Our study focused on the surgical outcome of primary total correction of TOF patients from Tanzania. The principal findings of this study were that 30-day mortality following primary total correction of classical TOF at our institution was 5.9% and all fatalities occurred within the hospital. Our mortality rate is lower than the reported average of 6.9–15% in developing countries [10]. For instance, in Ethiopia, a study involving 62 TOF patients operated between 2009 and 2014 reported a mortality rate of 12.9% [20]. Tchoumi et al. studied 22 TOF patients who underwent complete repair surgery by a visiting team. The average age of the patients was 9.2 ± 6.5 years, and the mortality rate was 9% [21]. Similarly, in a study by Benbrik et al., complete repair of TOF was performed on 47 children from developing countries at a mean age of 4.8 ± 3.2 years, with a postoperative mortality rate of 4.2% [22].

However, an interesting contrast can be seen in Pakistan, where Waqar et al. reported on a large cohort of 307 children who underwent TOF repair at a mean age of 9.6 ± 4.9 years. The 30-day mortality rate in that study was 1.3%, similar to rates reported in developed nations [23]. In Europe and North America, perioperative mortality for TOF is less than 3% due to improved management strategies [2]. The outcomes observed in various developing countries can partially be attributed to factors intrinsic to the characteristics of patients seen, the experience and expertise of the healthcare centers and systemic factors outside the disease that contribute to higher mortality rates [23]. This was demonstrated in a cohort of 47 African patients who were operated on in France, which exhibited a low mortality rate of 3.2%, comparable to that of local patients, despite being older than the 90 French patients [22]. Therefore, as emerging centers in low- and middle-income countries gain more experience and handle larger patient volumes, and health systems improves to ensure early detection and treatment of patients with CHD we expect improved outcomes over time.

Our cohort’s median age at repair was three years. As anticipated, only 19.6% of patients who underwent primary TOF complete repair were younger than one year of age. In developed countries, in contrast, more than 90% of operations are conducted on patients younger than one year of age [24]. Age at repair is important. The Toronto group reported the safety of surgery between 3 and 11 months of age, while a risk of death was associated with surgery at 12 + months [25]. Our study confirmed these findings, as no mortalities were observed before one year of age. Nevertheless, a later age for TOF repair is a common trend in most developing nations. In Iran, the mean age of operation for TOF patients was four years. In Brazil, a cohort of 83 TOF patients had a mean age at operation of 3.7 years. Similarly, Turkey’s mean age at operation was 2.3 years [26, 27, and 28]. Insufficient screening and access to echocardiography in rural health canters of developing countries act as barriers to early detection and treatment.

Early repair is crucial as it can alleviate the effects of cyanosis and protect vital organs. Additionally, early repair prevents the obstruction of the right ventricular outflow tract (RVOT) caused by fibrosis, a risk factor for poor outcomes [10]. Consequently, patients in LMICs who undergo surgery at a later stage due to delayed presentation are more likely to experience unfavorable outcomes.

Although Tetralogy of Fallot is more common in males according to the literature and was shown in our data set to be 62.6%, female sex in our cohort was associated with 40% higher hospital mortality. We are unaware of any reports indicating higher mortality rates for females following TOF repair. However, historical reports have indicated that females are at a high risk of death postcardiac surgery [29]. Chang and Klitzner were the first to show sex differences in-hospital mortality in children undergoing cardiac CHD surgery; using data from 1989 to 1999 in California, in their study, the female sex was associated with an 18% greater risk of death [30]. A US population study examining sex differences in CHD surgical outcomes showed that female in-hospital mortality was 21% greater [31]. The cause of excess mortality in females is unclear [29,30,31].

Surgical mortality is influenced by the severity of the disease. In the case of patients with Tetralogy of Fallot (TOF) who experience deep cyanosis and higher hematocrit levels, their condition is more critical. In our study, we found that children with hematocrit levels exceeding 55% and a haemoglobin saturation below 75% was at a higher risk of mortality and experienced longer stays in the ICU and hospital. A study conducted in Houston, Texas, between 1954 and 1962, involving 203 patients with TOF, demonstrated that a high hematocrit was a reliable risk indicator. Patients with a hematocrit greater than 55% had a mortality rate of 31%, while those below 55% had a mortality rate of 10% [32]. Furthermore, a Turkish study revealed a connection between higher hematocrit levels and unfavorable outcomes, including extended hospital stays, prolonged mechanical ventilation, prolonged ICU stays, and increased occurrence of major adverse effects [33]. In Houston, a successful approach to reducing mortality in TOF surgeries involved using a Blalock-Taussig (BT) shunt to lower hemoglobin concentration from above 18 gm to below 18 gm [32]. Extended periods of cyanosis precede elevated hematocrit levels, resulting in a hypercoagulable state. This leads to low consumption coagulation factors and the emergence of consumption coagulopathy, exacerbating postoperative complications in children with cyanotic CHD. Recent studies utilizing machine learning to assess perioperative predictors of TOF outcomes have suggested that preserving right ventricular remodeling and optimizing hematocrit levels are effective strategies [34]. Therefore, for patients in low- and middle-income countries (LMICs) who present late with deep cyanosis and high hematocrit levels, it is crucial to tightly control these parameters during CPB [32, 34].

The need for trans-annular patches (TAPs) for TOF repairs can indicate disease severity and technical difficulties, resulting in longer bypass times and ICU and hospital stay [34]. In our series, TAP patients were three times more likely to experience fatal outcomes. These findings are consistent with many studies in the literature. Surgeons in North America frequently use ventriculotomy and TAP for TOF repair [35]. In Europe, TAP techniques were associated with increased mortality [36]. Notably, although desirable, valve-sparing is not achievable in most settings [35, 36]. Therefore, teams must understand the risks of TOF patients receiving TAP to provide optimal care. It is worth noting that in our study, none of the patients under one year requiring TAP died. This may be due to the fact that none of the children we operated on were less than one month old, which is the age group that typically requires emergency surgeries. The youngest patient in our study who underwent surgery was three months old. In this cohort. TOF accounts for nearly a quarter (23.8%) of all operated patients; highlighting the substantial burden of TOF in this setting.

Although there is not much documentation on the burden of TOF in LMIC, experts estimate that it is consistent with the global prevalence, where TOF makes up 7–10% of all CHD cases [1]. The excess proportion we see in our cohort may be for reasons of survival ship. Without surgery, 90% of children with CHD and TOF die within ten years, but 66% survive the first year of life [37]. We speculate that due to a lack of systematic screening for CHD, the patients we encounter in our settings represent milder forms of the disease, the survivors, while more severe cases perish at a young age before receiving a diagnosis, underscoring the importance of early detection through screening programs.

These findings, in general, indicate that there is still room for improvement in the management of CHD and particularly TOF. Nonetheless, they also highlight the resilience and dedication of patients and medical professionals in the face of challenging circumstances.

Our dataset emphasizes the importance of detecting CHD early, particularly in low- and middle-income countries (LMICs) where patients often seek medical attention at a late stage. It is crucial to carefully select cases and understand the risk factors inherent to patients with complex anatomy who require TAP insertions. By implementing a systematic screening process for CHD, including TOF, we can identify and diagnose more severe cases earlier. Furthermore, recognizing the risk factors associated with TOF and implementing strategies such as tightly controlling modifiable factors like hematocrit levels and establishing systematic screening processes for CHD may lead to excellent outcomes, reduced mortality, shorter stays in intensive care units and hospitals, and improved survival rates for individuals with TOF in LMICs.

To the best of our knowledge, this study represents the first examination of factors related to mortality in Tanzania, specifically for the total correction of TOF. However, it is important to acknowledge that this study is based on a single center, potentially limiting its findings’ generalizability to other settings. Nevertheless, the results hold significance since the Jakaya Kikwete Cardiac Institute (JKCI) currently stands as the sole center providing cardiac care for children in the country.

One limitation of this study is the unavailability of echocardiography data, neither CT scan or catheterization reports, due to loss of information, which rendered the classification of TOF severity impossible. Consequently, the researchers resorted to using TAP (Trans Annular Patch) as a means to indicate severe TOF. Moreover, this investigation did not account for additional influential factors such as cardiopulmonary bypass (CPB) time, cross clamp time, surgical expertise or intensive care unit (ICU) experience, which could potentially impact outcomes. Notwithstanding these limitations, the study offers valuable insights into the prevailing circumstances faced by TOF patients at the National Referral Center while identifying immediate factors clinicians within this facility can utilize to enhance outcomes. However, it is crucial to recognize that this study underscores the necessity for a prospective study, encompassing a comprehensive analysis of all factors associated with outcomes, to gain a deeper understanding of this commonly occurring CHD and risk factors for outcome within the Tanzanian context.