The Arch Watch Study: An Integrated Evaluation of Hemodynamics in Infants With Suspected Coarctation of the Aorta

Coarctation of the aorta (CoA) is a potentially life-threatening form of congenital heart disease (CHD) in which an anatomic narrowing of the aortic arch may cause critical aortic arch obstruction (AAO) following closure of the ductus arteriosus (DA). CoA accounts for 6-8% of all CHD and occurs in about 1 in every 1800 babies born in the United States each year. Despite this prevalence, CoA frequently eludes detection on both prenatal imaging and CHD screening. If undiagnosed, infants may present with catastrophic shock, often leading to mortality or severe morbidities. In many cases, the anatomic appearance of the aortic arch in the fetal or early postnatal period raises suspicion for AAO that can only be confirmed by allowing the DA to become restrictive and closely monitoring for hemodynamic changes. However, the process of monitoring hemodynamics during ductal closure (MHDC, i.e. the 'arch watch') is variable across institutions and can be insensitive to critical deficiencies in oxygen delivery in the setting of decreased blood flow, even in subspecialized ICU environments. Current approaches to monitoring hemodynamic changes in neonates with possible AAO revolve around non-invasive measurements of oxygen saturation (i.e. pulse oximetry, near infrared spectroscopy (NIRS)) and tissue perfusion (i.e. femoral pulse strength, urine output, blood pressure). There are no publications which systematically and concurrently assess these trends during this hemodynamic transition, and as such, there are no agreed upon thresholds to alert clinicians that a developing AAO is causing impaired tissue perfusion/oxygenation. Exploration of traditional measures of tissue oxygenation may prove more sensitive and specific at identifying compromise in newborns with critical AAO. For example, certain pulse oximetry waveform characteristics (photoplethysmography, PPG) have shown differences in healthy newborns versus those with CoA. Resonance Raman spectroscopy (RRS) is another validated non-invasive method that assesses peripheral tissue oxygenation in neonates and has been shown to correlate well with invasive markers of tissue oxygenation. The investigators and others have utilized RRS in healthy neonates and in animals to detect tissue hypoperfusion. To test the hypothesis that a validated MHDC process that combines commonly used non-invasive monitoring tools, new components of these traditional tools, and RRS, will have improved sensitivity in detecting critical impairments to tissue oxygen delivery in newborns with suspected critical AAO, the investigators identified the following aims:

Aim I: To assess the reliability of currently deployed non-invasive markers of tissue oxygenation/perfusion (femoral pulse strength, pre- vs. post- ductal blood pressure and saturation gradient, cerebral/renal NIRS, and urine output) in identifying a critical AAO that will need intervention in the newborn period.

Aim II: To explore the sensitivity of PPG to identify critical AAO requiring intervention in the newborn period.

Aim III: To determine the feasibility of assessing oxygen utilization at the tissue level based on RRS during MHDC and examine its predictive capability in identifying those infants with AAO who will require arch intervention in the newborn period.