ACE inhibitors

Question 1

What is the function of angiotensin 2?

Answer 1

• Angiotensin 2 is a potent vasocontrictor of precapillary arterioles and post-capillary venules
• Inhibits reuptake of norepinephrine (a1,a2,B1 agonist) = longer lasting effect
• stimulates release of catecholamines from adrenal medulla
• stimulates hypertophy of smooth muscle in blood vessels and cardiomyocytes

Question 2

What effect do ACE inhibitors have on angiotensin 2?

Answer 2

• ACE inhibitors stop breakdown of angiotensin 1 to 2
• lower arterial and venous blood pressure, reducing preload and afterload
• inhibits degradation of bradykinin (peptide involved in vasodilation)

Question 3

What is meant by preload and afterload?

Answer 3

Preload - the volume of blood present in the ventricles at the end of ventricular diastole (just before they contract in systole)

Afterload - the pressure the ventricles have to work against to open the semilunar valves of aorta/pulmonary artery. Eg, in aortic stenosis, valves are harder to open and get blood through, therefore greater pressure is need to push blood, increasing afterload

Question 4

What factors affect stroke volume?

Question 5

What factors affect stroke volume?

Question 6

What is digital substraction angiography?

Answer 6

• interventional radiological technique used to study blood vessels in bony or dense tissue environment
• pre-contrast image is subtracted from post-contrast image
• parts of two images that are different in the before and after images are shown in the final image

Question 7

Explain how digital substraction angiograph works?

Answer 7

1. take a mask image
2. take an opacification image (mask image + contrast agent is introduced)
3. perform a linear subtraction of images 1 and 2

This canbe used for time-series imaging; used when doing image-guided surgery

Question 8

How many contours of the heart are there in an X-ray image?

Answer 8

• 2 contours (left and right)

Left has 4 arches:
L arch 1 - aorta
L arch 2 - pulmonary artery/trunk
L arch 3 - left atrial auricle
L arch 4 - left ventricle
Right has 2 arches:
R arch 1 - superior vena cava + ascending portion of aorta
R arch 2 - right atrium

Question 9

How many forms of teh heart are there?

Answer 9

• ordinary
• mitral
• aortal
• trapezoid
• spherical