Coronary artery bypass surgery consists of two clearly differentiated phases: graft harvesting and myocardial revascularization itself. Optimizing outcomes requires excellence in both processes.

Graft Harvesting: Techniques and Considerations

The study under review emphasizes the first phase of the procedure, graft harvesting, which has gained increasing importance. Compared to the revascularization phase, graft harvesting is likely the main factor contributing to both early and late graft failure. This failure is a key predictor of adverse events, including increased mortality, following coronary artery bypass surgery. The phenomenon is multifactorial, involving acute thrombosis, intimal hyperplasia, inflammation, spasm, and atherosclerosis. Thus, various aspects must be carefully considered to preserve graft integrity and maintain functionality until they are used for constructing anastomoses:

1. Graft Harvesting: Skeletonization of internal mammary artery (IMA) grafts has become the preferred technique to reduce sternal complications. This approach is further supported by the expansion of off-pump revascularization and avoidance of aortic manipulation. These strategies enable longer grafts for sequential anastomoses, increasing their diameter. However, this technique carries a higher risk of mechanical and/or thermal injury and may result in the loss of certain vasomotor properties due to denervation of the surrounding adipose pedicle. The use of harmonic scalpels appears preferable for skeletonized IMA graft harvesting, although robust evidence is lacking. Double IMA grafting may be unsuitable in women, obese patients, and those with insulin-dependent diabetes mellitus due to a high risk of mediastinitis or inadequate graft development. In such cases, using the radial artery may help expand arterial graft options.
2. Saphenous Vein and Radial Artery Grafts: Endoscopic harvesting lacks strong evidence supporting its widespread use in cardiologic terms. While it offers clear surgical benefits in terms of wound aesthetics and reduced complications, it may not sufficiently offset potential graft damage, particularly in the fragile saphenous vein. Achieving comparable outcomes requires overcoming learning curves and generating new evidence that matches results from open techniques. For the saphenous vein, mid-term outcomes appear similar between open and endoscopic approaches, but observational evidence highlights significant graft damage in early-generation endoscopic harvesting devices and procedures. Pedicled techniques are preferred for saphenous vein harvesting, preserving adventitia and, where possible, some surrounding adipose tissue to minimize saphenous nerve damage. Overdistension testing should be avoided entirely, with pressure-controlled syringes (e.g., Maquet® Vasoshield®) recommended. Radial artery harvesting should also be performed pedicled to maintain vasomotility and reduce manipulation.

Graft Storage

Until utilized, grafts have been stored in various solutions, often without recognizing the potential endothelial damage that may result. Grafts should be kept in true “organ baths,” replicating physiological conditions of osmolarity, pH, and temperature while minimizing storage duration. Otherwise, anastomosing an inert conduit could have severe consequences, even if the intraoperative transit time flow (TTF) measurement is satisfactory. Abundant in vitro and observational evidence supports the use of buffered solutions (e.g., Duragraft®, He’s solution, or Hong Kong solution) over normal saline (acidic pH) or supposedly buffered solutions with autologous blood (alkalinized ex vivo). Buffered solutions help prevent endothelial damage, which is critical for graft integrity.

Prevention of Graft Spasm

Spasm-induced graft failure is a challenging complication to resolve, making preventive measures essential. Minimizing damage and manipulation during graft harvesting, preferably using pedicled techniques for the radial artery, is crucial. One recommended strategy includes longitudinal opening of the fascia on the muscular side while maintaining the integrity of the vascular bundle during radial artery harvesting. Vasodilatory solutions also play a significant role in spasm prevention. Protocols often include buffered papaverine in lactated Ringer’s solution or heparinized whole blood. Although papaverine is the most potent available arterial vasodilator, its intraluminal use may cause endothelial damage. Alternatives like He’s solution or Hong Kong solution offer promising options by combining storage and spasm prevention benefits.

Myocardial Revascularization

The second phase, myocardial revascularization, is regarded as the “noble” component of the procedure. Once an adequate “capital” of grafts is obtained, several premises must be considered:

1. Achieving Complete Revascularization: This involves covering all territories with tributary vessels affected by angiographically significant lesions (>70% stenosis, except for the left main coronary artery, which requires >50%) and with an appropriate vessel diameter (>1.5 mm caliber).
2. Graft Selection: Proper graft selection aims to maximize arterial graft usage while balancing the risk-benefit ratio for each patient based on graft availability, development, potential for long-term patency, indications, contraindications, and morbidity from harvesting. Contraindications for radial artery usage include prior catheterization, the need for future hemodialysis access, carpal tunnel syndrome, Raynaud’s phenomenon, atherosclerotic disease, pathological or positive Allen test results, and assignment to target vessels with proximal stenosis <70% in the left coronary territory or <90% in the right. Similar principles may extend to other arterial grafts like the internal mammary arteries, though the radial artery often has more liberal application. No pathological (fibrotic, atherosclerotic, calcified) or hypoplastic graft should be used solely to minimize surgical aggression during harvesting. When graft availability is limited, hybrid revascularization schemes to treat non-addressed territories should be considered. Radial artery calibers above 4 mm (RAPCO study) and saphenous vein calibers between 5–8 mm are considered optimal, depending on the segment used.
3. Anastomotic Quality and Geometry: Constructing a revascularization scheme with precise anastomotic techniques is essential. Intraoperative verification using TTF ensures graft functionality. Normofunctional parameters include a flow >15 mL/min, PI <5 (preferably <3), and diastolic flow >60–80% in the left coronary territory and >45–55% in the right. Although not the primary focus of this work, schemes utilizing composite or sequential grafts should carefully consider graft availability and the functional significance of the lesions. Distal vessels in sequential grafts should exhibit the most severe lesion, particularly in the right coronary territory. Evidence-based benefits for coronary artery bypass surgery were primarily obtained with independent aorto-coronary grafts, especially involving saphenous veins and radial arteries.
4. Minimizing Procedural Morbidity: Morbidity related to the approach, aortic manipulation, use of circulatory support, blood loss, and other factors should be minimized without compromising revascularization quality. Individualized approaches based on patient characteristics and the surgical team’s expertise are essential.

Optimal Medical Therapy

The optimal outcomes of invasive treatments must align with optimal medical therapy. Solid evidence supports the following axioms:

• Aspirin: Prescribe low-dose aspirin (100–325 mg/day) to prevent saphenous vein graft failure (observational evidence).
• Dual Antiplatelet Therapy: Add clopidogrel or ticagrelor during the first year to reduce saphenous vein graft failure (randomized evidence). Ticagrelor’s stable pharmacokinetics may make it preferable, except in patients with high bleeding risks. No evidence supports monotherapy with P2Y12 receptor inhibitors over aspirin.
• Statins: High-dose statins should be prescribed regardless of baseline cholesterol levels to delay atherosclerosis progression in coronary vessels and grafts. Ezetimibe and PCSK9 inhibitors may complement statins to meet secondary or tertiary prevention cholesterol targets.
• Calcium Channel Blockers: Low-dose amlodipine (2.5–5 mg twice daily) is recommended to prevent arterial graft spasm, particularly in radial arteries (meta-analysis of observational studies).

COMMENTARY:

Coronary artery bypass grafting (CABG) represents a highly refined surgical technique and serves as a testament to the evolution of scientific knowledge. Initially grounded in logical empiricism, CABG has advanced over more than 70 years, incorporating contributions from various surgical schools, observational studies, and, ultimately, randomized evidence. This progression enables surgeons to tailor the best therapeutic option for each patient, considering their clinical characteristics and coronary anatomy.

08Within this revascularization strategy, grafts have transitioned from being secondary elements to becoming central players in a procedure that has significantly improved the quantity and quality of life for patients. CABG is a shining example of how medical practice, guided by evidence, continues to evolve and transform patient outcomes.

REFERENCE:

Sandner S, Antoniades C, Caliskan E, Czerny M, Dayan V, Fremes SE, et al. Intra-operative and post-operative management of conduits for coronary artery bypass grafting: a clinical consensus statement of the European Society of Cardiology Working Group on Cardiovascular Surgery and the European Association for Cardio-Thoracic Surgery Coronary Task Force. Eur J Cardiothorac Surg. 2024 Nov 28;66(6):ezae400. doi: 10.1093/ejcts/ezae400.