In this multicentre , randomised , double-blind , placebo-controlled , phase 3 study , patients aged 18-80 years with a genotype-confirmed or clinical diagnosis of heterozygous familial hypercholesterolaemia , on optimum lipid-lowering treatment for at least 6 weeks , and with an LDL-C concentration of 259 mmol/L or higher without cardiovascular disease or 181 mmol/L or higher with cardiovascular disease from 26 lipid clinics across nine countries were eligible .