Clinical characteristics and in‐hospital mortality among insulin pump users with acute coronary syndrome in the predominantly open‐loop era: A UK ‐wide MINAP registry analysis

BACKGROUND: We compared characteristics of adults with insulin-treated diabetes using continuous subcutaneous insulin infusion (CSII) versus multiple daily insulin injections (MDI) during admission with acute coronary syndrome (ACS) and identified factors associated with in-hospital mortality among CSII users. METHODS: This retrospective cohort study used the Myocardial Ischaemia National Audit Project, a registry of ACS admissions in England and Wales. Adults aged ≥18 years with confirmed ACS and insulin-treated diabetes were classified as CSII or MDI users. Baseline characteristics were compared. Gradient boosting machine (GBM) modelling and multivariable logistic regression evaluated mortality predictors among CSII users. RESULTS: The cohort included 3321 CSII users and 30,593 MDI users. In-hospital mortality was higher among CSII users (11.4% vs. 5.1%; p < 0.001). CSII users had higher rates of cardiogenic shock (4.8% vs. 1.3%), pulmonary oedema (12.1% vs. 8.3%), poor left ventricular systolic function (23.5% vs. 19.7%), and STEMI (32.2% vs. 20.5%). Cardiogenic shock was the strongest predictor of mortality (adjusted OR 10.46, 95% CI 6.95-15.81), followed by poor left ventricular function (OR 4.15, 95% CI 2.69-6.53), basal crepitations (OR 1.94, 95% CI 1.40-2.67) and pulmonary oedema (OR 1.56, 95% CI 1.05-2.28). Higher systolic blood pressure was associated with lower mortality (OR 0.86 per 10 mmHg, 95% CI 0.82-0.90). The GBM model achieved an AUC of 0.85 and a Brier score of 0.088. CONCLUSIONS: CSII users admitted with ACS represented a more complex group with haemodynamic compromise and higher unadjusted mortality. Findings predominantly reflect the open-loop CSII era and may not generalise to contemporary hybrid closed-loop systems.