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Eur J Cardiothorac Surg 1998;14:165-172
© 1998 Elsevier Science NL

Cardiac surgery with extracorporeal circulation in 23 infants weighing 2500 g or less: short and intermediate term outcome¹

^a Department of Cardiothoracic Surgery, Hôpital Universitaire des Enfants Reine Fabiola, Brussels, Belgium
^b Department of Intensive Care, Hôpital Universitaire des Enfants Reine Fabiola, Brussels, Belgium
^c Department of Cardiology, Hôpital Universitaire des Enfants Reine Fabiola, Brussels, Belgium
^d Department of Anesthesiology, Hôpital Universitaire des Enfants Reine Fabiola, Brussels, Belgium

Received 29 September 1997; received in revised form 28 April 1998; accepted 12 May 1998.

Corresponding author. Department of Cardiac Surgery, Sint - Elisabeth ziekenhuis, Avenue de Fré 206, 1180 Brussels, Belgium. Tel.: +32 2 3731611; fax: +32 2 4772329.

	Abstract

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Objective and methods: From September 1990 to February 1997, 23 consecutive critically ill infants (12 males, 11 females) weighing 2500 g or less underwent cardiac surgery necessitating extracorporeal circulation (ECC). A retrospective study was carried out to evaluate short- and intermediate-term outcome. Mean weight at operation was 2265 g (range 1750–2500 g). Mean age at operation was 24 days. The indications for surgery were transposition of the great arteries (TGA; 7), ventricular septal defect (VSD; 4), aortic stenosis (AS; 3), univentricular heart (UVH; 2), tetralogy of Fallot (TOF; 2), interrupted aortic arch (IAA; 2), atrial septal defect (ASD; 1), atrioventicular septal defect (AVSD; 1) and total abnormal pulmonary venous return (TAPVR; 1). All patients were in NYHA class IV; 17 patients (74%) were intubated pre-operatively. Results: The mean aortic cross-clamping time was 40 min. Twelve patients required deep hypothermia (<20°C) with total circulatory arrest (mean duration 19 min). All patients were successfully weaned from extracorporeal circulation (ECC). Five patients left the operating room with an open sternum (mean duration before closure: 3.5 days). Mean duration of artificial ventilation was 10.6 days; of inotropic support 6.7 days and of intensive care stay 17.8 days. Severe complications were observed in 19 patients (83%): cardiac failure requiring high inotropic support, sepsis [7], and acute renal insufficiency [5]. One patient needed a ventricular assist device. Five patients (22%) died in the intensive care unit (ICU): 2 AS with fibroelastosis, 2 IAA with VSD, and 1 UVH with pulmonary atresia. At discharge from the ICU, 7 patients were receiving no treatment. Mean duration of follow-up was 32 months (range 2–80 months). We had 2 reoperations: 1 for right ventricular outflow tract obstruction 1 year after a switch operation and 1 for mitral valve replacement 1 year after total abnormal pulmonary venous return repair (death 30 days post mitral valve replacement). Survival at 1 year was 73%. At the last clinical examination 16 patients were in NYHA class I. Conclusion: Despite the severity of pre-operative cardiac disease, early surgical repair with ECC in infants weighing 2500 g or less is feasible with tolerable mortality yet with significant early morbidity.

Key Words: Cardiac surgery • Extracorporeal circulation • Neonates • Low birth-weight

	Introduction

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Although considerable progress has been made in achieving successful repair of congenital heart disease in the neonatal period, application of the strategy of early repair to the neonate with low birth-weight has been hampered by the perception that low birth-weight is in itself an operative risk factor.

Several reports have been published regarding the outcome of neonatal cardiac surgery as a whole. Results of surgery in neonates weighing 2500 g or less are scarce.

A retrospective study was carried out over a 6-year period to evaluate short- and intermediate-term outcome of cardiac surgery under extracorporeal circulation in this particular group of patients. Instead of birth-weights we took the actual weight at the time of surgery which seemed, to us, more relevant.

From the start we were aware of the obvious difficulties with this study because of the small number of children and the inhomogenicity of the pathologies involved. Furthermore, finding a `comparative' group of critically ill patients weighing more than 2500 g but with the same type of pathology seemed illusive. Therefore, the purpose of this study was not to compare the outcome of low birth-weight neonates with the general neonatal population, but to illustrate our experiences with this particular group of patients.

	Materials and methods

Top Abstract Introduction Materials and methods Results Discussion Conclusion References

 
Among 833 infants having undergone cardiac surgery under extracorporeal circulation between September 1990 and February 1997, 23 patients were identified as weighing 2500 g, or less, at the time of surgery.

Hospital charts were obtained for all patients and were sufficiently detailed to allow collection of the following parameters: sex; gestational age; age at operation; birth-weight; weight at operation; pre-operative clinical status; pre-operative therapy; pathology; type of surgery; duration of ECC; aortic cross-clamping and eventual total circulatory arrest, as well as immediate- and medium-term outcomes.

Statistical comparison with ² analysis was used in researching eventual risk factors for mortality within the group of low weight infants. Statistical significance was defined as P<0.05.

A total of 23 neonates weighing 2500 g or less underwent major cardiac surgery with the use of extracorporeal circulation; 12 males (52%) and 11 females (48%).

The more relevant pre-operative data are detailed in Table 1.

The gestational age range was 28–40 weeks with a birthweight range of 930–3200 g (mean 2275 g). The age at operation ranged from 1–90 days (mean 24 days) while the weight at that time ranged from 1750 to 2500 g (mean 2232 g).

Two patients had a proven chromosomal aberration (Trisomy 21 and Catch 22), while 2 others with univentricular hearts had right atrial isomerism. These last 2 patients also had associated asplenia. Three patients had to receive coarctectomy (with pulmonary artery banding in 1 case) prior to intracardiac repair.

All the patients were hospitalized pre-operatively in the neonatal intensive care unit; all presented with the signs of cardiopulmonary distress concordant with their main hemodynamic disorder: congestive heart failure with respiratory distress in unrestricted left to right shunts; low cardiac output pattern in left heart obstructive lesions and severe hypoxemia in both right heart obstructive lesions and transpositions.

Except in 1 patient with aortic arch interruption, severe metabolic acidosis could be avoided and no patient had to be ressuscitated prior to operation.

Most patients, however, had to be intensively cared for: 17 were permanently ventilated; 13 received catecholamines; 11 prostaglandins; 5 diuretics and 5 digoxin. Ten were receiving catecholamines and prostaglandins while on a ventilator.

None of the patients exhibited pulmonary complications in relation to prematurity but 4 had to be treated for septicemia prior to operation. Moreover, signs of impaired renal function were present in 2 patients.

Extracorporeal circulation (ECC) management, patient monitoring and anaesthetic protocol are similar to those used in neonates and children weighing more than 2500 g. Anaesthetic protocol involves analgetic anaestesia using high doses of opiates (Sufentanil, Pancuronium) systemic use of corticosteroids (Solumedrol).

Extracorporeal circulation with hypothermia (20–24°C) and hemodilution (haematocrit 20–25%) were used in all patients with standard neonatal circuit and oxygenator (1/4 circuit and Safe Micro/polystan 0.33 m² oxygenator with hollow fiber membrane); priming contained, as for all neonates, haemacel, SSPP, irradiated and deleucocytised red blood cells, aprotinin and mannitol. We manufacture our canulae ourselves from thorax drains and nasotracheal aspiration tubes; we mostly use canulae size 8 or 10 Ch for aortic canulation, canulae size 12–14 Ch for double venous canulation and canulae size 18–20 for single venous canulation.

Antegrade cold crystalloid cardioplegia (15 ml/kg) was administered in all patients, except for the patient with univentricular heart (UVH) and pulmonary atresia (PA). During extacorporeal circulation blood gas analyses were done using the alpha stat method. Modified ultrafiltration was systematically performed at the end of extracorporeal circulation. Relevant per-operative and post-operative information is summarized in Table 2.

In a patient with classic Tetralogy of Fallot we closed the VSD and placed a short transannular patch (autologous pericardium) to widen the right ventricular outflow tract. A patient with pulmonary atresia of the Tetralogy of Fallot type received, following closure of the ventricular septal defect, a 10 mm diameter pulmonary homograft in an orthotopic position.

In 4 patients an isolated ventricular septal defect was closed; 2 patients had a correction of an interrupted aortic arch and ventricular septal defect.

One patient had a closure of an ostium secundum type atrial septal defect and 1 had a correction of an isolated total abnormal pulmonary venous return.

Two patients had palliative procedures (9%). A patient with a univentricular heart and total abnormal pulmonary venous return with pulmonary hypertension had a correction of the total abnormal pulmonary venous return and a banding of the pulmonary artery. A patient with a univentricular heart and pulmonary atresia received a central aortopulmonary shunt.

	Results

Top Abstract Introduction Materials and methods Results Discussion Conclusion References

 
The mean duration of extracorporeal circulation was 117 min (range 49–285 min) (see Table 2). The mean aortic cross-clamping time was 40 min (range 20–92 min). The patient with a univentricular heart and accompanying pulmonary atresia was operated on without aortic cross-clamping. Twelve patients (52%) required total circulatory arrest with deep hypothermia (20°C) (mean duration 19 min; range 3–50 min).

All patients were successfully weaned from ECC. Five patients left the OR without sternal closure (22%) (mean duration before closure 3.5 days).

One patient had to be revised for bleeding with tamponade (4%). Five patients died in the intensive care unit (ICU)(22%). Two patients with critical aortic stenosis died of left ventricular failure (fibroelastosis) on the 2nd and 3rd day post-operatively; the patient with UVH and PA who received a central aortopulmonary shunt died of respiratory failure 1 month after surgery. The 2 other deceased patients had both an interrupted aortic arch with ventricular septal defect. One of them died of sepsis. The other benefited from extracorporeal membrane oxygenator because of low cardiac output on the first post-operative day but could never be weaned from the assist device. Autopsy showed that the patient had, in fact, a double outlet left ventricle and that the patch placed to close the ventricular septal defect obstructed the left ventricular outflow tract.

The mean duration of intensive care treatment for the surviving neonates was 17.8 days (range 5–35 days). The mean duration of inotropic support was 6.7 days (range 2–23 days) and of artificial ventilation 10.6 days (range 2–17 days).

Post-operative complications were observed in 19 patients (83%): cardiac failure requiring high inotropic support (13 patients); pneumonia (7); sepsis (7); pneumothorax (6); pulmonary hypertensive crisis (4); acute renal insufficiency requiring dialysis (5); hyperglycemia requiring insulin therapy (3); metabolic acidosis (3) and convulsions (2). Thrombopenia was present in 2 patients. Only 1 patient (with atrioventricular septal defect) presented a transient atrioventricular bloc.

A ² statistical analysis was performed to research risk factors for mortality within the group of patients (Table 3). Statistically significant were: preoperative metabolic acidosis (P<0.03); pre-operative dependency of catecholamines (P<0.01) and preoperative renal failure (defined as a serum creatinine concentration of more than 1.2 mg/dl associated with decreased urinary output) (P<0.03). Post-operatively significant risk factors were: resuscitation in the intensive care unit on the first postoperative day; renal insufficiency requiring dialysis (P<0.004) and high inotropic needs (dobutamin>10 µg/kg per min and/or adrenalin therapy) (P<0.01). The mean follow-up was 31 months (range 2–80 months). Survival rate at 1 year was 73%, the cumulative chance of patient survival (Kaplan–Meier) is 95% after 1 year and 88% after 2 years. ( Fig. 1 ).

View larger version (96K): [in this window] [in a new window]   Fig. 1. Cumulative chance of patient survival (Kaplan–Meier):

We had 2 reinterventions. One patient (transposition plus ventricular septal defect) had to be reoperated for right ventricular outflow tract obstruction due to malalignment of the VSD-patch.

The 1 surviving patient with a univentricular heart was operated on 1 year after the palliative procedure. She presented with retrograde pulmonary hypertension from a massively regurgitant single AV-valve which was replaced by a mechanical valve. At the same time, the first step (bidirectional Glenn) of the future total cavopulmonary correction was done; the PA-banding was left in place. Three weeks later she returned with thrombosis of the valve. Fibrinolysis failed. We replaced the mechanical valve by a biological valve and completed the total cavopulmonary correction but the child died a few days later.

Only 1 patient who had closure of a ventricular septal defect has residual mild chronic dyspnea and requires medical therapy. All other survivors are in excellent clinical condition with no respiratory, neurological or major cardiac deficits at the time of their last visit and are without any medication.

	Discussion

Top Abstract Introduction Materials and methods Results Discussion Conclusion References

 
The management of low-weight neonates with congenital heart defects is a well-recognised problem. The experience of the New England Regional Infant Cardiac Program showed that low birth-weight was a risk factor for mortality in infants with congenital heart disease and that death occurred mostly within the first few weeks of life [1].

Several reports have been published reporting that low birth-weight alone is a risk factor that contributes to death during or after cardiac surgery [2] [3] [4].

Due to the perceived high risk of open heart surgery using cardiopulmonary bypass early in life, critically ill neonates were mostly subjected to a first stage palliative procedure to avoid the use of extracorporeal circulation.

However, critical congenital heart disease may cause progressively more severe and sometimes irreversible secondary organ damage, notably to the heart, lungs and the central nervous system. It also interferes with normal post-natal development, such as myocardial hyperplasia, coronary and pulmonary angiogenesis and alveologenesis. In addition, there is a suggestion of developmental and psychomotor abnormalities in these children [5] [6]. Palliation does not seem to protect babies from these changes. Furthermore, in some infants palliation is ineffective. Corrective surgery becomes the only therapeutic option in these patients.

Rapidly growing clinical experience with reparative cardiac operations in neonates seems to contradict the earlier impression that cardiac surgery under extracorporeal circulation in low-weight infants carries a high risk: early reparative surgery using cardiopulmonary bypass has been recently performed in this group of patients with acceptable mortality (18%) and fair long-term survival [7] [8]. These series involve, however, low birth-weight neonates, and do not specify the actual weight of the neonate at the time of surgery, which is, in our opinion, more relevant.

The early mortality in our series (22%) is, taking into account the severity of the clinical condition of our patients, acceptable. Although the results in neonates weighing less than 2.5 kg are worse when compared to those achieved in patients weighing more (early mortality 7–11%) [4] [7] [8], results are encouraging. Prolonged efforts to achieve medical stability and promote weight gain may not yield superior results compared with early surgical intervention [8].

Statistically significant risk factors associated with mortality in our series: are presence of pre-operative metabolic acidosis; type of pathology (univentricular congenital heart disease, aortic stenosis with fibroelastosis and interrupted aortic arch associated with ventricular septal defect); pre- and post-operative renal insufficiency and high post-operative inotropic needs. Age, low birth-weight and low weight at the time of intervention did not significantly affect the outcome within the group of low weight infants. These results seem to correlate with those of other authors for low (birth) weight infants [7] [8].

More accurate pre-operative evaluation can influence the mortality rate. In retrospect, the 2 infants who died after surgery for critical aortic stenosis had already very poor prognoses due to the presence of fibroelastosis. One of the patients with IAA and VSD had, in fact, a double outlet left ventricle. The patient died because of malposition of the patch to close the VSD; due to the small size of the heart it was not possible to correct this anatomic diagnosis intra-operatively.

Obvious limitations of our study are the small number of patients and the great variety of congenital heart defects involved. We were unable to compare the results with a matched control group regarding the variety of factors involved. We can state that within the group of low weight infants, low weight itself does not influence mortality rates. Particularly encouraging is the notion that all survivors are in good clinical condition after corrective surgery with no respiratory, neurological or major cardiac deficits. All but 1 of our patients is without medication.

	Conclusion

Top Abstract Introduction Materials and methods Results Discussion Conclusion References

 
Primary reparative surgery for congenital heart disease offers the opportunity to rectify the underlying defect and to abate the secondary effects developing in other organs, and can be performed with good short- and intermediate-term results even in low weight neonates. Palliative procedures should be reserved for those neonates whose anatomy and physiology are not amenable to biventricular repair. We feel encouraged to persist in a policy of major surgery in neonates with low weight and correctable, or palliable, simple, or complex, congenital heart defects.

	Footnotes

 
Presented at the 11th Annual Meeting of the European Association for Cardio-thoracic Surgery, Copenhagen, Denmark, September 28 – October 1, 1997.

	References

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1. Fyler D. Report of the New England Regional Infant Care Program. Pediatrics 1980;65(Suppl.):337-461.
2. Quaegebeur J.M., Rohmer J., Ottenkamp J. The arterial switch operation: an eight year experience. J Thorac Cardiovasc Surg 1986;92:361-381.[Abstract]
3. Trusler G.A., Castaneda A.R., Rosenthal A., Black Stone E.H., Kirklin J.W. Current results of management in transposition of the great arteries with special emphasis on patients with associated ventricular septal defect. J Am Coll Cardiol 1987;10:1061-1071.[Abstract]
4. Castaneda A.R., Mayer J.E., Jonas R.A., Lock J.E., Wessel D.L., Hickey P.R. The neonate with critical congenital heart disease: repair – a surgical challenge. J Thorac Cardiovasc Surg 1989;98:869-875.[Abstract]
5. Rabinovitch M., Herrera-de Leon V., Castaneda A.R., Reid L. Growth and development of the pulmonary vascular bed in patients with tetralogy of Fallot with or without pulmonary atresia. Circulation 1981;64:1234-1249.[Free Full Text]
6. Newberger J.W., Silbert A.R., Buckley L.P., Fyler D.C. Cognitive function and age at repair of transposition of the great arteries in children. N Engl J Med 1984;310:1495-1499.[Abstract]
7. Pawade A., Waterson K., Laussen P., Karl T.R., Mee R.B. Cardiopulmonary bypass in neonates weighing less than 2.5 kg: analysis of the risk factors for early and late mortality. J Card Surg 1993;8:1-8.[Medline]
8. Chang A.C., Hanley F.L., Lock J.E., Castaneda A.R., Wessel D.L. Management and outcome of low birth weight neonates with congenital heart disease. J Pediatr 1994;124:461-466.[Medline]

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