M-mode echovenography: a new technique for the evaluation of venous wall and valve motion.

The M-mode technique which is widely used in echocardiography allows continuous recording of spontaneous venous wall movements. Compliance of the vein can be quantified. The diameter of the normal vein changes with respiration, while only minor changes are induced by cardiac function. Distensibility and compressibility of the common femoral vein (CFV) were documented. During Valsalva manoeuvre the mean diameter of the CFV increased from 1.05(SD 0.18) cm to 1.52(0.25) cm (p less than 0.01) in the recumbent position and from 1.50(0.20) cm to 1.63(0.17) cm (NS) in the upright position. A patent vein can be completely compressed by the scan head, a thrombosed vein is incompressible. The valve of the normal subclavian vein describes a characteristic M-shaped tracing. The waveform is modulated by cardiac and respiratory function. The study of venous wall movement and venous valve motion provides new insights into venous physiology.