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It has always been known that valvular
incompetence is the reason behind poor venous return.
Valvular incompetence can occur due to primary valve
failure in the superficial venous system as in varicose
veins, or as a consequence of both primary valve failure
and thrombus formation in the deep veins, as seen in
post-phlebitic syndrome.
Newer insight
into the pathophysiology of chronic venous insufficiency
of the lower limbs suggests that loss of venous elasticity
or tone precedes valvular incompetence. Thus, venous
reflux not only occurs due to valvular incompetence
but also due to poor venous wall tone around the valvular
ring.
The wide variation in the venous wall tone is due to
genetic factors. This has been corroborated by a three-fold
increase in the prevalence of varicose veins in South
India as compared to North India.
- Vascular tone and smooth muscle contractility of
the vessel wall has been found to be determined by
a genetically-mediated, variable response to noradrenaline.
- People with risk factors for varicose veins such
as prolonged standing and overweight, have been shown
to have reduced venous tone as compared to those without
risk factors.
- In pregnancy, it has been observed that excess of
oestrogen in the blood has a definite relaxant effect
on the smooth muscles, particularly of the venous
wall, thus reducing the venous tone. As a consequence
of poor venous wall tone, valvular incompetence occurs
leading to venous reflux and therefore venous stasis.
This causes venous hypertension, as shown by a smaller
fall in ambulatory venous pressure on exercise, as
compared to normal. This leads to the development
of varicose veins. Patients with varicose veins are
more prone to develop thrombotic episodes in the deep
veins thus leading to post-phlebitic syndrome. In
post-phlebitic syndrome, venous outflow obstruction
causes venous reflux, further impairing venous return
thus provoking a vicious cycle of venous stasis and
hypertension.
The treatment of venous insufficiency
of the lower limbs ranges from elastocrepe bandaging
to surgery. In recent years, the role of phlebotonic
drugs in its management has been investigated. The aim
of the treatment of venous insufficiency of the lower
limbs is to normalize venous return, thus preventing
venous stasis and the subsequent consequences of venous
hypertension. Drugs, which have a specific mode of action
in the correction of the underlying disorders of venous
insufficiency of the lower limbs at each level need
to be adopted as a first line therapy in the management
of venous disease.
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