Intracardiac Shunt Calculations using the Fick Principle. Not all data needs to be entered. Calculations will be done based on available data.
Step 1:
Estimate Oxygen Consuption (VO2):
Enter the following for VO2 estimation:
height (cm)
weight (kg)
age (yrs)
heart rate (bpm)

Choose Gender:


Then click Calculate to Estimate VO2.
Estimated VO2: (ml/min)

Measured VO2: (ml/min)
(If this box is filled, the value will be used in calculations. If left blank, the estimated VO2 will be used instead)

Body Surface Area (BSA):
Calculated BSA: (m2)
(please enter height and weight above)

Indexed VO2: (ml/min/m2)

Examples: (select and click Calculate)
normal circulation
left to right shunt
right to left shunt
bidirectional shunt
CLEAR FORM
Step 2:
Oxygen Saturations (sat):
Enter values for the following:
SVC sat (%)
IVC sat (%)
PA sat (%)
PV sat (%)
Ao sat (%)
Hgb (g/dl)

Step 3: Choose method to estimate
Mixed Venous sat (MV):

Resulting MVsat: (%)

Step 4:
Pressures (for resistance only)
mean RA (mmHg)
mean PA (mmHg)
mean LA (mmHg)
mean Ao (mmHg)

Step 5:


Use Supplemental Oxygen

Clear Form

RESULTS
Flows (Q):
Qpulmonic (L/min)
Qsystemic (L/min)
Qef (L/min)

Shunts:
R-->L shunt (L/min)
L-->R shunt (L/min)
Qp/Qs ratio
Systemic shunt fraction
Pulmonic shunt fraction

Cardiac Index (CI):
Pulmonic CI(L/min/m2)
Systemic CI (L/min/m2)
Effective CI (L/min/m2)

Resistance (PVR/SVR):
PVR (wood units, indexed= u-m2)
PVR (dynes/sec/cm-5)
SVR (wood units, indexed= u-m2)
SVR (dynes/sec/cm-5)

Stroke Volume/Index (SVI):(Will only calculate if shunt volume is less than 0.5 L/min)
Pulmonic:(ml/beat) (ml/beat/m2)
Systemic:(ml/beat) (ml/beat/m2)

Definitions: VO2=oxygen consumption; BSA=body surface area; SVC=superior vena cava; IVC=inferior vena cava; PA=pulmonary artery; PV=pulmonary vein; Ao=aorta; Hgb=haemoglobin; MV=mixed venous; RA=right atrial; LA=left atrial; Qp=flow to pulmonic circulation; Qs=flow to systemic circulation; Qeffective=effective flow, ie from systemic capillary bed to pulmonic capillary bed; CI=cardiac index PVR=pulmonary vascular resistance; SVR=systemic vascular resistance; SVI=stroke volume index.

Formulae:
  1. BSA = ((height x weight)/3600)1/2 (Mosteller formula, NEJM,317(17):1098,1987) See Other Methods
  2. Estimated VO2 (female) = BSA x [138.1 – 17.04 x ln(age) + 0.378 x HR] (reference 8)
  3. Estimated VO2 (male) = BSA x [138.1 – 11.49x ln(age) + 0.378 x HR]
  4. O2capacity = Hgb (g/dl) x 1.36 (ml/g) x 10 (dl/L) = ml/L
  5. Note: Literature varies on oxygen binding coefficient. 1.34, 1.36, and 1.39 ml/g have all been published.
  6. Qpulmonic = VO2/[O2capacity x (PVsat – PAsat) / 100]
  7. Qsystemic = VO2/[O2capacity x (Aosat – MVsat) / 100]
  8. Qeffective = VO2/[O2capacity x (PVsat – MVsat) / 100]
  9. R-->L shunt = Qsystemic - Qeffective
  10. L-->R shunt = Qpulmonic - Qeffective
  11. Qp/Qs = (Aosat – MVsat)/(PVsat – PAsat)
  12. Pulm shunt fraction = (PAsat – MVsat)/(PVsat – MVsat)
  13. Syst shunt fraction = (PVsat – Aosat)/(PVsat – MVsat)
  14. Cardiac Index = Flow/BSA
  15. PVR = (PApressure - PVpressure)/Qpulm (multiply by 80 to convert woods units to dynes/sec/cm-5)
  16. SVR = (Aopressure - MVpressure)/Qsyst (multiply by 80 to convert woods units to dynes/sec/cm-5)
  17. Stroke Volume = Flow/HR (only meaningful if no significant shunt or regurgitation present)
  18. Stroke Volume index = SV/BSA
Selected References:
  1. Hillis LD, Winniford MD, Jackson JA, Firth BG. Measurements of left-to-right intracardiac shunting in adults: oximetric versus indicator dilution techniques. Cathet Cardiovasc Diagn 1985; 11:467-72.
  2. Flamm MD, Cohn KE, Hancock EW. Ventricular function in atrial septal defect. Am J Med 1970; 48:286-94.
  3. French WJ, Chang P, Forsythe S, Criley JM. Estimation of mixed venous oxygen saturation. Cathet Cardiovasc Diagn 1983; 9:25-31.
  4. Pirwitz MJ, Willard JE, Landau C, Hillis LD, Lange RA. A critical reappraisal of the oximetric assessment of intracardiac left-to-right shunting in adults. Am Heart J 1997; 133:413-7.
  5. Iga K, Izumi C, Matsumura M, et al. Partial pressure of oxygen is lower in the left upper pulmonary vein than in the right in adults with atrial septal defect: difference in P(O2) between the right and left pulmonary veins. Chest 1999; 115:679-83.
  6. Cigarroa RG, Lange RA, Hillis LD. Oximetric quantitation of intracardiac left-to-right shunting: limitations of the Qp/Qs ratio. Am J Cardiol 1989; 64:246-7.
  7. Shepherd AP, Steinke JM, McMahan CA. Effect of oximetry error on the diagnostic value of the Qp/Qs ratio. Int J Cardiol 1997; 61:247-59.
  8. LaFarge CG, Miettinen OS. The estimation of oxygen consumption. Cardiovasc Res 1970; 4:23-30.
  9. Wilkinson JL. Haemodynamic calculations in the catheter laboratory. Heart, 2001; 85:113-120.


Written by Craig S. Broberg, MD
Suggestions, Errors, Comments Welcome!
webadmin@rbht.nhs.uk
Adult Congenital Heart Disease Unit
Royal Brompton & Harefield NHS Foundation Trust
Sydney Street, London, SW3 6NP
United Kingdom
Authors not responsible for clinical decisions based on this website