Prognostic utility of shock index and modified shock index on long-term mortality in acute decompensated heart failure; Persian Registry of cardioVascular diseasE/Heart Failure (PROVE/HF) study

Background Shock index (SI) and modified SI (MSI) are used for prognosis in patients with cardiovascular diseases (CVDs), especially myocardial infarction. However, the utility of these indices in heart failure(HF) is less frequently investigated. We aimed to evaluate the long-term prognostic capability of SI and MSI among Iranian HF patients. Methods This retrospective cohort study was implemented in the context of the Persian Registry Of cardioVascular diseasE/HF (PROVE/HF). A total of 3896 acute decompensated HF (ADHF) patients were enrolled from March 2016 to March 2020. SI and MSI were assessed at admission. Receiver operating characteristic (ROC) and Kaplan-Meier curves were used to define optimum SI and MSI cut-off points and depict mortality during follow-up, respectively. The association of CVD death according to different SI and MSI cut-off points and quartiles was assessed through univariate and multivariate regression hazard models. Results Mean age of participants was 70.22 +/- 12.65 years (males: 62.1%). We found 0.66 (sensitivity:62%, specificity: 51%) and 0.87 (sensitivity: 61%, specificity: 51%) as optimised cut-off points for SI and MSI, respectively. Mean follow-up was 10.26 +/- 7.5 months and 1110 (28.5%) deaths occurred during this time. Multivariate adjusted models revealed patients had SI >= 0.66 or within the third and fourth quartiles had higher likelihood of mortality compared to reference group (hazard ratio(HR): 1.58, 95%CI: 1.39-1.80, p < 0.001, HR: 1.38,95%CI:1.14-1.66, p = 0.001 and HR:2.00,95%CI:1.68-2.38, p < 0.001, respectively). MSI outcomes were similar (MSI >= 0.87: HR: 1.52,95%CI: 1.34-1.72, p < 0.001, third quartile (0.89 <= MSI < 1.00):HR:1.23,95%CI:1.009-1.50, p = 0.041, fourth quartile (MSI >= 1.00): HR: 1.80,95%CI: 1.53-2.13, p < 0.001). Kaplan-Meier curves showed patients with higher SI and MSI cut-off values and quartiles had lower survival rates. Conclusion Higher SI and MSI values were associated with increased mortality risk, and these two bedside indices could be appropriately considered for long-term prognosis in ADHF patients.