The Cryosurgical Maze Procedure

Patient Selection

In the cryosurgical approach the atrial incisions of the standard maze procedure are replaced by linear cryolesions. The cryosurgical procedure results in a shorter and technically less demanding procedure. Whether surgical incisions or cryolesions are used to perform the Maze procedure, it is essential to create transmural atrial lesions to prevent late recurrence of atrial fibrillation.  Since the cryolesions actually can be observed as they develop it is a simple matter  to determine when transmural ablation has or has not occurred. 

The cryosurgical surgical technique described herein has become our standard procedure for the treatment of all types of medically refractory atrial fibrillation with and without associated acquired or congenital heart diseases.

Operative Steps

Figure 1

The cryosurgical maze procedure can be performed through a standard median sternotomy or via a small 7-cm right anterior thoracotomy for the minimally-invasive approach (not included in this presentation).  A variety of cryoprobes are used, the most important being a rigid straight probe which that can create linear cryolesions 5-7 cm in length.  Two of these linear cryoprobes are preferable for performing certain aspects of the cryosurgical Maze procedure.   A 25 mm round cryoprobe and a 15 mm right angle probe are also helpful in most cases (Cooper Surgical, Shelton, Connecticut USA- [Figure 1]).

Right Atrial Cryolesions:

The right atrial cryolesions can be performed without the use of cardiopulmonary bypass, but after full heparinization.

A purse-string suture is placed in the posterior-lateral right atrium and a linear cryoprobe is inserted through the purse-string into the inside of the right atrium.  A cryolesion is placed in a cephalad direction into the postero-lateral aspect of the superior vena cava (SVC) orifice and away from the SA node [Figure 2].  Using the same purse-string suture, a second cryolesion is placed into the orifice of the inferior vena cava (IVC) to complete the longitudinal lesion from the SVC to the IVC [Figure 3]. Through the same purse-string a third lesion is made along the lateral wall of the right atrium down to inter-atrial septum and the right pulmonary veins is placed [Figure 4 - closed arrow]. The first purse-string suture is tied and a second purse-string is placed near the AV groove of the free-wall of the right atrium. The cryoprobe is inserted through this second purse-string suture to create the linear “T” lesion across the lower right atrium [Figure 5]. Using the same purse-string suture, the cryolesion is extended down to the level of the tricuspid valve annulus at the junction of the anterior and posterior commissures [Figure 5 and 6 – closed white arrows].

Figure 2	Figure 3	Figure 4
Figure 5	Figure 6

The second purse-string is then secured and will be used for insertion of  the coronary sinus catheter, later in the procedure. The second purse-string suture is then tied and a third purse-string suture is placed in the right atrial appendage.  A lateral right atrial cryolesion is placed from the tip of the atrial appendage towards the previously placed “T” lesion, leaving at least 3 cm between its tip and the “T” cryolesion. Using the same purse-string suture in the right atrial appendage, a cryolesion is placed from the appendage down to the antero-medial tricuspid valve annulus at the septal commissure [Figure 6 – open arrows].  Since this lesion, if placed incorrectly, can be approximate to the A-V node, it is sometimes preferable to initiate cardiopulmonary bypass at this point and open the right atrial appendage so that the precise placement of this last right atrial cryolesion can be made under direct vision.  However, it is our standard practice to place this lesion before initiating bypass.

Left Atrial Cryolesions:

 
After the completion of the right atrial cryolesions, cardiopulmonary bypass is instituted.  For placement of the left atrial cryolesions we use slightly different techniques for patients having an isolated Maze procedure and those who are also undergoing mitral valve surgery.  The technique also varies in a few details depending upon whether the surgical approach is through a median sternotomy or a small right thoracotomy. 

The inter-atrial groove is dissected completely and the right superior and right inferior pulmonary veins are dissected free circumferentially. One linear cryoprobe is placed posterior to the right pulmonary veins as they enter the left atrium.  A second identical cryoprobe is placed on the anterior surface of the veins in the same plane.  The cryoprobes are then “squeezed” together firmly and two-minute cryolesion is created by freezing with both probes. This result is a transmural cryolesion around the orifices of the right pulmonary veins. A left ventricular vent is placed via the right superior pulmonary vein [Figure 7]

Figure 7

The ventricular apex is then retracted in a cephalad direction out of the pericardium using the left hand to expose the intra-pericardial segments of both left pulmonary veins. After minimal dissection around the left pulmonary veins, the two cryoprobes are “clamped” around both left pulmonary veins as they enter the left atrium posteriorly and cryothermia is applied to both probes.  The result is a circumferential, transmural cryolesion around the orifices of the left pulmonary veins [Figure 8]. 

Figure 8

A purse-string suture is then placed in the tip of the left atrial appendage and a linear cryoprobe is inserted inside the atrial appendage with its tip placed into the orifice of the left superior pulmonary vein to create a linear lesion. The cryoprobe is then withdrawn and the left atrial appendage is excluded from the rest of the left atrium by stapling or suturing the base of the appendage from the outside [Figure 9]. 

A standard left atriotomy is performed after placement of the aortic cross clamp and instituting cardioplegic arrest. A lesion connecting the inferior right and left inferior pulmonary veins is performed using the linear cryoprobe [Figure 9]. Creating a lesion from the pulmonary veins connecting line down to the posterior mitral valve annulus with the linear cryoprobe and ablation of the coronary sinus with the 15mm right angle probe concludes the procedure [Figure 10- arrows]. Cryoablation of the coronary sinus is performed on the epicardial surface [Figure 10- open arrow].

Figure 9	Figure 10

This technique decreases the aortic cross-clamp time by reducing the number of cryolesions that are necessary after opening the left atrium to three for those that are marked with arrows in figures 9-10.

If an isolated cryomaze procedure is being performed the left atriotomy is then closed, and the procedure completed; however, if a combined mitral valve procedure is required, the valve surgery is performed at this time.

Postoperative management

Urine Output

• Maintain Urine output at 1.5-2 cc/kg/h using IV furoseamide drip to reduce the risk of fluid retention for the first 48 hours.
• I.V furoseamide at 1 mg/kg/day  followed by PO Lasix for 4 weeks  
• Spironalactone 25 mg QD upon extubation and for 6 weeks

Arrhythmia Control

• Potassium and magnesium levels should be maintained in the higher range of normal
• No prophylaxis for patients coming out of the OR on nodal rhythm or slow sinus rhythm. When patients resume sinus rhythm > 60 bpm, start IV amiodarone and convert to PO only in patients with left atrium larger than 6cm or history of RHD for 6 months. Holter ECG should be ECG performed to assess cardiac rhythm following the cessation of antiarrhythmic treatment
• Postoperative atrial fibrillation should be treated aggressively. Rate control at first and electrical cardioversion if needed.

Nodal rhythm management

• No antiarrhythmic drugs!
• Atrial pacing
• Aggressive diuresis
• Permanent pacemaker implantation not before postoperative day 7.

Anticoagulation/antiaggregates

• Coumadin treatment
  • Life long for patients with indication for anticoagulation
  • 3 months postoperatively for patients with preoperative CVA/TIA/RIND
  • Patients with recurrent atrial fibrillation should be treated until sinus rhythm resumed
• Aspirin for patients that don’t meet the indications for coumadin
  

Tips & Pitfalls

• If TEE documents thrombus in the left atrium or PFO no attempts of beating heart cryomaze should be made. Following aortic cross clamp the left atrium should be opened and the thrombus should be excluded as the first step and PFO closure should be performed when indicated.
• Cryolesions should be applied for 2 minutes  after the ice ball has been formed.
• Be aware of cryolesions close to the phrenic nerve especially that of the right one when ablating down to the IVC and in redo cardiac surgery.
  

References

1. JL. Cox, N Ad, T. Palazzo. Impact of the Maze Procedure on the Stroke Rate in Patients  with atrial fibrillation. J. Thorac Cardiovasc Surg. 1999;118:833-40.
2. JL Cox, N. Ad. New surgical and catheter-based modifications of
   the Maze procedure. Seminars in Thoracic and Cardiovascular Surgery
   2000;12:68-73
3. Niv Ad, Young D. Kim, Martin A. Makary, et. al. Prophylactic Diuresis with continuous Furosemid drip following the Maze procedure reduces the incidence of fluid retention. J Thorac Cardiovasc Surg. 2002;123:232-36.
4. Niv Ad, Young D. Kim, Josseph Verbalis, James L. Cox. The Effect of the Maze Procedure on the Secretion of Arginine-Vasopressin and Aldosterone. J Thorac Cardiovasc Surg 2003 126: 1095-1100.