Investigation of Left Ventricular Strain and Its Morphological Basis During Different Stages of Diastolic and Systolic Dysfunction in Spontaneously Hypertensive Rat

Background Myocardial fibrosis plays an important role in the pathogenesis of hypertensive cardiac dysfunction, and myocardial strain could detect early systolic abnormalities when left ventricular ejection fraction (LVEF) is preserved. The aim of this study was to investigate the characteristics of left ventricular multidirectional strain during different stages of heart dysfunction and the possible morphological basis in spontaneously hypertensive rats (SHRs). Methods SHRs and Wistar-Kyoto (WKY) rats were randomly divided into cages and observed for 3-25 months. Echocardiographic measurements, LV + dp/dtmax and left ventricular end-diastolic pressure (LVEDP), and histological collagen volume fraction (CVF) were observed in all rats. Results According to LVEF and LVEDP, SHRs were divided into normal cardiac function group (group A), diastolic dysfunction group (group B1), and systolic dysfunction group (group B2). In group A, myocardial strain and CVF showed no difference compared with the control group. In group B1, global longitudinal strain (GLS) and endocardial longitudinal strain (SL-endo) were lower than those in group A CVF-endo was increased (all P < 0.05). In group B2, global and layer-specific strain decreased significantly, along with the increased CVF-endo and CVF-epi (all P < 0.05). The decrease of GLS and SL-endo was moderately correlated with the increase of CVF-endo. The reduction of LVEF was correlated with the decrease of SC-endo (r = 0.65, P < 0.01). Conclusions Pathological myocardial fibrosis associated with hypertension develops from the inner to outer layer of myocardium, which is coincident with the impairment of myocardial deformation, where longitudinal strain is involved firstly and LVEF declines when all directions of strain are reduced.

Automated summary

This study investigated the characteristics of left ventricular multidirectional strain during different stages of heart dysfunction in hypertensive rats and found that pathological myocardial fibrosis associated with hypertension develops from the inner to outer layer of myocardium. Impairment of myocardial deformation, especially in the longitudinal strain, is involved in the development of cardiac dysfunction.