Cardiac catheterizations (CC) in the early postoperative period after congenital heart surgery (CHS) are proclaimed to be high-risk procedures associated with an elevated rate of morbidity and mortality [1–5]. This is due to early postoperative hemodynamic instability and vulnerability, especially in young patients and children. Therefore, CCs during the early postoperative period are often avoided or postponed. Nevertheless, unsatisfying outcomes after congenital heart surgery will in some cases necessitate re-operations or transcatheter interventions in the immediate postoperative period [1–9]. Yet, early cardiac transcatheter interventions may be the safest procedural option, especially in critically ill children in whom re-operations on cardiopulmonary bypass in quick succession are deemed to be of even greater risk [6–9]. Considering the limited data available in the literature [1–9], we propose to evaluate indications, feasibility, safety, and outcome of early CC within 30 days after CHS in children at our institution over an 11-year period. During the assessed period (from 2010 to 2020), the interventional lead and team of the CC laboratory with its standards, know-how, and technical options remained unchanged.

A total of 317 (138 diagnostic, 179 interventional) postoperative CCs were performed in 245 patients during January 2010 and December 2020. There was a total of 3247 CHS within this period, giving a rate of early postoperative CC of 9.7%. The study includes a median follow-up period of 1.7 years (IQR 2.9) after the postoperative CC. Preceding cardiac surgeries and cardiac anatomies are detailed in Table 1.

A total of 194 procedures (61.2%) were performed in patients with univentricular heart disease. Median age at catheterization was 3 months (IQR 6); median weight was 5 kg (IQR 4); sex was male in 190 (59.9%) and CC were performed at a median of 4 days (IQR 13) after CHS. Indications to perform early CC are detailed in Table 2.

Hypoxaemia, suspected pulmonary artery stenosis, prolonged postoperative course, suspected coronary artery abnormalities, diagnostic after BCPC and ECMO/HLM weaning failure were the most frequent.

There is a variety of different possible post-operative problems or residual lesions after CHS and some surgical outcomes after CHS in children need further, early and often invasive diagnostic investigation or interventional transcatheter treatment [11–13]. The threshold to perform further investigations, including invasive CC studies should be low, if significant hemodynamic or clinical problems are observed in the early post-operative period. A benefit of CC is the correct delineation of the anatomy and physiology, which allows for effective therapy; thus, a substantial number of patients undergo reoperation based on the findings during CC. Furthermore, medical, and interventional treatments performed will have a positive effect, optimizing postoperative therapy of these patients.

Earlier studies of post-operative CC in children [1–9] mainly described the feasibility and safety of early post-operative CC, but to our knowledge did not focus on indications and likeliness for interventional treatment according to the previously performed surgery. As to the diverse surgical strategies, different underlying anatomies, and different preceding surgeries it is imminent, that the assessed study population is heterogeneous. Therefore, we aimed to analyze a period of 11-year, where (at least) the interventional lead and team of the CC laboratory with its standards and interventional philosophy have been stable.

In case of CHS with preceding RV-PA conduit surgery, suspected pulmonary artery (PA) stenosis or hypoxia seem valid indications for a CC, since this could be resolved with an intervention in more than 70% of the cases and up to 80% of the patients showed a significant clinical benefit after the intervention. On the other hand, angiographic visualizations of coronary arteries after ASO and/or arrhythmias mostly confirmed a good postoperative result without the need for transcatheter interventional treatment. In 6 patients after ASO, where the indication for CC was coronary angiography, the performed interventions (“consequences”) were coil occlusions of significant residual MAPCAs, which can mimic coronary undersupply due to diastolic runoff [14].

Interestingly, approximately 61% of interventions were performed in the group of single ventricle physiology patients at different stages of their palliation. This is despite the fact, that it is institutional practice to perform CC prior to BCPC and TCPC. In the patients after TCPC the rate of interventions following diagnostic CC was around 50% and mostly involved treatment of vessel stenosis (pulmonary artery) associated with prolonged postoperative course. Nevertheless, when a CC intervention was performed its clinical impact was high. Interestingly, diagnostic angiography without any clinical problem post TCPC surgery showed normal results in most cases. The cohort after BCPC reflects the largest group in our study and involves 69 patients. In this group, there were solid indications for CC, such as hypoxemia or suspected PA-stenosis on echocardiography, which were associated with vessel stenosis and with a very high rate of interventions as well as a significant clinical impact after the catheter procedure.

The patients after a Norwood procedure had various indications for CC and a lower interventional rate compared to the other groups. Independently from the indication for CC, vessel stenosis or shunt occlusion were the most frequent findings, but the associated clinical impact of their treatment was lower than in other groups. Lastly, the patients after AP-shunt showed, that suspected shunt dysfunction is associated with a high and urgent need of reintervention, which lead to a clinical benefit in more than 70% of the cases.

Our study showed that these early high-risk CC interventions mostly can be performed safely and target-oriented, with no intra-procedural mortality. There was a total of 29 (9.1%) intra-procedural and 37 (11.6%) post-procedural adverse events. Most of these events were minor complications, while only 9 (2.8%) intra-procedural events stratified as major complications [10]. These occurrence rates of AEs are comparable to reported rates in normal, elective CC procedures in children in the literature [15,16]. Regarding this, early post-operative CC should not be postponed. Nevertheless, these interventions should be considered high-risk and procedural preparation and a multi-disciplinary approach with good surgical and intensive care back-up are essential.

This is a retrospective, single center analysis and therefore limitations regarding relatively small numbers of patients which limits subgroup analysis and risk factor analysis are imminent to this study. The gold standard of a prospective, randomized control study is ethically not applicable in this population, and we think that the results of our study are important to justify CC in the early post-operative period, although they are considered to be high risk interventions. Nevertheless, the lack of a control group especially limits the interpretation of the impact of these procedures on outcome and clinical improvement of these patients in the early post-operative period.

Cardiac catheterizations in the early postoperative period after CHS can be performed safely and should not be withheld from patients after CHS. Hypoxemia suspected arterial stenosis and prolonged postoperative course are solid indications for CC after RV-PA shunt, TCPC and BCPC. After ASO a CC only sporadically results in an intervention. Suspected AP-shunt dysfunction had a high probability for the necessity of an interventional transcatheter treatment.