Published online before print September 15, 2008, doi: 10.1161/CIRCULATIONAHA.107.741579
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(Circulation. 2008;118:1410-1418.)
© 2008 American Heart Association, Inc.
Congenital Heart Disease |
Two-Year Survival and Mental and Psychomotor Outcomes After the Norwood Procedure
An Analysis of the Modified Blalock-Taussig Shunt and Right Ventricle–to–Pulmonary Artery Shunt Surgical Eras
From the Department of Pediatrics (J.A., A.R.J., C.M.T.R., J.D.D., I.M.R.), School of Public Health (I.A.D.), and Department of Surgery (D.B.R., I.M.R.), University of Alberta, Edmonton, Alberta, Canada; Pediatric Rehabilitation Outcomes Evaluation and Research Unit (C.M.T.R.), Glenrose Rehabilitation Hospital, Edmonton, Alberta, Canada; and Department of Pediatrics (R.S.S.), University of Calgary, Calgary, Alberta, Canada.
Correspondence to Ari Joffe, MD, FRCP(C), Department of Pediatrics, 3A3.07 Stollery Children’s Hospital, 8440 112 St, Edmonton, Alberta, Canada T6G 2B7. E-mail ajoffe{at}cha.ab.ca
Received September 24, 2007; accepted July 25, 2008.
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Abstract |
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Background— The Norwood procedure for stage 1 palliation of hypoplastic left heart syndrome is performed with either the modified Blalock-Taussig (MBTS) or the right ventricle–to–pulmonary artery (RVPA) shunt. In our institution, surgical practice changed from use of the MBTS to use of the RVPA shunt in 2002. We analyzed survival and mental and psychomotor outcomes of the 2 consecutive surgical eras.
Methods and Results— Between September 1996 and July 2005, 94 neonates with hypoplastic left heart syndrome underwent the Norwood procedure. Patients were recruited as neonates and followed up prospectively. Health, mental, and psychomotor outcomes (Bayley Scales of Infant Development-II) were assessed at 2 years. The study subjects were from the Norwood-MBTS era (n=62; 1996 to 2002) or the Norwood-RVPA era (n=32; 2002 to 2005). In the MBTS era, early and 2-year mortality rates were 23% (14/62) and 52% (32/62); the mean (SD) mental and psychomotor developmental indices were 79 (18) and 67 (19). In the RVPA era, early and 2-year mortality rates were 6% (2/32) and 19% (6/32); the mean (SD) mental and psychomotor developmental indices were 85 (18) and 78 (18). The 2-year mortality rate (P=0.002) and the psychomotor developmental index (P=0.029) were improved in the more recent surgical era. On multivariable Cox regression analysis, postoperative highest serum lactate independently predicted 2-year mortality in the MBTS and RVPA eras.
Conclusions— Analysis of 2 consecutive surgical eras of hypoplastic left heart syndrome patients undergoing the Norwood procedure showed a significant improvement in 2-year survival and psychomotor development in the more recent era. Adverse neurodevelopmental outcome in this patient population remains a concern.
Key Words: heart defects, congenital • pediatrics • mortality • prognosis
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Introduction |
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The Norwood procedure for palliation of hypoplastic left heart syndrome (HLHS) was first described in 1980,1 and it has since undergone several modifications that have led to improved patient mortality and morbidity. Nevertheless, hemodynamic instability and postoperative death remain concerns. Unpredictable variability in pulmonary vascular resistance leading to overcirculation and coronary insufficiency is thought to be an important factor in the death of patients who have undergone the Norwood procedure with the modified Blalock-Taussig shunt (MBTS). More recently, the right ventricle–to–pulmonary artery (RVPA) shunt modification of the Norwood procedure was revived.2 This modification offers the advantage of separating the effects of changes in pulmonary vascular resistance from the systemic circulation while providing adequate pulmonary blood flow. This may lead to better survival rates. In 2003, Sano et al3 reported their positive experience with the RVPA shunt modification of the Norwood procedure. Since then, several centers have adopted the new technique; however, reports in the literature are conflicting as to the surgical and interstage survival differences.4–10 To the best of our knowledge, there are no reports in the literature comparing neurodevelopmental outcome between the MBTS and RVPA modifications of the Norwood procedure. We report our experience, with analysis of 2 consecutive surgical periods separately and evaluation of survival and mental and psychomotor outcomes at 2 years of age for each of the 2 study periods.
Clinical Perspective p 1418
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Methods |
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The present cohort study is part of a prospective interprovincial, inception-cohort outcomes follow-up project conducted in 4 provinces in Western Canada. As described previously,11,12 infants
6 weeks of age were identified at the time of complex cardiac surgery and were followed up prospectively. In the present study, we included all patients with the diagnosis of HLHS or its variants who had undergone the Norwood procedure between September 1996 and July 2005. All surgeries were performed at the Stollery Children’s Hospital, Edmonton, Alberta, Canada. Predetermined demographic, preoperative, intraoperative, and postoperative variables were collected prospectively.11,12 Long-term follow-up was discussed with parents or guardians once survival was probable, and with their written consent, contact was made with their respective follow-up clinics at the tertiary site of origin.
Early Childhood Assessments
Outcome assessments were completed when the children were between 18 and 24 months of age. History and physical measurements were obtained as described previously.11,12 The family socioeconomic status was determined with the Blishen Index.13 Maternal education was indicated by years of schooling. Pediatricians experienced in neurodevelopmental follow-up examined each child for evidence of cerebral palsy14 or visual impairment, defined as corrected visual acuity in the better eye of <20/60.11,12 Hearing was evaluated by experienced certified pediatric audiologists in soundproof environments as described previously.11,12 Sensorineural hearing impairment was defined as responses in the better ear of >40 dB at any frequency from 250 to 4000 Hz. Five certified pediatric psychologists and psychometrists administered the Bayley Scales of Infant Development-II15 in their respective referral institutions. The Bayley Scales of Infant Development-II is a widely accepted standardized outcome measure used in neonatal follow-up clinics that yields separate mental developmental index (MDI) and psychomotor developmental index (PDI) standardized scores with a mean of 100 and SD of 15. Developmental indices of <70 (2 SD below the mean) indicated mental or psychomotor delay. Within a normative sample, 2.27% of children have scores <70.
Variables
Demographic, preoperative, intraoperative, postoperative, and overall variables used in the study are listed in Table 1
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Outcomes
The primary outcomes of interest were (1) mortality (early, interim, and 2-year) and (2) mental and motor development. Early mortality was defined as death that occurred within 30 days of the Norwood procedure or at any time in the hospital if the patient was never discharged. Interim mortality was defined as death that occurred after the above-defined early mortality period and before the bidirectional cavopulmonary anastomosis surgical procedure. Two-year mortality included all deaths that occurred between the Norwood procedure and the 2-year birth date, inclusive. Secondary outcomes included morbidity, defined by the health and growth variables listed in Table 2.
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Statistical Analysis
Continuous variables are presented as mean (SD) and were analyzed with the Student t test. Categorical variables are presented as counts and percentages and were analyzed with Fisher exact test. Actuarial survival analysis was performed with Kaplan-Meier estimates with log-rank comparison of cumulative survival by study era. Mortality and mental and psychomotor development were analyzed for the 2 study groups separately. To screen for variables associated with early and 2-year mortality, we used univariate logistic and Cox regression analysis, respectively, and included all relevant variables from Table 1
. Multivariable logistic and Cox regression analysis included variables that were significant at P0.10 in the corresponding univariate analysis. To screen for variables associated with MDI and PDI, we used univariate logistic regression models and included all relevant variables from Table 1. Multiple linear regression models consisted of variables found to be significant at P0.10 in the univariate analysis, after screening for multicollinearity. Regression model results are reported as hazard ratios or effect sizes with confidence intervals and 2-sided P values. Statistical analyses were performed with SAS version 9.1 (SAS Institute Inc, Cary, NC).
The authors had full access to and take full responsibility for the integrity of the data. All authors have read and agree to the manuscript as written.
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Results |
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Description of Cohort
Ninety-four patients with HLHS or its variants underwent the Norwood procedure between September 1996 and July 2005. Patients with additional significant cardiac diagnoses included 1 with total anomalous pulmonary venous drainage and 1 with double-outlet right ventricle in the MBTS group, as well as 2 with unbalanced atrioventricular septal defects in the RVPA group. Complete follow-up data were available for all patients. The 2 study groups are from 2 consecutive surgical eras. The first was from September 1996 to September 2002 and included 62 patients having the Norwood procedure performed with the MBTS (MBTS era). The second was from October 2002 to July 2005 and included 32 patients having the Norwood procedure modified with the use of the RVPA shunt (RVPA era). Other significant changes that took place during the transition of surgical eras were (1) the use of regional cerebral perfusion and (2) the home monitoring program (as described by Ghanayem et al16).
Group Comparison
The demographic, preoperative, operative, postoperative, and overall variables compared between the MBTS and RVPA eras are shown in Table 1. Noncardiac diagnoses are listed in Table I in the online-only Data Supplement.
Primary Outcomes
Mortality
Early mortality was 23% (14/62) for the MBTS era and 6% (2/32) for the RVPA era (P=0.079). Interim mortality was 21% (13/62) for the MBTS era and 13% (4/32) for the RVPA era (P=0.403). Mortality by 2 years of age was 52% (32/62) for the MBTS era and 19% (6/32) for the RVPA era (P=0.002). Kaplan-Meier estimates of survival time after the Norwood surgery show significantly better survival at 2 years of age for the RVPA era than for the MBTS era (P=0.003; Figure 1).
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For early mortality, multiple logistic regression analysis was performed only for the MBTS era, adjusted for variables listed in Table 1 (see online-only Data Supplement Table II for univariate analysis). Highest lactate on postoperative days 2 to 5 (odds ratio 1.14, 95% confidence interval 1.03 to 1.27, P=0.016) and male sex (odds ratio 0.23, 95% confidence interval 0.05 to 1.07, P=0.062) were associated with early mortality. When the multiple logistic regression was repeated with the exclusion of postoperative variables, only male sex was associated with early mortality. Multiple regression analysis for early mortality was not performed for the RVPA era, because the outcome consisted of only 2 deaths.
For mortality by 2 years of age, multivariable Cox regression analysis was performed for the MBTS era and the RVPA era separately and adjusted for variables listed in Table 1 (see online-only Data Supplement Table III for univariate analysis). The results are shown in Table 3.
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Mental and Psychomotor Outcomes
Survivors were assessed with the Bayley Scales of Infant Development-II at 21.4 (4.2) and 21.9 (4.5) months in the RVPA and MBTS eras, respectively (P=0.695). The mean MDI scores in the RVPA and MBTS eras were not statistically significantly different (Table 2). The mean PDI scores were significantly higher and the incidence of psychomotor delay (score <70) was significantly lower in the RVPA era (Table 2; Figure 2).
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Multiple linear regression analysis, performed for the MBTS era and the RVPA era separately, included variables found to be significantly related to mental and psychomotor scores (P0.10) in the univariate logistic regression analysis (online-only Data Supplement Table IV). The results are shown in Table 4.
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Secondary Outcomes
Overall, no difference was found in the growth and health outcomes as listed in Table 4, except for sensorineural hearing loss, which occurred more often in patients in the RVPA era. Six patients (5 with RVPA shunt) required amplification (Table 2).
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Discussion |
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The incidence of HLHS is 1 in 4000 to 6000 live births. A natural history study reported a 95% mortality rate in the first month of life for unoperated HLHS.17 The past 2 decades have been witness to improvements in the care of the patient with HLHS. Advances have allowed marked improvement in the survival of these infants, and attention has shifted to their neurodevelopmental outcome. To the best of our knowledge, this is the first report describing the 2-year general and neurodevelopmental outcomes of infants with HLHS undergoing the MBTS and RVPA modifications of the Norwood procedure. We found a pattern of improvement in intraoperative management and improved early postoperative variables in the RVPA era, which likely reflects a more stable hemodynamic status. Several other authors have reported on the favorable hemodynamics of the RVPA modification of the Norwood procedure compared with the MBTS.18–23 Moreover, we showed significant differences in mortality and psychomotor developmental outcome between the 2 surgical eras.
Early Mortality
We found a trend to lower early mortality in the more recent RVPA surgical era; however, the present study was not powered to show this difference as statistically significant. Pizarro et al4 and Griselli et al8 reported a similar decrease in early mortality. On the other hand, other series identified no difference in early mortality between the MBTS and RVPA groups.5,7,10 In the late 1990s, reports on early mortality after the Norwood-MBTS ranged from 7% to 29%.24–27 A more recent study reported a 21% early mortality, with noncardiac abnormalities and birth weight <2.5 kg identified as risk factors.28 In the present study, multiple logistic regression analysis showed that postoperative serum lactate and male sex were independent predictors of early mortality in the MBTS era. Cheung et al29 previously identified postoperative lactate as a predictor of early mortality after neonatal surgery.
Interim Mortality
The difference in interim mortality did not reach statistical significance. Most comparative reports of interim death demonstrate a decreased incidence in the RVPA patient population compared with the MBTS population.4–6 Previous reports analyzing patients undergoing the Norwood-MBTS in the 1990s reported interim mortality rates of 13%24 and 15%.25 Overall, interim mortality appears to be declining. It is still not negligible, however, and remains an important clinical concern. The benefit of the home surveillance program in decreasing interim mortality documented by others16 could not be confirmed in the present study cohort.
Two-Year Mortality
We found a significantly lower mortality rate by 2 years of age in the RVPA era. In the late 1990s, MBTS mortality rates were reported at 28%24 and 34%.27 Sano et al,30 in a multi-institutional study, reported a 37% 2-year mortality rate for an RVPA cohort. Two recent studies reported similar MBTS versus RVPA late mortality rates of 32% versus 30%5 and 31% versus 27%,10 respectively. In the present study, multivariable Cox regression analysis identified postoperative serum lactate and base deficit as statistically significant predictors of mortality by 2 years of age in the MBTS era. In the RVPA era, a higher postoperative serum lactate was the only independent predictor of mortality by 2 years of age.
Bidirectional Cavopulmonary Anastomosis
The bidirectional cavopulmonary anastomosis procedure was performed at a younger age in the RVPA era. This earlier timing has been observed by others5,7,10 and is thought to be due to earlier cyanosis.7 Another study showed no difference in the timing of the bidirectional cavopulmonary anastomosis between the MBTS and RVPA groups.31 The earlier timing of bidirectional cavopulmonary anastomosis may also be related to a gradual change in the medico-surgical practice toward earlier relief of the right ventricular volume overload and shortening of the high-risk interim period. There has been some theoretical concern about poor growth of the pulmonary arteries after RVPA; however, recent studies showed that the RVPA conduit provided better growth of the pulmonary arteries than the MBTS.31,32
Mental and Psychomotor Outcomes
Some infants undergoing complex surgery for congenital heart disease have an abnormal neurodevelopmental outcome when evaluated at as early as 1 or 2 years of life.11,33–35 Mahle et al36 evaluated 115 of 138 eligible surgically palliated school-aged and adolescent children with HLHS using mailed questionnaires. They found that performance correlated with the incidence of preoperative seizures and cumulative duration of cardiopulmonary bypass. Standardized neurocognitive evaluation was performed on 28 of 34 patients, who were eligible if they lived within a local geographic region and if English was their primary language used at home. Eighteen percent (5/28) had IQ scores in the mentally retarded range. Other studies have reported the significant risk for adverse neurodevelopmental outcome in HLHS patients.37–40 One study showed the duration of DHCA to be inversely associated with performance IQ in a small cohort of 14 patients.39 For children after Norwood MBTS surgery, a strong correlation has been found between the MDI at 18 to 24 months of age and full-scale intelligence scores at 5 years of age.41
In the present study cohort, MDI scores and the incidence of mental delay did not improve in the recent surgical era. Linear regression analysis identified a lower socioeconomic status and prolonged hospitalization at the time of the Norwood procedure as independent predictors of lower mental scores in the MBTS era. In the RVPA era, lower PaO2 and longer ventilation time (days) before the Norwood procedure, as well as longer DHCA time during the Norwood procedure, were independent predictors of lower mental scores. Robertson et al11 previously identified preoperative ventilation as a significant predictor of neurodevelopmental outcome after neonatal open heart surgery. Longer hospitalization was identified previously as an independent predictor of lower full-scale IQ scores in a cohort of school-aged HLHS patients who had undergone either the Norwood procedure or heart transplantation.42
The present results showed a significant improvement in PDI scores and a lower incidence of psychomotor delay in the RVPA era. Linear regression analysis identified only male sex as an independent predictor of lower psychomotor scores in the MBTS era. In the RVPA era, longer overall hospitalization and the need for cardiopulmonary resuscitation at any time before or after the Norwood procedure were independent predictors of a lower psychomotor score.
The use of regional cerebral perfusion was not a significant predictor of MDI or PDI scores in the MBTS era. Regional cerebral perfusion was used, however, in all patients in the RVPA era and thus could not be analyzed as a predictor. A recent retrospective study43 and a recent randomized clinical trial44 compared the neurodevelopmental outcome of patients undergoing the Norwood procedure with and without low-flow regional cerebral perfusion and showed no difference in the Bayley Scales of Infant Development-II scores when assessed at 1 year of age.
Sensorineural hearing loss occurred more commonly in the RVPA era. This degree of hearing loss, even if amplified, may have reduced the MDI scores among RVPA survivors. The cause of the hearing loss remains unknown.45 An unexpectedly high prevalence of sensorineural hearing loss has been reported previously among children with congenital heart defects.46
The results of the present study must be interpreted in the context of its nonrandomized study design and the use of a single surgical center and consecutive surgical eras. The inception cohort size limited the statistical power of the study. Nevertheless, the study included a large number of variables, and there was no loss to follow-up. We cannot determine whether the finding of improved outcomes in the RVPA era is a cause-effect relationship attributable to the change in surgical shunt technique only, because many known or unidentified changes in practice over the years may account for the findings.
Conclusions
An analysis of 2 consecutive surgical eras showed that HLHS patients undergoing the Norwood procedure have experienced significant improvement in their survival to 2 years of age and in their psychomotor developmental outcome without any significant adverse change in general health or mental outcome. Survival and developmental outcome predictors varied between the 2 surgical eras and included modifiable and nonmodifiable variables. Further research in this field is needed, because adverse neurodevelopmental outcome in this patient population remains a concern.
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Acknowledgments |
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We would like to thank the families of these children for their active participation in the developmental sites across Western Canada and their commitment to this project. We sincerely thank the research coordinators and psychologists who made this research possible. We acknowledge the contributions of the Western Canadian Complex Pediatric Therapies Follow-Up Group: Dr D. Moddemann, Winnipeg, Manitoba, Canada; Dr P. Blakley, Saskatoon, Saskatchewan, Canada; and Dr A. Ninan, Regina, Saskatchewan, Canada.
Sources of Funding
Financial support was initially provided by the Glenrose Rehabilitation Hospital Research Trust Fund, with ongoing operational funding from The Registry and Follow-up of Complex Pediatric Therapies Project, Alberta Health and Wellness.
Disclosures
None.
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References |
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The online-only Data Supplement is available with this article at http://circ.ahajournals.org/cgi/content/full/CIRCULATIONAHA.107.741579/DC1.
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Circulation 2008 118: 1403-1404.
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