White matter injury common after aortic arch surgery in infants

By Eleanor McDermid, Senior medwireNews Reporter

Diagnostic category is the strongest predictor for postoperative white matter injury (WMI) in infants undergoing surgery for congenital heart disease, say researchers.

New WMI after surgery occurred in 42% of infants in the study, with rates ranging from 22% in patients with lesions affecting both ventricles, to about 60% in those who required aortic arch surgery. Aortic arch raised the risk for WMI more than fourfold, after accounting for confounders, report John Beca (Starship Children's Hospital, Auckland, New Zealand) and co-workers.

WMI, in turn, increased mortality risk, with the mortality rate rising with the severity of injury - nearly half of the patients with severe WMI died before the 2-year follow up, whereas just 92% of those with mild WMI died.

The presence of WMI did not affect neurocognitive outcomes when the children were 2 years old; however, most survivors to this age had only mild injury "raising the possibility that any consequences of this may not be discernible at two years of age," say the researchers.

There were 153 infants in the study, who underwent surgery at less than 8 weeks of age. Thirty infants already had WMI, detected on magnetic resonance imaging prior to surgery. This was related to brain maturity, in that the likelihood for pre-existing WMI fell with increasing brain maturity.

Use of cardiopulmonary bypass (CPB) did not itself affect the risk for postoperative WMI, report the researchers in Circulation. However, among the 129 patients in whom it was used, each 1-minute increase in duration of CPB raised the risk for WMI by 2%.

The team says: "The mechanism for this association is unclear, and could either be related to an increased inflammatory response to CPB itself, or perhaps that prolonged CPB might be a surrogate marker for other factors that increase WMI, for example a more challenging operation with the potential for greater hemodynamic instability."

Deep hypothermic circulatory arrest (DHCA), on the other hand, was a significant predictor of new WMI. It increased the risk nearly threefold, and fivefold in infants undergoing aortic arch surgery. Use of DHCA also predicted WHI severity, with the procedure used in all seven infants whose WHI was rated as severe.

Beca et al note that use of DHCA in infants is controversial. It was used in just one center in their study, in 50 patients, and a randomized trial will be needed to shed more light on the issue, they say.

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