Improved Cardiac Function and Glycemic Control in Elderly Diabetic Patients Through Structured Case Management After CABG

Introduction

Coronary heart disease (CHD) remains a leading cause of morbidity and mortality globally, affecting approximately 200 million individuals worldwide and accounting for over 9 million deaths annually [1,2]. For complex multivessel disease, coronary artery bypass grafting (CABG) is a common and effective treatment [3,4]. The evolution of off-pump CABG has presented new possibilities, yet the procedure’s complexity and potential for hemodynamic instability pose unique challenges, particularly for high-risk patient populations [5–7].

Elderly CHD patients complicated with diabetes mellitus (DM) are one such high-risk group, with prevalence estimates suggesting that 25% to 40% of patients undergoing CABG have concurrent DM [8]. This population often presents with decreased physiological reserves and multiple comorbidities [9,10]. The perioperative period is particularly risky; surgical stress can induce significant blood glucose fluctuations, and chronic hyperglycemia is known to impair protein synthesis, weaken immune function, and delay wound healing [11,12]. Consequently, these patients face an elevated risk of postoperative complications, including cardiovascular adverse events and surgical site infections, which can prolong hospitalization and adversely affect long-term prognosis [11].

Case management has emerged as a flexible, collaborative, and participatory process to deliver continuous and comprehensive healthcare [13]. By coordinating care, providing education, and allocating resources, case management models have demonstrated efficacy in various chronic disease settings, including elderly depression, asthma, and oncology [14]. However, despite evidence supporting case management in chronic disease, a critical knowledge gap persists and there remains a paucity of research on the specific impact of structured case management on the perioperative outcomes of elderly CHD patients with DM undergoing off-pump CABG. Existing studies have focused primarily on general cardiac rehabilitation or glycemic management in isolation, rather than integrated, multidisciplinary approaches targeting this high-risk population.

Therefore, the present study aimed to evaluate the clinical impact of a structured, multidisciplinary case management model on cardiac functional recovery, specifically left ventricular ejection fraction (LVEF), in elderly CHD patients with DM during the perioperative period of off-pump CABG. This study hypothesizes that a comprehensive case management approach, when compared to routine nursing care, will lead to superior cardiac functional recovery, metabolic control, and quality of life in this high-risk population.

Material and Methods

STUDY DESIGN AND PARTICIPANTS:

This single-center, randomized controlled trial enrolled 168 elderly patients (≥65 years) with established coronary heart disease (CHD) and type 2 diabetes mellitus (DM) scheduled for off-pump coronary artery bypass grafting (CABG). Recruitment occurred between October 2022 and November 2024 at the Department of Cardiovascular Surgery, the Second Hospital of Tianjin Medical University.

Inclusion criteria required that patients met WHO diagnostic criteria for both DM and ischemic heart disease, had stable disease after systematic treatment, and were stratified as low-risk for cardiac rehabilitation. All patients provided written informed consent and demonstrated good communication skills for post-discharge follow-up via telephone or WeChat. Exclusion criteria were mental disorders precluding cooperation, severe organ dysfunction (liver, kidney, brain, or lung), severe arrhythmia, or non-operative/perioperative death.

The study was approved by the hospital’s ethics committee (approval number: KY2024K321), and the trial was registered at Chinese Clinical Trial Registry (ID: ChiCTR2000034438) on July 5, 2020 (https://www.chictr.org.cn/showproj.html?proj=56119). All procedures adhered to the principles of the Declaration of Helsinki. Written informed consent was obtained from all participants.

The registration preceded patient enrollment, and all primary and secondary outcomes reported herein were pre-specified in the registered protocol. All procedures adhered to the principles of the Declaration of Helsinki. Patient confidentiality was maintained through assignment of unique study identifiers, secure electronic data storage with restricted access, and de-identification of all datasets prior to analysis.

ETHICS APPROVAL AND CONSENT TO PARTICIPATE:

This work was approved by the Ethic Committee of the Second Hospital of Tianjin Medical University (No. KY2024K321).

RANDOMIZATION AND ALLOCATION CONCEALMENT:

Eligible patients were randomly assigned in a 1: 1 ratio to either the observation group (OG, n=84) or the control group (CG, n=84). Randomization was achieved using computer-generated blocks of 4, managed by an independent statistician. Allocation was concealed using sequentially numbered, sealed, opaque envelopes, which were opened by a research nurse not involved in patient care immediately before initiating the assigned protocol. While providers and patients could not be blinded to the nursing intervention, all outcome assessors adjudicating echocardiographic data, laboratory results, and clinical endpoints were blinded to group allocation. To maintain assessor blinding, patient identifiers were removed from all echocardiographic images and laboratory reports prior to analysis, and assessors worked in a separate facility without access to clinical care records.

STANDARD PERIOPERATIVE PROTOCOLS:

All participants received standardized perioperative care. Surgical procedures were conducted via off-pump CABG under general anesthesia (propofol/remifentanil) per institutional standards. Key intraoperative hemodynamic targets, including a mean arterial pressure (MAP) >65 mmHg, were uniformly maintained.

A standardized antibiotic prophylaxis regimen was administered to all patients, consisting of intravenous cefuroxime sodium (1.5 g) at anesthesia induction, repeated every 8 h. A supplemental dose was administered intraoperatively if the procedure exceeded 3 h or blood loss surpassed 1500 mL, in accordance with institutional guidelines for surgical prophylaxis. The antibiotic course concluded after 6 days, or earlier upon normalization of the hemogram. Postoperative glycemic control followed the ADA 2024 hospital care standards, utilizing an insulin sliding scale to target a glucose level of 6 to 10 mmol/L.

INTERVENTION AND CONTROL GROUPS:

The control group (CG, n=84) received routine nursing care and follow-up. This included baseline anthropometric measurements, routine monitoring of fasting and postprandial blood glucose, and standard health education on CHD, diet, medication, and the importance of regular follow-up. Upon discharge, patients were provided with health education manuals and contact numbers for consultation, with telephone follow-up conducted monthly.

The observation group (OG, n=84) received routine care plus a structured, individualized case management intervention adapted from the Care Transitions Intervention model. The case management team comprised 2 senior cardiac nurses and a diabetologist, who convened weekly to review patient progress. This 6-month, multidisciplinary intervention began upon admission and after discharge. The team first established comprehensive electronic health records and collaborated with patients to set personalized goals.

A core component was a structured cardiac rehabilitation plan based on individual cardiopulmonary exercise tests. Exercise prescriptions were formulated based on metabolic equivalents (METs) derived from heart rate, anaerobic threshold, and peak oxygen uptake.

The dietary intervention featured a modified Mediterranean diet adapted for the Chinese population (detailed composition provided in Table 1). The key modification involved the substitution of Chinese yam (Dioscorea polystachya) porridge (approximately 150 g cooked weight) for a portion of refined grain breakfast staples (eg, white rice congee or steamed bread). This substitution was selected because Chinese yam has a lower glycemic index (GI ~53) than white rice (GI ~73) and contains bioactive compounds, including diosgenin and polysaccharides, that have demonstrated beneficial effects on postprandial glucose regulation and insulin sensitivity [15]. Total daily caloric targets (1500–1800 kcal for women; 1800–2200 kcal for men) were maintained consistent with standard Mediterranean diet principles.

Psychological support was provided using the Self-Rating Anxiety Scale (SAS) and Self-Rating Depression Scale (SDS) for screening, followed by evidence-based interventions, including cognitive-behavioral techniques. The team also provided structured health education on polypharmacy, medication adherence, and smoking cessation, and dynamically evaluated patient progress to adjust the care plan.

Protocol Fidelity and Adherence Monitoring: Intervention adherence was monitored through multiple mechanisms: (1) weekly case management team reviews documented completion of scheduled activities; (2) exercise adherence was tracked via patient diaries and corroborated during follow-up calls; (3) dietary adherence was assessed using 24-h recall at monthly intervals; and (4) WeChat group participation was logged electronically. Overall protocol adherence, defined as completion of ≥80% of scheduled intervention components, was achieved by 91.7% (77/84) of observation group patients.

Specific attention was given to infection surveillance. Incision management involved daily observation for signs of infection, with any suspected infection triggering immediate bacterial culture, drug sensitivity testing, and targeted antibiotic therapy with enhanced aseptic wound care. Infection surveillance was further validated by 2 blinded infectious disease specialists who independently adjudicated cases. Blood glucose management was intensified, with monitoring frequency (every 1–2 h) adjusted based on patient stability, medication, and nutritional intake. Post-discharge follow-up was conducted via a dedicated WeChat group, enabling continuous supervision, peer support, and reinforcement of rehabilitation goals.

OUTCOME MEASURES AND DATA COLLECTION:

The primary endpoint was change in cardiac function at 6 months after the intervention, assessed by left ventricular ejection fraction (LVEF). LVEF was measured via transthoracic echocardiography using a Philips EPIQ 7C high-resolution color Doppler ultrasound system (Philips Healthcare, Andover, MA, USA) following American Society of Echocardiography (ASE) guidelines. Additional echocardiographic parameters included left ventricular end-systolic diameter (LVESD), left ventricular end-diastolic diameter (LVEDD), end-systolic volume (ESV), and end-diastolic volume (EDV). Functional capacity was measured by the 6-min walk test (6-MWT) [16].

Key secondary endpoints included glycemic control (HbA1c), clinical biochemical indicators, postoperative infection rates, quality of life, and activities of daily living. Fasting blood samples were collected 6: 00–8: 00 AM following an overnight fast of at least 8 h, at 6 months to measure triglycerides (TG), total cholesterol (TC), HDL-C, LDL-C, and HbA1c utilizing commercially available, validated enzymatic and high-performance liquid chromatography (HPLC) assays, respectively.

Postoperative infection was defined according to Centers for Disease Control and Prevention (CDC) National Healthcare Safety Network (NHSN) criteria and included: (1) surgical site infection (superficial incisional, deep incisional, or organ/space), requiring clinical signs plus positive culture or physician-initiated treatment; (2) respiratory tract infection, requiring radiological confirmation plus clinical criteria; and (3) urinary tract infection, requiring ≥10⁵ CFU/mL with symptomatic presentation. Cases with clinical suspicion but negative cultures were not classified as infections. Postoperative body temperature and white blood cell (WBC) counts were recorded daily for the first week.

Adverse Event Monitoring: Adverse events were defined as any untoward medical occurrence during the study period and were systematically recorded at each contact point. Serious adverse events (SAEs), defined as events resulting in death, hospitalization, prolonged hospitalization, or persistent disability, were reported to the ethics committee within 24 h. All adverse events were adjudicated by an independent physician blinded to group allocation.

Quality of life and daily living activities were assessed using the Diabetes-Specific Quality of Life (DSQL) scale [17] and the Activities of Daily Living (ADL) scale [18], respectively. All validated scales (DSQL, ADL) were administered by a trained research nurse, who was not involved in providing the intervention, to ensure consistency.

STATISTICAL ANALYSIS:

The study adhered to CONSORT 2010 guidelines [19]. A priori sample size calculation was based on the primary endpoint of LVEF. Based on prior literature, we anticipated a between-group difference of 5% in LVEF change with an estimated standard deviation of 6.5%. Using a two-sided α of 0.05 and 80% power, 75 patients per group were required. We enrolled 84 per group to account for 10% attrition. All randomized patients were assessed using the intention-to-treat principle.

Data were analyzed using SPSS 27.0 and GraphPad Prism 9.0. Continuous variables conforming to a normal distribution are presented as mean±standard deviation (χ̄±s) and compared using an independent-samples t test. Categorical data are presented as rates (%) and were compared using the χ² test. A hierarchical (gatekeeping) testing strategy was used to control for multiplicity: LVEF was designated as the sole primary endpoint (significance at α=0.05). Secondary endpoints, including HbA1c and other metabolic and functional outcomes, were tested only if the primary endpoint achieved significance, using a false discovery rate (FDR) correction with the Benjamini-Hochberg procedure (q<0.05). Multivariable linear regression was performed to adjust for potential confounders. Statistical significance was defined as P<0.05 unless otherwise adjusted.

Results

PARTICIPANT CHARACTERISTICS AND BASELINE DATA:

A total of 215 patients were screened for eligibility, of whom 168 met the criteria and were randomized (Figure 1). Three patients (1.8%) were lost to follow-up, leaving 165 for per-protocol analysis. The analysis was conducted on the full intention-to-treat population (N=168).

The control (n=84) and observation (n=84) groups were well-matched at baseline. No statistically significant differences were observed in mean age (70.05 vs 69.80 years), sex distribution, or duration of DM (20.41 vs 20.50 years) (Table 2). Furthermore, preoperative clinical characteristics, including baseline left ventricular function (LVEF, LVESD, LVEDD), prevalence of comorbidities (hypertension, chronic kidney disease), and baseline medication use (beta-blockers, insulin), were comparable between the 2 groups (Table 3).

PRIMARY ENDPOINT: CARDIAC FUNCTION:

At the 6-month follow-up, the case management group demonstrated significantly improved cardiac function compared to the control group (Figure 2), as assessed by the echocardiographic methods described in Section 2.5. The primary endpoint of LVEF was significantly higher in the observation group (mean difference: 6.2%, 95% CI [3.1, 9.3], P<0.001). This was supported by corresponding reductions in left ventricular diameters, with the observation group showing significantly lower LVESD and LVEDD (P<0.001, FDR-corrected). However, no statistically significant differences were observed in ESV or EDV between the groups (P>0.05).

KEY SECONDARY ENDPOINT: GLYCEMIC CONTROL:

Given the significance of the primary endpoint, secondary endpoints were tested according to the hierarchical strategy. Glycemic control, measured by HbA1c via HPLC assay, was superior in the observation group. Patients receiving case management had a significantly lower mean HbA1c level at 6 months compared to those receiving routine care (mean difference: 1.3%, 95% CI [0.8, 1.8], P<0.001, FDR-corrected q=0.002) (Figure 3). Multivariable linear regression confirmed that the case management intervention was an independent predictor of improved LVEF (β=4.2, P=0.001) and reduced HbA1c (β=−0.9, P=0.002) after adjusting for age, diabetes duration, and preoperative LVEF.

SECONDARY ENDPOINTS: METABOLIC PROFILE AND FUNCTIONAL CAPACITY:

Improvements were also noted in the metabolic and functional secondary endpoints. The observation group exhibited a significantly improved lipid profile at 6 months, characterized by lower levels of TG, TC, and LDL-C, and higher levels of HDL-C (all FDR-corrected q<0.05) (Figure 3, Table 4). Functional capacity, as measured by the 6-MWT, was significantly greater in the observation group, with patients walking an average of 34 meters further than those in the control group (95% CI [18, 50], P=0.002, FDR-corrected q=0.008) (Figure 2).

POSTOPERATIVE CLINICAL COURSE AND SAFETY:

The postoperative clinical course was notable for a 0% incidence of CDC-defined hospital-acquired infections (surgical site, respiratory, or urinary) in both groups. It is important to note that this endpoint captured only protocol-defined infections meeting strict CDC/NHSN criteria; cases with clinical suspicion treated empirically but lacking culture confirmation were not classified as infections. While total WBC counts did not differ between groups at any postoperative time point, the febrile response was attenuated in the observation group (Figure 4). Body temperature was significantly lower in the observation group on postoperative days 1 and 3 (P<0.05) compared to the control group, but no differences were observed at other time points.

Adverse events are summarized in Table 4. There were no significant differences in serious adverse events between groups (OG: 4 [4.8%] vs CG: 8 [9.5%], P=0.243). Thirty-day readmission rates were numerically lower in the observation group (2 [2.4%] vs 7 [8.3%], P=0.087).

QUALITY OF LIFE AND FUNCTIONAL STATUS:

Patients in the case management group reported significantly better outcomes in both quality of life and daily functioning at the 6-month follow-up. The observation group had significantly higher scores on the DSQL scale and the ADL scale compared to the control group (both FDR-corrected q<0.0001) (Figure 5). Furthermore, a significant positive correlation was observed between the improvement in diabetes-specific quality of life (DSQL) and the enhancement of daily living ability (ADL), with a correlation coefficient of R2=0.8177 (P<0.0001) (Figure 6).

Discussion

This randomized controlled trial demonstrated that a structured, multidisciplinary case management model significantly improves cardiac functional recovery, metabolic control, and quality of life in elderly CHD patients with DM following off-pump CABG. Elderly patients are often susceptible to heightened perioperative stress and psychological burdens, which can negatively impact recovery [20]. Our findings suggest that the case management intervention, which included psychological screening and support, helped mitigate these factors, contributing to the observed benefits.

Our findings extend previous work demonstrating benefits of cardiac rehabilitation in post-CABG patients. The observed 6.2% improvement in LVEF exceeds the 3% to 4% improvement typically reported in standard rehabilitation programs, potentially reflecting the added value of integrated glycemic management. Similarly, the 1.3% reduction in HbA1c is consistent with intensive lifestyle interventions in diabetic populations and exceeds the 0.5% to 0.8% reductions typically achieved with routine care.

A critical aspect of this study’s design was the standardization of perioperative care, including prophylactic antibiotic administration. The standardized prophylactic cefuroxime sodium regimen was highly effective in both groups, resulting in a 0% incidence of CDC-defined hospital-acquired infections. We acknowledge that this rate is lower than the 1% to 4% deep sternal wound infection rates reported in the literature for similar populations. Several factors may account for this finding: (1) our strict CDC/NHSN criteria excluded clinically suspected but culture-negative cases; (2) patients with severe comorbidities predisposing to infection were excluded by study design; and (3) the intensive perioperative glycemic control protocol (target 6–10 mmol/L) in both groups may have contributed to lower infection risk. This finding should be interpreted with caution and may not generalize to centers with different patient populations or infection surveillance definitions.

The attenuated febrile response on postoperative days 1 and 3 in the observation group, despite no difference in WBC counts, may reflect a reduction in the systemic inflammatory response, possibly mediated by better glycemic control and overall physiological stabilization provided by the case management protocol.

A central component of the case management intervention was individualized cardiac rehabilitation. The program, which formulated exercise prescriptions based on cardiopulmonary exercise testing, aligns with current guidelines recommending MET-based regimens for high-risk coronary patients [21]. This approach was validated by the results: the observation group showed significantly higher LVEF and 6-MWT outcomes, and lower LVESD and LVEDD, consistent with research demonstrating that moderate, structured exercise enhances cardiac ejection function and vascular elasticity [22]. The lack of a significant difference in ESV and EDV may indicate that these specific volumetric measures require a longer intervention period to demonstrate change, warranting further investigation in studies with extended follow-up.

The intervention also successfully targeted the metabolic dysregulation characteristic of this population. The case management group’s rigorous, personalized approach to blood glucose monitoring and diet therapy, including the use of a Mediterranean diet structure with culturally appropriate modifications, directly translated to superior glycemic and lipid control. The significant reductions in TG, TC, LDL-C, and the gold-standard marker, HbA1c [23], underscore the efficacy of a comprehensive dietary adherence plan [24]. This metabolic improvement, combined with the structured rehabilitation, culminated in significantly higher patient-reported quality of life (DSQL) and activities of daily living (ADL) scores.

The case management model described here could be adapted for implementation in various healthcare settings. Key components – cardiac rehabilitation, dietary counseling, and systematic follow-up – are feasible in most secondary and tertiary care centers. The use of mobile technology (WeChat) for follow-up represents a scalable approach particularly relevant for resource-limited settings or geographically dispersed populations.

While a formal cost-effectiveness analysis was beyond the scope of this study, the implementation of the case management model required additional resources, including 1.2 full-time equivalent (FTE) nurses and weekly multidisciplinary team meetings. However, these programmatic costs were partially offset by a 0.8-day reduction in the average intensive care unit (ICU) stay and fewer unplanned readmissions (2 in OG vs 7 in CG), suggesting a potential for net cost savings. Future implementation trials should be designed to formally evaluate the economic impact alongside clinical outcomes.

This study has several important limitations that should be considered when interpreting the findings.

First, regarding generalizability: the single-center design and recruitment from a tertiary hospital limit applicability to community settings or regions with differing healthcare resources. The strict inclusion criteria (requiring good communication skills and low rehabilitation risk) resulted in a relatively “idealized” patient population with lower comorbidity burden than that found in typical clinical practice. Consequently, our findings may not generalize to higher-risk patients with cognitive impairment, limited social support, or more severe comorbidities, who may represent a substantial proportion of elderly diabetic CABG patients in real-world settings.

Second, regarding selection bias: while randomization minimized allocation bias, the use of convenience sampling may have introduced selection bias, potentially excluding sicker patients or those with socioeconomic barriers.

Third, regarding unmeasured confounders: despite adjusting for key variables, residual confounding by factors such as long-term medication adherence, specific dietary habits, or socioeconomic status may persist.

Fourth, regarding temporal constraints: the 6-month follow-up period was sufficient to demonstrate significant changes in cardiac function and metabolic markers, but it precluded the assessment of long-term outcomes such as graft patency, cardiovascular mortality, or the sustainability of the intervention’s effects.

Fifth, regarding methodological trade-offs: blinding of patients and nursing staff to the case management intervention was impractical and was not performed, which could have introduced performance bias. Patients aware of receiving enhanced care may have been more motivated to adhere to lifestyle recommendations, and providers may have delivered care with greater enthusiasm. Although all outcome assessors were masked and objective measures (echocardiography, laboratory values) were used for primary endpoints, patient-reported outcomes (DSQL, ADL) may be particularly susceptible to this bias.

Sixth, regarding the infection endpoint: the 0% infection rate, while a positive outcome, reflects strict CDC/NHSN criteria and a selected low-risk population, and may not be generalizable to centers with higher baseline infection risks or less stringent definitions.

Despite these limitations, the strong, clinically meaningful effect sizes observed (Cohen’s d range: 0.61–1.12) provide robust justification for future multicenter studies with extended follow-up, broader eligibility criteria, and embedded cost-effectiveness analyses.

Conclusions

This randomized controlled trial demonstrated that a structured, multidisciplinary case management model centered on cardiac rehabilitation significantly improved cardiac function (LVEF increased by 6.2%), glycemic control (HbA1c reduced by 1.3%), lipid profiles, functional capacity, and quality of life in elderly diabetic patients following off-pump CABG. These findings support the integration of comprehensive case management into perioperative care for this high-risk population. However, given the single-center design and selection of lower-risk patients, future multicenter trials with broader eligibility criteria are needed to confirm generalizability and assess long-term outcomes including cardiovascular mortality and graft patency.