Discussion

Poverty is global challenge. According to World Bank estimates, 1345 million people in the world subsisted on a daily income of US$1.25/day in 2008, which is inadequate to sustain adequate caloric intake;7 854 million people in the world suffer from chronic malnutrition of which 146 million are children.8 This represents more than a quarter of children in the developing world.8 The number of persons below the arbitrary poverty line (unable to purchase a basket of food providing 2400 kcal in rural and 2100 kcal in urban area) in India were 260 million (26%) in 2006.9 Poverty and economic backwardness are closely linked to child malnutrition so much so that economists have argued that the level of child malnutrition in a society can be an effective yard stick for measuring poverty.10 The relation between poverty, malnutrition and childhood diseases is well established.11

CHD is a major contributor for poor growth in children. Possible mechanisms include inadequate caloric intake, malabsorption and increased energy requirement caused by increased metabolism. Congestive heart failure, hypoxia and cyanosis may all contribute12–19 to poor growth in such children. Non-availability of food in the economically underprivileged results in deprivation of both energy and proteins critically needed for growth. Undernutrition during pregnancy and the first year of life has structural, metabolic and anthropometric effects on the child that persists throughout life.8 This is a major consideration in the developing world where 35% of children have malnutrition measured by stunting.20 Indeed, 70% of malnourished children live in Asia.20 The fate of these children when they have the additional burden of CHD has not been discussed in literature.

It has been shown that the nutritional status of children with CHD significantly improves following correction of CHD. Vaidyanathan et al21 reported a significant improvement in nutritional status at 3 months follow-up after cardiac surgery. The same group reported that 73% of children undergoing CHD repair below the age of 5 years had normalisation of growth at 2 years follow-up.22 Earlier studies have reported that the catch up growth after CHD surgery is most rapid within 6–12 months.23 Given the implications of poverty and malnutrition for long-term well-being, it is not clear whether CHD surgery will yield similar results in the economically underprivileged with a very high prevalence of malnutrition. The present study attempted to answer this question by following the anthropometric parameters of growth in a selected population of economically disadvantaged children.

The World Bank uses an income of US$1.25/day as the minimum amount required to sustain an individual's caloric requirement.7 In Southeast Asia, 40.4% of population belong to the US$1.25/day poverty group.7 In the Indian context with a single wage earner and family size of four, this amount would be US$5/day for the family (Rs 84 600, equivalent to US$1800 per annum for family). The present study was conducted in a group of children selected from families having an annual income of Rs 20 000 or less (US$425 per annum). One would expect that their income level would be grossly inadequate to sustain the caloric requirements. Thus, the children were selected from an extremely disadvantaged background. It must be mentioned that they still belong to the state with the highest human development index in India, having 100% literacy and the lowest figures for infant mortality rate.24 This unique combination made access to these children possible and their follow-up thorough.

One need to choose simple and reliable means of monitoring growth in such a cohort. Weight and height are always measured prior to surgery and can be checked periodically by a healthcare worker. Both these values can be related to the age of the child. Weight for height has readily available Z score reference values (WHO) only below the age of 5 years; hence this parameter was not used in this study in which 60% of the population was above this age limit. BMI charts were used instead for uniformity in analysis. For comparison of growth parameters, CDC 2000 standards were used as these have been previously validated for use in Indian children.22 25 The Z score is widely recognised as the best system for analysis and presentation of anthropometric data in surveys.

In the present study, 92% of the population had weight for age Z score below zero with 61% having weight for age Z score ≤−2. The absence of more severe forms of malnutrition in a still larger number could be explained by the unique status of population (high human development index and literacy rate, hence focus of care on the affected child) and the higher prevalence of simpler cardiac lesions (figure 1). Also, there was wide dispersion of human development within this group with some families showing extreme deprivation as in aborigines living in forests.

The present study showed that there was significant nutritional improvement following cardiac surgery in the cohort as a whole with the mean weight for age improving from 14.74±5.75 to 23.83±7.83 kg (p<0.05). The percentage of subjects whose anthropometric parameters were at or above the predicted level can be presumed to be a reflection of the effect of surgery on subsequent growth. Before surgery, only 8% of the subjects had weight for age Z score above zero; following surgery, 35% of the subjects crossed this level. The percentage of malnourished children also significantly decreased after cardiac surgery. While the decline in malnutrition in the operated children was gratifying, there still remained a proportion of children who were malnourished postoperatively. In the present study, the group with residual malnutrition showed higher prevalence of cyanotic CHD and extreme economic deprivation. A small number also had syndromes affecting growth. Suboptimal recovery of somatic growth after CHD surgery in severely malnourished infants has been reported earlier.26 27 Uncorrected poverty has been a major contributor to malnutrition in the present series. The incidence of low birth weight in such a group would be significantly high and this would impact their recovery after surgery. However, the information on birth weight was not available in the majority of the patients in this study.

Interestingly, the odds for improvement were least impressive for height for age and BMI for age Z scores. Height is influenced by a number of factors that are not correctable by surgery, for example, mid-parental height. Also, catch up growth may not be possible after some age.

That the improvement in weight was not simply related to growth is established by the improvement in weight for age Z score. The median improvement in Z score was 0.85. Thus, 50% of the children improved their Z score by at least 0.85. This is also reflected by the decrease in the number of malnourished children from 61% to 27% after surgery. Recently, Vaidyanathan et al22 reported that severe malnutrition at presentation was a predictor of poor postoperative weight gain. In the present series, however, those with worst malnutrition exhibited the best improvement. Mean weight for age Z score of malnourished children improved from −3.01 to −1.6 (p<0.005) with surgery; the change in the group without initial malnutrition was not statistically significant. When the severely malnourished children (weight for age Z score <−3) were analysed separately their Z scores for weight and BMI also improved significantly with surgery.

Vaidyanathan et al22 observed residual malnutrition (weight for age Z score ≤−2) in 27.3% of children following cardiac surgery in an economically unselected series. The present study showed that 44.2% of the malnourished population still remained at weight for age Z score ≤−2, showing the impact of poverty. Residual malnutrition subjects in the present study tended to have extreme economic deprivation, cyanotic CHD and coexisting syndromes. Incidence of congestive heart failure at presentation in the series was too low to be a potential contributor.