Pulsatile flow in venous perforators of the lower limb

Area of Science:

• Physiology
• Vascular Biology
• Hemodynamics

Background:

• Traditionally, arterial pressure pulses are thought to be absent in lower limb venous circulation due to capillary bed dampening.
• Perforator veins, connecting superficial and deep venous systems, typically show minimal flow and no pulsatility at rest.

Purpose of the Study:

• To investigate the presence and characteristics of arterial pulsations in lower limb perforator veins under heat stress conditions.
• To challenge the established notion of absent venous pulsatility in the lower limbs.

Main Methods:

• Duplex ultrasound was used to measure blood velocity in ankle perforator veins of healthy volunteers.
• Participants underwent passive heating (hot-water suit) and active heating (cycling with suit) to increase core body temperature by +2°C.
• Measurements were taken at +0.5°C increments, and microvascular imaging assessed skin vein perfusion.

Main Results:

• Sustained, pulsatile blood flow, synchronous with the cardiac cycle, was demonstrated in all heated perforator veins.
• Maximum velocity reached 30 ± 13 cm/s with passive heating, significantly higher than with active heating (P=0.04).
• Increased perfusion and pulsatility were also observed in small skin veins at the ankle using microvascular imaging.

Conclusions:

• Arterial pulsations can transmit across the capillary network into lower limb perforator veins during heat-induced increases in skin blood flow.
• This pulsatility is attributed to increased vasodilation and flow volume, representing a normal physiological response.
• Findings necessitate a re-evaluation of the understanding of venous hemodynamics in the lower extremities under physiological stress.