Several modifications of AF catheter ablation techniques have been proposed in an effort to improve outcomes, ranging from pulmonary vein isolation (PVI), to wider inclusion of the antrum of the pulmonary veins (PVs), to including the posterior wall of the left atrium (LA) in a box lesion, to substrate modification by ablating complex atrial fractionated electrograms and trying to create linear lesions in the atrium. Unfortunately, only the inclusion of the posterior LA wall in a box lesion has clearly proven to be superior to PVI alone. However, the potential risk of esophageal injury associated with isolation of the posterior LA wall using an endocardial radiofrequency (RF) catheter has resulted in simple PVI remaining as the primary technique for the catheter ablation of AF. Unfortunately, success rates below 50%, even after multiple catheter ablation procedures for LSpAF, have dampened the enthusiasm of the electrophysiology community for treating such a complex subset of patients at all. Furthermore, recent studies have shown that in LSpAF, the macro-reentrant drivers that sustain AF are more complex than originally thought and may exhibit epicardial–endocardial dissociation on electroanatomic mapping. ^,

Most patients referred for the surgical ablation of AF have undergone multiple prior catheter ablations. Endocardial catheter PVI is associated with high success rates in patients with paroxysmal AF (PAF); therefore, hybrid procedures are rarely required in those patients. However, some patients with recurrent AF after PVI who are thought to have complete isolation of the PVs on the basis of endocardial maps can have epicardial breakthroughs that go undetected by endocardial mapping. This phenomenon can result in failure of an endocardial catheter PVI that requires thoracoscopic epicardial ablation. However, most catheter ablation failures occur in patients with persistent AF or LSpAF. Hybrid procedures offer these patients a complementary solution to address problems with a prior PVI as well as incomplete isolation of the posterior wall of the LA. Only recently has a complete Cox-Maze lesion set has been accomplished with a hybrid approach ; the hybrid Maze procedure is described in Chapter 37 .

Left atrial dimensions as determined by echocardiography and the duration of AF are also considered in the selection of patients to undergo hybrid procedures. Prior failed catheter ablation is a risk factor for AF recurrence following thoracoscopic epicardial surgical ablation. This is likely due to the presence of a complex substrate in the atrium with significant atrial remodeling and endocardial scar formation. Previous cardiac surgery is considered to be a contraindication for hybrid procedures because of pericardial adhesions.

Different minimally invasive surgical approaches have been described for performing the initial epicardial surgical ablation in a hybrid procedure, including mini-thoracotomies, thoracoscopy, and a subxiphoid approach. In addition, several different ablative lesion sets have been used in hybrid procedures, but the common goal has been to create an off-pump, epicardial-only surgical approach performed in conjunction with endocardial catheter ablation. Hybrid procedures can be performed as a “joint” procedure at the time of the initial thoracoscopic surgery or as a “staged” procedure in which the endocardial catheter ablation portion of the procedure is delayed several weeks to allow time for the epicardial lesions to mature.

The ablative energy source that is currently used for the initial epicardial ablation is either unipolar or bipolar RF. Although bipolar RF clamps were used most commonly in the early experience with minimally invasive approaches, different linear devices have since been developed that augment lesion sets and minimize surgical manipulation. Cryoablation is not effective for off-pump epicardial ablation because of the “heat sink” caused by the circulating normothermic cavitary blood (see Chapter 20 ). This is also a challenge for off-pump unipolar RF epicardial ablation in which the cavitary blood acts as a “cooling sink.” Other energy sources, such as microwave and high-intensity focused ultrasound, have been proposed in the past but are no longer in use.

The primary objective of the initial thoracoscopic epicardial ablation of a hybrid procedure is to create a box in the LA that isolates all four PVs and the intervening posterior left atrial wall. The most common technique for creating the box in hybrid procedures is to isolate the right and left PVs in pairs using bipolar RF clamps passed through bilateral mini-thoracotomies or thoracoscopic ports. Floor and roof lesions are then created to isolate the posterior left atrial wall and complete the posterior box. These lesions have traditionally been created using a dual-electrode, unipolar Coolrail linear pen (Atricure Inc.). ^, Other techniques and devices to create the box lesion included a linear RF ablation device that could be wrapped around all four PVs and the posterior left atrial wall to create a complete box lesion, but it is no longer in use. More recently, a novel approach, the Convergent procedure, was introduced in which the posterior left atrial wall is ablated rather than isolated and the PVs are then isolated by endocardial catheter ablation (see Chapter 36 ). One advantage of the Convergent procedure is that it mitigates the risk of esophageal injury during isolation of the posterior left atrial wall that can occur with extensive endocardial catheter ablation. Another advantage is that it is performed through a small subxiphoid incision, though if the left atrial appendage is to be closed, it requires a separate left chest incision.

Hybrid procedures allow for the intraoperative validation of both epicardial and endocardial entrance and exit block as well as for advanced high-density mapping to confirm the acute results of the epicardial ablation. The role of the electrophysiologist is to detect and address any endocardial gaps in the surgical ablation lines or, during the convergent procedure, to complete the isolation of the PVs.

The clinical results of different hybrid procedures vary significantly due to a variety of factors that affect outcomes. These factors include the type of being treated (PAF versus nonparoxysmal AF [non-PAF]), the duration of (<5 years versus >5 years), the selected surgical approach (thoracotomy versus thoracoscopy versus subxiphoid), the choice of ablation device (bipolar RF versus unipolar RF), and the preferred ablation lesion set (PVI versus box lesion versus posterior wall ablation). Most published data are based on single-center experiences with limited cohorts of patients. The overall aggregate success rate of hybrid procedures in terms of freedom from AF ranges from approximately 60% to approximately 80%, and complication rates vary between 2% and 6%. ^{, ,}

Recently, three prospective randomized trials of hybrid procedures (CONVERGE, HARTCAP, CEASE-AF) that used different surgical techniques and technologies demonstrated a superiority of hybrid procedures over catheter ablation with an absolute increase in sinus rhythm restoration, especially in patients with LSpAF, ranging between 20% and 40%. Most of the published series report only 1- to 3-year follow-up data, so there is a paucity of information regarding the long-term results of hybrid procedures. Therefore, additional clinical evidence from either institutional experiences or prospective randomized trials is needed to assess the impact of hybrid procedures on long-term outcomes such as quality of life, stroke, heart failure, and mortality.