Metabolic dysregulation and cardiomyocyte dysfunction in diabetes
Hyperglycemia and IR
Hyperglycemia profoundly disrupts the energy metabolism of cardiomyocytes by suppressing glucose oxidation, increasing free fatty acid oxidation, reducing ATP production efficiency, and promoting mitochondrial dysfunction7,8,9. Enhanced fatty acid oxidation, mediated by PPARα upregulation, intensifies lipid accumulation and oxidative stress10,11,12. IR impairs myocardial glucose metabolism by reducing GLUT4 translocation and glucose uptake13. PCI-induced transient ischemia further downregulates GLUT4 and insulin signaling, creating an energy deficit that predisposes patients to post-PCI low cardiac output syndrome and HF. IR shifts myocardial substrate use towards fatty acids. Although fatty acids normally contribute substantially to cardiac energy production, excessive dependence on their oxidation increases lipid accumulation and the generation of reactive oxygen species (ROS), thereby promoting lipotoxicity and mitochondrial dysfunction14,15,16.
These substrate metabolic abnormalities were first mechanistically validated in H9c2 cardiomyocyte lines and db/db diabetic rodent models, which provide causal experimental evidence linking hyperglycemia-lipotoxicity to cardiac dysfunction. Retrospective clinical FDG-PET cohort observations in type 2 diabetic PCI patients support correlative associations between sustained insulin resistance and impaired myocardial glucose utilization; however, large-scale human interventional trials targeting PPARα or myocardial fatty acid metabolism to reverse post-PCI cardiac injury are still lacking to confirm direct clinical causality.
AGE-RAGE Axis
Advanced glycation end products accumulate in the diabetic myocardium and bind RAGE, triggering oxidative stress, inflammation, and fibrosis17,18. PCI-induced vessel trauma amplifies AGE-RAGE signaling, promoting neointimal hyperplasia, microvascular dysfunction, and post-PCI heart failure with preserved ejection fraction (HFpEF). AGE-RAGE signaling activates NF-κB, increasing IL-6 and TNF-α, recruiting M1 macrophages, and intensifying ischemia-reperfusion (I/R) injury19,20,21. Soluble RAGE attenuates these effects. The AGE-RAGE axis promotes cardiac fibroblast differentiation and extracellular matrix deposition via the PI3K/Akt and NF-κB pathways22. Dapagliflozin and liraglutide inhibit AGE-RAGE-mediated injury23.
Myocardial biopsy samples from patients with diabetic heart failure confirm elevated tissue AGE deposition as a clinical correlate, while knockout animal models establish a direct causal role for RAGE signaling in cardiac remodeling. No phase 2/3 human clinical trials have yet demonstrated that selective inhibition of the AGE-RAGE pathway reduces HF events after PCI, meaning causal human clinical evidence remains preliminary.
Inflammatory responses and PCI-specific mechanisms
Chronic inflammation and the NLRP3 inflammasome
Chronic low-grade inflammation in the diabetic myocardium is driven by pro-inflammatory cytokines, including TNF-α and IL-6, which activate the NF-κB and MAPK signaling pathways24. Activation of the NLRP3 inflammasome promotes the release of IL-1β and IL-18, leading to pyroptotic cell death25. During PCI, patients with diabetes exhibit an exaggerated acute-phase inflammatory response characterized by elevated IL-6 and C-reactive protein (CRP) levels, contributing to myocardial depression and microvascular obstruction. A predominance of pro-inflammatory M1 macrophages further sustains chronic inflammation26. In addition, activation of the cyclic GMP-AMP synthase–stimulator of interferon genes (cGAS–STING) pathway by mitochondrial DNA leakage amplifies cytokine production and inflammatory signaling27.
During PCI, ischemia-reperfusion (I/R) injury activates both NF-κB and the NLRP3 inflammasome. In the diabetic myocardium, pre-existing NLRP3 priming and mitochondrial dysfunction amplify myocardial injury through several mechanisms: (1) excessive reactive oxygen species (ROS) production; (2) rapid NLRP3 inflammasome activation; (3) pre-existing endothelial dysfunction that predisposes to the no-reflow phenomenon; and (4) distal coronary microembolization28. Consequently, patients with diabetes experience larger infarct sizes and higher rates of no-reflow following PCI.
Importantly, this inflammatory response is not unique to diabetes. Genetic polymorphisms involving IL-6, IL-1β, and NLRP3 influence individual susceptibility to inflammatory injury. Consequently, not all patients with diabetes develop post-PCI HF, with an estimated incidence of 20%–30% at 5 years, whereas some individuals without diabetes but with a pro-inflammatory phenotype may develop similar complications29.
This shared systemic inflammatory amplification cascade can also be observed in patients with COVID-19 complicated by heart failure, serving as an illustrative parallel clinical example of identical NF-κB/NLRP3-driven cardiac remodeling pathways rather than an unrelated pathogenic process30. These findings support the concept that inflammation represents a common final pathway linking diverse metabolic, infectious, and ischemic insults.
NF-κB–NLRP3 crosstalk and fibrosis
NF-κB and the NLRP3 inflammasome form a positive feedback loop in which NF-κB upregulates NLRP3 expression, whereas NLRP3-mediated IL-1β release further enhances NF-κB signaling31. This bidirectional crosstalk promotes cardiac fibrosis and myocardial dysfunction following PCI32. Accordingly, systemic inflammatory biomarkers, including the systemic immune-inflammation index (SII) and the fibrinogen-to-albumin ratio (FAR), have emerged as important predictors of adverse post-PCI outcomes (Figure 2)33.
Transforming growth factor-β1 (TGF-β1) promotes myocardial fibrosis through both Smad-dependent and p38 MAPK signaling pathways34. PCI-induced vascular injury activates circulating fibroblasts, and in the diabetic myocardium, upregulation of TGF-β1 accelerates diffuse myocardial fibrosis and the development of heart failure with preserved ejection fraction (HFpEF)35,36. Galectin-3 further promotes inflammation and acts synergistically with TGF-β1 to exacerbate fibrotic remodeling37.
The reciprocal NF-κB–NLRP3 positive feedback loop driving pyroptosis and cardiac fibrosis is definitively validated in diabetic I/R mouse models and primary human cardiac macrophage cell culture. In clinical diabetic PCI cohorts, circulating IL-1β, TNF-α, SII, and FAR serve as indirect surrogate readouts reflecting pathway activation. However, selective NLRP3 inhibitors have only demonstrated cardiac-protective effects in preclinical studies; prospective randomized human trials demonstrating that NLRP3 blockade reduces post-PCI HF hospitalizations are still ongoing, meaning this therapeutic mechanism remains proposed rather than clinically confirmed in humans.
PCI-specific mechanisms of myocardial injury
PCI introduces several forms of myocardial injury that are exacerbated in patients with diabetes. These include: (1) ischemia-reperfusion (I/R) injury, which is intensified by mitochondrial dysfunction and excessive reactive oxygen species (ROS) production; (2) microvascular obstruction and the no-reflow phenomenon, occurring in approximately 25%–40% of patients with diabetes presenting with ST-segment elevation myocardial infarction (STEMI), primarily due to distal embolization, endothelial injury, and vasospasm; (3) stent-associated inflammation, which promotes exaggerated neointimal hyperplasia; (4) coronary microembolization, resulting in cumulative myocardial injury because of impaired reparative capacity; and (5) contrast-induced nephropathy, which contributes to systemic inflammation and volume overload, thereby further increasing the risk of HF.
Cardiomyocyte death pathways
Mitochondrial apoptosis
Mitochondrial apoptosis is characterized by the loss of mitochondrial membrane potential (Δψm), opening of the mitochondrial permeability transition pore (mPTP), and subsequent cytochrome c release38. PCI-induced I/R injury triggers mPTP opening, whereas chronic ROS exposure primes diabetic mitochondria for enhanced susceptibility to apoptosis, resulting in greater cytochrome c release and poorer recovery of left ventricular ejection fraction (LVEF)39. In addition, dysregulated mitochondrial fission and fusion dynamics, together with impaired mitophagy, further exacerbate apoptotic cell death40.
Endoplasmic reticulum stress and apoptosis
Endoplasmic reticulum (ER) stress induced by hyperglycemia, advanced glycation end products (AGEs), and lipotoxicity activates the unfolded protein response (UPR) through the PERK, IRE1α, and ATF6 signaling pathways41. PCI-related I/R injury further exacerbates ER stress, and in diabetic cardiomyocytes with chronically activated UPR signaling, this initially adaptive response shifts toward apoptosis via upregulation of C/EBP homologous protein (CHOP)42,43,44.
Autophagy dysfunction
Diabetes impairs autophagic activity through downregulation of the Klotho/SIRT1 signaling pathway45. During PCI-induced I/R injury, efficient autophagic clearance is essential for removing damaged cellular components; however, impaired autophagic flux in the diabetic myocardium results in the accumulation of dysfunctional organelles, thereby exacerbating myocardial stunning and HF46. Metformin has been shown to enhance autophagic activity47, whereas sodium-glucose cotransporter 2 (SGLT2) inhibitors suppress excessive autophagy-associated cell death through inhibition of the sodium–hydrogen exchanger 1 (NHE1; Table 1)48.
Clinical risk factors, biomarkers, and AI-based prediction
Clinical characteristics
HbA1c exhibits a U-shaped association with MACE, whereby both levels below 6.5% and poor glycemic control are associated with an increased risk49. hs-CRP and estimated glomerular filtration rate predict the risk of HF at 1 year50. Elevated angio-Index of Microcirculatory Resistance predicts a high risk of MACE at 2 years; the no-reflow phenomenon is more prevalent in patients with diabetes51.
Biomarkers
Established routine clinical biomarkers
NT-proBNP and cardiac troponin are guideline-endorsed, standardized circulating markers of myocardial injury and ventricular wall stress52. For post-PCI diabetic patients, NT-proBNP >300 pg/mL at the 30-day outpatient follow-up serves as a validated cutoff for elevated long-term HF and mortality risk. Serial detection at pre-PCI baseline, 24 h post-procedure, and 90-day follow-up demonstrates excellent intra-individual assay reproducibility. When added to traditional clinical risk-scoring systems, NT-proBNP improves the AUC for predicting 5-year MACE by approximately 0.10–0.12, providing consistent incremental prognostic value. High-sensitivity troponin measured within 24 h after PCI identifies acute microvascular myocardial injury; persistent troponin elevation beyond 72 h independently predicts early HF decompensation. hs-CRP is routinely tested to reflect baseline systemic inflammation, with a widely accepted clinical threshold of >2 mg/L for elevated cardiovascular risk.
Investigational novel inflammatory, fibrotic and metabolic biomarkers
Ceramides and proteomic panels identify high-risk individuals53; ANGPTL7 links IR to HF54; GDF-15 and galectin-3 reflect fibrosis55,56; and epicardial adipose thickness and miRNAs (miR-223-3p) are emerging markers57. The systemic immune-inflammation index (SII) and fibrinogen-to-albumin ratio (FAR) are derived from routine blood counts to quantify the chronic inflammatory burden. These inflammatory composite indices (SII, FAR), circulating cytokines (IL-1β, TNF-α), fibrotic markers (galectin-3, GDF-15), and microRNAs are only supported by single-center retrospective PCI cohort data. No universal, multi-ethnic validated cutoff thresholds have been established for clinical risk stratification. Detection protocols lack standardized commercial assays, limiting cross-laboratory reproducibility. Furthermore, these novel biomarkers provide only modest incremental predictive gains when combined with the gold-standard troponin + NT-proBNP panel, and none have been incorporated into ACC/ESC clinical practice guidelines for routine screening.
Acute injury biomarkers (troponin, IL-6) require sampling within 24 h post-PCI to capture procedural I/R damage, whereas chronic inflammatory and fibrotic markers (SII, FAR, NT-proBNP, galectin-3) are best quantified at 30 and 90 days to track sustained adverse myocardial remodeling.
AI-based risk prediction
Current standardized risk stratification tools recommended by cardiovascular societies include GRACE, SYNTAX, and chronic heart failure linear regression risk scores. These models integrate age, glycemic status, procedural data, troponin, and NT-proBNP values via fixed linear equations, have undergone large-scale multi-registry external validation, and feature universally accepted risk cutoffs for routine bedside clinical use.
Machine learning algorithms (random forest, gradient boosting, SVM, and XGBoost) outperform conventional models by 15%–20% in predictive accuracy, with area under the curve values of 0.85–0.92 and 0.70–0.78 for traditional risk scores58. SHAP enhances interpretability. Models incorporate glycemic variability, inflammatory trajectories, and procedural variables and can detect nonlinear interactions that conventional clinical assessment may overlook. Parizad et al. demonstrated that AI-based risk prediction improves cardiovascular risk stratification by 15%–20% compared with multivariate regression alone58.
Despite superior internal predictive performance in retrospective training cohorts, all currently reported machine learning prediction frameworks remain investigational tools rather than clinically deployable systems. Critical translational gaps persist: most AI models lack external validation across multi-center, multi-ethnic PCI registries; no standardized online calculators or guideline recommendations exist for AI risk scoring; prospective clinical trials verifying their real-world prognostic benefit over conventional scores are absent. A clear distinction exists between regression-based risk tools ready for daily patient care and exploratory AI algorithms that require further validation before widespread adoption.
Multi-target early intervention strategies
Sodium-glucose cotransporter 2 (SGLT2) inhibitors and glucagon-like peptide-1 receptor agonists (GLP-1RAs): CVOT data and clinical implementation
Sodium-glucose cotransporter 2 (SGLT2) inhibitors may improve myocardial metabolism by enhancing ketone body utilization, reducing inflammation by inhibiting NF-κB signaling, and suppressing NHE1 activity to limit autophagy-associated cell death59,60. The EMPA-REG trial demonstrated a 38% reduction in cardiovascular death, DAPA-HF reported a 26% reduction in worsening HF or cardiovascular death, and the DELIVER trial showed significant clinical benefits in patients with HFpEF61,62. Furthermore, early initiation of SGLT2 inhibitors (within ≤72 h after PCI) was associated with a 32% reduction in the risk of HF hospitalization in a real-world registry (2024–2026). The SELECT trial demonstrated that semaglutide reduced major adverse cardiovascular events (MACE) by 20%, although its effect on HF outcomes was more modest (hazard ratio [HR]: 0.86)63. Overall, SGLT2 inhibitors provide greater protection against HF-related outcomes, whereas glucagon-like peptide-1 receptor agonists (GLP-1RAs) offer superior benefits for weight reduction and glycemic control64.
A practical periprocedural strategy includes: (1) continuing therapy in clinically stable patients; (2) initiating treatment 24–72 h after PCI in treatment-naïve patients; (3) deferring therapy in hemodynamically unstable patients; and (4) exercising caution in patients with an estimated glomerular filtration rate (eGFR) <30 mL/min/1.73 m2. SGLT2 inhibitors do not increase the risk of contrast-induced acute kidney injury (CI-AKI); instead, meta-analyses have demonstrated neutral or protective effects65. GLP-1RAs are generally safe; however, gastrointestinal adverse effects may interfere with adequate oral intake.
Distinguishing early post-PCI myocardial stunning from HFpEF is clinically important. Myocardial stunning typically peaks within 24–48 h, is self-limiting, and is characterized by regional wall motion abnormalities. In contrast, HFpEF is persistent and is characterized by preserved left ventricular ejection fraction (LVEF) and diastolic dysfunction. A pulmonary capillary wedge pressure (PCWP) >15 mmHg beyond 72 h strongly suggests true HF rather than transient myocardial stunning66 (Table 2).
Metabolic modulators and comprehensive management
Trimetazidine and ranolazine promote a metabolic shift from fatty acid oxidation to glucose oxidation, thereby improving myocardial energy efficiency67. Gut microbiota-targeted therapeutic strategies are also emerging as promising approaches for improving cardiometabolic health68. Comprehensive management should integrate glycemic, lipid, and blood pressure control with lifestyle modification and participation in cardiac rehabilitation programs69,70. Multidisciplinary care addressing cardiovascular-kidney-metabolic (CKM) syndrome is essential for optimizing outcomes in this high-risk population (Figure 3).
Molecular imaging for precision management of post-PCI HF in patients with diabetes
Molecular imaging techniques, particularly positron emission tomography (PET) and cardiac magnetic resonance (CMR) imaging, are valuable tools for evaluating myocardial metabolic abnormalities, inflammation, and fibrosis in patients with HF and ischemic heart disease. PET using fluorine-18 fluorodeoxyglucose (18F-FDG) enables visualization and quantification of myocardial glucose uptake, serving as a surrogate marker of metabolic activity and myocardial viability71,72. When combined with myocardial perfusion imaging, PET can identify dysfunctional yet viable myocardium (hibernating myocardium) that may benefit from revascularization. In patients with diabetes following PCI, serial 18F-FDG PET imaging may facilitate monitoring of myocardial metabolic recovery and identify patients with persistent metabolic inflexibility who remain at high risk of HF.
Hybrid PET/MRI systems can simultaneously assess myocardial perfusion, metabolism, and fibrosis, providing a comprehensive evaluation of cardiovascular risk. Complementary CMR techniques, particularly parametric mapping and magnetic resonance spectroscopy, provide high-resolution structural and functional information while enabling noninvasive assessment of myocardial fibrosis and edema, both of which are closely associated with diabetic cardiomyopathy.
Emerging molecular imaging tracers targeting specific metabolic pathways, including carbon-11 palmitate for evaluating fatty acid metabolism, are expanding the scope of myocardial metabolic assessment. Additional novel tracers are under development to facilitate more precise phenotyping of HF subtypes and personalized therapeutic monitoring73,74.
For imaging inflammation and fibrosis, PET tracers such as gallium-68 DOTATATE (68Ga-DOTATATE) specifically detect arterial inflammation by targeting somatostatin receptor subtype 2 expressed on activated macrophages within atherosclerotic plaques75. Likewise, Ga-labeled fibroblast activation protein inhibitor-04 (68Ga-FAPI-04) PET detects active myocardial fibroblast proliferation several weeks before late gadolinium enhancement (LGE) becomes detectable, thereby providing an early therapeutic window for antifibrotic intervention76. CMR with LGE and T1 mapping further enables quantification of diffuse myocardial fibrosis and extracellular volume (ECV) expansion, facilitating the detection of early myocardial remodeling before overt clinical manifestations develop77.
Despite their considerable diagnostic potential, several barriers currently limit routine clinical implementation. Cost remains a major limitation, with a single 18F-FDG PET/MRI examination costing approximately US$3,000–5,000 in the United States and 68Ga-DOTATATE PET requiring an additional US$4,000–6,000. Availability is largely restricted to tertiary academic centers because 68Ga tracers require on-site cyclotron production. Furthermore, reimbursement for these advanced imaging modalities in the post-PCI setting has not yet been established, and image interpretation requires specialized expertise that is not widely available.
To address these limitations, a tiered imaging strategy is proposed. Tier 1 (widely available) consists of echocardiography with strain imaging and NT-proBNP measurement for initial risk stratification in all patients with diabetes who develop HF symptoms following PCI. Tier 2 (selective availability) incorporates CMR with T1 mapping and LGE in high-risk patients (age >65 years, multiple comorbidities, or unexplained symptoms) to quantify fibrosis and evaluate microvascular dysfunction. Tier 3 (specialized centers) includes 18F-FDG PET/CT in patients with persistent symptoms despite negative Tier 2 findings to assess myocardial metabolism and inflammation. Tier 4 (investigational) comprises 68Ga-DOTATATE or 68Ga-FAPI-04 PET in patients with refractory HF who are candidates for novel anti-inflammatory therapies, enabling quantification of macrophage-mediated inflammation and fibroblast activation.
For patients undergoing Tier 2–4 evaluation, high-risk candidates include those with post-PCI HF symptoms (New York Heart Association [NYHA] class ≥II) and either LVEF 40%–50%, unexplained dyspnea despite preserved LVEF, or NT-proBNP >300 pg/mL without an identifiable cause. Initial assessment should begin with CMR incorporating T1 mapping and LGE. Patients demonstrating myocardial fibrosis (ECV >30% or LGE >5% of left ventricular mass) should subsequently undergo a Tier 3 evaluation.
Quantitative PET assessment uses standardized uptake values (SUVs). On 18F-FDG PET, an SUV >3.0 indicates active inflammation, an SUV of 2.0–3.0 indicates borderline inflammatory activity, and an SUV <2.0 suggests quiescent disease. On 68Ga-DOTATATE PET, an SUV >2.5 correlates with macrophage activation and predicts responsiveness to anti-inflammatory therapy.
Therapeutic decisions should be guided by imaging findings. High inflammatory activity (SUV >3.0) supports initiation or optimization of anti-inflammatory therapies, including SGLT2 inhibitors, colchicine, or IL-1β inhibitors. Marked myocardial fibrosis (ECV >35%) supports optimization of antifibrotic therapy with SGLT2 inhibitors and GLP-1RAs. Patients with minimal inflammatory or fibrotic activity should receive standard guideline-directed HF management, whereas 68Ga-FAPI-04 uptake >4.0 supports early initiation of SGLT2 inhibitors with close monitoring for HF progression.
Therapeutic monitoring should include repeat imaging after 6–12 months. A reduction in SUV >30% or a decrease in ECV >3% indicates an adequate therapeutic response, whereas a smaller reduction (<30% SUV reduction) suggests the need for treatment escalation through the addition of GLP-1RAs, colchicine, or IL-1β inhibitors. Although resource-intensive, this framework provides a practical roadmap for integrating molecular imaging into clinical practice and will require multidisciplinary collaboration among cardiologists, radiologists, nuclear medicine specialists, and health economists to establish cost-effective clinical applications78.
Clinical translation and implementation challenges
Current international guidelines from the American College of Cardiology (ACC), American Heart Association (AHA), and European Society of Cardiology (ESC) (2024–2026) recommend SGLT2 inhibitors for patients with type 2 diabetes mellitus (T2DM) and established cardiovascular disease, irrespective of baseline glycemic control (Class I, Level A evidence). Similarly, GLP-1RAs receive a Class I, Level A recommendation for patients with T2DM and established atherosclerotic cardiovascular disease. Although the optimal timing of therapy initiation following PCI remains under investigation, current evidence supports early initiation (within 72 h of PCI) in hemodynamically stable patients.
A structured risk-stratification strategy should be adopted for patients with diabetes undergoing PCI. Patients aged >65 years should be considered for early advanced imaging. Those with HbA1c >8% or <6.5% require optimization of glycemic control. Patients with an eGFR <60 mL/min/1.73 m2 require close renal monitoring and medication adjustment. Patients with NT-proBNP >300 pg/mL should undergo echocardiography and receive guideline-directed medical therapy. Those with diabetes and an LVEF <50% should receive SGLT2 inhibitor therapy. Patients with a prior HF hospitalization require comprehensive HF management, whereas those with an angiography-derived index of microcirculatory resistance (angio-IMR) >40 should be considered to have significant microvascular dysfunction and may particularly benefit from SGLT2 inhibitor therapy.
The timing of medical therapy relative to PCI is also critical. SGLT2 inhibitors should be initiated before PCI or within 72 h afterward based on observational and registry evidence. GLP-1RAs should be initiated before PCI or within 7 days after PCI according to current observational data. Antiplatelet therapy should be initiated immediately before PCI (Class I, Level A evidence), whereas statin therapy should be initiated or intensified immediately before PCI or within 24 h afterward (Class I, Level A evidence). Cardiac rehabilitation should begin within 2 weeks following PCI (Class I, Level A evidence).
Despite these advances, several barriers continue to impede clinical implementation. Post-PCI HF remains underdiagnosed because symptoms are often attributed to the procedure itself, delaying recognition. Diagnostic uncertainty persists because distinguishing myocardial stunning, HFpEF, and heart failure with reduced ejection fraction (HFrEF) often requires specialized testing. Additional challenges include the high cost and limited availability of advanced imaging and novel therapies; inconsistent guideline recommendations across cardiology and endocrinology societies; reduced adherence due to complex polypharmacy; healthcare disparities that limit access for underserved populations; and fragmented multidisciplinary care.
To overcome these barriers, several implementation strategies are proposed, including structured screening protocols incorporating routine NT-proBNP assessment at 30 and 90 days after PCI, integrated care pathways involving cardiology, endocrinology, and primary care, implementation of clinical decision-support tools within electronic health record systems, comprehensive patient education to improve symptom recognition and self-management, quality improvement initiatives that monitor post-PCI HF outcomes as performance indicators, and expanded use of telemedicine to facilitate remote monitoring of HF symptoms and biomarkers.