Volume in Targeted Temperature Management Reflects System-Level Quality Rather Than Treatment Effect

The study by Kim et al.¹⁾ offers important insights into the relationship between institutional experience with targeted temperature management (TTM) and neurological outcomes in survivors of out-of-hospital cardiac arrest (OHCA). Using a large nationwide registry including 4,018 patients, the authors report that higher TTM case volume is associated with improved neurological outcomes, even after adjustment for multiple clinical variables. The interpretation of these results warrants careful consideration, particularly in the context of evolving evidence regarding TTM itself. Over the past decade, several large randomized trials have failed to demonstrate a clear survival advantage of hypothermia compared with controlled normothermia.²⁾,³⁾ Furthermore, there is limited evidence clearly demonstrating the efficacy of TTM, regardless of the duration or method of its application.⁴⁾,⁵⁾ If the therapeutic benefit of TTM itself is uncertain, it is difficult to attribute improved outcomes directly to greater institutional experience with this specific intervention. Rather, TTM volume may function as a surrogate marker of overall institutional capability, reflecting factors such as protocol adherence, multidisciplinary coordination, and resource availability. From this perspective, the observed association between higher TTM volume and better outcomes likely reflects broader system-level performance rather than the isolated effect of TTM expertise. An additional challenge in interpreting the present study lies in the differences in baseline characteristics across center volume groups. As reported, patients treated in high-volume centers had a higher rate of bystander cardiopulmonary resuscitation. This variable is a well-established determinant of neurological outcomes after OHCA.⁶⁾ Although multivariable adjustment was performed, residual confounding is difficult to exclude in observational registry-based analyses, particularly when key variables—such as arrest etiology, postarrest hemodynamics, and detailed intensive care unit management—are not captured. Furthermore, high-volume centers often receive patients via “inter-hospital transfer,” which inherently selects for patients stable enough to be moved, a major confounder in registry data. Taken together, these considerations suggest that volume itself is unlikely to be the causal factor; rather, it is more plausibly a proxy for the quality and organization of post–cardiac arrest care.

The dose–response relationship between TTM volume and outcomes also deserves attention. The spline analyses suggest a nonlinear association, with outcomes improving up to approximately 20–25 cases per year before reaching a plateau. While this pattern is statistically interesting, its clinical implications are less clear. The absence of a well-defined threshold and the sensitivity of the findings to model specification limit their applicability in guiding clinical decision-making or policy development. These findings suggest that the primary message of the study should not be interpreted as evidence that increasing TTM volume per se will improve outcomes. Instead, the results highlight the importance of institutional readiness and the delivery of comprehensive post–cardiac arrest care. High-volume centers are likely to have established protocols, experienced multidisciplinary teams, and the infrastructure necessary to provide coordinated care, including 24/7 availability of an operational cardiac catheterization laboratory, capability for extracorporeal membrane oxygenation-assisted cardiopulmonary resuscitation, timely coronary evaluation, optimized hemodynamic management, and standardized neuroprognostication. From a clinical perspective, the focus should therefore shift from individual interventions to systems of care.

Future research should aim to disentangle the relative contributions of individual components within post–cardiac arrest care. Studies incorporating granular data on postarrest management, including hemodynamics, neuroprognostication strategies, and intensive care practices, will be essential to identify the mechanisms underlying improved outcomes. Furthermore, prospective studies or pragmatic trials focusing on system-level interventions may provide more actionable insights than analyses centered solely on procedural volume.

In conclusion, while the study by Kim et al.¹⁾ contributes valuable data on the association between TTM case volume and neurological outcomes, its clinical implications should be interpreted with caution. In an era where the benefit of TTM itself remains debated, the incremental value of volume-based analyses is likely limited. The findings are best understood as reflecting the importance of high-quality, system-based care rather than the effect of TTM experience alone. Ultimately, improving outcomes after cardiac arrest will depend not on how often TTM is performed, but on how well comprehensive post–cardiac arrest care is delivered.