(Circulation. 1999;100:II-167.)
© 1999 American Heart Association, Inc.
Surgery for Congenital Heart Disease |
Early Survival of Infants Weighing 2.5 Kilograms or Less Undergoing First-Stage Reconstruction for Hypoplastic Left Heart Syndrome
From the Divisions of Pediatric Cardiothoracic Surgery and Pediatric Cardiology, Cardiac Center, Children’s Hospital of Philadelphia, Philadelphia, Penn.
Correspondence to Thomas L. Spray, MD, Children’s Hospital of Philadelphia, Division of Cardiothoracic Surgery, 34th & Civic Center Blvd, Suite 8527, Philadelphia, PA 19104-4399.
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Abstract |
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Background—Results of staged palliation for hypoplastic left heart syndrome (HLHS) have improved in recent years; however, certain risk factors have been associated with decreased survival rates.
Methods and Results—We retrospectively reviewed the medical
records of 67 patients weighing 
2.5 kg undergoing the first stage
of reconstructive surgery at our institution between January 1, 1990,
and December 31, 1997. HLHS was present in 45 patients, complex
double-outlet right ventricle in 10, unbalanced AV canal in 5,
tricuspid atresia with transposition of the great vessels in 4, and
other diagnoses in 3. Mean age at surgery was 10.1±10.7 days (median,
8 days), and mean weight was 2.2±0.3 kg (median, 2.2 kg). Fourteen
patients weighed 2.0 kg, and 2 patients weighed 1.5 kg. Early
mortality (death within 30 days or before hospital discharge) was 51%
(34 of 67). No patient, procedural, or time-related variables
correlated with increased mortality. However, there was a trend toward
increased mortality with increased cardiopulmonary bypass time
(P=0.076) and decreased preoperative
ventricular performance
(P=0.139).
Conclusions—These findings suggest that low weight alone in a patient with HLHS or an anatomic variant should not be considered a contraindication to staged reconstructive surgery.
Key Words: heart defects, congenital • surgery • risk factors
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Introduction |
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Early survival after the first stage of palliative surgical reconstruction for hypoplastic left heart syndrome (HLHS) has steadily improved since Norwood et al1 and Doty et al2 first described the operation in 1979. In a recent multi-institutional review from the Congenital Heart Surgeons Society (CHSS), 1-month survival for stage 1 palliation for aortic atresia was 64%, with better results achieved at 2 "low-risk" institutions.3 Bove and colleagues4 from the University of Michigan recently reported hospital survival rate of 76% after stage 1 palliation. Results from our own institution are similar, with an overall early survival rate of 73% in >171 cases between January 1, 1995, and December 31, 1998.
Early survival for HLHS is significantly less than for other cardiac defects requiring neonatal repair. Anatomic variation, size of the ascending aorta, age at surgery, tricuspid valve function, ventricular function, low birth weight, associated noncardiac anomalies, and other variables have been suggested as possible predictors of mortality for patients undergoing staged reconstruction for HLHS.5 6 7 8 9 10 11 Identification of such risk factors would ideally lead to increased survival, either as a result of preoperative management strategies to reduce these "high-risk" characteristics or by leading to referral for cardiac transplantation rather than staged reconstruction to the Fontan operation for a specific subset of patients.
There have been only a few recent reports on the outcome of low-weight
(<2.5 or 2.0 kg) infants undergoing cardiac
surgery.12 13 14 15 The overall early survival rate for infants
undergoing corrective or palliative surgery for congenital heart
defects in these studies was acceptable (80% to 87%) but still lower
than for babies of normal weight. These studies included few patients
with HLHS. Because of the potential additive risks of low weight and
complicated neonatal palliative cardiac surgery, we evaluated the
results of first-stage reconstruction in infants weighing 2.5 kg to
describe this population and to attempt to identify factors predictive
of early mortality.
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Methods |
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The cardiopulmonary bypass (CPB) records of cardiac surgical cases performed at the Children’s Hospital of Philadelphia between January 1990 and December 1997 were reviewed to identify babies weighing
2.5 kg at the time of stage 1 reconstruction for HLHS or an
anatomic variant (see Table 1
).
Among the 69 patients identified, 67 had complete records and are
included in this study. Patient data were compiled by review of
clinical records, preoperative echocardiographic
reports, perfusion records, operative notes, and autopsy
reports.
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Stage 1 reconstruction at our institution includes aortic arch augmentation with cryopreserved homograft, creation of an aortopulmonary shunt, and an atrial septectomy when necessary to ensure adequate interatrial mixing. Early mortality was defined as death within 30 days or before hospital discharge. Prematurity was defined as birth at a gestational age of <37 weeks. Appropriateness of weight for gestational age was assessed with the Growth Record for Infants (Abbott Laboratories). Time on CPB was calculated as circulatory arrest time plus time on CPB.
Characteristics examined as potential predictors of mortality are shown
in Table 1
. Operations were performed by 4 surgeons, and because
the variable "operating surgeon" was essentially collinear with
"year of operation," only the latter variable was
analyzed. Logistic regression or 
2 was
used to analyze the dichotomous variables. The remaining
characteristics were analyzed as continuous variables.
Results of univariate analysis did not support
proceeding to multivariate analysis. All
statistical tests were carried out by use of Stata 5.0 software.
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Results |
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Characteristics and anatomic diagnoses of the 67 patients who met study criteria are listed in Table 2
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Premature birth occurred in 39 of 67 patients (58%). Weight was
appropriate for gestational age in 44 patients (79%), low for
gestational age in 11 (16%), and high for gestational age in only 2.
Fourteen patients (21%) weighed 2 kg at the time of surgery. Even in
patients in whom surgery was performed after the median age, there was
no appreciable weight gain or loss before surgery. Specific genetic
syndromes were identified in 5 patients, including 2 infants with
Turner’s syndrome and 1 each with Rubinstein-Taybi syndrome, 22Q
deletion, and CHARGE syndrome.
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Early mortality was 51% (34 of 67). Causes of hospital mortality are
listed in Table 3. One patient died after
discharge but before 30 days of life. Two thirds of the deaths were
secondary to cardiac causes, defined as a chart description of
cardiopulmonary arrest, arrhythmia, or
pulmonary overcirculation preceding death. Infection and sepsis
were a factor in all noncardiac deaths. Necrotizing enterocolitis was
present before surgery in 6 patients, and 3 survived to hospital
discharge. In addition, 2 patients died of perforated viscus (1 colon
and 1 appendiceal) in the postoperative period. Pulmonary
infections were the primary cause of death in 4 patients. Evidence of
meningitis at autopsy was present in 2 patients. The median time of
death from cardiac causes was 1 day after surgery (range, 0 to 19
days); for noncardiac causes, it was 17 days (range, 4 to 160
days).
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In univariate analysis, no patient, procedural, or time-related variable was predictive of mortality in this cohort. However, there was a trend toward higher mortality with longer CPB times (P=0.07). In addition, all 3 patients with severely decreased ventricular function and all 3 patients with severely obstructed pulmonary venous drainage died. Three of the 5 infants with genetic syndromes, 2 with Turner’s syndrome, and 1 with Rubinstein-Taybi syndrome died.
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Discussion |
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Although improvements in surgical technique and perioperative care have led to increased survival after surgical reconstruction for HLHS, operative mortality after the first stage is still high (9% to 47%).4 6 10 Many investigators have attempted to identify factors predictive of death after the Norwood procedure. Identification of high-risk characteristics would aid in the management of these patients and may help in deciding more precisely which patients should be listed for transplantation and which should undergo staged reconstruction.16 Prematurity and low weight in patients with HLHS have been found to be risk factors for higher mortality in some reports. However, contemporary reviews of low-weight neonates with a wide variety of lesions requiring CPB for repair have suggested that low weight alone is not a contraindication to early repair.12 13 14 In the present study, survival was 47% for low-weight infants undergoing stage 1 reconstruction. Overall survival for stage 1 reconstruction at our institution is 74%. Within the cohort of low-weight infants, weight at the time of stage 1 reconstruction for HLHS had no effect on survival. In addition, no statistically significant increase or decrease in weight was evident in patients in whom surgery was delayed.
Only a few studies have focused on the influence of weight on survival
after CPB.12 14 17 18 Pawade and
associates14 from the Royal Children’s Hospital in
Melbourne analyzed risk factors for mortality in infants
weighing <2.5 kg undergoing CPB and compared them with a similar group
undergoing CPB with weights >2.5 kg. There were 8
univentricular repairs and 52 biventricular
repairs. HLHS was present in only 4 of the low-weight infants.
There were 946 patients in the control group. Early mortality in the
low-weight group was 16.5% compared with 7.5% for the overall
population (P<0.006). Predictors of mortality were
preoperative metabolic acidosis, univentricular
repair, and longer CPB time. Of the 4 patients with HLHS, 2 were early
survivors.14 Rossi and colleagues13 recently
reviewed the outcomes of cardiac operations in 30 infants weighing 2
kg at the Mount Sinai Hospital in New York. Hospital survival was 83%,
with no difference in mortality rates based on age, weight, or type of
procedure. HLHS was present in 4 patients; 3 of these were early
survivors.
Bove and Lloyd3 reviewed 158 patients undergoing staged reconstruction from 1990 through 1995 and identified several risk factors for early death, including age >1 month, pulmonary venous obstruction, significant noncardiac congenital anomalies, gestational age <35 weeks, and birth weight <2.5 kg. Hospital survival for the 31 patients with these high-risk characteristics was 42%, which was significantly lower than the 86% survival rate seen in the remaining 127 patients (P=0.0001).3
Forbess and colleagues17 reviewed 212 consecutive patients undergoing stage 1 reconstruction at the Children’s Hospital of Boston between 1983 and 1993. Operative mortality in this group was 46.2%. Patients weighing <3 kg were at higher risk for hospital death, and weight <3 kg was an independent risk factor for mortality in the multivariate analysis. The authors suggested that low-weight patients might be best served by referral for transplantation.17 However, in the CHSS study, low birth weight was found to be an incremental risk factor for death in both staged reconstruction and heart transplantation protocols.3 Overall experience of transplantation in low-weight infants is limited. In the largest series reported of infants transplanted for HLHS at Loma Linda (142 patients of 176 listed), the average weight was 3.7±0.8 kg (range, 2.0 to 6.4 kg; median weight, 3.6 kg).19
Traditional experience with cardiac surgery in small infants has suggested that weight is indeed a risk factor for early intervention.12 13 14 18 The reasons for the increased mortality are probably multifactorial. The neonatal heart is less compliant that the mature heart and is thought to be less capable of handling a volume load.20 21 The immature pulmonary vascular bed can make the postoperative course unpredictable, and underdeveloped renal and hepatic functions impair fluid balance.12 13 14 15 22 Patients born prematurely may have hyaline membrane disease and are at risk for necrotizing enterocolitis.13 22 In addition, the germinal matrix of the premature infant is more susceptible to hemorrhage and neurological complications from heparinization and CPB.18 Newborns of small size undergoing the Norwood procedure present the additional technical challenges of cannulation, cerebral protection, aortic arch reconstruction for extremely small vessels, and selection of an appropriate shunt size to provide adequate but not excessive pulmonary blood flow while allowing for sufficient growth.
While this may be the largest reported series of small infants undergoing stage 1 reconstructive surgery, the statistical power to define significant predictors of mortality is limited. For example, the influence of severely diminished ventricular performance, obstructed pulmonary venous drainage, and prolonged CPB times may be underestimated because of the small number of patients in the series with those characteristics. As in previous reports examining the influence of weight on cardiac surgery, weight differences within this group had no effect on mortality.12 13 14 Because of the entry criteria of the study, we did not identify patients who might have been born at <2.5 kg but grew preoperatively to weigh more than this at the time of surgery or patients who were not referred for surgery because of low birth weight. Yet in this review, patients in whom surgery was delayed did not experience a statistical increase or decrease in weight before the date of surgery, similar to previous reports.13 14 This finding suggests that a delay in surgery to allow weight gain is not justified and exposes the patient to prolonged risks of pulmonary overcirculation, long-term mechanical ventilation, and other ICU-related complications.13 14 The study design also does not reveal how many infants at various postgestational ages might have died before surgery. Within the limitations of this study, however, age at operation did not influence survival. Previous studies have not compared age-weight appropriateness and outcome in cardiac surgery, but in this study, being born small for gestational age did not predict a higher mortality.
Although low-birth-weight infants with congenital cardiac defects, including HLHS, are likely to be at a higher risk for postoperative death and complications than their normal-size counterparts, current experience does not suggest that waiting to obtain a minimum weight before surgery improves outcome. Therefore, a delay in surgical intervention in the hope of somatic growth is not warranted. Survival for low-weight infants undergoing stage 1 reconstruction in general is decreased compared with larger babies having the same operation at the same institution; however, the absolute survival rates are acceptable by national standards. Weight alone should not be considered a contraindication to staged surgical reconstruction in infants with HLHS.
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Acknowledgments |
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This work was supported in part by the Daniel M. Tabas Endowed Chair in Cardiothoracic Surgery.
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