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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 17  |  Issue : 2  |  Page : 128-135

Morphological and clinical indices determining mode of repair in children with tetralogy of Fallot in Enugu, Nigeria


1 Department of Paediatrics, College of Medicine, University of Nigeria Teaching Hospital/ University of Nigeria, Okolobiri, Nigeria
2 Department of Paediatrics and Child Health, Niger Delta University Teaching Hospital, Okolobiri, Nigeria
3 Department of Community Medicine, Enugu State University Teaching Hospital, Enugu, Nigeria

Date of Submission09-Sep-2020
Date of Decision22-Oct-2020
Date of Acceptance02-Dec-2020
Date of Web Publication13-Nov-2021

Correspondence Address:
Dr. Josephat M Chinawa
Department of Paediatrics, University of Nigeria Teaching Hospital, ItukuOzalla, Enugu, Enugu State
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njc.njc_28_20

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  Abstract 


Background: Children with tetralogy of Fallot (TOF) present with various clinical and morphological attributes which aid in screening for primary, stage, or elective repair.
Objectives: This study is aimed at determining the morphological and clinical indices that predict mode of repair among children with TOF in our locale.
Materials and Methods: This was a retrospective echocardiographic review of children with TOF carried out in three different institutions over a 5-year period.
Results: The mean age of presentation was 5.0 ± 5.3 years. The nutritional status revealed that 18.2% (8/44) were wasted, 25.0% had severe wasting, while 2.3% were obese. Stunting was observed in 4.5% of the patients and severe stunting in 29.5%. The mean pulmonary valve (PV) annulus of 43 of the patients assessed was 11.0 ± 5.5 mm (mean z-score: −2.03 ± 1.95). Five of them (11.6%) had values one standard deviation (1SD) below the mean of the standard population, 32.6% had values 2SD below the mean, and 27.9% had values 3SD below the mean. Of the 33 children whose right pulmonary artery (RPA) z-scores were assessed, 24.2%, 12.1%, and 12.1%, respectively, had RPA z-scores of 1SD, 2SD, and 3SD below the mean of the standard population, while 17.5% and 7.5% of 40 children whose left pulmonary arteries were assessed had z-scores of 1SD and 2SD below the standard mean, respectively. Right aortic arch and major aortopulmonary collateral arteries (MAPCAs) were seen in 8.1% and 30.5% of the children, respectively. 30.5% of the children with TOF had MAPCAs. Features of Down syndrome were observed in 4.8% (3/62) of the patients.
Conclusion: A large proportion of patients present with various degrees of malnutrition with a significant low z-score for PV annulus and branch pulmonary artery diameters. The presence of right aortic arch and MAPCAs was observed in the patients. The increased rate of protein–energy malnutrition, small PV annulus, MAPCAs and presence of right aortic arch, etc., are screening tools that may assist the surgeon in selecting the various surgical options and timing in the approach of children with TOF in this locale.

Keywords: Children, clinical, morphological, tetralogy of Fallot, variation


How to cite this article:
Chinawa JM, Duru CO, Chukwu B, Chinawa AT. Morphological and clinical indices determining mode of repair in children with tetralogy of Fallot in Enugu, Nigeria. Nig J Cardiol 2020;17:128-35

How to cite this URL:
Chinawa JM, Duru CO, Chukwu B, Chinawa AT. Morphological and clinical indices determining mode of repair in children with tetralogy of Fallot in Enugu, Nigeria. Nig J Cardiol [serial online] 2020 [cited 2021 Nov 29];17:128-35. Available from: https://www.nigjcardiol.org/text.asp?2020/17/2/128/330426




  Introduction Top


The diagnosis of tetralogy of Fallot (TOF) comprises a constellation of cardiac defects that arise from anterior-cephalad deviation of the conal septum, coupled with defects in the septoparietal trabeculations.[1] This anterior superior deviated conal septum gives rise to a malaligned ventricular septal defect (VSD), overriding of the aorta, and variable degrees of infundibular, valvar, and supravalvar pulmonary stenosis.[2] TOF is the most common cyanotic congenital heart disease, comprising about 3.5% of infants born with congenital heart disease and 8%–10% of cyanotic congenital heart disease.[2],[3]

It is important to note that children with TOF present with variable clinical and morphological variations. For instance, the aortic override seen on TOF determines the size of the patch required to baffle blood to the aorta.[4] Furthermore, anomalous coronary artery crossing the right ventricular outflow tract (RVOT) may warrant the surgeon to get a conduit for Rastelli operation instead of doing a transannular patch (TAP).[4] Another mode of surgery for coronaries crossing the RVOT is transatrial-transpulmonary approach that is a suitable option in situation when the branch pulmonary artery (PA) size is within the normal range for body surface area. A small infundibulotomy parallel to the abnormal coronary and a modified double-barrel technique are also surgical options in the approach of coronaries crossing the RVOT.[4]

The morphology of the malaligned or subarterial VSD may affect the site of placement of sutures during VSD closure; hence, the risk of postoperative conduction defects.[4] Knowledge about these variables provides a unique and valuable resource for improving our understanding of these morphological variations and to assess their impact on surgical care.

In addition, functional tricuspid regurgitation (TR) is an ominous sign in children with TOF. If noted during screening, it will then be expedient for the pediatric cardiologist to discuss with the surgeon, as isolated TR is noted as an independent predictor of mortality.[4] Indeed, the severity of TR in children with TOF correlates with a higher cardiovascular mortality rate.[5],[6],[7],[8] Age, weight, and protein–energy malnutrition have also been seen as vital clinical correlates to consider when screening children for TOF repair. In fact, malnutrition alone is an important clinical correlate that determines surgical outcome and length of intensive care unit (ICU) stay for children with TOF repair.

In our setting, there exists a gap between the knowledge of these screening tools and the surgical intervention of children with TOF. This study is, therefore, aimed at documenting various morphology and clinical correlates seen in children with TOF that may assist the surgeon in selecting the various surgical options and timing in the approach of children with TOF in this locale.


  Materials and Methods Top


This was a descriptive study carried out in three different institutions, University of Nigeria Teaching Hospital, Blessed Children Hospital, and Triple Care Hospital all in Enugu, over a 5-year period (March 2016–March 2020). This University of Nigeria Teaching Hospital is a referral center for children with congenital heart disease, while Blessed Children Hospital and Triple Care Hospital all in Enugu are hospitals that were run by pediatric cardiologists, and children with congenital heart disease have been evaluated in these centers.

Seven hundred and fifty-eight echocardiography reports on children with cardiac disease were studied, and a diagnosis of TOF was made in 62 children. Echocardiographic diagnosis was made using a Hewlett-Packard Model SONO 2000 and the E2-Model SonoScape Medical Corp. 2019 cardiac Ultrasound Imaging. Echocardiography was done by consultant pediatric cardiologists in the institution of study. The study had a quality control where other cardiologists confirm the findings periodically so as to reduce bias.

Assessment of nutritional status

Anthropometric measurements included height in centimeters for age more than 2 years and supine length in centimeters for age below 2 years. Weight was also measured in kilograms. z-scores for weight for age, weight for height, and height for age were also calculated Using the WHO Anthro 3.2 Geneva 2011 software. Nutritional status was ascertained by means of z-scores.

Definition of operability

The concept of “operability” simply means mode of surgery such as primary intracardiac, staged, emergency, or elective repair.

Only children with an echocardiographic diagnosis of TOF were included in the study, while children with other types of congenital heart disease were excluded.

Data analysis

Categorical variables were analyzed in the form of proportions and percentages and presented in the form of tables, while discrete variables were analyzed in the form of means and standard deviations (SDs). The z-scores of weight for age, weight for height, height for age, and body mass index were calculated with the WHO “Antrho” and “Anthro plus”( v 1.0.4, WHO, 2007) software for children 5 years and below and children above 5 years. The z-scores of pulmonary valve (PV) annulus, right pulmonary artery (RPA), and left pulmonary artery (LPA) diameters were calculated with echo z-score calculators based on body surface area.


  Results Top


Sixty-two patients were diagnosed with TOF over the period under review giving a prevalence of TOF among children with congenital heart disease as 8.2% (62/758). [Table 1] illustrates some of their demographic characteristics. They comprised 59.7% of males and 40.3% of females. Their age ranged from 1 month to 18 years, with a mean age of 5.0 ± 5.3 years. The preschool age was the most populated (45.2%). The nutritional status of 44 (had data for analyzing nutritional status) of the 62 patients was analyzed and revealed that 18.2% (8/44) were wasted, 25.0% had severe wasting, while 2.3% were obese. Stunting was observed in 4.5% of the patients and severe stunting in 29.5%. It was also observed that 25.0% of the children were wasted and stunted.
Table 1: Demographic characteristics of patients with tetralogy of Fallot

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The mean PV annulus of 43 of the patients assessed was 11.0 ± 5.5 mm (mean z-score: −2.03 ± 1.95). Five of them (11.6%) had values 1SD below the mean of the standard population, 32.6% had values 2SD below the mean, and 27.9% had values 3SD below the mean. The mean of the RPA and LPA diameters was 8.1 mm (mean z-score: −0.51 ± 1.80) and 8.2 mm (mean z-score: 0.48 ± 1.86), respectively. On the right, 24.2% (8/33), 12.1%, and 12.1% of them were 1SD, 2SD, and 3SD below the mean of the standard population (based on weight and height). On the left, 17.5% (7/40) had mild stenosis and 7.5% moderate stenosis. The anatomical locations of the pulmonary stenosis are shown in [Table 2]. Majority (27.4%) have valvar pulmonary stenosis, while a substantial number (25.8%) had a combination of the different types of stenosis.
Table 2: Anatomical location of pulmonary stenosis among the patients

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The size of associated VSD ranged from 4 mm to 24 mm, with a mean of 12.8 ± 4.4 mm. Aortic override as a component of TOF was observed in all the patients. The override was <30% in 3.3% of the children and between 30% and 50% in 85.5% of the children. There was a right aortic arch in 8.1% of the patients. Coronary crossing RVOT was seen in 4.8% (3/62) of the patients and patent foramen ovale in 3.2%, but none had TR. Thirty-six of the patients were assessed for major aortopulmonary collateral arteries (MAPCAs), and it was found that 30.5% of them had the collaterals. Features of Down syndrome were observed in 4.8% (3/62) of the patients.


  Discussion Top


Pulmonary valve annulus

From the pulmonary z-score values, it is noted that over half of the children with TOF may need staged repair such as Blalock–Taussig shunt or right ventricular to PA shunt operation. PV annulus measured by z-score is a very important determinant for survival in children with TOF. Children with small annulus and a low z-score will benefit from a TAP. Studies by Awori et al.[8] noted several “cutoffs” in literature, which can lead to errors in insertion of TAP. They noted, in their systematic review of children with TOF repair, that a very little percentage of 26.3% of the studies mentioned the actual z-score cutoff point for pulmonary annulus size in deciding TAP operation.[8],[9]

Awori et al.[8] noted a z-score of − 2 as a marker below which to insert a TAP. On the contrary, Stewart et al. observed PV z-score >−4 as the best predictor for PV sparing, and this value can avert recurrent obstruction.[10] However, PV annulus z-score, calculated from echocardiography measurements, has played a very important role in decision-making process, and a score below − 2 has been commonly referenced as a “cutoff” point for the insertion of a TAP.[8] The sole aim of ascertaining PV annulus size using z-scores is to protect the right ventricle (RV) from chronic volume overload.[11] However, there are several controversies surrounding this approach, such as the ideal age and weight for complete repair, staged versus primary repair, the role of percutaneous interventions in staging, and the importance of sparing the RV infundibulum.[11],[12],[13],[14]

It is interesting to note that, however, a “cutoff” point for PV z-score value to determine surgical technique has not been well established. This is even made more complex with varying available literature.[12],[13],[14],[15]

Kasturi et al.[16] strongly noted in their study, using receiver operator characteristic curves, that the most potent prognostic indicators for selecting children for surgical closure of TOF, especially TAP, are pulmonary annulus, PA annulus, and main PA z-scores. The pulmonary z-score obtained in our study will, therefore, serve as a guide to help the surgeon in deciding for surgical technique in our locale. It is advisable for every country or region to have their own z-scores for PV annulus.

Pulmonary artery

When we looked at the average percentage of children with TOF whose branch PAs fall short of 2SD for mean, 31.5% may at least need a stent or a stage procedure. This is the first time we are generating these scores in South-East Nigeria among children with TOF, and it can be of immense benefit to surgeons in this locale. The use of LPA and RPA as predictors of survival among children with TOF cannot be overemphasized. For instance, I-Seok et al.[17] noted increases in pulmonary regurgitation in children with borderline LPA and RPA after TOF repair.[17] They noted that the contribution of the LPA to the total regurgitant flow volume was 54% ± 19%, whereas its average contribution to the total forward flow volume They, however, could not hazard any reason for this difference in blood flow in the branch pulmonary arteries.flow is strongly correlated with branch PAs z-scores but noted no significant correlation between z-scores of branch pulmonary arteries and net forward flow volume.[17]

Children with TOF who present with borderline z-scores of PA, if not properly managed, can lead to atelectasis and severe pulmonary regurgitation after surgical repair. Some authors have hazarded the insertion of LPA stents, so as to help reduce pulmonary regurgitation.[16],[17],[18]

It is very important to establish the continuity of branch PAs before surgery. It is also very important to estimate the severity and level of pulmonary hypoplasia. The gold standard for estimating the continuity of branch PAs before surgery is the use of cardiac computerized axial tomography (CT) scan and magnetic resonance imaging (MRI). However, in a resource-poor setting, echocardiographic estimation of the pulmonary arteries using the Nakata index could be helpful.[19] Normal measurements are around 330 ± 30 mm/m2. Children with index >100 mm2/m2 usually fulfill operability and would normally undergo total intracardiac repair with minimal complications.

Ventricular septal defect

We noted, in this study, very large (12.8 ± 4.4 mm) perimembranous, malaligned, and tortious and large size VSD as very poor prognostic predictors for surgical outcome. It is very inferential to depict the fact that the morphology of the VSD is a very decisive marker in deciding for surgical closure of TOF.[20] It has also been noted in a study that large perimembranous VSD seen in TOF, if not properly handled, can lead to postoperative heart block. It is reported that the atrioventricular conduction axis usually courses through the zone of the fibrous continuity that intertwines between the tricuspid, aortic, and mitral valves in large perimembranous malaligned VSDs.[20] This, therefore, poses a risk of injury during placement of VSD patch, with attendant perturbation of atrioventricular conduction.[21],[22]

We noted few subpulmonic VSDs in our study. The closure of subpulmonic VSDs in children with TOF has been associated with increased morbidity and mortality when compared with infracristal VSD. It is true that anterior cephalad deviation of the conal septum in TOF normally caused by large VSDs and infundibular stenosis is the bona prima in definition of TOF, yet the infracristal variety is usually categorized as a tetralogy syndrome.[23] In fact, prolapse of the right or noncoronary cusp in subarterial VSD in TOF is a harbinger of aortic regurgitation.[23],[24],[25]

Again, children who present with subarterial VSD in TOF repair usually show a higher RV/LV ratio, especially if the surgery is done without TAP.[23],[24],[25],[26]

Nevertheless, it is important, therefore, to note that both TOF with subarterial VSD and those with infracristal VSD had a better prognosis and is a good selection criterion than the perimembranous VSD variety because they have an excellent long-term outcome.[24],[25],[26],[27]

Coronary arterial abnormalities

Another important indicator for screening for operability in children with TOF, seen in this study is when coronaries crosses the RVOT. This was noted in about 3.2% of our children. Kervancioglu et al.[28] noted a prevalence rate of coronary artery anomalies in 12.7% of the patients in their series. This higher value could be due to a verge sample size of 620 children enrolled in their study.[28]

Claire et al.[29] in a meta-analysis also noted anomalous coronary artery crossing RVOT to range from 2% to 23% of the patients with TOF. The most common type of coronary noted in this study is the left anterior descending coronary.[28] Some studies have also implicated the anterior interventricular artery. These findings are similar to the reported clinical series.[29],[30]

The surgical sequel of this coronary crossing the RVOT is the risk of transection during complete repair, as they are often mistaken for a large infundibular or conal branch.[31]

Several surgical techniques have been proposed in children with coronary crossing RVOT. These include placement of a right ventricular-to-pulmonary arterial conduit (Rastelli), right ventriculotomy with a patch on the coronary artery, the use of TAP, or pulmonary valvar commissurotomy.[29],[30]

The PV annulus z-score and the level of crossing RVOT are the two most important echocardiographic screening for reducing mortality and morbidity after surgical repair in children with TOF.[29],[30],[31],[32],[33]

Pulmonary stenosis

Majority of the children present with valvar pulmonary stenosis in this study. This is at variance with several studies who identified infundibular stenosis as the most common variety.[34],[35],[36] Infundibular stenosis is another bad prognostic factor for screening for surgery. It connotes a worse prognosis more than valvar and supravalvar pulmonary stenosis. This level of stenosis usually results from the anterior-cephalad deviation of the conal and an anomalous relationship to the septoparietal trabeculations. The use of catecholamine in children with infundibular stenosis should be abhorred as the degree of stenosis could be worsened. This can lead to severe hypoxia and hypercyanotic spells.[35],[36],[37],[38]

We noted the prevalence of pan stenosis (valvar, infundibular, and supravalvar stenosis) in this study as 25.8%. In this scenario, the surgeon should be prepared to inspect the valve and subsequently do a leaflet thinning and commissurotomies to help increase free leaflet edge mobility.[38] Other options are thorough subvalvar resection and infundibular incisions. If infundibular obstruction persists, the z-score of the RVOT may be re-examined, and if need be, valve-sparing repair should be done.[38]

Aortic override

Over ridding of the aorta is seen in all our cases. Majority of the children with TOF in this study had between 30% and 50% of override. This is caused by the malaligned perimembranous VSDs. The severity of aortic override is normally assessed by echocardiography or by measuring the percentage of aortic valvar leaflets that override the RV.[20]

Tricuspid regurgitation

We noted no moderate or severe TR in our children. TR in children with TOF is a very ominous screening sign, and these patients should be evaluated thoroughly before surgery. Jouke et al.,[39] in a retrospective, multicenter cohort study among 129 patients with TOF in an 8-year follow-up, noted preoperative TR as a predictive factor for adverse events. They opine close surveillance among such children. Woudstra et al.[40] also noted, in their study, that moderate TR was seen in 12% of their participants during 7.6 years, and this progressed to severe TR.

Nutritional status

We noted from this study that 18.2% of the children with TOF were wasted, 25.0% had severe wasting, while 2.3% were obese. Stunting was observed in 4.5% of the patients and severe stunting in 29.5%. We also observed that 25.0% of the children were wasted and stunted.

There is a strong link between malnutrition and increased morbidity and mortality for TOF repair. Woudstra et al.,[40] in their series, noted age and undernutrition as significant predictors of morbidity during repair of TOF. The cause of death among malnourished children with TOF ranges from worsening hypoxemia, prolonged cardiopulmonary bypass, and prolonged stay in the ICU. It is important, therefore, during screening children for repair to emphasize the need of nutritional rehabilitation.

Major aortopulmonary collateral arteries

This was noted in 30.5% of the children who had TOF presenting with MAPCAs.

MAPCAs are found in about 35%–40% of the patients with TOF but mainly in pulmonary atresia.[41] Echocardiography underestimates the number of MAPCAs, and accuracy of detecting MAPCAs is very high with cardiac CT and MRI. Unfortunately, we could not do CT scan and MRI due to financial restraint. However, the presence of MAPCAs does not denote inoperability.

It has been postulated that an inverse relation occurs between the total number of ortopulmonary collaterals and the size of the main pulmonary arteries.[41]

MAPCAs is a lesion with so many anatomic variabilities.[41] More often than not, the pulmonary arteries (PAs) are not in continuity with the RVOT. The branch PAs may even be small and augmented through the ductus arteriosus. Clinically, the lung may be overloaded giving rise to signs and symptoms of heart failure.[41] On the other hand, the MAPCAs may be stenotic at the aortic origin, or the pulmonary end may be patent ductus arteriosus dependent. This can also produce cyanosis and thus protect the pulmonary vasculature.[41]

The major objective of surgery in this group of patients is to construct PA with a good z-score, to do a PA unifocalization, and construct an RV-PA conduit after VSD closure.[41]

Right aortic arch

We reported the prevalence of right-sided arch in children with TOF as 8.1%. Other studies have documented varying prevalence, probably due to sample size, and some were done among the adult population.[42],[43],[44] For instance, a study documented a prevalence of 25% while another study with prevalence ranging from 13% to 35%.[42]

We noted no vascular associations in children presenting with right arch in our study. However, it is important to note that if there are associated vascular malformations such as aberrant left subclavian artery with left ligamentum arteriosus or pulmonary rings causing symptoms such as dysphagia or stridor, a single-stage corrective surgery under circulatory arrest and profound hypothermia is worthwhile.[43]

It is important to note that though stenosis of the proximal aortic arch is rarely observed in patients with TOF, but if present can cause additional systemic overload and worsening cyanosis. Stenting of the arch could resolve the obstruction.[44],[45]

Age at presentation

Late presentation is a very important clinical correlate that connotes a bad prognostic criterion for repair. This is seen in our study where we obtained the mean age of presentation as 5.0 ± 5.3 years. Martins Izabela et al.,[46] in a systematic review, noted the best age for repair of TOF to be between 3 and 6 months of age. They suggested total repair as the best approach with minimal complications and death rate if performed early. Glen et al.,[47] in a large cohort, noted that deaths occurred in children with primary repair above 12 months of age. They concluded also that the best survival and physiological outcomes of children with TOF were achieved when primary repair was done between 3 and 11 months.

Down syndrome

We noted a prevalence of 8.2%, and when we looked at their PV annulus and branch PAs, we noted that children with Down had lower values than their non-Down counterpart. Boussouf et al.[48] noted the prevalence of Down syndrome in children with TOF as 3.6% when compared with a world prevalence of between 5% and 8%.[48] Fudge et al.,[49] in analysis of outcomes following Surgery in Down syndrome children who had congenital heart disease, noted that children with Down syndrome had longer ICU stay and more tendency of having respiratory challenge, infections, and pulmonary hypertension compared to their non-Down colleague.[49] We also noted that children with Down syndrome had decreased growth velocity compared with their counterparts without Down. This also makes operability very difficult. It is, however, hypothesized that decision for early surgical repair in patients with Down syndrome may be related to feeding, growth, and adenotonsillar hypertrophy that is common with them.[50]


  Conclusion Top


Operability (mode of surgery such as primary, stage, or elective) strongly depends on z-scores of PV annulus and branch PAs in children with TOF. Other important morphological correlates for surgical repair are MAPCAs and right aortic arch. Age, Down syndrome, and nutritional status are very vital clinical markers in deciding the mode and timing of surgery. It is advisable for every region to generate their own cutoff for PV and branch PA z-scores, since there are lots of variations as seen in the literature.

Limitation

The use of CT or MRI in delineating the anatomy of branch PAs is very crucial. Unfortunately, we could not do these due to financial restraints.

Ethics approval and consent to participate

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standard. Informed written consent was also granted by the parents/caregivers of children before they were operated upon.

Financial support and sponsorship

This paper is not funded by any organization. We bore the expenses incurred in this study.

Conflicts of interest

There are no conflicts of interest.



 
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