In our study, the mean total cost of healthcare was about $240 per patient per annum, with direct medical costs accounting for 81% of the total cost. Hospitalization costs was found to be a major contributor to the direct medical cost as almost half of the children in the study had been hospitalized at least once in the year under review. Direct health care cost expended for hospitalization has been found to be responsible for more than half of all medical costs for children with birth defects such as congenital heart diseases [31, 32]. On an average, drugs and investigations were responsible for 45% of total direct cost each among children who were compliant with medications and had investigations when prescribed. The long term needs for medication, periodic investigative assessment and recurrent hospitalization associated with CHD further highlights the financial burden borne by the families of the affected children.
Catastrophic health expenditure (CHE) occurs when households spend a large proportion of their income (above a threshold usually 10% income) to pay for healthcare . In this study, the incidence of CHE among families interviewed was 35.5%. This finding is similar to what was reported by Sadoh et al  in Benin, where about 34.4% of families spent greater than 10% of income on care of children with chronic heart failure. This implies that more than a third of families with children with CHD spend more than 10% of the families’ annual income on the healthcare of only one child in the family. This demonstrates the potential effect that the presence of this condition has on the welfare of families. Azzani et al  in their study showed that socioeconomic status, incidence of hospitalization, and presence of a family member with a chronic illness were significant factors associated with household CHE. In the presence of CHE, families may have to cut down on basic needs like education, feeding, clothing and compromise living standards to cope with the long term cost of healthcare [35, 36]. With 3 as the median number of children in the family in this study, it means other children may suffer neglect, lack and low living standards because of a sibling with CHD.
The Catastrophic Overshoot and Mean Positive Overshoot show that a third of the families spent far above the 10% income threshold on the care of these children. Furthermore, almost 1 in every 10 families spent greater than 50% of their annual income on CHD treatment. Affected families exceeded this threshold by as low as 0.26% and as high as 237.7%. This certainly means that a proportion of these families will spend far above their annual income to care for the affected child and may even be forced to borrow money. When there is a significant proportion of out of pocket house hold expenses spent on health, it is usually at the expense of non- health goods and services such as care of other non-ill siblings at home [32, 33]. In these cases, health services could be paid for with family savings, loans or sale of assets; all which put a financial strain on the family income . This validates the impoverishing effect of healthcare cost as families now utilize future earnings in replacing household assets and paying back debts and interest.
Some Nigerian authors have reported that co-morbidities like congestive cardiac failure (CCF) in association with CHD increases cost thereby leading to financial catastrophe in the families with children with CHD [37, 38]. This study similarly identified CCF as a significant driver of healthcare cost in these children, significantly increasing both the direct and indirect cost. CCF is a common co-morbidity in children with CHD which results from the pulmonary over-circulation that occurs following the left to right shunting of blood through these defects. When longstanding and uncontrolled, CCF leads to recurrent chest infections, pulmonary hypertension and failure to thrive in affected children . This finding was not surprising as the presence of CCF leads to frequent trips to the hospital either on an outpatient basis or for emergency in-patient care, thus increasing all categories of healthcare cost. The cost of treatment of a child with chronic heart failure has been described as enormous by Sadoh et al  where greater than 25% of the families seen in their study spent over 10% of their income on anti-failure medications.
Duration of cardiology clinic attendance was also found to significantly increase the direct non-medical cost. The results illustrate that as the duration of clinic attendance increases, the direct non-medical cost becomes significantly higher. Regular and frequent clinic attendance was found to increase the financial burden on the families due to expenses made on transportation, feeding and outpatient consultation fees by Sadoh et al  in their study on children with chronic heart failure. In their study, the authors reported that as high as 8% of the family income was spent on transportation, and postulated that this was due to frequent trips to the hospital for drug refills. Transportation costs however did not impact on direct medical cost in the present study. This could be due to the fact that some families spend more at the initial stage of diagnosis of this condition on investigation, medication and sometimes on hospitalization in order to plan appropriate treatment. Also over time, the older patients may also forgo clinic visitations especially when they have no associated co-morbidities thus cutting down on medical cost.
The cost of healthcare was not significantly associated with social class unlike the study by Sadoh et al  who noted higher expenditures among the lower social economic class compared to those in the middle or high social class. This difference could be attributed to the fact that their study was carried out in a hospital setting and involved a smaller sample size as compared to the present study. It was also surprising to note that expenditures made by insured families were not significantly different from those by families paying for healthcare with out-of-pocket payment mechanism. Health insurance in Nigeria is a social health insurance model operated by the National health insurance scheme which covers a healthcare of a family; which consists of the principal, his/her spouse and a maximum of four children below the ages of 18 years [40, 41]. A person below the age of 18 years is regarded as a minor and is not allowed to register on his or her own; however newborn infants up to the ages of 3 months are covered by the health insurance schemes of their mothers . Thereafter, the enrollment of children into the NHIS is solely dependent on their parents or guardians [40, 41]. Low enrollment rates into health insurance schemes were described by Onwujekwu et al  who noted that only 1% of the households in a survey in South Western Nigeria had a primary adult registered under the NHIS. Delayed enrollment of children into a health insurance scheme could be a reason why most of the children in an insured family are not enjoying discounted cost of healthcare.
This study attempts to fill the gap created by drought of research into economic burden of healthcare cost among families of children with CHD, however, it is not without limitations. First, the study attempted to estimate healthcare in the group under investigation over a period of one year prior to the study, this could be affected by recall bias. Since the conservative care in children with CHD is a continuous care, participants were patiently interrogated from the most recent events to more distant events. Secondly, there is a likelihood of underestimation of healthcare cost in this study since only children who sought one form of care before the medical mission were interviewed, the cost of care for families who forgo care was not calculated thus leading to an underestimation. Lastly the study did not explore the coping strategies employed by these families in mitigating the enormous economic burden forced on families with children with CHD.