Failure of microvenous valves in small superficial veins is a key to the skin changes of venous insufficiency

Vincent JR, Jones GT, Hill GB, et al (Univ of Otago, Dunedin, New Zealand) J Vasc Surg 54:62S-69S.e3, 2011^§

Abstract

Objective

To determine the role of microvenous valves in the superficial venous system in the prevention of reflux and skin changes in the progression of venous insufficency.

Methods

The venous anatomy of 15 amputated lower limbs, eight free from clinical venous disease and seven with varicose veins and ulcers, was examined using retrograde venography corrosion casting. Prior to amputation, all limbs were scanned by duplex ultrasound to confirm the presence or absence of reflux in the great (GSV) and small saphenous veins or their tributaries. The resulting resin casts were photographed and mapped to show the position, orientation, and competency of valves in the superficial venous network. Casts were also examined by scanning electron microscopy.

Results

Retrograde venous filling was demonstrated in the “normal” limbs despite a competent GSV. Microvalves were identified down to the sixth generation of tributaries from the GSV. Only in regions where incompetence existed in microvalves out to the third (ie, the “boundary”) generation was the resin able to penetrate deeper into microvenous networks of the dermis. This was despite the presence of subsequent competent valves, which were able to be bypassed in the network. In limbs with varicose veins and venous ulcers, reflux into the small venous networks and capillary loops was more extensive with more dense networks and greater tortuosity.

Conclusions

This study demonstrates that valvular incompetence can occur independently in small superficial veins in the absence of reflux within the GSV and the major tributaries. We have shown that once there is incompetence of the third generation “boundary” microvalves, reflux can extend into the microvenous networks in the skin. These effects are markedly worse in the presence of GSV incompetence. We propose that degenerative changes with valve incompetence are required in both the larger proximal vessels and the small superficial veins, in particular at the “boundary” valve level, for the severe skin changes in venous insufficiency to occur (Figs 1D, 4, 6, 7C, D and 8).

Figure 1 D. Varying patterns of retrograde resin casting in normal limbs (CEAP 0 or 1). All limbs had competent great saphenous veins (GSVs) as determined by ultrasound. D, Multiple territories of small vein network filling and dilated tortuous (arrow) veins (63-year-old female). Of note, the GSV was intact with numerous competent valves and tributaries (arrowheads). (Reprinted from the Journal of Vascular Surgery. Vincent JR, Jones GT, Hill GB, et al. Failure of microvenous valves in small superficial veins is a key to the skin changes of venous insufficiency. J Vasc Surg. 2011;54:62S-69S.e3, Copyright 2011, with permission from the Society for Vascular Surgery.)

Figure 4 Schematic representation of valve distribution and effect of competency on resin filling with table of actual total valve counts by generation and competency. As shown in the table, competent valves were found through all six generations, while the vast majority of incompetent valves were observed in generations one to three (94%). The concept of a “boundary” valve is represented in the schematic by an incompetent valve in generation 3 (B). Reflux through this valve results in widespread filling of the subsequent generations of tributaries, despite the presence of a more distal competent valve. The two other incompetent valves shown in generations two and three are not boundary, as subsequent competent valves prevent further resin reflux. ^∗Generation could not be determined, usually due to cast breakage. (Reprinted from the Journal of Vascular Surgery. Vincent JR, Jones GT, Hill GB, et al. Failure of microvenous valves in small superficial veins is a key to the skin changes of venous insufficiency. J Vasc Surg. 2011;54:62S-69S.e3, Copyright 2011, with permission from the Society for Vascular Surgery.)

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