Abstract
Arrhythmias remain one of the leading causes of death for adults with congenital heart disease. Although catheter ablation is often successful in this population, patients with complex arrhythmia mechanisms or complex cardiac anatomy stand to benefit from surgical ablation, often performed at the time of other indicated cardiac surgery. In the setting of atrial fibrillation, the full biatrial lesion set of the Cox-Maze IV procedure has produced excellent long-term results, with nearly 80% freedom from atrial tachycardias at 5 years, as well as improved long-term survival. A variety of modified lesion sets have been applied to congenital heart patients with success in expert hands, and guidelines for the treatment of arrhythmias in this patient population have recently been created. This chapter reviews the history, indications, techniques, postoperative management, and expected outcomes of arrhythmia surgery in patients with congenital heart disease.
Key words
Congenital heart disease, Arrhythmia, Atrial fibrillation, Ablation, Maze procedure, Fontan
The definitive treatment of arrhythmias began in the late 1960s with the development of surgical techniques for disruption of accessory atrioventricular (AV) connections in Wolff-Parkinson-White syndrome by Sealy, Wallace, and Boineau at Duke University. From this foundation, extensive experimental work by Cox, Boineau, and colleagues at Duke and then at Washington University in St. Louis led to the development of surgical techniques for treatment of ventricular arrhythmias, AV and AV nodal reentry tachycardia, and the Maze procedure for atrial fibrillation. Experimental and translational work in our laboratory has produced continued refinement of the original “cut-and-sew” Cox-Maze procedure, most notably through the application of energy sources for replacement of most of the suture lines with either radiofrequency (RF) or cryothermal ablation lines. This has allowed for reduced complexity, reduced operative time, and greater reproducibility of the Maze procedure, as well as its completion through minimally invasive approaches.
Techniques for catheter-based electrophysiologic mapping and arrhythmia ablation also developed alongside of, and were greatly informed by, the advances made in arrhythmia surgery over this time. Catheter ablation has found wide adoption given its relatively low invasiveness and frequent effectiveness and today is usually the first treatment approach for patients requiring arrhythmia intervention. However, the long-term outcomes of catheter ablation can fall short of surgical ablation, especially for patients with long-standing arrhythmias or complex arrhythmia substrates. Surgical ablation therefore remains an important method of arrhythmia therapy for patients who have experienced failure of catheter ablation, who are undergoing cardiac surgery for another reason, or who have specific anatomic or electrophysiologic reasons to suggest that catheter ablation may be unsuccessful.
With improved overall survival of patients with congenital heart disease, the common occurrence of late postoperative arrhythmias has been appreciated, along with their contributions to late morbidity and mortality in this population. Arrhythmias remain a leading cause of death in adults with congenital heart disease, and those who develop atrial arrhythmias have a 50% increase in mortality, a twofold increase in risk of stroke and/or heart failure, and a threefold increase in risk of needing reintervention. Lesions such as Ebstein anomaly, single-ventricle lesions, tetralogy of Fallot, atrial repairs of transposition of the great arteries, truncus arteriosus, and atrial septal defects (ASDs) have the highest risk for late arrhythmia development. Frequently these patients have additional indications for reoperation at some point in their management ( Table 68.1 ). A variety of modifications to established surgical ablation techniques have been developed and reported for such patients.
| CHD Lesion | Reoperation | Atrial Arrhythmias | Ventricular Tachycardia |
|---|---|---|---|
| Ebstein anomaly | 30%-50% | 33%-60% | >2% |
| Single ventricle | >25% | 40%-60% | >5% |
| Tetralogy of Fallot | 26%-50% | 15%-25% | 10%-15% |
| Transposition of the great arteries, atrial switch | 15%-27% | 26%-50% | 7%-9% |
| Transposition of the great arteries, arterial switch | 12%-20% | <2% | 1%-2% |
| Congenitally corrected transposition of the great arteries | 25%-35% | >30% | >2% |
| Truncus arteriosus | 55%-89% | >25% | >2% |
| Atrioventricular septal defect | 19%-26% | 5%-10% | <2% |
| Atrial septal defect | <2% | 16%-28% | <2% |
This chapter reviews indications, techniques, postoperative management, and expected outcomes of arrhythmia surgery for patients with congenital heart disease. We review the standard Cox-Maze IV lesion set and surgical technique that we apply for patients with normal anatomy undergoing atrial ablation. We also review published modifications to this lesion set based on the particular arrhythmia substrate or special anatomic considerations when being applied to patients with congenital heart disease. Because persistent arrhythmias are generally a late-developing burden of congenital heart disease, this review is most relevant to older children and adults with congenital heart disease.
Indications for Arrhythmia Surgery
Expert consensus guidelines have been recently developed by the Pediatric and Congenital Electrophysiology Society (PACES) and the Heart Rhythm Society (HRS) to provide indications for arrhythmia surgery in patients with congenital heart disease and to guide the selection of arrhythmia procedure type ( Tables 68.2 to 68.4 ). Indications for arrhythmia surgery are generally grouped into three main categories: (1) patients with arrhythmias who have experienced failure of catheter ablation, (2) patients with known arrhythmias who are undergoing concomitant surgery for congenital heart disease, and (3) prophylactic ablation in patients with high risk for future arrhythmia development who are undergoing concomitant surgery for congenital heart disease.
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Although the most common role for arrhythmia surgery in patients with congenital heart disease is the completion of a Maze procedure for atrial fibrillation or atrial macro-reentry tachycardias, surgical ablation is also indicated in patients with accessory pathways, focal atrial tachycardias, or AV nodal reentry circuits who have experienced failure of catheter ablation. In comparison with catheter ablation, especially in complex anatomy, surgical ablation techniques allow direct visualization of the anatomy, can be more efficient for performing complete lines of block between difficult-to-access anatomic structures, and can provide more complete lines of ablation.
Cox-Maze IV Procedure
The Cox-Maze procedure for atrial fibrillation went through several revisions throughout its development based on the results of extensive laboratory testing, with serial refinement of lesion sets and surgical technique. The Cox-Maze IV procedure refers to the modern, ablation-assisted, biatrial technique performed by most arrhythmia surgeons today, in which many of the suture lines of previous versions are replaced by lines of ablation. Many energy devices are commercially available for surgical cardiac ablation, but we advocate the primary use of bipolar RF ablation clamps because they safely create rapid, consistently transmural lesions in both animal and human studies. Cryothermal energy is an important adjunct that is used for creating lesions close to valve tissue and the fibrous skeleton of the heart because it induces cell death while preserving tissue collagen and normal architecture.
The following sections outline the surgical technique of the Cox-Maze IV procedure as performed in patients with normal atrial anatomy, which forms an important basis for understanding modifications to these techniques for patients with congenital heart disease.
Preparation
Although patients undergo transthoracic echocardiography during preoperative assessment, the left atrial appendage (LAA) is not well visualized with this modality, and thrombus cannot be excluded with certainty. The left atrium is therefore thoroughly examined with intraoperative transesophageal echocardiography (TEE) or epicardial ultrasonography, and in those rare patients with identified thrombus, care is taken to minimize manipulation of the heart until exclusion of the LAA has been performed. Coexisting congenital lesions and valvular disease are also assessed by TEE. At the conclusion of the procedure TEE is used to confirm successful exclusion of the LAA and to evaluate any additional repairs performed.
The Cox-Maze IV procedure can be broken down into three primary components: (1) pulmonary vein (PV) isolation, (2) creation of the right atrial lesion set, and (3) creation of the left atrial lesion set.
Pulmonary Vein Isolation
A median sternotomy is performed, and the pericardium is opened in standard fashion. Bicaval and aortic cannulas are placed, and normothermic cardiopulmonary bypass is initiated. The right and left PVs are bluntly dissected, with care taken to fully dissect the epicardial fat pad off the atrial surface, and are surrounded with umbilical tapes. If the patient is in atrial fibrillation and there is no thrombus on ultrasound evaluation, amiodarone is administered, and the patient is electrically cardioverted to normal sinus rhythm. Pacing thresholds are obtained from each PV using a bipolar pacing probe. The right and left PVs are each isolated using a bipolar RF clamp, such that a circumferential line of ablation surrounds as large a cuff of atrial tissue as possible ( Fig. 68.1 ). For these and all subsequent lines created using the bipolar RF clamp, three discrete ablations are performed with slight adjustments in clamp position, effectively forming three closely approximated concentric circles to ensure isolation. If the surgeon is using a nonirrigated bipolar clamp, the jaws must be cleaned of char every two to three ablations to ensure the creation of transmural lesions. PV isolation is confirmed by documenting exit block, or failure of atrial capture, with epicardial pacing from each of the PVs. Further ablations are performed as needed until exit block is obtained.
Right Atrial Lesion Set
The patient is cooled to 34°C, and the right atrial lesion set is performed on the beating heart. A small purse-string suture is placed at the base of the right atrial appendage, and a stab incision is made at its center, wide enough to accommodate one jaw of the bipolar RF ablation clamp. An ablation lesion is created with the clamp across the free wall of the right atrium down toward the superior vena cava, taking care to avoid the sinoatrial (SA) node ( Fig. 68.2 ). A vertical atriotomy is then made from the interatrial septum up toward the AV groove near the free margin of the heart. When possible, this incision should be at least 2 cm from the first free wall ablation to avoid creating an area of slow conduction. A linear cryoprobe is used to create an endocardial cryoablation from the superior aspect of the atriotomy down to the tricuspid annulus at the 2 o’clock position. All cryoablations are performed for 3 minutes at −60°C. Cryoablation is preferable to RF ablation over annular tissues because it preserves the fibrous skeleton of the heart, avoiding any potential compromise of valve competency. The linear cryoprobe is then inserted through the previously placed purse-string suture, and an endocardial cryoablation is created down to the tricuspid valve annulus at the 10 o’clock position ( Fig. 68.3 ). The bipolar RF clamp is then used to create ablation lines running from the inferior aspect of the right atriotomy up along the lateral aspect of the SVC and down the inferior vena cava (IVC). The SVC ablation should be performed as lateral and posterior as possible to minimize the risk of injury to the SA node, and the IVC ablation line should travel as far as possible onto the IVC ( Fig. 68.4 ). Finally, the right atriotomy is closed in standard fashion.
