Truncus arteriosus is a conotruncal anomaly resulting from complete
failure of septation of the common arterial trunk. In the 1950s and
1960s, it was managed by pulmonary artery banding. In 1967, McGoon first
used a valved allograft conduit to repair truncus
arteriosus.1 Initial results of repair in early
infancy were generally poor, with over 50% mortality. However, results
of repair of truncus arteriosus in older infants, who were managed
medically for the first 6 months of life before surgical correction,
were equally poor due to development of pulmonary vascular disease.
During the last 50 years, neonatal surgical correction of truncus
arteriosus has become routine. Improved surgical techniques, conduit
materials, and postoperative care have made such operations possible at
an operative risk less than that previously reported for banding.
The authors of “Outcomes of truncus arteriosus repair and predictors of
mortality” carried out a retrospective analysis of more than 3000
infants with truncus arteriosus using the National Inpatient Sample
dataset of the Healthcare Cost and Utilization Project database.
Logistic regression was used to identify factors associated with
in-hospital mortality. These included prematurity, stroke, necrotizing
enterocolitis, venous thrombosis, and need for ECMO or cardiac
catheterization during the index hospitalization. The database design of
the study allowed for an impressively large, national cohort. The
ability to report on race and insurance type and outcomes is also quite
interesting, and unfortunately, their findings are consistent with what
has been widely observed in pediatric cardiac surgical
outcomes.2-5 The authors should be praised for their
thoughtful discussion of these findings.
The study’s major limitations are due to the administrative nature of
their database. This database did not provide specifics regarding
patients’ pre/post-operative anatomy (coronary anomalies, truncal valve
insufficiency, etc.) or the surgical repair. Timing of diagnosis,
cardiopulmonary bypass time, concomitant truncal valve or interrupted
aortic arch repair, and conduit size are all factors that have been
previously associated with adverse post-operative outcomes; and none of
these could be included in this analysis.6-8 The cause
of death, i.e. withdrawal of support due to poor neurological prognosis
versus residual disease and progressive cardiorespiratory or multiorgan
failure, also could not be clearly ascertained. Consequently, this
analysis provides an incomplete picture of mortality risk factors in
neonates with truncus arteriosus.
Interestingly, more than 30% of the study sample underwent repair at
>28 days of age. This seems incongruent with today’s
practices and is especially notable since these patients seem to have a
lower mortality. Further, the authors didn’t seem to find the size of
the hospital (possibly correlating with surgical volumes of congenital
heart surgeries) to be a factor in outcomes. This also is at variance
from currently published literature and thinking.
Perhaps the most intriguing finding is the seemingly protective effect
of 22q11.2 deletion, which affected 27.2% of the cohort. Subjects with
22q11.2 deletion had a lower risk of mortality (aOR= 0.54, CI 0.34-0.87,
p=0.011) on multivariate analysis. DiGeorge syndrome was originally
identified in the 1960s, and subsequently linked to a chromosome 22q11.2
microdeletion in 1982 by a multi-disciplinary team, including Dr. Angelo
DiGeorge (Figure 1). Today, 22q11.2 deletion is recognized as the most
common microdeletion syndrome, with a prevalence of more than 1:6000
live births.9 It is present in up to 5% of children
with congenital heart disease, and much more common among those with
conotruncal anomalies like truncus arteriosus.10,11The effect of 22q11.2 deletion on peri-operative morbidity and mortality
remains somewhat uncertain.
Interestingly, the protective effect seen in this cohort does not seem
to be mediated through the identified mortality risk factors. Patient
factors such as prematurity and low birth weight, and perioperative
events such as ECMO, cardiopulmonary resuscitation, mechanical
ventilation, and cardiac catheterization, were similar in the 22q11 and
non-22q11 groups. Lower mortality was observed even though the 22q11.2
deletion group had a higher incidence of non-white race and lower rate
of private insurance. It’s difficult to reconcile this result in the
context of the paper’s broader findings. As the authors point out, the
association between prematurity, lower socioeconomic status, and
non-white race is complex and the contribution of each is difficult to
tease out. As the mortality benefit does not seem related to measured
baseline characteristics or post-operative complications, the authors
suggest that the anatomic details of patients with 22q11.2 deletion such
as potentially lower rates of significant truncal valve insufficiency
may account for their improved post-operative
survival.12 However, additional work will be necessary
to more clearly understand this finding.
Finally, those patients with 22q11.2 deletion had longer
hospitalizations and higher rates of tracheostomy and gastric tube
placement. Perhaps it’s worth pondering then, that although we may offer
these patients a similar chance at life, the quality of life we offer
may be quite different.
Figure
1.
From left to right, Hope H. Punnett, Ph.D., Angelo M. DiGeorge, M.D.,
James B. Arey, M.D., Ph.D., and Harold W. Lischner, M.D. taken 1997.
References
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