Impaired renal function is associated with worse clinical outcomes in patients with LV systolic dysfunction (LVSD) and heart failure. Renin-angiotensin-aldosterone system (RAAS) inhibitors provide clinical benefit in these settings and often worsen renal function. It is not clear whether worsening renal function (WRF) in patients exposed to these agents predicts a worse prognosis or merely reflects the pharmacological action of the drug on the kidney.