An increase in the NT-proBNP concentration and a decrease in the LVEF level may be caused by a patient's increased venous pressure, diastolic filling pressure, and abnormal ventricular systolic function, and the occurrence of these conditions may in turn antagonize the expansion of circulating blood vessels and act on the renin–angiotensin–aldosterone system, which may lead to impaired kidney function. This evidence concerns the gene REN and medical procedure.