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Inova Heart and Vascular Institute, Falls Church, Virginia
Accepted for publication January 18, 2010.
* Address correspondence to Dr Ad, Inova Heart and Vascular Institute, 3300 Gallows Rd, Cardiac Surgery Research, Ste 3000, Falls Church, VA 22042 (Email: niv.ad{at}inova.org).
Presented at the Fifty-sixth Annual Meeting of the Southern Thoracic Surgical Association, Marco Island, FL, Nov 4–7, 2009.
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Abstract |
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Methods: This is a prospective longitudinally designed study assessing all patients who underwent surgical treatment for atrial fibrillation as a standalone or concomitant with other procedures by multiple surgeons. All patients were monitored according to the Heart Rhythm Society guidelines.
Results: From January 2005 to present, 400 consecutive patients operated on by multiple surgeons were enrolled. The overall success rate per the Heart Rhythm Society guidelines was 87% and 84% (off antiarrhythmic drugs, 78% and 73%) at 12 and 24 months, respectively. Sixteen patients (4%) were referred for electrophysiology study after the surgical procedure (15 Cox-maze III or IV, 1 pulmonary vein isolation). The average age was 61.1 ± 15.2 years; the mean left atrium size was 5.1 ± 0.7 cm; and the mean time to ablation was 16.9 ± 10 months. In 16 patients radiofrequency ablation was applied to treat the following atrial arrhythmias: 7 right atrial flutter or tachycardia, 3 left atrial flutter, 1 biatrial flutter, and 5 left atrial tachycardia. Six patients required a subsequent radiofrequency ablation intervention including 4 patients who required atrioventricular nodal ablations. The long-term success rate for the subsequent catheter ablation in these 16 patients (follow-up of 42.9 ± 9.8 months) determined by the rate of sinus rhythm as captured by electrocardiography was 94%. Fifty-three percent of the patients (n = 8) in sinus rhythm were still taking antiarrhythmic drugs; 8 patients remained on warfarin. There was 1 late noncardiac death and no late strokes.
Conclusions: In a certain subset of patients, unsuccessful surgical ablation of atrial fibrillation may result in symptomatic atrial arrhythmia. If indicated, catheter ablation is a safe and effective intervention with a relatively high success rate. The combination of the two treatment modalities, catheter and surgical ablation, can improve the outcome even in complex patients.
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Introduction |
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The success rate reported after the cut-and-sew Cox maze procedure is considered to be the gold standard, and some reports document a success rate as high as 90% [3], although other studies suggest a different success rate [4, 5].
Unlike the cut-and-sew techniques, the application of surgical ablation devices may result in an incomplete conduction block and thus recurrence of the atrial arrhythmia [6]. Previous studies have focused mainly on sinus node function [7]; however, new mapping devices allow a more complete intraatrial mapping in symptomatic patients such that recurrence of atrial arrhythmia was documented. As a result, new information related to the electrophysiologic characteristics is available, and another treatment option to improve success is available to us [8].
In this study we describe our clinical experience with patients after surgical ablation; the clinical and electrophysiologic characteristics and management of postsurgical ablation atrial arrhythmia is described and discussed.
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Material and Methods |
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The parent study is a prospective longitudinal study in which all patients undergoing surgical ablation for atrial fibrillation by multiple surgeons either as a standalone procedure or concomitantly with other surgical procedures are enrolled. All patients are longitudinally followed according to the Heart Rhythm Society guidelines [9] as well as a clinical protocol for recurrent atrial arrhythmias. The follow-up times occur at 6, 12, and 24 months. The clinical data obtained includes (1) rhythm as per electrocardiography, 24-hour Holter, or long-term monitoring, (2) incidence of stroke in the interim between follow-up times, (3) bleeding related to warfarin, and (4) all current medications to include antiarrhythmic medications. In addition to the clinical data collected, health-related quality of life using the Short Form 12 questionnaire (SF-12v2; Medical Outcomes Trust and Quality Metrics, Lincoln, RI) was also obtained at baseline and at respective times.
The following describes the surgical ablation techniques used for the subgroup of patients having subsequent radiofrequency catheter ablation procedures (RFA group):
Fifteen patients who underwent a complete Cox maze III or IV procedure had the procedure carried out using one of the following procedures:
The pulmonary vein isolation (n = 1) was performed using bipolar radiofrequency (AtriCure). In all patients having pulmonary vein isolation only, to include the one in the study, exit block was tested and confirmed. However, conduction block was not routinely assessed in the Cox maze III or IV patients at the time of the surgical procedure. This has, however, changed and our current practice is to test for an exit block across the pulmonary veins in patients having this part of the surgery performed with bipolar radiofrequency technology. It is unclear yet whether acute conduction block can be achieved for cryoablation, and therefore an assessment of conduction block for these patients is not being performed routinely.
The following paragraphs describe the radiofrequency catheter ablation approach for the RFA group:
The procedure was initiated by placing three quadripolar catheters (Biosense Webster, Inc, Diamond Bar, CA) in the right atrium, the bundle of His area, and the right ventricular apex. Through the left subclavian vein, a decapolar catheter (Biosense Webster) with a lumen was placed in the coronary sinus. Overall, mapping and ablation was performed with a 4-, 8- (Biosense Webster), or a 3.5-mm irrigated-tip Navistar catheter (Thermo-cool, Biosense Webster). CARTO three-dimensional mapping (Biosense Webster) was used for navigation, mapping, and ablation.
Specifically, the suspected atrial tachycardias were initially mapped in the right atrium using CARTO three-dimensional mapping, and in the majority of instances, entrainment was performed from the right atrial isthmus as well as through the distal coronary sinus. If entrainment or right atrial mapping indicated a left atrial origin of the tachycardia, transseptal catheterization was performed for left atrial mapping and ablation. Transseptal catheterization was performed using fluoroscopic guidance, pressure monitoring, and on occasion, intracardiac ultrasound. Intravenous heparin was given with the goal of maintaining activated clotting time at more than 350 second. Because all tachycardias studied were either macro reentrant or focal tachycardia, no attempts were made at pulmonary vein isolation.
If a focal atrial tachycardia was suspected, it was mapped using the CARTO three-dimensional mapping and ablated at the site of earliest activation. For macro reentrant tachycardia, the critical isthmus was identified with the help of entrainment mapping, and ablative lesions were delivered across the isthmus with the goal of terminating the tachycardia.
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Results |
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Two hundred five patients were available for analysis at 12 months, and 130, at 24 months. The overall return to sinus rhythm rate by electrocardiography and Holter monitoring at 12 months was 87% (78% off antiarrhythmic drugs) and 84% (73% off antiarrhythmic drugs) at 24 months.
Perioperative mortality was 3% (n = 12), with an additional 23 (6%) patient deaths during a mean follow-up of 24.1 months (5 cardiac-related, 10 noncardiac, and in 8 patients the cause is unknown).
Sixteen patients (4%) were referred for a subsequent percutaneous RFA for intractable atrial arrhythmias. Interestingly, an additional 4 patients were found to have recurrent atrial tachycardia with very minimal symptoms and were managed medically.
The group of patients referred for catheter ablation is a unique group that may be considered by some as a high-risk group for recurrence of atrial arrhythmia after surgical ablation, in which 25% (n = 4) of the patients had a pacemaker with or without AV nodal ablation before surgery, 31% (n = 5) had a previous cardiac surgery to include 3 with complex congenital anomalies, and 38% (n = 6) had at least one catheter ablation before surgery.
The average age at time of surgery for this group was 61.2 ± 14.7 years. Before surgery, 11 patients (69%) had longstanding persistent atrial fibrillation, and 5 patients (31%) had persistent atrial fibrillation. The mean left atrium size was 4.7 ± 0.6 cm. There were no subsequent reported thromboembolic events for this group with a mean time to follow-up of 42.87 ± 9.8 months. The average time to ablation was 16.9 ± 10 months.
A total of 24 RFA catheter procedures were performed (Fig 1), in which only 10 patients required a single intervention.
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After the first RFA intervention, 6 patients continued to have significant symptoms related to atrial arrhythmias, indicating the need for a subsequent electrophysiology study and ablation. Of these 6 patients, 2 patients were previously ablated for atypical left atrial flutter after the surgical ablation, and both continued to experience significant events of atypical flutter necessitating an ablation of the AV node. Two patients who had typical right atrial flutter ablation underwent a subsequent ablation for right atrial tachycardia.
Of the 2 remaining patients in the group that required a second catheter ablation, 1 patient with previous biatrial ablation for biatrial tachycardia continued to be symptomatic, and 1:1 conduction of atrial tachycardia was diagnosed, leading to AV nodal ablation. An additional patient who initially had ablation to treat right atrial tachycardia underwent a subsequent ablation for recurrence of right atrial typical flutter.
One patient did require a third electrophysiology study and ablation for recurrent right atrial tachycardia and underwent an AV nodal ablation and pacemaker placement (Fig 1).
Interestingly, during the repeated catheter interventions none of the patients mapped were found to have a pulmonary vein source for the arrhythmia, and all veins mapped were found to be electrically silent. We are intrigued by these findings in light of not acutely testing for conduction block in these patients. Therefore, it would be impossible for us to comment on the importance of such acute testing and its predictive value for long-term success.
The success rate for the 16 patients who underwent catheter ablation as captured by electrocardiography at their last known follow-up was 94% with a mean time to follow-up of 42.87 ± 9.8 months. At last follow-up, 53% of the patients (n = 8) in sinus rhythm were still taking antiarrhythmic drugs, with 47% of patients remaining on warfarin. One patient (6%) died owing to a noncardiac cause, and there were no reported thromboembolic events (mean time of follow-up, 42.87 ± 9.8 months). In addition, 4 other patients required a pacemaker: 1 in the immediate postoperative period for severe bradycardia and 3 in the later postoperative period for tachy-brady syndrome. All patients labeled as successes in this special subgroup of patients are still to be considered as a failed surgical ablation per the Heart Rhythm Society guidelines [9]; however, the study shows a reasonable success rate after the subsequent intervention when the majority of the patients present a significant challenge.
Because the average time to first ablation was 16.9 ± 10 months, the first reported assessment of the health-related quality of life for the RFA group was at 24 months after surgery (n = 10), and it showed no statistical difference in their scores for physical functioning (CPS), mental state (CMS), and perception of their overall general health (GH) when compared with the patients after surgical ablation who did not have a catheter ablation and were in sinus rhythm (n = 117). For both the ablation and nonablation groups the average CMS (55.56 ± 6.57; 54.56 ± 7.34) and GH (51.21 ± 5.6; 51.35 ± 9.59) scores were greater than the norm-based mean of 50. There was no statistical difference between groups for their CPS (44.62 ± 10.87; 47.87 ± 10.15); however, neither group reached the norm-based mean of 50.
This same pattern held for reporting of their health-related quality of life at 36 months. For both groups (n = 8 and n = 80) their GH (50.13 ± 11.73; 52.11 ± 10.80) and CMS (57.36 ± 8.7; 54.38 ± 9.18) remained higher than the norm-based mean of 50, but were not statistically different from each other. The CPS was documented to be slightly below the norm-based mean of 50, but not statistically different, with no difference between groups although incrementally both groups improved (47.24 ± 9.42; 49.52 ± 9.19).
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Comment |
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Our findings suggest that in a certain subset of patients the surgical treatment of atrial fibrillation may result in highly symptomatic atrial arrhythmia, which can be safely and effectively addressed with catheter ablation. A relatively high success rate should be expected when combining the two modalities of treatment, catheter and surgical ablation, for atrial fibrillation, especially in a more challenging subset of patients such as reported in this study and more specifically patients with previous surgical treatment for congenital heart disease.
The long-term success of surgical ablation to include the Cox maze III procedure varies. Previous reports [11, 12] demonstrated that the extent of the ablation as well as specific lesion pattern may have a significant impact on the results. The reported success rate is also dependent on the type of follow-up and its duration. Significant numbers of publications deal with a relatively small number of patients and with a relatively short follow-up of several months to 1 year. We believe that despite the importance of longer follow-up, the shorter periods of follow-up represent the significant challenges of maintaining a longer period of follow-up [13–15]. In our program, we have established a comprehensive protocol that allows us a detailed and complete follow-up on a large scale of patients [16].
In this report we describe a very interesting group of patients in which we were able to address recurrence of atrial arrhythmia with catheter ablation. When taking into consideration the traditional risk factors for failed surgical ablation [17–19], this group of patients comprises patients with a lower risk to have a recurrence; however, 63% (n = 10) of the patients had either undergone previous open heart surgery or catheter intervention before the surgical ablation procedure. Although it is still unclear what the real impact of previous interventions on the success rate of the surgical ablation is, it makes sense to assume in some of these patients that excessive scarring may lead to late atrial arrhythmias. In fact when we compared this group with our total surgical ablation group, we found that this group had significantly more interventions before their surgical ablation than the total group: 37% had had a least one prior ablation compared with only 15% in the total group (p = 0.0161), 63% had undergone at least one cardioversion as compared with only 31% in the total group (p = 0.0078), and 50% had a previous cardiac surgery interventions as compared with only 24% in the total group (p = 0.0177). It is of importance to mention that none of the patients mapped were found to have the source of the arrhythmia within the pulmonary veins. These findings are unique and different from some of the reports in the literature and should lead us to study atrial tissue scarring and remodeling in more depth [20, 21].
In our series, the success rate at 1 and 2 years suggest that about 15% of the patients have documented atrial arrhythmias. Catheter ablation was offered to symptomatic patients who failed medical treatment. In 4 patients an AV nodal ablation and a pacemaker was offered after postsurgery catheter ablation failed to control atrial tachycardia and rapid ventricular response rate. Interestingly, 3 of the 4 patients having AV nodal ablation were found to be in sinus rhythm as determined by electrocardiography. No major complications were reported, and in longer-term follow-up there was one death reported to be noncardiac-related. For the 16 patients, electrocardiographic assessment revealed significant success; however, about 50% of the patients are still being controlled with antiarrhythmic drugs and being kept on warfarin. However, we believe that the success is significant mainly because all the patients in this group experienced significant symptomatic atrial arrhythmias before the catheter intervention. Although the number of patients is small, we are encouraged by the relatively good reports on their respective quality-of-life surveys.
Limitations of the Study
In this study we report the success rate after catheter ablation (n = 16) based on electrocardiography only. It is clear to us that the use of longer-term monitoring may show a higher rate of atrial arrhythmia [22]. However, it is important to keep in mind that these patients treated were all highly symptomatic with their atrial arrhythmias after the surgical procedure, and after the ablation their clinical status was improved significantly. Pacemaker interrogation (n = 10) showed that 63% of the patients were indeed in stable sinus rhythm; however, pacemaker interrogation interpretation is complicated when atrial mode switching is occurring.
In addition, the surgical procedure was performed using different combinations of energy sources. It may be important to study the potential differences in outcomes between the two techniques; however, this was not the scope of this study, and the number of patients may be too small to draw a scientifically sound conclusion.
Conclusions
In a certain subset of patients unsuccessful surgical ablation of atrial fibrillation may result in symptomatic atrial arrhythmias. We believe that when indicated, subsequent catheter ablation should be considered. We found that this modality of intervention was safe and effective with a relatively high success rate. The combination of the two treatment modalities, catheter and surgical ablation, can improve the outcome even in a very complex subset of patients.
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Discussion |
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Interestingly enough, in Circulation 2 years ago, there was a nice report on postablation tachycardias from the cath lab, 16 patients, much like yours. All of those patients were found to be reentrant tachycardias from the left side; none of them were right-sided reentrant tachycardias. Most of the tachycardias centered on the mitral isthmus. In your group of patients, over half the tachycardias originated from the right side. All these patients had right-sided lesions except for 1, which was a patient who underwent pulmonary vein isolation. So my question is, do we know that the right-sided lesion set is actually favorable in patients with atrial fibrillation? If patients with right atrial lesion sets have an increased risk of reentrant tachycardia from the right-sided ablation as well as an increased risk of pacemaker implantation over patients with left-sided lesion set alone, should we be performing right-sided ablation? When one considers the additional risks of right-sided ablation and a recent randomized trial showing no difference in efficacy between biatrial and left atrial ablation reported in the European Journal of Cardiothoracic Surgery by Dr Wang et al, there seems to be a case for avoiding the biatrial approach.
My second question is in reference to your thoughts regarding the hybrid approach for treating atrial fibrillation. We are seeing increased interest in the hybrid approach where an epicardial surgical ablation is performed and then at the same procedure endocardial catheter-based ablation is also performed. Since a number of these reentrant tachycardias, representing gaps and macroreentry around those gaps, that you have described will become evident after the scar from the ablation has matured, is it not better to separate the two ablation procedures by some time to allow these gaps and reentrant tachycardias to become mappable and then able to be taken care of in the EP (electrophysiology) lab at the time of an initial catheter-based procedure? It just seems to me that the current single epicardial and endocardial ablation sequence will result in additional catheter-based procedures to take care of late reentrant tachycardias.
I would like to thank the Society for the invitation to discuss this paper.
DR AD: Thank you, Mark. As usual, excellent questions. Well, the focus of the study is not on the type of arrhythmia; it is on the approach. I can tell you that the 400 patients were done by multiple surgeons initially. There were some relevant differences between surgeons, and we are trying to solidify the approach to treat our A-fib (atrial fibrillation) patients, without major deviations, but yet only 7 out of 400 had a right-sided issue, which is very little. Interestingly enough of those patients, we had 3 patients with complex congenital anomalies, all of them had right atrial issues, and the only patient who had PVI (pulmonary vein isolation) had right atrial issues. So 4 out of the 7 with right atrial arrhythmias can be well explained. The other 3 I think that we can explain by using a lower dosage of cryothermal energy. When we moved from the Frigitronics to the argon-based CryoCath, we were recommended to freeze only for 1 minute, and 2 out of the 3 patients with the right-sided arrhythmias were treated with an underdosage of cryo. So I believe that this may explain better your concerns and your point is well taken. But as mentioned this was not the focus of the study. The focus is that these arrhythmias are highly symptomatic and need to be addressed aggressively and not just with an AV (atrioventricular) node ablation and pacemaker placement.
The other comment is actually very important, and I am actually going back and forth on the hybrid approach. However, we have to keep in mind that we have to work together with the electrophysiologists on this issue. Otherwise we are going to be staying by ourselves doing 5 to 10 cases a year and help fewer patients. Therefore we have to be able to develop some protocols and look at this problem prospectively in a very serious way, whether to space the procedures, whether to do it together, what type of protocol to use, et cetera, et cetera. My personal thought is that we should move forward and participate in all those collaborations provided we can use sound techniques and reliable devices to create transmural lesions that as you know none of the RF (radiofrequency) devices is a good fit.
DR DWIGHT E. HAND (Cincinnati, OH): Was there any attempt at the time of the ablations in the cath lab to actually map the site of the failure? Can we say with any assurance that it was the site of the cryolesions and not the site of the bipolar radiofrequency lesions?
DR AD: That is an excellent point. That is a question I ask. Except for 2 patients with a redo operation that was certainly related to some scar from a previous cannulation site, I can't really comment on that. The one very interesting point in my mind was that none of the patients were mapped to have any issues within the pulmonary vein, which is a little different than the big series from Italy, from the Cleveland Clinic, and others. That is a very good point and we don't really have a good answer.
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References |
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