What is a full Cox Maze procedure for an adult patient with severe and symptomatic atrial fibrillation who has not responded to other treatments, such as medication or catheter ablation?

What is a Full Cox Maze Procedure?

The full Cox Maze procedure is a surgical operation that creates a series of strategic incisions or ablation lines in both the right and left atria to eliminate macroreentrant circuits, isolate the pulmonary veins, connect these lesions to the mitral valve annulus, and create electrical barriers that prevent sustained atrial fibrillation while preserving sinus node and atrial transport function. 1

Mechanism and Rationale

The procedure is based on the hypothesis that reentry is the predominant mechanism responsible for atrial fibrillation. 1 The strategic placement of atrial incisions creates barriers to conduction that limit the amount of myocardium available to propagate reentrant wave fronts, thereby preventing sustained AF. 1 The name "maze" derives from the concept of creating a geographical maze in the heart tissue that guides electrical impulses along a specific path from the sinoatrial node to the atrioventricular node. 2, 3

Technical Components of the Full Procedure

The complete Cox Maze procedure includes several critical elements:

• Pulmonary vein isolation through transmural lesions that completely encircle all four pulmonary veins 1
• Connection of pulmonary vein lesions to the mitral valve annulus to prevent left atrial macroreentry 1
• Right atrial lesions that create electrical barriers preventing macroentrant rhythms (atrial flutter or AF) from becoming sustained 1
• Preservation of sinus node function and atrial transport capacity 1
• Left atrial appendage amputation or obliteration to reduce thromboembolic risk 1

Evolution of the Technique

The procedure has undergone three major iterations (Maze I, II, and III), with the Cox Maze III becoming the standard "cut-and-sew" technique. 1 The original Cox Maze III is no longer widely performed due to its complexity and high pacemaker implantation rates with earlier versions. 1 The Cox Maze IV represents a less invasive modification using radiofrequency or cryoablation to replicate the surgical lines of ablation instead of the traditional cut-and-sew approach. 1, 2

Clinical Efficacy

Success rates are impressive but vary by patient population:

• 95% freedom from AF at 15 years in patients undergoing concomitant mitral valve surgery 1, 2
• 89-93% freedom from atrial tachyarrhythmias at 3-12 months in Cox Maze IV procedures 1, 2
• 78% off antiarrhythmic drugs at 12 months 1, 2
• Other studies report success rates around 70%, reflecting variation in patient selection and follow-up methods 1

Risks and Complications

Operative mortality is less than 1% when performed as an isolated procedure, but increases to approximately 2% when combined with other cardiac surgeries. 1, 2 Major complications include:

• Permanent pacemaker requirement in 3-10% of patients, particularly with right-sided lesions 1, 2
• Recurrent bleeding requiring reoperation 1, 2
• Atrioesophageal fistula (rare but potentially fatal) 1, 2
• Delayed atrial arrhythmias, especially atrial flutter 1, 2
• Transient fluid retention due to reduced atrial natriuretic peptide release 1, 2
• Impaired atrial transport function (though >90% regain function postoperatively) 1

Current Clinical Application

The American College of Cardiology provides a Class IIa recommendation for AF surgical ablation in selected patients undergoing cardiac surgery for other indications, and a Class IIb recommendation for stand-alone procedures in highly symptomatic patients not well managed with other approaches. 1, 2

Despite high success rates, the traditional maze operation has not been widely adopted outside of patients already undergoing cardiac surgery due to the need for cardiopulmonary bypass. 1, 2 Only 5.3% of AF surgical ablations recorded in the Society of Thoracic Surgeons database from 2005-2010 were stand-alone procedures. 1, 2

Important Clinical Caveats

Atrial transport function recovery: Echocardiographic studies demonstrate that left and right atrial transport function is regained postoperatively in more than 90% of patients. 1 This is a critical distinction from catheter ablation approaches that may not preserve atrial mechanical function as effectively.

Anticoagulation considerations: When combined with left atrial appendage obliteration, postoperative thromboembolic events are substantially reduced. 1 However, patients with stroke risk factors should continue anticoagulation based on their CHA2DS2-VASc score regardless of apparent procedural success.

Patient selection: The procedure is typically reserved for patients with AF refractory to medical treatment, history of systemic embolism, contraindications to anticoagulation, or those already undergoing cardiac surgery for other indications. 2