Discussion

To our knowledge, this study is the first to provide data demonstrating current variability in cardiac ICU training experiences during paediatric critical care medicine. Combining website and survey-based data, we demonstrated that United States paediatric critical care medicine fellowships provide vastly different cardiac ICU training experiences. Some of the most notable variations include time on cardiac ICU service being as short as 4 weeks in some programmes. There are training programmes with no attending physicians with formal cardiac critical care training, though it should be noted that these programmes may include cardiac ICU attendings who were practising before advanced fellowship training pathways were widely available. Only 29% (12/41) of programmes have supplemental cardiac rotations. Finally, some fellows graduate having taken absolutely no call covering critically ill cardiac patients. Ensuring paediatric critical care medicine fellows graduate with competency in caring for cardiac ICU patients is particularly difficult given: 1) differing cardiac ICU structures and learner traffic, 2) varying CHD surgical case volume and acuity exposure, and 3) inconsistencies in cardiac ICU didactic and simulation educational experiences.

Prior literature reporting the landscape of cardiac ICU care models – designated cardiac ICU versus mixed paediatric ICUs – is sparse, with a recent study reporting 67% designated cardiac ICUs. ^{Reference Horak and Bai Shasha2,Reference Horak, Alexander, Amirnovin, Klein, Bronicki and Markovitz5,Reference Morrison, Helfaer and Nadkarni13} Our study demonstrates that 76% (31/41) of responding programmes now have a dedicated cardiac ICU. The learner experience is different in these dedicated cardiac ICUs by nature of unit organisation. ^{Reference Tabbutt, Ghanayem and Almodovar3} For example, dedicated cardiac ICUs may be more likely to utilise temporary circulatory support devices besides extracorporeal membrane oxygenation and durable cardiac support devices (e.g., Berlin Heart EXCOR, heart ventricular assist devices), which are not commonly encountered in mixed units. ^{Reference Tabbutt, Ghanayem and Almodovar3,Reference Horak, Alexander, Amirnovin, Klein, Bronicki and Markovitz5} Separate cardiac ICUs also tend to have increased access to more cardiac-specific subspecialists (e.g., electrophysiology, heart failure, cardiac anaesthesia consultants). ^{Reference Tabbutt, Ghanayem and Almodovar3,Reference Horak, Alexander, Amirnovin, Klein, Bronicki and Markovitz5,Reference Owens, Owens, Rajput, Charpie, Kidwell and Mullan15} More commonly in separate cardiac ICUs vs. mixed units, at least one attending has additional cardiac training. ^{Reference Tabbutt, Ghanayem and Almodovar3,Reference Horak, Alexander, Amirnovin, Klein, Bronicki and Markovitz5,Reference Baden, Zimmerman, Brilli, Wong, Wetzel and Burns14} A recent survey of paediatric critical care medicine directors indicated that approximately 33% of cardiac ICU staff physicians are double-boarded in paediatric critical care medicine and cardiology, 12.5% underwent paediatric critical care medicine fellowship and a 1-year cardiac ICU fellowship, 30% underwent cardiology fellowship in addition to a 1-year cardiac ICU fellowship, and 21% underwent paediatric critical care medicine fellowship with no additional training (including those who were practising long before the addition of the 1-year cardiac ICU and dual fellowship training pathways became readily available). ^{Reference Werho, DeWitt, Owens, McBride, Schaik and Roth16} The 1-year paediatric cardiac critical care fellowship even has standardised training guidelines now; however, dual boarding in cardiology and paediatric critical care medicine remains the gold standard. ^{Reference Tabbutt, Krawczeski and McBride1} While paediatric residents commonly staff mixed units, paediatric critical care medicine fellows are predominant learners in cardiac ICUs, perhaps allowing for more fellow practice autonomy. ^{Reference Tabbutt, Ghanayem and Almodovar3,Reference Horak, Alexander, Amirnovin, Klein, Bronicki and Markovitz5,Reference Owens, Owens, Rajput, Charpie, Kidwell and Mullan15} Unit structural differences create different learning environments for paediatric critical care medicine fellows and likely affect exposure to various CHDs, acuity, surgical procedures, and circulatory support devices. ^{Reference Tabbutt, Ghanayem and Almodovar3}

In general, hospitals with dedicated cardiac ICUs have higher surgical volumes and younger patients with higher-risk defects, increasing fellow exposure to higher acuity patients. ^{Reference Tabbutt, Ghanayem and Almodovar3,Reference Hilvers and Thammasitboon17,Reference Burstein, Jacobs, Li, Sheng, O’Brien and Rossi18} We begin to describe the variability in surgical volume exposure and acuity, as depicted in Figure 1. While data in this figure are based on calculated assumptions, they depict an obvious trend: programmes with more CHD surgical cases do not necessarily provide more learning opportunities per fellow. Often, higher volume programmes have more paediatric critical care medicine fellows, supporting the assumption that these cases are shared between more learners. This notion is further complicated by the presence of other learners in the cardiac ICU at any one time. The impact of being the primary fellow responsible for individual patient versus sharing cases for learning opportunities is not well understood. While some literature suggests a positive association between quantity of clinical encounters and medical knowledge acquisition, an ideal patient caseload for optimal fellow learning is unclear. ^{Reference Burstein, Jacobs, Li, Sheng, O’Brien and Rossi18,Reference McCoy, Stenerson, Halvorsen, Homme and McDonald19}

There is no standard Accreditation Council of Graduate Medical Education-recommended cardiac curriculum for paediatric critical care medicine fellowships and variable cardiac ICU training pathways post- paediatric critical care medicine fellowship. ^{Reference Horak and Bai Shasha2,Reference Tabbutt, Ghanayem and Almodovar3,Reference Anand, Kwiatkowski, Ghanayem, Axelrod, DiNardo and Klugman20} However, according to the Pediatric Cardiac Intensive Care Society, either the 1-year paediatric cardiac critical care fellowship or dual boarding in Cardiology and paediatric critical care medicine are now the national standard for training for current fellows undergoing training and expecting to care for cardiac critical care patients. ²¹ Cardiac ICU experiences during paediatric critical care medicine fellowship also vary in terms of time spent on service (for those with separate units) and institution-specific cardiac didactics. Programmes with dedicated cardiac ICU blocks required more total on-service ICU time for their fellows in exchange for less non-ICU experiences, and the effects of this exchange on fellows are unknown. ^{Reference Morrison, Helfaer and Nadkarni13} Some institutions also require their paediatric critical care medicine fellows to spend time on cardiothoracic surgery, cardiology, and/or echocardiography/catheterisation lab rotations, while others do not. While these experiences may expand fellow exposure to cardiology, the potential benefit to fellow education and impact on cardiac ICU preparedness is yet to be determined. Further, while the majority of programmes reported a dedicated cardiac didactic curriculum, this was not universal, highlighting a potential additional disparity among graduating paediatric critical care medicine fellows. Lastly, prior studies demonstrated that simulation advances learner comfort, knowledge, and skills surrounding management of complex cardiac patients. ^{Reference Bergman and Howell22–Reference Cashen and Petersen24} As depicted by our study, critical cardiac simulation experiences are not standardised across United States paediatric critical care medicine fellowships.

Our study has some limitations. Our survey response rate of 58% (41/71) clearly did not encompass all paediatric critical care medicine fellowships. However, respondents came from programmes across the country and were various in terms of institution size and patient load. This study did not assess programme-to-programme variance in primary responsibilities of the paediatric critical care medicine fellow at bedside, number of additional fellows and other learners concurrently rotating through the cardiac ICU, duration of clinical service rotations, or paediatric critical care medicine fellow mandatory research or vacation time. These limitations should be considered when reviewing our results regarding patient volume per paediatric critical care medicine fellow. While we cannot assume all websites were recently updated, programme websites’ fellow listings appeared to be up to date, particularly with the recent national virtual recruitment season due to the pandemic, leading us to believe most information was reasonably recent.

Our findings are congruent with prior studies. ^{Reference Su and Munoz8} Though formal cardiac training pathways now exist, not all paediatric critical care medicine will not pursue them, as even in dedicated CICUs, many attendings staffing these units did not have advanced training. As the trend toward dedicated CICUs continues and the field of paediatric cardiac critical care becomes more standardised, ^{Reference Horak and Bai Shasha2} so should the education. Discussions among field experts regarding minimum amount of time on service, optimal patient to fellow ratios, and the need for supplemental educational experiences during paediatric critical care medicine fellowship should be pursued and more specific recommendations from the Accreditation Council of Graduate Medical Education are needed.

Overall, this study illustrates the continuing trend toward dedicated cardiac ICUs and the variability that currently exists in United States paediatric critical care medicine fellowships. This is important because paediatric critical care medicine fellows are graduating with varying levels of exposure to patients with critical cardiac disease and, consequently, different levels of comfort caring for these patients.