Coronary artery bypass grafting (CABG) remains an important revascularization strategy for patients with complex multivessel coronary artery disease, left main disease, diabetes, or anatomy in which surgery is expected to provide durable myocardial perfusion. The long-term effectiveness of CABG depends in part on the durability of the conduits used to bypass diseased coronary segments. The left internal thoracic artery is established as the preferred conduit for the left anterior descending artery, while a second conduit is commonly required for other significantly stenosed vessels. The saphenous vein has been widely used because it is readily available, can provide adequate length, and is familiar to surgical teams. However, vein grafts are exposed to arterial pressure and may develop intimal hyperplasia and accelerated atherosclerosis, leading to stenosis or occlusion over time. The radial artery is a muscular arterial conduit with greater resistance to atherosclerotic degeneration and has therefore received renewed attention as an alternative for non-left anterior descending targets. Its use requires appropriate patient and target-vessel selection. Competitive native coronary flow may contribute to graft spasm or a string sign when stenosis is not sufficiently severe. Assessment of hand collateral circulation, preservation of radial access for potential future procedures, and avoidance in patients likely to need dialysis access are also relevant considerations. Comparative evidence has increasingly supported radial artery grafting for selected patients. A patient-level pooled analysis of randomized trials found fewer adverse cardiac events and fewer graft occlusions with radial artery than with saphenous vein grafts at approximately five years [1]. An individual-participant meta-analysis subsequently reported a lower ten-year incidence of death, myocardial infarction, or repeat revascularization with radial artery grafting [2]. The RAPCO randomized programme also reported better ten-year patency for radial artery than vein grafts in its comparison cohort, although estimates for some clinical outcomes remained imprecise [3]. Current revascularization guidance accordingly favours the radial artery for the most important significantly stenosed non-LAD target in appropriate patients [4]. Nevertheless, conduit performance in routine practice can vary with patient characteristics, coronary target stenosis, harvesting technique, graft configuration, perioperative management, and follow-up duration. Local comparative data on early recovery, perioperative complications, graft patency, and short-term cardiovascular events can help describe how the two conduits perform in a specific surgical setting. This study was designed to compare outcomes among patients undergoing CABG with a radial artery or saphenous vein graft, while accounting for baseline clinical profile and target-vessel factors. AIM To compare perioperative and 12-month outcomes in patients undergoing CABG with radial artery and saphenous vein grafts. OBJECTIVES 1. To compare baseline clinical characteristics and perioperative outcomes between patients receiving radial artery and saphenous vein grafts. 2. To compare graft patency at 12 months between the two conduit groups. 3. To compare major adverse cardiac and cerebrovascular events through 12 months after CABG.

Source of Data Data were obtained from the hospital cardiac surgery registry, inpatient case records, operative notes, laboratory and imaging records, and scheduled postoperative follow-up records for adults who underwent isolated CABG during the study period. The patient was the unit of analysis. Only the prespecified study conduit used for a non-LAD target was compared; the left internal thoracic artery was used for the LAD whenever clinically indicated and available. Study Design A hospital-based prospective comparative cohort study was described. Patients were classified according to whether a radial artery (RA) or saphenous vein graft (SVG) was used as the study conduit. Conduit allocation was determined by the operating team and clinical suitability, rather than random assignment. Follow-up was planned to 12 months. Study Location The study was conducted in the Department of Cardiovascular and Thoracic Surgery, Government Stanley Medical College and Hospital, Chennai Study Duration Recruitment was described for 18 months, from [month/year] to [month/year], with each participant followed for 12 months after surgery. Insert the actual recruitment and follow-up dates before use. Sample Size The planned total sample was 180 patients, with 90 allocated to each conduit group. For two independent proportions, the sample size equation was: Assuming 12-month patency of 0.93 for RA and 0.78 for SVG, two-sided alpha=0.05, and 80% power, the calculation required approximately 85 patients per group. Allowing 5% for incomplete follow-up gave approximately 90 per group (total N=180). These planning assumptions must be checked against local estimates and the prespecified primary endpoint. Inclusion Criteria Adults aged 18 years or older undergoing first-time, isolated CABG for coronary artery disease; receipt of an RA or SVG as a graft to a significantly stenosed non-LAD coronary target; availability of baseline clinical and operative information; and documented consent for prospective follow-up and graft assessment where applicable. Exclusion Criteria Emergency salvage CABG with incomplete baseline assessment; concomitant valve, aortic, or other major cardiac surgery; previous CABG; use of both RA and SVG as competing study conduits in the same patient when a single patient-level exposure could not be defined; prior radial artery catheterization or inadequate collateral hand circulation precluding RA harvest; advanced chronic kidney disease with anticipated haemodialysis access requirement; contraindication to follow-up imaging; or absence of the minimum outcome data. Procedure and Methodology Eligible patients were screened consecutively. A preoperative assessment included demographic details, cardiovascular risk factors, renal function, left ventricular ejection fraction, coronary angiography findings, target vessel and stenosis severity, and operative risk. For patients considered suitable for RA harvest, collateral circulation was assessed clinically with an objective test such as duplex ultrasonography or modified Allen testing according to institutional protocol. The study conduit was harvested by the operating surgeon using the unit’s standard technique. RA grafts were directed to a significantly stenosed non-LAD target, and perioperative vasodilator therapy was given according to institutional practice. SVG harvest was performed using the unit’s standard open or endoscopic approach. The choice of conduit, anastomotic configuration, cardiopulmonary bypass use, cross-clamp time, number of distal anastomoses, and intraoperative flow assessment were recorded. All patients received guideline-directed postoperative antiplatelet, lipid-lowering, and secondary-prevention treatment unless contraindicated. Clinical review was planned at discharge, 30 days, 6 months, and 12 months. Twelve-month graft imaging was obtained using coronary CT angiography or invasive angiography when clinically indicated or specified by protocol. Imaging was interpreted using a prespecified definition; graft patency was defined as uninterrupted flow without occlusion or severe graft stenosis. Events were adjudicated from medical records. Sample Processing No biological specimen was collected specifically for this conduit-comparison study. Routine blood investigations performed during standard care, including haemoglobin, serum creatinine, lipid profile, and cardiac biomarkers, were abstracted from the electronic or paper record with date and units recorded. Imaging data were stored and interpreted according to institutional radiology and cardiology procedures. Study identifiers were used on the analysis file, and direct identifiers were kept separately in a restricted linkage log. Statistical Methods Data were analysed using [name and version of statistical software]. Continuous variables were summarized as mean (standard deviation) when approximately normally distributed, or median (interquartile range) otherwise. Categorical variables were summarized as frequency and percentage. Between-group comparisons used the independent-samples t test or Mann-Whitney U test for continuous variables and chi-square or Fisher exact test for categorical variables. Mean differences or risk differences were presented with 95% confidence intervals. The primary binary outcome, 12-month graft patency, was compared using an unadjusted risk difference and logistic regression; adjusted estimates were to account for prespecified confounders such as age, sex, diabetes, renal function, ejection fraction, target vessel, degree of stenosis, and graft configuration. Time-to-event outcomes were summarized with Kaplan-Meier estimates and compared by log-rank test; Cox regression was used when event counts allowed. All tests were two-sided, with p<0.05 considered statistically significant. Missing data and loss to follow-up were reported, and no imputation was assumed in the illustrative tables. Data Collection A structured case-record form captured age, sex, body mass index, diabetes, hypertension, smoking, dyslipidaemia, chronic kidney disease, prior radial access, ejection fraction, coronary anatomy, target vessel, percent stenosis, conduit type and harvest method, operative duration, cardiopulmonary bypass and cross-clamp times, transfusion, intensive-care and hospital stay, wound complications, perioperative myocardial infarction, stroke, reoperation, 12-month graft status, death, myocardial infarction, stroke, and repeat revascularization. Data were checked against source records, coded using a study-specific dictionary, and entered into a password-protected database with range and consistency checks.

Table 1. Baseline profile of participants and target-vessel characteristics (N = 180) Characteristic Radial artery (n=90) Saphenous vein (n=90) Test statistic / effect (95% CI) p value Age, years, mean (SD) 61.8 (8.7) 62.6 (8.9) t=-0.62; MD -0.8 (-3.3 to 1.7) 0.53 Male sex, n (%) 69 (76.7) 71 (78.9) chi2=0.13; RD -2.2% (-14.4 to 10.0) 0.72 Diabetes mellitus, n (%) 38 (42.2) 41 (45.6) chi2=0.21; RD -3.3% (-17.8 to 11.1) 0.65 Hypertension, n (%) 57 (63.3) 60 (66.7) chi2=0.22; RD -3.3% (-17.1 to 10.4) 0.64 LVEF, %, mean (SD) 52.1 (9.6) 51.4 (10.1) t=0.48; MD 0.7 (-2.2 to 3.6) 0.63 Target stenosis >=90%, n (%) 75 (83.3) 72 (80.0) chi2=0.34; RD 3.3% (-9.0 to 15.7) 0.56 Circumflex territory target, n (%) 57 (63.3) 55 (61.1) chi2=0.09; RD 2.2% (-12.1 to 16.6) 0.76 In this illustrative cohort, the two groups had similar baseline distributions. Mean age was 61.8 years in the RA group and 62.6 years in the SVG group. Diabetes was present in 42.2% and 45.6%, respectively, and the majority of study targets had at least 90% stenosis. None of the displayed between-group comparisons was statistically significant. These example data suggest broad baseline comparability, but real analyses should report standardized differences and adjust for clinical selection of conduit. Table 2. Perioperative characteristics and early postoperative outcomes Outcome Radial artery (n=90) Saphenous vein (n=90) Test statistic / effect (95% CI) p value Operative time, min, mean (SD) 286 (39) 272 (36) t=2.52; MD 14 (3.1 to 24.9) 0.012 Cross-clamp time, min, mean (SD) 71.4 (18.2) 69.1 (17.5) t=0.88; MD 2.3 (-2.9 to 7.5) 0.38 ICU stay, days, median (IQR) 2 (2-3) 2 (2-3) Mann-Whitney U 0.61 Hospital stay, days, mean (SD) 8.2 (2.6) 8.5 (2.8) t=-0.74; MD -0.3 (-1.1 to 0.5) 0.46 Perioperative MI, n (%) 3 (3.3) 4 (4.4) Fisher exact; RD -1.1% (-7.2 to 5.0) 0.70 Stroke, n (%) 1 (1.1) 2 (2.2) Fisher exact; RD -1.1% (-4.9 to 2.7) 0.56 Harvest-site wound complication, n (%) 2 (2.2) 7 (7.8) chi2=2.88; RD -5.6% (-12.0 to 0.9) 0.09 In-hospital death, n (%) 1 (1.1) 2 (2.2) Fisher exact; RD -1.1% (-4.9 to 2.7) 0.56 In the illustrative results, mean operative duration was longer in the RA group by 14 minutes (95% CI 3.1 to 24.9; p=0.012). Cross-clamp time, ICU and hospital stay, perioperative myocardial infarction, stroke, wound complications, and in-hospital mortality did not differ significantly. The apparent wound-complication difference favoured RA but was imprecise and did not reach the prespecified significance threshold. Table 3. Twelve-month graft patency among participants with interpretable imaging (Objective 2) Imaging outcome Radial artery (n=80) Saphenous vein (n=78) Test statistic / effect (95% CI) p value Patent graft, n (%) 75 (93.8) 65 (83.3) chi2=4.13; RD 10.4% (0.4 to 20.5) 0.042 Graft occlusion, n (%) 5 (6.3) 13 (16.7) chi2=4.13; RD -10.4% (-20.5 to -0.4) 0.042 Severe stenosis without occlusion, n (%) 3 (3.8) 6 (7.7) Fisher exact; RD -4.0% (-11.6 to 3.7) 0.33 Imaging not available, n (%) 10 (11.1) 12 (13.3) chi2=0.21; RD -2.2% (-12.5 to 8.1) 0.65 Among participants with interpretable 12-month imaging, graft patency was 93.8% for RA and 83.3% for SVG. The illustrative absolute patency difference was 10.4 percentage points (95% CI 0.4 to 20.5; p=0.042). Occlusion was correspondingly less frequent in the RA group. Imaging was unavailable for 11.1% and 13.3%, respectively; the missing imaging must be considered when interpreting these estimates, and the actual study should state whether imaging was protocol-mandated or clinically selected. Table 4. Major adverse cardiac and cerebrovascular events through 12 months (Objective 3) Outcome Radial artery (n=90) Saphenous vein (n=90) Test statistic / effect (95% CI) p value Composite MACCE, n (%) 9 (10.0) 16 (17.8) Fisher exact; RD -7.8% (-18.4 to 2.9) 0.15 All-cause death, n (%) 4 (4.4) 6 (6.7) Fisher exact; RD -2.2% (-9.9 to 5.4) 0.51 Nonfatal MI, n (%) 3 (3.3) 6 (6.7) Fisher exact; RD -3.3% (-10.7 to 4.0) 0.31 Stroke, n (%) 2 (2.2) 3 (3.3) Fisher exact; RD -1.1% (-6.9 to 4.6) 0.65 Repeat revascularization, n (%) 3 (3.3) 7 (7.8) Fisher exact; RD -4.4% (-11.9 to 3.0) 0.20 By 12 months, the illustrative composite MACCE frequency was 10.0% in the RA group and 17.8% in the SVG group (risk difference -7.8 percentage points, 95% CI -18.4 to 2.9; p=0.15). Death, nonfatal myocardial infarction, stroke, and repeat revascularization were numerically less frequent with RA, but none of the comparisons was statistically significant. The modest sample and low event counts limit precision.

Principal findings This illustrative comparison suggests that RA grafting may be associated with higher 12-month imaging patency than SVG grafting, while major early complications and 12-month clinical events were not statistically different. The RA group had a modestly longer operative time, which is consistent with the additional steps involved in radial harvest and conduit preparation. These values are hypothetical and should not be interpreted as local clinical evidence. Baseline profile and patient selection The example groups were similar in age, sex, diabetes, hypertension, ejection fraction, target stenosis, and coronary territory. This balance is important because observational conduit selection is influenced by age, renal function, diabetes, target-vessel stenosis, prior radial access, surgeon preference, and expected survival. Neumann et al.(2019)[5] and Lawton et al.(2022)[4] emphasized matching conduit choice to patient factors and target-vessel characteristics. In a real cohort, nonsignificant p values alone would not establish balance; adjusted modelling and standardized mean differences would be needed to reduce confounding by indication. Perioperative outcomes The illustrative operative time was longer in the RA group, whereas ICU stay, hospital stay, perioperative MI, stroke, and in-hospital death were similar. Gaudino et al.(2019)[6] found no significant difference in operative mortality, perioperative MI, or stroke in their meta-analysis comparing RA and SVG as the second conduit. This supports the expectation that harvesting RA in appropriately selected patients need not increase short-term major morbidity. Nappi et al.(2021)[7] summarized practical selection, harvesting, and antispasm considerations, including assessment of hand circulation, avoidance after transradial catheterization, and attention to target stenosis. Wound outcomes can be influenced by harvesting method, diabetes, obesity, and local practice, so any observed difference should be interpreted with adjustment for these factors. Graft patency In the example data, 12-month patency was higher with RA than SVG, with an absolute difference of 10.4 percentage points. The direction is consistent with long-term randomized and pooled evidence. Gaudino et al.(2018)[1] reported a lower risk of graft occlusion with RA in a patient-level analysis of randomized trials. Gaudino et al.(2020)[2] extended this evidence and found fewer major cardiovascular events at ten years with RA. The RAPCO investigators, reported by Hayward et al.(2020)[8], estimated 10-year patency of 85% with RA compared with 71% with SVG in the randomized RA-versus-SV comparison, although the confidence interval for graft failure approached unity. Yamasaki et al.(2016)[9] reported less graft-body disease in RA than SVG more than five years after CABG, while the angiographic network meta-analysis by Gaudino et al.(2022)[10] found lower occlusion with RA than conventionally harvested SVG. These data support the biological rationale for arterial conduit durability, but patency depends strongly on severe target-vessel stenosis, absence of competitive flow, conduit handling, and completeness of follow-up imaging. Clinical events The example cohort had numerically fewer MACCE events with RA, but the confidence interval included no difference. Such a result is expected in a study of 180 patients followed for one year, where mortality and repeat revascularization are relatively infrequent. In the pooled five-year analysis, Gaudino et al.(2018)[1] observed lower composite cardiac events with RA, and the ten-year individual participant meta-analysis by Gaudino et al.(2020)[2] showed a sustained reduction in death, MI, or repeat revascularization. The 2021 ACC/AHA/SCAI guideline recommended RA over SVG for the second most important significantly stenosed non-LAD vessel in isolated CABG patients [4]. A short follow-up study cannot confirm or refute these longer-term benefits; adequately powered follow-up with time-to-event methods is required. Clinical implications and limitations of comparison The available evidence supports considering RA as a second conduit in suitable patients, particularly when the non-LAD target has severe stenosis and the patient has adequate renal function and collateral hand circulation. The vein remains useful when RA is unavailable, unsuitable, previously instrumented, or when clinical and technical circumstances favour its use. Studies evaluating RA against SVG should report which conduit supplied the LAD, the target vessel and stenosis, harvest approach, graft configuration, antispasm therapy, secondary prevention, imaging modality, and attrition. The example study would be limited by nonrandom allocation, single-centre practice, possible selection bias, missing follow-up imaging, and too few clinical events for robust adjusted analyses. Twelve-month patency is also a surrogate for long-term clinical durability.

In this illustrative 180-patient comparison, radial artery grafting was associated with higher 12-month graft patency than saphenous vein grafting, while perioperative major complications and 12-month MACCE did not differ significantly. RA grafting required a modestly longer operative time. These example findings are consistent with evidence favouring RA for selected non-LAD targets, but they are not real patient results and must be replaced and recalculated using the verified study dataset before any conclusion is reported as observed evidence. LIMITATIONS • The numerical results in this draft are illustrative and cannot be used as clinical findings or submitted as study data. • If implemented as a nonrandomized cohort, conduit choice may be confounded by patient condition, coronary anatomy, surgeon preference, and suitability for radial harvest. • A single-centre sample of 180 patients would have limited power to detect differences in mortality and other uncommon cardiovascular events. • If follow-up imaging is incomplete or clinically directed, estimates of graft patency may be affected by missing-data and verification bias. • Twelve months is insufficient to characterize late graft failure, vein-graft atherosclerosis, or long-term survival differences. • Conduit harvest technique, graft configuration, target stenosis, use of vasodilators, and post-discharge medical therapy may vary and influence outcomes. • Residual confounding and loss to follow-up may remain despite multivariable adjustment.

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