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PULMONARY VEINS |
The accurate identification of the normal pulmonary venous connections to the left atrium may be difficult to detect antenatally. It is however important to confirm normal pulmonary venous return to the left atrium as fetuses with aberrant drainage rapidly deteriorate postnatally with severe respiratory distress and cyanosis.
Four pulmonary veins enter the left atrium. It is probably only necessary to identify one or two of the pulmonary veins as this excludes total anomalous pulmonary venous drainage (partial anomalous pulmonary venous drainage has no real hemodynamic consequences).
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· It is important to differentiate the pulmonary veins from peripheral branches of the pulmonary arteries but assessing both the direction of the blood flow as well as the veins draining into the left atrium.
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COLOR AND PULSED DOPPLER |
- Low velocity blood flow (decrease velocity settings on color flow to under 0.2 m/s).
- Pulmonary veins drain into the Left Atrium
- Pulmonary venous flow in the fetus is similar to that reported in children and adults (1).
- Waveform.
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- Initial peak followed by continuous flow during ventricular systole (represents atrial filling secondary to the "suction" effect of atrial relaxation).
- Peak during early diastole (due to rapid atrial emptying across the mitral valve).
- Period of no flow or reversed flow during atrial contraction.
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Video clip of normal pulmonary vein Video clip of
pulmonary vein waveform
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Reference.
- Feller Printz BF, Allan LD. Abnormal pulmonary venous return diagnosed prenatally by pulsed doppler flow imaging. Ultrasound Obstet Gynecol 1977;9:347-349.