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2015 GUIDELINES Source

  • Lang RM, Badano LP, Mor-Avi V, et al. Recommendations for cardiac chamber quantification by echocardiography in adults. Eur Heart J Cardiovasc Imaging. 2015;16:233–270.

  • Echocardiographic measurements are standardized and extensively illustrated.

  • Normal values are provided.

  • Calculations are explained.

  • The right ventricle is included.

  • Measurement criteria of the proximal ascending aorta are illustrated.

DOPPLER CALCULATIONS

  • Stroke volume is calculated as the volume of a cylinder.

  • The volume of a cylinder is calculated as the area of the base × height.

  • Example: Left ventricular outflow stroke volume = LVOT area × LVOT VTI.

  • LVOT VTI is the stroke distance (cylinder height).

  • Stroke volume × heart rate = cardiac output.

  • Stroke volume = end-diastolic volume × ejection fraction.

  • Cardiac output = heart rate × stroke volume.

  • Cardiac output = heart rate × end-diastolic volume × ejection fraction.

  • Corollary:

    • - Cardiac output is affected by changes in heart rate, by end diastolic volume (preload), and by ejection fraction.

    • - Practical clinical value: 2D echo provides a look at the impact of preload in patients with Doppler evidence of constriction, restriction, etc., by showing right and left ventricular end-diastolic volumes.

Source

  • Hurrell DG, Nishimura RA, Ilstrup DM, et al. Utility of preload alteration in assessment of left ventricular filling pressure by Doppler echocardiography: a simultaneous catheterization and Doppler echocardiographic study. J Am Coll Cardiol. 1997;30:459–467.

CARDIAC OUTPUT IN THE CATH LAB

Fick versus Thermodilution

  • The Fick method uses the a-v O2 difference. It works in atrial fibrillation because “steady state” is used. It is most accurate in low-output states where there is a wide a-v O2 difference. Oxygen extraction is greater with decreased cardiac output. This results in a low pulmonary artery saturation. Pulmonary artery saturation <65% indicates decreased cardiac output.

  • Thermodilution measures the “area under the curve” after a short set of cardiac cycles. It is less reliable in low-output states. The calculation is affected by significant tricuspid regurgitation, and possibly by the variable cardiac cycle length in atrial fibrillation.

Source

  • Gonzalez J, Delafosse C, Fartoukh M, et al. Comparison of bedside measurement of cardiac output with the thermodilution method and the Fick method in mechanically ventilated patients. Crit Care. 2003;7:171–178.

DERIVATIONS FROM STROKE VOLUME CALCULATIONS

  • Aortic stenosis area calculation by continuity:

    • - Because of flow continuity and conservation of mass: Stroke volume is the same below the stenotic aortic valve and the same at the stenosis.

    • - In other words, the stroke volume “cylinder” simply changes from “short and fat” to “long and thin.”

    • - The volume of both cylinders is identical.

  • The two cylinders have a total of four components.

  • If three components are known, it is possible to use a simple formula to solve for the fourth unknown component.

    Example: Calculation of ...

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