Low-Volume, High-Volume, Weaknesses, and Strengths

My first clinical post as a congenital heart surgeon was in a low-volume program and since then I spent 19 years in high-volume programs. With a personal perspective in both environments, I have some observations to consider as the conflict between low- and high-volume programs draws increasing attention.

(NB: “Low-volume” and “High-volume” are arbitrarily defined as 75-200 and >200 annual STS index cases respectively as previously described by Backer et al (J Thor Cardiovasc Surg. 2023 Dec;166(6):1782-1820).

High-volume programs have access to an incredible spectrum of expertise with highly dedicated clinicians. Experts abound for every rare and complex lesion and even ‘rare’ lesions are common in this type of enriched environment. Nevertheless, the sheer size of high-volume programs at the higher range of volume creates a significant challenge in communication and maintaining shared consciousness across the organization. Trust can also become an issue when the roster of clinicians is so large that clinicians feel that they are ‘working with strangers’ and, furthermore, families can be dissatisfied when they have trouble identifying who is actually in charge on a of their child’s care on a day-to-day basis as multiple clinicians rotate through their circle of care.

Low-volume programs face a different set of volume-related challenges. Although low-volume programs may have the majority of required areas of expertise covered, ‘single points of failure’ often exist in areas whenever a key clinician is unavailable due to vacation, illness, or exhaustion. Lack of repetition can also lead to a higher frequency of errors in common cases and this concern may be more pronounced when treating rare lesions. The judgement required to initiate timely transfer of patients to high-volume programs with appropriate expertise is an ever-present decision-making challenge for the clinical team. Nevertheless, the evidence suggests that some low-volume programs can achieve superb risk-adjusted outcomes. Excellent outcomes may be related to the fact that the team can easily achieve ‘one-ness’ through constant close communication and personal proximity that leads to highly personalized, intense, and focused care. Parents of our patients clearly enjoy a sense of partnership with a closely-knit clinical team that imparts additional perceived value to the delivery of care.

Most recently I have spent considerable time in a consulting role at Driscoll Children’s Hospital - which is a rapidly growing low-volume program (~150 STS index cases/year) that nevertheless achieves remarkable level of performance in the most recently updated version of the Society of Thoracic Surgeons (STS) public reporting database (encompassing index cases from July 2019 - June 2023; https://publicreporting.sts.org/chsd ). The Driscoll program under the leadership of Drs Stephen Langley and Dan McKenna have an overall observed to expected mortality (O/E) ratio of 0.61 with upper/lower confidence limits of 0.31/0.96 respectively - suggesting that the favorable O/E ratio is statistically significant. In the past this level of performance was considered worthy of a ‘3-star’ designation. In the current STS reporting, only 12 out of ~97 publicly reporting congenital heart programs have achieved this level of risk-adjusted performance with upper confidence limits < 1.0. This low-volume program is delivering excellent care.

Not all low-volume programs achieve excellence (and, of course, neither do all high-volume programs). It is not clear which factors contribute to the wide range of performance in low-volume programs. Undoubtedly, manageably sized teams working closely together as a unified and dedicated, capable, and focused unit contributes to excellent performance. Hospital administrative support may also be a critical factor. Indeed, the willingness of the Driscoll hospital leadership to work closely with the clinical team underscores a clear institution-wide commitment to strive for excellence. In fact, a manifestation of the hospital leadership’s commitment is demonstrated in their willingness to fund my engagement at Driscoll – where my role is to contribute wherever I can to improve team performance as the clinical volume grows. Personally, I am learning a great deal by watching the Driscoll team in action - and it is a pleasure to enjoy the sense of ‘one-ness’ that is difficult to achieve in a high-volume program but intuitively seems to strongly impacts outcomes.

Those of us who have dedicated our careers to treating patients with congenital heart disease need to better understand how the top performing programs in low-volume settings can achieve excellent outcomes. It is worth mentioning that the Congenital Heart Surgeons Society will be studying programs to identify the attributes associated with superior performance. Our objective will be to identify the important attributes and share the information among all programs. (More details to follow on this exciting study which was generously funded by the Brett Boyer Foundation!)

Low- and high-volume programs face important (and differing) challenges to optimize performance. Mastery of these volume-related challenges will have strong effect on outcomes. Whatever the size of your program: Identify and manage your weaknesses, leverage your strengths, and always do what is best for the patient.