For neonates in this study, there was a relationship between poor preoperative condition and worse outcome after heart surgery. Poor presenting patient condition was defined as cardiovascular compromise requiring mechanical ventilation and resuscitation or evidence of metabolic acidosis with end organ dysfunction. Neonates with CHD who presented preoperatively with these clinical features were at a disadvantage in terms of duration of ventilation associated with heart surgery and mortality in the case of cardiovascular compromise. Adverse preoperative condition or critical illness was most common when CHD was recognised late, after the neonate had been discharged home, and was least common when recognition was antenatal. The route to recognition of CHD was not directly related to the outcome measures, most likely because a range of interrelated and unevenly distributed factors contributed.
Certain cardiovascular risk factors may render a neonate particularly vulnerable to preoperative deterioration15,16
—for example, obstructed pulmonary venous return in the context of SV.16
Thus, there are neonates with CHD in critical condition for whom the most optimal preparation and access to tertiary care will not avert severe cardiovascular compromise. These children are likely to present very early in life with critical illness. Our study suggests, however, that, as well as predetermined cardiovascular risk factors, the route by which CHD is first recognised also plays a major part in determining preoperative condition, as this determines access to and timing of appropriate treatment.
A major limitation of this study is the small number of patients included; an investigation of a larger cohort would be informative. Furthermore, the results must have been influenced by local factors and practice patterns. For example, the rates of antenatal diagnosis for our dataset were as follows: for all patients, 20%; in SV, 68%; in LHO, 19%; in PA 27%; in TGA, 6%; and in TAPVC, 0%. A recently presented program‐based rate of antenatal diagnosis for a neonatal cohort was noticeably higher at 54% (A Dorfman and G Wernovsky, personal communication). Previously reported rates for SV range from 36.6%17
and for TGA a rate of 26% has been reported.2
We are a tertiary centre with no obstetric service on site and the median age on admission to the unit was 8.5 days. Other series report a median admission age for neonates with CHD of between 0 and 4 days,2,17,18
suggesting a late presenting age in our patients. This is in keeping with what we believe may be a high proportion of missed patients with CHD, which was 25%. Furthermore, 77 (27%) neonates in the cohort received ICU care at another institution before transfer to our centre for cardiac surgery. This aspect may have influenced the proportion of patients who required intubation and subsequent escalation of intensive care support mainly for the purpose of transfer.
Our first outcome measure, ventilation time, is a summary measure of morbidity that is less vulnerable to extraneous factors than length of hospital stay. We note with interest a recent study that associated prolonged stay after neonatal arterial switch operation with adverse neurological outcome in childhood.9
The median duration of ventilation for our cohort was 101 h, or 4.2 days. Data directly comparable with ours are not readily available in the literature, although a program‐based cohort recently reported a median length of hospital stay of 13 days (A Dorfman and G Wernovsky, personal communication). In general, the total duration of ventilation is likely to be greater for patients who require preoperative intubation, and a high proportion of neonates requiring this will influence the median value. We note that cardiovascular compromise for which mechanical ventilation was required was present in 109 (38%) of our patients and this proportion rose to 60% in the missed neonates of group C. A published series of patients with TGA reported preoperative mechanical ventilation in 38% in patients with postnatal diagnosis,2
although we are unaware of other surveys of neonates with missed CHD.
The mortality among our patients was 9.4% at 30 days and 12% to hospital discharge. This is broadly comparable with a recently published UK summary of overall neonatal mortality for 2000–1 that reported that 9.1% of 780 patients died before 30 days and 13.9% died by 1 year of age.19
Neonatal operative mortality is influenced by case mix, prematurity, associated syndromes or anomalies, and low Apgar scores.20,21
Although we found a strong relationship between adverse preoperative patient condition and mortality (and other authors have presented related information1,2
), risk adjustment based on critical illness scores is not usual.21
Our data are supported by reports that use severity of illness scores such as paediatric index of mortality, as these are known to be useful in populations of critically ill children that include those with CHD.22
Several examples in the literature describe the evolution of dangerous or fatal CHD symptoms when access to appropriate specialist care is impaired. A 1998 study from Toronto indicated that 4% of neonates with simple TGA died preoperatively from hypoxaemia due to a restrictive atrial septum.15
A 1994 study from the UK found that, of 185 patients who died of CHD in one region, 30% had died without a diagnosis.6
A further 1999 study from France of 250 patients with TGA detected eight previously unrecognised cases at autopsy.2
A 1999 regional study from the USA identified, among 800 infants who died of CHD, 76 who died before a diagnosis was made.7
A UK study that evaluated patterns of postnatal CHD presentation concluded that, of those discharged without a diagnosis, 35% became unwell or died before the age of 6 weeks.5
Our study evaluated the effect of variations in access to appropriate care in a population that was actually treated with cardiac surgery. In addition to the 286 included patients, we know of five further neonates with CHD who were referred to our centre during the study period and died without access to surgery. All died from severe cardiovascular compromise and end organ injury that were related to late diagnosis. All these studies are salient reminders that neonatal CHD remains a significant source of morbidity and mortality.
In conclusion, for the individual patient, optimised preoperative condition will be associated with minimised operative morbidity and mortality. Early identification of CHD will facilitate access to appropriate care and is in the patient's best interests. The ideal scenario for CHD screening and triage is beyond the scope of this paper, but dialogue and feedback between cardiac units and the communities responsible for obstetric and neonatal screening may be required to promote best practice.