Surgical ablation for AF is recommended for all symptomatic patients with documented AF during concomitant MV surgery (Class I, Level A). This recommendation comes with no added risk of operative mortality and major morbidity.

Surgical ablation for AF is recommended for all symptomatic patients with documented AF during concomitant isolated aortic valve surgery, isolated coronary artery bypass graft (CABG) surgery, and aortic valve plus CABG surgery (Class I, Level B nonrandomized). This recommendation comes with no added risk of operative mortality and major morbidity.

Stand-alone surgical ablation for AF is recommended for all symptomatic patients who are refractory or intolerant to antiarrhythmic drug therapy and who have failed one or more attempts of catheter ablation, are not candidates for catheter ablation, or prefer a surgical approach. (paroxysmal AF [PAF]: Class IIB, Level B randomized; persistent AF and LSpAF: Class IIA, Level B nonrandomized).

In our opinion, there are also relative indications for the surgical ablation of AF that were not addressed or explicitly mentioned in the consensus statement:

• 1.

  Patients with AF who have a contraindication to long-term anticoagulation therapy and a high stroke risk (CHA ₂ DS ₂ -VASc Score ≥2) are excellent candidates for surgery. The Cox-Maze-IV procedure not only effectively eliminates AF in the majority of these patients but also completely removes or closes the left atrial appendage (LAA), a significant source of atrial thrombus formation. Notably, the incidence of stroke after the procedure without anticoagulation has been remarkably low, even among patients with high CHA ₂ DS ₂ -VASc scores.

• 2.

  Patients with persistent and LSpAF who have experienced a stroke despite receiving adequate anticoagulation are at high risk for recurrent neurologic events. In our experience with 236 patients who underwent a stand-alone Cox-Maze-IV procedure, only 3 patients have experienced a postoperative stroke. This is particularly noteworthy considering that roughly 15% of these patients had previously had at least one cerebrovascular accident before undergoing surgery.

• 3.

  Patients with AF and with a thrombus in the LAA are unsuitable candidates for catheter ablation and should be evaluated for surgical ablation.

Finally, in the present era of minimally invasive approaches such as totally thoracoscopic procedures and hybrid procedures, it is crucial to establish a collaborative multidisciplinary team involving both electrophysiologists and surgeons to guarantee the proper selection and treatment of patients requiring stand-alone procedures.

Three decades of research and clinical experience have shaped our clinical decision-making process, and the following description reflects our current practice pattern. The Cox-Maze-IV procedure can be performed through either a median sternotomy or a minimally invasive right mini-thoracotomy. The choice of approach is determined by the presence or absence of concomitant cardiac pathology, patient-specific anatomic characteristics, and the expertise of the operating surgeon. In our institution, the preferred surgical approach for a Cox-Maze-IV procedure in patients undergoing stand-alone AF ablation or as a concomitant procedure to mitral or tricuspid valve surgery is a right mini-thoracotomy. Median sternotomy is reserved for patients with severe peripheral vascular disease that hinders femoral cannulation for CPB, patients with a history of a previous right thoracotomy, individuals with severe left ventricular dysfunction or chest wall deformities such as pectus excavatum, or cases in which the Cox-Maze-IV procedure is combined with other concomitant procedures such as aortic valve replacement and coronary artery bypass grafting. All Cox-Maze-IV patients should undergo preoperative echocardiography to assess ventricular function and to search for intracardiac thrombosis, patent foramen ovale (PFO) or atrial septal defect (ASD), and aortic insufficiency.

The Cox-Maze-IV procedure performed through a median sternotomy uses central cannulation of the aorta and bicaval cannulation or, rarely, femoral artery and vein cannulation for CPB. With a right mini-thoracotomy approach, peripheral cannulation is performed through a femoral cutdown (our preferred approach) or percutaneous cannulation of the femoral artery and vein.

Patients who are in AF at the time of surgery receive a dose of IV amiodarone after initiation of CPB. If a left atrial thrombus can be ruled out by intraoperative TEE, electrical cardioversion is performed. All patients undergo intraoperative exit block testing from each pair of isolated PVs after surgical ablation. This testing involves standard sterilizable insulated bipolar forceps connected to pacing cables and a temporary pacemaker (100–120 ppm). Pacing thresholds are measured from the PVs. Using a bipolar RF ablation device, the PVs are isolated by ablating a cuff of surrounding atrial tissue. Confirmation of electrical isolation is achieved by demonstrating the exit block from each PV. Although all four PVs are usually tested when using a median sternotomy, only the right PVs can be tested during minimally invasive right mini-thoracotomy. This quick, efficient, and inexpensive technique for assessing lesion integrity is the sole intraoperative quality control method. It confirms the successful creation of transmural nonconductive lesions and complete isolation of the PVs immediately after surgical ablation.

The right atrial lesion set of the Cox-Maze-IV includes (1) a continuous line of block from the SVC to the inferior vena cava (IVC), (2) a separate line from this intercaval line to the nonconductive tissue of the tricuspid annulus, and (3) a third lesion from the base of the right atrial appendage (RAA) across the anterolateral RA, taking care not to damage the sinoatrial (SA) or atrioventricular (AV) nodes ( Figs. 17.1 to 17.3 ). These RA lesions differ from those in the Cox-Maze-III procedure in that the lesion to prevent reentry around the base of the RAA in the Cox-Maze-III procedure is placed more anteriorly in the RA extending from lesion #3 up to the tip of the RAA (see Chapters 13 and 14 ).

Application of first pursestring suture and stab incision just above the interatrial septum, midway between the superior vena cava (SVC) and inferior vena cava (IVC), followed by radiofrequency ablations of the (1) IVC, (2) SVC, and (3) right atrial free wall directed toward the atrioventricular groove near the acute margin of the heart. This lesion is traditionally called the “T” lesion.

Substantial evidence supports the significance of the RA in the maintenance of persistent AF and of the cavotricuspid isthmus in classic atrial flutter. ^, Previous studies, including our own, have shown that up to one-third of AF drivers are located in the RA. This is why the best late outcomes of surgical ablation have been observed in patients who receive a biatrial lesion set rather than a LA-only lesion set.

We prefer to perform the right atrial lesion set on CPB before aortic cross-clamping. A bipolar RF ablation clamp is used for most lesions (see Figs. 17.1 and 17.3 ). When there is no need to open the RA, the right atrial free-wall ablations are typically made through three pursestring sutures (see Chapter 14 ). However, a single incision in the right atrial free wall is necessary if there is a need to repair the tricuspid valve or address a defect in the atrial septum (PFO or ASD). A small right atriotomy is also helpful for visualizing and cannulating the coronary sinus ostium for retrograde cardioplegia, and is used in all sternotomy cases.

The first pursestring suture is placed just above the interatrial septum, midway between the SVC and IVC. (It is placed two-thirds of the way down from the SVC to the IVC in the Cox-Maze-III procedure.) It is crucial to avoid the crista terminalis because of the thickness of the tissue in the area. One jaw of the bipolar RF clamp is introduced into the RA through a stab incision. Three separate ablation lines are performed through this first pursestring suture. These lines extend up into the SVC, down into the IVC, and across the right atrial free wall toward the AV groove near the acute margin of the heart (see Fig. 17.1 ). The IVC ablation line should extend as far as possible onto the IVC, and the SVC ablation line should be placed as lateral and posterior as possible to reduce the risk of injury to the anatomic SA node.

The second pursestring suture is placed at the superior end of the right atrial free wall ablation line near the AV groove. Temporarily filling the RA with volume can facilitate the placement of this pursestring suture. Care must be taken to avoid injuring the right coronary artery in this area. A linear cryoprobe is placed through this pursestring to extend the right atrial free-wall line (the “T” lesion) down to the tricuspid valve annulus, where it terminates at the 2 o’clock position (see Fig. 17.2 ). Before initiating freezing, it is important to palpate the cryoprobe in the right ventricle. Additionally, confirmation of correct placement is ensured when the beating heart deflects the probe. For nitrous oxide (N ₂ O) devices, cryoablations are performed at–60°C for 3 minutes each. For argon devices, the cryoablation is performed between–140°C and–160°C for 2 minutes each.

Left panel, The second pursestring suture and stab incision near the atrioventricular groove at the end of the first right atrial free wall ablation line, followed by an endocardial cryolesion down to the tricuspid annulus at the 2 o’clock position. Right panel, Schematic illustration for clarification.

The third pursestring suture is placed at the base of the RAA. One jaw of the bipolar RF clamp is inserted through this pursestring into the RA, and a second right atrial free wall ablation is created, extending several centimeters toward the SVC. It is crucial to avoid the anatomic SA node, so we leave a minimum of 2 cm between the end of this ablation line and the SVC line (see Fig. 17.3 ). We now perform this ablation line down the aortic side of the RAA to avoid the area of the SA node complex. The right atrial lesion set is completed by performing another endocardial cryoablation down to the tricuspid valve annulus at approximately the 10 o’clock position ( Fig. 17.4 ).

The third pursestring suture at the base of the right atrial appendage and creation of a right atrial free wall lesion using a bipolar radiofrequency clamp. The end of this lesion should be at least 2 cm from the intercaval line. The position of the anatomic sinoatrial (SA) node varies.

Left panel, Completion of the right atrial (RA) lesion set by extending an endocardial cryolesion from the end of the RA free-wall lesion down to the 10 o’clock position on the tricuspid annulus. Right panel, Schematic illustration for clarification.

The primary goals of the LA lesion set are (1) to establish a complete “box lesion” around all four PVs that electrically isolates not only the PVs but also the intervening posterior left atrial wall between the right and left PVs and (2) to block electrical conduction across the left atrial isthmus by connecting the box lesion to the mitral annulus, which is nonconductive.

Achieving complete isolation of the four PVs and the posterior LA with a box lesion is the single most important component of both the Cox-Maze-IV and Cox-Maze-III procedures (see Chapter 14 , Fig. 14.28 ). The posterior LA, encompassing the PVs, has consistently been identified as essential for initiating and maintaining AF. Approximately 70% of ectopic atrial triggers in patients with concomitant PAF are located within this area (see Chapter 25 ). ^, Furthermore, our data have shown that even if the PVs are successfully isolated and all of the other left atrial and right atrial lesions are complete, failure to isolate the posterior wall of the LA results in only a 33% freedom from recurrent atrial tachyarrhythmias at 5 years. Two randomized controlled studies showed that success rates for surgical PV isolation (PVI) are comparable to those of catheter PVI but with increased morbidity. ^, They also showed that PVI with either method that does not include exclusion of the posterior left atrial wall is an inadequate therapy for AF.

A linear lesion, known as the “left atrial isthmus line,” or the “mitral line,” connecting the box lesion to the posterior MV annulus is essential to prevent “atypical LA flutter,” which is also called “perimitral flutter.” Moreover, studies dating as far back as the late 1970s during development of the left atrial isolation procedure have shown that the coronary sinus itself can conduct electrical impulses (see Chapter 9 , Fig. 9.14 ). Therefore, to block conduction across the left atrial isthmus and prevent postoperative perimitral flutter, it is necessary to block conduction through both the coronary sinus with a cryolesion and conduction through the left atrial myocardium with the mitral line (see Chapter 48 ).

Right PV isolation is typically performed on CPB before cross-clamping the aorta as part of the box lesion. After blunt dissection between the right pulmonary artery and the right superior PV and opening the oblique sinus posterior to the IVC, an umbilical tape is passed around the right PVs ( Fig. 17.5 ), and pacing is performed before and after a bipolar RF clamp is applied to isolate the right PVs ( Fig. 17.6 ). It is important to place the bipolar clamp well up onto the LA to isolate as large a cuff of atrial tissue as possible around the right PVs. When performing this ablation, three sets of two consecutive (double) ablations without unclamping are performed with slight adjustments in position between each set, effectively resulting in the creation of three closely positioned concentric circles in the LA around the orifices of the right PVs. We then document complete isolation of the PVs by testing for exit block (see Chapter 20 ).

Blunt dissection and mobilization of the space between the right superior pulmonary vein and the right pulmonary artery from underneath the superior vena cava (SVC). IVC, Inferior vena cava.

Right-sided pulmonary vein isolation using a bipolar radiofrequency clamp.

Left-sided PV isolation is performed similarly to the right PVI if the Cox-Maze-IV procedure is performed through a standard median sternotomy. However, when the procedure is performed through a minimally invasive right mini-thoracotomy, left PV isolation is performed from the inside of the LA as it is done in the Cox-Maze-III procedure. After the placement of a left atrial retractor and lift system, the endocardial surfaces of the LA and MV are visualized ( Fig. 17.7 ). Starting from the inferior aspect of the left atriotomy, the bipolar RF clamp is used to create an ablation line across the floor of the LA toward the left inferior PV orifice, commonly referred to as “inferior connecting lesion” or the “floor lesion” ( Fig. 17.8 ). From the superior aspect of the left atriotomy, the bipolar RF clamp is used to create another ablation line across the roof of the LA toward the left superior PV, commonly referred to as the “superior connecting lesion” or the “roof lesion.” The endpoints of the bipolar ablation lines are usually marked with methylene blue if they are challenging to visualize.

Internal anatomy of the left atrium through a left atriotomy in Waterston’s groove. IVC, Inferior vena cava; LAA, left atrial appendage; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein; RIPV, right inferior pulmonary vein; RSPV, right superior pulmonary vein; SVC, superior vena cava.

Internal view of the right-sided pulmonary vein isolation with superior (roof) and inferior (floor) connecting lesions. Occasionally, the endocardial mitral line and the epicardial coronary sinus lesion can be created simultaneously with a bipolar radiofrequency clamp by the clamp from the lower end of the left atriotomy all the way to the mitral annulus. This should only be done in patients with dominant right coronary artery systems, and this lesion is placed between the last marginal branch of the distal circumflex coronary artery and the posterior descending branch of the right coronary artery in the so-called “watershed” area of the left atrioventricular groove. It should never be done in patients with either left-dominant or balanced coronary artery anatomy.

The mitral isthmus line is then created either with cryoablation alone or with a combination of bipolar RF and cryoablation depending on the anatomy of the mitral isthmus ( Figs. 17.8 to 17.10 ). The presence of the AV groove fat pad and its contents in that area (see Chapter 3 , Fig. 3.22 ) prevents the bipolar RF clamp from creating a transmural lesion all the way to the mitral annulus. The bipolar RF clamp is used, when needed, from the lower aspect of the left atriotomy to create an ablation line across the floor of the LA, heading toward the MV annulus and potentially across the coronary sinus (see Fig. 17.8 ). To bridge the gap of 1 to 2 cm and connect the bipolar ablation line to the annulus, an endocardial cryoablation is used toward the annulus (see Fig. 17.9 ). In many instances, a linear cryoprobe can complete this mitral isthmus lesion alone. Endocardial cryoablation is advantageous for preserving the heart’s fibrous skeleton, making it well-suited for ablation on valvular tissue. If needed, placing a lap pad beneath the cryoprobe’s shaft can reduce the risk of injury to the right phrenic nerve. To ensure complete conduction block across the LA isthmus, the coronary sinus cryolesion must be in line with the endocardial mitral line lesion (see Fig. 17.10 ). This is accomplished using an epicardial application of cryoenergy. It is essential to highlight a potential risk to the circumflex artery when creating the left atrial isthmus lesion at the mitral annulus in patients with a left-dominant system. For patients with a right-dominant system, the isthmus line is typically directed toward the junction of the P2 and P3 scallops of the posterior leaflet. In patients with a left-dominant system, injury can be prevented by directing the ablation toward the posteromedial commissure.

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