Cardiovascular Calculations Flashcards
What does LVEF stand for?
Left ventricular ejection fraction
LVEF equations
- (EDV-ESV)/EDV x 100
- SV/EDV x 100
Normal LVEF
55-60%
Normal EDV
110-120 ml
Normal ESV
40-50 ml
Normal SV
70 ml
Cardiac output equations
CO= Arterial pressure/ Total peripheral resistance
CO= SV X HR
Normal cardiac output
Men: 5.7 L/ min
Women= 4.9 L/ min
Cardiac index
CO per square meter of body surface area
*Normal is 3L/ min/m2 of BSA
CO with Fick
CO= [O2 absorbed per minute by lungs (mL/min)]/ [Arteriovenous O2 difference (mL/L of blood)]
- O2 consumption can be measured or assumed to be 125 ml/min/m2
- Arterial venous O2 contents need to be calculated
- Mixed venous O2 content needs to be determined
Calculation of arterial and venous O2 contents
Systemic cardiac output
Determining mixed venous O2 Content
What are the advantages and disadvantages to Fick?
Advantages
- Most accurate method if the heart rate or rhythm is irregular such as AFIB
- Most accurate for low flow states
Disadvantages
- Cannot detect rapid changes in cardiac output
- Requires simultaneous measurements
Continuity equation
Q1= Q2
v1xA1= v2 x A2
Modified Bernoulli equation
4(V)2
Needed values:
- Peak velocity across the valve for the gradient
- The gradient is used to calculate the valve area
- Stenotic lesions such as aortic stenosis
*Represent maximal instant gradient
LVOT Area
(D/2)2
D= Diameter
The Bernoulli equation
Gorlin’s formula: Aortic valve area
Simplified Gorlin for Aortica valve area
AVA= (CO)/ (square root of the peak to peak gradient)
Systolic Ejection Period
What are the limitations of AVA calculations?
- Limitations in pressure measurement, especially if pulmonary capillary wedge pressure replaces left atrial pressure or if femoral artery pressure replaces aortic pressure
- Valve area itself can be dependent on flow and pressure- “dynamic area?”
Arterial ____ is used clinically. Arterial _____ is used in laboratory investigations.
Resistance; impedence
Vascular resistance *pulmonary
(Mean pulmonary artery pressure- left atrial pressure)/ Left-sided cardiac output
NOTE: Systemic vascular resistnace is calculated the same way but wth the right atrial presure and mean aortic pressure
Units for Vascular resistance
Wood unit: mmHg (1/min)
1 wood unit= 80dynes.s.cm-5
Normal pulmonary arterial restistance
67 dynes.s.cm-5
Normal total pulmonary resistance
205 dynes.s.cm-5
Normal systemic resistance
1,130 dynes.s.cm-5
In the absence of a shunt what is the relationship between systemic and pulmonary flow?
Qp=Qs
- In the setting of left to right shunt Qp> Qs
- In the setting of right to left shunt Qs> Qp
What do you notice observing oxygen saturation profile in the figure?
- There is an oxygen saturation “step-up” in the right atrium
- This patient has an atrial septal defect
What are normal oxygen saturation levels in the compartments of the heart?
