自发性高血压大鼠左室心肌应变特点及其与心功能不全类型的关系

The relationship between left ventricular myocardial strain and different stages of cardiac dysfunction in spontaneously hypertensive rats evaluated by two-dimensional strain echocardiography

目的应用应变二维超声心动图技术观察自发性高血压大鼠(SHR)在左心功能不全不同阶段心肌各向应变特点及其与整体心功能的关系。方法按心功能情况将28~102周龄SHR分为心功能正常组[A组,左室射血分数(LVEF)与左室舒张末期压力(LVEDP)均正常,13只]、舒张功能不全组(B组,LVEF值正常但LVEDP增高,24只)和收缩功能不全组(C组,LVEF降低且LVEDP增高,17只);以相同周龄段WKY大鼠为对照(分别为a组7只,b组12只,c组16只)。应用超声心动图获得左心结构指标及LVEF,在EchoPac工作站上分析获得左室乳头肌水平收缩期峰值纵向应变、周向应变、径向应变;组织学观察心肌间质胶原含量。结果①B组左房内径较A组、b组增大(均P<0.05),C组左心内径及室壁厚度均较A组、B组、c组增大(均P<0.05)。②B组纵向应变较A组、b组显著下降(均P<0.05),在C组进一步下降(P<0.05);而周向、径向应变及LVEF在C组较A组、B组及c组明显下降,差异有统计学意义(均P<0.05),但A、B两组间差异无统计学意义(均P<0.05)。③B、C组SHR心内膜下及中层心肌间质胶原含量较A组显著增多,且分别高于b、c组,C组的心外膜下层心肌间质胶原含量较A组、B组及c组显著增多。④纵向、周向及径向应变与LVEF呈正相关(r=0.65,0.80,0.80;均P<0.01)。结论SHR在舒张功能不全时已出现超声心动图上纵向应变的受损,当径向及周向应变均受累时才导致收缩功能不全。

Objective To investigate the relationship between multi-dimensional myocardial strain and global cardiac function in different stages of cardiac dysfunction in spontaneously hypertensive rats (SHR) by two-dimensional strain echocardiography. Methods According to cardiac function measurements, SHR of 28 to 102 weeks were divided into 3 groups: Normal group[Group A, normal left ventricular ejection fraction(LVEF) and left ventricular end-diastolic pressure(LVEDP), n=13], diastolic dysfunction group (Group B, normal LVEF but increased LVEDP, n=24), and systolic dysfunction group (Group C, decreased LVEF and increased LVEDP, n=17), with WKY rats at similar weeks of age as controls (group a, n=7;group b, n=12;and group c, n=16). Morphological parameters of left ventricular were measured by echocardiography. Using EchoPac workstation, systolic peak longitudinal strain, circumferential and radial strain were calculated at the left ventricular middle levels. Extracellular collagen content was observed histologically. Results Left atrial dimension increased in group B and larger in group C, and dilated left ventricular and thickened wall were only found in group C. Systolic peak longitudinal strain of group B was significantly lower than group A and group a(all P<0.05), and deteriorated in group C(P<0.05), while systolic peak circumferential and radial strain and LVEF were only significantly decreased in group C (all P<0.05), while there was no significant difference between Group A and Group B(all P>0.05). Collagen content in endocardial and mid-layer myocardium increased in group B and C, and increased epicardial collagen occurred in group C. Systolic peak longitudinal strain, circumferential and radial strain were correlated positively with LVEF(r=0.65, 0.80, 0.80, all P<0.01). Conclusions In SHR, systolic peak longitudinal strain obtained by echocardiography is decreased in the period of diastolic dysfunction, while the damage of systolic peak circumferential and radial strain leads to the systolic dysfunction.