Cardiac Haemodynamics

Question 1

what is the most likely diagnosis of an elderly woman which becomes breathless and cannot lie flat with lower O2 sat and respiration is fats and shallow

Answer 1

pulmonary oedema - fluid in the lungs - seen as white areas - usually at the bottom of the lungs

Question 2

what is the basic structure of skeletal muscle in the heart

Answer 2

each muscle fibre is made up of individual myofibrils which contain rows of adjacent sarcomeres
actin and myosin filament overlap and this shortens the row of sarcomeres

Question 3

what initiates heart contraction

Answer 3

calcium binds to troponin which induces conformational change in troponin-tropomyosin complex
exposes binding sites of actin

Question 4

describe the power stroke in the heart

Answer 4

myosin beds can bind once Ca influx has occurred - then ATP is required for binding - initiates power stroke and pulling

Question 5

how much ATP do myocardial cells use up

Answer 5

6kg per day

Question 6

what does the use of ATP do in myocardial cells

Answer 6

force generation
myofilamant shortening
transforms basic mechanical energy into useful hydraulic function

Question 7

which directions does the heart contract

Answer 7

longitudinal, horizontal, twisting - torson

Question 8

what did william harvey discover

Answer 8

circulation

Question 9

what causes higher demand on the heart

Answer 9

exercise
incurrent illness
fluid overload
pregnancy - almost doubles

Question 10

what is cardiac functional reserve

Answer 10

the capacity to augment performance on demand

Question 11

how do you calculate cardiac reserve

Answer 11

maximal cardiac output - cardiac output at rest

Question 12

what is the difference n CO at rest compared to during exercise

Answer 12

5 l/min

20 l/min

Question 13

what is cardiac reserve innervated by to affect HR

Answer 13

sympathetic innervation
speeds up SAN depolarisation = more AP - increases conduction through AVN and bundle
also by adrenaline - B1 agonism

Question 14

how can we augment stoke volume

Answer 14

sympathetic stimulation
prolonged ca channel opening enhances muscle contraction
also depends on preload

Question 15

what happens if there is too much stretch in sarcomere

Answer 15

then there is less tension and less contraction - in the graph you always want to be on the left side down slope

Question 16

how does sarcomere length affect tension

Answer 16

small changes in sarcomere length cause large changes in tension - normally stretching the LV will aid contraction

Question 17

what determines stretch of the LV

Answer 17

EDV - greater the preload the greater the cardiac performance

Question 18

what is the starling law of the heart

Answer 18

the energy of contraction is a function of the length of the muscle fibre

Question 19

what happens to contraction if preload is decreased

Answer 19

reduced muscle contraction

Question 20

what causes shifts in the frank starling graph

Answer 20

left shift - exercise, pharmacological stimulation

right shift - pharmacological depression and myocardial loss

Question 21

what does a decrease or increase in after load look like in a frank starling graph

Answer 21

decreased after load shift up and left

increased after load in down and right

Question 22

what happens to the frank starling curve with sympathetic stimulation and why

Answer 22

shift to the left and NA and A stimulate cAMP so more Ca enter and greater cross bridge linking in sarcomeres

Question 23

how do you calculate ejection fraction

Answer 23

stroke volume / EDV

Question 24

what is physiological Ef and what is it during exercise

Answer 24

55-75%

90% in exercise

Question 25

what does high BP do to after load

Answer 25

increases it

Question 26

what happens to CO in heart failure

Answer 26

ischeamia - scarred myocardium - less movement of walls
wall thinning due to infection
increased after-load - chronic high output

Question 27

if there is too much preload and too much stretch to sarcomeres

Answer 27

move to the right downward line on the sarcomere graph and shift to the right in frank starling graph

Question 28

if there was failing LV and fluid entering then lungs how would you resolve this

Answer 28

give o2
morphine to relax pulmonary vessels - reduce preload and take strain of LV - also reduce pain
furosemide - take fluid out of lungs, reduce preload