Preoperative atrial fibrillation (AF) is present in 10% to 20% of patients undergoing coronary artery bypass grafting (CABG). , Although the prevalence of AF is much higher in those with valvular heart disease, far more CABG procedures than valve procedures are performed, so the absolute number of patients with concomitant AF requiring cardiac surgery is highest in patients undergoing CABG. In 2017, both the Society of Thoracic Surgeons (STS) guidelines and the Association for Thoracic Surgery Expert Consensus statement on AF treatment recommended that all patients with AF undergoing CABG should have concomitant AF ablation unless specific contraindications exist (see Chapter 24 ). , This recommendation was further strengthened in the 2024 STS guidelines. Because concomitant AF ablation is a Class 1A guideline recommendation, failure to treat AF in patients undergoing CABG falls below the contemporary standard of care. Absent specific contraindications, simply ignoring the concomitant AF is not a justifiable option.
Surgeons have several options to treat patients with concomitant AF, including left atrial appendage occlusion (LAAO), pulmonary vein isolation (PVI) alone, PVI plus LAAO, a box lesion, a box lesion plus LAAO, and the Maze procedure. As described in Chapter 25 , the expected results of each of these approaches varies widely depending on whether the patient has paroxysmal AF (PAF) or nonparoxysmal AF (non-PAF; persistent AF or long-standing persistent AF [LSpAF]). The choice of surgical approach must also consider that of these options, only the Maze procedure requires opening the left atrium (LA).
Atrial Fibrillation Ablation Procedure Options
The choice of AF ablation procedure for concomitant AF during CABG surgery hinges on the type of concomitant AF being treated. The importance of distinguishing between PAF and non-PAF and the rationale for different lesions sets has been discussed in detail in Chapter 25 . In patients with PAF, the best options are either a box lesion plus LAAO without opening the LA with an expected 80% success rate or a Maze procedure, which requires opening the LA with an expected success rate of more than 90%. We recommend performing a Maze procedure in all patients with non-PAF because it is highly successful compared with the other procedures, which have remarkably low success rates for non-PAF (see Chapter 25 ).
When comparing the results of these various lesion sets for PAF and non-PAF, the assumption is that every individual lesion in a particular lesion set is contiguous (no gaps) and uniformly transmural. If this assumption is incorrect and one or more of the individual lesions is less than perfect, it is meaningless to compare one lesion set with another. The integrity of individual lesions is independent of the lesion pattern; rather, it depends on the choice of ablation device, the energy source, and the surgeon. Unipolar radiofrequency (RF) ablation devices are notoriously unreliable for the creation of transmural lesions off pump because of the cooling-sink of the cavitary blood. When possible, bipolar RF clamps should be used to create off-pump lesions, and either bipolar RF clamps or cryosurgery should be used under cardioplegic arrest. Because CABG does not require opening the LA but performance of a Maze procedure does, we tend to reserve the use of the Maze procedure for patients undergoing CABG with LSpAF or permanent AF.
Clinical assessment is also important in deciding the appropriate lesion set for patients with concomitant AF in CABG. A careful history should be taken to distinguish between the symptoms related to the AF and those related to the coronary artery disease. AF-related symptomatology can include complications such as stroke, systemic embolization, heart failure, anticoagulation-related problems, and aggravated angina pectoris. We recommend a Maze procedure for patients who have had multiple catheter ablation failures before presenting for CABG surgery. On the other hand, some patients are asymptomatic from their AF and are at elevated operative risk for CABG from comorbidities. In such patients, it may be prudent to perform LAAO alone to lessen their long-term risk of stroke while expediting the CABG procedure.
In non-PAF, the available options for AF ablation procedures are the same as those for PAF, but the expected results for a given lesion set can be profoundly different in non-PAF. For example, in non-PAF, a box lesion plus LAAO achieves only 30% efficacy compared with 80% efficacy in PAF (see Chapter 25 ). Thus we do not recommend performing either PVI alone or a box lesion alone for concomitant non-PAF. The optimal choices for AF intervention during CABG for non-PAF with better than a 30% success rate are a left-sided Maze procedure (70%) and a biatrial Maze procedure (>90%), both of which require opening the LA. The decision to open the LA should be based on clinical factors and surgical risk in the opinion of the operating surgeon. Several studies have demonstrated that adding a Maze procedure to CABG does not impact the operative mortality or operative morbidity rates of the procedure. , However, in cases of emergency CABG with shock, an LAAO alone is reasonable.
Cannulation Techniques for Coronary Artery Bypass Grafting and Atrial Fibrillation Ablation
Typical cannulation for CABG surgery performed on cardiopulmonary bypass (CPB) is to place the arterial cannula in the distal ascending aorta and a single dual-stage venous return cannula in the right atrial appendage. Antegrade cardioplegia is administered through a line in the ascending aorta and retrograde cardioplegia through a cannula positioned into the coronary sinus through the right atrial wall. Cannulation for CPB in a CABG patient who requires concomitant AF ablation is modified depending on the concomitant AF ablation procedure to be performed. We recommend bicaval venous cannulation in patients undergoing AF ablation and CABG if a Maze procedure is to be performed ( Fig. 26.1 ) because it does not interfere with the right atrial lesions, offers better exposure for the left atrial lesions, and keeps the atria colder (see Chapter 47 , Figs. 47.8 and 47.9 ). Ideally, a right-angle venous return cannula is placed in the intrapericardial segment of the SVC approximately 2 cm cephalad to the SVC–right atrium (RA) junction, and a right-angle venous cannula is placed low and anterior in the RA near the level of the inferior vena cava (IVC)–RA junction. The retrograde cardioplegia cannula should be placed in the lower third of the RA where the diagonal atriotomy will be placed as a part of the right atrial T-lesion. If the planned AF ablation procedure does not require opening of either atrium, a single dual-stage venous return cannula is satisfactory.
Cannulation sites for cardiopulmonary bypass (CPB) in patients undergoing coronary artery bypass grafting (CABG) and atrial fibrillation (AF) ablation. Optimal venous cannulation sites for CPB and retrograde cardioplegia in CABG patients undergoing the concomitant ablation of AF using a Maze procedure. The superior vena cava (SVC) is cannulated anteriorly 2 cm above the SVC–right atrium (RA) junction. The inferior vena cava (IVC) is cannulated as low and anterior as possible. Bicaval cannulation at these two sites results in less interference with performance of the right atrial lesions and better exposure of the internal left atrium. The retrograde cardioplegia cannula is placed through a stab wound in the lateral RA in a position that will be included in the right atriotomy used to create the right atrial lesions.
Conduct of the Combined Surgical Procedure
In LAAO alone with CABG, we recommend placing an epicardial LAAO device on the left atrial appendage (LAA) immediately after arresting the heart to enhance the ability to position it at the true base of the LAA to avoid leaving a stump. It is preferable to construct bypass grafts to the left circumflex artery, which avoid direct contact with the external LAAO device.
For concomitant AF ablation procedures that do not require opening the atria, we recommend performing the AF ablation procedure before constructing the coronary artery bypass grafts. After institution of CPB, Waterston’s groove is developed to expose the LA wall. The oblique sinus is opened underneath the IVC, and a plane of dissection is established between the right superior pulmonary vein (PV) and the right pulmonary artery to allow complete encirclement of the right PVs. A bipolar RF clamp can then be applied well up onto the posteromedial LA to avoid RF injury of the orifices of the right PVs ( Fig. 26.2 ). Next, the heart is arrested with antegrade and retrograde cardioplegia. The heart is then retracted to the right to expose the left PVs and LAA. ( Fig. 26.3 ). The retraction of the heart in this manner stretches the ligament of Marshall, making it easier to identify and divide with electrocautery ( Fig. 26.4 ). The potential space between the left pulmonary artery and left upper PV is developed, and the left PVs are encircled. A bipolar RF clamp is then applied as high on the LA and away from the left PV orifices as possible ( Fig. 26.5 ). An epicardial LAAO device is then applied to the base of the LAA to exclude it and to complete the ablation lesion set ( Fig. 26.6 ). The advantage of performing the AF ablation before the CABG procedure is to avoid injury to the bypass grafts or coronary anastomoses during AF ablation.
Isolation of the right pulmonary veins (PVs). Waterston’s groove separating the posterior right atrium (RA) and left atrium (LA) is first developed, and then a plane of dissection is established between the right superior pulmonary vein (RSPV) and the right pulmonary artery (RPA). A bipolar radiofrequency ablation clamp is then placed well up onto the LA as far as possible away from the PV orifices, and the right PVs are isolated. RIPV, Right inferior pulmonary vein.
