DYNAMIC ASSESSMENT OF VENOUS VALVULAR FUNCTION USING M-MODE ULTRASONOGRAPHY

AKH Chao*, W Yung#, J Crozier#, JP Fletcher*

*Department of Surgery, Westmead Hospital, Westmead NSW 2145
#Vascular Diagnostic Service, Liverpool Hospital, Liverpool NSW 2170

ASUM'99 - Winner of the Acuson Best Research Presentation Award

Introduction
"M" or motion mode ultrasound is commonly employed in echocardiography to assess valvular function of the heart. Valves in the venous system have hitherto been difficult to identify on "B"-mode ultrasound, but with the advent of newer, high resolution ultrasound scanners, venous valves in the veins of the lower limb are better imaged. Adequacy of peripheral venous valvular function has been evaluated using indirect means such as pulsed doppler waveform analysis of venous flow with augmentation, and photoplethysmography. A direct test to assess the dynamic function of the venous valve has been described for the valves of the internal jugular vein but not the peripheral veins(1,2).

Aim
We describe a new method of assessing the dynamic function of the venous valves of the lower limb using M-mode ultrasonography.

Methods
Healthy volunteers without evidence of venous thrombosis or incompetence were enrolled in our study. They were initially scanned in the supine position using an ATL 3000 HDI using a 10-5 Mhz linear transducer or 7-4 Mhz linear transducer. The valve in the long saphenous vein (LSV) nearest the saphenofemoral junction (SFJ), the valve in the superficial femoral vein (SFV) just below the confluence of the long saphenous vein, and the valve in the common femoral vein (CFV) just above the saphenofemoral junction was evaluated initially in real-time B-mode. M-mode was then used to interrogate the valvular apparatus and the following parameters were determined: frequency (F) of valvular closure in "beats" per minute, closing time (t) and velocity (v) of leaflet closure (acceleration time). Changes in response to Valsava manoeuvre, standing and the activation of calf muscle pump by depressing a pedal were also noted. Patients with previous deep venous thrombosis and venous incompetence were also evaluated.

Results
The frequency (F) of valvular closure was found to correlate with the atrial pulsatility and therefore the subject's heart rate. However this action was abolished on Valsalva and when the subject adopts an erect position. The valve would then open again in response to calf compression or activation of the calf muscle pump. The average closure time is 85 ms and the velocity of closure averages about 2.3 cm/s. This valvular leaflet motion appears to be abolished in patients with previous thrombosis.

Conclusion
M-mode ultrasonographic evaluation of lower limb venous valve function is possible and has potential application in the evaluation of the efficacy of newer methods of venous valvular repair such as valvuloplasty, external ring reinforcement and venous valve transplantation.

References