CD68 and Hypertension: In comparison to normotensive WKY controls, hypertension in the SHR led to significant: i) Bi-atrial enlargement and bi-ventricular hypertrophy; ii) Abbreviation of atrial refractoriness; iii) Increase in atrial conduction heterogeneity & iv) Increase in atrial myocyte dimension, interstitial fibrosis and CD68-positive macrophages infiltration.