Inotropes and mortality in patients with cardiogenic shock: an instrumental variable analysis from the SWEDEHEART registry

Abstract Background The use of inotropic agents in treating cardiogenic shock (CS) remains controversial. This study investigates the effect of inotropes on 30-day mortality in CS patients using data from the SWEDEHEART registry (The Swedish Web-system for Enhancement and Development of Evidence-based care in Heart disease Evaluated According to Recommended Therapies). Methods Data were sourced from the national SWEDEHEART registry for all CS patients in Sweden from 2000 to 2022. The primary endpoint was 30-day all-cause mortality. We employed multilevel Cox proportional-hazards regression with instrumental variable and inverse probability weighting propensity score to adjust for confounders. The treatment-preference instrument was the quintile of preference for inotrope use at the treating hospital. Results A total of 16 214 patients (60.5% men, 39.5% women) were included; 23.5% had diabetes, 10.2% had a previous myocardial infarction (MI), and 13.8% had previous heart failure (HF). The median age was 70 years (IQR; 19), with 66.4% over 70. Acute coronary syndrome (ACS) caused CS in 82.9%. Inotropes were administered to 43.8% of patients, while 56.2% did not receive them. There were 7 875 (48.1%) deaths. Patients treated with inotropes were, on average, two years younger and more likely to have ACS, while those not treated had more previous MI and were less likely to undergo PCI. The number of CS cases decreased by 12% per year (Ptrend < 0.001), and inotrope use increased by 5% per year (Ptrend < 0.001). Unadjusted mortality in CS rose by 2% per calendar year (Ptrend < 0.001). Inotropes were associated with higher mortality (adjusted HR 1.72; 95% CI 1.26–2.35; P = 0.001), with significant interactions between inotrope treatment, age, and diagnosis (Pinteraction < 0.001 and Pinteraction = 0.018). Conclusions In this observational study, inotropes were linked to higher mortality in CS patients, particularly those younger than 70. While CS cases decreased, inotrope use and mortality increased in Sweden.