Investigators
will test the validity of using an optical non-invasive imaging technique,
which continuously monitor cerebral blood flow and brain oxygenation, for
determining which infants are at greatest risk of developing abnormal cerebral
blood flow fluctuations after open heart surgery. Patients will then have a
brain MRI to correlate this abnormal cerebral blood flow fluctuation with developing
white matter damage in the brain.
Some children born with severe forms
congenital heart defects (CHD) require open-heart surgery during their first
week of life. These infants undergo
cardiopulmonary bypass, with or without cooling of their head and body to
produce circulatory arrest during the surgery. These two strategies may alter
the way cerebral arteries respond to signals from the body, including
alteration of “autoregulation,” the process that normally protects the brain
against blood pressure fluctuations. Normally, smaller blood vessels in the
brain will either dilate or constrict in response to changes in systemic blood
pressure. As a consequence of open heart surgery, however, infants’ cerebral
blood flow fluctuates with changes in systemic blood pressure: low systemic
blood pressure will result in low cerebral blood flow. While 90 percent of infants survive the
operation, more than 50 percent develop an injury to the brain’s white matter,
called periventricular leukomalacia (PVL), which may result in learning
disabilities. Additionally, about 20
percent of the infants have already developed PVL prior to surgery, due to the
heart condition itself.
The investigators hypothesize that
disrupted autoregulation results in an increased risk of developing PVL
following surgery. First, they will use MRI imaging pre-surgically, to quantify
the extent of any existing PVL. Then they will identify those infants with
disrupted autoregulation, using a non-invasive optical imaging technique,
called Diffuse Optical Spectroscopy (DOS). This imaging technique can measure
cerebral blood flow and oxygen saturations continuously through the scalp,
without requiring chemical or radioactive dyes.
Brain MRI will be used thereafter to obtain pilot data on the effect of
disrupted autoregulation on the risk for developing PVL (or worsening of
existing PVL white matter damage) during the post-operative period. By
correlating impaired autoregulation of cerebral blood flow with post-surgical
MRI they will identify infants with the highest risk for post-operative
PVL.
Significance: If DOS is found to be a valid means for
identifying infants at risk for PVL post-surgically, DOS will become a vital
tool for post-surgical monitoring to prevent brain injury. Furthermore, it’s
use could be extended to the care of vulnerable infant populations such as the
premature infant.
