NORMAL DOPPLER VALUES

Link to Normal Doppler Values Of Fetal Cardiac Function

1. Venous Circulation.
   Blood flow velocities may be recorded from the SVC, IVC or pulmonary veins. The IVC waveform's have been most closely studied and is measured from the segment of the vessel just distal to the entrance of the ductus venosus (1).
• Normal waveform
• Percentage of reversed flow (2). This is quantified as the percentage of time velocity interval during atrial contraction (reverse flow) with respect to total forward time velocity integral (first and second wave).
  This index relates the pressure gradient between the RA and RV during end diastole, which is a function of ventricular compliance and ventricular end diastolic pressure (3).
• In the ductus venosus the S/A ratio is used.
• Umbilical vein flow is continuous and devoid of pulsations after 12 gestational weeks.
2. Atrioventricular Valves.
   Flow velocity waveforms are recorded at the level of the mitral and tricuspid valves (just distal to the valve leaflets), and are characterized by two peaks. The E wave represents early ventricular filling, and the A wave represents atrial contraction. The E/A ratio is an index of ventricular diastolic function and is an expression of both cardiac compliance and preload (4,5). Normal E/A ratio.
3. Outflow Tracts.
   Peak velocities and time to peak velocities are the most commonly used indices in the aorta and pulmonary artery (6,7). Peak velocity is influenced by valve size, myocardial contractility and afterload, wheras time to peak velocity is affected by mean arterial pressure (8).
4. Ductus Arteriosus.
   Peak velocity or pulsatility index are measured (9).

REFERENCES

1. Rizzo G, Caforio L, Arduini D et.al. Effects of sampling site on inferior vena cava flow velocity waveforms. J Maternal Fetal Invest 1992;
2. Reed KL, Appleton CP, Anderson CF et.al. Doppler studies of vena cava flows in human fetuses - insights into normal and abnormal cardiac physiology. Circulation 1990;91:498-505.
3. Appleton CP, Hatle LK, Propp RL. Superior vena cava and hepatic vein doppler echocardiography in healthy adults. J Am Coll Cardiol 1987;10:1032-1039.
4. Stoddard MF, Pearson AC, Kern MJ et.al. Influence in alteration in preload of left ventricular diastolic filling as assessed by doppler echocardiography in humans. Circulation 1989;79:1226-1236.
5. Labovitz AJ, Pearson C. Evaluation of left ventricular diastolic function: clinical relevance and recent doppler echocardiographic insights. Am Heart J 1987;114:836-851.
6. Gardin JM. Doppler measurements of aortic blood velocity and acceleration: load independent indexes of left ventricular performance. Am J Cardiol 1989;64:935-936.
7. Bedotto JB, Eichorn EJ, Grayburn PA. Effects of left ventricular preload and afterload on ascending aortic blood velocity and acceleration in coronary artery disease. Am J Cardiol 1989;64:856-859.
8. Kitabatake A, Inoue M, Asao M et.al. Non invasive evaluation of pulmonary hypertension by a pulsed doppler technique. Circulation 1983;68:302-309.
9. Van de Mooren K, Barendregt LG, Wladimiroff J. Flow velocity waveforms in the human fetal ductus arteriosus during the normal second trimester of pregnancy. Pediatr Res 1991;30:487-490.