Cardio Equations *

Question 1

CO =

Answer 1

SV x HR

• also: (MAP - Right atrial P) / TPR
• R atrial P = preload

Question 2

Ficke equation; CO =

Answer 2

rate of O2 consumption/ (arterial O2 cont. - venous O2 cont)

Question 3

MAP = (#1)

Answer 3

CO x TPR

Question 4

MAP = (#2)

Answer 4

2/3 diastolic pressure + 1/3 systolic pressure

Question 5

what does MAP give a measure of

Answer 5

afterload!

Question 6

pulse pressure =

Answer 6

systolic pressure - diastolic pressure

Question 7

what is pulse pressure proportional to?

Answer 7

stroke volume

Question 8

SV = (2 equations)

Answer 8

CO/ HR = EDV - ESV

Question 9

what two factors maintain HR in early exercise? Late exercise?

Answer 9

HR and SV increase initially, but SV can only increase so much, so eventually only HR is increasing to ↑ HR

Question 10

what happens to CO if HR gets too high

Answer 10

as HR ↑ diastolic filling is incomplete, so CO ↓

Question 11

two conditions that ↑ HR leads to ↓ CO

Answer 11

Ventricular tachycardia and atrial fibrillation

Question 12

What three variables affect SV

Answer 12

1. Contractility
2. Preload
3. Afterload

• ” SV CAP”

Question 13

Contractility (and SV) increase in what 3 changes?

Answer 13

1. Catecholamines (β1 agonism = ↑[Ca] intracell by stimulating SR release)
2. ↓ extracell Na+
3. Digitalis⇒ (blocks Na/K pump, leading to ↑ [Na] intracell; this ↓ action of Ca/Na pump that pumps Ca out of cell = ↑ intracell Ca

Question 14

Contractility (and SV) decrease in what 5 ways

Answer 14

1. β1 blockade (↓cAMP)
2. Heart failure (systolic dysfunction)
3. Acidosis
4. Hypoxemia/ Hypercapnia
5. Non-DHP CCB (verapamil)
   * also MI ( loss of myocardium)

Question 15

mycocardial O2 demand is increased when what 4 variables increase?

Answer 15

1. ↑ afterload (proportional to arterial pressure)
2. ↑ contractility
3. ↑ HR
4. ↑ heart size (↑ wall tension)

Question 16

Preload is roughly equal to what 3 other measures?

Answer 16

1. ventricular EDV
2. Right atrial pressure
3. Central venous pressure

Question 17

Afterload is equal to what

Answer 17

MAP (proportional to TPR)

Question 18

Venodilators decrease what? example of one

Answer 18

Preload (vEno = prEload)

• nitroglycerin is venodilator

Question 19

vasodilators (arterial) decrease what? example

Answer 19

afterload (vAso = Afterload)

• hydralazine is vasodilator

Question 20

preload increases in what 3 conditions

Answer 20

1. exercise (slightly)
2. ↑ blood volume (pregnancy, overtransfusion over hydration)
3. excitement (↑ sympathetic activity)

Question 21

what usually happens to CO or SV as preload (ventricular EDV) increases? (Starling curve)

Answer 21

usually increases in healthy individuals⇒ force of contraction is proportional to end-diastolic length of cardiac muscle fiber

Question 22

why can CO or SV increase even more during exercise with increasing preload than under normal conditions

Answer 22

sympathetic nerve stimulation⇒ β1 stimulation, which increase contractility and thus SV, leading to increased CO

Question 23

why does the CO or SV actually fall in CHF once preload gets past a certain point (starling curve rises, then begins to dip)

Answer 23

fluid overload⇒ overloads capacity of SV to increase anymore and past a certain point is actually counter-productive (drop in CO)
*CHF already have high preload to begin with (starling curve shifted to the right)

Question 24

what drug can be helpful in maintaining CO in CHF

Answer 24

digoxin ⇒ ↑ contractility, increasing SV

Question 25

EF = (2 forms of the equation)

Answer 25

(SV) / (EDF, or preload, RAP) = (EDV - ESV) / EDV

Question 26

what is EF an index of

Answer 26

ventricular contractility or function

Question 27

what is normal EF?

Answer 27

usually 55%- 75% (2/3 or 66% is a good approx.)

Question 28

when does EF decrease

Answer 28

systolic HF⇒ a failing heart has ↓ SV (numerator decreases)

Question 29

what 3 factors determine resistance

Answer 29

1. viscosity
2. length of vessel
3. radius of vessel

Question 30

what two factors are directly proportional to resistance

Answer 30

1. viscosity
2. length of vessel

• resistance increases when these do

Question 31

what factor is inversely proportional to resistance?

Answer 31

Radius⇒ 1/ R^4

• any decrease in vessel radius GREATLY increases resistance

Question 32

what are three conditions viscosity is increased (and therefore resistance)

Answer 32

1. polycythemia
2. hyperproteinemic states (multiple myeloma)
3. hereditary spherocytosis

Question 33

what does viscosity mostly depend on

Answer 33

hematocrit

Question 34

where does most of the regulation of resistance in vessels take place

Answer 34

arterioles

Question 35

vessels in an organ are arranged in series what does this mean for blood flow (Q) and pressure

Answer 35

blood flow is constant, from the aorta to the arteries to the veins–> what decreases is the pressure