Doppler evaluation of central venous lines in the superior vena cava.

Thrombus formation in the superior vena cava (SVC) complicates the use of central venous catheters. Visualizing the thrombus by two-dimensional echo-cardiography is often difficult. Flow in the SVC can be recorded by using color flow Doppler examinations. Hence SVC flow was evaluated by color flow Doppler in 12 patients before and within 48 hours of central venous catheters. Five patients with catheters in their SVCs, with suspected thrombus or obstruction to the SVC, were also studied. The SVC flow in the subjects before catheter placement was characterized by two distinct peaks, respiratory variability, and maximal velocities between 0.5 and 1.5 m/sec; these were unchanged by the catheters. The five patients with thrombus or obstruction had turbulent flow, loss of a distinct biphasic profile, and increased velocity downstream to the thrombus and decreased velocity upstream. It appears that Doppler study is a worthwhile adjunct to two-dimensional echocardiography in the evaluation of catheter-related thrombus, and that an altered SVC flow profile with increased velocity suggests thrombus formation or obstruction or both.