There was a significant linear correlation between serum ferritin level and longitudinal ( r = 0.44 , P = 0.0078 ) and radial strain ( r = -0.46 , P = 0.0051 ) , with optimal cutoff provided to be -15.48 % , -21.31 % , and 26.67 % for longitudinal , circumferential , and radial strain in predicting clinical events , respectively .