Quantitative Assessment Of Myocardial Elasticity In Isolated Ventricular Wall Using Real-time Ultrasonic Tissue Elastography

Objective：To assess myocardial elasticity in different locations of theisolated porcine ventricular wall using real-time ultrasound tissueelastography (RTE) technology and analyze the correlations between themyocardial elasticity and the content and three-dimension distribution ofmyocardial interstitial collagen fibers quantitatively.Methods：Ten isolated porcine hearts were used for the RTE researchof ventricular myocardium. Cubical segments were excised from left andright ventricular anterior walls and interventricular septum (IVS) at thebase of ventricles, respectively. Along the ventricular long and short-axisdirections, the elastic strain ratio (SR) of2%agar without collagen fibers tothe myocardium was measured and calculated using ultrasonic RTEtechnology. Combined with the area (CA) and the area percentage (CA%)of myocardial interstitial collagen fibers,content in the three differentlocations of patho-histological slice with Masson,s Trichrome stain, SR,CA and CA%in the long or short-axis direction were compared among the three different locations, and the three parameters were compared betweenthe ventricular long and short-axis directions in each location, respectively.Besides, the correlations between the myocardial elasticity and the contentand distribution of myocardial interstitial collagen fibers in the threedifferent locations were also analyzed.Results：(1) RTE findings:①Along the ventricular long-axisdirection, LV and RV scored0~1and IVS scored1~2using RTE. Along theventricular short-axis direction, LV, RV and IVS scored0~1using RTE.②Along the ventricular long-axis direction, there were statistically significantdifferences of SR between LV, RV and IVS (P＜0.01). Along theventricular short-axis direction, there were no statistically significantdifferences of SR between LV, RV and IVS (P＞0.05).③There werestatistically significant differences of SR between the ventricular long-axisdirection and short-axis direction at IVS (P＜0.01). There were nostatistically significant differences of SR between the ventricular long-axisdirection and short-axis direction at LV and RV (P＞0.05).(2)Patho-histological findings:①Along the ventricular long-axis direction,there were statistically significant differences of CA and CA%between LV,RV and IVS (P＜0.05). Along the ventricular short-axis direction, therewere no statistically significant differences of CA and CA%between LV,RV and IVS (P＞0.05).②There were statistically significant differences ofCA and CA%between the ventricular long-axis direction and short-axis direction at IVS (P＜0.05). There were no statistically significantdifferences of CA and CA%between the ventricular long-axis direction andshort-axis direction at LV and RV (P＞0.05).(3) The statistically significantpositive linear correlations between SR and CA and CA%were found(r=0.57~0.73,P＜0.05).Conclusions：By using ultrasonic RTE, the myocardial elastic strainratio between LV, RV and IVS in the long and short-axis directions isdifferent, along with the area and the area percentage of myocardialinterstitial collagen fibers’ content in the long and short-axis directions aredifferent. The correlations between the myocardial elasticity and thecontent and distribution of myocardial interstitial collagen fibers have beenestablished.