CVS 128 Chronic Stable Angina

Question 1

What is Angina?

Answer 1

Chest pain provoked by physical exertion, reversible ischaemia brought on my increased work load - subsides with rest

Question 2

Why does angina occur?

Answer 2

Due to increased oxygen demand of the myocardium which exceeds the supply

Question 3

How do you classify angina?

Answer 3

Stable - Class 1: predictable brought on by strenuous or protracted exercise
Class 2: slight limitation
Class 3: marked limitation
Unstable: unpredictable and should be treated as Acute Coronary Syndrome (ACS)

Question 4

With chest pain, what a more localised pain indicate?

Answer 4

That the origin was pleuritic or to do with the chest wall? Ischaemic chest pain is diffuse

Question 5

What are some causes of “chest pain” that may originate from below the diaphragm?

Answer 5

Acute cholecystitis radiating to right shoulder

Crushing pain through to bank think thoracic aorta

Question 6

Why is cocaine and nicotine a risk factor for ischaemic heart disease?

Answer 6

They cause coronary artery spasm

Question 7

How can you treat angina?

Answer 7

Treat and manage underlying disease/lifestyle
GTN spray
Beta blockers
Calcium channel blockers
Statins

Question 8

What is GTN?

Answer 8

glycerol trinitrate - fast acting vasodilator

Question 9

Why are beta blockers used to treat angina?

Answer 9

They reduce heart rate and contractility reducing work load

Question 10

What do calcium channel blockers cause?

Answer 10

Vasodilation

Question 11

What do statins do?

Answer 11

Inhibit cholesterol synthesis and encourage LDL uptake by the liver
Inhibit thrombosis - aspirin, clopidogrel

Question 12

What is Darcy’s Law?

Answer 12

Perfusion = pressure difference/ resistance

can only be applied to laminar flow

Question 13

What is Pouseille’s Law?

Answer 13

takes into account the resistance of a vessel

8 x viscosity x length / pi x radius^4

Question 14

What is resistance due to in blood vessels? Describe the fluid flow?

Answer 14

Friction between fluid layers moving at different speeds
No slip condition: outermost layer doesn’t move as it is in contact with the epithelium
Fluid layers is arranged in concentric layers from Slow –> Fast

Question 15

Where is viscosity of blood smallest? Why?

Answer 15

In the smallest vessels - due to axial streaming and bolus flow - the Fahraeus Lindqvist effect

Question 16

What is axial streaming in the blood stream?

Answer 16

Where RBC’s migrate to the centre of the lumen leaving a cell free zone near the wall where friction is the greatest - which acts as a lubricant layer
RBC’s move through the microcirculation faster than the plasma therefore the haematocrit is lower here and blood has decreased viscosity

Question 17

What is bolus flow in the blood stream?

Answer 17

Where the RBC diameter takes up the whole capilliary therefore “sweeps along” the plasma - so there is no slow moving plasma at the edge of vessels

Question 18

Why is viscosity of blood lower at high flow rates?

Answer 18

RBC aggregation and shear thinning. When shear forces are low (low flow) the RBC’s aggregate in rouleaux (increased viscosity) whereas in high shear these are thinner to allow free flow and movement of RBC’s

Question 19

What can a higher RBC count cause?

Answer 19

hypertension and heart failure

Question 20

What are the 3 ways of measuring blood flow?

Answer 20

Tissue clearance

Plethysmography and Ficks principle

Question 21

How do you measure tissue clearance?

Answer 21

Radioactive substance is injected into tissue and the time taken for the radioactivity to decline due to seepage into bloodstream is measured

Question 22

How do you measure blood flow using plethysmography?

Answer 22

Measures blood flow through a limb - pressure cuff used to occlude venous drainage only and initial swelling in limb is measured

Question 23

How do you measure blood flow using Fick’s Principle?

Answer 23

Measures blood flow through an organ - consituents of blood before and after passing through an organ are measured and compared to normal rates of increase/depletion of constituent organ

Question 24

Why is autoregulation important for the control of distribution of blood flow?

Answer 24

As it is necessary in organs that require a near constant flow e.g. brain and kidneys - used to stabilise against BP changes

Question 25

How does “active hyperaemia” control the distribution of blood flow?

Answer 25

It regulates local blood flow by how hard they’re working - the metabolic rate
It adjusts perfusion to demand and is controlled both intrinsically and extrinsically due to control of resistance vessels

Question 26

Where is resistance most in what arteries?

Answer 26

systemic arterioles - small change in diameter is a huge change in resistance and therefore BP

Question 27

What controls arteriole diameter?

Answer 27

Vascular smooth muscle contraction in response to various extrinsic and intrinsic factors
e.g. K+, CO2 and adenosine from respiration or NO from endothelium =vasodilation

Question 28

What is NO released in response to ? and why?

Answer 28

Shear forces in the endothelium increase NO secretion to dilate organs upstream with a metabolic need

Question 29

When are PG’s, histamine and bradykinin released and what is their function?

Answer 29

Released in response to damaged or inflamed tissue - act as vasodilators

Question 30

What are the extrinsic neuronal and hormone regulators of distribution of blood flow?

Answer 30

Vasomotor nerves (NA and AcH) and adrenalin and the RAAS system