Therapeutic catheterization in congenital heart disease: reflections on the value of risk scores

This editorial refers to ‘Prediction of adverse events after catheter-based procedures in adolescents and adults with congenital heart disease in the IMPACT registry’†, by A.C. Stefanescu Schmidt et al., on page 2070. Cardiac catheterization has become an essential part of the armamentarium available for the diagnosis and treatment of patients with congenital heart disease (CHD), and its role is expanding further. The number of catheter-based procedures carried out in CHD centres has increased over the last two decade, and new procedures—often complementing surgery—such as, for example, percutaneous pulmonary or tricuspid valve implantation, have been introduced into clinical practice.1 , 2 The increase in procedure numbers is universal for all age groups, but more pronounced in adults than in children (Figure 1). This reflects the ever-increasing numbers of patients surviving with CHD as a result of the progress made in the management of children with major congenital cardiac malformations.3 The number of adult patients with CHD is therefore growing continuously and now exceeds the number of children.4 Surgery and catheter interventions in congenital heart disease performed in the UK over the period from 2000/2001 to 2014/2015. Source: National Institute for Cardiovascular Outcomes Research; https://nicor4.nicor.org.uk/CHD/an_paeds.nsf/WSummaryYears?openview&RestrictToCategory=2015&start=1&count=500. It is not only true that congenital cardiac catheterization procedures have increased in number but it is also evident that their role has evolved. Cardiac catheterization has developed from a diagnostic towards an increasingly complex interventional tool as non-invasive diagnostic modalities have become available. It is therefore timely to focus on the risks associated with cardiac catheterization in the ageing population of CHD patients. Stefanescu Schmidt and co-workers should be commended on their effort at establishing a risk score for major adverse events in adolescent and adult patients in the USA that is published in this issue of the journal.5 Such scores could be helpful tools to individualize the patient’s risk and to guide the consent process. The risk score presented results from the analysis of data from 27 293 diagnostic and interventional procedures performed at 87 hospitals on patients aged 10 years or above, and collected in the Improving Pediatric and Adult Congenital Treatment (IMPACT) registry of the American College of Cardiology. A major adverse event was very broadly defined as a composite of death, urgent surgery or procedure due to a catheterization complication, transfusion, embolic stroke, tamponade, the need for extracorporeal membrane oxygenation or ventricular assist device placement, device embolization, malposition, or thrombosis requiring surgical intervention. An event rate of 2.5% was reported. Independent predictors of an adverse event were older age, pre-procedural anticoagulation use, renal disease, lower haemoglobin, lower oxygen saturation, non-elective procedure, higher risk procedure, and having had no prior cardiac catheterization procedures. Although this is a helpful addition to the existing literature on risk prediction for congenital cardiac catheterization, the presented data have some weaknesses limiting its use in everyday practice, particularly in relation to specialist adult CHD services. A mixed population including 63% children aged 10–18 years and only 37% adults is analysed, under-representing the increasing and ageing population of adult CHD patients and therefore limiting the use of the proposed risk score for centres specializing exclusively in adult CHD. The fact that nationwide registry data collected from 87 centres are analysed also means that data from centres with different workload, expertise, and focus have been mixed. It is likely that mainly paediatric centres were the majority of contributers to the IMPACT registry. Unfortunately, centre-specific variables that may well have a major impact on procedural risks and outcomes were not analysed. This potentially reduces the validity of the risk score for centres that focus on either paediatric or adult congenital catheterization alone. In adult CHD interventional practice, we have seen the role of cardiac catheterization expanding. A look at the case mix of procedures performed at London’s Royal Brompton Hospital shows that with the introduction of new procedures, catheter-based work in adult CHD has become more diverse during the last decade. Furthermore, procedures of low complexity such as patent foramen ovale (PFO) closure are less frequently performed (from 2005 to 2016 the proportion of PFO closures has reduced from 44% to 18% of the interventional cases), whereas newer procedures of high complexity such as valve implants nowadays comprise a significant proportion of the workload; for example, 9% of the work performed in 2016 was pulmonary or tricuspid valve implants. Despite this, major adverse event rates as defined by Stefanescu Schmidt have been maintained at a low level of 1.3% in 2016. This illustrates that therapeutic cardiac catheterization performed on an adult in a specialist centre for adult CHD results in major complication rates comparable with or even less than those reported by Stefanescu-Schmidt et al. for a much younger population. We would therefore speculate that there is rarely a place for the paediatric cardiologist who alone performs occasional interventional procedures on adults just as there is rarely the case for the adult cardiologist who performs procedures on infants and children. Each individual operator should be appropriately trained. It is our opinion that the ideal model of care for adults and children with CHD is a vertical and multidisciplinary environment with close collaboration between the teams of cardiologist and surgeons specializing in paediatric and adult congenital cardiology. Conflict of interest: none declared.