Diabetes-related foot ulceration (DFU), a serious but preventable complication of diabetes, is a leading cause of hospitalisation, lower extremity amputation and disability worldwide. People with DFU have a greater burden of cardiovascular risk factors, heart failure and chronic kidney disease, resulting in over two-fold higher risk of cardiovascular death compared with people with diabetes without DFU. Here, we propose a “cardio-renal-metabolic-foot” connection in people with diabetes based on shared pathophysiological mechanisms linking DFU with cardiovascular and renal disease. Whilst these mechanistic links remain to be fully elucidated, systemic inflammation and infection in the context of DFU are postulated as key mediators in the development, and progression of, cardiovascular and renal disease. However, cardiovascular and renal disease are also implicated in the pathogenesis of DFU, highlighting the multi-directional interplay between conditions. The impact of screening, prevention, and early management of cardiovascular complications associated with DFU requires further research. Multi-modality cardiac imaging could play a role in unravelling disease mechanisms leading to novel therapeutic strategies, as well as facilitating personalised risk assessment and management. Recent clinical trials have transformed the therapeutic landscape for people with type 2 diabetes, by demonstrating that sodium glucose co-transporter 2 inhibitors, glucagon-like peptide-1 agonists and non-steroidal mineralocorticoid receptor antagonists improve cardiovascular and renal outcomes. Although dedicated research in people with DFU is warranted, these therapies could target multiple facets of the “cardio-renal-metabolic-foot” connection. The holistic, person-centred approach to managing DFU should incorporate new multidisciplinary models of care focusing on the prevention and management of cardiovascular and kidney disease. Graphical abstract The cardio-renal-metabolic-foot connection in people with diabetes. There is a critical need for (1) a better understanding of mechanisms connecting DFU with cardiovascular and kidney disease, perhaps guided by cardiac imaging, novel biomarkers, multi-omics and artificial intelligence to facilitate current treatments and the development of novel therapeutic strategies, (2) more data from clinical trials, registries and biobanks to inform clinical guidelines and evidence-based medicine, and (3) health system-wide integration of structured models of care with a contemporary emphasis on cardio-renal-metabolic-foot health to improve patient outcomes. DFU diabetes-related foot ulceration. Created with BioRender.com

Background: Diabetes-related foot ulceration (DFU) is a common complication of diabetes, with a significant impact on survival, health care costs, and health-related quality of life. The prognosis of DFU varies widely among individuals. The International Working Group on the Diabetic Foot recently updated their guidelines on how to classify ulcers using “classical” classification and scoring systems. No system was recommended for individual prognostication, and the group considered that more detail in ulcer characterization was needed and that machine learning (ML)–based models may be the solution. Despite advances in the field, no assessment of available evidence was done. Objective: This study aimed to identify and collect available evidence assessing the ability of ML-based models to predict clinical outcomes in people with DFU. Methods: We searched the MEDLINE database (PubMed), Scopus, Web of Science, and IEEE Xplore for papers published up to July 2023. Studies were eligible if they were anterograde analytical studies that examined the prognostic abilities of ML models in predicting clinical outcomes in a population that included at least 80% of adults with DFU. The literature was screened independently by 2 investigators (MMS and DAR or EH in the first phase, and MMS and MAS in the second phase) for eligibility criteria and data extracted. The risk of bias was evaluated using the Quality In Prognosis Studies tool and the Prediction model Risk Of Bias Assessment Tool by 2 investigators (MMS and MAS) independently. A narrative synthesis was conducted. Results: We retrieved a total of 2412 references after removing duplicates, of which 167 were subjected to full-text screening. Two references were added from searching relevant studies’ lists of references. A total of 11 studies, comprising 13 papers, were included focusing on 3 outcomes: wound healing, lower extremity amputation, and mortality. Overall, 55 predictive models were created using mostly clinical characteristics, random forest as the developing method, and area under the receiver operating characteristic curve (AUROC) as a discrimination accuracy measure. AUROC varied from 0.56 to 0.94, with the majority of the models reporting an AUROC equal or superior to 0.8 but lacking 95% CIs. All studies were found to have a high risk of bias, mainly due to a lack of uniform variable definitions, outcome definitions and follow-up periods, insufficient sample sizes, and inadequate handling of missing data. Conclusions: We identified several ML-based models predicting clinical outcomes with good discriminatory ability in people with DFU. Due to the focus on development and internal validation of the models, the proposal of several models in each study without selecting the “best one,” and the use of nonexplainable techniques, the use of this type of model is clearly impaired. Future studies externally validating explainable models are needed so that ML models can become a reality in DFU care. Trial Registration: PROSPERO CRD42022308248; https://www.crd.york.ac.uk/PROSPERO/view/CRD42022308248

Aims/hypothesis: Diabetes-related foot ulceration (DFU) is associated with increased cardiovascular risk, but the mechanisms remain unclear. Inflammation and infection are mediators of CVD, which may be important in DFU. Methods: Prospectively collected data from patients attending a multidisciplinary DFU service were analysed. A deep ulcer was defined as one that reached muscle, tendon or deeper structures. Patients were categorised into four DFU groups: not deep and no infection (D−/I−), not deep but infected (D−/I+), deep with no infection (D+/I−) or deep with infection (D+/I+). Incident major adverse cardiovascular events (MACE) were defined as hospitalisation for myocardial infarction, stroke or transient ischaemic attack, or heart failure. Survival analyses were performed using the logrank test and multivariate Cox regression. Results: Of 513 patients, 241 (47.0%) were in the D−/I− group, 110 (21.4%) were in the D−/I+ group, 35 (6.8%) were in the D+/I− group and 127 (24.8%) were in the D+/I+ group. MACE or all-cause mortality occurred in 75 patients (14.6%), and MACE alone occurred in 46 patients (9.0%) after median follow-up of 381 days (IQR 220–551) and 404 days (IQR 228–576), respectively. Infection was associated with significantly higher MACE or all-cause mortality (21.5% vs 8.7%; p<0.001) and MACE alone (13.5% vs 5.1%; p=0.003). MACE or all-cause mortality was significantly higher in the D+/I+ group (D−/I− 7.9%; D−/I+ 15.5%; D+/I− 14.3%; D+/I+ 26.8%; p<0.001), as was MACE alone (D−/I− 5.0%; D−/I+ 10.9%; D+/I− 5.7%; D+/I+ 15.7%; p=0.017). Infection and a deep ulcer were independent predictors of adverse outcomes. Conclusions/interpretation: Deep and/or infected DFUs are associated with increased cardiovascular risk compared with DFUs that are not deep or infected. These findings provide a potential mechanistic explanation that requires investigation. Graphical

Aims: To determine whether there is an excess of cognitive impairment in patients with type 2 diabetes and foot ulceration. Methods: 55 patients with type 2 diabetes and foot ulcers attending Multidisciplinary Diabetes Foot Ulcer clinics (MDFU cohort) were compared with 56 patients with type 2 diabetes attending Complex Diabetes clinics (CDC cohort) using commonly used screening tests for cognitive impairment (Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MOCA)), as well as foot self-care, mood and health literacy. MMSE was also compared between the MDFU cohort and a historical community-based cohort of patients with type 2 diabetes (FDS2 cohort). Results: Median MMSE scores were the same in all three groups (28/30). Median MOCA scores did not differ between the MDFU and CDC cohorts (25/30). There were no significant differences in the percentages of patients with MMSE ≤ 24 or MOCA ≤ 25 between MDFU and CDC cohorts (3.6% versus 10.7%, p = 0.27 and 56.4% versus 51.8%, p = 0.71, respectively), findings that did not change after adjustment for age, sex, education, diabetes duration, and random blood glucose. Conclusions: Using conventionally applied instruments, patients with type 2 diabetes and foot ulceration have similar cognition compared with patients without, from either hospital-based clinic or community settings.