Calf Muscle Pump Works Like Stream Diversion Pump

Calf muscle pump (CMP) failure is associated with the development and progression of chronic venous insufficiency and characterized by progressive deterioration of centripetal blood ejection (ejection fraction [EF] and residual volume fraction [RVF] of plethysmography). The increase in blood flow through deep veins during calf muscle activity has been shown. However, the changes in blood flow through the GSV have not been directly investigated. In addition, direct measurements of venous flow and pressure were never done during normal ambulation. The aim of this study was to measure the pressure gradient across the Great Saphenous Vein (GSV) and between segments of the GSV and the deep veins during normal ambulation.

Methods:

The pressure in the great saphenous vein at three levels (ankle [GSV_ANKLE], proximal calf [GSV_CALF], and mid-distal thigh [GSV_THIGH]) and in veins of gastrocnemius muscle [IV_CALF], was continuously measured in twelve legs of nine healthy volunteers. The muscle activity was monitored simultaneously with pressure measurement by electromyography of gastrocnemius (GCM) and anterior tibial muscle (ATM). All measurements were done at rest, and during treadmill walking (30, 45 and 60 strides per min), running (75 and 90 strides/min) and plantar flexion (30, 45 and 60 flexions/min). Pressure gradient (PG, mmHg) between adjacent points of measurement was calculated.

Results:

A consistent pattern of PG changes was observed during walking and running. In addition to expected PG between the intramuscular and superficial veins, an absence of PG directed from the calf to thigh (centripetal) in GSV was observed at all times (Figure 1). Instead, a retrograde PG was registered during the entire time of the stride cycle. The magnitude of this PG decreased with the increase in stride cycles frequency. The dynamics of PG between superficial and deep veins paralleled the synergistic work of antagonist calf muscles, with the PG magnitude considerably higher than PG between any of the GSV levels. The PG was directed from deep to superficial veins during GCM concentric contraction and was reversed during ATM concentric contraction and GCM relaxation during swing phase.

Conclusions:

During locomotion (walking and running) the pressure gradient in the GSV prevents centripetal flow. Instead, the PG directs blood outflow from the superficial venous network toward intramuscular veins through perforating veins.