Introduction
Coronary artery bypass grafting (CABG) is a surgical intervention aimed at improving myocardial blood flow in patients with coronary artery disease. This procedure involves the use of the arteries or veins of the patient as grafts to reroute blood around coronary arteries that are either partially or completely obstructed due to the buildup of atherosclerotic plaques. The grafts are surgically connected to bypass the areas of blockage, thereby restoring adequate perfusion to the affected myocardial tissue and alleviating symptoms (1). This procedure remains one of the most frequently performed major surgical procedures, which is typically carried out at a rate of 44 procedures per 100,000 individuals (2). However, over the past 10 years, there has been a notable reduction in the number of CABG procedures, with a decrease of ~30%. This may be attributed to advancements in alternative treatments, such as percutaneous coronary interventions, as well as improvements in medical management and preventive care for coronary artery disease. Despite this trend, CABG continues to be a critical option for patients with severe coronary artery obstruction where other treatment methods may be less effective (1).
In CABG surgery, the heart is deliberately halted to allow for accurate grafting. This is achieved by blocking the ascending aorta and introducing a cold, potassium-rich solution to stop the activity of the heart. To compensate for the lack of natural circulation, a cardiopulmonary bypass machine is utilized, ensuring oxygenation and blood flow during the period of cardiac arrest, typically lasting 1 to 2 h (1).
In CABG, grafts are primarily sourced from either arteries or veins. Arterial grafts are commonly harvested from the internal mammary artery, radial artery, or right gastroepiploic artery, while vein grafts are typically taken from the lower extremities, such as the great saphenous veins. The internal mammary artery provides excellent long-term patency rates of >90% and resistance to atherosclerosis. The radial artery is a strong alternative, with improved patency than venous grafts, particularly for high-grade stenosis. Saphenous vein grafts (SVGs), although less durable, remain common due to ease of harvest and versatility, despite a progressive failure rate. Conduit selection should be personalized, considering patient factors, vessel quality and stenosis severity, with modern approaches using tools such as fractional flow reserve for optimal graft performance (3-5).
The present study aimed to evaluate the patency of different types of grafts in CABG and identify factors influencing graft failure, such as cross-clamp time (CXT), number of grafts, comorbidities and surgical techniques.
Discussion
The success of CABG in improving patient outcomes is fundamentally linked to the sustained patency of grafts. Despite this critical role, contemporary clinical practice seldom incorporates routine, systematic evaluations of graft integrity. The majority of existing data on the long-term viability of CABG grafts originates from studies conducted several decades ago, which may not accurately reflect advancements in surgical techniques and postoperative care. Moreover, much of the currently available evidence is drawn from patient cohorts undergoing imaging due to symptomatic concerns, introducing a potential selection bias that limits the generalizability of findings (7). In the present study, all patients were assessed for graft patency at the 1 and 3-year follow-up periods.
The underlying mechanisms driving graft failure are influenced by both the type of graft utilized and the temporal phase following CABG. In the early post-operative period, within the first month, graft occlusion is primarily attributed to acute thrombosis, a process that antithrombotic therapy aims to mitigate. While both arterial and venous grafts are susceptible to thrombotic occlusion, the incidence is notably higher in venous grafts. Beyond the initial post-operative month, venous graft failure is predominantly driven by pathological processes such as intimal hyperplasia and the rapid progression of atherosclerosis, which compromise long-term graft patency (4).
Among the various factors contributing to vein graft failure following CABG, smoking and dyslipidemia have been identified as the predominant atherosclerotic risk determinants. Smoking, in particular, serves as an independent predictor of both mortality and the necessity for repeat revascularization in patients who have undergone venous graft procedures. Consequently, post-CABG smoking cessation is of paramount importance, particularly in cases where vein grafts have been employed. Similarly, elevated cholesterol and triglyceride levels are strongly implicated in the pathogenesis of vein graft disease, ultimately leading to graft failure. Furthermore, substantial evidence underscores a robust association between persistently high cholesterol levels and increased long-term mortality following coronary surgery. As a result, the rigorous management of dyslipidemia should be a fundamental component of post-operative care to optimize long-term clinical outcomes (7). In line with this, in the present study, almost half of the patients were smokers and had dyslipidemia, with hypertension being present in up to 80% of the cases highlighting their major role for patients that undergo CABG. In addition, DM was found to significantly affect the number of grafts required, as more than half of the patients who required five grafts were diabetic, while none of the patients who required three grafts had diabetes.
Furthermore, the present study demonstrated that graft patency varied depending on the specific conduit used and its connection to the coronary artery. The LIMA exhibited patency rates of 90% at 3 years . However, In the present study, SVG patency was 88.9% at 1 year for SVG to PDA grafts and 84.1% at 3 years for SVG to OM grafts; notably, SVG anastomosed to PDA and OM arteries demonstrated a higher rate of graft failure with total occlusion reaching 9.1% at the 3 years follow-up; furthermore, graft failure predominantly occurred at the distal anastomosis site in LIMA grafts, all occlusions occurred in the distal segment. In addition, in SVGs, the majority of occlusions were also observed in the distal portion. This finding is likely due to reduced flow velocity and increased turbulence at the distal anastomosis, promoting thrombosis and intimal hyperplasia, particularly in smaller recipient vessels. The relatively small sample size from a single center limits the statistical power of subgroups; thus, larger multicenter studies are required to confirm the observation and provide a more thorough observation and identification of predictors of graft failure following CABG. Another limitation of the present study was the absence of multivariable regression analysis to adjust for potential cofounding factors, such as age, hypertension and other cardiovascular risk variables, although multivariable analysis can help identify independent predictors of graft failure. The relatively small size sample and the limited number of graft failure even observed during follow-up may have resulted in model instability and overfitting. Therefore, the present study was restricted to univariable comparison. Future studies with larger sample sizes and multicenter cohorts are warranted to perform more robust multivariable analysis to better identify independent predictors of graft patency following CABG.
Graft failure represents a critical clinical challenge, often resulting in a cascade of adverse outcomes. These may include the development of myocardial ischemia, persistent angina that resists medical management, life-threatening arrhythmias, compromised cardiac output, and, in severe cases, fatal heart failure. The failure of coronary grafts can, therefore, undermine the therapeutic benefits of CABG, leading to a decline in patient prognosis and an increased risk of morbidity and mortality (8). LIMA to LAD graft patency did not exhibit a statistically significant association (P=0.050), although a trend toward improved patency was observed with shorter cross-clamp durations. Furthermore, the study by Gaudino et al (9) demonstrated that graft patency on imaging may not indicate the clinical status of the patient. In the event that the patient is asymptomatic and has an occlusion of a graft, it may not necessarily indicate urgent surgical intervention (9).
In the present study, all SVGs were harvested using the open no-touch technique, which is routine practice at our center Ibn Al-Bitar Specialized Center for Cardiac Surgery, Baghdad, Iraq; therefore, a direct comparison with alternative harvesting techniques, such as endoscopic vein harvesting was not possible. In line with the SVG harvesting technique used herein, the study by Kim et al (10) utilized the no-touch technique SVG for aortocoronary grafts, which yielded favorable graft patency rates up to the 3-year follow-up period. The 2018 guidelines from the European Society of Cardiology (ESC) and the European Association for Cardio-Thoracic Surgery (EACTS) on myocardial revascularization endorsed the ‘no-touch’ technique as a Class IIa recommendation with a level of evidence B, specifically when an open harvesting method is employed (8,11). Souza et al (12) demonstrated that ‘no-touch’ SVG exhibited significantly superior conduit patency at 18 months, a finding that was consistently validated over extended follow-up periods of 8 and 16 years. Notably, the patency of ‘no-touch’ SVG was found to rival that of the LIMA (12,13). Another harvesting technique explored in the clinical trial by Zenati et al (14) was the endoscopic approach for SVG, compared to the traditional open harvesting method. Their study revealed that the endoscopic technique was associated with lower patency rates after 1 year of follow-up (15).
In the study by Gaudino et al (15), seven trials involving 4,413 patients and 13,163 grafts were analyzed, with a median time to imaging of 1.02 years. Their study found that 33.7% of individuals had graft failure, with 16.6% of the total grafts failing, with factors such as an older age, female sex and smoking being independently associated with increased graft failure, while statin use provided a protective effect. Graft failure was linked to higher risks of myocardial infarction, repeat revascularization and increased all-cause mortality. By contrast, in the present study, SVG patency was 88.9% at 1-year follow-up, indicating relatively favorable short-term outcomes and after the imaging assessments, which occurred at an average of 1-year post-surgery (15).
It is also crucial to highlight the significance of dual antiplatelet therapy in preserving graft patency over both the short and long term, as emphasized by Harik et al (16) and Kim et al (10); these findings align with the approach adopted for the patients in the present study.
In conclusion, the present study demonstrated that LIMA grafts have superior patency at the 1- and 3-year follow-ups compared to SVGs using the no-touch technique. Additionally, DM was significantly associated with the number of grafts reflecting more advance coronary artery disease, whereas cross-clamp time did not exhibit a statistically significant association; furthermore, graft failure most commonly occurred at the distal anastomotic site.