Age Shock Index is Superior to Shock Index and Modified Shock Index for Predicting Long-Term Prognosis in Acute Myocardial Infarction.

BACKGROUND

Shock index (SI) has been reported to help us predict adverse prognosis in patients with acute myocardial infarction (AMI) undergoing percutaneous coronary intervention (PCI). However, the prognostic value of age SI and modified shock index (MSI) in AMI undergoing PCI is unknown. Moreover, the prognostic performance of admission age SI is not compared with SI, MSI, and the Global Registry of Acute Coronary Events (GRACE) risk score.

METHODS

One thousand eight hundred sixty-four AMI patients undergoing PCI were analyzed in a retrospective cohort study. Clinical endpoint was all-cause mortality. The predictive performance of new models was assessed by C-statistic, Hosmer-Lemeshow test, Nagelkerke-R, Brier scores, integrated discrimination improvement (IDI), and net reclassification improvement (NRI).

RESULTS

Multivariate analysis showed that higher age SI and MSI were both associated with a higher rate of all-cause mortality [age SI: hazard ratios (HR) = 1.025, 95% CI = 1.010-1.040, P = 0.001; MSI: HR = 2.902, 95% CI = 1.180-7.137, P = 0.020]. The prognostic performance of admission age SI was similar to the GRACE systems for predicting all-cause mortality (C-statistic: z = 0.437, P = 0.662; IDI: -0.005, P = 0.474; NRI: -0.028, P = 0.257), but better than admission SI (C-statistic: z = 3.944, P < 0.001; IDI: 0.012, P = 0.016; NRI: 0.472, P < 0.001) and admission MSI (C-statistic: z = 3.214, P = 0.001; IDI: 0.011, P = 0.001; NRI: 0.561, P < 0.001).

CONCLUSIONS

Age SI alone can identify patients at high risk of death in AMI patients undergoing PCI. It is similar to GRACE but better than SI and MSI for predicting all-cause mortality. However, age SI is easier to calculate than GRACE.