Stretch calculated from grip distance accurately approximates mid-specimen stretch in large elastic arteries in uniaxial tensile tests

Abstract

The mechanical properties of vascular tissues affect hemodynamics and can alter disease progression. The uniaxial tensile test is a simple and effective method for determining the stress-strain relationship in arterial tissue ex vivo. To enable calculation of strain, stretch can be measured directly with image tracking of markers on the tissue or indirectly from the distance between the grips used to hold the specimen. While the imaging technique is generally considered more accurate, it also requires more analysis, and the grip distance method is more widely used. The purpose of this study is to compare the stretch of the testing specimen calculated from the grip distance method to that obtained from the imaging method for canine descending aortas and large proximal pulmonary arteries. Our results showed a significant difference in stretch between the two methods; however, this difference was consistently less than 2%. Therefore, the grip distance method is an accurate approximation of the stretch in large elastic arteries in the uniaxial tensile test.

Pulmonary arterial strain- and remodeling-induced stiffening are differentiated in a chronic model of pulmonary hypertension

“…1A) and then mechanically tested ex vivo . Samples were clamped in grips and pulled in uniaxial tension as described previously (Tian et al, 2015a). Briefly, tissues were initially stretched to remove buckling, and the gauge length for each sample was recorded after a small load was observed.…”

“…This is consistent with a previous investigation that found minimal hysteresis in canine PA tissues (Debes and Fung, 1995). Samples were then tested at a rate of 20% gauge-length/s (Tian et al, 2015a; Tian et al, 2014) until the force-extension curve exhibited nonlinear elastic behavior.…”

“…1B) as previously done by our group (Kobs and Chesler, 2006; Tabima and Chesler, 2010; Wang and Chesler, 2012). The low- and high-strain regions were taken at stretches from 1.1–1.2 and 1.7–1.8, respectively, based on literature values for arterial stretch encompassing physiological and pathological PA stretch ranges (Kao et al, 2011; Learoyd and Taylor, 1966; Tian et al, 2015a; Vaishnav et al, 1990). Transition strain was determined using the intersection of the fit lines as previously done (Liu et al, 2015).…”

Biaxial quantification of passive porcine myocardium elastic properties by region

“…During these tests, the specimens are generally clamped to the machine actuator using mechanical clamps (Perez et al, 2014, Hu et al, 2014, Nolan and McGarry, 2016. The interpretation of biaxial test results is complex and the direct use of material parameters in computer simulation may be complex (Tian et al, 2015, Delgadillo et al, 2015. In the present study, the stress-strain on the LV, septal and RV walls was presented to investigate the cardiac mechanics.…”

Determination and Finite Element Validation of the WYPIWYG Strain Energy of Superficial Fascia from Experimental Data

“…Following the analysis and recommendation given in Ref. [21], we also considered an effective length of 95% of the actual distance between grips in order to compute the strains from measured displacements between grips (abscissae in Figure 2). This gives a reference effective length of 15.39 mm for the longitudinal specimen and a reference effective length of 12.16 mm for the transverse specimen.…”