CCRN Practice Questions -
Cardiovascular
A patient develops atrial fibrillation after abdominal surgery. Her blood pressure falls from 110/70 mm
Hg to 92/68 mm Hg. The hypotension is related to which of the following?
a. Decrease in ventricular contractility
b. Hypovolemia
c. Mural thrombi
d. Decrease in ventricular filling - Correct answer: d
Rationale: The contribution that atrial contraction makes to ventricular filling volume is approximately
15% to 30%. Atrial fibrillation results in quivering but not contracting atria. The loss of 15% to 30% of
diastolic filling volume reduces cardiac output and can have significant hemodynamic consequences.
Although mural thrombi also are a problem, they
result in an embolic phenomenon rather than a direct decrease in cardiac output. The relationship
between the development of atrial fibrillation and the decrease in cardiac output make hypovolemia and
decrease in contractility less likely.
Test-Taking Strategy: Relate recent changes in patient status to recent occurrences. The patient had a
change in atrial function, so select an option that results in loss of atrial contraction or "kick." Choose
option d.
Oxygen delivery (DO2) is the product of which of the following?
a. PaO2, hemoglobin, mean arterial pressure
b. SaO2, hemoglobin, cardiac output
c. SvO2, cardiac index, SaO2
d. PaO2, mean arterial pressure, SvO2 - Correct answer: b
Rationale: Ninety-seven percent of oxygen is attached to the hemoglobin molecule, so the SaO2 (arterial
oxygen saturation) is a more accurate reflection of the amount of oxygen in blood. The PaO2 represents
only the 3% that is dissolved in the plasma. The lungs must put the oxygen in the blood, the hemoglobin
must carry the oxygen, and the cardiac output is a reflection of how well the heart is moving the blood
with its hemoglobin with attached
oxygen. SvO2 (venous oxygen saturation) is a reflection of the oxygen reserve. SvO2 is what is left over
after the tissues have extracted what they need. The mean arterial pressure is a reflection of organ tissue
perfusion pressure but does not indicate anything about the amount of oxygen in that blood.
,Test-Taking Strategy: Oxygen is delivered from the arterial end, so choose an option that has SaO2
instead of SvO2. Also remember that most oxygen is carried on hemoglobin. Look for SaO2 (not PaO2)
and hemoglobin. The only option with both of these is option b.
A patient is in cardiac and respiratory arrest. The selection of medications to reestablish cardiac function
would stimulate the sympathetic nervous system beta1 receptors. This stimulation would result in
increased automaticity and which of the
following?
a. Increased myocardial contractility
b. Decreased left ventricular stroke work
c. Decreased myocardial oxygen consumption
d. Increased left ventricular afterload - Correct answer: a
Rationale: The sympathetic nervous system contains alpha, beta, and dopaminergic receptors that
produce various responses when stimulated. Stimulation of beta1 receptors increases heart rate,
conductivity, and myocardial contractility. Stimulation of beta2 receptors produces vasodilation and
bronchodilation. Alpha receptors, when stimulated,
produce vasoconstriction. Stimulation of dopaminergic receptors produces a vasodilating
effect on renal, mesenteric, coronary, and cerebral vessels.
Test-Taking Strategy: Note the helpful clue in the stem: stimulate the sympathetic system and recall that
this results in a fight-or-flight response—the body is responding to survive. Stroke volume would
increase, so eliminate option b. Afterload would increase, but this is due to alpha stimulation, not beta1
stimulation, so eliminate option d. Because the heart is working faster and harder, the myocardial oxygen
consumption does increase, so eliminate option c. Remember that the primary effects of beta1 receptors
are to increase heart rate, contractility, and rate of conduction. Choose option a. A memory aid that also
may help is this: beta 1 beta 2, 1 heart 2 lungs: beta1 affects the heart, and beta2 affects the lungs.
A patient arrived in the emergency department with complaints of chest pain. The 12-lead
electrocardiogram shows ST segment elevation in leads V3 and V4. Occlusion of the affected coronary
artery most likely would affect perfusion to which portion of the
conduction system?
a. Sinoatrial (SA) node
b. Bachmann's bundle
c. Atrioventricular (AV) node
d. Bundle of His - Correct answer: d
, Rationale: ST segment elevation in leads V3 and V4 indicates injury to the anterior wall, which would
occur with occlusion of the left anterior descending (LAD) artery. In most persons, the SA node,
Bachmann's bundle, and AV node are supplied by the right coronary artery. The bundle of His is supplied
by the left anterior descending artery. This is why an
anterior myocardial infarction may cause type II second-degree AV block or third-degree AV heart block
at the level of the bundle of His.
Test-Taking Strategy: Note that options a, b, and c are part of the supraventricular conduction system.
They usually are supplied by the right coronary artery. The LAD artery supplies most of the
interventricular conduction system, including the bundle of His and
the bundle branches.
Which of the following types of block are most likely after an anterior wall myocardial infarction (MI)?
a. Sinus block
b. Second-degree atrioventricular (AV) block, type I
c. Second-degree AV block, type II
d. Third-degree AV block with junctional escape rhythm - Correct answer: c
Rationale: Anterior MI is caused by a left anterior descending (LAD) artery lesion. The LAD artery supplies
the bundle of His and bundle branches, so anterior MIs may cause blocks of the bundle of His or bundle
branches. Second-degree AV block type II is a block at the level of the bundle of His. If this patient does
develop a third-degree AV block, it would be at the level of the bundle of His, and the only escape
rhythm available below the bundle of His is a ventricular escape rhythm.
Test-Taking Strategy: The sinus node is supplied by right coronary artery (in 55% of people) or left
coronary artery (in 45% of people), so eliminate option a. Type I AV block, also called Wenckebach, is a
block at the AV node, and the AV node is supplied by right coronary artery (in 90% of people) or left
coronary artery (10%), so eliminate option b. The
LAD artery supplies the bundle of His, and blocks in this area would eliminate the possibility of junctional
escape rhythms, so eliminate option d. Choose option c.
A shift in the point of maximal impulse (PMI) to the fifth left intercostal space at the anterior axillary line
could be caused by any of these conditions except:
a. left ventricular hypertrophy.
b. right tension pneumothorax.
