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Click here to read this article as a CME activity
a Division of Cardiovascular-Thoracic Surgery, Children's Memorial Hospital, Chicago, Illinois
b Division of Cardiology, Children's Memorial Hospital, Chicago, Illinois
c Department of Surgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois
d Department of Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, Illinois
Accepted for publication April 23, 2008.
* Address correspondence to Dr Mavroudis, Division of Cardiovascular-Thoracic Surgery-M/C #22, Children's Memorial Hospital, 2300 Children's Plaza, Chicago, IL 60614 (Email: cmavroudis{at}childrensmemorial.org).
Presented at the Forty-fourth Annual Meeting of The Society of Thoracic Surgeons, Fort Lauderdale, FL, Jan 28–30, 2008.
| Pediatric cardiac surgery:
The Annals of Thoracic Surgery CME Program is located online at http://cme.ctsnetjournals.org. To take the CME activity related to this article, you must have either an STS member or an individual non-member subscription to the journal.
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Abstract |
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Methods: Between 1987 and 2007, arrhythmia operations were done in 11 patients without associated congenital heart disease and in 89 along with congenital heart repairs. Mean age was 15.9 ± 12.5 years (range, 7 days–48 years); 7 were infants (mean age, 23 ± 16 days). Resternotomy was performed in 65 (65%). Two functional ventricles were present in 67 patients; 33 had 1 functional ventricle. Arrhythmias included macro-reentrant atrial tachycardia in 45, atrial fibrillation in 11, accessory connections in 19, atrioventricular nodal reentry tachycardia in 6, focal atrial tachycardia in 6, and ventricular tachycardia in 13.
Results: Operative mortality was 3 (3.0%) due to advanced associated congenital heart disease. There were 4 late deaths (4.0%) and 2 late cardiac transplants (2.0%). Freedom from arrhythmia recurrence at 1 and 10 years was 94% and 85% for atrial arrhythmias, and 85% and 68% for ventricular arrhythmias, respectively.
Conclusions: Successful surgical therapy for atrial arrhythmias can be performed safely with a high freedom from recurrence rate in patients with and without associated congenital heart disease. Surgical ablation for ventricular arrhythmias is less predictive. Complexity of the underlying congenital heart disease and hemodynamic status may contribute to potential arrhythmia recurrence or new onset arrhythmia manifestation.
The introduction and development of arrhythmia surgery in patients with and without associated congenital heart disease has enabled clinicians to treat disabling arrhythmias not amenable to transcatheter ablative techniques [1–8]. Because decreased cardiac output attributable to arrhythmias is compounded by coexisting unrepaired or residual congenital defects, the initial or reoperative repair must include both physiologic-anatomic correction as well as electrophysiologic correction if optimal long-term outcome and beneficial quality of life are to be achieved [9].
Mechanisms underlying the various atrial and ventricular arrhythmias have been incompletely understood by congenital heart surgeons owing to case-mix variability in many congenital heart surgery centers. This leads to an incomplete understanding of what is accomplished by ablative therapy. The purpose of this article is to update [10] our long-term results of arrhythmia operations and review arrhythmia mechanisms and the principles of corrective ablative therapy.
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Material and Methods |
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18 years of age) had intervention without associated congenital heart repair. Mean age at operation was 15.9 ± 12.5 years (range, 7 days–48 years); 7 were infants (mean age, 23 ± 16 days). Resternotomy was done in 65 of 100 patients (65%). Two functional ventricles were present in 67. Arrhythmias included macro-reentrant atrial tachycardia in 45, atrial fibrillation in 11, atrioventricular nodal reentry tachycardia in 6, concealed and manifest accessory connections in 19, focal (automatic) atrial tachycardia in 6, and ventricular tachycardia in 13. Some patients had more than one arrhythmia and were treated with techniques appropriate for the particular substrates. Clinical features of all patients are noted in Tables 1 to 6.
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Infrequently, arrhythmia was not inducible in the catheterization laboratory, in which case intraoperative mapping was attempted. Intraoperative epicardial mapping was performed in 51 patients; those with atrial fibrillation or hemodynamic instability during arrhythmia were excluded. Mapping was performed early in the series with a hand-held probe or a multiple-array epicardial sock; it is now performed with 2 decapolar probes.
Standard surgical techniques for arrhythmia ablation were used, which included resection, isolation, and cryoablation of affected atrial or ventricular tissue [1–8]. Cryoablation in the early part of our experience was performed using 3-, 5-, and 15-mm circular probes (Frigitronics, Cooper Surgical Inc, Shelton CT) at –60°C for 90-second lesions. Since 2003, we have used malleable linear CryoCath probes to place 60-second lesions at –150°C (CryoCath Technologies Inc, Montréal, Québec, Canada).
Macro-reentrant atrial tachycardia (Fig 1) was ablated by either an isthmus ablation (early in the series) or a standard or modified right atrial maze procedure that was specific for the anatomic substrates: patients with 1 ventricle (primary Fontan) [13] or patients with 2 ventricles [7]. Ablative therapy principles for anatomically complex patients with macro-reentrant atrial tachycardia are based on the normal pattern of atrial electrical impulses and the paths that these impulses take around natural or created obstacles to stimulate the atrioventricular node.
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The goal of cryoablation therapy is to transform an area of slow conduction to an area of no conduction by interrupting the electrical corridor (isthmus) between adjacent obstacles or scars, while preserving sinoatrial and atrioventricular nodal function. A patient with a separate hepatic vein entry into the right atrium, for example, will require cryoablation lesions to connect the inferior vena cava os to the coronary sinus os, the hepatic vein os to the coronary sinus os, and the hepatic vein os to the tricuspid annulus; remaining lesions are standard for the right-sided maze procedure. These principles (Fig 1A) can be applied to all other natural and created obstacles; it is important to recognize that these principles do not apply to focal atrial tachycardias, which arise from discrete foci.
Atrial fibrillation was treated by left atrial Cox-maze III procedure in addition to modified or standard right atrial maze, depending on the anatomic substrate [7, 8], using a combination of incisions and cryoablation lesions. Selective cryoablation modification of the atrioventricular nodal slow pathway in the region of the coronary sinus was used to treat atrioventricular nodal reentry tachycardia (Fig 2). Accessory connections (Fig 3A and B) were divided by both epicardial and endocardial resection techniques. Focal (automatic) atrial tachycardia (Fig 4) was treated by isolation, resection, or cryoablation of the affected atrial tissue [3]. Ventricular tachycardia was ablated by a combination of endocardial resection and cryoablation, or epicardial resection and cryoablation based on the identified pathology [5].
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Consistent with our previously reported protocols, patients with atrial arrhythmias (other than atrial fibrillation) received β-blockade for 3 months postoperatively; patients with atrial fibrillation received amiodarone therapy for 3 months postoperatively. Patients with inducible sustained ventricular tachycardia postoperatively received implantable defibrillators. Arrhythmia recurrence was assessed at routine visits by review of symptoms, comprehensive electrocardiographic monitoring, and interrogation of pacemakers or implanted defibrillators. Consulting statistician constructed freedom from arrhythmia recurrence graphs using the life-test procedure product-limit survival estimates. Institutional Review Board approval for this retrospective study was obtained, and the need for informed consent was waived.
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Results |
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Late deaths occurred in 4 patients (see Tables 1, 4); one death that occurred after attempted takedown of a Mustard procedure was previously reported [10].
Operations were performed as emergencies in 2 surviving patients who had acute hemodynamic decompensation. One patient without congenital heart disease presented with cardiogenic shock due to focal atrial tachycardia and was brought to the operating for an emergency ventricular assist device. He underwent electrophysiologic mapping of the right atrium and resection of the arrhythmogenic focus in the right atrial appendage with conversion to normal sinus rhythm. No assist device was implanted; gradual normalization of ventricular function ensued without arrhythmia recurrence. Another patient with a left-sided accessory connection and aortic perforation during a transseptal procedure before catheter ablation had limited epicardial mapping with epicardial cryoablation. Accessory connection function later recurred and was treated with β-blocking medication.
The median postoperative hospital stay was 9 days (range, 4 to 278 days). Early postoperative surgical complications requiring return to the operating room occurred in 17 of 100 (17%) patients. Three patients with accessory connections who were operated on early in our series (1989 to 1991), before transcatheter ablation procedures were standard therapy, underwent a second surgical ablation postoperatively at 4, 4, and 8 days, respectively, because of recurrent tachycardia; 1 patient had late recurrence. A fourth patient, also early in the series, underwent surgical ablation 9 months postoperatively because of late recurrence of accessory connection-mediated tachycardia. Additional patients underwent early reoperation for ventricular assist device placement, Fontan takedown, control of bleeding, thoracic duct ligation, sternal instability, delayed sternal closure, and device placement in 6 or revision in 2.
Two patients required cardiac transplantation late after the operation (Tables 1, 3). A third patient is under consideration for cardiac transplantation (Table 6).
Freedom from arrhythmia recurrence, as determined by documented persistent clinical recurrence more than 3 months postoperatively [14], was 94% and 85% for atrial arrhythmias at 1 and 10 years, respectively, representing nine recurrences in 87 patients (10%; 3 macro-reentrant atrial, 4 accessory connection-mediated, and 2 focal atrial tachycardias), and 85% and 68% for ventricular arrhythmias at 1 and 10 years, respectively, representing two recurrences in 13 patients (15%; Fig 5).
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Comment |
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Our arrhythmia recurrence rate for atrial tachycardia in congenital heart patients (Fig 5) compares favorably with other reports [15–17]. The recurrences can be explained by anatomic, electrophysiologic, and hemodynamic variability that present significant challenges to the principles of arrhythmia ablation. Important anatomic variability that impacted arrhythmia ablative techniques included bilateral venae cavae, separate atrial entry of the hepatic veins, anomalous pulmonary venous return, absence of the coronary sinus, common atrioventricular valve, juxtaposed atrial appendages, and dilated coronary sinuses. These variations tended to occur in diagnoses known to have anomalous conduction systems and poorly defined accessory connections such as crisscross heart with single ventricle and straddling atrioventricular valve, single ventricle with heterotaxy, and single ventricle with l-transposition.
Most of our recurrences tended to be in patients with residual accessory connections and macro-reentrant atrial tachycardias in whom preoperative and improvised intraoperative electrophysiologic studies presented various challenges. It was not uncommon to treat a patient for one arrhythmia only for another and unrelated arrhythmia to occur using a different pathway. Hemodynamic variability, preoperative ventricular dysfunction, and hesitation to prolong the cross-clamp time for complex intracardiac procedures led us to perform an abbreviated arrhythmia operation in 3 patients whose arrhythmias recurred. Whether more aggressive operative solutions would have resulted in better outcomes or given rise to adverse events must be left to speculation. The outcomes do underline the necessity of performing established arrhythmia operations; abbreviated procedures are likely to result in recurrence.
The characteristics of our patients with macro-reentrant atrial tachycardia include those with prior operations and atrial enlargement due to hemodynamic aberrations (Table 1). The largest category in this group is patients with a univentricular heart who underwent first-time Fontan operations. Other categories include patients who had reoperation for tetralogy of Fallot/double-outlet right ventricle or conduit replacement for right ventricular-to-pulmonary artery continuity, which a large multicenter study showed was related to late arrhythmia development and late sudden death [18]. Risk factors associated with these conditions establish the substrate for macro-reentrant atrial tachycardia propagated by an area of slow conduction, which could be the coronary sinus-inferior vena cava isthmus or around a previous atrial incision or scar, and an area of unidirectional block (Fig 1). Macro-reentrant atrial tachycardia recurred in 3 of 45 (7%) at a mean follow-up of 5 years, which compares favorably with other reports [15–17].
Eleven patients had surgical therapy for atrial fibrillation (10 with a Cox-maze III procedure) in association with initial Fontan, complex repair revisions, repair of atrioventricular canal, and mitral valve repair/replacement. We and others [10] have reported a high success rate in treating atrial fibrillation with the Cox-maze III procedure. Interestingly, 2 patients manifested new-onset atrial arrhythmias that were not previously recognized because patients with atrial fibrillation cannot be tested for multiple arrhythmogenic foci.
Our patients with atrioventricular nodal reentry tachycardia experienced no recurrence of arrhythmias, not unexpectedly due to the circumscribed nature of the arrhythmia (Fig 2). Customarily addressed in the catheterization laboratory, the arrhythmias in these patients were treated surgically because of the underlying complexity of their cardiac defects, extensive suture lines from prior operations, or the presence of an additional arrhythmia substrate. There were two late deaths, which underscore the complex congenital heart defects seen in this group.
Patients with accessory connections generally do not present with the usual prior atrial incisions. The electrophysiologic "playing field" (Fig 3, Fig 4) for this arrhythmia is the atria, the ventricles, the AV node, and the accessory connection(s). In general the accessory connection(s) in the normal heart can be found in all areas of atrioventricular continuity except for the shared annulus of the aortic and mitral valves. Complex congenital heart disease with transposed great arteries, subaortic coni, and double-outlet ventricles injects a level of complexity that challenges these established tenets. In these circumstance, the accessory fibers can potentially be found anywhere along the atrioventricular anatomic connections. The ablative therapy is aimed at accessory pathway interruption. This group had four recurrences; one very early in the series, one due to an abbreviated epicardial ablation, and the last two in patients with complex single-ventricle anatomy (crisscross heart and heterotaxy). Transcatheter radiofrequency ablation, even when performed in complex anatomy, is successful in most cases, allowing the surgical team to concentrate on the anatomic repair. Even so, the surgeon must know the operative approach for accessory connections in the rare event of failed catheter ablation or small patient size.
The recurrence rate in our patients with focal (automatic) atrial tachycardia was high at 33% (2 of 6 patients). Crawford and Gillette [19] reported a similar recurrence rate of 36% (4 of 11 patients) in children undergoing surgical ablation. They cited the difficulties in localization and the incidence of multiple foci for the high recurrence rate, and proposed more aggressive ablative techniques. Two approaches were used in our patients: resection of the arrhythmogenic focus (atrial amputation) or cryoablative isolation techniques. Recurrences occurred in 1 patient who had isolation of the pulmonary veins for a pulmonary venous arrhythmogenic focus and, in the other, right atrial ablation. The results in our series tended to be better when the arrhythmogenic focus was confined to the right atrial appendage and totally excised (Table 5). Patients with ill-defined limits of the arrhythmogenic focus will require better isolation techniques if uniform success is to be achieved.
Most reported surgical series involving ventricular tachycardia and congenital heart defects concentrate on tetralogy of Fallot outcomes [17, 20]. Interestingly, Karamlou and associates [17] reported a high arrhythmia-free survival rate in tetralogy patients with ventricular tachycardia undergoing reoperation whether or not an associated ablative procedure was performed (96% vs 95%). In contrast, there was significant difference in arrhythmia-free survival (75% vs 33%) in patients undergoing ablation for atrial tachycardia compared with those who did not have ablation.
Our experience with tetralogy patients who had resection or cryoablation for ventricular tachycardia is similar; however, 2 patients experienced late new onset of atrial tachycardia, raising the possibility that these patients might be better served with a prophylactic right-sided maze procedure at the time of ventricular tachycardia ablation. Our nontetralogy patients with ventricular tachycardia had varied diagnoses and were either unoperated or had prior surgical interventions.
Ablative methods for ventricular tachycardia are highly individualized and dependent on etiologic factors and anatomic findings. In our previous report [12], we found a positive correlation between gross anatomic findings and tachycardia focus manifested by identifiable dysplastic myocardial tissue, jet lesions, or scar from previous incisions. Patients undergoing ablation for ventricular tachycardia should be studied postoperatively for inducibility and undergo automatic internal cardiac defibrillator placement if the study is positive.
As in our previous report, we found that arrhythmia surgery can be successful in patients with and without associated congenital heart disease. The principles of ablative therapy can be applied to a wide range of intraatrial cardiac anomalies. The complexity of underlying congenital heart defects, hemodynamic status, and conduction system variability impact the surgical approach and may contribute to potential arrhythmia recurrence or new onset arrhythmia manifestation. This study is limited because the small number of patients in many of the subgroups is not amenable to statistical analyses. The low mortality is our series, however, emphasizes the safety of arrhythmia surgical intervention, even when there are associated complex congenital anomalies.
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Discussion |
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DR MAVROUDIS: In our experience, almost everyone with a single-ventricle repair had some form of a pacemaker. We had 3 patients in whom we placed epicardial wires without a pulse generator. All 3 required a pacemaker within 2 years of that operation. Of course, we place epicardial wires and implant them in the rectus muscle because we perform an extracardiac Fontan and access to the heart is only through an epicardial approach for a pacemaker.
In the rest of the patients with two ventricles, it was fairly rare to use a pacemaker. In some tetralogy patients, we did use an AICD [automatic implantable cardioverter defibrillator] due to inducible ventricular tachycardia after an ablative procedure. There were 3 patients in this category. Interestingly enough, none of them discharged in the 5-year follow-up. So we are saying that they are not recurrences, but it is hard to send somebody home who has inducible ventricular tachycardia and not treat it.
DR DODGE-KHATAMI: Most often just with temporary wires we should be okay?
DR MAVROUDIS: I think so. I think I would use temporary wires, unless you believe that through your arrhythmia surgery that you performed an injury to the AV node, which does not usually happen when these lesions are placed. The trouble is, as you know, these are complex congenital heart diagnoses, which are known to have anomalies of the conduction system, especially in patients with congenitally corrected transposition of the great arteries and crisscross heart.
DR JEFF L. MYERS (Boston, MA): You briefly touched on epicardial ablation for the left side. And we are constantly struggling with what to do with the left side in our 2-ventricle patients where if we don't enter the left side to do the lesions, then we don't have to cross-clamp to do the rest of the operation. So how do you do that? Do you do it epicardially? Do you do it with a radiofrequency device?
DR MAVROUDIS: That's a good question. We used cryoablation exclusively in this series. To expose the left atrium, we usually enter through the interatrial septum and use the malleable cryoablation probe. Usually with 2 or 3 lesions we can isolate the pulmonary veins. We amputate the left atrial appendage if the exposure is easy. If not, we isolate it from within the left atrium by cryoablation and, of course, perform the lesion to the mitral annulus.
One has to be very careful to define the arrhythmia when isolating the pulmonary veins. If the electrophysiologic substrate is left focal (automatic) atrial tachycardia, one really has to know where that lesion is in order to cryoablate it and isolate it from the rest of the atrium. That is how we do it. I hope that answers your question.
DR JOSEPH A. DEARANI (Rochester, MN): Could you comment on the various forms of the maze procedure, cut and sew, radiofrequency ablation, or cryoablation in terms of atrial mechanical function? The maze procedures are getting more and more modified and abbreviated in an effort to try to preserve atrial function and limit the lesions in order to make the operation simpler. In patients where you've done the equivalent of the Cox-maze III with cryoablation, do you have any information or any insight in terms of whether the atria are working afterwards?
DR MAVROUDIS: Thank you. That is a very good question. I have an answer to that question and I have a follow-up comment. To answer your question, I have no data on that. And I don't know anyone who does. And I think that that is a good thing to follow-up on, although I'm not sure how you measure atrial contraction. We have to figure that out.
We do have, actually, more important data, and that is, we have taken some patients to the operating room who are in extremis, who needed a VAD, and we found automatic atrial tachycardia. Intraoperative electrophysiologic mapping and ablation resulted in stabilization and normalization of ventricular function over time without VAD placement. So we had a more important issue in that ventricular dysfunction normalizes over time. And that demonstrates just how bad arrhythmias can be for ventricular function.
The answer to your question is we don't have the data on atrial function, but I just wanted to impart with you what can happen when one treats some of the arrhythmias in these patients; their ventricular function can improve dramatically.
DR JOSEPH M. FORBESS (Dallas, TX): Gus, I wanted to ask you a question about the preoperative EP study in these patients. Because I noticed from the manuscript that you kindly provided to me that only 54 patients actually had preoperative EP [electrophysiology] studies. Could you tell me a little bit about the population of patients who are getting this kind of surgery who have not had a preoperative EP study? What is your threshold there?
DR MAVROUDIS: All patients with atrial fibrillation do not undergo preoperative evaluation because there is no sense to it. There are patients whom I have taken to the operating room who are in extremis without preoperative studies, as noted earlier. And there are also patients who don't have very good access to the heart who tend to be infants with poor transvenous cardiac access.
In general, we try to perform a preoperative EP study on everyone except those patients with atrial fibrillation or hemodynamic instability. And when we can't, we perform an intraoperative EP study.
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