Volume 14, Issue 3 , Pages 208-223, Autumn 2009
Minimally Invasive Bi-Atrial CryoMaze Operation for Atrial Fibrillation
Article Outline
The Cox maze III operation (CMIII) pioneered by Dr. Cox remains the gold standard for treatment of atrial fibrillation (AF); however, it has yet to gain widespread application due to its perceived invasiveness and complexity. The “holy grail” for AF therapy is a safe, minimally invasive procedure that can provide the same freedom from AF as the CMIII operation, which has achieved >96% freedom from AF at >5 years mean follow-up. 1
Patients prefer a sternotomy-sparing approach, which offers cosmetic advantages and may allow for earlier recovery of normal function. However, these objectives should not affect the primary objective of eliminating AF and minimizing the risk of late thromboembolism. With the introduction of catheter-based unipolar radiofrequency ablation (RFA), interventional treatment of AF has become increasingly popular. 2 However, catheter-based techniques are often laborious and time-consuming and most results have been disappointing. Unipolar RFA has been found to be a potentially dangerous energy source whether used percutaneously or surgically, with development of fatal left atrial to esophageal fistulas in both instances. 3 In addition, catheter-based RFA cannot create a complete left atrial lesion set. To offer patients >90% freedom from AF and cerebral thromboembolism, pulmonary vein isolation alone is likely to be inadequate. Despite the work of Haissaguerre and coworkers, 4 the experience from the Cleveland Clinic has demonstrated that the lesion from the pulmonary veins to the mitral valve annulus is very important and reduced their rates of recurrent AF from ∼40% to ∼20% at 1 year. 5 This may explain why most reports of long-term follow-up after percutaneous AF ablation show only 70% to 80% freedom from AF. In addition, and perhaps more importantly, the left atrial appendage (LAA) is left open when using a percutaneous approach, thereby leaving patients with the potential for thromboembolism, as ∼90% of left atrial thrombus is felt to originate from the LAA. 6 At this moment, percutaneous treatment of AF remains an imperfect means of managing patients with AF.
With the introduction of multiple new energy sources intended to simulate “cut and sew” lesions, there is renewed interest in surgical AF ablation. Apart from cryothermy, all of the new energy sources currently in use for AF ablation (unipolar or bipolar RFA, microwave, high-frequency ultrasound, and laser) are limited by their potential to damage adjacent structures, such as the atrial endothelium, esophagus, coronary arteries, or valvular tissues. Cryothermy has always been an important part of the CMIII operation 7 and is the only energy source currently available that can safely re-create all of the lesions of the CMIII operation, including the lesions down to the mitral and tricuspid annuli.
Traditional cryothermy was delivered by a liquid nitrogen-cooled probe (Frigitronics; CooperSurgical Inc, Trumbull, CT), which achieved temperatures of approximately −60°C, with probes that were not very flexible. Current cryothermy technology uses argon gas as the refrigerant (CryoMaze Probe; ATS Medical, Plymouth, MN) 8 and provides faster cryothermy to the tissues, with temperatures as low as −160°C, delivered by a flexible, linear probe. Studies of animal tissues have demonstrated effective transmural lesion creation after application of the Cryocath probe to cardiac tissues of up to 4 mm thickness for 60 seconds (Surgifrost Chronic Dosing Study, communication from Cryocath). In addition, cryothermy has an excellent safety profile, causing less endothelial damage than unipolar RFA (noted by an absence of char formation), with no reports of esophageal injury or left atrial fistula formation. Finally, the CryoMaze probe is well suited to a minimally invasive or robotic approach because it is a flexible, linear device with a 4-mm diameter, available in lengths of 6 to 10 cm.
We believe that the other critical factor affecting long-term freedom from AF after surgical ablation is the lesion set. Although there is a large interest in minimally invasive techniques that apply energy epicardially, these approaches suffer from an inability to reliably create the lesion from the pulmonary vein orifices to the mitral valve annulus—a lesion that is important for prevention of left atrial flutter and recurrent AF postoperatively, as noted by the Cleveland Clinic experience. 5 This is the reason our technique involves cardiopulmonary bypass, cardiac arrest, and endocardial lesions.
Contraindications to a minimally invasive approach include previous right lung surgery or dense adhesions, forced expiratory volume <1 L, or significant peripheral vascular disease. If a patient requires concomitant coronary artery bypass or aortic valve surgery, the CryoMaze operation can still be performed through a sternotomy incision.
We present our technique of the minimally invasive CryoMaze, along with early results in a small group of patients with isolated AF.
Operative Technique
Figure 1.
(A) The patient is positioned supine with a slight 30° left lateral decubitus position. The right arm is wrapped in a flexed position, beside the patient, to expose as much of the axilla as possible. Double-lumen endotracheal intubation is employed and transesophageal echocardiography (TEE) is used in each patient in addition to other standard monitoring devices. A 3- to 4-cm minithoracotomy incision is created in the right inframammary crease and the pleural space is entered through the fourth intercostal space (ICS). (B) A soft-tissue retractor (Edwards, Irvine, CA) is placed with minimum rib spreading to expose the mediastinum. The pericardium is opened 3 cm anterior to the phrenic nerve and pericardial and diaphragmatic retention sutures, 2-0 Ticron (US Surgical Corp, Norwalk, CT), are exteriorized as far posteriorly as possible to maximize intrathoracic working space. A 5-mm videoscope (Storz, Tuttlingen, Germany) is placed directly through the chest incision or through a 5-mm stab wound posterior to the incision in the fourth ICS to facilitate deep intracardiac visualization. PC = peripheral cannulation; MT = minithoracotomy.
Figure 2.
Peripheral cannulation is achieved by exposing the femoral vessels through a 2-cm horizontal groin incision. Only the anterior surfaces of each vessel are exposed and 4-0 Prolene purse-string sutures (Johnson and Johnson Health Care Systems, Piscataway, NJ) are placed for cannulation. The patient is systemically heparinized. Using a Seldinger guide-wire technique with TEE guidance, we routinely perform right femoral arterial (17-19 Fr) and venous cannulation (21 Fr) using Bio-Medicus thin-wall cannulas (Medtronic-BioMedicus, Eden Prairie, MN). The venous cannula is guided to rest at the mid-right atrium level. In addition, a right internal jugular venous drainage line (15-17 Fr) is placed by the anesthesiologist in the distal superior vena cava well above the superior cavoatrial junction, before central line placement. Kinetic-assisted venous drainage is used in every case. Cardiopulmonary bypass (CPB) is initiated and the patient is cooled to 28°C.
Tapes are place around the superior and inferior vena cava in preparation for the right-sided lesions. a. = artery.
Figure 3.
A long antegrade cardioplegia/aortic root vent needle (Medtronic) is placed in the ascending aorta. (A) A small stab wound is made as far superior and posterior as possible in the axilla to allow the Chitwood transthoracic aortic cross-clamp (Scanlan International, Minneapolis, MN) to be passed through the second ICS. (B) It is then applied through the transverse sinus with the concave aspect of the blades (C) facing cranially. Great care is taken to avoid injury to the pulmonary artery, left atrial appendage, and left main coronary artery. After the aorta has been cross-clamped, cold, intermittent, antegrade blood cardioplegia is used for myocardial protection. a. = artery; SVC = superior vena cava.
Figure 4.
The surgical field is flooded with CO2 via a 14-Fr angiocatheter, introduced through the right chest wall. The interatrial groove is developed with electrocautery and the left atrium is opened. The oblique sinus is developed with sharp or blunt dissection, and the left atriotomy incision is extended caudad posterior to the inferior vena cava, and anterior to the right inferior pulmonary vein. A weighted-tip DLP sump catheter (Medtronic) is placed via a separate stab incision on the chest wall near the aortic cross-clamp, through the atriotomy to rest in the left superior pulmonary vein. This allows the pulmonary vestibule to be free of pooled blood. Exposure of the left atrium can be facilitated with a handheld basket-type retractor or with a fixed blade retractor system (Estech, Danville, CA). A 5-mm videoscope (Storz) can be passed through the incision for assisted vision or through a separate port incision as shown in Figure 1A. In general, this minimally invasive approach provides superior visualization of all deeper cardiac structures, with minimal surgical exposure. SVC = superior vena cava.
Figure 5.
All lesions are created by applying the CryoMaze Probe (ATS Medical) for 2 minutes directly to myocardial tissue with temperatures reaching −140°C to −160°C. Following lesion creation, the probe is thawed from the surrounding tissue by administering cold saline for the left-sided lesions and room temperature saline for the right-sided lesions. The left-sided lesions are created under cardiac standstill and the right-sided lesions are created on the beating heart, while rewarming.
The left-sided endocardial lesions are performed first. The pulmonary vestibule is isolated as a single island with a wide box lesion around it. The first cryo-lesion is performed on the inferior aspect of the pulmonary vestibule along the atrial ridge that separates the pulmonary vestibule from the mitral valve. PV = pulmonary vein.
Figure 6.
The next cryo-lesion extends around the lateral aspect of the left pulmonary veins, between the orifice of the LAA and the left superior pulmonary vein. Great care is taken to avoid skip lesions by ensuring complete contact between the probe and atrial tissue along the entire lesion and crossing well over the last lesion to form a connection. PV = pulmonary vein.
Figure 7.
The box lesion is completed by a cryo-lesion across the superior aspect of the pulmonary veins that connects with the left atriotomy incision, which is the only non-cryo-lesion of the pulmonary vein isolation. In general, the box lesion can be constructed with 2 or 3 cryo-lesions; however, if the left atrium is particularly large and redundant, more lesions may be required.
We create an additional lesion from the pulmonary vein isolation box to the LAA if this area was not completely ablated during the creation of the pulmonary vein isolation box. PV = pulmonary vein.
Figure 8.
An endocardial lesion is then created to join the box lesion around the pulmonary veins to the mitral valve annulus at the level of P3. By extending this lesion medially toward P3, the lesion can be created while avoiding circumflex coronary artery injury. Most of our recurrent AF after the CryoMaze operation, as identified in the electrophysiology laboratory, has originated from this lesion line incompletely crossing the annulus. As a result, we routinely place the Cryo probe across the entire mitral annulus on to the posterior leaflet. We have not experienced any injury to the leaflet with appropriate thawing of the leaflet tissue. PV = pulmonary vein.
Figure 9.
The final left atrial lesion is an epicardial lesion across the coronary sinus, via the oblique sinus. As demonstrated in the drawing, this lesion ensures complete transmurality at the mitral valve annulus. The videoscope can be helpful to allow accurate placement of the CryoMaze probe across the coronary sinus. We place a suction catheter posterior and lateral to the CryoMaze probe to prevent the probe from freezing the oblique sinus closed, making it difficult to extricate the probe, and to protect the left phrenic nerve, which may lie just adjacent to probe. It is crucial that this lesion incorporates the coronary sinus and that it is parallel and right on top of the endocardial lesion toward P3. Alternatively this lesion can be created first and a mark in the left atrial endocardium with methylene blue could be made to delineate the location for the endocardial lesion extending toward P3 to have both lesions on top of each other.
Figure 10.
The LAA is routinely closed as part of the CryoMaze operation, unless there are significant pericardial adhesions keeping the appendage patent, for example, during reoperative cardiac surgery. The LAA is closed in a 2-layer fashion using a 3-0 Gore-Tex (W.L. Gore & Associates, Flagstaff, AZ) suture. The suture bites should be within the thicker tubular portion, away from the trabeculated portion, of the LAA to allow complete appendage obliteration without tearing.
The left atrium is then de-aired and closed with a running 3-0 Prolene suture. The transthoracic aortic cross-clamp can now be removed; rewarming can begin and the right-sided lesions can be performed with the heart beating.
Figure 11.
The intercaval lesion is created between the superior vena cava and the inferior vena cava, avoiding both the sinoatrial node as well as the left atriotomy incision. Alternatively, the intercaval lesion could be created at the beginning of the procedure, before cardiac arrest and opening of the left atrium, and thus obviating the potential for freezing over your left atriotomy suture line. This lesion can usually be created with 1 freeze but may require 2 freezes. Care is taken at this point to avoid contact between the CryoMaze probe and the phrenic nerve. A small surgical sponge could be placed at the peri-cardio-caval reflections to protect the phrenic nerve.
Figure 12.
We recommend performing a small vertical atriotomy as an inverted T connecting to the intercaval lesion after securing the caval tapes. Two endocardial lesions are created, 1 toward the tricuspid annulus at the 2 o'clock position and another between the right atrial appendage and the tricuspid annulus at the 10 o'clock position.
Figure 13.
Alternatively, a puncture site is made in the midbody of the right atrium and an endocardial lesion is created along the endocardial surface of the right atrium out to the tricuspid valve annulus anteriorly. This lesion is performed on full cardiopulmonary bypass with the atrium emptied, ensuring contact between the endocardium and the CryoMaze probe. The right atrium is then filled to thaw the probe and separate it from the tissue. Caval tapes are usually not required.
The atriotomy incision shown in Figure 12 is replaced by an epicardial cryolesion, shown in Figure 13 as the second lesion connecting between the tricuspid lesion and the intercaval lesion, with the tip of the catheter aiming toward the oblique sinus. After completion of this lesion, a 4-0 Prolene purse-string is placed to close the small right atrial stab wound.
Temporary ventricular and atrial pacing wires are placed, and then the patient is weaned from CPB. After de-airing is confirmed by TEE, the vented cardioplegia cannula is removed and the purse-string is secured. Once hemostasis of the suture lines has been achieved, the protamine is administered, and the femoral artery and vein are decannulated.
Postoperative Management
Patients are loaded with intravenous amiodarone over the first 24 postoperative hours (1 mg/min IV × 6 hours, then 0.5 mg/min IV × 18 hours) and then switched to oral amiodarone. Amiodarone is not administered, or is discontinued, in patients with bradycardia (heart rate <60), heart block, or evidence of adverse reaction/toxicity. Electrical cardioversion is attempted in the operating room if the patient is in AF after discontinuation of CPB, or if he/she is hemodynamically unstable in the recovery period. All patients are also restarted on warfarin therapy once the pacing wires and chest tubes have been removed, to a target INR of 2 to 3.
Patients are routinely monitored with CardioNet monitoring (CardioNet, Conshohocken, PA), a continuous loop recorder, for 1 week at 3, 6, and 12 months following surgery. We feel this is more accurate than electrocardiogram “spot” checks and is absolutely necessary to determine the long-term efficacy of any AF ablation procedure. If CardioNet monitoring demonstrates sinus rhythm at 3 months, after being off amiodarone for 1 month, warfarin therapy is discontinued. Monitoring is then repeated at 6 months and 1 year after the initial procedure as well as yearly thereafter or in the event of symptom development.
Conclusions
At the East Carolina Heart Institute, it was our goal to develop an AF operation that offered a minimally invasive approach, while at the same time allowing for re-creation of the CMIII lesions, including closure of the LAA. Between September 2003 and August 2008, we performed a total of 333 CryoMaze operations; 71 were performed for lone AF and 162 were performed as a concomitant procedure, most commonly with mitral valve surgery. Every 1 of the stand-alone procedures was performed using the minimally invasive techniques described here without sternotomy conversions.
Our initial results in the stand-alone group demonstrated restoration of sinus rhythm in approximately 88% (off anti-arrhythmic medications and warfarin) with at least 6-month follow-up on every patient.
The CryoMaze probe system may combine greater safety and efficacy, along with the added advantage of easy applicability via a small unilateral inframammary incision. Further studies of randomized patients are necessary to determine the optimal treatment of AF—a therapeutic option that will provide patients with a minimally invasive, yet safe and highly effective treatment of their illness.
References
- The Cox maze III procedure for atrial fibrillation: long-term efficacy in patients undergoing lone versus concomitant procedures. J Thorac Cardiovasc Surg. 2003;126:1822–1828
- . Catheter ablation of supraventricular arrhythmias: state of the art. PACE. 2004;27:125–142
- Esophageal perforation during left atrial radiofrequency ablation: is the risk too high?. J Thorac Cardiovasc Surg. 2003;125:836–842
- Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins. N Engl J Med. 1998;339:659–666
- Surgery for permanent atrial fibrillation: impact of patient factors and lesion set. Ann Thorac Surg. 2006;82:502–514
- Is left atrial appendage occlusion useful for prevention of stroke or embolism in atrial fibrillation?. Z Kardiol. 2002;91:376–379
- Modification of the maze procedure for atrial flutter and atrial fibrillation II (Surgical techinique of the maze III procedure). J Thorac Cardiovasc Surg. 1995;110:485–495
- A new cryoprobe for intraoperative ablation of atrial fibrillation. Ann Thorac Surg. 2004;77:1460–1462
W. Randolph Chitwood, Jr reports consulting/advisory fees from ATS Medical and royalties from Scanlan. Evelio Rodriguez reports consulting/advisory fees from CardioNet Inc. and ATS Medical.
PII: S1522-2942(09)00093-2
doi:10.1053/j.optechstcvs.2009.06.009
© 2009 Elsevier Inc. All rights reserved.
Volume 14, Issue 3 , Pages 208-223, Autumn 2009
