump blood to either the lungs (the right ventricle) or the rest of the body (the left ventricle). So, the ventricles have a much thicker myocardial layer than the atria. The wall of the left ventricle is three times thicker than that of the right because the left ventricle propels blood to most vessels of the body. The right ventricle moves blood only through the blood vessels of the lungs and then into the left atrium.
OBJ: Identify and describe the c
N ha U m R b S er I s o N f G th T e B he .a C rt O an M d the vessels that enter or leave each.
- An internal wall of connective tissue called the separates the right and left ventricles.
- septae
- interventricular septum
- coronary sinus
- mediastinum
ANS: B
The right and left sides of the heart are separated by an internal wall of connective tissue called a septum. The interatrial septum separates the right and left atria. The interventricular septum separates the right and left ventricles. The septa separate the heart into two functional pumps. The right atrium and right ventricle make up one pump. The left atrium and left ventricle make up the other.
OBJ: Identify and describe the chambers of the heart and the vessels that enter or leave each.
10. The left atrium receives blood from the:
- pulmonary veins.
- aorta.
- pulmonary arteries.
- inferior vena cava.
ANS: A
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