Myocardial global longitudinal strain: An early indicator of cardiac interstitial fibrosis modified by spironolactone, in a unique hypertensive rat model

Figures

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  Fig 1. Overview of the experimental design. Animals were given an initial two weeks on the 0.167% w/w indole-3-carbinol (I3C) diet to establish hypertension before commencing daily spironolactone (SP) dosing. Every month, animals had systolic blood pressure (SBP) measured and an echocardiogram (Echo) performed. After one month, a sub set of animals (n = 8) were terminated, while the remaining animals were terminated following three months. Normotensive animals were only terminated after three months.

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  Fig 2. Left ventricular ejection fraction after one, two and three months. Left ventricular ejection fraction (LVEF) of normotensive (N, grey, n = 8), hypertensive (H, black, n = 8) and hypertensive animals dosed daily with spironolactone (H+SP, dashed line, n = 4) after one, two and three months. Values are shown as mean ± 95% confidence intervals. Significance between N and H is indicated by *, p<0.05 *, p<0.001 *** Significance between N and H+SP is indicated by †, p<0.001 ††† Significance between H and H+SP is indicated by #, p< 0.05 #, p<0.01 ##.

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  Fig 3. Hypertension and cardiac fibrosis. 3(a) Cardiac transverse sections, taken 6mm from the apex (scale bar is 3mm) from normotensive animals (N) after three months, hypertensive animals (H) and hypertensive animals with spironolactone (H+SP) after both one and three months. Sections were stained with picrosirius red and light green counter stain. Inlay sections (50x magnification, scale bar 100μm) are taken from the lateral wall of the left ventricle. (3b, 3c) Percentage of fibrosis of the left ventricle (transverse sections taken 6mm from the apex) from normotensive (N, grey, n = 8), hypertensive (H, black, n = 8) and hypertensive animals dosed daily with spironolactone (H+SP, striped, n = 4) following one month (b) and three months (c). Values for normotensive animals were taken at three months only (dashed line), and were compared with hypertensive and spironolactone treated animals at both one month and at three months. Values are shown as mean ± standard deviation.

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  Fig 4. Global longitudinal strain analysis. Global longitudinal strain (GLS) tracking analysis (a), showing the region of interest and the strain assessment at both one month and three months in normotensive (N), hypertensive (H) and hypertensive with spironolactone (H+SP) groups. (b) Analysis of the endocardium layer and (c) myocardium layer from normotensive (N), hypertensive (H) and hypertensive animals with spironolactone (H+SP) following one, two and three months. Values are shown as mean ± standard deviation. Significant differences between N and H is indicated by *, p<0.05 *, p<0.01 **, p<0.001 *** Significant differences between N and H+SP is indicated by †, p<0.05 †, p<0.01 †† Significant differences between H and H+SP is indicated by #, p< 0.05 #, p<0.01 ##.

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  Fig 5. Comparison of left ventricular fibrosis and myocardial global longitudinal strain. Data from individual animals comparing left ventricular cardiac fibrosis (%) against EF% (a, c) and myo-GLS (b, d) in normotensive animals (N, grey circles, data only available following three months), hypertensive animals (H, black circles) and hypertensive animals dosed daily with spironolactone (H+SP, triangles) after one month (a, b) and three months (c, d). The black dotted lines represent the 95% CI normal reference range of the normotensive animals. r2 correlation values are shown on each graph for all data.