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J Thorac Cardiovasc Surg 2004;127:457-464
© 2004 The American Association for Thoracic Surgery
Surgery for congenital heart disease |
a Department of Cardiac Surgery, German Heart Center Munich, Technical University Munich, Munich, Germany
b Department of Cardiology, German Heart Center Munich, Technical University Munich, Munich, Germany,
c Department of Pediatric Cardiology and Congenital Heart Disease, German Heart Center Munich, Technical University Munich, Munich, Germany
Read at the Eighty-third Annual Meeting of The American Association for Thoracic Surgery, Boston, Mass, May 4-7, 2003.
Received for publication May 2, 2003; revisions received July 31, 2003; accepted for publication August 11, 2003.
* Address for reprints: Joachim Weipert, MD, Department of Cardiac Surgery, German Heart Center Munich, Lazarettstr. 36, 80636 Munich, Germany
Weipert{at}dhm.mhn.de
| Abstract |
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METHODS: Current follow-up was available in 162 patients (2005 patient-years) with a wide range of underlying diagnoses operated on between February 1978 and May 1995. Risk factor analysis included patient-related and procedure-related variables, with late failure and the incidence of re-entrant tachycardia as outcome parameters.
RESULTS: Forty late failures were observed (2.0 per 100 patient-years). At 15 years, Kaplan-Meier estimated survival was significantly (P = .007) better for patients with tricuspid atresia (93%) compared with that for patients with complex congenital malformation (71%). The sole multivariable risk factor for Fontan failure was the type of underlying diagnosis. At 20 years' follow-up, overall freedom from tachycardia was estimated to be 46% ± 12%. Acute success of electrophysiologic ablation was seen in 25 (83%) of 30 patients, and Kaplan-Meier estimated freedom from recurrent tachycardia was 81% ± 10% at 3 years. Multivariate analysis identified duration of Fontan circulation as the sole risk factor for re-entrant tachycardias.
CONCLUSION: After the modified Fontan operation, long-term survival in patients with tricuspid atresia was significantly better compared with that in patients with complex congenital malformations. As first-choice therapy for atrial re-entrant tachycardias, we recommend electrophysiologic ablation therapy.
The purpose of this article is to document our results with radiofrequency ablation therapy of tachycardia in patients after the Fontan operation. We determined patient- and procedure-related risk factors influencing late Fontan failure, development of IARTs, and management strategy.
| Methods |
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Electrophysiologic technique
If patients had been treated unsuccessfully with an average of 3 antiarrhythmic drugs, an ablation procedure was indicated. Antiarrhythmic drugs were discontinued more than 5 plasma half-lives before the study. For the procedure, patients were sedated with midazolam (1-2 mg administered intravenously). A 64-electrode basket catheter (Constellation; EP Technologies, San Jose, Calif), providing 56 bipolar electrocardiograms, was placed in the right atrium through an 11F-long sheath inserted from the femoral or internal jugular veins. On the basis of echocardiographic estimation of right atrial dimensions, basket diameters between 48 and 90 mm were used.15,16 After basket catheter deployment, a 5F decapolar catheter with an interelectrode distance of 2 to 10 mm spacing between electrodes was positioned in the coronary sinus (in cases when the coronary sinus was not surgically drained in the left atrium) to detect small changes in intracardiac position. The third catheter was used as a roving catheter to record and pace from selected sites in the right atrium and to perform radiofrequency ablation.
Definitions
Fontan survivors were defined as patients with an intact Fontan pathway of any modification. Fontan failure was defined as death at the time of last follow-up because during late follow-up, no takedown of the Fontan circulation to a systemic to pulmonary shunt procedure was performed. Time to IART was defined as the period beginning 30 days after the Fontan procedure and extending to the date of the first electrophysiologic investigation. By defining time to IART in this way, the uncertain effects of early arrhythmias in patients without frequent follow-up were eliminated. Patients with antiarrhythmic drugs and regular sinus rhythm were censored at the time of the most recent follow-up.
Statistical analysis
Overall late Fontan failure and the incidence of postoperative IARTs served as outcome parameters. The influence of early mortality was eliminated by defining survival time as the period beginning 30 days after the Fontan procedure. Patients in whom the Fontan circulation did not fail were censored at the time of last follow-up. Estimated actuarial survival and freedom from IARTs were determined by using the Kaplan-Meier method. Significance during univariable analysis was assessed by using the log-rank test when the type of diagnosis for Fontan survival and the type of Fontan anastomosis for IART were the outcome parameters during the Kaplan-Meier procedure. For multivariable analysis, the Cox proportional-hazards regression model was used to establish the variables independently predictive of Fontan failure and the incidence of IARTs. Hazard ratios with 95% confidence intervals were constructed for the significant multivariable predictors. Final models were derived by using the forward stepwise selection procedure. Variables having P value of less than .1 in the univariable analyses were entered as candidates into the Cox regression models. A P value of less than .05 was required for the variable to be retained in the equation. All reported P values are 2 tailed. Statistical analysis was performed with the SPSS software package (version 10.1; SPSS, Inc, Chicago, Ill). Data are presented as means ± SEM or SD as indicated.
| Results |
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For RA-RV anastomoses, either the Bjoerk17 modification (n = 60) with a polytetrafluoroethylene* tunnel or an allograft (n = 10) was used. For RA-PA connection, either a direct right atrial to pulmonary artery anastomosis (n = 26)18 or allografts (n = 14) or a lateral tunnel constructed with autologous atrial tissue (n = 52) was used. Between patients with Fontan failure and survivors, no significant difference for preoperative mean pulmonary artery pressure, mean indexed pulmonary artery resistance, mean right atrial pressure, mean ventricular end-diastolic pressure, and mean hematocrit and hemoglobin values was found (Table 1). Preoperatively, 154 (95.1%) patients were in sinus rhythm, and 4 patients showed atrial fibrillation or intermittent tachycardias that could be controlled by medical therapy. In 2 patients pacemakers for treatment of bradyarrhythmia were implanted. The mean age at the time of the Fontan operation was significantly (P = .04) different, being 7.8 ± 5.9 (SD) years (median, 6.1 years) for patients with TrA and 9.7 ± 5.6 years (median, 7.8 years) for patients with CCMs. The mean Fontan circulation time was significantly (P = .002) longer for patients with TrA (13.5 ± 4.8 years; median, 13.9 years) compared with that for patients with CCMs (10.9 ± 5.3 years; median, 12.4 years). The Kaplan-Meier estimate of overall freedom from Fontan failure was 89.0% ± 2.4%, 83.0% ± 3.8%, 77.0% ± 3.5%, and 59.0% ± 7.7% at 5, 10, 15, and 20 years' follow-up (Figure 1). The Kaplan-Meier estimate of freedom from Fontan failure at 15 years was significantly (P = .007, log-rank test) higher for patients with TrA (83.0% ± 4.0%) compared with that for patients with CCMs (70.8% ± 5.5%). In 17 (11%) patients conversion of the modified Fontan pathway to total cavopulmonary connection was performed during follow-up.
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| Discussion |
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Risk factors for late Fontan failure
The surgical procedures used in this Fontan series resulted in a functional status that was found to be comparable with data reported in the literature.19 Four large series1,2,8,20 have provided important information about late outcome after the modified Fontan operation. Yet comparison of outcome measures between institutions is not possible without fully accounting for patient selection, surgical modifications, time of operation, interventional catheter techniques, and postoperative management. Nevertheless, Kaplan-Meier estimates of late Fontan failure in our series (eg, at 15 years being 77.0% ± 3.5%) are comparable with those published in the above-mentioned series. Multivariate Cox proportional hazard testing showed the diagnosis of CCM as significantly associated with Fontan failure. These data indicate that patient-related but not procedure-related variables determine the outcome in patients undergoing the Fontan operation during late follow-up.
Risk factors for IART
The development of tachycardia during the life of a patient who has undergone the Fontan operation has been a matter of concern since the introduction of the Fontan procedure in 1971.21 In our Fontan population the development of tachycardia was clearly a time-dependent process (Figure 2). To overcome the uncertainty of the clinical significance of IART after the Fontan operation, we defined the time until the first IART treatment, determined by means of radiofrequency ablation, as an outcome parameter. The Kaplan-Meier estimated freedom from tachycardia is similar to values published from other series.5,6 In general, patients with an RA-RV anastomosis had a more simple underlying cardiac malformation compared with the patients with RA-PA anastomoses (Figure 3). This might explain why patients with RA-RV connections had a significantly (during univariable analysis) lesser incidence of tachycardia. Yet in the multivariable Cox proportional-hazard model, this difference was lost, and duration of follow-up remained the only significant variable for the development of tachycardia (Table 2). Summarizing the data from this and 2 recent studies5,6 doing an overview of 995 patients undergoing the Fontan operation, the duration of the follow-up interval,5 prior palliation with atrial septectomy,5 and atrioventricular valve replacement6 remain independent risk factors for the development of atrial tachycardia after the modified Fontan operation.
Management for IART
In patients undergoing the Fontan operation, the critical isthmus for the re-entrant circuit in atrial flutter was located between the tricuspid annulus, the coronary sinus, and the Eustachian ridge adjacent to the inferior vena cava.22 This region was also involved in the majority of our patients. In addition, further zones of slow conduction that define a critical isthmus in which radiofrequency ablation is likely to be successful have been identified and were also targeted: between the atriotomy and (1) the tricuspid annulus or the (2) superior or (3) inferior vena cava or (4) between the tricuspid annulus and the Fontan conduit. We performed an electroanatomic mapping technique for identification of the critical tachycardia zone, of which a detailed description has been recently published.23 This technique offers at least 3 advantages for mapping and guiding ablation of IARTs after the Fontan operation: (1) acquisition of multiple and simultaneous recordings; (2) software-assisted activation maps that rapidly identify zones of split potentials and slow conduction that can be further analyzed with an entrainment technique as possible targets for radiofrequency ablation; and (3) multiple and stable rows of electrodes representing a reliable tool to verify the completeness of the ablation lines.
Early and high recurrence rates of tachycardia after electrophysiologic ablation therapy have been reported in a small series of patients undergoing the Fontan operation.10 Therefore right atrial Cox maze procedure, pacemaker insertion, and conversion to total cavopulmonary connection was recommended as first-choice therapy in these patients.11-13 However, comparison of outcome measures between institutions is not possible for the same reasons mentioned above. Furthermore, innovation of the electrophysiologic technique (eg, introduction of bidirectional pacing to assess lesion continuity and better software) and gaining experience might influence early and late success.16,23 By using this technique, 80% freedom from IART at 3 years' follow-up or reduction of tachycardia frequency could be achieved. In our experience patients with tachycardia do not frequently have a failing Fontan circulation, which would facilitate indication for conversion to cavopulmonary connection. Therefore our concept is that surgical intervention should be reserved for those patients with failed electrophysiologic ablation or IARTs with failing Fontan circulation.
Limitations of the study
The validity of our study is clearly limited by its retrospective nature and evaluation of data in a nonconsecutive patient group. Although long-term follow-up information was available in a high percentage of the patients, the incidence of IART is most likely underestimated because of the transient nature of some arrhythmias and the limited availability of serial electrocardiographic and Holter studies. Interpretation of the results is also difficult because there is a lack of an unoperated or conventionally palliated patient population as a control group.
Since 1995, we have changed our institutional policy and abandoned the modified Fontan operations described in this series. Recent data from patients with total cavopulmonary anastomoses14 indicate that the lateral tunnel approach with prosthetic material and early correction of cyanosis considerably reduces the incidence of atrial arrhythmia compared with that of the patient group presented in this article. Thus this article might serve as a basis for future studies, clarifying the long-term outcome and treatment approach for IART in patients with the older Fontan modifications.
Conclusions
In this retrospective study we have shown that late survival after the Fontan operation was significantly determined by the patients' underlying congenital malformations. The long-term survival was estimated to be higher in patients with TrA compared with that in patients with CCM. IART develops over time after the Fontan operation, regardless of the type of underlying morphology. By using 3-dimensional atrial electroanatomic activation mapping, rapid and comprehensive therapy of re-entrant atrial tachyarrhythmias in patients undergoing the Fontan operation is achieved. Surgical intervention should be reserved for those patients who do not respond to interventional therapy.
Discussion
Dr Constantine Mavroudis (Chicago, Ill). Dr Weipert and associates have presented their experience with 162 patients undergoing the Fontan operation with varying types of venoatrial pulmonary artery connections. Congratulations on a very nice presentation. It was clear, succinct, and easy to follow.
Dr Weipert and associates divided their patients into 2 groups, namely the TrA group and the complex group. The incidence of atrial tachycardia over time was documented, and they also showed the benefits of transcatheter ablation in controlling atrial arrhythmias in some 25 patients. Their results are better than most in the literature, but nevertheless, they have a 50% recurrence rate over a 5-year period. This article was nicely presented and serves as an important benchmark because of the significant follow-up, which includes approximately 2000 patient-years.
Our experience at Children's Memorial Hospital in Chicago has centered on those patients who had Fontan failure on the basis of atrial arrhythmias, pathway obstructions, and valvular dysfunction. In your article you thought that it was unlikely that arrhythmias would be the sole cause of Fontan failure. We have a differing opinion in that we have seen a number of patients who have had atrial arrhythmias over long periods of time who have ventricular dysfunction and have regained their ventricular function after the maze procedure. Perhaps you could comment on this issue.
I have several other questions. I see from the article that you excluded patients with hypoplastic left heart syndrome. Is it because you had few patients like this, or have you excluded others with other more complex anatomy, and if you did, can you tell us why?
Also, did you see a difference in the transcatheter ablation success rate between the patients with TrA and your complex congenital patients? The reason I ask this is because the patients with TrA tend to have thicker atrial walls and might not be treatable by means of energy-giving techniques because of the difficulty in creating transmural lesions. You might want to give us some thoughts on that.
And another thing, I did not see in your long follow-up any patients who had atrial fibrillation. Did any of your patients have atrial fibrillation? We contend that atrial fibrillation is the natural course after atrial re-entrant tachycardia for a significant number of these patients; that is to say, the first arrhythmia is atrial re-entrant tachycardia followed in time with atrial fibrillation. If you did have patients like that, did you take these patients to the catheterization laboratory and try to perform a left- and right-sided maze procedure to convert them or did you operate on them?
We do not have a problem with performing transcatheter ablation for our sets of patients. However, we find that a number of these patients have pathway obstructions and anatomic problems as well, and therefore we usually go to surgical intervention with these patients.
I look forward to your comments, and I also look forward to your transcatheter techniques getting better, where these patients hopefully will not have to have an operation that is as large as this one.
Dr Weipert. Thank you very much, Dr Mavroudis. I skipped the problem of conversion operation to total cavopulmonary connection in these patients, but we did 17 conversions in patients with the full symptoms of Fontan disease, such as together with fibrillation, flutter, and protein-losing enteropathy, and there was a mortality rate of about 25%. Therefore we are reluctant to go ahead and do the operation in patients who have flutter, which I could present here.
Fibrillation, when it is disturbing the patient, might be also an indication to try catheter ablation, but when it is with a normal heart rate, it is not.
Patients with hypoplastic left heart syndrome were excluded, and they were not amenable for this type of Fontan operation. And we could not see a difference at present between the patients with TrA and the other patient group with regard to the success rate or ablation rate. The patient numbers are too small, and the numbers of failures are too small also. Atrial fibrillation alone is not an indication to convert the Fontan tunnel to a total cavapulmonary anastomosis.
Dr Marcus Haw (Southampton, United Kingdom). I come from a center from which Dr Batts published his results with ablation, and therefore we congratulate you with your fantastic results for transcatheter intervention.
We followed very much Dr Mavroudis' line in treating these patients, and we have almost invariably found with the traditional type of atriopulmonary connection that patients have a good deal of effort intolerance, as well as the intermittent flutter, and I wonder if you have any sort of outcome data in terms of your patients' functional status after a successful ablation?
Dr Weipert. The follow-up is short, and we do not have functional data at present. Patients were satisfied with their clinical condition when atrial flutter could be abolished or arrhythmia frequency decreased. But we do not have objective methods where we can say it is really an advantage for this patient.
Dr Haw. Thank you.
Dr Thomas L. Spray (Philadelphia, Pa). How many of these patients in late follow-up ended up with a pacemaker, and how many are still receiving antiarrhythmia medications?
Dr Weipert. Three patients ended up with a pacemaker, and 3 of them are taking amiodarone.
Dr Spray. And are they all receiving ß-blockers or only a selected portion?
Dr Weipert. Most of the patients are receiving ß-blockers.
Dr Carlos Troconis (Caracas, Venezuela). Are those arrhythmias surgically related, or were they related to dilatation of the right atrium?
The reason for my question is because in the past 5 years, we have operated on 3 patients older than 18 years with extracardiac conduit, and all of them had normal sinus rhythm at follow-up. On the other hand, we have 20 cases (2-4 years of age at operation) over 10 years' follow-up of extracardiac conduit, and we have not seen any surgically related arrhythmias at all.
Dr Weipert. The lateral tunnel Fontan operation might be very promising for the future.
There was a recent article from the Boston group: at 10 years, 90% of the patients with a lateral tunnel were free from new supraventricular tachycardias. The lateral tunnel approach probably is the best solution for the univentricular heart at present.
In the patient with a failing Fontan operation, when there are surgically amenable lesions, we go ahead and make a conversion, but in these patients this was not the case.
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| References |
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