In vitro versus in vivo assessment of vein wall properties

Venous compliance reflects the mechanical properties of the vein wall. Clinical methods of measurement have not been validated by comparison with the accepted in vitro measurement. Despite this, clinical assessment of vein compliance may have a series of useful applications: (1) to assess the progression of chronic venous insufficiency and the related hemodynamic forces acting on the saphenous vein wall; (2) to determine the suitability of the saphenous vein for replacement of an arterial conduit by testing its mechanical properties; and (3) to select the saphenous vein with preferable mechanical performance for coronary artery bypass. The aim of this study is to assess the relationship between in vitro and two in vivo methods of compliance measurement. Compliance of the saphenous vein was determined in 20 patients, using both an invasive and a noninvasive (A and B, respectively) method. Duplex scanning was used for diameter measurement. Venous pressure was derived either intravenously with a needle transducer, or noninvasively with limb length measurement. Patients underwent saphenous excision with further in vitro compliance measurement of the same vein segment (method C). The compliance values obtained with the three methods showed different degrees of correlation (r= 0.516, p = 0.0001 for method A versus method C; r = 0.658, p = 0.0001 for method B versus method C; r = 0.993, p = 0.0001 for method A versus method B). The relationships with the in vitro measurements that were determined validate both in vivo methods for assessment of saphenous vein compliance. Due to its completely noninvasive design, method B appears to have potential use for clinical assessment of saphenous vein wall properties.