Cardiac repair surgeries performed on the patients were ranked from 1 to 4 in increasing complexity, with 43% being listed at categories 3 or 4, and including some more complex than category 4. The two most commonly seen procedures (72%) were closure of a hole between the atria (upper chambers of the heart) or between the ventricles (lower chambers of the heart).

Both the cardiac repair surgery and the non-surgery subjects were followed medically for up to 13 years, with data collected until death, diagnosis of ESKD or the end of the study (March 31, 2015). Of the 3,600 subjects who had surgery, 140 (3.89%) died and 52 (1.44%) developed ESKD. These numbers were significantly higher than those among the 36,000 who did not have CHD or surgery. In the latter group, 35 (0.10%) died -- a rate four times lower than the CHD patients -- and six (0.02%) developed ESKD, a rate nearly nine times lower.

The mortality incidence rate -- the total number of deaths from all causes during the study period divided by the cumulative time in years for all of the patients participating (known as person-years) -- for the cardiac repair surgery subjects was 69 deaths per 10,000 person-years. By contrast, the rate for the nonsurgery group was two deaths per 10,000 person-years.

The researchers say this indicates that children who had cardiac repair surgery at a young age were 34.5 times more likely to die within a decade after that surgery than those in the general population.

The ESKD incident rates also showed significantly higher risk of developing kidney failure as an outcome of early age CHD repair surgery. For the surgery patients, the incident rate was 26 cases per 10,000 person-years compared with 0.3 cases per 10,000 person-years -- a difference of 867-to-1.

"We also saw that the more complex the cardiac surgery performed, the higher the risk of both death from any causes and for developing ESKD," Parikh says. "In the most extreme case, patients who had surgery to correct a hypoplastic left heart -- a severe defect where the left side of the heart is underdeveloped -- were 10 times more likely to develop ESKD than those who had other congenital heart conditions remedied."

Parikh cautions that medical records studies that "look back" at patient histories have limitations, but says that the research team's findings should be useful in guiding better long-term care for those at highest risk for ESKD and shortened lifespans.

"For now, we recommend that children who have cardiac repair early in their lives be monitored more closely for signs of developing ESKD," he says. "Future research should look for early biomarkers of kidney damage and develop computer models that could help us identify those most at risk."

Cardiology Homepage