Tetralogy of Fallot (TOF) is a congenital heart defect characterized by a ventricular septal defect (VSD), pulmonary stenosis, right ventricular (RV) hypertrophy (RVH), and an overriding aorta [1]. Currently, surgical correction of TOF is critically important, with timely and effective surgery being essential for achieving favorable long-term outcomes [2].

TOF is present in 3 out of every 10,000 live births and is the most prevalent cause of cyanotic heart disease in individuals beyond the newborn stage, representing up to 10% of all congenital heart anomalies [3].

Globally, TOF constitutes 3–5% of congenital heart defects, with its occurrence varying from 0.4–2.1% in Europe, 3–8% in China, and approximately 6.7% in the USA. In contrast, Sub-Saharan Africa exhibits higher rates, ranging from 5–20% across various regions, underscoring the necessity for improved regional data to inform healthcare planning [4].

Due to the complexity and prevalence of TOF, comparing various surgical repair methods is crucial to enhance patient care. Specifically, evaluating the traditional use of transannular patches (TAPs) against valve-sparing (VS) repair (VSR) techniques is a key research focus [5]. TAPs are commonly employed to alleviate RV outflow tract (RVOT) obstruction (RVOTO) during surgery, but are often linked to postoperative issues like pulmonary regurgitation and RV dysfunction [6]. Conversely, VS procedures have emerged as a potential solution to mitigate these adverse effects, necessitating comparison to identify the optimal surgical approach [7].

This review aims to summarize current findings regarding the advantages and disadvantages of TAP versus VSRs, thereby establishing the role of each method in contemporary practice [8]. Identifying the most effective surgical technique for TOF treatment in clinical settings is crucial. The choice of surgical method directly affects patient outcomes, including mortality, quality of life, and the occurrence of postoperative complications such as RV dysfunction and pulmonary valve insufficiency [9]. Therefore, a thorough analysis of existing literature not only informs surgical practices but also guides healthcare providers in making decisions for treating congenital heart defects [10]. Ultimately, clarifying the outcomes of VSRs compared to TAP will enhance understanding of the best management strategies for TOF patients [11].

TOF is a cyanotic congenital heart defect characterized by four anatomical abnormalities. These include a large, non-restrictive VSD, an RVOTO that can be subvalvular, subinfundibular, valvular, or supravalvular, the aortic root overriding the ventricular septum, and RVH [3]. It consists of four distinct heart defects that primarily affect infants and children. Babies with TOF struggle to get sufficient blood to their lungs, resulting in the body receiving blood with low oxygen levels. The four defects in TOF include: 1. pulmonary stenosis, where a narrowed or stiffened pulmonary valve hinders the pulmonary artery from delivering adequate blood from the heart to the lungs; 2. VSD, which is a hole between the ventricles allowing the mixing of oxygen-rich and oxygen-poor blood; 3. overriding aorta, where the aorta is positioned above the ventricles, leading to insufficient oxygen-rich blood reaching the body; and 4. RVH, where the right ventricle is abnormally thick, making it difficult for blood to pass through the pulmonary valve (Figure 1). These defects result in poor blood oxygenation, causing cyanosis, a bluish discoloration of the lips, skin, and nails [11]. Notably, TOF has favorable survival rates following surgical intervention. Additionally, the age of the patient is crucial in surgical planning, with complete repair associated with better outcomes than staged repair [12]. The causes of TOF are multifactorial, with genetics playing a significant role. It is linked to the deletion of the 22q11.2 gene [13], along with other mutations such as trisomy 21, Alagille syndrome, Cat Eye Syndrome, or CHARGE and VATER/VACTERL syndromes. Variants in the key cardiac transcription factor NKX2.5 were the first to be identified as a genetic cause of TOF [14].

In addition to genetic abnormalities, a rubella infection in the mother is a significant factor contributing to TOF. If the mother contracts the infection during the first trimester, it can result in congenital rubella syndrome, which includes serious birth defects like congenital heart defects, such as TOF [15]. The precise role of prenatal rubella infection or genetic factors in causing TOF remains unclear [15]. The severity of the right-to-left shunt is influenced by the pressure difference between the right and left ventricles and the RVOTO. Dynamic RVOTO, often caused by muscle spasms, can worsen under stress, leading to cyanotic episodes. A reduction in systemic vascular resistance (SVR) or an increase in pulmonary vascular resistance (PVR) can further exacerbate the shunt. Despite the desaturation, cardiac output is usually maintained initially. RVH results in diastolic dysfunction, making the heart dependent on venous return and sensitive to tachycardia, which decreases filling and raises oxygen demand [14].

TOF typically manifests with mild to moderate cyanosis, which becomes apparent as the obstruction in the right ventricle worsens. Patients experience cyanosis without signs of respiratory distress or symptoms of congestive heart failure, such as poor feeding, failure to thrive, or sweating, because the obstruction affects only pulmonary blood flow. Due to the RVOTO, the second heart sound is heard as a single, loud sound accompanied by a harsh systolic ejection murmur [3].

The primary clinical feature of TOF is the occurrence of hypercyanotic episodes, also known as “tet spells”. These episodes are characterized by a sudden and severe drop in oxygen saturation, along with symptoms like intense cyanosis, rapid and shallow breathing (hypercapnia), fainting, lethargy, and limpness. These symptoms typically appear between 2 and 6 months of age, especially during periods of agitation, crying, or dehydration, which exacerbate the RVOTO [3]. Infants often adopt a knee-to-chest position to increase SVR and improve blood flow to the lungs.

In older children, exertional dyspnea and gradually worsening cyanosis are observed, and they may squat during physical activity to alleviate symptoms [16]. In adults, if TOF remains uncorrected, complications such as heart failure, atrial and ventricular arrhythmias, and infective endocarditis can develop [16, 17].

The TAP repair method has existed since the 1990s for addressing RVOTO. It is particularly favored for patients with significant pulmonary annulus hypoplasia and severe RVOTO [11, 18]. The TAP procedure typically involves making an incision from the main pulmonary artery to the infundibulum, allowing surgeons to access the constricted outflow tracts. To gain deeper access into the infundibulum, the RV muscle is excised, and the pulmonary valve leaflet tissue is either partially or entirely removed. Patch material is then used to reconstruct the RVOT, extending to the bifurcation of the pulmonary arteries. While this procedure effectively removes the obstruction, it results in notable insufficiency in pulmonary circulation. Postoperative ICU stay was on average 1–2 days longer for TAP patients compared with those undergoing VSR in the cohort of 11,723 patients, due to underlying RVH, diastolic dysfunction, and the low cardiac output associated with diastolic dysfunction [5, 18–20]. A significant benefit of TAP is its capacity to immediately address RV hypertension [21, 22]. Although TAP can alleviate RV tract obstruction, pulmonary regurgitation remains the most common complication [23].

In response to the limitations of TAP and its long-term effects, VSR techniques have been developed as a superior alternative, aiming to preserve the native valve function and minimize post-operative dysfunctions. Surgeons perform VSR surgery to address slightly narrowed pulmonary valves, keeping the valves intact [24]. To preserve the valves, several techniques are employed, such as commissurotomy, delamination plasty, and T-shaped infundibulotomy [11, 25]. Compared to the TAP procedure, VSR offers significant advantages, including a reduced risk of pulmonary regurgitation, a lower likelihood of future reoperations, and a decreased risk of developing arrhythmias [11, 24]. Patients who underwent VSR did not require additional surgical or interventional procedures [11].

TOF is a complex congenital heart condition with various symptoms that tend to worsen over time. Accurate surgical procedures with minimal complications are essential. One such symptom, RVOTO, can be promptly addressed with TAP repair. However, this method may lead to complications such as pulmonary regurgitation and RV dysfunction. Although valve sparing is currently popular and frequently utilized, the TAP repair remains the most commonly employed method for correcting TOF. This dominance is largely attributed to its historical significance as one of the earliest surgical techniques for TOF correction, making it a well-established and familiar approach, particularly in developing and underdeveloped countries. This is due to factors such as limited access to modern and advanced surgical equipment, cost-effectiveness, and the ease with which it can be implemented. VSRs offer significant advantages, including improved long-term survival, maintained valve function, and a lower risk of arrhythmias, ultimately enhancing the patient’s quality of life. Consequently, VSR is considered a superior surgical option compared to TAP.