Pediatric Cardiac Surgery Outcomes Not Linked to Procedure Volume

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A real-world analysis in the United States suggests hospital volume may not be the lone predictor of outcomes in pediatric cardiac surgery.

A recent study suggested variations in procedure volume may not be the lone indicator of quality outcomes, including mortality rates, within hospitals performing pediatric cardiac surgery.1

The real-world analysis identified performance deficits among nearly 26,000 operations performed across 235 low-, mid-, and high-volume hospitals in the United States, suggesting case volume as a surrogate for quality may lead to unnecessary conclusions.

“This national, real-world, risk-adjusted volume-outcome analysis highlights that volume alone may not be the solitary arbiter to predict the quality of pediatric cardiac surgery outcomes in the United States,” wrote the investigative team, led by Christopher E. Mascio, MD, department of cardiovascular and thoracic surgery, West Virginia University.

Prior research has indicated a positive correlation between procedure volume and outcomes, leading many to believe that higher volume is associated with improved outcomes for pediatric cardiac surgery.2 However, program quality can be due to several factors, with evidence suggesting a complex relationship between annual case numbers and patient outcomes. These complexities may be due to system- or operator-dependent factors or patient-related variables.

For this analysis, Mascio and colleagues assessed the differences in mortality between low-, mid-, and high-volume hospitals in the US that perform pediatric cardiac surgery.1 To do so, the investigators team used the Kids’ Inpatient Database (KID), the largest publicly available all-payer pediatric inpatient care database in the US, which randomly samples 80% of complicated pediatric discharges (<21 years). The team analyzed data from the 2016 to 2019 KID to evaluate outcomes in hospitals performing at least 1 of 8 benchmark operations from the STS.

The analysis excluded hospitals performing only off-bypass coarctation and ventricular septal defect repair. Included hospitals were separated into terciles, according to the annual on-pump case volume: low-volume (≤103 cases/year), mid-volume (104 to 194 cases/year), and high-volume (>194 cases/year).

Multivariable logistic regression models were used to collect the adjusted in-hospital mortality rates for each included hospital. The study included 25,749 operations performed by 235 hospitals for analysis. These included 140 low-volume hospitals, 64 mid-volume hospitals, and 31 high-volume hospitals.

Overall, the risk-adjusted mortality rate for the sample was 1.9%. Across all 3 volume groups, investigators identified underperforming hospitals (mortality rate >1.9%) and overperforming hospitals (mortality <1.9%).

Among the low-volume hospital cohort, 53% (n = 74) of hospitals overperformed, while 47% (n = 66) of hospitals underperformed. For the mid-volume hospital cohort, 58% (n = 37) of hospitals overperformed, while 42% (n = 27%) underperformed. In the high-volume hospital cohort, 68% (n = 21) of hospitals overperformed, while 32% (n = 10) of hospitals underperformed.

Altogether, the adjusted overall mortality rates were 2.1% for the low-volume hospital cohort, 1.9% for the mid-volume hospital cohort, and 1.7% for the high-volume hospital cohort. The team found no statistically significant differences in mortality when comparing low- and mid-volume hospitals to high-volume hospitals for benchmark operations, including tetralogy of Fallot, arterial switch with ventricular septal defect (VSD), arterial switch without VSD, Glenn, Fontan, and repair of truncus arteriosus.

As Mascio and colleagues identified these real-world deficits in all volume categories, including high-volume programs, they noted case volume may represent an unfair quality metric for pediatric cardiac surgery outcomes.

“Using case volume as a surrogate for quality may unfairly asperse high-performing, low-volume programs,” they noted.


  1. Chauhan D, Mehaffey JH, Hayanga JWA, Udassi JP, Badhwar V, Mascio CE. Volume Alone Does Not Predict Quality Outcomes in Hospitals Performing Pediatric Cardiac Surgery. Presented the 2024 Society of Thoracic Surgeons Annual Meeting, January 27-29, 2024.
  2. Welke KF, Diggs BS, Karamlou T, et al. The relationship between hospital surgical case volumes and mortality rates in pediatric cardiac surgery: a national sample, 1988-2005. Ann Thorac Surg 2008; 86(3):889-96; discussion 889-96.