doi: 10.1161/01.cir.0000032883.55215.49
(Circulation. 2002;106:I-46.)
© 2002 American Heart Association, Inc.
Surgery for Valvular Heart Disease |
The Effect of Cryo-Maze Procedure on Early and Intermediate Term Outcome in Mitral Valve Disease: Case Matched Study
From the Department of Cardiovascular Surgery, National Cardiovascular Center, Osaka, Japan.
Correspondence to Junjiro Kobayashi, MD, Department of Cardiovascular Surgery, National Cardiovascular Center, 5-7-1 Fujishirodai, Suita, Osaka 565-8565, Japan. E-mail jkobayas{at}hsp.ncvc.go.jp
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Abstract |
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Background The maze procedure is an effective way to treat atrial fibrillation (AF) associated with mitral valve disease. In a last several years, cryoablation was substituted for atrial incision in many reports to simplify the maze procedure. However, there has been no comparative study to delineate the feasibility of the use of cryoablation.
Methods and Results We compared the early and intermediate-term results of the maze procedure including pulmonary venous isolation from the left atrium using cryoablation (CM) with our conventional (Kosakai) maze procedure (KM) including encircling incision around the orifices of pulmonary veins. One hundred and 10 pairs of patients were matched in the age, left atrial dimension >70 mm, duration of AF >0 years, previous cardiac surgery, mechanical valve implantation and concomitant aortic valve procedures. CM required significantly shorter cardiopulmonary bypass time (186±56 minute versus 214±47 minute, P=0.001) and aortic cross-clamp time (134±43 minute versus 144±37 minute, P=0.03) than KM with less chest tube drainage (590±353 mL versus 745±618 mL, P=0.02) for 12 hours after operation. The sinus rhythm restoration rate in CM group (85.4%) was comparable with KM group (86.4%) at discharge. In the late results, the actuarial freedom from recurrence of sustained AF at 3 years in CM group (97.7%) was not significantly (P=0.11) different from that in KM group (90.4%). The actuarial freedom from stroke at 3 years in CM group was 99.0%.
Conclusion The modification of the maze procedure including cryoablation for pulmonary venous isolation provided less aortic cross-clamp time and less amount of chest tube drainage with the comparable recovery and maintenance of sinus rhythm with KM. CM is a reliable and less invasive surgical option for the AF associated with mitral valve disease.
Key Words: mitral valve disease • maze procedure • atrial fibrillation • cryoablation
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Introduction |
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To eliminate atrial fibrillation (AF) and restore sinus rhythm after mitral valve operation prevents stroke,1,2 decreases the late mortality,2 and improves cardiac function with the recovery of atrial contraction2,3 and the quality of life.2,4 The conventional maze procedure requires large left atrial incisions and sutures, and prolongs cardiac ischemic time. Therefore, the conventional full maze procedure has a potential risk of postoperative complications, such as bleeding, low output syndrome and sick sinus syndrome.2
In a last decade, various modifications of the maze procedure have been developed by many surgeons.6–15 Most of these modifications include the sutureless interruption of the myocardial conduction in the left atrium especially for isolation of pulmonary veins (PV),6–11 which is the critical part as a trigger site of initiation of AF.17–19 The cryoablation is 1 of the common ways of substitution for atrial incision in the maze procedure6–8 and early results of these trials in small population were seemed to be acceptable.6–11 However, the rationale of cryoablation for PV isolation has not been proved because no comparative study has been previously reported.
In the present study, we examined the rationale of cryoablation for PV isolation by comparing the early and intermediate-term results of our conventional maze procedure.
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Methods |
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Patients
Between May 1992 and June 2001, 414 patients underwent the maze procedure associated with mitral valve operation. Since September 1998, 119 patients underwent cryo-maze procedure (CM), 244 underwent Kosakai maze procedure (KM) before introduction of CM, and 51 underwent the other modified maze procedure. The choice of procedure depended on the period when operation was performed. One hundred and 10 pairs of patients were matched. Only hospital survivors were assigned to this study. The matching variables were the age, the preoperative duration of AF >10 years, preoperative left atrial dimension >70 mm, the history of previous cardiac surgery, and concomitant aortic valve operation. These were reported to be negative predictive factors for regaining sinus rhythm after the maze procedure,12,13,16 procedural time or postoperative bleeding. The patients were selected from the preoperative and operative database except for the clinical results to exclude the bias. There was a significant difference in NYHA functional class in 2 groups. The incidences of preoperative history of stroke and associated coronary artery disease in CM group were significantly higher than those in KM group. Cardiothoracic ratio on the chest X-ray film, the voltage of f-wave in V1 lead on ECG and left ventricular dimension were similar in both groups (Table 1).
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Operative Procedure
The details of operative technique of our conventional maze procedure were described previously.13 KM is composed of PV isolation by incision and suture, and cryoablation for the interruption of macro-reentry circuits in the left and right atriums (Figure 1).
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The scheme of current CM is described in Figure 1. The major difference between KM and CM is the use of cryoablation for PV isolation from the left atrium. We incised only right-sided left atrium in CM just for simple mitral valve operation. Cryoablation was applied on the atrial endocardium to -80°C cold for 2 minutes with 20° angled 4 cm linear probe (CCS-200, Cooper Surgical, Shelton, CT). Another difference is the site of cryoablation on the interatrial septum. Cryoablation was performed between fossa ovalis and right atrial incision (Figure 1). We avoid injury on the sinus node or sinus node artery in CM. Right atrial appendage was fully preserved and left atrial appendage was partially preserved in CM. Concomitant procedures were similar in both groups (Table 1). As for myocardial protection, crystalloid cardioplegia had been used early in the period of KM but not in CM group at all. We preferably use tepid blood cardioplagia these years.
Postoperative Management
Electrocardiogram (EKG) was continuously monitored until cardiac rhythm became stable. Perioperative AF or atrial flutter was treated with group Ia and Ic antiarrhythmic drugs. Cardioversion was performed if necessary. Verapamil or beta blocker was added for the treatment of high ventricular rate. Group III antiarrhythmic drugs, sotalol or amiodarone, have never been used. Antiarrhythmic drugs were gradually withdrawn 3 months after operation.
Warfarin was routinely administered to all patients for 3 months. If the sinus rhythm was constantly maintained, anticoagulation therapy could be terminated in patients with mitral valve repair or biological valve implantation. Then small dose of aspirin was given if the contraction of left atrium was absent or left atrial dimension was over 55 mm.
These postoperative antiarrhythmic and anticoagulation strategy were the same in both groups.
Follow-Up Data
The status of patients was determined by referring to medical records and correspondence with the responsible physicians. All the events were recorded in detail. Patients were followed up by EKG, chest roentgenogram, and echocardiography with pulsed Doppler study every 3 months. We defined the sinus rhythm on EKG if the P-wave was present. Follow-up was complete by outpatient clinic or mail interview in all patients. The mean follow-up time was 18.8±10.8 months for CM and 64.1±27.4 months for KM.
Statistical Analysis
Continuous variables are expressed as the mean values±SD. The clinical profiles of the 2 groups were compared by Wilcoxon rank sum test or Fisher’s exact test. Longitudinal data were estimated by the Kaplan-Meier method and differences of 2 groups were compared by Cox-Mantel method.
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Results |
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Early Results
Cardiopulmonary bypass time and aortic cross clamp time in KM group (214±47 minutes and 144±37 minutes) were significantly (P=0.001 and P=0.03) longer than in CM group (186±56 minute and 134±43 minute).
Reexploration for bleeding was required in 2 cases (1.8%) in CM group and in 5 cases (4.5%) in KM group (P=0.25). The amount of chest tube drainage for 12 hours in ICU in CM group (590±353 mL) was significantly (P=0.02) smaller than that in KM group (745±618 mL). The patients who required high dose catecholamine (dopamine >8 µg/kg/min) were more frequently seen in KM group (4.5%) than CM group (0%) (P=0.02). The incidence of other early complications was the same in both groups (Table 2).
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On discharge from hospital, sinus rhythm was regained 94 patients (85.4%) after CM and 95 patients (86.4%) after KM. There was no significant difference between 2 groups. Perioperative recurrence of AF was seen in 59 patients (54%) in CM groups and in 66 patients (60%) in KM group. There was no significant difference in the incidence of perioperative AF (Table 2).
Late Results
There were only 2 late deaths (1.8%) in KM group. One died of anticoagulation related intestinal bleeding, and the other died of cerebral infarction. One patient in CM group, who underwent mitral valve repair and regained sinus rhythm, suffered from cerebral infarction 4 months after the operation.
The actuarial survival rate at 3 years was 91.7% in CM group and 98.0% in KM group (P=0.32) (Figure 2). The actuarial freedom from stroke at 3 years was 99.0% in CM group and 99.0% in KM group (P=0.68). There was no significant difference between 2 groups (Figure 3).
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Three patients underwent redo mitral valve replacement in KM and 2 patients in CM. All of these 5 patients underwent mitral valve repair or commissurotomy combined with the maze procedure. One patient had angina pectoris and successfully treated with catheter intervention for significant coronary artery disease (Table 3). The event-free survival rate as assessed by the freedom from cardiac death, thromboembolism, reoperation, and anticoagulation-related hemorrhage at 3 years was 88.5% in CM group and 96.2% in KM group (P=0.31).
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The actuarial freedom from recurrence of sustained AF at 3 years was 99.0% in CM group and 90.4% in KM group. There was no significant difference between the groups (P=0.11) (Figure 4).
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Discussion |
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The correction of mitral valve disease alone is not sufficient to restore sinus rhythm in the majority of the patients.3,15,20 The maze procedure during the mitral valve operation is the only effective way to facilitate the recovery of sinus rhythm and eliminate the morbidity of AF.1 The sinus rhythm recovery rate was relatively low (59% to 90%) in mitral valve disease compared with isolated AF, probably because of the dilated left atrium and degenerated myocardium.3,6–8,13,16 To improve the successful rate and decrease the complications in the maze procedure, we had imposed restrictions on the indication of the maze procedure and modified the operative procedures.12,13
The disadvantages of the conventional maze procedure are the long atrial suture line and the prolongation of cardiac ischemic time, which causes postoperative bleeding,3 ventricular dysfunction, and occasional injury of sinus node artery. In addition, we speculate that excessive atrial incision can be a cause of the impairment of postoperative atrial contraction and possibly increase the focus of the reentry. And "cut-and-sew" technique in the encircling incision and suture around the orifices of PV was time-consuming and somewhat technically demanding,3,15 and reexploration for bleeding was mostly attributed to this suture line in our experience. To resolve these problems, many surgeons have modified the maze procedures. In common, incision and suture for PV isolation substituted by the sutureless devices such as cryoablation or radiofrequent ablation6–11,21 and recent minimally invasive cardiac surgery accelerates such a modification. On the other hand, PV has the important role as the trigger of the initiation of AF. Haissaguerre and colleagues17 reported 94% of the ectopic foci were present in the PV and Chen and colleagues18,19 reported that PV contributed to the initiation of AF in 88 to 93% of patients. Therefore some surgeons believe that incision and suture for PV isolation from the left atrium is mandatory to restore sinus rhythm.14,15,22,23 However, there has been no comparative study to elucidate the feasibility of the use of devices or the obligation of atrial incision and suture, especially for PV isolation.24
Cryoablation is advantageous in the aspect of the minimal damage on endocardium and creating the transmural homogeneous lesions.24,25 It has been successfully used for the treatment of cardiac arrhythmia for a long time. During mitral valve operation, our current procedure of CM requires no additional atriotomy. The left atrium was incised in almost the same length as a standard right-sided left atriotomy, which was essential for the approach to the mitral valve. And the left atrial appendage was just ligated from the epicardial side. This method simultaneously has benefits to preserve the mechanical function and atrial natriuretic peptide secretion,26 which could decrease the incidence of the fluid retention and requirement of high dose of catecholamine after CM.
The use of the cryoablation for PV isolation is advantageous in shorter procedural time and decreased risk of bleeding, the satisfactory rate of sinus rhythm recovery, and its maintenance in the intermediate term follow-up, comparing with PV isolation with cut-and-sew technique. CM shortened the aortic cross clamp time by 10 minutes. It takes only 20 to 25 minutes of additional aortic cross clamp time in mitral valve operation. Less amount of chest tube drainage in CM group is attributed to the shorter cardiopulmonary bypass time and diminished left atrial incisional line. The sinus rhythm restoration and maintenance rate of CM group were as good as those in KM group in our series. On the contrary, Izumoto and colleagues6 reported that the recurrence of AF during 5 years after operation was as high as 22% when they use cryoablation in their modified procedure. The deprived intermediate outcome of their series is probably because of inappropriate applications of the cryoablation. We have frozen the tissue up to -80°C as long as 2 minutes under bloodless field to create completely transmural cryolesions.
The maze procedure is not mandatory in patients with AF who undergo mitral valve surgery. Therefore, it should be as less invasive as possible as an adjunctive procedure. Minimally invasive surgery including robotic surgery21 has been introduced into the mitral valve operation last 6 years. Surgeons who are good at minimally invasive mitral valve repair demand minimally invasive maze procedure. If the maze procedure must be composed of cut-and-sew technique, the minimally invasive mitral valve operation is restricted. Our results proved the rationale of the cryoablation instead of cut-and-sew technique in the maze procedure, and will spread the future of the maze procedure with concomitant minimally invasive mitral valve surgery.
The drawback of the present study is the operation was not randomly assigned for CM and KM in a certain period. There might be some bias in this study. KM was gradually replaced by CM in a couple of months. We are more accustomed to the procedure and postoperative care in CM from the beginning. And the advance in the cardioplegic solution has been notable for several years, and it could be related to the requirement of inotropic support in some cases after KM. However, the bias is considered to be negligible in sinus rhythm recovery rate and maintenance, because preoperative profiles were completely matched in 2 groups.
In conclusion, the cryo-maze procedure including cryoablation for PV isolation was as reliable as the conventional maze procedure.
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