Cardiovascular physiology

Question 1

10018 – Vasodilator metabolites which relax arterioles and precapillary sphincters include
1: endothelium 1
2: thromboxane A2
3: lactate
4: circulating Na+ - K+ AT Pase inhibitor

Answer 1

FFTF
Ganong, 19th ed, Ch 31

Question 2

13289 – Which of the following is an enzyme?
A. bradykinin
B. angiotensin II
C. vasopressin
D. gastrin
E. rennin

Answer 2

E
The nonapeptide bradykinin is one of the vasodilator peptides formed in the plasma. The octapeptide angiotensin II is the most potent vasoconstrictor known and acts directly on the adrenal cortex, on peripheral noradrenergic neurons, and on water metabolism as well. The nonapeptide vasopressin (ADH) is one of the two posterior pituitary gland hormones. Its main physiologic effect is the retention of water by the kidney. Gastrin is a polypeptide hormone produced by the G cells of the gastric antral mucosa. Its principal action is stimulation of gastric acid and pepsin secretion. The above mentioned four physiologically active peptides (or polypeptides) have no enzymatic activity (A, B, C and D false).
Renin is a proteolytic enzyme secreted by the kidney into the bloodstream, with a molecular weight of 40 000 in humans. It splits the end off one of the plasma proteins called renin substrate, to release a decapeptide, angiotensin I (E true).

Question 3

23189 – Atrial natriuretic peptide production
1: is increased when ECF volume increases
2: increases sodium excretion by increasing glomerular filtration rate
3: lowers the blood pressure
4: stimulates the secretion of renin and angiotensin

Answer 3

TTTF
Ganong CHAPTER: 24 PAGE: 386

Question 4

13645 – With regard to sympathomimetic amines
1: dopamine acts on alpha, beta 1 and beta 2 and specific ‘dopaminergic’ receptors
2: isopreterenol acts predominantly on beta 1 and beta 2 adrenergic receptors
3: noradrenaline has little or no effect on alpha adrenergic receptors
4: adrenaline acts on alpha, beta 1 and beta 2 adrenergic receptors

Answer 4

TTFT
The catecholamines vary in the degree to which they engage the receptors specific to catechol effects. This fact is revealed within the spectrum of agonist drugs used clinically. Dopamine acts on its own receptor and on alpha, beta 1 and beta 2 receptors (A true). Noradrenaline and adrenaline can engage alpha, beta 1 and beta 2 receptors (D true, C false) but isoproterenol is the most selective in being agonist to only beta 1 and beta 2 receptors (B true).

Question 5

13579 – In the carcinoid syndrome vasoactive substances which may be released include
1: serotonin
2: bradykinin
3: prostaglandin
4: histamine

Answer 5

TTTT
Apart from serotonin (5-hydroxy-tryptamine), which is the best known vasoactive substance produced by carcinoid tumours, several other vasoactive agents are secreted by these tumours. All the compounds enumerated in this question can be present in the carcinoid syndrome.

Question 6

12833, 23254 – Prostacyclin (PGI2)
1: causes vasoconstriction
2: stimulates renin secretion
3: inhibits blood clotting
4: mimics the effects of oestrogen

Answer 6

FTTF
Prostacyclin (PGl2) is derived from arachidonic acid which is closely related to, but has slightly different actions from, the prostaglandins and thromboxanes. It is produced by endothelial and smooth muscle cells in blood vessels and generally promotes blood flow. It inhibits platelet aggregation (C true) and is a vasodilator (A false). It stimulates renin secretion by a direct action on the juxtaglomerular cells and indirectly by reducing blood pressure (B true). There is no evidence that its actions mimic those of oestrogen (D false).

Question 7

10008 – The factors influencing the total cerebral blood flow include
1: cerebral metabolic rate
2: the arterial pressure at brain level
3: mainly noradrenergic and cholinergic nerve fibres
4: the venous pressure at brain level

Answer 7

FTFT
Ganong, 19th ed, Ch 32.
Please note that cerebial metabolic rate remains remarkably constant irrespective of brain activity, in contrast to many other tissues.

Question 8

20481 – S. Increased intracranial pressure causes hypertension and bradycardia BECAUSE R. with increased intracranial pressure there is stimulation of the vasomotor centre due to local accumulation of carbon dioxide

Answer 8

S is true, R is true and a valid explanation of S
Guyton 7th ed. Page: 250-251

Question 9

27168 – Coronary blood flow has all the following characteristics except
A. high oxygen extraction fraction of about 70% at rest
B. nearly 100% oxygen extraction during exercise
C. a large increase in flow, up to five or six times, during maximal exercise
D. limitation of increased flow in exercise in the presence of proximal stenoses
E. flow peaking during systole when the driving pressure is greatest

Answer 9

E
The heart is extremely aerobic, burning fatty acids, ketones and some glucose continuously. The extraction fraction is large at rest, and can therefore be increased only moderately, so that increased oxygen delivery during exercise depends on increased flow. For the left ventricle, pressure within the myocardium limits flow during systole. Maximal flow occurs during diastole, so E, being incorrect, is the required answer.

Question 10

9922 – Concerning the conducting system of the heart
1: stimulation of cholinergic vagal fibres to nodal tissue decreases potassium ion conductance
2: depolarization of the ventricular muscle starts on the right side of the interventricular system
3: the last part of the heart depolarized is the epicardial surface of the left ventricular apex
4: stimulation of sympathetic cardiac nerves results in increased intracellular cyclic AMP

Answer 10

FFFT
Ganong, 19th ed, Ch 28

Question 11

10109 – In regard to the overall synchronisation of the heart beat
1: right atrial systole precedes left atrial systole
2: right ventricular contraction precedes left ventricular contraction
3: right ventricular ejection precedes left ventricular ejection
4: pulmonary valve closure precedes aortic valve closure

Answer 11

TFTF
Ganong, 19th ed, Ch 29

Question 12

10003 – In atrial flutter
1: the atrial rate is 150-220/min
2: there is accelerated AV conduction
3: the heart rate is irregular
4: the ventricular rate can be slowed by carotid sinus pressure

Answer 12

FFFT
Ganong, 19th ed, Ch 28
1: atrial rate = 300/min. Ventricular rate = 150 (2:1 block), 100 (3:1 block) or 75 (4:1 block)

Question 13

9933 – In accelerated atrio-ventricular conduction (Wolff-Parkinson-White-Syndrome) the electrocardiograph may show
1: an abnormal P wave
2: paroxysmal atrial tachycardia
3: a short PJ interval
4: normal QRS complex

Answer 13

FTFF
Ganong, 19th ed, Ch 28
4: delta wave

Question 14

14626 – In accelerated atrio-ventricular conduction (Wolff-Parkinson-White syndrome)
1: there is a prolonged PR interval and prolonged QRS complex slurred on the upstroke
2: circus movement tachycardia is usually initiated by an atrial premature beat
3: the arrhythmia commonly progresses to complete heart block
4: atrial fibrillation is a life threatening arrhythmia

Answer 14

FTFT
Refer to Ganong, 19th Ed, Ch 28, page 534

Question 15

15448 – The QT interval of the electrocardiogram
1: varies inversely with heart rate
2: has a normal duration of 0.6 seconds
3: corresponds to electrical systole
4: is prolonged in hypokalaemia

Answer 15

TFTF
Refer to Ganong, 19th Ed, Ch 28, page 526 and following

Question 16

25686 – In a post-operative surgical patient with a tachycardia of 120 bpm
A. acute atrial fibrillation is the most likely cause
B. biochemical disorders associated with tachycardia include hypokalaemia and hypermagnesaemia
C. supraventricular tachycardia is associated with narrow QRS complexes whereas a broad complex is more likely in ventricular tachycardia
D. multifocal ectopics in a 12 lead ECG imply myocardial infarction or an electrolyte disorder
E. amiodarone is a useful medication for atrial flutter and supraventricular tachycardia

Answer 16

C

Question 17

9856 – S: Injections of noradrenaline cause coronary vasodilation because R: injections of noradrenaline produce vasodilator metabolites as a result of increased myocardial activity

Answer 17

S is true, R is true and a valid explanation of S
Ganong, 19th ed, Ch 32

Question 18

15057 – Alpha adrenergic blocking agents can be used in refractory shock to
1: increase blood pressure
2: increase renal blood flow
3: increase venoconstriction
4: prevent the imbalance between precapillary and venular tone

Answer 18

FTFT

Question 19

25830 – Concerning inotropes
1: they ideally should reduce afterload and preload as well as increasing cardiac output and ejection fraction
2: adrenaline is an ideal all-around inotrope
3: higher doses are used to compensate for hypovolaemia
4: their safe use requires a full range of monitoring being available

Answer 19

TFFT

Question 20

27192 – In a failing left ventricle all of the following parameters are reduced except
A. ejection fraction
B. end-systolic volume
C. rate of rise of pressure (dP/dt) at the commencement of systole
D. stroke-volume at a given filling pressure
E. systolic shortening of myocardial fibre length

Answer 20

B
The biochemical changes in a failing ventricle lead to a shift of the Starling curve (stroke volume versus filling pressure) to the right. Changes in expression of myosin isoforms results in slower contraction with reduced dP/dt, which is an important index of ventricular function derived during catheter studies. Stroke volume is reduced at each value of filling pressure, so that systolic fibre length shortening is reduced, ejection fraction falls, and end systolic volume increases. Thus B, being incorrect, is the required answer.

Question 21

27210 – Isometric contraction of the left ventricle
A. occurs during the first third of systole
B. involves the most rapid change in pressure per unit time in the cardiac cycle
C. occurs after closure of the aortic valve
D. is terminated at the T wave of the ECG
E. is responsible for ejection of a majority of the stroke volume

Answer 21

B
During the cardiac cycle, the time sequence is: diastolic filling (with atrial systole in late diastole increasing filling); the QRS complex; ventricular contraction commencing at the peak of the R wave; A-V valve closure; isometric ventricular contraction (isometric means equal size: the volume does not change) with rapidly rising ventricular pressure; opening of the aortic and pulmonary valves as the ventricular pressure exceeds arterial diastolic pressure; rapid ejection in the first third of systole; slow ejection; the T wave; ventricular relaxation with falling ventricular pressure; aortic and pulmonary valve closure and the dicrotic notch in the arterial pressure waveform; isometric relaxation; opening of the A-V valves; rapid phase of diastolic filling. Isometric contraction occurs at the commencement of systole, does not involve any ejection of blood, and is the steepest part of the pressure-time graph.
Answer B is the only one correct.

Question 22

27246 – S: Patients with severe aortic stenosis causing left ventricular failure have poor outcomes from valvular surgery because R: impaired left ventricular function may persist after correction of the stenosis.

Answer 22

S is false and R is true
The long-term changes in ventricular function occurring in failure due to pressure overload, including pathological hypertrophy, fibrosis, vascular insufficiency and changes in myosin isoform expression, may persist postoperatively. However, the patient’s cardiac status is improved (often dramatically) by operation, because the large pressure gradient across the aortic valve is relieved and cardiac workload is greatly reduced. Thus, the assertion is false, and the reason given is a correct statement, but not a reason for the assertion.

Question 23

27222 – In a patient with mixed aortic stenosis and insufficiency due to rheumatic heart disease, deteriorating cardiac function could be exacerbated by all except
A. increased pressure gradient across the aortic valve
B. increased reflux through the aortic valve
C. increased aortic diastolic pressure
D. increased aortic systolic pressure
E. rapid heart rate

Answer 23

C
Cardiac workload is increased by both volume and pressure overload in valve disease. Systemic hypertension will add to the pressure workload and is a well-known, correctable factor in cardiac failure. The diastolic pressure has other implications, however. Because of the intramural pressure increase during systole, most of the left ventricular coronary blood flow occurs during diastole: therefore, diastolic pressure and time are important. The reduced aortic diastolic pressure seen with aortic incompetence will seriously compromise coronary flow. Thus, C is the only factor that improves rather than worsens the patient’s cardiac function, and is therefore the required answer.

Question 24

27204 – Essential differences between cardiac failure with diastolic dysfunction and failure with systolic dysfunction include all of the following except
A. diastolic filling pressure
B. ejection fraction
C. myocardial wall thickness
D. end-diastolic volume
E. end-systolic volume

Answer 24

A
Systolic dysfunction is the commoner pattern of failure, and is caused by ischaemic heart disease, myopathy, or severe volume or pressure overload from valve pathology: it results in a dilated ventricle (increased end diastolic volume) with reduced ejection fraction (giving increased end systolic volume).
Diastolic dysfunction is reduced ventricular compliance, as seen with extreme myocardial hypertrophy in, for example, hypertrophic subaortic stenosis, or longstanding severe hypertension. The hypertrophied, stiffer ventricle requires increased diastolic filling pressure. In this respect, it is similar to systolic dysfunction, though the mechanism is different (A correct).
With systolic dysfunction, the failing ventricle needs increased filling pressure to achieve increased end-diastolic volume and move it further up the Starling curve. With diastolic dysfunction, the increased stiffness requires increased filling pressure to approach a normal end-diastolic volume. The hypertrophied muscle has increased performance, so that the ejection fraction is increased.

Question 25

27234 – A congenital ventricular septal defect would be associated with all except
A. a pansystolic murmur
B. increased pulmonary blood flow
C. cyanosis from birth
D. possible late right ventricular failure
E. possible late pulmonary hypertension

Answer 25

C
Flow through septal defects follows the pressure gradients: therefore, both atrial and ventricular septal defects usually have left-to-right flow unless the pressures are highly abnormal. Cyanosis requires the delivery of deoxygenated blood to the left heart and so to the systemic circulation: ie right-to-left shunts. Left-to-right shunts do not result in cyanosis, though they increase pulmonary blood flow. A late sequel to the increased volume load on the right ventricle and pulmonary circulation may be attenuation of the pulmonary vasculature, pulmonary hypertension and right ventricular failure. The murmur of a VSD is pansystolic since it reflects only the pressure profile of the ventricle and not the acceleration of the long, massive, blood column in the aorta, which determines the diamond-shaped systolic murmur of aortic stenosis. All the options are plausible associations, except C, which is therefore the required answer.

Question 26

27216 – Volume overload in a left ventricle with valve pathology will occur with
A. aortic stenosis
B. aortic insufficiency
C. mitral stenosis
D. mitral insufficiency
E. combined aortic and mitral insufficiency

Answer 26

E
Cardiac output is actually regulated by factors external to the heart, so that the heart meets demands, unless the patient is in cardiogenic shock leading to circulatory failure. Cardiac output must be kept normal, despite changes in valve function. In aortic insufficiency, the stroke volume increases so that the output is kept normal despite part of the stroke volume being lost back into the ventricle during diastole. Likewise, in mitral insufficiency, the volume refluxing back into the atria must be pumped again at the next cycle. Aortic stenosis increases pressure workload, but does not increase volume load; while in mitral stenosis, the left ventricle is protected and the increased pressure is in the left atrium. The answer is option E, with both aortic and mitral insufficiency.

Question 27

27144 – A loud pericardial rub is consistent with
A. a small effusion
B. negligible risk of tamponade
C. an infective or systemic inflammatory process
D. widespread Q waves
E. none of the above features

Answer 27

C
Pericardial effusions are commonly due to infectious pericarditis (Coxsackie virus, influenza, echoviruses, HIV) or occasionally due to collagen diseases such as SLE (C correct). Because the fluid is often rich in fibrin, it may produce a loud rub, despite having a large volume that prevents contact between the myocardium and the pericardium. Thus, loud rubs are by no means inconsistent with large or even life-threatening effusions. The ECG changes reflect myocardial inflammation and are typically ST depressions and T wave changes, not the Q waves which are seen in full-thickness myocardial infarction.

Question 28

27108 – A majority of patients with significant pulmonary thromboembolism show
A. haemoptysis
B. friction rubs
C. clinical signs of deep vein thrombosis
D. cyanosis
E. tachycardia and dyspnoea

Answer 28

E
Pulmonary thromboembolism was recently the third most frequent cause of death in the USA. Clinical diagnosis is made difficult by the inconstancy of clinical signs: only a minority of patients present the textbook picture of haemoptysis, friction rub, gallop rhythm, cyanosis, wide fixed split of the second sound and signs of the source of the embolism from deep vein thrombosis in the legs. The majority of patients, however, do have tachycardia and dyspnoea, at least transiently (E True).

Question 29

25692 – Pulmonary artery flotation catheters
A. directly measure central venous pressure (CVP), pulmonary artery wedge pressure (PAWP), and cardiac index (CI)
B. show decreased readings of 1 mmHg for every 5 cm of PEEP applied
C. are likely to be correctly placed if wedged PaO2 < mixed venous PaO2
D. may migrate into the pulmonary veins with prolonged wedging leading to distal infarction
E. are essential for the management of high risk surgical patients with recent myocardial infarction

Answer 29

A

Question 30

15508 – The haemorrhage associated with streptokinase infusion is due to
1: Hypofibrinogenaemia alone
2: high levels of fibrin degradation products alone
3: high levels of plasminogen
4: high levels of fibrin degradation products and hypofibrinogenaemia

Answer 30

FFFT
Ganong Chapter 27, p525-6.

Question 31

15052 – In the foetal circulation
1: superior vena caval blood enters the left atrium via the patent foramen ovale
2: haemoglobin in the umbilical vein blood is 80% saturated with oxygen
3: inferior vena caval blood is directed via the ductus arteriosus to the head vessels
4: the inferior vena cava receives blood directly from the ductus venosus

Answer 31

FTFT
Refer to Ganong, 19th Ed, Ch 32, page 597 and following
1: IVC carries blood to right atrium which enters left atrium via foramen ovale. SVC carries deoxygenated blood to right ventricle –> pulmonary trunk –> ductus arteriosus.
3: IVC receives oxygenated blood directly from left umbilical vein via ductus venosus

Question 32

10129 – With respect to the fetus
1: umbilical venous haemoglobin saturation is 97%
2: haemoglobin F in fetal blood has a lower P50 than haemoglobin A in maternal blood
3: placental blood flow is about 20% of fetal cardiac output
4: superior vena cava blood is preferentially directed into the pulmonary circulation

Answer 32

FTFT
Ganong, 19th ed, Ch 32
1: 80%

Question 33

15443 – From Bernoulli’s principle of blood flow it can be derived that
1: the sum of the kinetic energy of flow and the pressure energy is constant
2: the energy lost in overcoming resistance is irreversible
3: the pressure drop due to conversion of potential to kinetic energy is reversible
4: in a narrowed segment of a vessel the velocity flow and lateral wall pressure are reduced

Answer 33

TTTF
Refer to Ganong, 19th Ed, Ch 30, page 560

Question 34

9928 – Mean venous pressure in the
1: dural sinuses is constantly negative
2: foot is higher when standing still than when walking
3: foot, when standing still, is 50 mmHg
4: subclavian vein, as it crosses the first rib, is positive above atmospheric pressure, when lying down

Answer 34

FTFT
Ganong, 19th ed, Ch 30

Question 35

25746 – A high CVP reading may be caused by all of the following EXCEPT
A. a rapid fluid bolus
B. pulmonary embolism
C. tension pneumothorax
D. supraventricular tachycardia
E. cor pulmonale

Answer 35

D

Question 36

10013 – On assuming the upright position
1: the arterial pressure at head level and the jugular venous pressure fall 20 - 30 mm Hg
2: cerebral vascular resistance is reduced
3: brain tissue pO2 is maintained by autoregulation
4: cerebral O2 consumption is about the same as in the supine position

Answer 36

FTFT
Ganong, 19th ed, Ch 33

Question 37

23184 – Acclimatization to altitude is associated with
1: enhancement of erythropoietin secretion and the circulating red cell mass
2: lactic acidosis in the brain causing a fall in CSF pH to enhance the ventilatory response to hypoxia
3: an increase in tissue content of cytochrome oxidase
4: an increase in red blood cell 2, 3 DPG which decreases O\b2 affinity of haemoglobin

Answer 37

TTTT
Ganong 13th Edition Chapter: 37 Page: 572-574.

Question 38

19156 – Extracellular edema may be caused by all of the following except
A. high venous pressure
B. increased arteriolar resistance
C. low plasma protein content
D. increased capillary permeability
E. lymphatic obstruction

Answer 38

B
Guyton 8th ed. Page: 281

Question 39

15062 – Negative gravitational forces acting on the body produce
1: increased cardiac output
2: increase in cerebral arterial pressure
3: ecchymoses around the eyes
4: mental confusion

Answer 39

TTTT
Refer to Ganong, 19th Ed, Ch 33, page 603

Question 40

27126 – The procedure and interpretation of the Brodie-Trendelenburg test include all the following except
A. the patient reclines with the leg elevated to empty the veins
B. the superficial veins are compressed in the thigh
C. the patient then stands while the veins are observed
D. rapid filling on standing of the superficial veins below the knee during the phase of compression indicates incompetent leg and ankle perforators
E. rapid filling of the long saphenous vein from above on release of the tourniquet indicates deep venous occlusion extending up to the saphenofemoral junction

Answer 40

E
The Brodie-Trendelenburg procedure is described correctly except for item E, which is therefore the required answer. Rapid filling from above of the long saphenous vein after removal of pressure from the saphenofemoral junction indicates incompetence of the saphenofemoral junction, rather than of the valves in the lower deep venous system. The Brodie-Trendelenburg test can sometimes be additionally useful in detecting incompetent lower leg and ankle perforators, which indicate severe dysfunction of the venomuscular pump. Duplex-Doppler venous flow studies are now increasingly used to pinpoint incompetent perforators.

Question 41

27083 – Venous pressure in the veins of the foot exhibits all the following properties except
A. in all subjects, increases on standing
B. in normal subjects, diminishes on exercise
C. in subjects with varicose veins but competent perforators, fails to diminish on exercise
D. in subjects with incompetence of the perforators and valves of the deep veins, remains elevated during exercise
E. in all subjects, diminishes on elevation of the legs

Answer 41

C
The key to understanding the pathology of the venous system of the lower limb is the operation of the veno-muscular pump. Simple physics dictates that the pressures in the veins of the dependent limb will tend to increase in the standing posture by up to the equivalent of a column of blood from ankle to heart - a little over a metre of water, about 100 millimetres of mercury. Pumping the blood up the limb on exercise depends on the competence of the valves in the ankle perforators and the deep veins. Cyclic compression of the deep veins pushes blood up the deep veins during their positive pressure excursions. Competent perforators allow blood from the saphenous system to enter the deep veins during their negative pressure excursions, without allowing that blood back into the superficial veins at the next contraction of leg muscles. Even patients with incompetence of the valves in the saphenous system, but competent perforators, experience a fall in venous pressure on walking - though it is not as marked as the fall with competent valves at all levels. Option C describes the behaviour incorrectly, and is therefore the required answer.