NOS3 and heart failure: Although the present study’s exclusion criteria (diabetes mellitus, peripheral vascular disease, myocardial infarction, known heart failure, valvular heart disease, atrial fibrillation, dialysis-dependence and uncontrolled hypertension) limits the generalizability of its findings, the exclusion criteria does allow removal of these potential external factors that affect both eNOS activity and left ventricular function, allowing a more ‘pure’ analysis of eNOS polymorphism association with LVEF in early CKD.