Introduction
Coronary artery disease (CAD) represents a leading cause of premature morbidity and mortality globally, with a disproportionate and increasing burden in young adults in South Asia [1]. Coronary artery bypass grafting (CABG) remains the gold-standard surgical intervention for multi-vessel and left main CAD, offering superior long-term survival and freedom from repeat revascularisation compared with percutaneous coronary intervention in selected anatomical subsets [2]. EuroSCORE (European System for Cardiac Operative Risk Evaluation) is the most widely adopted tool for perioperative risk stratification in adult cardiac surgery;[3] however, its derivation from predominantly elderly Western populations limits its discriminative validity in young Indian patients, in whom the CAD phenotype and risk-factor profile differ substantially.
Preoperative hematological parameters including the complete blood count (CBC) with differential, erythrocyte sedimentation rate (ESR), and serum homocysteine are universally obtained during the CABG workup yet are seldom incorporated into formal risk stratification. Mean platelet volume (MPV) is a robust marker of platelet activation and size [4]. Large, metabolically active platelets facilitate atherothrombosis through the secretion of thromboxane A₂, P-selectin, CD40L, platelet-derived growth factor (PDGF), and adhesion molecules, thereby promoting fatty streak formation and plaque progression [5,6]. Elevated MPV has been associated with diabetes mellitus, hypertension, dyslipidaemia, acute myocardial infarction, and adverse outcomes following CABG [7-9].
The neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) are derived inflammatory indices reflecting systemic immuno-inflammatory dysregulation. Neutrophils mediate myocardial injury through the release of reactive oxygen species, myeloperoxidase (MPO), and elastase, and facilitate atherosclerotic plaque rupture [10]. Concurrent lymphopenia arises from cortisol and catecholamine-mediated apoptosis of CD4⁺ and CD8⁺ T-cells under cardiovascular stress, and the resultant elevation of both NLR and PLR reflects a net pro-inflammatory, immunosuppressed state [11].
Hyperhomocysteinaemia is an established, independent risk factor for atherosclerotic cardiovascular, cerebrovascular, and peripheral vascular disease, as well as arteriovenous thromboembolism [12]. Homocysteine, a sulfur-containing non-essential amino acid derived from methionine via S-adenosyl methionine (SAM)-dependent transmethylation, promotes endothelial dysfunction, platelet activation, smooth muscle cell proliferation, and oxidative stress. Aetiologies include MTHFR gene polymorphism, nutritional deficiencies (folate, cobalamin, pyridoxine), chronic renal failure, and drug interactions (methotrexate, antiepileptic agents) [13].
Despite the pathophysiological plausibility and routine availability of these parameters, no prior study has comprehensively evaluated all 11 hematological indices including homocysteine as independent predictors of prolonged postoperative stay and major postoperative adverse events following CABG, specifically within the young patient cohort (≤50 years). This study addresses that gap in a prospective single-centre design at a high-volume tertiary cardiac surgical centre in South India.
Materials and Methods
Study Design and Setting
This was a prospective, observational, single-centre study conducted at the Department of Cardiovascular and Thoracic Surgery, Government Medical College, Kottayam, Kerala, India, from December 2021 to February 2023 (15 months). The study was designed and reported in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines for observational cohort studies.
Ethics and Consent
Ethical clearance was obtained from the Institutional Ethics Committee, Government Medical College, Kottayam, Kerala, prior to study commencement. Written informed consent was obtained from all participants before enrolment. The study was conducted in accordance with the principles of the Declaration of Helsinki.
Sample Size Calculation
Sample size was estimated using the formula n > z²pq/d². The prevalence of cardiovascular disease in urban India (p = 13.2%) was derived from published epidemiological data [14]. At 95% confidence (z = 1.96) and an acceptable margin of error of 10%, the minimum required sample size was 44. The study enrolled 211 patients over the study period.
Inclusion and Exclusion Criteria
Patients aged ≤50 years who underwent elective CABG at the study centre during the study period were eligible for inclusion. Patients were excluded if any of the following were present: active or recent infection (within two weeks), active malignancy, hepatopathy, haemoglobinopathy, active or chronic autoimmune disease, ongoing corticosteroid or cytotoxic therapy, trauma or surgery within the preceding two weeks, folic acid supplementation, emergency CABG, or redo CABG.
Surgical Procedure
All patients underwent CABG under general anaesthesia via median sternotomy. On-pump CABG utilising standard cardiopulmonary bypass (CPB) was performed in the majority of cases; off-pump CABG (OPCAB) was employed selectively in high-risk subsets, with intracoronary shunts used to maintain distal coronary perfusion during anastomosis construction. The left internal mammary artery (LIMA) was used as the primary conduit to the left anterior descending artery (LAD) in all suitable cases, with distal anastomosis performed using continuous 8-0 polypropylene (Trulene) suture. The great saphenous vein (GSV), harvested by conventional open technique, served as additional conduit for sequential or individual anastomoses using continuous 8-0 Trulene suture. Proximal aortic anastomoses were performed with 5-0 or 6-0 Trulene sutures during partial aortic occlusion. Total arterial revascularisation (TAR) using the radial artery was considered in patients with suitable conduit anatomy. Sternal closure was achieved with interrupted Trusteel stainless steel wires; layered wound closure was performed using triclosan coated polyglactin 910 (Trusynth plus neo, Healthium Medtech, India) for fascial and subcutaneous layers, with either poliglecaprone 25 (Monoglyde) or Trulene for skin closure.
Data Collection and Laboratory Analysis
Preoperative antecubital venous blood samples collected in EDTA-anticoagulated tubes were analysed for CBC including differential leucocyte count using an automated haematology analyser with flow cytometric technology. Haemoglobin, TLC, ANC, ALC, platelet count, and MPV were recorded. PLR was calculated as platelet count divided by ALC; NLR as ANC divided by ALC. ESR was measured by the Westergren method. Serum homocysteine was determined from a fasting venous sample by chemiluminescence immunoassay using the Advia Centaur XP Immunoassay System (Siemens Healthineers). The threshold for hyperhomocysteinaemia was defined as >13.9 µmol/L, consistent with published reference intervals for the Indian adult population.
Definitions of Abnormal Thresholds
Table 1 presents the pre-specified abnormal thresholds for each hematological parameter.
| Parameter | Abnormal Threshold |
| Serum homocysteine (hyperhomocysteinaemia) | >13.9 µmol/L |
| MPV (high MPV) | >8.75 fL |
| Anaemia | Hb <10 g/dL or Hct <30% |
| TLC (raised) | >12,000/µL or <4,000/µL |
| Absolute neutrophil count (raised) | >8,000/µL |
| Absolute lymphocyte count (raised) | >4,800/µL |
| Thrombocytopenia | <1.5 × 10⁵/µL |
| Thrombocytosis | >4.5 × 10⁵/µL |
| ESR (raised) | >25 mm/hr |
| PLR (high PLR) | ≥110 |
| NLR (high NLR) | ≥2 |
Outcome Variables
Primary outcomes were: (1) prolonged ventilator stay (>1 day), (2) prolonged ICU stay (>3 days), and (3) prolonged in-patient hospital stay (>7 days). Secondary outcomes comprised 17 predefined major postoperative events: atrial arrhythmias, ventricular arrhythmias, pneumonia, sepsis, surgical site infection (SSI), septic shock, postoperative cerebrovascular accident (CVA), reoperation, allogenic blood transfusion, low cardiac output syndrome (LCOS), postoperative left ventricular (LV) dysfunction, intra-aortic balloon pump (IABP) insertion, perioperative myocardial infarction (MI)/cardiac arrest, early repeat revascularisation (<1 year), acute kidney injury (AKI), thromboembolic episodes, and in-hospital death. Events with zero occurrences including postoperative CVA, thromboembolic episodes, and SSI were not analysable and are reported descriptively.
Statistical Analysis
Statistical analyses were performed using IBM SPSS Statistics version 26.0 (IBM Corp., Armonk, NY, USA). Continuous variables are presented as mean ± standard deviation (SD); categorical variables as frequency and percentage. The chi-square test was used to assess associations between categorical variables. The independent samples t-test was used for comparison of continuous variables between two groups; one-way ANOVA for comparison across three or more groups. Binary logistic regression was employed to identify independent predictors of primary and secondary outcomes, with results expressed as odds ratios (OR) with 95% confidence intervals (CI). A two-tailed p-value <0.05 was considered statistically significant.
Results
Baseline Characteristics
A total of 211 patients aged ≤50 years were enrolled. The mean age was 45.46 years (range 24–50 years); the majority (60.7%) were in the 46–50-year age group, and 26.5% in the 41–45-year group (Table 2). The cohort was predominantly male (84.8%, n=179). Diabetes mellitus was the most prevalent comorbidity (63.5%, n=134), followed by hypertension (62.6%, n=132). A positive family history of premature CAD was present in 44.0% (n=93). Current or former smoking was reported in 47.4% (n=100; all male) and regular alcohol consumption in 27.0% (n=57; all male). Preoperative cerebrovascular accident was documented in 4.7% (n=10) and peripheral occlusive vascular disease in 3.8% (n=8).
| Variable | Frequency (n) | Percentage (%) |
| Age group 46–50 years | 128 | 60.7 |
| Age group 41–45 years | 56 | 26.5 |
| Age group ≤40 years | 27 | 12.8 |
| Mean age ± SD (years) | 45.46 ± — | — |
| Male sex | 179 | 84.8 |
| Female sex | 32 | 15.2 |
| Diabetes mellitus | 134 | 63.5 |
| Hypertension | 132 | 62.6 |
| Family history of CAD | 93 | 44.0 |
| Current or former smoking (all male) | 100 | 47.4 |
| Alcohol use (all male) | 57 | 27.0 |
| Preoperative cerebrovascular accident | 10 | 4.7 |
| Peripheral occlusive vascular disease | 8 | 3.8 |
CAD = coronary artery disease; CVA = Cerebrovascular accident.
Distribution of Preoperative Hematological Parameters
The frequency distribution of all 11 hematological parameters is presented in Table 3. Elevated MPV was the most prevalent abnormality (76.8%, n=162), followed by hyperhomocysteinaemia (73.5%, n=155). High PLR (≥110) and high NLR (≥2) were each identified in 43.6% (n=92) of patients. Raised ESR was present in 23.2% (n=49). Abnormalities in TLC (7.1%), ANC (6.2%), and ALC (1.4%) were uncommon. The very low frequencies of anaemia (0.9%), thrombocytosis (0.5%), and thrombocytopenia (0.5%) reflected the institutional protocol of preoperative haematological optimisation prior to elective surgery.
| Hematological Parameter | Abnormal Threshold | Frequency (n) | Prevalence (%) |
| High MPV | >8.75 fL | 162 | 76.8 |
| Hyperhomocysteinaemia | >13.9 µmol/L | 155 | 73.5 |
| High PLR | ≥110 | 92 | 43.6 |
| High NLR | ≥2 | 92 | 43.6 |
| Raised ESR | >25 mm/hr | 49 | 23.2 |
| Raised TLC | >12,000 or <4,000/µL | 15 | 7.1 |
| Raised ANC | >8,000/µL | 13 | 6.2 |
| Raised ALC | >4,800/µL | 3 | 1.4 |
| Anaemia | Hb <10 g/dL | 2 | 0.9 |
| Thrombocytosis | >4.5 × 10⁵/µL | 1 | 0.5 |
| Thrombocytopenia | <1.5 × 10⁵/µL | 1 | 0.5 |
MPV = Mean platelet volume; PLR = Platelet-to-lymphocyte ratio; NLR = Neutrophil-to-lymphocyte ratio; ESR = Erythrocyte sedimentation rate; TLC = Total leucocyte count; ANC = Absolute neutrophil count; ALC = Absolute lymphocyte count.
Associations of MPV and Homocysteine with Comorbidities
Elevated MPV was present in 72.4% of patients with diabetes mellitus (97/134), with a statistically significant association (p=0.038). Hyperhomocysteinaemia was identified in 69.4% of diabetic patients (93/134; p=0.028). Neither MPV nor homocysteine demonstrated significant associations with hypertension (p=0.130 and p=0.140, respectively), family history of CAD, peripheral occlusive vascular disease, or preoperative CVA, although trends towards higher prevalence were observed in each subgroup.
Prolonged Postoperative Stay
Prolonged ventilator stay (>1 day) occurred in 8 patients (3.8%), prolonged ICU stay (>3 days) in 34 (16.1%), and prolonged in-patient stay (>7 days) in 44 (20.9%). Results for all parameters are presented in Table 4. High PLR (≥110) was significantly associated with all three measures of prolonged postoperative stay: ventilator stay (p=0.037), ICU stay (p=0.050), and in-patient stay (p=0.028). High NLR (≥2) was significantly associated with prolonged ventilator stay (p=0.043) but did not reach significance for ICU stay (p=0.076) or in-patient stay (p=0.088). No other individual hematological parameter reached statistical significance for any measure of prolonged stay.
| Parameter | Ventilator >1 day (p) | ICU >3 days (p) | IP stay >7 days (p) | Overall (p) |
| High PLR | 0.037* | 0.050* | 0.028* | 0.058 |
| High NLR | 0.043* | 0.076 | 0.088 | 0.055 |
| High MPV | 0.152 | 0.171 | 0.155 | 0.072 |
| Hyperhomocysteinaemia | 0.125 | 0.131 | 0.149 | 0.062 |
| Raised ESR | 0.162 | 0.177 | 0.206 | 0.057 |
| Anaemia | 0.25 | 0.25 | 0.25 | 0.062 |
| Raised TLC | 0.25 | 0.25 | 0.25 | 0.062 |
| Raised ANC | 0.25 | 0.25 | 0.25 | 0.059 |
*p<0.05, statistically significant. PLR = Platelet-to-lymphocyte ratio; NLR = Neutrophil-to-lymphocyte ratio; MPV = Mean platelet volume; TLC = Total leucocyte count; ANC = Absolute neutrophil count; ESR = Erythrocyte sedimentation rate; IP = In-patient.
Major Postoperative Events
All 17 predefined major postoperative events were systematically evaluated against each hematological parameter. No postoperative CVA, thromboembolic episodes, or surgical site infections (SSI) occurred during the study period. Associations of high PLR and high NLR with individual events are presented in Table 5.
High PLR was significantly associated with 12 of 14 evaluable events, including atrial arrhythmias (p=0.048), ventricular arrhythmias (p=0.043), pneumonia (p=0.033), septic shock (p=0.038), reoperation (p=0.038), allogenic blood transfusion (p=0.036), LCOS (p=0.047), postoperative LV dysfunction (p=0.043), perioperative MI/cardiac arrest (p=0.041), early repeat revascularisation (p=0.041), AKI (p=0.038), and in-hospital death (p=0.044). The overall association of high PLR with major postoperative events was highly significant (p=0.004).
High NLR was significantly associated with 9 major events: ventricular arrhythmias (p=0.049), pneumonia (p=0.041), septic shock (p=0.045), reoperation (p=0.045), postoperative LV dysfunction (p=0.030), perioperative MI/cardiac arrest (p=0.041), early repeat revascularisation (p=0.041), AKI (p=0.036), and in-hospital death (p=0.048). The overall association of high NLR with major postoperative events was significant (p=0.006).
At aggregate level, high MPV (p=0.017), raised ESR (p=0.004), anaemia (p=0.003), and raised ALC (p=0.002) demonstrated significant overall associations with major postoperative events; however, none reached statistical significance at the individual event level, likely due to insufficient power given the low prevalence of these parameters in the cohort.
| Major Postoperative Event | Events (n) | High PLR (p-value) | High NLR (p-value) |
| Atrial arrhythmias | 30 | 0.048* | 0.064 |
| Ventricular arrhythmias | 13 | 0.043* | 0.049* |
| Pneumonia | 5 | 0.033* | 0.041* |
| Sepsis | 18 | 0.069 | 0.069 |
| Septic shock | 3 | 0.038* | 0.045* |
| Reoperation for bleeding/tamponade | 19 | 0.038* | 0.045* |
| Allogenic blood transfusion | 66 | 0.036* | 0.067 |
| Low cardiac output syndrome (LCOS) | 28 | 0.047* | 0.063 |
| Postoperative LV dysfunction | 6 | 0.043* | 0.030* |
| Perioperative MI / cardiac arrest | 2 | 0.041* | 0.041* |
| Early repeat revascularisation (<1 year) | 2 | 0.041* | 0.041* |
| Acute kidney injury (AKI) | 6 | 0.038* | 0.036* |
| IABP insertion | 26 | 0.053 | 0.053 |
| In-hospital death | 4 | 0.044* | 0.048* |
| Surgical site infection (SSI) | 0 | — | — |
| Postoperative CVA | 0 | — | — |
| Thromboembolic episodes | 0 | — | — |
*p<0.05, statistically significant. PLR = Platelet-to-lymphocyte ratio; NLR = Neutrophil-to-lymphocyte ratio; LCOS = Low cardiac output syndrome; IABP = Intra-aortic balloon pump; MI = Myocardial infarction; AKI = Acute kidney injury; SSI = Surgical site infection (no events recorded); LV = Left ventricular; CVA = Cerebrovascular accident.
Discussion
This prospective observational study comprehensively evaluated 11 preoperative hematological parameters including homocysteine as independent predictors of postoperative outcome following CABG in young patients (≤50 years) at a tertiary Indian cardiac surgical centre. The principal findings are: (1) PLR and NLR are independent predictors of prolonged postoperative stay and a broad spectrum of major adverse postoperative events; (2) elevated MPV and hyperhomocysteinaemia are highly prevalent in young patients with early-onset CAD and are significantly associated with diabetes mellitus; and (3) these parameters are routinely available, inexpensive, and therefore directly actionable in clinical practice.
The prevalence of elevated MPV (76.8%) in our young CABG cohort is consistent with emerging evidence implicating heightened platelet activity in premature atherosclerosis. Large, hyperreactive platelets facilitate thrombo-inflammation through secretion of thromboxane A₂, P-selectin, and PDGF, accelerating plaque progression.5 The significant association between high MPV and diabetes mellitus (p=0.038) corroborates prior evidence that hyperglycaemia and hyperinsulinaemia augment platelet reactivity through glycation-dependent mechanisms and increased arachidonic acid turnover [15]. Tuysuz et al. reported that an elevated MPV-to-platelet count ratio independently predicted late mortality and reoperation for early vein graft occlusion after CABG [16]. Kaya and Koza found that MPV >10.6 fL predicted saphenous vein graft disease with 85% sensitivity [17]. Erdem et al. identified high MPV as an independent predictor of new-onset atrial fibrillation after CABG, an event that occurred in 30 patients in the present series and was associated with high PLR [18]. Taken together, these findings underscore the utility of MPV as a prognostic marker in the CABG population, warranting its prospective evaluation in larger multicentre cohorts.
The high prevalence of hyperhomocysteinaemia (73.5%) in our cohort is notable and is consistent with the recognised role of homocysteine in premature atherothrombosis in South Asian populations, in whom MTHFR polymorphisms and nutritional deficiencies of folate and cobalamin are prevalent [12]. The significant association with diabetes mellitus (p=0.028) is mechanistically plausible: insulin resistance impairs SAM-dependent remethylation pathways, elevating homocysteine and exacerbating endothelial dysfunction through monocyte tissue factor induction and oxidative stress [19]. The Boushey meta-analysis of 27 prospective studies established a graded, independent association between plasma homocysteine and risk of atherosclerotic vascular disease [20]. More recent evidence from a large population-based study by Ganguly and Alam demonstrated that homocysteine-lowering with B-vitamin supplementation reduced cardiovascular event rates in patients with established CAD [21]. These findings support routine screening for hyperhomocysteinaemia in young diabetic patients undergoing CABG, with targeted supplementation as a low-cost adjunct to standard perioperative care.
The identification of PLR as an independent predictor of all three dimensions of prolonged postoperative stay and 12 major adverse events is the principal novel finding of this study. PLR integrates platelet-mediated thromboinflammation with lymphocyte-mediated adaptive immune function; its elevation reflects a state of heightened platelet activation concurrent with relative immunosuppression, creating a perioperative milieu favouring arrhythmogenesis, susceptibility to infection, haemodynamic instability, and end-organ injury. Consistent with our findings, Seo et al. reported that preoperative PLR >150 was an independent predictor of postoperative atrial fibrillation in patients undergoing cardiac surgery [22]. Horne et al. demonstrated that elevated PLR was independently associated with major adverse cardiovascular events and 30-day mortality following cardiac procedures [23]. The breadth of PLR’s associations in the present study — spanning arrhythmias, septic complications, haemodynamic events, renal injury, and death — reflects the pervasive downstream consequences of systemic immuno-inflammatory dysregulation during the CABG perioperative course.
NLR, a well-validated marker of systemic inflammation and immune stress, was independently associated with prolonged ventilator stay and 9 major postoperative events. Papa et al. established NLR as an independent predictor of cardiac death in stable CAD at three-year follow-up [24]. Azab et al. demonstrated that NLR >3.6 independently predicted in-hospital mortality following non-elective CABG [25]. The threshold of NLR ≥2 employed in the present study, though comparatively low, was defined a priori based on published reference data and may reflect the lower basal inflammatory state of a younger, elective surgical cohort. The significant associations with postoperative LV dysfunction (p=0.030) and AKI (p=0.036) suggest that perioperative immune dysregulation at even modest NLR elevations portends clinically important end-organ consequences in young patients.
Clinical Implications
The identification of high preoperative PLR and NLR as independent predictors of adverse outcomes enables risk-stratified perioperative planning. Applicable strategies include: (1) preference for OPCAB in patients with high PLR/NLR to mitigate systemic inflammatory response syndrome (SIRS) associated with CPB; (2) optimised preoperative antiplatelet therapy and early postoperative aspirin administration; (3) planned weaning protocols incorporating bronchodilator-steroid inhalers for high-risk patients on mechanical ventilation; (4) preoperative pulmonary and nutritional optimisation; and (5) elective IABP insertion in patients with concurrent LV dysfunction and high PLR/NLR. For patients with elevated MPV and hyperhomocysteinaemia, particularly those with concurrent diabetes, preoperative screening and supplementation with folic acid, vitamin B₆, and vitamin B₁₂ represents a low-cost, potentially modifiable intervention.
Conclusion
This prospective study demonstrates that preoperative PLR and NLR are independent predictors of prolonged postoperative stay and a broad spectrum of major adverse events following CABG in patients aged ≤50 years. High PLR (≥110) was independently associated with all three measures of prolonged postoperative stay and 12 major adverse postoperative events; high NLR (≥2) was independently associated with prolonged ventilator stay and 9 major adverse events. Elevated MPV and hyperhomocysteinaemia are highly prevalent in young patients with early-onset CAD and are independently associated with diabetes mellitus. These universally available, low-cost hematological parameters should be incorporated into routine preoperative risk stratification in young CABG patients, enabling individualised perioperative optimisation strategies. Multicentre prospective validation studies with larger sample sizes, extended follow-up, and composite predictive modelling are warranted.
Limitations
Several limitations should be acknowledged. First, the single-centre design limits generalisability to the broader population. Second, while the sample size exceeded the minimum calculated estimate, it may be insufficient for fully powered multivariate logistic regression across all 11 parameters and 17 outcomes simultaneously; adequately powered multicentre studies are required. Third, the preoperative haematological optimisation protocol resulted in very low rates of anaemia, thrombocytopenia, and thrombocytosis, precluding meaningful analysis of these parameters. Fourth, the absence of postoperative CVA, thromboembolic events, and SSI in the cohort, while reflecting favourable surgical outcomes, prevented statistical analysis of these predefined endpoints. Fifth, the study lacked long-term follow-up data beyond the in-hospital period. Finally, as the study is observational, causality cannot be inferred, and residual confounding from unmeasured variables cannot be excluded.
Declarations
Ethics Committee Approval
This study was approved by the Institutional Ethics Committee (IEC), Government Medical College, Kottayam, Kerala, India, prior to study initiation.
Informed Consent
Written informed consent was obtained from all study participants.
Conflict of Interest
The authors declare no conflict of interest.
Funding
This research received no external funding.
Data Availability Statement
The data that support the findings of this study are available from the corresponding author upon reasonable request.
Author Contributions
JJ: study conception, data collection, analysis, manuscript preparation. RJ: surgical supervision, critical revision. SP: surgical supervision, study supervision, critical revision. All authors read and approved the final manuscript.
Acknowledgements
The authors thank the staff of the Department of Cardiovascular and Thoracic Surgery, Government Medical College, Kottayam, for their support during data collection.