Unit6: Ch 28 (Porth's 5th Ed) - Disorders of Cardiac Conduction and Rhythm Flashcards
- A physician has ordered the measurement of a cardiac patient’s electrolyte levels as part
of the client’s morning blood work. Which of the following statements best captures the
importance of potassium in the normal electrical function of the patient’s heart?
A) Potassium catalyzes the metabolism of ATP, producing the gradient that results in
electrical stimulation.
B) Potassium is central to establishing and maintaining the resting membrane
potential of cardiac muscle cells.
C) The impermeability of cardiac cell membranes to potassium allows for action
potentials achieved by the flow of sodium ions.
D) The reciprocal movement of one potassium ion for one sodium ion across the cell
membrane results in the production of an action potential.
Ans: B
Feedback:
The selective permeability of cell membranes to potassium, and its near-impermeability
to sodium ions, produces the resting membrane potential of cardiac cells. Potassium
does not catalyze the metabolism of ATP, and sodium and potassium ions do not move
across the cell membrane in a 1:1 ratio
- Which of the following statements describes phase 4 of the action potential of cells in
the sinoatrial (SA) node?
A) A slow depolarization occurs when Na+ is transported out of the cell and K+
moves back in, resulting in resting membrane potential.
B) The cells are capable of responding to a greater than normal stimulus before the
resting membrane potential is reached.
C) The fast sodium channels in the cellular membranes close, causing an abrupt
decrease in intracellular positivity.
D) Potassium permeability is allowing the cell membrane to remain depolarized, and
Ca2+ channel opens moving Ca2+ back into the cell
Ans: A
Feedback:
During phase 4 in the cells of the SA node, a slow leakage of current through the slow
channels of the cellular membrane leads to spontaneous depolarization; this slow
response enables pacemaker function. Answer B describes the relative refractory period
of the action potential curve, which occurs at the end of phase 3 in cardiac cells, and
answer C describes phase 1 of the action potential, which signals the end of
depolarization. The sodium–potassium pump transports sodium out of the cell and a
smaller amount of potassium into it, contributing to the negative intracellular charge of
the resting membrane potential in phase 4.
- An ECG technician is placing leads on a patient who has presented to the emergency
department with a sudden onset of chest pain. The technician would recognize which of
the following facts about the placement of leads and the achievement of a clinically
accurate ECG?
A) The electrical potential recorded by a lead on an extremity will vary significantly
depending on where the lead is placed on the extremity.
B) The chest leads measure electrical activity on the horizontal plane, while limb
leads measure it on the vertical plane.
C) Limb leads measure the electrical activity of the heart indirectly through the
activity of adjacent skeletal muscle.
D) A total of 12 chest leads are necessary to attain the most accurate ECG
Ans: B
Feedback:
A complete ECG is obtained by combining data from chest leads, which measure
activity on the horizontal plane, and limb leads, corresponding to the vertical or frontal
plane. The electrical potential recorded by a lead on an extremity should not vary
significantly depending on where the lead is placed on the extremity, and limb leads do
not measure electrical activity by way of skeletal muscle activity. A total of 12 leads,
only six of which are on the chest, are necessary for a complete ECG.
- The cardiologist just informed a patient that he has a reentry circuit in the electrical
conduction system in his heart. This arrhythmia is called Wolff-Parkinson-White
(WPW) syndrome. After the physician left the room, the patient asks the nurse to
explain this to him. Which of the following statements most accurately describes what is
happening?
A) “This means that the SA node (which is the beginning of your heart’s electrical
system) has been damaged and is no longer functioning normal.”
B) “You must have a large clot in one of your arteries that supply oxygenated blood
to the special conduction cells in your heart.”
C) “There is an extra, abnormal electrical pathway in the heart that leads to impulses
traveling around the heart very quickly, in a circular pattern, causing the heart to
beat too fast.”
D) “For some reason, your electrical system is not on full charge, so they will have to
put in new leads and a pacemaker to make it work better.”
Ans: C
Feedback:
There are several forms of reentry. The first is anatomic reentry. It involves an anatomic
obstacle around which the circulating current must pass and results in an excitation
wave that travels in a set pathway. Arrhythmias that arise as a result of anatomic reentry
are paroxysmal supraventricular tachycardias, as seen in WPW syndrome, atrial
fibrillation, atrial flutter, etc. Answer choice A relates to sinus node arrhythmias and
SSS. Answer choice B relates to arrhythmias caused by MI. Answer choice D relates to
third-degree block or ventricular standstill, for example
- A 68-year-old male complains to his family physician that when he tests his blood
pressure using a machine at his pharmacy, his heart rate is nearly always very low. At
other times, he feels that his heart is racing, and it also seems to pause at times. The man
has also had occasionally light-headedness and a recent syncopal episode. What is this
client’s most likely diagnosis and the phenomenon underlying it?
A) Sick sinus syndrome as a result of a disease of his sinus node and atrial or
junctional arrhythmias
B) Ventricular arrhythmia as a result of alternating vagal and sympathetic stimulation
C) Torsade de pointes as a result of disease of the bundle of His
D) Premature atrial contractions that vacillate between tachycardic and bradycardic
episodes as a consequence of an infectious process
Ans: A
Feedback:
The client’s alternating bradycardic and tachycardic episodes are indicative of sick sinus
syndrome. This pattern is not characteristic of ventricular arrhythmia, premature atrial
contractions, or torsade de pointes
- A 6-year-old boy has been brought to the emergency department by ambulance after his
mother discovered that his heart rate was “so fast I couldn’t even count it.” The child
was determined to be in atrial flutter, and his mother is seeking an explanation from the
health care team. Which of the following points should underlie an explanation to the
mother?
A) The child is experiencing a reentry rhythm in his right atrium.
B) The resolution of the problem is dependent on spontaneous recovery and is
resistant to pacing interventions.
C) The child is likely to have a normal ECG apart from the rapid heart rate.
D) The boy’s atria are experiencing abnormal sympathetic stimulation
Ans: A
Feedback:
Atrial flutter is caused by a reentry rhythm that is located in the right atrium. It is
normally responsive to pacing. His ECG will appear highly irregular, and the problem
does not originate from sympathetic stimulation.
- A nurse educator is teaching a group of nurses at a long-term care facility about atrial
fibrillation in light of its prevalence in older adults. Which of the following statements
by the nurses would the educator most want to correct?
A) “The electrical impulses go in chaotic directions, and so the atria can’t contract
properly.”
B) “An ECG of someone in atrial fibrillation would be almost random in
appearance.”
C) “The contraction of the ventricles and the atria can range from 400 to 600
beats/minute.”
D) “It can be hard to measure at the bedside because not all ventricular beats make a
palpable pulse.”
Ans: C
Feedback:
While atrial contraction can range from 400 to 600 beats/minute, ventricular contraction
is normally in the range of 80 to 180 beats/ minute during atrial fibrillation. The
electrical impulses do go in chaotic, inappropriate directions, and the ECG can appear
random. Measurement can be challenging because of the lack of pulses corresponding to
all ventricular contractions.
- A medical student is working with a 61-year-old male client in the hospital who has
presented with a new onset of atrial fibrillation. Which of the following courses of
treatment will the student most likely expect the attending physician to initiate?
A) Immediate cardioversion followed by surgery to correct the atrial defect
B) Anticoagulants and beta-blockers to control rate
C) Antihypertensives and constant cardiac monitoring in a high acuity unit
D) Diuretics, total bed rest, and cardioversion if necessary
Ans: B
Feedback:
Atrial fibrillation is most often treated with anticoagulants to prevent embolic events as
well as beta-blockers and digoxin. Cardioversion would not be a first-line intervention,
and antihypertensives and diuretics would be unlikely treatments of choice.
- A 63-year-old male client has been diagnosed with a bundle branch block. How will this
client’s care team most likely expect his condition to be expressed diagnostically?
A) His AV node will be performing the primary pacemaker role due to inadequacy of
the SA node.
B) His ECG will show a flattened P wave as a result of impaired atrial
depolarization.
C) Conduction from the Purkinje fibers to the bundle branches is compromised by
inadequate conduction.
D) His ECG will show an inordinately wide QRS complex because impulses are
bypassing the normal conduction tissue.
Ans: D
Feedback:
Because impulses must pass through muscle tissue rather than specialized conduction
tissue, the client’s QRS complex will be wide. His SA node is unlikely to be defective,
and the client’s P wave is not likely to be abnormal on an ECG. Conduction takes place
from the bundle branches to the Purkinje fibers rather than vice versa
- Which of the following patients should the nurse be assessing for long QT syndrome?
A) A 95-year-old patient with Alzheimer’s who is having periods of apnea
B) A 32-year-old male admitted for cocaine overdose with long history of illicit drug
abuse
C) A 56-year-old female admitted for total hysterectomy due to excessive bleeding
and clotting
D) A 68-year-old male who was in a car accident with sternal bruising and fractured
femur
Ans: B
Feedback:
Acquired LQTS has been linked to a variety of conditions, including cocaine use,
exposure to organophosphorous compounds, electrolyte imbalances, marked
bradycardia, MI, SAH, HIV, and protein-sparing fasting.
- A number of patients in an acute cardiac care unit of a hospital have diagnoses of
impaired cardiac conduction. Which of the following patients is most deserving of
immediate medical attention?
A) A 46-year-old man whose cardiac telemetry shows him to be in ventricular
tachycardia
B) A 69-year-old woman who has entered ventricular fibrillation
C) A 60-year-old man with premature ventricular contractions (PVC) and a history of
atrial fibrillation
D) A 60-year-old woman who has just been diagnosed with a first-degree AV block
Ans: B
Feedback:
Ventricular fibrillation, or ventricular flutter, is a life-threatening emergency that would
necessitate immediate intervention. Ventricular tachycardia is also a serious condition
but less so than ventricular fibrillation. PVCs and a first-degree AV block would not
normally require emergency intervention.
- A 71-year-old man is slated for pacemaker insertion for treatment of a third-degree AV
block. The man’s nurse has been educating him about his diagnosis and treatment and
answering the numerous questions he has about his health problem. Which of the
following teaching points should the nurse include in this patient teaching?
A) “This is almost certainly a condition that you were actually born with, but that is
just now becoming a serious problem.”
B) “Because the normal electrical communication in lacking, the bottom parts of
your heart are beating especially fast to compensate for inefficiency.”
C) “The root problem is that the top chambers of your heart and the bottom chambers
of your heart aren’t coordinating to pump blood efficiently.”
D) “If left untreated, this would have put you at great risk of stroke or heart attack.”
Ans: C
Feedback:
A third-degree AV block is characterized by independent, and thus uncoordinated,
pacemaker action for the atria and for the ventricles. It can be either congenital or
acquired, and ventricular contraction tends to be slow, not fast. Manifestations tend to
be those associated with decreased cardiac output, and a third-degree AV block is not
necessarily associated with a large increase in stroke or MI risk.
- A 72-year-old woman with a recent onset of syncopal episodes has been referred to a
cardiologist by her family physician. As part of the client’s diagnostic workup, the
cardiologist has ordered her to wear a Holter monitor for 24 hours. Which of the
following statements best captures an aspect of Holter monitoring?
A) A Holter monitor is preferable to standard ECG due to its increased sensitivity to
cardiac electrical activity.
B) The primary goal is to allow the cardiologist to accurately diagnose
cardiomyopathies.
C) Accurate interpretation of the results requires correlating the findings with activity
that the woman was doing at the time of recording.
D) Holter monitors are normally set to record electrical activity of the heart at least
once per hour
Ans: C
Feedback:
It is imperative that activity level be correlated with Holter monitor results in order to
draw accurate diagnostic conclusions. It is the long-term gathering of data, rather than
sensitivity or accuracy that gives Holter monitoring an advantage over standard ECG
measurement. The goal is to diagnose arrhythmias, not cardiomyopathies. The hallmark
of Holter monitoring is its continuous, rather than intermittent, measurement.
- A 31-year-old woman with a congenital heart defect reports episodes of
light-headedness and syncope, with occasional palpitations. A resting electrocardiogram
reveals sinus bradycardia, and she is suspected to have sick sinus syndrome. Which of
the following diagnostic methods is the best choice to investigate the suspicion?
A) Signal-averaged ECG
B) Exercise stress testing
C) Electrophysiologic study
D) Holter monitoring
Ans: D
Feedback:
Because sick sinus syndrome frequently involves intermittent or alternating types of
arrhythmias, Holter monitoring, which can record changes in rhythm that occur over a
period of up to 48 hours, is likely to provide the best picture of the spectrum of cardiac
changes in any particular client. Signal-averaged ECG is most useful for identifying
specific arrhythmias that may not be clear on traditional surface ECG. Exercise stress
testing measures changes in rhythm specifically in response to exercise.
Electrophysiologic studies are used diagnostically to determine a person’s potential for
arrhythmia formation.
- Following electrophysiological testing that included ablation therapy, the nurse should
be assessing the patient for which complication that may occur postprocedure?
A) Complaints of nausea and spitting up bile-looking secretions along with stomach
cramps
B) Sudden onset of dysonea, tachypnea, and chest pain of a “pleuritic” nature
(worsened by breathing)
C) Bleeding from the nose that requires packing, excessive swallowing of mucus,
and coughing
D) Complaints of heart palpitations, frequent PVCs noted on monitor, and substernal
chest pain
Ans: B
Feedback:
Following EPS that included an ablation, the procedure increases the risk of
complications, which include venous thrombosis and pulmonary emboli. Answer choice
B refers to s/s of pulmonary emboli. Answer choice A refers to GI symptoms, which
are not associated with EPS. Answer choice C refers that this procedure does not place a
tube down the nose/throat. Answer choice D refers that EPS usually does not involve
the left side of the heart; therefore, the risk of MI is minimal
