**4.3 Age**

Several studies showed that older age is an independent predictor of CIN [28]. The reasons for higher risk are multifactorial, which encompasses age-related changes in renal function including decreased glomerular filtration rate, renal concentration ability, and tubular secretion. The presence of multi-vessel coronary artery disease, mandating complex more prolonged PCI, combined with more difficult vascular access that results from tortuosity and calcification of the vessels that frequently requires a greater amount of contrast, and therefore represent additional factors of elevated CIN risk in elderly.

## **4.4 Gender**

Ovarian hormones can have an influence upon the renin-angiotensin system as well as the renal blood flow. In a retrospective study of 8628 patients who underwent PCI, female sex presented an independent risk predictor of CIN (OR = 1.4, p < 0.0001). One-year analyses of outcomes by gender demonstrated a higher mortality rate when compared to males in a cohort of CIN patients (14 vs 10%, p = 0.05) [29].
