409 PROFESSIONAL ARTICLE Definition of the complications of cardiac catheterization in children in Slovenia Copyright (c) 2023 Slovenian Medical Journal. This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License. Definition of the complications of cardiac catheterization in children in Slovenia Opredelitev zapletov srčnih kateterizacij pri otrocih v Sloveniji Laura Kekec,1 Rina R Rus,2,3 Gorazd Mlakar,2,3 Miroslav Elek2,3 Abstract Background: Although cardiac catheterizations are less invasive compared to cardiac surgical procedures, they have few- er complications, and patients recover faster after them, they are not without complications. With our research, we wanted to identify the population’s characteristics, the most common pathologies, types of catheterizations, and complications during catheterizations in our centre, and identify possible risk factors. Methods: We collected data on all pediatric cardiac catheterizations performed between June 2018 and August 2021. We defined them according to the type of catheterization (diagnostic and therapeutic), weight, age, and sex of the patients, and complexity of pathology. Complications were divided into major and minor, and using the Pearson chi-square test and the Mann-Whitney U test, we determined their correlation with the possible risk factors. Results: During the mentioned period, 191 cardiac catheterizations (54 diagnostic and 137 therapeutic) were performed in 175 children, of which 95 were boys, and 80 were girls. The children were between a few hours and 18 years old and weighed between 2.6 kg and 85.5 kg. We recorded 9 complications; 5 were major and 4 were minor. With our research, we did not demonstrate a statistically significant relationship between risk factors (body weight, sex, type of catheterization, age of patients, complexity of pathology) and the occurrence of complications. Conclusion: Most catheterizations were performed in children aged between 1 and 10 years and those weighing between 10 and 40 kg. Slightly more catheterizations were performed in boys; the most frequent were therapeutic catheterizations. The incidence of complications in our centre is comparable to other centres. In our centre, we did not determine the correlation between body weight, sex, type of catheterization, age, the complexity of the pathology, and the incidence of complications. 1 University Medical Centre Ljubljana, Ljubljana, Slovenia 2 Department of Cardiology, Division of Pediatrics, University Medical Centre Ljubljana, Ljubljana, Slovenia 3 Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia Correspondence / Korespondenca: Laura Kekec, e: laura.kekec@gmail.com Key words: congenital heart defect; interventional cardiology; outcomes; risk factors; pediatrics Ključne besede: prirojene srčne bolezni; intervencijska kardiologija; izidi; dejavniki tveganja; pediatrija Received / Prispelo: 7. 10. 2022 | Accepted / Sprejeto: 20. 4. 2023 Cite as / Citirajte kot: Kekec L, Rus Rina R, Mlakar G, Elek M. Definition of the complications of cardiac catheterization in children in Slovenia. Zdrav Vestn. 2023;92(9–10):409–19. DOI: https://doi.org/10.6016/ZdravVestn.3390 eng slo element en article-lang 10.6016/ZdravVestn.3390 doi 7.10.2022 date-received 20.4.2023 date-accepted Cardiovascular system Srce in obtočila discipline Professional article Strokovni članek article-type Definition of the complications of cardiac catheterization in children in Slovenia Opredelitev zapletov srčnih kateterizacij pri otro- cih v Sloveniji article-title Definition of the complications of cardiac catheterization in children in Slovenia Opredelitev zapletov srčnih kateterizacij pri otro- cih v Sloveniji alt-title congenital heart defect, interventional cardiol- ogy, outcomes, risk factors, pediatrics prirojene srčne bolezni, intervencijska kardiologi- ja, izidi, dejavniki tveganja, pediatrija kwd-group The authors declare that there are no conflicts of interest present. Avtorji so izjavili, da ne obstajajo nobeni konkurenčni interesi. conflict year volume first month last month first page last page 2023 92 9 10 409 419 name surname aff email Laura Kekec 1 laura.kekec@gmail.com name surname aff Rina R Rus 2,3 Gorazd Mlakar 2,3 Miroslav Elek 2,3 eng slo aff-id University Medical Centre Ljubljana, Ljubljana, Slovenia Univerzitetni klinični center Ljubljana, Ljubljana, Slovenija 1 Department of Cardiology, Division of Pediatrics, University Medical Centre Ljubljana, Ljubljana, Slovenia Služba za kardiologijo, Pediatrična klinika Ljubljana, Univerzitetni klinični center Ljubljana, Ljubljana, Slovenija 2 Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia Medicinska fakulteta, Univerza v Ljubljani, Ljubljana, Slovenija 3 Slovenian Medical Journallovenian Medical Journal 410 CARDIOVASCULAR SYSTEM Zdrav Vestn | September – October 2023 | Volume 92 | https://doi.org/10.6016/ZdravVestn.3390 1 Introduction Cardiac catheterization is a procedure in which an operator inserts a thin, flexible tube (catheter) through a vessel (artery or vein) into the heart. When catheter- izing the right heart, the catheter is inserted antegrade through the vein (mostly femoral vein in children) and in catheterization of the left heart retrogradely through the artery (mostly femoral artery in children). Cardiac catheterizations can be diagnostic, in which structures are visualized with the help of X-ray and contrast dye, and pressures and blood oxygen saturation are mea- sured. Moreover, they can be therapeutic when a pro- cedure is performed to resolve a pathological condition, which in pediatric cardiology means the creation of in- ter-atrial communication, closure of the PDA (patent ductus arteriosus), ASD (atrial septal defect), PFO (pat- ent foramen ovale), or VSD (ventricular septal defect), balloon dilation of narrowed vessels and valves, inser- tion of stents into vascular and cardiac structures, and insertion of biological valves. Because cardiac catheterizations are less invasive compared to cardiac surgery, have fewer complications and patients recover faster, they are being performed more and more frequently. Sometimes, they can also allow for a temporary improvement of the heart defect, which can postpone an otherwise necessary surgical in- tervention to a later time. Despite the less invasive nature of cardiac catheter- izations, they are not without complications. Research (1-7) has shown that complications occur in 5.5-19% of Izvleček Izhodišča: Čeprav so srčne kateterizacije v primerjavi s kardiokirurškimi posegi manj invazivne, imajo manj zapletov, bol- niki pa po njih hitreje okrevajo, te niso brez zapletov. Z raziskavo smo želeli ugotoviti značilnosti populacije, najpogostejše patologije, vrste kateterizacij, zaplete pri kateterizacijah v našem centru ter opredeliti morebitne dejavnike tveganja. Metode: Zbrali smo podatke o vseh pediatričnih srčnih kateterizacijah, opravljenih med junijem 2018 in avgustom 2021. Opredelili smo jih glede na vrsto kateterizacije (diagnostične in terapevtske), težo, starost, spol bolnikov in kompleksnost patologije. Zaplete smo ločili na lažje in težje ter z uporabo Pearsonovega testa hi-kvadrat in testa Mann-Whitney U ugotav- ljali njihovo povezanost z morebitnimi dejavniki tveganja. Rezultati: V tem obdobju je bilo opravljenih 191 srčnih kateterizacij (54 diagnostičnih in 137 terapevtskih) pri 175 otrocih, od tega pri 95 dečkih in 80 deklicah. Otroci so bili stari od nekaj ur do 18 let, tehtali so od 2,6 kg do 85,5 kg. Zabeležili smo 9 zapletov, od tega 5 težjih in 4 lažje. Z našo raziskavo nismo dokazali statistično pomembne povezave med dejavniki tve- ganja (telesna teža, spol, vrsta kateterizacije, starost, kompleksnost patologije) in pojavom zapletov. Zaključek: Največ kateterizacij je bilo opravljenih pri otrocih, starih med 1 letom in 10 let in tistih, ki so tehtali med 10 in 40 kg. Nekoliko več kateterizacij je bilo opravljenih pri dečkih. Najpogostejše so bile terapevtske kateterizacije. Pojavnost zapletov v našem centru je primerljiva z drugimi centri. Telesna teža, spol, starost otroka, vrsta kateterizacije in komple- ksnost patologije v našem centru niso bili statistično značilno povezani s pojavom zapletov ob katerizaciji. pediatric cardiac catheterizations, with 1.4-6.2% being major, potentially life-threatening, and 4.1-16.3% mi- nor, resolved with or without treatment. Mortality of paediatric cardiac catheterizations is 0.14-0.4% (1-7). The most frequently recorded are arrhythmias, bleed- ing, vein thrombosis, device embolization, and perfora- tion of the heart walls or vessels (1-7). With the research, we wanted to determine the char- acteristics of the population, the most common pa- thologies, types of catheterizations, and complications during catheterizations in our centre, and identify po- tential risk factors. 2 Methods Our research took place at the Cardiology Depart- ment of the Paediatric Clinic in Ljubljana. We retro- spectively collected data on cardiac catheterizations from the files of children with heart disease aged 0 to 18 years. In the research we included those children who underwent cardiac catheterization between June 2018 and August 2021. We separated catheterisations into di- agnostic or therapeutic and classified each into 4 main groups: isolated cyanotic and acyanotic congenital heart defects (CHD), which are clearly defined CHD or defect associations in the literature, and combined cyanotic and acyanotic defects with the presence of at least two different CHD that are individually described in the lit- erature. We also calculated the share that an individual 411 PROFESSIONAL ARTICLE Definition of the complications of cardiac catheterization in children in Slovenia Property Value Diagnostic n (%) Therapeutic n (%) Combined n (%) Age < 1 month 3 (5.6) 20 (14.6) 23 (12.0) 1-11 months 9 (16.7) 21 (15.3) 30 (15.7) 1-9,9 years 24 (44.4) 66 (48.2) 90 (47.1) ≥ 10 years 18 (33.3) 30 (21.9) 48 (25.1) Sex Men 37 (68.5) 71 (51.8) 108 (56.5) Female 17 (31.5) 66 (48.2) 83 (43.5) Weight < 4 kg 1 (1.9) 21 (15.3) 22 (11.5) 4-9,9 kg 12 (22.2) 26 (19.0) 38 (19.9) 10-39,9 kg 23 (42.6) 62 (45.3) 85 (44.5) ≥ 40 kg 18 (33.3) 28 (20.4) 46 (24.0) Table 1: Characteristics of the population undergoing cardiac catheterization. pathology or a group of pathologies represents within the type of catheterization. Next, we analyzed inter- ventions that were performed during therapeutic cath- eterizations. We divided them into three main groups: closure devices use, balloon dilatations, and other therapeutic catheterizations. For each group, we listed which procedures and how often they were performed and calculated the proportion of all procedures per- formed as part of therapeutic catheterizations (with one therapeutic catheterization, several procedures could be performed). For ASD and/or PFO closure, we used Amplatzer septal occluders (Abbot, United States of America); for PDA closure MReye Flipper Coil (COOK Medical, United States of America) and Amplatzer PDA closure devices (ADO I, ADO II, Piccolo) (Abbot, Unit- ed States of America). Z5 atriseptostomy balloon cathe- ters with a balloon size of 13.5 mm (NuMed, Lebanon) were used for atrioseptostomies. Following, we focused on the number of complica- tions. We divided them into major and minor compli- cations and calculated their share. Following the exam- ple of foreign literature (1,2,7), we defined more severe complications as those that are potentially life-threat- ening and require immediate treatment (for example, complications that require intervention or surgery, blood transfusion, more severe infections, more severe arrhythmias that cause decompensation), and minor complications are those that are not life-threatening and resolve on their own or with specific treatment (for example bleeding that stops after a few minutes, arrhythmias that stop on their own or after specific treatment and do not cause decompensation). We fo- cused on complications arising from the catheterization procedure and excluded those arising from anesthesia. We also took into account the type of catheterization (diagnostic, therapeutic), sex, age, body weight of the children and the complexity of pathology, determining whether any of these factors are correlated with the oc- currence of complications. To calculate the statistical significance of the correla- tion of the occurrence of complications with the type of catheterization and sex, we used the Pearson chi-square test. The Mann-Whitney U test was used to calculate the statistically significant correlation of age, weight, and complexity of pathology. The p-value was calculated based on the total number of complications (major and minor combined) in each category. A value of p < 0.05 was used as the limit of statistical significance. 3 Results 3.1 Population Between June 2018 and August 2021, 191 cardiac catheterizations were performed in our centre in 175 children, 95 boys (M) and 80 girls (F). The children ranged in age from a few hours to 18 years, with a medi- an age of 5 years (interquartile range (IQR) = 9.1 years). They weighed between 2.6 kilograms (kg) and 85.5 kg; the median body weight was 17.9 kg (IQR = 31.7 kg) (Table 1). 412 CARDIOVASCULAR SYSTEM Zdrav Vestn | September – October 2023 | Volume 92 | https://doi.org/10.6016/ZdravVestn.3390 Legend: HLH –hypoplastic left heart; TOF – tetralogy of Fallot; TGA – transposition of great arteries; VSD – ventricular septal defect; PDA – patent ductus arteriosus; ASD – atrial septal defect; PFO – patent foramen ovale; AVSD – atrioventricular septal defect; AV – aortic valve; PAPVC – angl. partial anomalous pulmonary venous connection. PATHOLOGY MALE n (%) FEMALE n (%) TOTAL n (%) Isolated cyanotic defects 8 (24.2) 6 (37.5) 14 (28.6) HLH 7 (21.2) 1 (6.3) 8 (16.3) Truncus arteriosus 0 3 (18.8) 3 (6.1) TOF 0 2 (12.5) 2 (4.1) TGA 1 (3.0) 0 1 (2.0) Isolated acyanotic defects 11 (33.3) 5 (31.3) 16 (32.7) Coarctation of the aorta 4 (12.1) 0 4 (8.1) VSD 3 (9.1) 0 3 (6.1) Coronary artery diseases 1 (3.0) 2 (12.5) 3 (6.1) PDA 1 (3.0) 1 (6.3) 2 (4.1) ASD/PFO 0 1 (6.3) 1 (2.0) AVSD 1 (3.0) 0 1 (2.0) AV stenosis 1 (3.0) 0 1 (2.0) PAPVC 0 1 (6.3) 1 (2.0) Combined cyanotic defects 7 (21.2) 3 (18.8) 10 (20.4) Combined acyanotic defects 7 (21.2) 2 (12.5) 9 (18.4) TOGETHER 33 (100.0) 16 (100.0) 49 (100.0) Table 2: Initial pathologies of patients who underwent diagnostic catheterization. 3.1.1 Diagnostic catheterizations A total of 54 diagnostic catheterizations were per- formed (M:37, F:17) in 49 children (M:33, F:16). Re-catheterization was required five times, once in a girl and four times in boys (of which twice in the same boy). Children were aged 5 days to 18 years, with a me- dian age of 6.75 years (IQR = 11.4 years). They weighed between 3.9 kg and 80.4 kg, with a median weight of 20.7 kg (IQR = 32.9 kg) (Table 1). 3.1.2 Therapeutic catheterizations There were 137 therapeutic catheterizations (M:71, F:66) performed in 127 children (M:63, F:64). There were ten therapeutic re-catheterizations, twice in girls and 8 times in boys (of which twice in the same boy). One of the boys had previously undergone a diagnos- tic catheterization. The children were aged from a few hours to 17 years, with a median age of 4 years (IQR = 8.5 years). They weighed from 2.6 kg to 85.5 kg, with a median weight of 17.2 kg (IQR = 30.0 kg) (Table 1). 3.2 Initial pathologies 3.2.1 Diagnostic catheterizations Table 2 shows the types of heart defects in children who underwent diagnostic catheterization; 32 cathe- terizations were performed in children with isolated heart defects, and 22 catheterizations in children with combined heart defects. 413 PROFESSIONAL ARTICLE Definition of the complications of cardiac catheterization in children in Slovenia Legend: TGA – transposition of great arteries; DORV – double outlet right ventricle; TOF – tetralogy of Fallot; HLH – hypoplastic left heart; ASD – atrial septal defect; PFO – patent foramen ovale; PDA – patent ductus arteriosus; AV – aortic valve; PV – pulmonary valve. PATHOLOGY MALE n (%) FEMALE n (%) TOTAL n (%) Isolated cyanotic defects 7 (11.1) 5 (7.8) 12 (9.4) TGA 3 (4.8) 2 (3.1) 5 (3.9) DORV 2 (3.2) 1 (1.6) 3 (2.4) TOF 0 1 (1.6) 1 (0.8) HLH 1 (1.6) 0 1 (0.8) Truncus arteriosus 1 (1.6) 0 1 (0.8) Pulmonary atresia 0 1 (1.6) 1 (0.8) Isolated acyanotic defects 43 (68.3) 47 (73.4) 90 (70.9) ASD/PFO 12 (19.0) 20 (31.2) 32 (25.2) PDA 7 (11.1) 13 (20.3) 20 (15.7) AV stenosis 9 (14.3) 5 (7.8) 14 (11.0) PV stenosis 10 (15.9) 4 (6.3) 14 (11.0) Coarctation of the aorta 3 (4.8) 4 (6.3) 7 (5.5) Aortic arch stenosis 2 (3.2) 0 2 (1.6) Interruption of the aortic arch 0 1 (1.6) 1 (0.8) Combined cyanotic defects 10 (15.9) 6 (9.4) 16 (12.6) Combined acyanotic defects 3 (4.8) 6 (9.4) 9 (7.1) TOGETHER 63 (100.0) 64 (100.0) 127 (100.0) Table 3: Initial pathologies of patients who underwent therapeutic catheterization. 3.2.2 Therapeutic catheterizations Table 3 shows the types of heart defects in children who underwent therapeutic catheterization; 110 cath- eterizations were performed in children with isolated heart defects and 27 catheterizations in children with combined heart defects. 3.3 Procedures during therapeutic catheterizations As part of 137 therapeutic catheterizations, 143 pro- cedures were performed. Interventions as part of ther- apeutic catheterizations are shown in more detail in Table 4. 3.4 Complications Table 5 shows the number of complications according to the type of catheterization, age, gender, body weight and the complexity of the pathology. We found that the occurrence of complications is not correlated with the listed risk factors (p > 0.05). 3.4.1 Major complications We recorded embolisation of the occluder during ASD closure twice, when in one case it was necessary to remove the occluder from the femoral artery surgically, and in the other case with a catheter, which means 5.9% frequency (95% confidence interval (CI): 0.7%-19.7 %) 414 CARDIOVASCULAR SYSTEM Zdrav Vestn | September – October 2023 | Volume 92 | https://doi.org/10.6016/ZdravVestn.3390 Legend: ASD – atrial septal defect; PFO – patent foramen ovale; PDA – patent ductus arteriosus; VCS – vena cava superior; MAPCA – major aortopulmonary collateral arteries; PV – pulmonary valve; AV – aortic valve. INTERVENTION MALE n (%) FEMALE n (%) TOTAL n (%) Closing with closure devices 24 (32.9) 37 (52.9) 61 (42.7) ASD/PFO closure 13 (17.8) 21 (30.0) 34 (23.8) Closing the PDA 8 (11.0) 15 (21.4) 23 (16.1) Closing the fenestration 1 (1.4) 1 (1.4) 2 (1.4) Closing the left VCS 1 (1.4) 0 1 (0.7) Closing MAPCA 1 (1.4) 0 1 (0.7) Balloon dilations 35 (48.0) 25 (35.7) 60 (42.0) Balloon dilatation of the PV 11 (15.1) 11 (15.7) 22 (15.4) Balloon dilatation of AV 12 (16.4) 5 (7.1) 17 (11.9) Balloon dilatation of coarctation of the aorta 4 (5.5) 4 (5.7) 8 (5.6) Balloon dilatation of the pulmonary arteries 2 (2.7) 4 (5.7) 6 (4.2) Balloon dilatation of the aortic arch 3 (4.1) 1 (1.4) 4 (2.8) Balloon dilatation of the homograft 2 (2.7) 0 2 (1.4) Neoaortic balloon dilatation 1 (1.4) 0 1 (0.7) Other 14 (19.2) 8 (11.4) 22 (15.4) Balloon atrioseptostomy 11 (15.1) 7 (10.0) 18 (12.6) Insertion of the Melody (pulmonary) valve 1 (1.4) 1 (1.4) 2 (1.4) Removing the closure device 1 (1.4) 0 1 (0.7) Stent insertion into the homograft 1 (1.4) 0 1 (0.7) TOGETHER 73 (100.0) 70 (100.0) 143 (100.0) Table 4: Procedures during therapeutic catheterizations. of occluder embolisation during this procedure. We also recorded more severe bleeding with the need for blood transfusion (0.5% frequency, 95% CI: 0.01%-2.9%) and infection requiring double-line antibiotic therapy (0.5% frequency, 95% CI: 0.01%-2.9%); both complications oc- curred after diagnostic catheterizations. One perforation with cardiac tamponade during balloon atrioseptosto- my required urgent surgery (0.5% frequency, 95% CI: 0.01%-2.9%). 3.4.2 Minor complications In two cases, we recorded SVT (supraventricular tachycardia) (1.1% frequency, 95% CI: 0.1%-3.7%); these occurred during diagnostic catheterization and during balloon dilatation of coarctation of the aorta. We recorded one minor bleeding from the puncture site (0.5% frequen- cy, 95% CI: 0.01%-2.9%) and one slippage of the wire into the pericardial space, without registered apparent peri- cardial effusion (0.5% frequency, 95% CI: 0.01%-2.9%), both occurred during pulmonary valve (PV) dilatation. 3.5 Catheterization performers In our centre, most of the catheterizations were performed by three different pairs of doctors. Pair A 415 PROFESSIONAL ARTICLE Definition of the complications of cardiac catheterization in children in Slovenia Legend: OR – odds ratio; CI – confidence interval. The p-value was calculated based on the total number of complications (major and minor combined) in each category. A value of p < 0.05 was used as the limit of statistical significance. Risk factor Value Major complications n (%) OR (95% CI) Minor complications n (%) OR (95% CI) Combined n (%) OR (95% CI) Total catheterizations Type p = 0.730 Diagnostic 2 (3.7)1.72 (0.28-10.58) 1 (1.9) 0.84 (0.09-8.28) 3 (5.6) 1.28 (0.31-5.33) 54 Therapeutic 3 (2.2)1 (reference) 3 (2.2) 1 (reference) 6 (4.4) 1 (reference) 137 Age p = 0.086 < 1 month 1 (4.3)1 (reference) 2 (8.7) 1 (reference) 3 (13.0) 1 (reference) 23 1-11 months 2 (6.7)1.57 (0.13-18.48) 1 (3.3) 0.36 (0.03-4.26) 3 (10.0) 0.74 (0.14-4.06) 30 1-9.9 years 1 (1.1)0.25 (0.01-4.11) 1 (1.1) 0.12 (0.01-1.36) 2 (2.2) 0.15 (0.02-0.97) 90 ≥ 10 years 1 (2.1)0.47 (0.03-7.83) 0 1 (2.1) 0.14 (0.01-1.45) 48 Sex p = 0.530 Male 3 (2.8)1.16 (0.19-7.09) 3 (2.8) 2.34 (0.24-22.94) 6 (5.6) 1.57 (0.38-6.47) 108 Female 2 (2.4)1 (reference) 1 (1.2) 1 (reference) 3 (3.6) 1 (reference) 83 Weight p = 0.088 < 4 kg 1 (4.5)1 (reference) 2 (9.1) 1 (reference) 3 (13.6) 1 (reference) 22 4-9.9 kg 2 (5.3)1.17 (0.1-13.66) 1 (2.6) 0.27 (0.02-3.17) 3 (7.9) 0.54 (0.1-2.96) 38 10-39.9 kg 1 (1.2)0.25 (0.02-4.16) 1 (1.2) 0.12 (0.01-1.38) 2 (2.4) 0.15 (0.02-0.98) 85 ≥ 40 kg 1 (2.2)0.47 (0.03-7.83) 0 1 (2.2) 0.14 (0.01-1.44) 46 Patologija p = 0.186 Isolated defect 2 (1.4)0.22 (0.04-1.35) 3 (2.1) 1.04 (0.11-10.2) 5 (3.5) 0.41 (0.11-1.6) 142 Combined defect 3 (6.1)1 (reference) 1 (2.0) 1 (reference) 4 (8.1) 1 (reference) 49 Table 5: Number of complications according to catheterization type, age, sex, body weight and complexity of pathology. performed 88 catheterizations with 5 complications (3 minor and 2 major). Pair B performed 86 catheteriza- tions with 4 complications (2 minor and 2 major). Pair C performed 4 catheterizations with no complications. Five catheterizations were performed by other doctors, and there were no complications. 4 Discussion Between July 2018 and August 2021, 191 cardiac catheterizations were performed on children up to 18 years of age at the Paediatric Clinic of the University Hospital Ljubljana. As in many other centres (3,5,7,8), therapeutic interventions were also in majority in our case. Vitiello et al. (2) found that the share represented by therapeutic procedures in their centre increased from 14% to 43% from 1987 to 1993, which could indicate a shift in the direction of therapeutic catheterizations over the years. However, some recent studies did not confirm the increase in therapeutic catheterizations (1,4). Diagnostic catheterizations were performed more often in boys, while in therapeutic catheterizations the 416 CARDIOVASCULAR SYSTEM Zdrav Vestn | September – October 2023 | Volume 92 | https://doi.org/10.6016/ZdravVestn.3390 sex ratio was equal. We did not find data on the sex ra- tio specifically for diagnostic or therapeutic catheteriza- tions, but most centres reported the sex ratio as equal for all catheterizations performed (2,3). The most therapeutic catheterizations were per- formed in children aged between 1 and 10 years. Our experience was similar to that of some other centres. Bergersen et al. (5) reported that 33% of diagnostic catheterizations were performed in children over 10 years and 30% in children between 1 and 10 years of age. 42% of therapeutic catheterizations were performed in children aged between 1 and 10 years. Ravndal et al. (3) stated that most were performed in children aged between 1 and 10 years (50.7% of all catheterizations). Furthermore, in our centre, catheterizations were most often performed in children who weighed between 10 and 40 kg, which coincides with the age at which most catheterizations were performed. Similarly, Ravndal et al. (3) described that 61.8% of all catheterizations were performed in children who weighed more than 10 kg. The reason for the highest number of catheterizations performed in the period from 1 to 10 years is most likely that in children with congenital heart defects during this period it is most often time for additional invasive di- agnostic procedures to monitor the condition or before planned surgery. It is also necessary to correct the pa- thology in time with therapeutic intervention, which can otherwise leave significant consequences for the heart. If possible, certain invasive procedures such as ASD clo- sure, vascular stenting, or pulmonary valve implantation are avoided in younger children because complications are more common (1-3,6-9), and the child may outgrow the implanted material, which might cause problems. The most common pathologies in diagnostic cathe- terization were isolated acyanotic and isolated cyanotic heart defects. Isolated defects are easier to identify with other non-invasive methods, while complex congenital heart defects or combinations of defects usually require additional invasive diagnostics. This higher frequency may be attributed to isolated defects being more com- mon than combined defects, both in general and in our population. In our population, diagnostic catheteriza- tion was most often performed in children diagnosed with hypoplastic left heart (HLH). In the literature, few centres reported which were the most common pathol- ogies in diagnostic catheterizations. Yilmazer et al. (1) observed VSD and tetralogy of Fallot (TOF) as the most common pathologies, while Bergersen et al. (5,6) report- ed a higher proportion of complex heart defects. The lat- ter, therefore, most likely depends on the incidence of certain congenital heart defects and the experience of the individual centre. In almost three-quarters of cases, children with an isolated acyanotic heart defect had therapeutic cath- eterization. The most common pathologies for which therapeutic catheterization was performed were found in only one research, where they were performed in 61% of complex and 34% of isolated defects (5). However, Mori et al. reported that 83.2% of all catheterizations were performed in complex pathologies (4). Differenc- es also somewhat depend on the definition of groups of pathologies; while we divided them into isolated and combined, some divided them further into isolated, complex and heart defects without a structural defect (4) or into even more groups (5). Almost half of the thera- peutic catheterizations performed in our centre (42.7%) involved closing defects with closure devices (closure of ASD/PFO and PDA). Balloon dilatation of PV and aortic valve (AV), and balloon atrioseptostomy were performed in most other cases (42%). At some centres, ASD and PDA closure procedures prevailed (3,5), while at others, balloon dilatation of valves, especially PV, pre- vailed (1). Among all catheterizations performed, 9 (4.7%) complications were noted. Based on the number of catheterizations performed, this gives a 95% confidence interval between 2.1% and 8.8%, which is at the lower end of the complication rates of some other centres per- forming pediatric cardiac catheterizations (1-7), which state that the rate is between 5.5% and 19%. In the case of minor complications, we note a frequency of 2.1% (95% CI 0.6%-5.3%), which is slightly less compared to foreign centres (between 4.1% and 16.3%) (1-7). For major complications, which we recorded in 2.6% (95% CI 0.9%-6.0%), we note a similar frequency as in for- eign centres (between 1.4% and 6.2%) (1-7). According to foreign data, death due to catheterizations occurred in 0.14% to 0.4% (1-7), while we did not record any deaths. In our centre, the most common complications re- corded were arrhythmias, bleeding, and embolization of the closure during ASD closure. The most common ma- jor and minor complications in foreign literature include arrhythmias and vascular thrombosis (1-5,7). Minor bleeding and damage to blood vessels or myocardium are also common complications (3,4). According to foreign data, the probability of emboli- sation of the closure device during ASD closure ranges from 0.05 % to 9.4% (average 4.46%) (1,10-13); in our case, we determined it as 5.9%. The lower probability of closure device displacement was in studies in which adults were also included or in studies with higher av- erage age. In our case, the embolisation occurred in 2 417 PROFESSIONAL ARTICLE Definition of the complications of cardiac catheterization in children in Slovenia patients aged 8 and 16 years. A higher percentage of em- bolisations was observed in studies where the sample of all ASD closures was smaller, and different closing devic- es than those in our centre were used (1,10). With a bet- ter selection of patients suitable for transcatheter closure of ASD, as well as with a better selection of the occluder size, the number of complications can be reduced, and as the number of performed catheterizations increases, so does operator experience. Severe bleeding as a complication was recorded in 0.5%, compared to other centres where it occurred, in 0.01% to 0.1% (average 0.04%) (5-7). A confidence in- terval between 0.01% and 2.9% indicates the frequency of the mentioned complication within the frequency limits of other centres. Moreover, bleeding occurred in a 2-month-old baby weighing 6.3 kg, where even a small amount of blood loss means a greater percentage of the total volume, hastening the need for transfusion. The frequency of minor bleeding in our centre was 0.5%, similar to other centres where it ranged between 0.2% and 0.6% (mean 0.46%) (2,4-7). Perforation of the heart wall and tamponade during balloon atrioseptostomy, a procedure with a high risk of the above complication, occurred in one case, repre- senting 0.5% of all cases. According to foreign research data, serious perforations of the heart walls occurred be- tween 0.04% and 0.35% of cases (2,4-7). The complica- tion happened in a few-hour-old baby weighing 3.4 kg, whose heart structures are smaller and catheterizations are technically more difficult. Balloon atrioseptostomy is a rather invasive, imperfectly controlled and high-risk catheter procedure. In one case, there was a perforation of the heart wall with minimal effusion and no further complications, which means a frequency of 0.5% in our centre. In other centres, minor cardiac perforations were described in 0.05% to 0.16% of cases (average 0.1%) (2,5- 7). According to the confidence interval (in both cases between 0.01% and 2.9%), the proportions are consis- tent with the frequency in other centres. Infection of catheterization site occurred in one pa- tient, representing 0.5% of all catheterizations, while other centres again reported infection rates between 0.02% and 0.1% (mean 0.06%) (5,6). With a confidence interval of between 0.01% and 2.9%, our experience is similar to that of other centres. Since all children re- ceived a preventive dose of antibiotics, the number of infection cases is low. The frequency of SVT occurrence during catheter- izations in other centres was between 0.2% and 0.6% (average 0.43%) (1,2,7), and the frequency of rhythm disturbances (in both cases of SVT) in our centre was 1.0%, with a confidence interval between 0.1% and 3.7%, corresponding to the experience of other centres. The incidence of complications in diagnostic cath- eterizations was 5.6%, and in therapeutic 4.4%, so the probability between both types is similar (p = 0.730). Our findings are consistent with the studies of some foreign centres (7), while others indicate an increased probability of complications during therapeutic proce- dures (1-3,5,6). Mehta et al. reported a higher incidence of major complications in therapeutic procedures, while the incidence of minor complications did not correlate with the type of catheterization (7). The incidence of complications in our centre also was not correlated with the type of therapeutic procedure. In foreign literature, the most complications were observed in balloon dila- tation of the aorta or AV (1,2). The difference may be explained by the fact that in our balloon dilatation cen- tre we only use low-pressure balloons (Tyshak balloon catheter, NuMed, Libanon), while the materials of other centres were not stated. We also note that the incidence of complications was not correlated with sex, since com- plications were found in 5.6% of all boys and 3.6% of all girls (p=0.530). Again, the findings differ depending on the centre; some noted a higher incidence in men (7), while others did not observe any differences between the sexes (1). We did not find statistically significant differ- ences according to age (p = 0.086) or weight (p = 0.088), but it can be noted that complications occurred some- what more often in younger and lighter children. They occurred in 13.0% of children under 1 month of age, 10.0% of those aged 1 to 11 months and in only 2.1% of children 1 year of age or older. The reason is likely that children of this age are lighter and smaller, their vascular and heart structures also being smaller, so procedures are technically more difficult to perform. Moreover, with more complex defects, catheterizations are required at a younger age, which might increase the likelihood of complications. We also observed that complications oc- curred in 13.6% of all children weighing less than 4 kg and 8.3% of children weighing between 4 kg and 9.9 kg (a total of 10.3% of children weighing < 10 kg), but only 2.4% for those weighing 10 kg or more. Despite this, we could not demonstrate any statistically significant differ- ences regarding the more frequent occurrence of com- plications in lighter children. Some other centres stated an increased probability of complications in children younger than 1 month or younger than 2 years and in children weighing less than 4 kg or less than 10 kg (1- 3,6-9). Complications were found in 3.5% of all children with an isolated and in 8.1% of children with a combined birth defect; we did not find any statistically significant 418 CARDIOVASCULAR SYSTEM Zdrav Vestn | September – October 2023 | Volume 92 | https://doi.org/10.6016/ZdravVestn.3390 References 1. Yilmazer MM, Üstyol A, Güven B, Öner T, Demirpençe S, Doksöz O, et al. Complications of cardiac catheterization in pediatric patients: a single center experience. Turk J Pediatr. 2012;54(5):478-85. PMID: 23427510 2. Vitiello R, McCrindle BW, Nykanen D, Freedom RM, Benson LN. Complications associated with pediatric cardiac catheterization. J Am Coll Cardiol. 1998;32(5):1433-40. DOI: 10.1016/S0735-1097(98)00396-9 PMID: 9809959 3. Ravndal ME, Christensen AH, Døhlen G, Holmstrøm H. Paediatric cardiac catheterisation in Norway: rates and types of complications innew terms. Cardiol Young. 2017;27(7):1329-35. DOI: 10.1017/S1047951117000208 PMID: 28270245 4. Mori Y, Takahashi K, Nakanishi T. Complications of cardiac catheterization in adults and children with congenital heartdisease in the current era. Heart Vessels. 2013;28(3):352-9. DOI: 10.1007/s00380-012-0241-x PMID: 22457096 difference in the frequency of complications accord- ing to the complexity of the pathology. Similarly, Mori et al. (4) determined the frequency of complications in 5.6% of patients with complex and 7.4% of children with an isolated congenital heart defect; no statistically significant differences were found between them, while Bergersen et al. (6) found the presence of complications in 18% of children with an isolated defect, 25% of chil- dren with a complex defect with one ventricle, and 26% of children with a complex defect with two ventricles. The cause of the differences between the centres might be different definitions of pathologies, as we separated them into isolated and combined, and the centres above into isolated and complex. Also, the reason for the dif- ferences may be the way complications were recorded, as both Mori et al. and Bergersen et al. (4,6) recorded data prospectively, while we recorded them retrospectively. The frequency of complications in our centre was also not correlated with the catheterization providers. 4.1 Limitations and possible improvements of the research The main limitation of our study is the small size of our patient sample. The comparison with some other centres may be less applicable due to possible differ- ent techniques or materials and different definitions of groups of initial pathologies and complications. There may also be differences in the inclusion and exclusion criteria for complications. Some centres also included transient arrhythmias as complications, which we did not, nor did we record the number of minor haemato- mas, which may have contributed to a lower incidence of minor complications. Differences in the proportion of some complications can also be attributed to retrospec- tive data collection. For a better comparison with foreign centres, it would be necessary to have a larger number of catheter- isations. Following the example of other research (5,6,9), the association of other factors with the occurrence of complications could be studied in the future. Factors that could be considered include risk assessment of the procedure, risk assessment according to the pathology, whether catheterization is urgent or elective, the dura- tion of catheterization and fluoroscopy, the amount of contrast used, and hemodynamic indicators of patient vulnerability. For a complete assessment of the occur- rence of complications, complications due to anesthe- sia should also be included. For easier comparison with foreign centres, the complications could be divided into several groups according to the severity level of the com- plication (none, minor, moderate, major, catastrophic) (5), which did not make sense in our case with a small number of catheterizations and complications. With prospectively designed research, more data could be col- lected in a targeted manner, which would also be record- ed more precisely. 5 Conclusion In our research, we presented all catheterizations performed at the Paediatric Clinic in Ljubljana between June 2018 and August 2021. We divided them into di- agnostic and therapeutic and identified all procedures performed during therapeutic catheterizations. The re- sults show that therapeutic catheterizations are predom- inant in our centre and that most catheterizations were performed in children aged between 1 and 10 years and those weighing between 1 and 40 kg. More catheteriza- tions were performed in boys. We found that the incidence of complications in our centre is comparable to other centres. We classified the complications into minor and major. Body weight, sex, age of the child, complexity of pathology or type of cath- eterisation were not statistically significantly correlated with the occurrence of complications during catheter- ization in our centre. Conflict of interest None declared. Acknowledgment We thank Ivan Verdenik, Ph. D. for advice on statis- tical calculations. 419 PROFESSIONAL ARTICLE Definition of the complications of cardiac catheterization in children in Slovenia 5. Bergersen L, Marshall A, Gauvreau K, Beekman R, Hirsch R, Foerster S, et al. Adverse event rates in congenital cardiac catheterization - a multi- center experience. Catheter Cardiovasc Interv. 2010;75(3):389-400. PMID: 19885913 6. Bergersen L, Gauvreau K, Jenkins KJ, Lock JE. Adverse event rates in congenital cardiac catheterization: a new understanding ofrisks. Congenit Heart Dis. 2008;3(2):90-105. DOI: 10.1111/j.1747-0803.2008.00176.x PMID: 18380758 7. Mehta R, Lee KJ, Chaturvedi R, Benson L. Complications of pediatric cardiac catheterization: a review in the current era. Catheter Cardiovasc Interv. 2008;72(2):278-85. DOI: 10.1002/ccd.21580 PMID: 18546231 8. Rhodes JF, Asnes JD, Blaufox AD, Sommer RJ. Impact of low body weight on frequency of pediatric cardiac catheterization complications. Am J Cardiol. 2000;86(11):1275-8. DOI: 10.1016/S0002-9149(00)01221-2 PMID: 11090810 9. Lin CH, Hegde S, Marshall AC, Porras D, Gauvreau K, Balzer DT, et al. Incidence and management of life-threatening adverse events during cardiac catheterizationfor congenital heart disease. Pediatr Cardiol. 2014;35(1):140-8. DOI: 10.1007/s00246-013-0752-y PMID: 23900744 10. Chessa M, Carminati M, Butera G, Bini RM, Drago M, Rosti L, et al. Early and late complications associated with transcatheter occlusion of secundum atrialseptal defect. J Am Coll Cardiol. 2002;39(6):1061-5. DOI: 10.1016/S0735-1097(02)01711-4 PMID: 11897451 11. Levi DS, Moore JW. Embolization and retrieval of the Amplatzer septal occluder. Catheter Cardiovasc Interv. 2004;61(4):543-7. DOI: 10.1002/ ccd.20011 PMID: 15065154 12. Turner DR, Owada CY, Sang CJ, Khan M, Lim DS. Closure of Secundum Atrial Septal Defects With the AMPLATZER Septal Occluder: A Prospective,Multicenter, Post-Approval Study. Circ Cardiovasc Interv. 2017;10(8):e004212. DOI: 10.1161/CIRCINTERVENTIONS.116.004212 PMID: 28801537 13. Abaci A, Unlu S, Alsancak Y, Kaya U, Sezenoz B. Short and long term complications of device closure of atrial septal defect and patentforamen ovale: meta-analysis of 28,142 patients from 203 studies. Catheter Cardiovasc Interv. 2013;82(7):1123-38. DOI: 10.1002/ccd.24875 PMID: 23412921