Relationship Between the Volume of Cases and In-hospital Mortality in Patients with Cardiogenic Shock Receiving Short-term Mechanical Circulatory Support

Background: We examined the relationship between annual case volume at each hospital and outcome in cardiogenic shock (CS) patients receiving mechanical circulatory support (MCS) devices.

Methods: This cross-sectional study used the Japanese nationwide database to identify patients receiving short-term MCS for CS between April 2012 and March 2020. Of 65,837 patients, 3 subcohorts were created; the intra-aortic balloon pump (IABP) alone (n = 48,643), the extracorporeal membrane oxygenation (ECMO) (n = 16,871), and the Impella cohorts (n = 696).

Results: The median annual case volume was 13.5 (7.4-22.1) in the IABP alone cohort, 6.4 (3.4-11.0) in the ECMO cohort, and 7.5 (4.0-10.7) in the Impella cohort. The highest quintile for the volume of cases in the IABP alone and ECMO had the lowest in-hospital mortality (IABP alone, 25.1% in quintile 1 vs 15.2% in quintile 5; ECMO, 73.7% in quintile 1 in 67.4% in quintile 5). Adjusted ORs for in-hospital mortality decreased as case volume increased (IABP alone, 0.63 [0.58-0.68] in quintile 5; ECMO, 0.73 [0.65-0.82] in quintile 5, with the lowest quintile as reference) but did not decrease significantly in the Impella (0.90 [0.58-1.39] in tertile 3, with the lowest tertile as reference). In the continuous models with the case volume as a continuous variable, adjusted ORs for in-hospital mortality decreased to 28 IABP cases/year and 12 ECMO cases/year. They did not decrease or became almost flat above that.

Conclusions: Higher volumes of IABP and ECMO are associated with a lower mortality. There is an upper limit to the decline. Centralizing patients with refractory CS in a particular hospital might improve patient outcomes in each region.