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Flashcards in Determinants and Cardiac basics Deck (100)
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1

Determinants of Cardiac Output

Heart and Stroke Volume

2

What is SV?

SV is the amount of blood ejected by the ventricle with each contraction.

3

Preload is the

precontractile fiber length of myocardial fiber augmented

4

Preload can be augmented by

End diastolic volume

5

Venous return is directly proportional to

EDV

6

Some factors that affect venous return

Factors that affect venous return include blood volume, venous tone, intrathoracic pressure, pulmonary vascular resistance, and right heart function

7

What is afterload?

Afterload, the force against heart contraction,

8

What are the 3 determinants of afterload?

Ventricular wall stress
Systemic vascular resistance
Blood viscosity.

9

Afterload and SV relationship is

Inversely proportional; As afterload increases, SV decreases.

10

Contractility is the

intrinsic ability of the myocardial fiber to contract.

11

What is the main role of Intracellular calcium

main mechanism which influences the binding strength of actin and myosin filaments that determine the force of myocardial contraction

12

Cardiac output (CO) is the

amount of blood delivered to the tissue in 1 min.

13

Starling’s law

The stronger the stretch, the greater output

14

Normal CO

5-6L/min

15

What is CI ?

CO/BSA

16

Normal CI

2.5 to 3.5⋅L⋅min−1⋅m−2

17

CO formula is

HR x SV

18

What is the primary determinant of HR?

the rate of phase 4 depolarization of the SA node of pacemaker cells

19

Rate of discharge of SA node is a determinant of HR and determined by

humoral and neural (Epi, NE) mechanisms

20

In children how is the CO determinants different?

the myocardium is less contractile and less compliant; therefore HR is critically important for maintenance of CO

21

How does significant tachycardia affect CO?

significant tachycardia can negatively affect CO because increased HR (> 170 beats/min) disproportionately decreases diastolic ventricular filling time relative to decreases in systole, which then contributes to a lower CO.

22

Heart rhythm also is an important determinant of cardiac output because the atrial contraction inherent in sinus rhythm contributes of _______CO in normal hearts and up to in the case of reduced ventricular compliance or delayed relaxation.

20% to 25%; 40% to 50%

23

What is a normal SV?

70-80ml per contraction

24

What are determinants of SV?

Preload, afterload and contractility. and SOMETIMES 4th wall motion abnormalities

25

What is the formula of SV?

EDV - ESV

26

What are the determinants of EDV?

Preload

27

What are the determinants of ESV?

Afterload and contractility

28

3 determinants of Preload

Venous return
Ventricular filling time
Intrathoracic pressure

29

3 determinants of Afterload?

SVR
Wall tension
Blood viscosity

30

2 determinants of contractility

Sympathetic nervous system
Catecholamines drugs.