Since April 1992, we have used exclusively the Maze-III procedure for the treatment of medically refractory atrial fibrillation. During the past 3 years, we have developed and refined a minimally invasive technique for performing the Maze-III procedure, which was used in over 70% of our patients in 1999. As with the standard Maze-III procedure, the objectives of the minimally invasive procedure remain the cure of atrial fibrillation, the restoration of atrioventricular synchrony, and the resumption of atrial contraction. How- ever, additional objectives of the minimally invasive procedure include shortened length of time in the intensive care unit, shorter hospitalization time, less perioperative morbidity, quicker recuperation, de- creased costs, and improved cosmesis.

SURGICAL TECHNIQUE

1- The patient is positioned on the operating table in the supine position with a slight left rotation. We usually put a single towel roll length-wise under the posterior right rib cage. The right arm is depicted in this drawing as being pulled upward. Actually, the arm is bent at the elbow and tucked alongside the right edge of the table so that good access to the axilla is available. The patient is intubated with a double-lumen endotracheal tube.
The right chest is entered through a 7 -cm right sub mammary incision placed in the mammary fold and centered in the nipple line. The chest will be entered through the fourth intercostal space, which is usually slightly cephalad to this incision. A small stab wound is placed approximately 6 to 8 cm caudad and posterior to the sub mammary incision in the same interspace. Another small stab wound is placed 1 or 2 interspaces directly below the sub mammary incision.
The right femoral artery and vein are isolated through a Small (3 - to 4 - cm) longitudinal incision in the right groin.

2 The right lung is def1ated by occluding the right branch of the double-lumen endotracheal tube. A Tuffier retractor is inserted in the fourth intercostal space. We use a wide malleable retractor underneath the lower blade of the Tuffier retractor to retract the dome of the right hemi diaphragm downward. The pericardium is opened longitudinally 3 to 5 cm anterior to the right phrenic nerve. Appropriate traction sutures (3-0 silk) are placed in the lower edge of the pericardium and brought out through the chest wall as depicted. Small clamps are placed on the sutures at the level of the skin to hold tension on these pericardial sutures. The anterior edge of the pericardium is sutured to the inside of the chest wall anteriorly.

3 The patient is heparanized and the right femoral artery and vein are cannulated. The tip of the femoral vein venous return cannula is positioned into the inferior vena cava (IVC) just below the level of the diaphragm (See Fig 4). The positioning of the venous return cannula can be expedited and confirmed by manual palpation of the right atrium and intrapericardial IVC during advancement of the cannula up the IVC system,
The arterial cannula is connected to the heart-Lung machine. The venous return cannula is connected in a "Y" fashion to the heart-Lung machine with an additional limb that is later connected to the superior vena cava (SVC) cannula.

4 The SVC and IVC are first freed of surrounding connective tissue and then encircled with Rummel tourniquets. Three size-4-0 monofilament stay sutures are placed superficially in the SVC just above its junction with the right atrium. These stay sutures (not shown) are used for traction during placement of the SVC cannula. A 3-0 monofilament purse-string suture is placed in the SVC and passed through a Rummel tourniquet.
A size-28 right-angled venous return cannula is passed through the posterior stab wound in the chest with its tip positioned near the purse-string suture. With traction being placed on the 3 stay sutures (anterior, posterior, and near the right atrial junction), the SVC is opened with a long-handle knife (number 11 blade) within the purse-string suture. The venous return cannula (with its proximal end clamped) is quickly inserted into the SVC and the purse-string is tightened around it. Care should be taken to be certain the tip of the cannula is not in the azygous vein.
The Rummel tourniquet is brought out through through same posterior stab wound and tied to the venous return cannula. The 2 loose Rummel tourniquets around the SVC and IVC are brought out the chest wall as diagrammed. The patient is now completely cannulated, and no cannulated or tourniquets that might interfere with surgical exposure are passing through the 7-cm sub mammary incision

5 The final step in preparation for the actual surgery is to place a cardioplegia cannula into the ascending aorta that is stabilized in position with another Rummel tourniquet. The cardioplegia cannula and its associated tourniquet are the only two space-occupying devices that pass through the 7 -cm sub mammary incision. .
This figure shows the Chit wood clamp that is used to cross-clamp the aorta later in the case after cardiopulmonary bypass has been established. It also shows the left ventricular vent that is positioned into the right superior pulmonary vein as soon as cardiopulmonary bypass has been initiated. Note that both of these devices are passed through the posterior stab wound to maintain maximum surgical exposure of the atria.

6 A small purse-string suture is placed in the posterior right atrium approximately mid-way between the SVC and IVC, and a slit is created within the purse-string suture with an 11 knife blade. A linear cryoprobe (3-mm diameter) is passed through the purse-string suture into the inside of the right atrium. The cryoprobe is then positioned as shown with its tip in the orifice of the SVC. Gentle upward traction is planed on the cryoprobe so that the right atrial free-wall that is to be cryoablated is stretched slightly over the shaft of the Cryoprobe. A transmural linear cryolesion is then created along this line by applying a temperature of -60°C for 2 minutes.

7 The posterior right atrial lesion between the SVC and the IVC is completed by using the same purse-string suture and cryoprobe to create the lower half of the long cryolesion down to the IVC, as shown.

8 A second purse-string suture is placed in the right atrial free-wall near the atrioventricular groove, and the linear cryoprobe is positioned as diagrammed. This cryolesion extends to the previously placed one between the SVC and the IVC.

9 The same purse-string suture and cryoprobe are used to extend this "T" lesion down to the level of the posterior-lateral tricuspid valve annulus. Because the distal end of this cryolesion must be placed blindly, we take care to be certain that the tip of the cryoprobe is well across the tricuspid valve annulus. This can be done in two ways. First, all patients have a transesophageal echo probe place soon after anesthesia induction, and it is frequently possible to document the position of the cryoprobe by this method. Secondly, the cryoprobe can be placed far enough across the valve to make contact with the thin part of the base of the right ventricle, just below the atrioventricular groove. When the cryothermia is then applied, the surgeon can see the "ice-ball" freezing through the base of the ventricle, documenting its transvalvular position.

10 A third purse-string suture is placed in the tip of the right atrial appendage. Linear cryolesions are placed both laterally and medially to complete the right-sided lesions of the Maze-III procedure.
It is important to place the medial cryolesion across the tricuspid valve annulus well anterior to the site of the His' bundle to prevent the inadvertent creation of heart block. This is best done placing the left index finger into the natural external groove between the aorta and the medial wall of the right atrium. The cryoprobe is then positioned anterior to the finger tip where there is no danger of injuring the more posteriorly located conduction system.

11 After completion of the right atrial cryolesions, cardiopulmonary bypass is instituted, and a left ventricular vent is placed via the right superior pulmonary vein (See Fig 5). The aorta is cross-clamped with a Chit wood clamp (See Fig 5), and the heal-t is arrested with ante grade warm blood cardioplegia. Once the heart is completely arrested, the cardioplegia temperature is decreased to 4°C and a total of 700 to 1,000 ml of cold blood cardioplegia is administered. Thereafter, cold blood cardioplegia is administered every 15 minutes during the aortic cross-clamp period.
A standard left atriotomy is performed. One linear cryoprobe is placed against the left side of the atrial septum through this left atriotomy. Another identical linear cryoprobe is passed through the original right atrial purse-string suture and placed against the right side of the atrial septum. The two cryoprobes are then '.pressed" together with their tips extending to the middle or lower portion of the fossa ovalis. This is determined blindly, and the only concern is of placing the cryoprobes too far down on the septum and creating heart block an extremely unlikely scenario. Both cryoprobes are then decreased to -60°C for 3 minutes.

12 The left atriotomy is then extended, but only slightly, in both the superior and inferior directions so that the inside of the entire left atrium can be seen. The right thoracotomy approach greatly enhances this view in comparison to the median sternotomy approach used for the standard Maze-III procedure.
Linear cryolesions are placed from outside the atrium as indicated so that the "ice-ball" can be documented to be transmural. These cryolesions should be placed for 2 full minutes at -60°C with The timing starting only when the "ice-ball" along the entire length of the cryoprobe has penetrated The full thickness of the atrial wall visually. The dotted lines show the positions where the cryolesions must be placed to completely encircle The pulmonary vein orifices and to accomplish circumferential ablation of the base of the left atrial appendage. The latter is accomplished using a 2.5-cm round cryoprobe placed directly into the orifice of the left atrial appendage. This results in the cryolesion extending down to the level of the pulmonary vein orifices, although this diagram depicts a noncryoablated space between the appendage orifice and the vein orifices. After circumferential cryoablation of the orifice of the left atrial appendage, it is closed from inside the atrium with a continuous 4-0 monofilament suture to prevent future embolization.
An endocardial linear cryolesion is then placed from the pulmonary vein-encircling cryolesion down to the level of the posterior mitral valve annulus.

13 A final epicardial cryolesion is placed down to the level of the mitral valve annulus taking care that it is positioned in exactly the same plane as the endocardial cyrolesion just completed (See Fig 12). During placement of this cryolesion, it is essential to hold the epicardial cryoprobe in position long enough to see the "ice-ball" penetrate to the endocardium. This assures that the coronary sinus has been cryoablated circumferentially in this plane. This completes the minimally invasive Maze-III procedure.
Between September 25, 1987 and August 1, 1999, we performed 345 total Maze procedures for the treatment of atrial fibrillation. The first minimally invasive Maze procedure was performed on March 1, 1996, and we have now performed a total of 60 Maze procedures by using minimally invasive techniques. Seventeen (28%) of those patients had concomitant mitral and/or tricuspid valve surgery, and 2 underwent simultaneous closure of an atrial septal defect. Three of the patients had the minimally invasive Maze procedure performed as a re-do cardiac operation.
The minimally invasive approach has resulted in a significant decrease in the time to extubation after surgery. In addition, the length of time in the intensive care unit and the length of stay in the hospital have both been decreased by using this new approach. Moreover,

Concomitant repair or replacement of the mitral and tricuspid valve can be performed at the same through the small incision. Thus, our experience the new minimally invasive, cryosurgical approach performing the Maze procedure for atrial fibrillate has been so encouraging that we now consider it to feasible alternative to the standard Maze procedure many patients with medically refractory atrial fibr tion.

From the Department of Thoracic and Cardiovascular Surgery, George.
University Medical Center, Washington, DC.
Address reprint requests to James L. Cox. MD. Professor and Chair Thoracic and Cardiovascular Surgery. Georgetown University Medical C 4PHC, 3800 Reservoir Rd NW, Washington. DC 20007.
Copyright @ 2000 by W.B. Saunders Company 1522-2942/00/0501-0005$10.00/0 doi:10.1053/oi.2000.5973