Introduction
Necrotizing enterocolitis (NEC) is a rare but devastating disorder associated with mostly premature infants. Preterm or normal babies with congenital heart disease are at risk of various comorbidities because of the abnormal heart structure or the treatment procedures employed. Necrotizing enterocolitis is one of the severe complications that impact children with cardiac lesions. The rate of NEC is estimated to be very high in newborn infants with symptomatic congenital heart disease compared to normal infants. The majority of full-term babies with NEC may be in the backdrop of developing cardiac conditions due to hemodynamic alterations in the gastrointestinal system.
What Is Necrotizing Enterocolitis?
Necrotizing enterocolitis is a condition characterized by intestine inflammation that leads to bacterial invasion and causes cellular damage and necrosis of the small and large intestines. It usually occurs in the second to third week of life. Approximately 70 percent of these occur in premature infants and are responsible for around eight percent of all admissions in the neonatal intensive care unit (NICU). In full-term infants, it is typically seen in the initial few days and is mostly associated with congenital heart defects. The signs and symptoms of NEC include vomiting, diarrhea, lethargy, poor feeding, and abdominal tenderness. If the condition progresses, it can result in intestinal perforation (hole in the intestine), peritonitis (inflammation of the abdominal lining), sepsis (severe response to infection), and death. Standard resuscitation is followed to support the vital signs, and the first intervention in the management of NEC is to stop enteral feedings (tube feeding), initiate parenteral nutrition (by vein), and maintain the patient's NPO (nothing by mouth). Enteral feedings are resumed once the infection resolves, which may take several days to weeks.
What Is Congenital Heart Disease?
Congenital heart disease (CHD) is an umbrella term used for a range of birth abnormalities that affect the functioning of the heart. There is no exact cause for this condition. Still, it can occur due to various risk factors such as genetic disorders, chromosomal abnormalities, infections, uncontrolled diabetes, certain medications, or smoking or alcohol consumption by the mother during pregnancy. CHD is characterized by rapid breathing, irregular or rapid heartbeat, severe tiredness, swelling of the legs, cyanosis (bluish discoloration of the skin), and poor feeding. Though recent advances in medical care and surgical techniques restore the functioning of the heart, patients often require treatment throughout their lives.
How Is Necrotizing Enterocolitis Associated With Congenital Heart Disease?
Necrotizing enterocolitis is a serious gastrointestinal disorder that is responsible for high morbidity and mortality in the neonatal period. It is associated with predisposing factors such as intrauterine growth retardation (poor growth of the fetus), congenital heart disease, birth asphyxia (lack of blood or oxygen to the baby), maternal exposure to cocaine, etc. The complexity or severity of cardiac lesions can majorly impact the etiology (cause) of necrotizing enterocolitis.
Any cardiac conditions that cause hemodynamic alterations (instability in the blood flow) can cause poor blood flow, less oxygen in the systemic circulation, and ischemia, resulting in gut necrosis. The prevalence of necrotizing enterocolitis is about 10 to 100 times higher in newborn infants with symptomatic congenital heart disease compared to infants with structurally normal hearts. They have a considerable morbidity due to severe intestinal injury, short bowel syndrome (lack of function of the small intestine), and a delay in neurodevelopment. The exact cause of NEC in congenital heart disease patients is not completely understood. However, it is considered multifactorial due to reduced bowel perfusion pressure due to poor diastolic pressure and less oxygenated blood flow. This results in damage to the integrity of the gastrointestinal lining, bowel ischemia (reduced blood flow), and increased bacterial growth.
Recent studies have shown that the severity of NEC in infants with congenital heart disease is less, and there is a reduced risk of bowel perforation, short bowel syndrome, and sepsis compared to infants with classical NEC. However, intestinal necrosis was more frequent in infants with CHD and NEC compared to infants without CHD.
What Are the Risk Factors for Necrotizing Enterocolitis in Congenital Heart Disease?
Various cardiac anomalies are associated with an increased risk of developing necrotizing enterocolitis. Some of these conditions include:
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Single ventricle physiology (one functioning ventricle).
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Hypoplastic left heart syndrome (left side of the heart is poorly developed).
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Very low birth weight infants.
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Infants with atrial or ventricular septal defects (holes in the heart's walls).
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Tricuspid atresia (tricuspid valve is missing or abnormally developed).
How Is Necrotizing Enterocolitis Managed in Patients With Congenital Heart Disease?
The management of necrotizing enterocolitis in infants with congenital heart disease is complex and challenging as the underlying cause consists of distinct features. The current management includes empirical antibiotic therapy, bowel rest with gastric decompression, parenteral nutrition, and supportive care.
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Ampicillin (if hemodynamically stable) and Gentamicin with or without Metronidazole are recommended for suspected cases of NEC; Vancomycin and Piperacillin-Tazobactam if the patient is hemodynamically unstable or in advanced cases of NEC.
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The healthcare team decides the initial surgery whether to perform NEC surgery or cardiac surgery initially, depending on the severity of the condition. Surgical intervention is indicated depending on the clinical signs and investigations that suggest intestinal perforation or if medical therapy is proven to be ineffective. It comprises stenting of the ductus arteriosus in ductal-dependent systemic lesions, usually followed by a bidirectional Cavo pulmonary connection for repair. Balloon atrial septostomy (widening the defect to improve the blood flow) can be considered in the transposition of arteries. However, further research is required to determine the association of NEC after cardiac surgical procedures.
Conclusion
Necrotizing enterocolitis is a severe gastrointestinal emergency that mostly occurs during the neonatal period. The severity or complexity of the cardiac conditions can highly influence the development of NEC. Studies have shown that neonates with low birth weight, preterm or gestational age less than 36 weeks, single ventricle, receiving parenteral nutrition, or mechanical ventilation are more likely to develop necrotizing enterocolitis. Around three percent of full-term infants with congenital heart diseases can also develop NEC. Research states that surgical intervention was successful in 33 percent of patients with CHD and NEC, which is highly significant compared to medical therapy alone. However, with appropriate intervention, early detection and rigorous monitoring of the infants are crucial to improve the outcomes of necrotizing enterocolitis.
