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Eur J Cardiothorac Surg 2004;26:323-329
© 2004 Elsevier Science NL
a Department of Cardiovascular Surgery, Institute for Clinical and Experimental Medicine, Prague, Czech Republic
b Department of Cardiology, Institute for Clinical and Experimental Medicine, Prague, Czech Republic
Received 10 October 2003; received in revised form 30 March 2004; accepted 31 March 2004.
* Corresponding author. Tel.: +420-60346-8697; fax: +420-24171-7669
e-mail: vlastimil.vancura{at}medicon.cz
| Abstract |
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130 ms were surgically excised or cryoablated. All surviving patients were restudied within one to two weeks after surgery using identical programmed electrical stimulation protocol. Results: Five (6.5%) patients died in the perioperative (30-days) period. In the remaining cohort, inducibility of any sustained VTA after surgical procedure was observed in 21 subjects (29.2%). An implantable cardioverter-defibrillator (ICD) was implanted in these patients. Recurrence of sustained VTA was documented during follow-up period in two patients who were noninducible after the surgery (at the month 10 and 22, respectively), and both received ICD as well. No patient died of sudden cardiac death. In 14 ICD patients, no significant VTA was documented during the mean follow-up of 37.3±23.2 months. Altogether, 61 from the 72 patients surviving the surgery (84.7%) remained free of spontaneous recurrences of VTA during the follow-up. Conclusions: Surgical ablation of an arrhythmogenic substrate guided by simplified intraoperative mapping in normothermic heart during sinus rhythm appears to be both safe and efficacious procedure that prevents recurrences of VTA in a substantial proportion of patients.
Key Words: Sudden cardiac death Ventricular tachycardia Ventricular fibrillation Implantable cardioverter-defibrillator Surgical ablation Cardiac mapping
| 1. Introduction |
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Over a period of the last two decades, electrophysiologically guided surgery of post-infarction VTAs has evolved as one of the viable treatment modalities. Sophisticated mapping techniques allow rapid analysis of the arrhythmogenic substrate and its precise location [4,5]. Excision of the scarred myocardium in subendocardial location has been used as the most useful surgical approach. It has been shown to prevent clinical recurrences of VTA in approximately 90% of patients, despite postoperative inducibility of VTA reaching 2030%. However, previous series have been accompanied by rather high perioperative mortality of 530% [69].
To minimize mortality and maximize the benefit, surgical technique should be a compromise between the preservation of cardiac function and neutralization of the substrate. Consequently, the modern principle of surgical treatment involves cryoablation or excision of a scar tissue as well as revascularization and left ventricular aneurysmectomy with remodelling when indicated. The extent of the mapping and surgery should be therefore tailored to an individual patient. The aim of this study was to evaluate long-term results of surgical ablation of post-infarction arrhythmogenic substrate guided by simplified intraoperative mapping in sinus rhythm.
| 2. Materials and methods |
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2.2. Late potential analysis
A pilot series of 23 consecutive patients underwent both preoperatively and postoperatively signal-averaged ECG recording (MAC 15, Marquette, Milwaukee, WI, USA). Time-domain analysis was performed with a noise level below 0.6 µV and filter setting at 45250 Hz.
2.3. Surgical technique
The operation was performed through a median sternotomy. Epicardial mapping was used in all patients after cannulation for cardiopulmonary bypass and normothermic perfusion. The purpose-built, multielectrode array probe with 16 bipolar electrodes (interelectrode spacing 2 mm, the distance between individual dipoles 8 mm) and the multichannel recording system (ICA 16, HLS Medical Electronic Prague, Czech Republic or CardioLab 4.3, Prucka Engineering, Houston, TX, USA) were used (Fig. 1C)
. Myocardial arrhythmogenic areas characterized by the presence of fractionated, long duration electrograms (
130 ms) in sinus rhythm were identified.
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For cryoablation, repeated application of the purpose-built liquid nitrogen-cooled probe (KCH 5, SMT Prague, Czech Republic) were used (Fig. 2A) . The equipment consists of a control unit and a hand-held probe with the container of liquid nitrogen. The freezing tip is supplied in various shapes and diameters. After its placement at the target site, temperature of 190 °C was applied for 23 min with subsequent active warming.
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2.4. Postoperative evaluation
All of the 72 survivors of the surgery underwent a control PES, using the identical protocol as preoperatively. The study was performed within one or two weeks after the surgery. Acute success of surgical ablation was defined by the absence of spontaneous VTA in postoperative period and by noninducibility of any sustained VTA during PES.
All 23 subjects who underwent signal-averaged ECG recording before the surgery were restudied before hospital discharge using the identical equipment and setup.
2.5. Follow-up
All patients were scheduled for regular out-patient visits at an interval of 6 months. Patients with implanted ICD were followed every three months. The long-term success of the procedure was defined by the absence of spontaneous sustained VTA and/or sudden cardiac death following hospital discharge.
2.6. Statistical analysis
The data are expressed as a mean±SD. The differences between patient groups were analyzed using Fisher's exact test or
2 test, when appropriate. A P value <0.05 was considered as statistically significant.
| 3. Results |
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Patients without an indication for ventriculotomy underwent only epicardial cryoablation. The mean number of cryolesions per patient reached 3.7±1.3. The remaining subjects underwent ventriculotomy and endocardial mapping. The median of endocardial mapping sites with a multiarray probe was 4. Subsequently, aneurysmectomy and/or subendocardial resection were performed with additional cryoablation of the transitional zones. The concomitant surgical procedures performed after surgical ablation are listed in Table 2.
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| 4. Discussion |
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The overall success rate of arrhythmia surgery in our series reached 70.8% with perioperative mortality of 6.5%. Although epicardial cryoablation alone tended to lower acute success rate as compared to more extensive ablation through left ventriculotomy (63.3 vs 76.2%, P<0.23), it was associated with more favorable perioperative mortality trend (3.3 vs 9.5%, P<0.30). Other authors reported acute success in abolition of all inducible VTAs within the range of 6392% and mortality ranging from zero to 24% [514].
When comparing the effectiveness and safety of different approaches in prevention of the recurrences of life-threatening VTA, it is important to stress the role of coronary artery bypass surgery alone. Some authors showed that myocardial revascularization adds very few to prevention of postinfarction VTA [15,16]. On the other hand, other studies documented that coronary artery bypass surgery has an additive role in the secondary prevention of sudden arrhythmic death [1719]. Specifically, inducibility of ventricular tachycardia or ventricular fibrillation was suppressed in about 3545% of patients after bypass surgery [15]. Nevertheless, mortality associated with this approach without specific arrhythmia surgery may still remain relatively high (more than 22% during a mean follow-up interval of 55 months) with a total of 55% of deaths classified as sudden [20]. Therefore, coronary artery bypass surgery itself does not seem to be effective enough to protect the majority of patients with previously documented VTA from its recurrence.
The lower success rate of epicardial cryoablation in our series may reflect the location of the reentrant circuit within the myocardial wall. Although a relatively high proportion of circuits is localized in epicardial region [21,22] and thus, easily accessible from epicardial approach, other are confined solely to the subendocardium, beyond the reach of epicardial cryoablation. Furthermore, the more extensive arrhythmia surgery is likely to be more effective in abolishing VTA as compared with our less invasive approach [23]. This is also confirmed by the data from our pilot substudy of signal-averaged ECG recordings. It showed significant changes in duration of filtered QRS duration after the successful surgery and this is in concordance with the concept of more extensive substrate modification. On the other hand, such an aggressive approach carries a higher significant risk of associated mortality [9,11,12].
Success rate of surgical ablation of arrhythmogenic substrate is also influenced by the mapping accuracy. Precise identification and location of arrhythmogenic substrate for monomorphic VTA requires mapping during tachycardia and this, in turn, increases both the complexity and risk of the procedure [6,7,21]. To overcome this dilemma, various simplified techniques of identification of arrhythogenic tissue continue to be investigated. Some of them are based on anatomical landmarks [9,14] while the other rely on endocardial mapping in sinus rhythm [10]. The latter approach of sinus rhythm mapping is based on the concept that the substrate can be detected by an analysis of low amplitude, fractionated electrograms. These pathological signals appear to reflect anatomic derangement and uncoupling of myocardial fibers [24] and thus, represent potentional targets for ablation [1,2,25].
Interestingly, when analyzing different patient populations we found a trend to higher acute success rate for patients who presented with polymorphic ventricular arrhythmias or ventricular fibrillation as compared to the subjects with documented monomorphic ventricular tachycardia (81 vs 66.7%, P<0.22). The difference may be explained by the fact that polymorphic VTA are more often triggered by ischemia in contrast to monomorphic VTA associated with arrhythmogenic substrate. In the former group, myocardial revascularization appears to play important role in prevention of VTA.
During long-term follow-up, our strategy to arrhythmia surgery resulted in overall clinical control of VTA in 86% of patients. Compared to a large series of University of Pennsylvania [11] in which extensive perioperative mapping and subendocardial resection were used, mortality in our cohort was lower (6.5 vs 15%) despite very similar percentage of clinically controlled VTA in long term follow up (84.7 vs 93%). Other series [5,7,13,14] also showed better long term clinical control of VTA than was the success rate predicted by early postoperative testing. Such finding may reflect the positive long-term effect of myocardial revascularization and ventricular remodelling on electrical stability of the ventricular myocardium.
| 5. Conclusions |
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| Acknowledgments |
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| Footnotes |
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| Appendix A. Conference discussion |
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Dr Pirk: We don't make the induction of the tachycardia.
Dr Bockeria: Why?
Dr Pirk: Why? It is danger for the patient and we don't see any reason. We don't do it. That is the aim of the study. We do it in sinus rhythm and we find the focus. We don't need to induct tachycardia during surgery. It is a simplified, easier method.
Dr F. Mohr (Leipzig, Germany): May I ask in terms of your time frame, I think the experience we see is that we hardly see patients for such procedures anymore because usually they are treated by ICD treatment and are no longer referred for surgery. And you showed us your 105, if I recall it right, patients, out of a period of eight to nine years. Is there a difference in referral rate, is it an increasing number in your hospital, or is it something which is historical, as it is in our units?
Dr Pirk: No. Of course, the cardiologists are in favor to insert the defibrillator. It is easy but is a symptomatic treatment and it can have dangers.
We are trying to convince the cardiologists that this is the treatment, to find the focus, to eliminate or isolate the focus, and you cure the patient. It is not a symptomatic treatment. So I would say we have more patients.
And there is one regulation in the Czech Republic. The defibrillator is a very expensive device. So there is a committee, and every patient, before it is indicated for a defibrillator, his material must be sent to this committee, and they review all the things and they say, no, this patient can be treated by surgery or by catheter ablation, and only if this is not the case, then it is an indication for a defibrillator. So we are trying to go the other way.
Dr Mohr: You are lucky.
Dr Pirk: The patients are lucky.
Dr A. Revishvili (Moscow, Russia): I would like to ask the question about EPI study because you didn't show us what kind of tachycardia you had during surgery, how many patients in ventricular tachycardia or atrial fibrillation. During heart mapping you may have 35%, which you will want to cryoablate all the surfaces. What is the real target for your surgery?
Dr Pirk: I could not show it. We have much more data, which hopefully will be published in the paper. About 12% of the patients had a history of ventricular fibrillation. All the other patients had a history of sustained ventricular tachycardia with hypotension and with resuscitation.
Dr Revishvili: Did you induce any arrhythmia during EPI study?
Dr Pirk: Not during the surgery. In the cath lab with the programmed electrical stimulation they have been trying to do the tachycardia, and in 97 patients they were successful with evoking the tachycardia. I didn't mention this, but all the patients, of course, were on amiodarone and beta blockers and full medication before. Because of the time I could not mention everything.
Dr L. Bockeria (Moscow, Russia): I would like to say just a few words about the tendency we saw today and those who are still active in the area of arrhythmia surgery. So, what to do, maze procedure or radiofrequency ablation? This is a question which should be addressed by any surgeon to himself, because in case we have better results with a pure maze procedure, I guess we should recommend to a patient to do the type of procedure in a place where it is done. That is what we see normally now in Moscow at our hospital, which is doing a pretty big number of cases.
The second point is concerning the last presentation. Yes, the cardiological approach killed this area of surgery, radical treatment, but it is my opinion also that in hospitals where they have an experience for this type of surgery, it should be used widely as soon as we know that this approach in experienced hands has many privileges.
When we go to radiofrequency ablation or when we use implantable cardioverter defibrillator, we are doing a palliative treatment. It should be, of course, existing in practice, but in general we should consider that the surgical approach should be used in hospitals where electrophysiology is well established, electrophysiology is still active, and where it is possible to treat patients more radically.
And the last one, what I wanted to mention is about autotransplantation of the heart. We used this approach maybe 20 years ago for the patients with long QT syndrome, and at least I remember two patients, a sister and a brother, eight years old. I made for both the autotransplantation of the heart, and they were doing very well. And that is understandable for me; when there is an extracardiac factor, the surgery of this type is logistic. But in cases when we do this for atrial fibrillation, it probably needs further explanation.
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