Introduction

Coronary artery bypass grafting (CABG) remains a cornerstone of surgical management of coronary artery disease (CAD), and is widely performed across the globe. Dynamic advancement of cardiac surgery has allowed for ongoing refinement of surgical techniques and a decrease in the number of procedure-related complications. The invasiveness of CABG can be minimized in 2 primary ways: 1) by performing the procedure on a beating heart, and 2) by minimizing the extent of the surgical incision.

Off-pump CABG (OPCAB) is generally preferred in patients with extensive aortic atherosclerosis as well as in those at a high risk of complications associated with cardiopulmonary bypass.1 In parallel, minimally-invasive strategies, such as minimally-invasive direct coronary artery bypass (MIDCAB) and totally endoscopic coronary artery bypass (TECAB), have been introduced to reduce surgical trauma, minimize incision extent, shorten recovery time, and improve cosmetic outcomes. These approaches are particularly recommended in patients with isolated proximal left anterior descending artery (LAD) stenosis or within the framework of hybrid coronary revascularization.1 Proper patient selection and multidisciplinary evaluation by the heart team remain essential to optimize procedural outcomes and ensure an individualized therapeutic approach.2

Off-pump coronary artery bypass grafting

Unlike conventional on-pump CABG (ONCAB), which involves cardioplegic arrest and extracorporeal circulation (ECC) to maintain organ perfusion and myocardial protection, OPCAB is performed on a beating heart, without ECC. While ONCAB remains the standard approach, it carries inherent risks related to aortic manipulation and the systemic effects of ECC, including neurological complications, acute kidney injury, coagulopathy, and inflammatory responses.3,4 OPCAB mitigates these risks by avoiding ECC and maintaining physiological cardiac function, making it particularly advantageous in patients with extensive aortic atherosclerosis or elevated perioperative risk.

The surgical access in OPCAB remains a median sternotomy. A dedicated device allows for precise positioning and stabilization of the anastomosis site by restricting myocardial movement in the targeted surgical area.5 Nevertheless, the procedure can be technically demanding, particularly when addressing lesions in the posterior or lateral myocardial territories. Therefore, the 2018 European Society of Cardiology / European Association for Cardio-Thoracic Surgery guidelines recommended that OPCAB be performed by experienced operators in specialized centers.1 In unstable or high-risk patients, beating-heart CABG may be supported by ECC to maintain hemodynamic stability when necessary.6

Numerous meta-analyses have shown that OPCAB is associated with a lower incidence of cerebrovascular events and ischemic stroke than ONCAB, especially in patients with extensive aortic atherosclerosis, who benefit most from no-touch techniques.3,7-9 Additionally, OPCAB significantly reduces the risk of postoperative atrial fibrillation (AF) and acute kidney injury.10-12 Guan et al13 reported the superiority of OPCAB in patients with ejection fraction lower than or equal to 40%, particularly in short-term outcomes, such as mortality, stroke, myocardial infarction, renal failure, and bleeding complications. Likewise, Wang et al14 reported significantly lower early mortality rates and a lower risk of AF, cerebrovascular events, and blood transfusion in patients with chronic kidney disease; however, the myocardial infarction rates and long-term survival did not differ significantly between the 2 methods. Machado et al15 showed that in elderly patients (aged >65 years) both techniques had comparable outcomes, although the need for repeat revascularization was more frequent in the OPCAB group. Despite these benefits (Table 1), some studies report higher long-term mortality rates in patients undergoing OPCAB, as compared with those treated with ONCAB.16,17

Table 1. Advantages of off-pump coronary artery bypass grafting

Advantage

Description

References

Reduced neurological morbidity

Avoidance of ECC and aortic cross-clamping reduces the risk of cerebral embolization, particularly in patients with aortic atherosclerosis.

3,7-9,14

Reduced risk of postoperative AF

OPCAB minimizes the systemic inflammatory response and myocardial ischemia–reperfusion injury associated with ECC, preserves atrial tissue integrity, and maintains stable hemodynamics.

10,11,14

Reduced risk of postoperative renal failure

OPCAB reduces hemolysis by avoiding mechanical trauma from ECC and preserves pulsatile renal perfusion.

12,13

Reduced blood loss and transfusion requirements

OPCAB avoids hemodilution and platelet dysfunction commonly associated with ECC.

9,13,14

Shorter mechanical ventilation time

Avoidance of ECC is associated with a lower level of systemic inflammatory response that contributes to postoperative pulmonary dysfunction.

11,14

Reduced risk of infection

Shorter mechanical ventilation time and reduced systemic proinflammatory activation may contribute to a lower incidence of postoperative infections, including pneumonia.

13,14

Shorter ICU and hospital stay

Faster postoperative recovery and fewer complications lead to reduced ICU and overall hospital stay.

11,14

Suitability for comorbid patients

OPCAB is particularly advantageous in patients with reduced left ventricular ejection fraction, chronic kidney disease, or severe aortic atherosclerosis.

8,13,14

Abbreviations: AF, atrial fibrillation; ECC, extracorporeal circulation; ICU, intensive care unit; OPCAB, off-pump coronary artery bypass grafting

Minimally-invasive direct coronary artery bypass

MIDCAB is predominantly performed in patients with single-vessel disease or as part of a hybrid treatment; nonetheless, it remains feasible in patients with prior coronary bypass surgery.18,19 The procedure is conducted on a beating heart via a left minithoracotomy (Figure 1). The patient is intubated with a double-lumen endotracheal tube to allow for selective lung ventilation. The intervention primarily targets the left coronary artery (commonly left internal mammary artery to LAD anastomosis); however, right coronary artery grafting is also feasible via a right minithoracotomy.20 Moreover, MIDCAB can be performed as a concomitant procedure, allowing for the simultaneous management of CAD and other cardiac surgical conditions, such as AF.21-23 The minimally-invasive approach reduces overall surgical invasiveness while offering a comprehensive and efficient therapeutic strategy.

Figure 1. Left minithoracotomy; stabilization of the left internal mammary artery–left anterior descending artery anastomosis site with the Stabilizer Arm (Terumo Cardiovascular, Ann Arbor, Michigan, United States)

Several meta-analyses have demonstrated the superiority of MIDCAB over percutaneous coronary intervention in the treatment of isolated LAD disease, as MIDCAB was associated with a significantly lower risk of long-term repeat target vessel revascularization and major adverse cardiovascular events, highlighting its durability and clinical benefit in this specific patient population.24-27 Furthermore, there is increasing clinical experience demonstrating that MIDCAB is effectively utilized as part of hybrid revascularization strategies in the management of multivessel CAD.28 This approach combines the durability of surgical grafting with the complementary benefits of percutaneous techniques, offering an optimized and less invasive solution for selected patients. In comparison with OPCAB, it is associated with a reduced need for blood transfusions, lower postoperative cardiac troponin levels (indicative of reduced myocardial injury), and significantly shorter hospital and intensive care unit stays.29 The minimally-invasive approach has been shown to be both safe and effective.29-32 Figure 2 presents a comparison of the minimally-invasive approaches with ONCAB, highlighting the advantages of the minimally-invasive techniques and underscoring their role in enhancing perioperative outcomes and promoting faster patient recovery.

Figure 2. Comparison of minimally-invasive techniques with on-pump coronary artery bypass grafting

Abbreviations: CABG, coronary artery bypass grafting; LAD, left anterior descending artery; MIDCAB, minimally-invasive direct coronary artery bypass; ONCAB, on-pump coronary artery bypass grafting; TECAB, totally endoscopic coronary artery bypass; others, see Table 1

Robotic coronary artery bypass grafting

Internal mammary artery harvesting and vascular anastomoses may be performed robotically via a minimally-invasive approach through ports placed in the intercostal spaces (Figure 3). The use of a surgical robot enhances precision, range of motion, and dexterity, in addition to providing high-quality visualization. Robot-assisted CABG is noninferior to the conventional approach with respect to graft patency; moreover, robotic harvesting provides better vessel visualization and facilitates complete retrieval, enabling access to the lateral / posterior wall targets.33-35 Kofler et al36 reported that perioperative and long-term outcomes of robotic CABG were comparable to those of conventional CABG, demonstrating the efficacy and safety of the robotic approach as an alternative surgical method in selected patients. Additionally, patients undergoing robotic CABG require fewer narcotic medications during the postoperative period than those undergoing conventional CABG, indicating that the minimally-invasive approach may lead to less postoperative pain.37 Leyvi et al38 reported that robotic CABG was associated with a lower 30-day complication rate and shorter length of hospital stay than conventional ONCAB, suggesting faster recovery.

Figure 3. Robot-assisted left internal mammary artery (arrow) harvesting (da Vinci Xi, Intuitive Surgical, Sunnyvale, California, United States)

TECAB is a safe and effective treatment option for both single and multi-vessel disease, minimizing surgical trauma, and accelerating postoperative recovery.39-41 However, the learning curve and costs still limit its rapid and widespread adoption.

Hybrid revascularization

Hybrid procedures, which can be performed either simultaneously or in a staged manner, combine minimally-invasive CABG and percutaneous coronary intervention in patients with multivessel disease. The remarkable advances in CAD treatment have facilitated effective collaboration between cardiac surgeons and interventional cardiologists, further enhanced by robot-assisted techniques.42 According to a study by Bonatti et al,43 robot-assisted hybrid revascularization had a relatively low mortality rate (1.3%) and was associated with minimal surgical trauma, short recovery time, and promising long-term survival, with a 5-year survival rate of 92.9%.

Although current data on hybrid coronary revascularization remain limited due to low adoption rates and methodological challenges, recent years have shown increasing interest and growing clinical experience. Generally, peri- and postoperative outcomes of the hybrid approach are promising, with several studies indicating a reduced risk of perioperative blood transfusion, shorter mechanical ventilation times, lower postoperative troponin release, and decreased length of hospital stay, as compared with CABG.44-47 The rates of postoperative complications, such as AF, stroke, renal complications, and myocardial infarction, appear to be comparable.44,47,48 While Harskamp et al49 reported a higher risk of repeat revascularization in the hybrid group, the 5-year outcomes of the randomized POLMIDES (Prospective Randomized Pilot Study Evaluating the Safety and Efficacy of Hybrid Revascularization in Multi-Vessel Coronary Artery Disease) trial contradicted these findings, demonstrating a comparable incidence of repeat revascularization between the hybrid and conventional CABG groups.50 Several meta-analyses reported similar midterm mortality; however, the length of follow-up was limited.47-49,51

Although the findings suggest that the hybrid approach is a promising and feasible treatment option for multivessel disease, offering reduced surgical trauma, faster recovery, and fewer transfusions, the results should still be interpreted with caution, given the limited long-term data and methodological variability across studies.48,51,52

Conclusions

The invasiveness of coronary surgery is minimized by performing operations on a beating heart and reducing the extent of the incision. Minimally-invasive CABG methods, such as MIDCAB and TECAB, decrease surgical trauma and shorten recovery time. Beating-heart procedures are associated with a reduced risk of neurological complications and stroke.