Teaching Case

A 57-year-old previously healthy female was admitted due to dyspnoea on exertion, tremor, and bilateral asymmetric leg swelling. ECG revealed atrial fibrillation (AF) with a tachycardic ventricular response. Laboratory studies found distinctly increased levels of T3, T4, nt-pro-BNP, D-dimer, cholestatic liver enzymes, bilirubin, INR, and hypoalbuminemia.

A venous Doppler US of both lower extremities was performed to rule out deep vein thrombosis in bilateral, however asymmetric leg swelling and high values of D-dimer.

Both femoral veins exhibited a pulsatile flow in nature on a pulse Doppler, with a prominent retrograde flow, compared to a normal antegrade femoral vein flow pattern (Figures 1a, 1b, 1c and 3b). The pulsatile flow pattern in a reduced manner could also be observed in both popliteal (Figure 2) and great saphenous veins

On the US, bilateral subcutaneous oedema in both lower extremities was identified (clinically, the right lower extremity exhibited increased circumference compared to the left). There was no evidence of deep vein thrombosis.

The US revealed bilateral pleural effusion and a small pericardial effusion. Heart US demonstrated severe tricuspidal regurgitation with a dilated right atrium and a 3 cm broad, noncollapsible inferior vein cava. CTA excluded pulmonary embolism.

Femoral vein pulsatility has become an important, easily obtainable, and reliable ultrasound marker of systemic venous congestion in patients with heart failure. It is a simpler tool than the VEXUS score, which includes changes in the hepatic, portal, and renal venous Doppler signal and changes in IVC diameter. Recently, the study of V. Bhardwaj [1] revealed that changes in femoral vein Doppler (FVD) have a strong correlation with the VEXUS score [1] and M. Torres [2] that FVD pulsatility correlates well with increased IVC diameter, significant tricuspid regurgitation, and pulmonary hypertension in acute heart failure patients [2,3].

Normally, cardiac pressure waves are not transmitted through the venous system retrogradely, which changes as the right ventricle fails and the right atrial pressure rises due to volume overload and venous valve insufficiency. Therefore, in the femoral vein, cardiac modulation is observed, and no more normal respiratory variation. Right ventricular failure results in bidirectional flow in the femoral vein due to a larger "A" wave, representing a contraction of atria against the stiff right ventricle with diastolic dysfunction and due to severe tricuspid regurgitation (TR) [1,4–7].

A normal flow should be antegrade continuous with a mean velocity around 10 cm/s with phasic peak retrograde flow less than 5 cm/s or 10 cm/s. Currently, based on the literature review, a lack of agreement exists on the definition of the pulsatile flow. Abnormally reversed FVD flow corresponds to >50% or >1/3 of the antegrade flow. Flow should neither be pulsatile in nature nor should retrograde flow exceed 10 cm/s [1,4,8]. The use of FVD for congestion evaluation is limited in liver cirrhosis, respiratory distress, and increased intraabdominal pressure [1].

FVD is performed with the patient lying supine with the linear probe. Spectral Doppler can be performed either in the short axis of the vein, without angle correction, or in the long axis of the vein with angle correction. The main drawback of the US Doppler measurement using a short axis is the underestimation of the true velocities [1,4,8]. We performed a Doppler US of the deep veins of the lower extremities to rule out deep vein thrombosis, therefore, according to the protocol, we used the short axis and assessed the compressibility of the vein. We used the Doppler signal for the respiratory flow variability assessment. Instead of a normal antegrade, we obtained an unusual pulsatile flow pattern.

Our patient was haemodynamically stable and received thiamazole due to Graves' disease, NOAC due to AF, propranolol to reduce heart rate and tremors, and diuretics to reduce systemic congestion.

On follow-up FVD three weeks later, normal antegrade flow was discriminated (Figure 1c).

Take home message

Femoral vein Doppler could be used to identify systemic venous congestion and monitor fluid status. It can also be used to rule out significant right ventricular dysfunction.

All patient data have been completely anonymised throughout the entire manuscript and related files.