Background/Objectives: Acute kidney injury (AKI) is a common and severe complication in patients with acute myocardial infarction (AMI). Very elderly patients are at a heightened risk of developing AKI. Fibrinogen and albumin are well-known biomarkers of inflammation and nutrition, which are highly related to AKI. We aim to explore the predictive value of the fibrinogen-to-albumin ratio (FAR) for AKI in very elderly patients with AMI. Methods: A retrospective cohort of AMI patients ≥ 75 years old hospitalized at the First Affiliated Hospital of Xi’an Jiaotong University between January 2018 and December 2022 was established. Clinical data and medication information were collected through the biospecimen information resource center at the hospital. Univariate and multivariable logistic regression models were used to analyze the association between FAR and the risk of AKI in patients with AMI. FAR was calculated as the ratio of fibrinogen (FIB) to serum albumin (ALB) level (FAR = FIB/ALB). The primary outcome is acute kidney injury, which was diagnosed based on KDIGO 2012 criteria. Results: Among 1236 patients enrolled, 66.8% of them were male, the median age was 80.00 years (77.00–83.00), and acute kidney injury occurred in 18.8% (n = 232) of the cohort. Comparative analysis revealed significant disparities in clinical characteristics between patients with or without AKI. Patients with AKI exhibited a markedly higher prevalence of arrhythmia (51.9% vs. 28.1%, p < 0.001) and lower average systolic blood pressure (115.77 ± 25.96 vs. 122.64 ± 22.65 mmHg, p = 0.013). In addition, after adjusting for age, sex, history of hypertension, left ventricular ejection fraction (LVEF), and other factors, FAR remained an independent risk factor for acute kidney injury (OR = 1.47, 95%CI: 1.36–1.58). ROC analysis shows that FAR predicted stage 2–3 AKI with superior accuracy (AUC 0.94, NPV 98.6%) versus any AKI (AUC 0.79, NPV 93.0%), enabling risk-stratified management. Conclusions: FAR serves as both a high-sensitivity screening tool for any AKI and a high-specificity sentinel for severe AKI, with NPV-driven thresholds guiding resource allocation in the fragile elderly.

Background: Intracardiac thrombus is a clinically important complication of acute myocardial infarction (AMI), particularly in patients with ventricular aneurysm. We examined the contemporaneous associations of anterior ventricular involvement and D-dimer with echocardiographically documented intracardiac thrombus with incomplete chamber-specific localization among hospitalized AMI patients with ventricular aneurysm. Methods: This retrospective analysis included 1684 patients with documented ventricular aneurysm from a final cohort of 17,950 hospitalized AMI patients treated between January 2018 and October 2025. The first D-dimer measurement obtained at our hospital after AMI confirmation was used for D-dimer analyses. Ventricular aneurysm and intracardiac thrombus status were determined from the available echocardiographic documentation during the index hospitalization. Aneurysm locations were coded as linked patient-level, non-mutually exclusive indicators. Logistic regression evaluated anterior involvement; missing model covariates were multiply imputed and regression estimates were pooled using Rubin’s rules. Collinearity diagnostics and sensitivity analyses restricted to patients with apical aneurysm, including a complete-case analysis, were performed. Model-performance measures were interpreted as exploratory apparent performance in the development dataset. Results: Intracardiac thrombus was documented in 211 of 1684 patients (12.5%). Anterior involvement was more frequent among patients with thrombus than among those without thrombus (57.3% vs. 45.0%; p < 0.001) and remained associated with thrombus in the primary anatomical and clinical model (OR, 1.63; 95% CI, 1.20–2.21; p = 0.002). D-dimer was available in 1633 patients. On the log2-transformed scale, each doubling of D-dimer was associated with higher odds of echocardiographically documented intracardiac thrombus (adjusted OR, 1.24; 95% CI, 1.14–1.34; p < 0.001). As a complementary descriptive analysis, the observed thrombus proportion increased from 3.63% in Q1 to 22.30% in Q4; compared with Q1, the adjusted ORs were 3.71, 5.22, and 9.50 in Q2, Q3, and Q4, respectively. The combined model had a mean apparent AUC of 0.716, compared with 0.713 for the model containing D-dimer without anterior involvement; the mean absolute increment was approximately 0.003. Conclusions: Among hospitalized patients with AMI and ventricular aneurysm, higher D-dimer levels and anterior ventricular involvement were associated with echocardiographically documented intracardiac thrombus. Chamber-specific localization was incomplete, and these contemporaneous associations do not establish causality or prospective prediction. Anterior involvement provided minimal incremental discrimination beyond D-dimer.