Concept of cardiac preload

Question 1

what is CO

Answer 1

volume of blood eject (SV) of the heart/min

CO=stroke volume (SV) x HR

Question 2

what is end diastolic volume

Answer 2

When heart relax = time where blood filled with blood (Diastole) -> End diastolic volume (EDV): amount of blood that will maximally filled the heart at the end of the relaxation -> average 130 ml

Question 3

what is end systolic volume

Answer 3

When heart contract = blood is pushed out to the artery (systole)
At the end of systole -> we still have a little amount of blood remaining in = End systolic -> average 60 ml

Question 4

what is cardiac preload

Answer 4

ventricular wall stress at end of diastole

blonde enter the heart, the wall of the heart will stretch to maximally load the heart -> at end of the filling, the amount of stretching = preload

Question 5

T/F preload is directly related to amount of blood that being ejected

Answer 5

T

Question 6

What affected preload

Answer 6

venous pressure and rate of venous return
artrial contraction
resistance from valve
ventricular compliance
heart rate

Question 7

impact of vasodilatation and vasoconstriction on preload

Answer 7

vasoconstriction: decrease venous tone = decrease venous return = decrease EDV = decrease CO = decrease preload

Vasodilatation= increase vascular tone of vein = increase venous return = increase EDV = increase cardiac preload

Question 8

impact of atrial contraction on preload

Answer 8

Increase force = increase blood filling= increase EDV= preload

Question 9

impact of ventricular compliance on cardiac preload

Answer 9

Compliance of the heart the stretch -> increase compliance = heart stretch more = increase preload like in dilated cardiomyopathy

Ventricular hypertrophy = increase stiffness to the heart = decrease stretch = decrease preload

Question 10

impact of high heart rate on cardiac preload

Answer 10

Fast heart rate like in tachycardia, reduce the time for the filling of the heart = decrease preload

Question 11

what is frank-starling mechanism

Answer 11

• The more you stretch the heart, the greater the reflex of the heart ejecting the blood will be -> higher preload = increase in frank-sterling mechanism = increase amount of blood ejecting (greater heart contraction)

Question 12

what is cardiac after load

Answer 12

• Amount of resistance or force need to overcome in order to eject blood out of the heart
• Ventricular wall stress during systole (ejection of blood)

Question 13

what is after load of left and right ventricle

Answer 13

• Afterload to left ventricle= aortic arterial pressure
• Afterload of right ventricle = pulmonary arterial pressure

Question 14

what affected cardiac after load

Answer 14

systemic vascular resistance
aortic pressure
valve disease

Question 15

role of system resistance in cardiac afterload

Answer 15

How blood vessel allow blood to flow through them

Vasodilation: widen vessel lumen by relaxing smooth muscle = decrease resistance = decrease afterload

Vasoconstriction: decrease vessel lumen = increase resistance = increase afterload

Question 16

role of aortic pressures in cardiac after load

Answer 16

Increase aortic pressure = heart need to work harder + generate more pressure in left ventricle to open aortic valve
Increase AP = increase afterload
Decrease AP = decrease afterload

Question 17

role of valve disease in cardiac after load

Answer 17

Aortic stenosis = aortic valve can’t open all the way = heart need to generate more pressure to eject blood = stress on ventricular wall = increase afterload
Mitral regurgitation= valve between atrium and ventricle doesn’t close all the way = blood leak back to left atrium during ejection = decrease stress on ventricular wall = decrease afterload

Question 18

when doing valsava maneuver what happen with preload

Answer 18

decrease venous return = decrease cardiac preload

Question 19

during pregnancy, what happen with cardiac preload

Answer 19

thoracic vena cava is compressed = decreased venous return = decrease preload

Question 20

after a meal, what happen with cardiac preload

Answer 20

increase venous return = increase cardiac preload

Question 21

preload occurs during systole or diastole

Answer 21

diastole

Question 22

cardiac after load occurs during systole or diastole

Answer 22

systole