Shock index and modified shock index at discharge as predictors of long-term mortality after myocardial infarction: results from the Augsburg Myocardial Infarction Registry

Clinical Research in Cardiology https://doi.org/10.1007/s00392-026-02929-z ORIGINAL PAPER Shock index and modified shock index at discharge as predictors of long‑term mortality after myocardial infarction: results from the Augsburg Myocardial Infarction Registry Constantin Rödl1 · Christa Meisinger1 · Bernhard Kuch3 · Philip Raake2 · Jakob Linseisen1 · Timo Schmitz1 Received: 4 February 2026 / Accepted: 17 April 2026 © The Author(s) 2026 Abstract Background Shock index (SI) and modified shock index (mSI), measured at hospital admission, have been shown to be predictive for mid- and long-term outcomes after acute myocardial infarction (AMI). Whether these associations also hold when indices are measured at discharge is unclear, so this study’s aim was to analyze the association between SI and mSI at discharge and long-term mortality after AMI. Material and methods This analysis included 11,676 AMI cases registered by the population-based Myocardial Infarction Registry Augsburg. The follow-up time was restricted to a maximum of 5 years. Patients were categorized into low and high SI or mSI groups through separation at 75th percentiles for STEMI and NSTEMI, respectively. Analysis of survival included Kaplan–Meier curves with log-rank tests and multivariable-adjusted Cox-regression models. Results Cut-off values were 0.6667 (STEMI) and 0.6545 (NSTEMI) for SI and 0.9231 (STEMI) and 0.9120 (NSTEMI) for mSI. Kaplan–Meier analysis showed significantly higher mortality for high SI and mSI groups in STEMI and NSTEMI patients. In STEMI cases, multivariable-adjusted Cox-regression analyses revealed significantly higher mortality for the high SI group (hazard ratio (HR): 1.25 (1.02–1.53), p value: 0.030), while mSI was non-significantly associated with longterm mortality (HR: 1.21 (0.99–1.48), p value: 0.060). Neither SI nor mSI was independently associated with mortality in NSTEMI. Conclusion SI and mSI at discharge represent valuable tools for long-term post-infarction risk stratification especially in STEMI cases and can support decision-making regarding individualized ambulatory care. * Timo Schmitz 1 Epidemiology, Faculty of Medicine, University of Augsburg, Stenglinstraße 2, 86156 Augsburg, Germany 2 Department of Cardiology, Respiratory Medicine and Intensive Care, University Hospital Augsburg, Augsburg, Germany 3 Stiftungskrankenhaus Nördlingen Department of Internal Medicine/Cardiology/Intensive Care, Donau‑Ries‑Kliniken, Nördlingen, Germany Vol.:(0123456789) Clinical Research in Cardiology Graphical Abstract Keywords Myocardial infarction · Shock index · Modified shock index · Long-term mortality Introduction Due to the persistent burden of acute myocardial infarction (AMI) for public health [1], practicable and clinically suitable tools for individual risk stratification remain relevant beyond the index hospitalization due to AMI. Heart rate and blood pressure are clinical parameters that reflect cardiovascular status and are part of basic clinical monitoring. These parameters can be combined in the shock index (SI) and modified shock index (mSI). The SI was developed already in 1967 by Allgöwer and Burri as heart rate divided by systolic blood pressure [2]. Liu et al. (2012) introduced the mSI, defined as the ratio of heart rate and mean arterial blood pressure (MAP), and thereby also considering diastolic blood pressure [3]. Originally developed as indices for emergency situations, both markers have been shown to be strong predictors for short-term mortality after AMI [2–4]. Reinstadler and coworkers demonstrated that SI is a predictor of major adverse cardiac events up to 1 year post-infarction [5]. Recently, our working group reported their predictive value for long-term mortality (up to several years) [6]. While recent studies analyzed SI and mSI separately for STEMI (ST-elevation myocardial infarction) and NSTEMI (non-ST-elevation myocardial infarction) [6], earlier research mostly did not differentiate between infarction types [7]. Furthermore, the primary research focus has been on SI and mSI at hospital admission, with limited evidence regarding their prognostic value at discharge. Since discharge reflects the patient’s status of cardiovascular recovery following therapy and marks the final point of in-hospital surveillance, evaluating the prognostic value of SI and mSI at this time is particularly relevant for planning ambulatory aftercare. Therefore, the aim of this study was to analyze whether SI and mSI at discharge can be used to stratify individual risks regarding long-term mortality after AMI, and whether their predictive strength differs between STEMI and NSTEMI, using data from a population-based registry with longterm follow-up. Clinical Research in Cardiology Materials and methods Patients The research for this analysis was based on the Myocardial Infarction Registry Augsburg, which was established in 1984 as part of the MONICA project. The registry captures AMI cases in the city of Augsburg and the two surrounding counties (overall population of about 705,000). Inclusion required residency in the study region and age 25–74 (until 2008) or 25–84 years (from 2009 to 2017). Standardized bedside interviews by trained study nurses and systematic elaboration of the medical chart yielded detailed information on demographics, comorbidities, risk factors, diagnostics, and treatment. Information on vital status and dates of death was ascertained through data from residents’ registration and local health authorities. For this analysis, the latest comprehensive mortality update was performed in 2019. Further details on methodology and data collection can be found in previous publications [8, 9]. The registry protocol was approved by the Ethics Committee of the Bavarian Medical Association (BLÄK, ethics committee number: 12057, date of approval (latest amendment): 10. December 2024); all data was collected in accordance with the Declaration of Helsinki. The study was registered at the German Register of Clinical Studies (DRKS, project number DRKS00029042). Written consent was obtained from all patients. The present analysis included all hospitalized patients with AMI between 2000 and 2017, who were discharged alive and survived at least 28 days after the AMI, thereby focusing exclusively on long-term mortality. Patients who died within the first 28 days were excluded. STEMI cases were defined as a physician-confirmed diagnosis of an acute coronary syndrome accompanied by new STsegment elevations in the admission ECG (ST-segment elevations in 2 or more contiguous leads greater than 0.1 mV at the J point) and elevated cardiac enzymes; NSTEMI cases included all cases of acute coronary syndromes with elevated cardiac enzymes and no or unspecific ECG changes. We excluded all patients with missing values for heart rate or systolic blood pressure at hospital discharge. The last documented values for resting blood pressure and heart rate on the day of (...truncated)