About 8–9 neonates out of every 1000 live births suffer from congenital heart defects (CHD), causing high morbidity and mortality (33%) in this population (23, 24). The reported prevalence of CHD in the United States of America is 40 thousand each year (25). The prevalence of CHD among Iranian children is reported to be 12.30 per 1000 live births(26). About 15–60% of these patients are affected by malnutrition, indicating it as a frequent problem (13, 27–30). Malnutrition is a common phenomenon in infants and children with CHD in low and middle-income countries, probably partly due to late presentation, delayed intervention and frequent hospitalization caused by respiratory infections (2, 31, 32). The prevalence of malnutrition by Mehrizi and Drash was reported to be 27% in 1962 (33); however, 85% was reported in a study in Turkish infants with CHD in 2010 (34). Aghaei-Moghadam et al. reported that the prevalence of malnutrition among Iranian patients with acyanotic cardiac lesions were 68.7% and 66.4%, based on WFA and WFL (4). Cyanosis, pulmonary hypertension and congestive heart failure influence the severity and type of the malnutrition. Furthermore, the severity of growth impairment is dependent on the type of the cardiac defect (33). The growth is impaired severely in moderate to large VSD and TGA, and moderately in TOF patients (13, 33, 35).
In the current study, the prevalence of moderate to large VSD, TGA and TOF was 53.1%, 4.1% and 8.2%, respectively; hence most of our patients suffered from the aforementioned defects; which highlights the importance of the performed intervention in our study. The congestive heart failure and recurrent respiratory infection occur as a result of delayed corrective surgery in developing countries. This vicious cycle results in the high preoperative malnutrition (36).
Different mechanisms have been considered to be involved in the etiology of malnutrition in infants and children with CHD, including inadequate energy intake, increased energy expenditure, and malabsorption, due to low cardiac output and impaired gastrointestinal function (37), as well as fluid restriction, disturbed hemodynamic situation (38, 39), fatigue during feeding and recurrent respiratory infections (38–40). Diminished blood flow of the splanchnic circulation, despite adequate caloric intake, may contribute to the impaired growth by malabsorption; however, there is a considerable controversy about the impact of malabsorption on malnutrition (13, 41). The total energy expenditure of critically ill children is estimated to be increased up to 30% in mild to moderate stress, up to 50% in severe stress and 100% in major burns (42). Decreased energy intake is known as the most import factor involved in the malnutrition of patients with CHD (13), as it is 76% of that in normal population (43). Putting altogether, increased energy requirement and decreased energy intake necessitate further intervention for improvement of the feeding in children with CHD.
Our current study shows that WFA z-score improved significantly when energy- and protein-dense formula was given to malnourished CHD infants instead of standard infant formula. Other growth indices (LFA and BMI z-score) also improved, but non-significantly, probably because it takes more time to catch up in length than to catch up in body weight.
According to a study evaluating the daily energy intake in 100 infants with CHD, the median intake was less than 100 kcal/Kg/ day, which is the minimum requirement for normal infants (44). Our patients were given 36.23 ± 52.49 kcal/kg/day at first which was increased up to 98.61 ± 38.27 kcal/kg/day at the end of the study.
Growth and development, wound healing and immune system function are influenced by nutritional status. Malnutrition affects both short term and long-term postoperative outcomes. Recurrent infection due to impaired immune system function and delayed surgical wound healing are considered as the short term outcomes, while disturbed growth, physical and cognitive development are seen as the long term ones (41, 45, 46). The Society of Thoracic Surgeons Congenital Heart Surgery Database has confirmed the correlation between lower WFA z-scores and poorer surgical results (47). High postoperative mortality (48) and morbidity, such as increased frequent hospitalization, persistent delayed growth, prolonged recovery time, and increased hospital stay (15) are associated with the preoperative malnutrition. Many studies have indicated that adequate nutritional status preoperatively highly influences the ability of the patient to recover following the surgery (19–22, 30, 46, 49).
Early and effective nutritional intervention is crucial for children with CHD, in order to ameliorate growth and reduce the aforementioned complications. Nutritional support should preferably start as soon as possible after diagnosis and continue during the post-operative period (50). Several studies support the use of a high energy formula for increasing energy intake and promoting weight gain in infants with CHD (50, 51). In the early study by Jackson and Poskitt, an 31.7% increment in energy intake by the use of a high energy formula lead to increased weight gain from 1.3 g/kg/day to 5.8 g/kg/day (5). Recently, nutritional guidelines were developed for infants with CHD awaiting surgery, using a modified Delphi process (10). For infants with moderate nutrition risk, an energy intake of 100–110 kcal/kg/day was recommended, with protein contributing 9–12% of energy. For those with high nutrition risk, the recommended energy intake was 120–150 kcal/kg/day, with 10-15en% of protein (up to 4 g/kg/day). These high-risk infants should preferably receive 50–100% of their nutrition requirements as energy and nutrient dense formula (1).
Preoperative use of high energy formula has been associated with weight gain and decreased hospital stay and postoperative complications (50). Postoperative use of energy- and nutrient-dense formula has been found to improve weight gain in infants with CHD (1) and to decrease hospital stay and reduce antibiotic use in these patients (52). In line with these findings, we observed a clinically and statistically significant weight gain (indicated by an increase in WFA z-score) when energy- and nutrient-dense formula was given preoperatively to malnourished infants with CHD. Furthermore, head circumference and mid-upper arm circumference were increased at the end of the study, compared to the first assessments. A better preoperative nutritional status, as observed in our study, may reduce post-operative mortality and complications and improve recovery.
One of the strengths of this study was its prospective nature; moreover, it was conducted in a tertiary center. Most patients with the diagnosis of CHD needing surgical repair, are referred to this center; It could be concluded that the patients enrolled in this study are an acceptable representation of the whole patients with moderate to high risk CHD.
There are some limitations to this study as well. The relatively short intervention period is a limiting factor for interpreting the results. We expect that the effect of giving energy and nutrient-dense formula on weight and length gain would have been more pronounced with a longer intervention period. Furthermore, we did not evaluate the postoperative outcome of the infants in this study.
In conclusion, the results of this study highlight the efficacy of preoperative feeding with energy- and nutrient dense formula in improving weight gain of malnourished infants with CHD.