Cox-Maze IV Procedure Using Bipolar Radiofrequency Energy

Indications for surgical treatment of atrial fibrillation

Our clinical indications for treatment of atrial fibrillation (AF) reflect the guidelines published by a joint panel of expert cardiologists, electrophysiologists and cardiothoracic surgeons who formed the Heart Rhythm Society (HRS) Task Force. Ralph J. Damiano Jr., MD, and Bruce D. Lindsay, MD, of the Washington University Center for Atrial Fibrillation, were co-authors of these guidelines. This consensus statement outlines recommendations for catheter and surgical ablation of AF. The HRS Consensus Statement (pdf) includes the policy for the surgical ablation of AF.

Lone atrial fibrillation

The main indication for surgical treatment of AF is intolerance of the arrhythmia in patients who have failed medical therapy. Patients with paroxysmal (intermittent) atrial flutter or fibrillation usually have more symptoms than those with continuous or permanent AF. Major symptoms include labored breathing on exertion, becoming easily fatigued, lethargy, malaise and a general sense of uneasiness. Patients with lone AF should receive a trial of medical therapy before surgery. A significant number of patients with AF are referred to surgery because of side effects or intolerance of antiarrhythmic drugs.

The development of tachycardia (rapid heartbeat)-induced cardiomyopathy (TIC) in patients with AF is another important indication for surgery. TIC is a condition characterized by atrial or ventricular dysfunction resulting directly from increased heart rates in an otherwise structurally normal heart. Untreated TIC can lead to heart failure. It is extremely important for doctors to recognize this condition in patients with uncontrolled AF since TIC is reversible if normal sinus rhythm is restored surgically.

Another consideration for surgery is when patients are no longer advised to use long-term anticoagulation, such as those patients who have suffered intracranial hemorrhage while on warfarin. Up to one third of patients screened for participation in prior clinical trials on the use of warfarin in AF were deemed unfit for chronic anticoagulation, primarily because of a high perceived risk for bleeding.

In addition, patients with chronic AF who have cerebrovascular accidents despite adequate anticoagulation should be considered for surgical treatment. Anticoagulation with warfarin reduces the risk of ischemic and hemorrhagic stroke by more than 60% in patients with AF, but does not eliminate this complication.

Atrial fibrillation combined with other conditions

Virtually all patients with AF who undergo elective cardiac surgery (coronary artery bypass grafting, valve repair/replacement) should be strongly considered for a Cox-Maze procedure as part of the same operation. Recent studies have shown that adding a Maze procedure can decrease the risk of cardiac- and stroke-related deaths in these patients. The only patients with AF who should not undergo a Maze procedure along with another heart operation would be high-risk patients who have tolerated their AF well and have not had problems with anticoagulation.

How the Cox-Maze IV procedure was developed

The traditional Cox-Maze operation achieves success (cure of atrial fibrillation) in more than 90% of patients; however, it is a technically difficult procedure and therefore is not performed frequently. Surgeons also must temporarily stop the heart and use a heart-lung machine to take over the heart’s role of circulating blood in order to make the incisions. Not all patients are healthy enough to endure the operation.

In order to simplify the operation, groups around the world began replacing many of the surgical incisions of the Cox-Maze procedure with linear lines of ablation. These ablations were created using a number of energy sources including radiofrequency energy, microwave, laser, high-frequency ultrasound and cryoablation. These new techniques simplified the operation by replacing the time-consuming traditional cut-and-sew Cox-Maze procedure with the simpler application of a probe or clamp. The ablation energy from these devices is driven through the atrial muscle, killing the normal tissue and creating a full-thickness scar that blocks the electrical impulse. Thus, it has the same function as a surgical incision. Unfortunately, many of the new technologies were not successful in reproducibly creating a full-thickness scar. This led many of the new procedures to achieve much lower success rates than had been obtained with the traditional cut-and-sew Cox-Maze III procedure.

At Washington University School of Medicine, extensive laboratory studies of all the new technologies were performed. The only technology to reproducibly and reliably create full-thickness scar in animals was the bipolar radiofrequency ablation clamp.

Chronic animal studies showed that ablation lines created with these devices were able to block electrical impulses both at the time of creation and 30 days later. These ablation lines were effective at stopping atrial fibrillation.

The bipolar radiofrequency device is a clamp with electrodes imbedded in the jaws. The clamp is applied to atrial tissue. Energy is delivered through the closely approximated electrodes embedded in the jaws of the clamp. Specially derived algorithms are used to tell the surgeon when the energy has created a full-thickness scar. Our excellent laboratory results using these clamps led to the development of a modification of the original cut-and-sew procedure, which was first performed in 2002. In this procedure, called the Cox-Maze IV, many of the lesions of the conventional version are replaced with linear lines of ablation using bipolar RF energy. Our experience with the Cox-Maze IV procedure reported comparable success rates to the Cox-Maze III procedure (traditional surgical procedure) with freedom from AF at last follow-up of greater than 90 percent.

The length of the operation is noticeably reduced using the Cox-Maze IV procedure. Traditional procedures take, on average, 92 minutes to perform, while procedures employing the new approach take only an average of 41 minutes. The reduced operation time has resulted in fewer complications and shorter hospital stays.

Minimally invasive approach

We also perform Cox-Maze IV procedures by making a small, right-sided chest incision and avoiding the traditional median sternotomy incision down the center of the breast bone. This minimally invasive approach offers a more cosmetically appealing alternative to a full Cox-Maze procedure.

After the Cox-Maze IV procedure, the majority of our patients no longer need blood thinners or heart rhythm medications. They can enjoy a normal life.

The advancements in ablation technology developed in our laboratory, replacing the traditional cut-and-sew procedure, have been adopted around the globe. This has greatly simplified the procedure and increased its use.