Background:
Shock index (SI), defined as heart rate divided by systolic blood pressure, is a useful simple predictor of long-term mortality after acute myocardial infarction.
Purpose: To assess the utilization of the SI updated version that includes renal function (Shock Index-Creatinine Clearance (SI-C)) to predict long-term mortality after ACS.
Methods: This preliminary analysis included 589 patients with ACS admitted to three Italian hospitals and discharged alive. Baseline clinical and laboratory data were collected within the first 7 days of hospitalization and SI-C was calculated as (SI×100)-estimated CCr. Patients were prospectively followed for 24 years or until death.
Results: Virtually all patients completed the follow-up, representing 7066 person-years. Patients ‘ mean age was 66±12 years, 70% were males and 482(82%) had died during follow-up. Compared to those who survived, deceased patients were significantly different in many clinical features. They also showed significantly higher SI-C values ( -11± 25 vs. -36±23, 0.0001). The predictive value of SI-C for 24-year mortality was very good (area under the curve= 0.783, 95% CI: 0.738-0.827, 0.001). The cumulative risk was significantly higher in the upper SI-C tertile (log-rank = 162.1, p < 0.001). Unadjusted Cox regression survival analysis showed that the SI-C score was significantly associated with long-term global mortality (HR: 2.1, 95%CI 1.8-2.3, 0.0001). A fully adjusted model revealed the same results. Conclusion: Baseline SI-C seems to be an effective independent predictor of long-term global mortality after ACS. It may have potential as a novel and simple early risk stratification tool for ACS patients including long-term outcomes.
