In this retrospective single-center study, we proposed a simple anatomic classification based on the size of the pulmonary valve annulus and pulmonary artery branches. We evaluated its impact on the subsequent requirement of surgical or interventional procedures, and on adverse cardiac events at medium term follow-up.
In the last decades, many efforts have been made with the aim to optimize and standardize the surgical treatment of TOF, in order to improve short-term and long-term results [9, 10]. The ideal TOF repair should be suitable for infants and should provide good relief of the RVOT obstruction, atrial and ventricular septation. It should also avoid an extensive ventriculotomy and last but not least, it should preserve the function of the pulmonary valve. Nowadays, the transatrial or transatrial-transpulmonary approach is utilized in most centers with excellent results. Neonatal repair is feasible with acceptable results, but it more often requires transannular patch, resulting in worse event-free survival .
Tetralogy of Fallot palliation in the current era is restricted to a limited group of patients, most of them are neonates or babies with small body weight. In our study, only 16% of the patients required a palliative procedure (BT shunt) before primary repair, and this percentage is compatible with most of the recent experiences from many other centers [12,13,14,15]. Also, in conformity with the current literature, our approach of primary repair with TAP during infancy is the most commonly used . Lastly, it is known that the TAP is the preferred procedure mainly in patients with hypoplastic PV annulus , and this was indeed also the most frequent repair in our cohort of patients (68%). Repair without ventriculotomy (19% of cases) and repair with infundibular patch (16% of cases) were the other common techniques that we used.
Although it’s well established that TOF presents a wide range of anomalies, the follow-up recommendations, mainly in adult patients, are tailored more on the postoperative results  without taking in account the native anatomy. In our population, we tested the impact of a simple anatomical classification on the surgical history and mid-term outcomes of patients who underwent TOF repair. In the setting of pre-operative native anatomy, in group 1 (normal size PV annulus and PAs) only 4 (6%) patients required a TAP. In 2 of them, the annulus was normal in size but the commissurotomy was inadequate due to severe valve dysplasia while in the others 2 patients the annulus was intraoperatively found to be smaller than expected from preoperative echocardiogram. Conversely in group 2 and 3 most of the patients received a TAP, 91% and 94% respectively, with 46 patients (70%) in group 3 requiring also a PAs enlargement due to hypoplastic branches. Patients from group 1 and group 2 almost never required PAs enlargement.
When considering mid-term follow up, the patients in group 1 had a low incidence of surgical re-interventions (5.7%) and only 1 required an interventional procedure. Freedom from any procedure was 98% at 5 years, 92% at 10 years and 92% at 20 years (Fig. 1), with no adverse events. These results show that a favorable anatomy, defined as PV and PAs size with z-score more than -2, leads to very low incidence of reoperations or interventional procedures an no significant adverse events in the following years. Conversely a significant higher incidence of surgical or interventional procedures was found in group 2 and 3. For group 2, freedom from any procedure was 89.3% at 5 years, 85.5% at 10 years and 69.1% at 20 years (Fig. 1). Most of the cases required surgical re-interventions to relieve RVOT restenosis at mid-term follow-up and to readdress PV regurgitation in long term follow-up. Only 2 (2.3%) patients required multiple procedures. In this group, the number of interventional procedures was limited to 5, mainly PAs balloon angioplasties and RVOT stent implantation. In the same group, only 3 patients experienced adverse cardiac events. In group 3 freedom from any procedure was 61.7% at 5 years, 53.6% at 10 years and 26.3% at 20 years. These patients required re-interventions due to PV regurgitation and/or RVOTO and/or stenosis of PAs. Among them, 20% required multiple combined surgical and interventional procedures, and 5 patients (12.2%) underwent 3 or 4 repeated procedures. In terms of adverse cardiac events, only one patient presented signs of heart failure 20 years later.
In the present study, PV annulus hypoplasia was an independent predictor for redo surgical procedures, in accordance with previous studies ; while PAs hypoplasia was an independent predictor of subsequent interventional procedures.
In this study we propose a simple anatomical classification that could be provided by a routine echocardiogram study focused on the size of the pulmonary valve annulus and pulmonary artery branches. In our population, we found a helpful correlation between this classification and the surgical results and mid-term outcomes. Actually, patients with preserved PV function and without residual stenosis (group 1), no adverse events or subsequent re-interventions occurred after 5 years, and in most of them even after 10 years. PV hypoplasia is the most frequent anatomical feature and surgical treatment inevitably requires a TAP with possible consequent PV regurgitation. In patients with TAP and normal size PAs (group 2), the number of re-interventions within 5 years was low and mainly due to residual RVOT obstruction; patients with PV and PAs hypoplasia (group 3), are the most challenging, as they underwent more frequently surgical and/or interventional procedures after the complete repair.
If these findings would be confirmed by larger prospective multicenter randomized studies, it would be reasonable to tailor both the counseling and the follow-up of patients who undergo TOF repair according to the native anatomy rather than according to a standardized protocol. For instance, in TOF patient with TAP and good size PAs without residual stenosis, even if with so-called “free pulmonary regurgitation”, would require very few cardiology out-patient clinics, at least in the first 5 years post-surgical repair. Because of the quite small sample size and the limited follow-up time we couldn’t assess the impact of the anatomical classification on long-term adverse outcomes. However, previous studies identified multiple cardiac operations as one of the risk factors for ventricular tachycardia and SCD  therefore we could speculate that the risk for adverse outcome of patients in the group 3 (with more subsequent operations) could be higher in comparison with the others 2 groups.
We acknowledge that our study presents the limitations of the retrospective nature and of the relatively low sample size, however the fact all patients were operated in the same center certainly reduces surgical strategy bias. Patients lost at follow-up were older compared with the remaining population, therefore the long-term results should be interpreted cautiously. Larger longitudinal studies are warranted to better investigate the impact of the native anatomy on adverse outcomes at long-term follow-up in this challenging population.