Important CV Equations

Question 1

Flow

Answer 1

Q = Δ P / R
MAP/SVR

Question 2

Cardiac Output

Answer 2

CO = HR x SV
Blood volume that ejects from the heart each minute
Dependent on preload, afterload, & contractility
Reference adult value = 4-8 L/min

Question 3

Cardiac Index

Answer 3

CI = CO / BSA
= (HR x SV) / BSA
Reference adult value = 2.8-4.2 L/min/m^2

Question 4

Stroke Volume

Answer 4

SV = (CO x 1000) / HR
OR
= EDV - ESV
Blood volume ejected from the ventricle in one heart beat
Reference adult value = 50-110 mL/beat

Question 5

Systemic Vascular Resistance

Answer 5

SVR = [(MAP - CVP) / CO] x 80
Resistance blood meets across the entire circulation
1° determinant LV afterload
Reference adult value = 800-1500 dynes/sec/cm

Question 6

Ejection Fraction

Answer 6

EF = [(EDV - ESV) / EDV] x 100%
= (SV / EDV) x 100
Blood amount that exits the ventricle after one systolic contraction
Reference adult value = 60-70%

Question 7

Blood Pressure

Answer 7

BP = CO x SVR
= HR x SV x SVR

Question 8

Mean Arterial Blood Pressure

Answer 8

MAP = [SBP + (DBP x 2)] / 3
OR
MAP = [(CO x SVR) / 80] + CVP
Average arterial pressure throughout the cardiac cycle, used to estimate perfusion pressure throughout the body
Cardiac cycle 1/3 systole & 2/3 diastole
Reference adult value = 70-105 mmHg

Question 9

Pulse Pressure

Answer 9

PP = SBP - DBP
= SV output / arterial compliance
L ventricle SV, blood flow velocity, & arterial compliance
↑pulse pressure d/t aging ↓arterial compliance, aortic regurgitation, & along the arterial tree (lowest in the aortic & higher in dorsalis pedis)
Reference adult value = 40-60 mmHg

Question 10

Afterload

Answer 10

= Wall tension / thickness

(LVP x chamber radius) / cardiomyocyte wall thickness

Question 11

CorrPP

Answer 11

= ADBP - LVEDP (or PAOP)
Driving CBF pressure
CBF autoregulates MAP 60-140 mmHg

Question 12

Coronary Blood Flow

Answer 12

= CorrPP / coronary artery resistance

Question 13

What impacts demand?

Answer 13

Preload
Afterload
Contractility
Heart rate

Question 14

Cardiac Workload α

Answer 14

Cardiac output
LVP
Preload (volume)
Frank-Starling

Question 15

What factors impact LVEDP?

Answer 15

L ventricle end diastolic pressure
- LV volume
- LV compliance
- External pressure

Question 16

What factors impact LVP?

Answer 16

= LVSP
Systolic ejection α afterload
1. ADBP
2. Chamber radius
3. Outflow tract diameter
4. Wall thickness (inversely proportional)

Impacts coronary artery demand

Question 17

What factors impact ADBP?

Answer 17

1. SVR
2. Volume (SV/CO)
3. Peripheral run-off

Question 18

O2 Supply

Answer 18

= CaO2 x CO = O2 delivery

Question 19

O2 Carrying Capacity

Answer 19

CaO2 = (Hgb x SaO2 x 1.34) + (PaO2 x 0.003)
How much oxygen contained in arterial blood (O2 bound to Hgb + O2 dissolved in the plasma)
Reference adult value = 20 mL O2/dL

Question 20

Venous Oxygen Content

Answer 20

CvO2 = (Hgb x SvO2 x 1.34) + (PvO2 x 0.003)
Reference adult value = 15 mL O2/dL

Question 21

O2 Delivery

Answer 21

DO2 = [(Hgb x SaO2 x 1.34) + (PaO2 x 0.003)] x CO x 10
= CaO2 x CO x 10 (conversion factor dL→L)
How much O2 in the blood & how fast O2 delivered to the tissues (based on CO)
Reference adult value = 1,000 mL O2/min

Question 22

Oxygen Consumption

Answer 22

VO2 = CO x (CaO2 - CvO2) x 10
250 mL/min or 3.5 mL/kg/min

Question 23

Oxygen Extraction Ratio

Answer 23

EO2 = (CaO2 - CvO2) / CaO2
25%

Question 24

Maximum Allowable Blood Loss

Answer 24

ABL = EBV x [(starting Hgb - allowable Hgb) / starting Hgb]
Estimates how much blood patient able to lose before considering a transfusion

Question 25

Cerebral Perfusion Pressure

Answer 25

CPP = MAP - ICP (or CVP)
Pressure gradient b/w systemic circulation & cranium
Brain autoregulates CBF to maintain pressures 50-150 mmHg
*Range varies based on patient-to-patient

Question 26

Anion Gap

Answer 26

= Na+ - Cl¯ + HCO3¯
Gap acidosis → acid accumulation
Non-gap acidosis → loss bicarbonate or ECF dilution
Reference adult value = 8-12 mEq/L

Question 27

Plasma Osmolarity

Answer 27

= 2[Na+] + (glucose / 18) + (BUN / 2.8)
Measures hydration status
Reference adult value = 280-290 mOsm/L

Question 28

Normal Hgb

Answer 28

Male 15 g/dL
Female 13 g /dL

Question 29

Normal Hct

Answer 29

Male
Female

Question 30

Ohm’s Law

Answer 30

Flow = Pressure gradient / Resistance
Q = ΔP / R

Q = CO
ΔP = MAP - CVP
R = SVR

Question 31

Poiseuille’s Law

Answer 31

Q = (π ⋅ r^4 ⋅ ΔP) / (8 ⋅ η ⋅ l)

Q = blood flow
r = radius
ΔP = pressure gradient
η = viscosity
l = length