Pulmonary Vein Doppler for Echocardiography
©Walter Rasmussen, R.D.C.S.
There are four pulmonary veins emptying in to the left atrium and the most accessible is the right upper pulmonary vein, seen in the apical four chamber view, at the bottom-most border of the left atrium, near the interatrial septum. Adjust the depth of the image so that several centimeters of tissue is visible beyond the left atrium. The pulmonary vein may be visible by two dimensional imaging alone, however, it is much easier to find with the aid of color Doppler. Since the site is one of the farthest structures from the transducer it is important to narrow the sector width to boost the color Doppler frame rate. Adjust the color Doppler box to cover just the area of interest and search for the characteristic pulsing red venous inflow which can be either very prominently pouring into the atrium or faintly displayed and very brief depending upon left atrial filling characteristics.
If the typical pulsing red color Doppler display it is not immediately visible, lower the scale and/or the Doppler flow setting. Make sure that the wall filter is not set too high. Rotation of the transducer clockwise or counter-clockwise by minute degrees can help to locate the vein and maximize the color Doppler signal. In patients with severe dysfunction, the scale may need to be set as low as 20 to 30 cm/sec in order to observe pulmonary vein flow on color Doppler. It is important to not confuse the pulmonary vein flow with the SVC flow, which is found on the right atrial side of the interatrial septum and can look very much like pulmonary vein flow.
After locating and recording color Doppler of the pulmonary vein, position the PW Doppler sample volume over the flow, as far into the vein as possible. Record a digital clip of the two dimensional and color Doppler image, demonstrating the position of the sample volume within the pulmonary vein blood flow. Activate the PW Doppler and look for a clear spectral display of the typically twin-peaked flow velocity above the baseline. In difficult cases, it can take quite a bit of effort to obtain the recording. Since pulmonary vein flow is usually of low velocity, high PRF Doppler should not be used.
While recording pulmonary vein blood flow, the PW Doppler baseline should be adjusted to include blood flow both above and below the baseline. If both diastolic and systolic pulmonary vein blood flow does not fit within the graph, record them individually by adjusting the baseline, –not by using high PRF. The adjustment of sample volume size might also improve a weak signal.
If the right upper pulmonary vein site is not successfully imaged, it is often possible to find an alternate pulmonary vein from the apical, subcostal or parasternal views.
Blood flow reversal in the pulmonary vein can help in assessing the severity of mitral regurgitation. The PW Doppler sample volume should be placed as deep as possible in to the pulmonary vein in order to assure that an apparent reversal is not caused by turbulence within the left atrium. In addition, if the jet of mitral regurgitation is seen near or directed toward or entering the pulmonary vein, the site cannot be used for assessment of its severity and an alternate pulmonary vein should be recorded.
Spectral Doppler of pulmonary vein flow may be impossible to record in the presence of irregular or paced heart rhythms.
When a prosthetic mitral valve is in place, shadowing often blocks the ultrasound from reaching the area where the pulmonary vein is located however; alternate views of the left atrium such as the parasternal long axis and the subcostal four-chamber may provide other pulmonary veins to interrogate.