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Eur J Cardiothorac Surg 1999;15:525-527
© 1999 Elsevier Science NL

Multicenter results of TADpole^TM heart wire system used to treat postoperative atrial fibrillation¹

European Multicenter Study Group, Department for Cardiovascular Surgery, Herz-Kreislauf-Klinik Bevensen, Römstedter Str. 25, 29549 Bad Bevensen, Germany

Received 23 September 1998; received in revised form 31 December 1998; accepted 13 January 1999.

Corresponding author.

	Abstract

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Objective: Postoperative atrial fibrillation (AF) affects 20–30% of patients undergoing open-heart surgery, delays mobilization and impairs hemodynamics. Implantation of TADpole^TM Heart Wires offers a new method of applying internal low-energy-shocks to terminate AF. The safety and efficacy of the TADpole^TM system to treat postoperative AF was evaluated in this multicenter trial. Methods: Two atrial wires, configured with a highly flexible 11.5 cm distal shocking and a 0.5 cm proximal pacing electrode were sutured onto the right and left atrium. Upon detection of AF, R-wave synchronized low-energy-shocks were administered via an energy attenuating External Defibrillator Interface Module or ICD programmer. Results: A total of 296 patients (65±9.2 years, 74.7% male) have been enrolled to date in six European centers. The wire placement time was 4.2±2.2 min, 65 patients had a total of 83 episodes of AF treated by the TADpole^TM Heart Wire system with a conversion rate of 88.5% (approximate energy of 6±2 J), early recurrence of AF was observed in ten patients (12.8%). No clinical complications were reported. The shocks were well tolerated with slight sedation. The ease of withdrawal was 2.3±1.2 on a graded scale of 0 (easy) to 10 (difficult). Conclusions: These multicenter results indicate that postoperative atrial cardioversion using TADpole^TM Heart Wires is both safe and efficient. It is expected that hospital length of stay and its associated economic impact can be reduced with this therapy.

Key Words: Atrial fibrillation • Cardioversion • Open heart surgery

	Introduction

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Approximately 20–30% of all patients undergoing open heart surgery and extracorporeal circulation suffer from atrial fibrillation mostly between the 2nd and 4th postoperative day [1] [2]. Although the prognosis of this rhythm disturbance is generally good, most patients return to normal sinus rhythm within 48–72 h, mobilization is delayed during the AF period and hemodynamics may be impaired especially in patients with reduced left ventricular function. Conventional treatment of postoperative AF consisted of antiarrhythmic medication, mostly Verapamil, beta-blockers [3] and amiodarone [4], and in severe cases external defibrillation under general anesthesia with the well-known side effects.

Since June 1997, a new device for internal cardioversion of postoperative AF has been available, the TADpole^TM heart wire system (InControl GmbH). It consists of two epicardial wires with a highly flexible distal defibrillation electrode and a proximal pacing electrode. The energy can be supplied by an ICD programmer or via an energy attenuating External Defibrillator Interface Module (EDIM). The EDIM reduces the energy delivered by an conventional external defibrillator to 3% of the energy. Thus low-energy cardioversion shocks with 3–9 J can be administered to the patient with any available defibrillation device.

The two wires are placed on the right and left atrium in order to include a maximum atrial muscle mass [5].

	Material and methods

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The pilot study was designed to investigate safety and efficacy of the TADpole^TM system. During heart operations, being mostly coronary bypass grafting, two epicardial wires were placed on the left and right atrium. The implantation had to be easy and fast with a wire length of more than 5 cm in touch with the atrial wall. Epicardial and pericardial fixation were allowed, the fixation was supposed to be spread widely over the atrium to avoid hot spots. A maximum atrial muscle mass should be included, the extraction had to be easy and quick.

On occurrence of AF, R-wave synchronized low energy shocks were administered via the Interface module in 66%, or other devices in 34%. Sedation was not mandatory, but given in most cases. The extraction of the wires was performed on the 6th postoperative day.

	Results

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Up to now, 296 patients were included in the pilot study with a mean age of 65±9.2 years. Sex (74.7% male, 15.3% female) and NYHA-classification (mean 2.8±0.7) showed a normal distribution. 65 patients (22%), suffered from AF postoperatively.

The wire placement time was 4.2±2.2 min, 4.8±2.3 stitches were performed on the right atrium, 3.9±2.4 on the left atrium. The implanted wire length was 9.3±2.3 cm on the right and 8.6±1.8 cm on the left atrium.

In the 65 patients with AF, a total of 83 episodes of AF occurred. Forty-nine patients had one, 14 had two and two patients had three episodes of AF. The time interval from the onset of AF to cardioversion was 337 min, a mean of 2±1.3 shocks were administered per episode. Mean energy of the first shock was 4.3±1.3 J. If this first shock did not lead to sinus rhythm, a second shock of 6.4±2.0 J, and if necessary a third shock of 8.4±1.7 J were given.

Of the 83 AF-episodes, three returned to sinus rhythm without any therapy and two could be converted by medication alone. In 78 episodes (93%), internal cardioversion via the TADpole^TM system was performed.

Successful cardioversion was achieved in 69 of the 78 episodes or 88.5% (Table 1). Early recurrence of atrial fibrillation within one minute after a primarily successful cardioversion shock occurred though in ten episodes, so that the total clinical success rate with a stable sinus rhythm was 75.6%. ERAF appeared to be the greatest problem in the performance of the TADpole^TM system [6].

Concerning wire extraction, the physicians were asked to assess ease of extraction on a scale from 1 to 10. 1 was `extremely easy' and 10 `extremely difficult' The mean result was 2.3±1.2. Discomfort of extraction was assessed by the patients from 1 `no discomfort' to 10 `extreme discomfort'. Again the mean result was very low with 2.2±1.2. Extraction complications have not been reported.

	Conclusions

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In conclusion, these results of a multi-center trial indicate that the TADpole^TM heart wire system is both safe and efficient for treatment of postoperative AF following open heart surgery. This includes wire placement, cardioversion performance and extraction. No proarrhythmic event has been reported.

Additional research into wire placement, configuration and time point of shock delivery may even more improve efficacy and reduce incidence of early recurrence of atrial fibrillation. It is expected that hospital length of stay and its associated economic impact can be reduced with this therapy.

	Footnotes

 
Presented at the 12th Annual Meeting of the European Association for Cardio-thoracic Surgery, Brussels, Belgium, September 20–23, 1998.

	Appendix A. Conference discussion

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Dr N. Stolf (Sao Paulo, Brazil): We I don't have the system available. We are trying to minimize the incidence of atrial fibrillation in other ways. I think that the most important question and the major concern is about the price of the device, the wires and the equipment itself, if you could clarify this point.

Dr Kleine: Yes. For the study itself, the price of the wires was the same as for the wires we normally use for pacing after open heart surgery, but in the future it may be approximately double as high as the normal pacing wires.

Dr J. Melo (Carnaxide, Portugal): You have a sequence for your options of treating atrial fibrillation, if I understood correctly from your diagram. So you start first from medication and, if it doesn't work, it goes to the antiarrhythmics. What is that option?

Dr Kleine: The experience we have made if you use the TADpole^TM system and cardiovert the patient immediately after onset of atrial fibrillation, you have a very high rate of early recurrence (50%). So that is why we treat the patient for 6 h with antiarrhythmics. Normally we use Verapamil, in other cases we use sotalol, and after 6 h we then cardiovert the patient, then the success rate is much higher. After a success, we continue with antiarrhythmic medication for another 24 h and then stop it.

Dr Melo: When you need to defibrillate, what kind of cautions do you use? Do you sedate the patients? What is the procedure for when you reach the point of defibrillating?

Dr Kleine: In this study, sedation was not mandatory but given to most patients. In our clinic, all patients have been slightly sedated, but they have not been transferred to an intensive care unit. It was done on an intermediate care unit.

Mr N. Moat (London, UK): It is a very interesting idea. Can you use these wires to pace the patient and how does the ease of extraction compare with removing ordinary standard epicardial wires? Is it the same or more difficult? And what sort of anticoagulation protocol do you use either before cardioversion and after cardioversion?

Dr Kleine: We usually have our patients on low-dose heparin at that time point and we have no extra anticoagulation during the AF period. Ease of extraction is completely the same as in normal pacing wires.

Mr Moat: With the anticoagulation policy, though, do you not anticoagulate the patients after cardioversion, because you are likely to have atrial stunning and possibly an increased risk of thrombus formation after you've cardioverted the patient.

Dr Kleine: No, we don't.

Mr L. Hamilton (Newcastle, UK): Fascinating idea. You mentioned you sedate the patients before you defibrillate them. What was the patients' reaction to the actual shock? Did they feel it?

Dr Kleine: Yes. I think it is more a kind of a surprise to the patient than really pain, so I think you don't have to use a lot of medication to take away pain. It is more important to sedate him so that he's sleeping during the cardioversion. Also, no patient said he wouldn't allow another shock.

	References

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1. Leitch J.W., Thomson D., Baird D.K., Harris P.J. The importance of age as a predictor of atrial fibrillation and flutter after coronary artery bypass grafting. J Thorac Cardiovasc Surg 1990;100:338.[Abstract]
2. Kirklin JW, Barrat-Boyes BG. Cardiac surgery, second ed. New York: Churchill Livingstone 1993:197–210.
3. Ip J., Grimes D., Etikerentse T., Santoni F., Mehta D., Pe E., Gomes J.A. A prospective randomized placebo-controlled double-blinded trial of Sotalol for the prevention of atrial fibrillation following open heart surgery. PACE 1998;21(4 Part II):812.
4. McAlister H.F., Luke R.A., Whitlock R.M., Smith W.M. Intravenous amiodarone bolus versus oral quinidine for atrial flutter and fibrillation after cardiac operations. J Thorac Cardiovasc Surg 1990;99:911.[Abstract]
5. Kleine P., Haisch G., Rosada B., Liebold A. Surgical technique for implantation of TADpole^TM heart wires for treatment of atrial fibrillation following cardiac operations. Thorac Cardiovasc Surg 1998;46(Suppl. I):227.
6. Kleine P., Machner M., Nolte Th., Schäfer P., Laas J. Early versus late termination of atrial fibrillation following coronary artery bypass grafting using TADpole^TM heart wires for internal defibrillation. PACE 1998;21(4 Part II):649.

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