Dynamic Mechanical Properties of Arterial and Venous Grafts Used in Coronary Bypass Surgery

Abstract

In this work we studied the frequency dependence of the dynamic mechanical characteristic s of saphenous vein (SV) and internal mammary artery (IMA) grafts. Rectangular longitudinal strips from 14 patients were tested under cyclic uniaxial tensile loading in the frequency range of 0.1–20 Hz, at 37°C in wet conditions. The dynamic mechanical parameters (the storage modulus ES and the hysteresis ratio h (loading/loop area)) together with the collagen phase modulus EH were computed as a function of frequency. The results showed that in all graft types ES and EH varied with frequency in the range 0.5–10 Hz, presenting a maximum in the neighboring of 1 Hz. The hysteresis ratio h was increased in the frequency range 1–20 Hz. It seems from the results that the physical resonance frequency of the components of the tissue responsible for their elastic behavior may lay in the range around 1 Hz, while that for the viscous behavior in the range of 20 Hz or more. Early clinical outcomes of both grafting were studied in parallel. In a one-year postoperative period the follow-up (clinical examination, electrocardiography, echocardiography and stress test) did not reveal any sign of graft occlusion or severe stenosis except one perioperative infraction but without any correlation to the graft quality.

Dynamic mechanical characteristics of intact and structurally modified bovine pericardial tissues

“…The strips were secured carefully by their narrow edges in special designed Plexiglas s grips of a custom made tensile testing machine, leaving a 5-7 mm free length between them. The detailed technical description of the testing apparatus has been published previously (Mavrilas et al, 2002). This machine was equipped with an electrodynamic vibrator system, which actuated the moving grip.…”

Functional properties of fresh and cryopreserved carotid and femoral arteries, and of venous and synthetic grafts: comparison with arteries from normotensive and hypertensive patients

“…Currently used methods for examining the biomechanical properties of blood vessels walls are (Mavrilas and Tsapikouni 2002;Silver et al 2003).…”

Viscoelastic Mapping of the Arterial Ovine System using a Kelvin Model

“…We opted for vascular segments, instead of the most used strips or rings [49], [50], since segments were better to reproduce the in vivo hemodynamic conditions, and to preserve the shape and integrity of the vascular wall [33]. The in vitro stretch of the artery segment should be the same with respect to in vivo condition.…”

“…Hence, although static analysis allow the indirect evaluation of rate or frequency-dependent mechanical properties (e.g., wall viscosity) [49], [50], an adequate characterization of the functional meaning and contribution of these properties requires dynamic analysis. Consequently, in order to evaluate the arterial wall mechanical behavior, we performed a dynamic analysis of the arterial wall, submitting the arteries to physiological hemodynamic conditions.…”