Women More Likely Than Men to Develop CIN after Angiography

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Women have a significantly greater risk for developing contrast-induced nephropathy (CIN) after coronary angiography than men, according to a study presented April 27, 2011 at the National Kidney Foundation Spring Clinical Meetings in Las Vegas, NV.

Investigators led by Javier Neyra, MD, of Henry Ford Hospital (Detroit, MI), and colleagues followed 1,211 patients who underwent coronary angiography from January 2008 to December 2009. Of these, 39.7% had estimated glomerular filtration rate (eGFR) values between 15 and 59 mL/min/1.73m². The remaining 60.3% had eGFR values of at least 60 mL/min/1.73m². Women accounted for 43.8% of the study population (n = 530).

CIN was defined as an increase in creatinine greater than 25% from baseline, absolute increase in creatinine of at least 0.5 mg/dL, or decrease in eGFR of at least 25% within 72 hours after contrast exposure.

Overall, CIN occurred in 19.8% of women and 13.6% of men (P = 0.004). After adjustment for possible confounders, multivariable analyses found that female gender independently predicted CIN risk. Other predictors included the use of furosemide and contrast media volume greater than 100 mL (table 1).

Table 1. Risk Factors for Development of CIN

Additionally, female gender significantly increased CIN risk for patients with eGFR values of at least 60 mL/min/1.73m² (OR 1.94; 95% CI 1.25-2.99, P = 0.003) but not for those with lower eGFR values (OR 1.09; 95% CI 0.66-1.81, P = 0.742).

Influence of Gender is Novel Finding

In a telephone interview with TCTMD, Dr. Neyra said previous studies that found a difference in CIN between men and women attributed the finding to the fact that women tend to have more comorbidities and present at older ages, as opposed to gender itself being a risk factor.

“In our study we adjusted for confounders [such as] age, diabetes, hypertension, and we [isolated gender] in the logistic regression analysis,” he said. “Why this is the case is not clear. It is hypothesized that estrogen may play a part. Another suggestion is that there may be a different way that women react to contrast as opposed to the way men react.”

A further possibility is that women’s smaller size is a factor, Dr. Neyra suggested. “If they are small, both in weight and height, and receive the same amount of contrast as a man who is much larger, it could be hypothesized that the contrast dose is too high for the body size and may present risk,” he said. “We don’t have a universal formula to adjust the contrast dose for a female’s weight and height and that is something that needs to be looked into further.”

The study adjusted for contrast volume using a contrast ratio that takes into account weight, but not height, Dr. Neyra noted, adding that the amount of contrast that men and women in the study received was essentially the same.

“Based on these results, we are convinced there may be some intrinsic gender risk,” Dr. Neyra said. “Our hope is to bring more interest and research to this area. There are many things about the pathogenesis of contrast-induced nephropathy that we still don’t know.”

Different from Birth?

According to Peter A. McCullough, MD, MPH, of St. John Providence Health System (Detroit, MI), female biology probably holds some intriguing explanations.

“The study brings up this issue of nephron mass in that it’s believed that women actually have a fewer number of functioning kidney nephron units,” he said in a telephone interview with TCTMD. “Because of that fact, if a woman has diabetes and hypertension and loses nephrons, since she started out with fewer of them than a man would have, she is more vulnerable to kidney injury.”

Interestingly, the number of nephrons a person has is related to birth weight and is set at birth, Dr. McCullough added, explaining, “This [set number of nephrons] is carried through life and ultimately translates to vulnerability.”

He proposed that future research aimed at testing this theory might go back and look at birth weights in women who develop CIN to see if they were particularly small or premature. Finally, Dr. McCullough said he believes the subanalysis finding that female gender increases the risk of CIN in patients with eGFR values of at least 60 mL/min/1.73m² has not been demonstrated previously and may help in future preventative measures.

Source:

Neyra J, Jacobsen G, Novak JE. Are women at higher risk to develop radiocontrast-induced nephropathy (RCIN) following coronary angiography? Presented at: National Kidney Foundation Spring Clinical Meetings. April 27, 2011.

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