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

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). 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. Key words: Echocardiography; Spontaneously hypertensive rat; Strain; Cardiac dysfunction