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J Thorac Cardiovasc Surg 2006;131:412-417
© 2006 The American Association for Thoracic Surgery
Surgery for Congenital Heart Disease |
a Division of Pediatric Cardiovascular Surgery, Department of Surgery, University of Michigan Medical School, Ann Arbor, Mich
b Division of Pediatric Cardiology, Department of Pediatrics and Communicable Disease, University of Michigan Medical School, Ann Arbor, Mich
Read at the Thirty-first Annual Meeting of The Western Thoracic Surgical Association, Victoria, BC, Canada, June 22-25, 2005.
Received for publication June 26, 2005; revisions received August 25, 2005; accepted for publication September 8, 2005. * Address for reprints: Richard G. Ohye, MD, F7830 Mott Hospital, 1500 East Medical Center Dr, Ann Arbor, MI 48109-0223 (Email: ohye{at}umich.edu).
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Abstract |
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 Top Abstract IntroductionPatients and MethodsResultsDiscussionAppendix 1References |
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METHODS: A single-institution review of all patients undergoing a Norwood procedure for a single-ventricle malformation from May 1, 2001, through April 30, 2003, was performed. Patient demographics, anatomy, clinical condition, associated anomalies, operative details, and outcomes were recorded.
RESULTS: Of the 111 patients, there were 23 (21%) hospital deaths. Univariate analysis revealed noncardiac abnormalities (genetic or significant extracardiac diagnosis, P = .0018), gestational age (P = .03), diagnosis of unbalanced atrioventricular septal defect (P = .017), and weight of less than 2.5 kg (P = .0072) to be related to hospital death. On multivariate analysis, only weight of less than 2.5 kg and noncardiac abnormalities were found to be independent risk factors. Patients with either of these characteristics had a hospital survival of 52% (12/23), whereas those at standard risk had a survival of 86% (76/88).
CONCLUSIONS: Although improvements in management might have lessened the effect of some of the traditionally reported risk factors related to variations in the cardiovascular anatomy, noncardiac abnormalities and low birth weight remain as a future challenge for the physician caring for the patient with single-ventricle physiology.
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Introduction |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionAppendix 1References |
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The outlook has improved dramatically since Norwood and colleagues
2
reported the first successful staged palliative reconstructive operations for infants with HLHS in 1983 and Bailey and associates
3
introduced cardiac transplantation for the disease in 1986. However, despite improvements in survival, HLHS continues to be the most common anomaly resulting in death within the first year of life in the United States.
4
Most of the mortality associated with staged repair occurs during the first stage, the Norwood procedure. Therefore the elucidation of preoperative risk factors associated with higher mortality could lead to better identification of those infants more likely to benefit from transplantation rather than staged repair.
Many authors have previously reported risk factors for the Norwood procedure. Despite these numerous reports, there exists no consensus on which risk factors are significant. Forbess and coworkers
5
found lower preoperative pH to be a significant risk factor for stage I mortality, whereas in a previous report
6
our group found no increased risk. Initial operations after 14 or 30 days have both been reported as a risk factor,
6-8
whereas others have found no increased risk for those infants operated on after 14 days of life.
9
The data are similarly ambiguous for fetal diagnosis,
10-13
anatomic subtype of HLHS,
5,6,8,10,14,15
lower operative weight,
5,6,8,10,16-18
smaller ascending aortic diameter,
5,6,16,17,19-21
longer circulatory arrest
6,11,17,20
or cardiopulmonary bypass (CPB) time,
11,17,21
noncardiac congenital anomalies,
7,16,22,23
and the presence of moderate-to-severe tricuspid regurgitation before the operation.
5,17,19,24
In addition to these risk factors, 3 authors have reported a higher risk of mortality associated with obstructed pulmonary venous return.
7,8,22,25
Many of these previously reported risk factors were derived from small cohorts of patients or collected over relatively long periods of time, during which management patterns have evolved. These factors might account for the level of disparity among risk factors described in the literature. This report describes our recent experience with the Norwood procedure for palliation of HLHS and other functional single ventricle (FSV) malformations, with a focus on identifying relevant risk factors in the current era.
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Patients and Methods |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionAppendix 1References |
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The study hypothesis was that because of improvements in operative technique and perioperative management, many of the traditional risk factors previously reported for the Norwood procedure have been overcome.
Patient Population
Between May 1, 2001, and April 30, 2003, 111 infants underwent a Norwood procedure for HLHS or other FSV malformations. The demographic data that were collected included gestational age at birth, age at initial operation, weight at operation, sex, race, cardiac anatomy, noncardiac diagnoses, and fetal diagnosis. Surrogates for condition at presentation included history of cardiac arrest or seizures, the lowest pH, and the peak creatinine levels. Preoperative pH and creatinine levels estimated adequacy of resuscitation and immediate preoperative condition. Also noted were the need for balloon atrial septostomy and the presence of pulmonary venous obstruction, as defined by significant hypoxemia in conjunction with radiographic evidence of pulmonary edema and an intact or nearly intact atrial septum confirmed by means of Doppler echocardiography and direct surgical or pathologic inspection. Echocardiographic parameters, including cardiac valve sizes and functions, aortic size and the presence of antegrade flow, and ventricular function, were all collected. Operative parameters included time in the operating room, deep hypothermic circulatory arrest (DHCA) or regional cerebral perfusion (RCP) time, CPB time, and shunt type and size. Postoperative parameters included time to chest closure and extubation, days in the intensive care unit, and days in the hospital. Time of follow-up and continuation to hemi-Fontan or Fontan procedures were also recorded. A detailed list of the potentially significant factors that were recorded is included in Appendix 1. Hospital survival was the primary outcome.
Surgical Technique
The technique used for the first stage of reconstruction was a classic Norwood procedure, as initially described by Pigott and associates.
26
Important modifications, including the manner of the proximal aortic anastomosis, technique and extent of the arch reconstruction, and the use of smaller shunts, have been previously detailed in a publication from our group.
22
One hundred five of the patients received a systemic–to–pulmonary artery shunt, of which 66% (69/105) were 3.5 mm, 31% (33/105) were 4.0 mm, and 3% (3/105) were 3.0 mm. Six patients (median weight, 2.2 kg; range, 1.7-3.2 kg) received a right ventricle–to–pulmonary artery shunt ranging in size from 4.0 to 5.0 mm.
Statistical Analysis
Normally distributed data are expressed as means ± standard deviation. Nonnormal data are expressed as medians and ranges. Dichotomous variables were analyzed with the Fisher exact test, and continuous variables were subjected to the Student t test. Wilcoxon rank sum testing was used for nonnormally distributed data.
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Results |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionAppendix 1References |
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Of the 100 patients with HLHS, there were 36 (36%) with aortic atresia and mitral atresia, 23 (23%) with aortic stenosis and mitral stenosis, 20 (20%) with aortic atresia and mitral stenosis, 1 (1%) with aortic stenosis and mitral atresia, 10 (10%) with a common atrioventricular valve orifice, and 10 (10%) with double-outlet right ventricle. The median ascending aorta size was 3.3 mm (range, 1.40-8.60 mm). Antegrade aortic flow was seen in 49 (42%) patients.
Twelve (11%) patients were identified as dysmorphic, and 34 (31%) patients underwent genetic analysis. Eleven (10%) patients were found to have abnormal chromosomes or a named genetic syndrome (Table 1). Ten (9%) patients had significant acquired or congenital extracardiac diagnoses (Table 2).
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Median time in the operating room was 205 minutes (range, 149-525 minutes). Seventy-five (68%) patients underwent DHCA, whereas RCP was used in the remaining 36 (32%) patients. Median DHCA time was 37 minutes (range, 24-68 minutes). Median RCP time was 39 minutes (range, 30-69 minutes). Median CPB time was 96 minutes (range, 59-308 minutes).
Chest closure was performed after a median of 7 days (range, 1-15 days), and patients were extubated after a median of 7 days (range, 2-46 days). The median number of days in the intensive care unit for survivors was 9 (range, 3-87 days), and the average length of hospital stay for survivors was 21 days (range, 8-148 days). Median length of follow-up was 17 months (range, 0.5-33 months), with 71 (64%) patients undergoing stage II palliation. Of these 71 patients, 30 (27%) have gone on to a Fontan procedure.
Hospital Survival and Risk Factors
The overall hospital survival was 79% (88/111 patients). The most common cause of death was low cardiac output in the immediate postoperative period in 39% (9/23) of patients, followed by unexpected arrest in patients seemingly making an unremarkable recovery in 22% (5/23). Other cardiorespiratory causes of death included high pulmonary vascular resistance in a patient with a history of obstructed pulmonary venous return (n = 1), refractory arrhythmia (n = 1), severe native aortic insufficiency (n = 1), severe neoaortic insufficiency (n = 1), and severe tricuspid regurgitation (n = 1). Noncardiac causes included sepsis (n = 1), necrotizing enterocolitis (n = 1), retroperitoneal hemorrhage caused by bladder perforation (n = 1), and intracranial hemorrhage caused by cerebral aneurysm (n = 1).
Table 3 shows the variables that could not be shown to have an effect on hospital survival. Univariable analysis revealed that noncardiac abnormalities, including genetic abnormalities or significant extracardiac malformations (P = .0018), gestational age at operation (P = .03), diagnosis of unbalanced atrioventricular septal defect (P = .017), and weight of less than 2.5 kg (P = .0072) were significantly related to hospital death (Table 4).
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Discussion |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionAppendix 1References |
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at the Children's Hospital of Philadelphia reported an improvement in hospital survival from 56.2% from 1984 through 1989 to 71.3% from 1995 through 1998 and 77.4% during 1998. At The Hospital for Sick Children in Toronto, hospital survival improved from 41% from 1990 through 1993 to 61% from 1994 through 1997 and 81% from 1998 through 2000.
16
Hospital survival from 1992 through 1996 at the Children's Hospital of Wisconsin was 53%, whereas it reached 93% from 1996 through 2001.
21
We have likewise experienced significant improvements at the University of Michigan since first performing the Norwood procedure for HLHS in 1983. Meliones and coworkers
27
reported a 46% thirty-day survival for patients operated on between 1983 and 1989. From 1990 through 1997, hospital survival had improved to 76%, as reported by Lloyd and Bove.
7,22
In this analysis we found that many of the previously reported risk factors related to cardiovascular anatomy appear to have been minimized in the current era. The most commonly reported factors, including obstructed pulmonary venous return, ascending aortic diameter, anatomic subtype of HLHS, age at initial operation, preoperative pH, CPB time or operative time, and fetal diagnosis, could not be shown to have a significant effect on survival. Perhaps most surprising is the fact that obstructed pulmonary venous return did not reach significance. The most obvious explanation would be the limited sample size. However, recent advances in postoperative management, such as inhaled nitric oxide and sildenafil, might also have an effect. Perhaps most importantly, the objective of this study was to evaluate risk factors for hospital survival in the current era. The failure to define obstructed pulmonary venous return as a risk factor for hospital survival should not be misinterpreted to mean that it does not have a significant effect on the ultimate outcome of the patient with FSV. Underscoring this point, of the 7 hospital survivors, there was 1 late death of undetermined cause, 1 patient whose Fontan procedure was delayed because of marginal pulmonary vascular resistance, and 1 patient who is not a Fontan candidate and will ultimately require a cardiac transplantation because of pulmonary vascular obstructive disease.
Weight of less than 2.5 kg and noncardiac diagnoses continue to be significant risk factors for hospital survival for patients with HLHS or other FSV conditions. Although noncardiac anomalies might be more difficult to affect, recent advances might improve the survivals for the low-birth-weight FSV patient. The management of pulmonary blood flow is problematic in these smallest of patients. The traditional 3.5-mm modified Blalock-Taussig shunt results in pulmonary overcirculation and systemic malperfusion. The 3.0-mm graft leaves little room for technical error at the anastomoses and is potentially at increased risk of thrombosis. The recent renewed interest in the right ventricle–to–pulmonary artery conduit for the Norwood procedure might be a solution for these low-birth-weight patients. Although challenges remain, ongoing advances in preoperative, intraoperative, and postoperative management continue to improve the outlook for the patient with FSV.
Although this is a relatively large cohort of patients, it is possible that other risk factors might have been identified with a larger sample size. However, it is important to note that several of the previously identified risk factors have been identified from small groups of patients, suggesting that at a minimum, the effect of many of these risk factors has been lessened.
An analysis of the effect of DHCA versus RCP could not be performed. Data are listed and analyzed as total DHCA or RCP time. The study subjects are also participating in an ongoing randomized, prospective, evaluator-blinded trial. Because there were personnel common to both this article and to the blinded portion of the study, we were unable to perform this analysis without compromising the randomized trial.
This cohort is a heterogeneous population of patients undergoing a common operation. However, the numbers of patients are too small to perform meaningful subgroup analysis, which leaves the possibility that certain risk factors might apply to individual diagnostic groups.
The primary outcome for this study was hospital survival, and the follow-up is of an intermediate length. Patient characteristics, which might act as risk factors for late survival, cannot be defined.
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Appendix 1 |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionAppendix 1References |
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Demographics
Age
Weight
Gestational age at birth
Gestational age at operation
Sex
Race
Primary cardiac diagnosis
Other cardiac diagnoses
Other noncardiac diagnoses
Anatomic subtype of hypoplastic left heart syndrome (aortic stenosis-atresia, mitral stenosis-atresia)
Morphologic right versus left ventricle
Dysmorphic by physical examination
Chromosomal abnormality
Genetic syndrome
Preoperative factors
Fetal diagnosis
History of cardiopulmonary arrest
Lowest preoperative pH
Immediate preoperative pH
Peak preoperative creatinine
Immediate preoperative creatinine
History of seizures
Obstructed pulmonary venous return
Cause of obstructed pulmonary venous return
Need for balloon atrial septostomy
Echocardiographic data
Aortic valve diameter and Z value
Ascending aortic (at sinotubular junction) diameter and Z value
Midtransverse arch diameter and Z value
Mitral valve diameter and Z value
Tricuspid valve diameter and Z value
Ventricular function
Antegrade aortic flow
Degree of tricuspid regurgitation
Degree of mitral regurgitation
Degree of aortic regurgitation
Degree of pulmonary regurgitation
Degree of tricuspid regurgitation
Operative data
Total operative time
Cardiopulmonary bypass time
Deep hypothermic circulatory arrest or region cerebral perfusion time
Shunt type
Shunt size
Hospital course
Time to chest closure
Time to initial extubation
Days to initial intensive care unit discharge
Days to hospital discharge
Hospital survival
Follow-up
Length of follow-up
Progression to hemi-Fontan procedure
Progression to Fontan procedure
Dead-alive
Cause of death
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References |
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TopAbstractIntroductionPatients and MethodsResultsDiscussionAppendix 1References |
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