Human internal jugular valve M-mode ultrasound characterization

Area of Science:

• Vascular Ultrasound
• Human Physiology
• Anatomy

Background:

• The precise mechanism of internal jugular vein (IJV) valve function in humans is not well understood.
• While M-mode ultrasound is standard for cardiac valves, its application to IJV valves is novel.
• Previous assessments have not utilized M-mode for IJV valve evaluation.

Purpose of the Study:

• To investigate the physiology of internal jugular vein valves in healthy volunteers.
• To assess IJV valve characteristics using B-mode and M-mode ultrasound.
• To understand the impact of posture and cardiac cycle on IJV valve dynamics.

Main Methods:

• Eighty-three healthy volunteers (35 male, 48 female) underwent high-resolution B-mode and M-mode ultrasound of 166 IJVs.
• Evaluations were conducted under standardized postural and respiratory conditions.
• Assessment included valve presence, cusp number, motility, and opening/closure mechanisms.

Main Results:

• Bilateral IJV valve absence was noted in 16% of subjects, with at least one absent in 46%.
• Valve leaflets were mobile, predominantly bicuspid (34%) or unicuspid (27%), with unicuspid valves more frequent on the left.
• In supine position, valves opened synchronously with the cardiac cycle; in upright position, valves remained open and apposed to the wall.

Conclusions:

• Internal jugular vein valve leaflets are mobile, but a high rate of absence suggests potential phylogenetic loss of function.
• M-mode ultrasound provides enhanced characterization of IJV valves.
• Routine addition of M-mode ultrasound to cerebral venous return investigations is recommended.