CRL Quiz 2 2010

1

Which one of the following statements regarding the electrocardiogram (ECG) is NOT CORRECT?


  The ECG can indicate the timing of atrial repolarisation.

  The ECG can indicate the presence or absence of atrial depolarisation.

  The ECG can indicate on which side of the body is the heart.

  The ECG can indicate the conduction through the bundle branches.

  The ECG can indicate the right ventricular size.


The magnitude (small) and timing (around time of ventricular depolarisation) of the atrial repolarisation means that is not visible on a normal ECG.

2

Which one of the following statements regarding the regulation of arterial tone is NOT CORRECT?


  The myogenic response is stimulated by changes in arterial pressure.

  Endothelium dependent vasodilatation depends on nitric oxide.

  Activation of the sympathetic nervous system usually causes a reduction in organ blood flow.

  Endothelium dependent vasodilatation is seen in veins.

  An increase in tissue pH will result in local systemic arterial vasodilatation.


It is a decrease in tissue pH, usually a side-effect of metabolic activity, that will cause arterial vasodilatation.

3

Which one of the following statements regarding blood pressure control is NOT CORRECT?


  A reduction in blood pressure results in reduced discharge of the carotid baroreceptor nerves.

  Parasympathetic nerves are important in the control of total peripheral resistance.

  Sympathetic nerve activity is less when lying than when standing.

  Hypertrophy of small arteries can contribute to chronic increases in blood pressure.

  Changes in the renal pressure-natriuresis relationship can result from blood pressure changes long-term.


The parasympathetic nerves have no role in the control of TPR, which is dependent on the degree of activation of the sympathetic innervation of the systemic arteries.

4

Which one of the following statements regarding blood pressure is NOT CORRECT?


  Body mass index correlates with blood pressure.

  Height is the closest correlate of blood pressure during adolescence.

  Pulse rate and blood pressure tend to show the same changes during the day.

  Diastolic pressure tends to rise with old age.

  Average male blood pressure is not always higher than average female blood pressure.


Diastolic pressure tends to fall with increasing age over 60 years. This is the result of a reduction in large arterial compliance (loss of elastin, more collagen) that results in increased pulse pressure - therefore, higher systolic and lower diastolic around the mean arterial pressure.

5

A patient in the emergency department is pale, has a low blood pressure and the jugular venous pressure is low. He doesn't have chest pain or shortness of breath. The most likely cause for his presentation is


  cardiac failure.

  internal haemorrhage.

  pulmonary embolism.

  fluid overload.

  renal failure.


Of the 5 clinical conditions only internal haemorrhage will result in low JVP. The others are associated with an increase in JVP.

6

A 54 year old man comes in to clinic and wants to know his risk for having a heart attack in the next 5 years. Which one of the following will most increase his risk?


  High HDL (high density lipoprotein).

  Low diastolic blood pressure.

  Family history of father having heart attack at age 75.

  High LDL (low density lipoprotein).

  High stress occupation.


Atherosclerosis risk factors include age, male gender, family history (1st degree relative under 60years of age), high LDL (OPTION D), low HDL, cigarette smoking, hypertension and diabetes mellitus.

7

Which one of the following statements about the β-adrenoceptor antagonist atenolol is correct?


  It causes vasodilatation.

  It is a non-selective β-adrenoceptor antagonist.

  It is commonly used in hypertensive patients with asthma.

  It may cause cough as an adverse effect.

  It may be used to prevent angina attacks.


Beta-adrenoceptor antagonists, of which atenolol is given as an example, may be used to prevent angina attacks as discussed in the lectures.
Atenolol happens to be a cardioselective drug but you did not have to know this for Option E to be the correct answer.
The other options are class effects: For the beta-adrenoceptor antagonists we talked about reflex vasoconstriction as an initial response as well as potentially opposing any beta2-mediated dilation if they were non-selective. Cold extremities is a potential adverse effect. This class of drugs are to be avoided in asthma whether cardioselective or not. Cough is a class effect of the ACE inhibitors not the beta-adrenoceptor antagonists.

8

The anti-anginal vasodilator drug glyceryl trinitrate may be administered as a sublingual tablet or transdermally (via the skin), but not via the oral (swallowed) route because


  it is rapidly metabolised in the liver.

  it causes severe vomiting.

  it enters an entero-hepatic shunt.

  it is not absorbed across the mucous membranes of the stomach or intestine.

  it is destroyed by the bacterial flora of the gastro-intestinal tract.


All the options are reasons why drugs may have a low bioavailability and alternative routes of administration need to be considered. For the nitrate class of antiianginal drugs, it is the case that their actions depends on conversion to NO by specific enzymes, but they are also rapidly inactivated by the liver (OPTION A) before they can donate their NO when administered orally.

9

Which one of the following statements about digitalis glycosides is NOT CORRECT?


  They increase the force of myocardial contraction.

  They are useful in the treatment of atrial arrhythmias.

  They increase atrioventricular conduction.

  They have a low therapeutic index.

  They are useful in the treatment of congestive cardiac failure.


The cardiac glycosides, of which digoxin extracted from digitalis was given as an example, possess all the above properties except OPTION C. When used as antiarrythmics they are useful in atrial fibrillation and their benefit derives from slowing AV conduction and increasing vagal tone.

10

Which one of the following side effects may be seen after administration of a thiazide diuretic?


  Hyperkalaemia.

  Hypoglycaemia.

  Hyperuricaemia

  Cerebral oedema

  Hypertension.


This class of diuretic drug inhibit the Na/Cl transporter in the distal tubule. This then promotes K loss from the collecting ducts and they have a tendency to cause hyperglycaemia. A and B incorrect. They do increase plasma uric acid, probably by inhibiting secretion from the peritubular capiliaries into the lumen. C is correct. Cerebral oedema and hypertension are unlikely side effects as they useful in reducing blood volume. D & E incorrect.

11

A patient dies some time after suffering a myocardial infarct. At autopsy you see granulation tissue growing into the edges of the necrotic muscle. This tells you the patient survived how long after the infarct before dying?


  3 minutes.

  3 hours.

  3 days.

  3 weeks.

  3 months.


Removal of necrotic debris is followed by the commencement of ingrowth of granulation tissue at 3 days. By 3 weeks granulation tissue has usually replaced the dead material and is beginning to mature into scar tissue. (Remember the case at the Alfred where the presence of early stage granulation tissue was used as supporting forensic evidence for the shooting occurring 3 days prior).

12

A patient is admitted to hospital with severe hypertension (their arterial blood pressure is 260/150 mmHg). They die several days later. At autopsy which one of the following changes would you expect to see either macroscopically or down the microscope?


  Renal artery aneurysms.

  Fibrinoid necrosis of arterioles with leakage of red blood cells.

  Acellular or hyaline arteriolar wall thickening.

  Acute myocardial infarction.

  Portal vein wall thickening.


Fibrinoid necrosis is the characteristic arteriolar abnormality in very severe hypertension.

13

Aortic dissection (dissecting thrombus) typically DOES NOT occur in the setting of severe and widespread atherosclerosis because


  individuals with risk factors for atheroma don't share risk factors for aortic dissection.

  the medial layer in atherosclerotic vessels is thickened with fibrosis, preventing dissection propogation.

  dilation of the aorta is common in aortic dissection but rare in tissues affected by atherosclerosis.

  aortic dissection is usually initiated by a tear in the adventitia.


Individuals with hypertension are at risk for both atherosclerosis and dissecting thrombus. Dissecting thrombus begins with an intimal tear that spreads to the media and propogates by dissecting the media away from the other vessel layers. In those with widespread advanced atherosclerosis the media becomes fibrotic and stiff and this feature is thought to be protective against thrombus propogation.

14

You have performed a fitness test at your gym that involved cycling on an exercise bike. Each minute the work load has been increased. After 8 minutes you have reached your maximum exercise capacity (VO2 max) and you stop cycling, because of breathlessness and fatigue in your legs. Which one of the following statements is most correct?


  The breathlessness implies that you have reached your maximum ventilatory capacity.

  Just before you cease cycling, it is likely that your tidal volume will be about 30% of your vital capacity.

  If you are well trained and fit, it is likely that your anaerobic threshold will occur at about 30% of your VO2 max.

  At the end of cycling, your serum bicarbonate level will be lower than usual.

  Your maximum heart rate will increase if you attend the gym more frequently.


At the end of maximum exercise, there is a lactic acidosis and bicarbonate will be reduced. Breathlessness is a common symptom at maximal exertion, however in normal people, ventilatory capacity has not been reached.

15

A patient undergoing replacement of the mitral valve with a metal prosthetic valve is treated initially with heparin, and later commences warfarin therapy. Which one of the following statements best describes the therapeutic rationale underpinning this therapeutic protocol?


  Warfarin is administered as a pro drug that requires bioactivation in the liver, whereas heparin is immediately active.

  Due to its large molecular weight, heparin can only be administered by injection, whereas warfarin can be given orally, so is more suitable when the patient is discharged.

  Heparin has activity against preformed clotting factors, whereas warfarin prevents the formation of clotting factors.

  Warfarin has fibrinolytic activity, whereas heparin does not.

  The half life of warfarin is longer than the half life of heparin.


Whilst each of B, C & E are correct statements, Option C provides the best explanation of the rationale for the use of warfarin in this context. Initial heparinisation followed by warfarinisation allows for the procedure to be performed and ensures minimally clotting immediately and then long term anticoagulation. The statements in B & E are secondary considerations to these. Warfarin is not a prodrug nor does it have marked fibrinolytic activity.