Case 4

Question 0

Outline the mechanism of action of GTN spray

Answer 0

An increase in Nitric Oxide activates guanylyl cyclase that raises cGMP that activates PKG that lowers calcium concentration in the Smooth muscle cell

Question 1

Contractile cells are at rest at what voltage? What channels are in adbundance here?

Answer 1

• membrane potential at -90 mV - several K + channels keeping at -90 mV

Question 2

What are the membrane potentials of Na, Ca K?

Answer 2

Na - 67 Ca +123 K -92

Question 3

What happens at contractile cells?

Answer 3

See pictures

Question 4

What is the refractory period?

Answer 4

Absolute refractory - during depolarisation, unable to stimulate Na + voltage gated channels as they are open or inactive (unable to stimulate unless they are closed) Relative refractory - during repolarisation, able to stimulate Na + channels as some of they have ‘reset’ as they are closed, however a significantly larger stimulus is required as only a few channels are closed

Question 5

In the ECG, break down what the QRS wave represents?

Answer 5

Q- interventricular septum depolarisation R - ventricular depolarisation going down S - late ventricular depolarisation (small areas of the ventricles activated at a later stage)

Question 6

What is your U wave?

Answer 6

Prolonged repolarisation of the ventricular repolarisation of perkinjie fibres

Question 7

What is the PR Interval normally?

Answer 7

0.12 - 0.2 secs (3-5 small sqaures)

Question 8

What is the normal QRS?

Answer 8

Less that 0.12 sec or 3 small squares

Question 9

Heart murmur what is it?

Answer 9

• turbulent flow of blood causing swooshing and wooshing

Question 10

Sinus tachycardia, what is it?

Answer 10

Rate is more than 100 bpm Regular QRS, may or may not get a P wave

Question 11

What is a cardia arrhythmia?

Answer 11

Disturbance in the initiation and propagation of action potential

Question 12

What area of the heart is most susceptible to damage?

Answer 12

The AV node

Question 13

Ectopic beats - what are they?

Answer 13

Cells other than pacemaker cells that initiate an action potential Are irregular and a thump

Question 14

What is first degree heart block?

Answer 14

When PR interval is MORE THAN 0.12-0.2 seconds Constant PR Interval

Question 15

What occurs in Second degree heart block?

Answer 15

Not every atrial impulse reaches the ventricles There are two types; Mobitz Type 1 Mobitz Type 2

Question 16

What is third degree heart block?

Answer 16

AV node fails to transmit any impulses

Question 17

What leads represent the RIGHT CORONARY ARTERY? What area of the heart is this?

Answer 17

Leads 2, 3 and AVF, Inferior side of heart

Question 18

What leads represent the Left Anterior Descending artery?

Answer 18

V1- V6 - anterior side of heart

Question 19

What chest leads represent the circumflex artery?

Answer 19

Leads 1, aVL, V5 and V6 Shows lateral side of heart

Question 20

Where are the chest leads placed for a 12 lead ECG?

Answer 20

V1 - 4th intercostal space (right) V2- 4th intercostal space (left) V4- 5th intercostal space, left midclavicular line v3- diagonally between v2, v4 V5 a left anterior axillary line V6- left mid axillary line

Question 21

Mali comes into the clinic to get her ECG done. This patient could have a blockage at her right coronary artery, which leads would you be looking at and why?

Answer 21

Looking at leads 2,3 and AvF As the right coronary artery runs at the inferior portion of heart which is represented by these leads

Question 22

What is a normal sinus rhythm?

Answer 22

60- 100 bpm Regular QTS P wave always preceding QRS - 1:1

Question 23

What is the function of endothelial cells?

Answer 23

Endothelial cells are involved in SAHIRS S- secrete Von Willerband Factor AH- Anti-haemostatic agents (nitric oxide, prostacyclin: prevent the aggregation of platelets) I- inflammatory response - histamine and bradykinin for vasodilation R- regulate vascular tone - by NO, EDHF, Endothelin (by sensing shear stress or by receptor agonists) S- semi-permeable

Question 24

Acetylecholine stimulates the release of what from endothelial cells?

Answer 24

Nitric oxide or endothelium derived relaxing factor

Question 25

What is the consequence of peroxinitrite production?

Answer 25

Interacts with lipids, DNA and proteins

Question 26

What are endothelum derived contracting factors?

Answer 26

An example is prostanoids. - when NO is impaired by stretch, ageing, hypertension - they reduce endothelium dependent vasodilations in aged subjects and in hypertensive patients

Question 27

What forced affect endothelial cells?

Answer 27

1) cyclic strain 2) fluid shear stress

Question 28

Where might you have disturbed shear stress in blood vessels?

Answer 28

1) areas of high curvatures 2) bifurcations

Question 29

How is nitric oxide produced by the endothelium?

Answer 29

1. **Agonist stimulated rise in intracellular Ca2+ and more Ca2+ influx** 2. **eNOS activated** and converts _L arginine to Nitric Oxide_ 3. _Important co factor is BH4 - tetrahydrobiopterin_

Question 30

What is the mechanism of action of NO?

Answer 30

1. ***NO diffuses from tunica intima to tunica media (smooth muscle cells)*** 2. ***Activates cGMP*** * less Ca2+ is mobilised from SR * less Ca2+ enters by L type Ca2+ channels * more Ca2+ uptake by SR * more Ca2+ extruded by calcium ATPase pump ***Activates (Ca2+ dependent) K+ channels, hyperpolarises membrane*** ***_All leads to vascular relaxation_*** *

Question 31

What are endothelium derived **hyperpolarising** factor?

Answer 31

* - bradykinins and Ach * - cause cell to **hyperpolarise and thus relax muscle** * - in absence of NO

Question 32

Mechanism of action of EDHF is similar to NO (i.e. increase in Ca2+ ) but what is the difference?

Answer 32

**Superoxide broken down to H2O2** **H2O2 potentiates EDHF**

Question 33

When does EDHF mechanism take action?

Answer 33

In notes, * Mainly in small arteries, arterioles * When **bioavailability of NO is compramised by increased superoxide production**

Question 34

What is prinzmetal angina?

Answer 34

Also known as coronary artery spasm, a temporary constriction within the vessel due to partial occlusion of the vessel by lipid build up

Question 35

Describe the features of this coronary artery histologically

Answer 35

Question 36

Describe the stages of atherosclerosis

Answer 36

Attatch

Question 37

What is the role of foam cells in artherogenesis

Answer 37

1- they promote movement of smooth muscle cells from media to intima 2- they promote smooth muscle cell proliferation (synthesises collagen and elastin) 3- they mediate SMCs to secrete calcium which hardens plaque 4- when the foam cells die, they increases chances of rupturing as they release all of their lipid content

Question 38

What does your first heart sound represent?

Answer 38

AV valves closing - LUB - onset of ventricular systole

Question 39

What does the second heart sound represent?

Answer 39

Closing of semilunar valve - DUB - onset of ventricular diastole

Question 40

What does the 4th heart sound represent?

Answer 40

Atrial contraction

Question 41

What does the 3rd heart sound represent?

Answer 41

Ventricular filling in early diastole

Question 42

Where might a murmur from regurgitant flow through the aortic valve occur, indicate where on an ECG?

Answer 42

Between the second and third heart sounds

Question 43

What is the significance of the fibrous skeleton?

Answer 43

1) atrioventricular rings of fibrous tissue 2) anchor valves 3) electrically insulating

Question 44

What are the four ways pain is brought about during cardiac ischaemia?

Answer 44

\*\*\* Pain helps daisy and me protect \*\*\* P - decreased perfusion pressure detected by pressure receptors h - hypoxia sensitised by chemoreceptors D - distention of cardial chambers M,p - pain inducing metabolites such as kinins

Question 45

What is stable angina?

Answer 45

- 'tight band like feeling at chest' - brought on by exertion - severity and frequency always the same - pain is relieved by resting, GTN med

Question 46

What is unstable angina?

Answer 46

1) 'tight band like feeling in chest' OF RECENT ONSET 2) Pain comes on less on exertion and more during rest 3) severity and frequency increases 4) a deterioration of stable angina

Question 47

What are the differences between stable angina, unstable angina and acute coronary syndrome in terms of the coronary lumen characteristics?

Answer 47

Stable Angina - atherosclerotic plaque that is partially occluding the lumen Unstable angina - atherosclerotic plaque has formed a fibrous cap, partially occluding THROMBUS STEMI - atherosclerotic plaque with fibrous cap, fully occluding thrombus

Question 48

What is the leading cause of death worldwide?

Answer 48

Atherothrombosis (MI, stroke, PaD)

Question 49

By how much does atherthrombosis reduce life expectancy in patients over 60 years old?

Answer 49

8-12 years

Question 50

How does clopidogrel work?

Answer 50

Clopidogrel and aspirin work synergistically. 1) Aspirin inhibits COX for forming thromboxane A2 2) Thromboxane A2 is unable to activate the membrane receptor. 3) ADP is not released. ADP that that is released from the receptor is competitive inhibited by clopidogrel 4) the fibrinogen receptor is not activated (Gb IIb, Gb IIIa)

Question 51

Atrial natriuretic peptide is released in response to... Hence it opposes... Thus it...

Answer 51

High blood pressure Aldosterone Descreases Na reabsorption in the distal convoluded tubule and collecting duct