Novel post-AMI mortality risk model may perform better than existing references

1. In this prospective modeling study of elderly adults who were hospitalized for acute myocardial infarction, the novel SILVER-AMI model appeared well-calibrated and had improved discrimination when compared the the commonly-used GRACE model.

2. Unique to the SILVER-AMI, several functional impairments were found to be independently associated with mortality and were included in the final multivariable model.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Acute myocardial infarction (AMI) risk guidelines are commonly used to assist clinical decision making, but existing models are based on a younger cohort with limited calibration in older adults, who are more vulnerable due to lower physiological reserve and greater numbers of comorbidities. This study proposed a novel stratified 6-month mortality risk model (SILVER-AMI) and tested its performance against that of the established Global Registry of Acute Coronary Events (GRACE) 6-month mortality risk score. While the two models shared many key variables such as heart rate and revascularization status, the incorporation of multiple additional risk factors such as functional impairment and comorbidity into the SILVER-AMI resulted in superior predictive accuracy when applied to the validation cohort. However, this new model was not externally validated, meaning that generated estimates ought to be used with caution in other populations. Another limitation was that the overall mortality rate in the internal dataset was lower than results from previous cohort studies would suggest. This trend may reflect either advances in care or bias due to a healthy enrollee effect. Finally, the cause of death was not distinguished in roughly a third of the sample population, making it difficult to link predictors with specific outcomes. Nonetheless, this model was relatively well calibrated and may be utilized to inform prognostication for older patients at time of discharge.

Click here to read the study in Annals of Internal Medicine

Click here to read an accompanying editorial in Annals of Internal Medicine

Relevant Reading: Risk Factors Associated With Major Cardiovascular Events 1 Year After Acute Myocardial Infarction

In-Depth [prospective cohort]: This multicenter observational study was conducted in the United States and involved 3006 patients over the age of 75 who were hospitalized for AMI and were subsequently discharged. The primary outcome was 6-month mortality as determined by medical records, death certificates, obituaries, or secondary report. Causes of death were classified as cardiovascular, non-cardiovascular, or unknown. A broad range of predictors were tested for inclusion in the final model, including general cognitive function, verbal fluency, upper-extremity strength, functional mobility, depressive symptoms, and fall history. Thresholds were established according to clinical relevance and distributions, and variables were then omitted based on missingness and prevalence (<5% or >95%). 15 variables were found to be associated with 6-month mortality, the strongest being receipt of in-hospital coronary artery bypass graft (protective), age, length of stay, self-reported health status, and unintentional weight loss. Consideration of functional impairments also significantly bolstered model performance. The final multivariable model demonstrated improved discrimination compared with the GRACE mortality risk score (AUC=0.84 vs. 0.76; P<0.001), and integrated predictiveness curves suggested that SILVER-AMI was able to better identify patients at both higher risk and lower risk.

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