Cardiac Cycle

Question 1

how many pumps are there in the heart and how do they work?

what circulation results in high/low pressure?

Answer 1

• 2 acting in series
• high = systemic
• low = pulmonary

Question 2

what type of muscle is the heart?

whats special about the cellular arrangement?

whats the duration of a cardiac AP?

Answer 2

• striated cardiac muscle, made up of myocytes that are interconnected electrically with each other
• 280ms

Question 3

what are the valves of the heart?

why do they open?

what are they attatched to?

Answer 3

• tricuspid , mitral (bicuspid) , pulmonary , aortic
• due to pressure differences from artia/ ventricles or ventricles/PA/Aorta
• attached to papillary muscle via chordae tendinae which prevents the prolapse of the valve upon high pressure

Question 4

what are the main cells in the conduction system and describe how they cause conduction steps that results in contraction?

Answer 4

• pacemaker cells in the SAN generate the AP across the atria - resulting in atrial systole
• , which reaches the AVN,
• from AVN spreads down the septum between the ventricles then through the ventricular myocardium from inner (endocardial) to outer (epicardial) surface causing ventricle contraction from the apex upwards forcing the blood through th valves

Question 5

7 phases of the cardiac cycle?

Answer 5

1) atrial contraction
2) isovolumetric contraction
3) rapid ejection
4) rejected ejection
5) isovolumetric relaxation
6) rapid filling
7) reduced filling

Question 6

plot a ‘x’ diagram

what does x mean?

for what side of the heart is it usually plotted?

Answer 6

image

wiggers diagram

left side , it can be plotted for the right but at lower pressures

Question 7

phase 1

Answer 7

atrial contraction

A wave. d ^ in atrial pressur d atrial systole (atrial pressure graph)

at the end we reach EDV

• small increase in pressure due to atria contracting to push that final little bit of blood out ,
• M and T valves open and filling is passive except for the last 10%
• P wave in ECG (volume) signifies the onset of atrial depolarisation

Question 8

phase 2

Answer 8

isovolumetric contraction

• M valve closes as intraventricular pressure increases atrial pressure
• rapid rise in pressure as the ventricles contract
• closing of mitral valve = C wave on pressure curve
• on ECG (volume) QRS complex forms and signifies the onset of ventrcular depolarisation
• closure of M + Tvalve = ‘lub’ sound 1
• no change in the ventricular volume because the valves are closed

Question 9

phase 3

Answer 9

rapid ejection

ventricular contraction increases pressure so higher pressure in the V than A = aortic valve opens and blood ejected through it

• in artial pressure graph the pressure decreases = ‘X DESCENT’ because the ventricular contraction pulls the atria downwards
• aortic valve open

Question 10

phase 4

Answer 10

reduced ejection

pressure in the A rises higher than ventricule

• same time atria filling up d continous venous return from lungs so gradual increasein pressure of atria = V wave
• T wave in the ECG depicts ventricular repolarisation
• aortic valves open

Question 11

phase 6

Answer 11

• isovolumetric relaxation

close A valve when intraventricuar pressure falls below aortic pressure, theres a backflow of blood wc causes the aortic valve to close = dicrotic notch causing slight increase in pressure

• rapid decreae in ventricular pressure , but volume constant as all values closed =isovolumetric relaxation
• ESV = minimum blood the ventricles can hold since not 100% blodd ejected from v to a
• closure of the A and p valve cause the second heart sound

Question 12

phase 6

Answer 12

rapid filling-

decrease in A pressure after opening of M valve =’ Y descent”

• when intraventricular pressure is lower than atrial pressure the mitral valve opens and b starts filling the ventricles rapidly
• sound 3 can be heard a little in kids is normal due to the b going from atria to ventricle, but in adults sound heard = pathological issue

mitral valve open

Question 13

phase 7

Answer 13

• reduced filling

rateof filling slows down diastasis as ventricle reaches its inherent relaxed volume, further filling is driven by venous pressure

• at rest 90% filled ventrice
• mtiral valve isopen

Question 14

2 abnormal valve functions and causes

Answer 14

• STENOSIS = valve doesnt open enough , obstruction to blood flow when valve normally open
• REGURGITATION (imcompetence/insufficiency) valve doesnt close all the way, back leakage when valve should be closed

Question 15

size of normal valve and the size requirements for stenosis?

causes of aortic valve stenosis

what does this result in?

sound

Answer 15

• N= 3-4 cm2. S = <1cm2
• degenerative (senile/calcificaition fibrosis/ vegetation)
• congenital ( bicuspid form valve instead of tricupsid)
• chronic rheumatic fever - from Strep.A group c inflammation can get autoimmune response where own antibodies attack the structure of the valve
• less blood can get through valve so;

increased LV pressure = LV hypertrophy / left sided heart failure = syncope / angina

or sheer stress of the RBC being pumped at high pressure can cause haemolysis resulting in MICROANGIOPATHIC HAEMOLYTIC ANAEMIA

• crescendo-decrescendo murmur after S2

Question 16

causes of aortic valve regurgitation

what does this result in?

sound?

Answer 16

• aortic root dilation (leaflets pulled apart)-
• valvular damage due to endocarditis rheumatic fever
• blood flows back into LV during diastole
• increase in stroke volume
• systolic pressure increases
• diastlic pressure decreases
• bounding pulse is found in these patients / QUINKE’S SIGN = pulsation in the nail bed/ changing colour with the pulsationsof the nail bed
• LV hypertrophy

- early decrescendo diastolic murmur

Question 17

mitral valve regurgitation

Answer 17

• chordae tendinae + papillary muscles weakened due to MYXOMATOUS DEGENERATION causing prolapse so blood leakage into LA
• or other weakenesed of = papillarymuscle weakening post MI, left sided heart failure leads to LV diation which can stretch valve / rheumatic fever can lead to leaflet fibrosis which distrupts seal formation
• blood leaks back into LA causing increase in preload resulting in more blood entering in subsequent cycle = LV hypertrophy
• holosystolic murmur

Question 18

mitral valve stenosis cause?

describe the mechanism by which this may cause damage?

sounds heard when?

Answer 18

• rheumatic fever (99.9%) cases
• comissural fusion of valve leaflets so harder for blood to flow LA to LV which causes increased LA pressure;
• causes pulmonary oedema because due to increased LA pressure blood is pushed into veins resulting in an increase in VP which pushes fluid out into the air spaces (alveoli) of the lungs
• dyspnea shorteness of breath
• pulmonary hypertension (^BP in the pulomary blood vessels

this all above cause RV hypertrophy

• LA dilation can cause atrial fibrillation = thrombus formuation / osephagus compression = dysphagia
• snapping sound sound heard after the first S1

Question 19

narrow pulse pressure?

Answer 19

aortic stenosis

Question 20

Quinke’ sign?

Answer 20

aortic regurgitation

beds of the nail changing colour

Question 21

bounding pulse

Answer 21

aortic regurgitation

Question 22

Murmur loud upon inspiration

Answer 22

right sided valve lesion

Question 23

murmur louder with patient in lateral position

Answer 23

mitral regurgitation

Question 24

rigth side 2nd intercostal space

Answer 24

aortic valve

Question 25

corrigan's sign?

Answer 25

exaggerated pulsations aortic regurgitation sign

Question 26

NICE guidelines for suspected MI

Answer 26

in ambulance admininster 300 mg of aspirin if allergic anaphylactic when get to hospital GTN spray and ECG if still in pain Morphine clopidgrel is given as monotherapy for patients with aspirin allergy later on