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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3981_Библиотеки_им_академика_М_И_Перельмана.pdf
Preface
Recent reforms in medical education worldwide have prompted replacement of subjective
examination methods with Multiple Choice Questions (MCQs) and Single Best Answer
(SBA) questions at all levels. In fact single best answer questions are fast becoming the sole
method of assessment in the undergraduate as well as postgraduate examinations. This first
edition of “Single Best Answer Questions in Cardiothoracic Surgery” provides a
comprehensive revision aid to the candidates taking the specialty examination in
Cardiothoracic Surgery worldwide. This new revision aid provides over 300 single best
answer practice questions in Cardiothoracic Surgery and conforms to the recent changes in
the format of specialty examinations in Cardiothoracic Surgery. Each question has been
carefully formulated to cover an important topic in Cardiothoracic Surgery. The questions
cover the complete specialty examination syllabus and a considerable number of these have
been based on previous examination questions. This book contains a substantial number of
patient-based questions or clinical vignettes that will enable prospective candidates to test
their ability to integrate key basic science concepts with relevant clinical problems. In
addition factual recall questions have also been included that probe for basic recall of facts.
Detailed and comprehensive explanations, rather than just brief answers, to questions have
been provided so that the candidates do not have to consult textbooks for clarification as is the
case with most other MCQs books currently available in the market. A list of relevant
references is provided at the end of each answer to enable candidates to read the most up to
date journal articles on the subject. The questions in this book can be used in a number of
ways: (1) as a diagnostic tool (pretest), (2) as a guide and focus for further study, and (3) for
self-assessment. The least effective use of these questions is to ―study‖ them by reading them
one at a time, and then looking at the correct response. These over 300 practice questions are
intended to be an integral part of a well-planned review as well as an isolated resource. If
used appropriately, these questions can provide self-assessment information beyond a
numeric score. Furthermore, the questions have been planned in such a way that this book can
be used as companion to any textbook of Cardiothoracic Surgery.
I am hopeful that this book will prove a useful revision and self-assessment tool
specifically for FRCS Cardiothoracic Surgery candidates as well as for all those taking single
best answer questions- based postgraduate examinations in Cardiothoracic Surgery.
Shahzad G. Raja
London
July 2013
Section One: Questions
Chapter I
Basic Sciences
1.1 A forest plot is a graphical display designed to illustrate the relative strength of
treatment effects in multiple quantitative scientific studies addressing the same question.
In a forest plot
A. the area of each square is proportional to confidence interval.
B. the left-hand column is a plot of the measure of effect (e.g., an odds ratio) for each of
the included studies.
C. the left-hand column lists the names of the studies.
D. the meta-analysed measure of effect is commonly plotted as a circle.
E. the overall meta-analysed measure of effect is often represented on the plot as a
horizontal line.
1.2 Dopamine acts on dopaminergic
and adrenergic receptors to elicit a multitude of
clinical effects. Dopamine
A. at a dose of 0.5 to 3 µg · kg
–1
· min
–1
increases glomerular filtration rate.
B. has direct natriuretic
effects through its action on renal tubules.
C. is the immediate
precursor to epinephrine (adrenaline) in the catecholamine synthetic
pathway.
D. promotes β
1
-adrenergic receptors mediated vasodilatation at a dose of 10 to 20 µg ·
kg
–1
· min
–1
.
E. weakly binds to α
1
-adrenergic receptors promoting
norepinephrine release.
1.3 Normal cardiac function is dependent on a constant resynthesis of adenosine
triphosphate (ATP) in the mitochondria. Which of the following statements regarding
myocardial energetics is correct?
A. Anaerobic enzymes are present in abundance in the heart.
B. During exercise lactate can
account for up to 70% of the metabolism.
C. In the fasting state, carbohydrates account for 70% of
the fuel used by the heart.
D. Most of the ATP used by the heart is required for maintaining
the concentration
gradients across the cell membrane.
E. Nearly all chemical energy used by the heart is generated by anaerobic metabolism.
Shahzad G. Raja
4
1.4 The metabolic machinery in the heart is designed to generate large amounts of
adenosine triphosphate (ATP) to support high rates of external cardiac power. Which of
the following statements regarding carbohydrate metabolism in the heart is correct?
A. In the well-perfused heart, ∼60–90% of the acetyl-CoA comes from the oxidation of
pyruvate.
B. The glycolytic pathway generates four ATP molecules for each molecule of glucose.
C. The healthy nonischemic heart is a net consumer of lactate even under conditions of
near-maximal cardiac power.
D. Glucose transport across the cardiac sarcolemma is facilitated by the monocarboxylic
acid transporter-1 (MCT-1).
E. There is a translocation of glucose transporters from intracellular vesicles to the
sarcolemmal membrane in response to insulin stimulation.
1.5 The regulation of myocardial metabolism is linked to arterial carbon substrate
concentration, hormone concentrations, coronary flow, inotropic state, and the
nutritional status of the tissue. In the heart
A. under nonischemic conditions almost all (>95%) of ATP formation comes from GTP
formation in the citric acid cycle.
B. there is a relatively high ATP content and high rate of ATP hydrolysis.
C. approximately 60–70% of ATP is used for the sarcoplasmic reticulum Ca
2+
-ATPase
and other ion pumps.
D. there is complete turnover of the myocardial ATP pool approximately every 10 s
under normal conditions.
E. ATP content depletes rapidly with large increases in cardiac power such as during
intense exercise or acute catecholamine stress.
1.6 Dobutamine is a synthetic catecholamine with a strong affinity for both β
1
- and
β
2
-receptors. Dobutamine
A. has more affinity for β
2
-receptors.
B. produces mild vasoconstriction particularly at lower doses (≤5 μg · kg
−1
· min
−1
).
C. has mild chronotropic effect.
D. produces malignant ventricular arrhythmias at high doses only.
E. does not produce tolerance even when used for long periods.
1.7 Norepinephrine (noradrenaline) is a catecholamine. Norepinephrine
A. is a major endogenous neurotransmitter liberated by preganglionic adrenergic nerves.
B. primarily increases cardiac output.
C. has strong β-agonist activity, which renders it a powerful vasoconstrictor.
D. increases coronary flow due to its strong α
1
-adrenergic effect.
E. produces direct toxic effect on cardiac myocytes by inducing apoptosis via protein
kinase A activation and increased cytosolic Ca
2+
influx.
Basic Sciences: Questions
5
1.8 The nonapeptide vasopressin or “antidiuretic hormone”, isolated in 1951, is
stored primarily in granules in the posterior pituitary gland. Vasopressin
A. is released after decreased plasma osmolality.
B. is synthesized by the adrenal gland in response to increased catecholamine secretion.
C. stimulates V
1a
receptors to increase water reabsorption by enhancing renal collecting
duct permeability.
D. produces dose-dependent decrease in systemic vascular resistance.
E. augments nitric oxide production.
1.9 Levosimendan is one of the documented pharmacological agents used in the
management and treatment of acute and chronic heart failure. Levosimendan
A. increases
myocardial contractility by increasing intracellular calcium.
B. enhances the calcium-binding coefficient
of troponin C by stabilizing the
conformational shape of the
protein in its active form.
C. increases myocardial systolic force
but compromises coronary perfusion.
D. does not impair diastolic
function.
E. exhibits enhanced myocardial
contractility with increase in oxygen demands at
therapeutic doses.
1.10 Funnel plots, introduced by Light and Pillemer in 1984 and discussed in detail
by Egger and colleagues are useful adjuncts to meta-analyses. A funnel plot
A. is a graphical display designed to illustrate the relative strength of treatment effects in
multiple quantitative scientific studies addressing the same question.
B. assumes that the small studies will be near the average.
C. is a scatterplot of treatment effect against a measure of study size.
D. with asymmetric shape arises from a ‗well-behaved‘ data set.
E. has the treatment effect measure on the vertical axis.
1.11 Inhaled
nitric oxide is a therapy that promises to be extremely
valuable to the
cardiothoracic surgeon. It has been shown to
improve oxygenation in the setting of acute
lung injury and
to selectively lower pulmonary vascular resistance, without
producing
unwanted systemic vasodilation. Nitric oxide
A. is synthesized by constitutive nitric oxide synthase from the amino acid lysine.
B. produces pulmonary vasorelaxation through cyclic guanosine monophosphate.
C. has a half-life of 30 minutes.
D. is inactivated by binding to myoglobin.
E. has 300 times more affinity for haemoglobin compared to oxygen.
1.12 The therapy of pulmonary hypertension has evolved rapidly in the last 10 years
from the use of non-selective vasodilators to drugs that specifically target pulmonary
vasodilation, endothelial function, and vascular remodeling. Sildenafil is a
phosphodiesterase type 5 inhibitor that has an expanding role in the treatment of
pulmonary hypertension. Which of the following statements regarding sildenafil is
correct?
Shahzad G. Raja
6
A. Sildenafil specifically degrades cyclic adenosine monophosphate.
B. Sildenafil augments the degradation of cGMP by phosphodiesterase 5.
C. Metabolism of sildenafil occurs primarily by hepatic cytochrome P450 enzymes.
D. Sildenafil elevates cAMP levels in myocardium.
E. Sildenafil has direct inotropic effect on human heart.
1.13 A scheme proposed originally by Vaughan Williams and modified
subsequently
is used often to classify antidysrhythmic
agents. According to Vaughan Williams
classification
A. Class I agents bind most avidly to open K
+
channels.
B. Class I agents dissociate from Na
+
channels during phase 2 of the action potential.
C. Sotalol is a class II agent.
D. Class IV agents carry the risk of torsades de pointes.
E. Class III drugs cause prolongation of action potential.
1.14 Intravenous amiodarone has become one of the most administered
intravenous
antiarrhythmics used in cardiac surgery because
of its broad spectrum of efficacy.
Amiodarone
A. causes increased QRS duration and QT interval after acute intravenous administration.
B. has a huge volume of distribution.
C. is primarily indicated for atrial fibrillation refractory to other therapy.
D. has a true elimination half-life of 40 to 60 days.
E. causes pulmonary toxicity following acute administration.
1.15 Heparin is a universally used anticoagulant for cardiac surgery. Which of the
following statements regarding heparin is correct?
A. Heparin that is used for cardiac surgery includes fragments
that range from 30 to 300
Da.
B. Heparin acts as an anticoagulant by binding to factor XII.
C. Heparin-induced thrombocytopenia is produced by IgM antibodies to the
composite of
heparin–platelet factor 4.
D. Low molecular weight heparin affects activated clotting time more than unfractionated
heparin.
E. Low molecular weight heparin inhibits both
factor Xa and thrombin.
1.16 Loop diuretics include furosemide, bumetanide, and ethacrynic acid. Loop
diuretics
A. act on the thick ascending loop of Henle
to inhibit the Na
+
-K
+
-2Cl
–
cotransport
mechanism.
B. have a longer duration of action when administered intravenously.
C. decrease the release of renin and prostaglandin.
D. produce metabolic acidosis.
E. increase renal blood flow and glomerular filtration rate concomitantly.
Basic Sciences: Questions
7
1.17 Cytokines are small, cell-signaling peptides produced and released into
blood or
the extravascular environment by both blood and tissue cells.
Cytokines stimulate
specific receptors on other cells to initiate a
response in that cell. Which of the following
statements regarding cytokines is correct?
A. Interleukin (IL)-1-beta and
TNF-alpha are delayed response cytokines.
B. The major anti-inflammatory cytokine involved during cardiopulmonary bypass is
IL-
10.
C. IL-8 induces production of IL-1
receptor antagonist (IL-1ra).
D. TNF-alpha down-regulates production of IL-1, IL-8,
and IL-10.
E. IL-1 reduces monocyte production of reactive oxidants.
1.18 Aprotinin has been used clinically to enhance hemostasis for decades and was
approved in the United States by the Food and Drug Administration in 1993 to reduce
the transfusion requirement during coronary artery bypass surgery. Marketing of
aprotinin ceased recently when observational studies and a randomized clinical trial
reported increased cardiovascular morbidity and mortality in patients receiving this
drug. Aprotinin
A. strongly inhibits
kallikrein.
B. plasma concentrations of 250 to 400 KIU are required to fully inhibit plasmin.
C. enhances neutrophil transmigration.
D. increases IL-10 synthesis.
E. enhances expression of ICAM-1 and vascular cell adhesion molecule-1
by endothelial
cells.
1.19 Hypothermia is the most efficient measure to prevent or reduce ischemic
damage to the central nervous system when blood circulation is
reduced. The central
nervous system has a high metabolic rate
and limited energy stores, which make it
extremely vulnerable
to ischemia. Which of the following statements regarding cerebral
metabolic rate is correct?
A. The brain uses up to 50% of total-body oxygen consumption.
B. 90% of brain energy is used in the transmission of nerve impulses.
C. The brain has an ischemic tolerance of 5 minutes at normothermia.
D. The reduction
in metabolic rate of brain in relation to temperature espouses a sigmoid
curve.
E. There is a greater drop in metabolic rate of brain at low temperatures than at high
temperatures.
1.20 Two strategies for blood gas management are possible during
hypothermia.
Which of the following statements regarding pH management during hypothermia is
correct?
A. In vivo, the hypothermic blood is alkaline and hypocapnic.
B. pH-stat management aims at maintaining normal pH and blood gases in the rewarmed
blood.
C. pH-stat management preserves autoregulation of brain perfusion and
optimizes cellular
enzyme activity.
Shahzad G. Raja
8
D. Alpha-stat management results
in a powerful and sustained dilatation of the cerebral
vessels.
E. Cerebral oedema is less likely to occur with pH-stat management.
1.21 The action potential represents the triggered response to a
stimulus derived
either internally (slow depolarizing ionic
currents) or externally (depolarization of
adjacent cells). In the cardiac myocyte
A. the "fast" calcium channels open as the transmembrane potential decreases to
approximately –65
mV.
B. phase 1 of the action
potential is caused by transient potassium current.
C. the plateau
of the action potential (phase 2) is sustained at a neutral
or slightly positive
level by an inward-flowing sodium current.
D. phase 3 of the action
potential is caused by transient calcium current.
E. during relative refractory period some of the chloride channels are reactivated.
1.22 Pressure-volume loops can be used to analyze various physiologic situations.
Which of the following statements regarding pressure-volume loops is correct?
A. Increased afterload moves the end-systolic pressure-volume point
slightly downward
and to the right.
B. Adrenergic
stimulation at constant stroke volume shifts the pressure-volume
loop to
the right.
C. Acute ischemia shifts the pressure-volume
loop to the right and upward.
D. In the dilated heart of chronic congestive
heart failure the pressure-volume loop is
shifted
to the left.
E. In the hypertrophied heart the pressure-volume loop shifts to the right.
1.23 Coronary blood flow is delivered to the
heart through large epicardial
conductance vessels and then
into the myocardium by penetrating arteries leading to a
plexus
of capillaries. Which of the following statements regarding coronary blood flow is
correct?
A. Resting coronary blood flow is 100 mL/g of
heart muscle per minute.
B. Blood flow in the left coronary artery is constant during the cardiac cycle.
C. There is a greater capillary density per square
millimeter in the subepicardial tissue
than in the subendocardium.
D. During systole subepicardial vessels are perfused preferentially.
E. Flow to the subendocardium
is effectively autoregulated as long as the pressure in the
distal coronary artery is above approximately 40 mm Hg.
1.24 A 68-year-old woman following prolonged surgery to repair acute aortic
dissection was transferred to intensive care unit. The nurse on arrival noticed multiple
ecchymoses of the skin. An urgent full blood count and coagulation screen were sent.
Her prothrombin time (PT) was 38 seconds and partial thromboplastin time (PTT) 55
seconds. A full blood count showed a WBC count of 5300/µL, haemoglobin 8.1 g/dL,
haematocrit 24.9%, MCV 99 fL, and platelet count 16,300/µL. Her D-Dimer test was
very high. She most likely had