Comparison Of The Stiffness Of The Normal And Hypertrophic Isolated Myocardial Wall In Rabbits

Objective:　The aim of this study was to compare the discrepancy between the stiffnesses of the normal and hypertrophic isolated myocardium in rabbits by analysing the stress-strain relationships of free wall with our prototype load-deformation experimental device, and to explore the feasibility of detecting myocardiul stiffness by indentation test.Methods:　The animal model of left ventricular hypertrophy was induced by the two-kidney,one-clip renal hypertension in rabbits.　Forty-five rabbits were divided into three groups randomly: Group Ⅰ－control group (N ,n=15); GroupⅡ－two-month group after operation(2M ,n=15); Group Ⅲ－three-month group after operation(3M ,n=15). To assess myocardial stiffness, the stress-strain relationships of the normal and hypertrophic isolated myocardial free wall were analysyed by utilizing our prototype load-deformation experimental device when the different forces was exerted perpendicularly .Results:1. The stress-strain relationships of the normal and hypertrophic isolated myocardial free wall could be fitted to a typical exponential equations : Y=A.eＢＸ (r=0.874-0.912).2. The stress-strain relationships was linear within the scope of a certain stress(For instance,4F:9.188±0.423～137.623±0.453g/cm2). In Group Ⅰ, the linear equations were: Y=11.095X-1.415(r=0.931,8F),Y=11.329X-0.174(r=0.937,6F),Y=11.372X-3.403(r=0.935,4F), there were no significantly　difference among the slopes of three linear equations(P>0.05). In Group Ⅱ, the linear equations were: Y=15.432X +2.905 (r=0.938,8F),Y=15.535X-1.019(r=0.934,6F),Y=15.479X- 0.301 (r=0.912,4F), there were no significantly　difference among the slopes of three linear equations (P>0.05). In Group Ⅲ, the linear equations were: Y=17.202X+4.792(r=0.937,8F), Y=17.217X+10.499(r=0.935,6F),Y=17.180X+27.757(r=0.939,4F), there were no significantly　difference among the slopes of three linear equations (P>0.05). ３．The myocardial stiffness of GroupⅠ, GroupⅡ and GroupⅢ was: 11.265±0.135g/cm2,15.388±0.136 g/cm2,17.199±0.019 g/cm2,respectively.Conclusions: 1. The stress-strain relationship of the normal and hypertrophic isolated myocardial free wall was linear in rabbits within the scope of a certain stress. The stiffness of the hypertrophic myocardium induced by the two-kidney,one-clip renal hypertension in rabbits was greater than that of the normal myocardium,the discrepancy between the stiffnesses of them could be detected by indentation test. 2. There was no significantly influence to assess the myocardium stiffness by utilizing the three different diameter probes.