Abstract
- 1.
Antitachycardia pacemakers can be an important adjunct therapy in select patients with atrial arrhythmias unresponsive to medications, ablation, and surgery. It can reduce arrhythmia duration, arrhythmia burden, the number of emergency room visits and hospitalizations.
- 2.
In patients with antitachycardia pacemakers, amiodarone (and other antiarrhythmic therapy) can slow the atrial arrhythmia sufficiently to make the antitachycardia pacing effective.
- 3.
In general, repeat ablation procedure should be attempted in such patients except in situations such as interrupted IVC.
Case Synopsis
This case involves a 33-year-old woman with complex congenital heart disease consisting of heterotaxy with a single systemic right ventricle, pulmonary artery atresia, and an interrupted inferior vena cava (IVC) with hemiazygous continuation to a persistent left superior vena cava (SVC) ( Fig. 12.1 ). She is status postpulmonary artery banding, creation of bilateral bidirectional cavopulmonary anastomoses (Kawashima procedure), creation of a lateral tunnel Fontan, right atrial plication, and tricuspid valve repair. She presented to the emergency room multiple times for recurrent episodes of tachycardia ( Fig. 12.2 EKG). She was started on amiodarone but continued to have recurrent episodes. She then had an electrophysiologic study where three distinct atrial flutters and a focal atrial tachycardia were induced ( Fig. 12.3 EGM). Subsequently, she underwent a biatrial maze procedure and implantation of a dual chamber antitachycardia pacemaker (Medtronic EnRhythm model P1501DR) with epicardial lead placement and an abdominal generator ( Fig. 12.4 ); however, the initial generator was faulty and required replacement.
During normal operation, the pacemaker delivers ATP if the atrial rate is above the atrial detection rate. However, the device also assesses the atrioventricular (AV) relationship and can only deliver ATP if the atrial rate is faster than the ventricular rate. Therefore ATP would not be delivered for atrial arrhythmias with a 1:1 AV relationship. Because of this software limitation, the pacemaker was loaded with custom software from Medtronic (TPARx) under compassionate use allowing patient-activated ATP. At the onset of symptoms, the patient presses a button on a wireless transmitter that starts a timer (typically 30 min). During this period, the pacemaker suspends the AV relationship criteria and delivers ATP for atrial rhythms above the atrial detection limit. The pacemaker returns to normal operation once the atrial arrhythmia ends or the timer expires. Placing a magnet over the device will also stop delivery of therapy by TPARx.
Following pacemaker implantation, atrial arrhythmias with a 1:1 AV relationship were documented during pacemaker interrogation ( Fig. 12.5 ). The pacemaker did not initially deliver ATP after patient activation because the heart rates were below the atrial detection limit. Once the atrial detection limit was lowered, ATP was able to be delivered with patient activation. The TPARx software has successfully terminated the patient’s subsequent atrial arrhythmias ( Figs. 12.6 and 12.7 ).
Questions
- 1.
Is there a role for repeat ablation in this patient?
- 2.
What would be the challenges to another ablation attempt and how to go about ensuring success?
- 3.
Would you continue amiodarone? If yes, why? If no, why not?
- 4.
Is there a different drug that you would try?
- 5.
Is it acceptable to leave the patient with current ATP management?
- 6.
Are there any downsides to ATP management and how can we minimize those?
Consultant Opinion #1
- Charlotte A. Houck, MD
- Natasja M.S. de Groot, MD, PhD
This case represents a patient with complex congenital heart disease who underwent multiple palliative surgical procedures and who presented with symptomatic postoperative atrial tachyarrhythmias. Several attempts were made to treat these atrial tachyarrhythmias, including antiarrhythmic drug therapy with amiodarone, a biatrial Maze procedure, and finally, implantation of a dual chamber antitachycardia pacemaker. Antitachycardia pacing with patient activation successfully terminated atrial tachyarrhythmias in this patient.
Multiple treatment modalities for postoperative atrial tachyarrhythmias have been described in patients after Fontan-type surgery, including antiarrhythmic drug therapy, antitachycardia pacing, conversion surgery, arrhythmia surgery, and catheter ablation.
Postoperative Atrial Tachyarrhythmias in Fontan Patients
Atrial tachyarrhythmias are the most commonly observed postoperative arrhythmias after Fontan-type surgery, occurring in up to 50% of patients by 20 years of follow-up. Risk factors for development of atrial tachyarrhythmias in Fontan patients include right atrial enlargement, elevated atrial pressure, dispersion of atrial refractoriness, sinus node dysfunction, older age at the time of cardiac surgery, elevation of pulmonary pressure, low oxygen saturation, preoperative arrhythmias, prior palliation with an atrial septectomy, AV valve replacement, and aging.
Macroreentrant circuits involving the right atrium are most often observed ( Fig. 12.1 ). However, in lateral tunnel-type repairs, a part of the anatomic right atrium (and thus the reentrant circuit) may end up in the pulmonary venous (left) atrium after surgery. Slowed conduction with reentry is facilitated by both anatomic and surgical barriers. Anatomic barriers include the orifices of the inferior and SVC, the ostium of the coronary sinus, and an atrial septal defect. Scar tissue, suture lines, and prosthetic materials form surgically induced barriers. Patients with a Fontan circulation often have multiple reentry circuits because of the extensiveness of areas of scar tissue that are scattered throughout the dilated atria. Follow-up of patients with lateral tunnel and extracardiac Fontan modifications show that patients with lateral tunnel repair experience more atrial tachyarrhythmias, consistent with the increased placement of suture lines in this procedure.
Focal atrial tachycardias have also been described in Fontan patients, although infrequently. A focal atrial tachycardia is defined as an atrial tachycardia originating from a circumscribed region from where it expands centrifugally to the remainder of the atrium, as demonstrated in Fig. 12.2 . Whether these tachycardias are caused by ectopic activity or microreentry remains questionable. Atrial fibrillation also occurs in patients with a Fontan circulation and this arrhythmia tends to occur at a much younger age (28 ± 9 years) in Fontan patients than in the normal population.
- 1.
Is there a role for repeat ablation in this patient?
- 2.
What would be the challenges to another ablation attempt and how to go about ensuring success?
Catheter Ablation
Catheter ablation is a good alternative in case of failure or adverse effects of medical therapy. Although numerous studies have reported ablation outcomes in patients with a variety of congenital heart diseases, only a few studies assessed results of catheter ablation in Fontan patients specifically. Outcomes of these studies are summarized in Table 12.1 . Acute success rates of ablative therapy for atrial tachyarrhythmias are variable and follow-up after catheter ablation is complicated by many recurrences. Successive atrial tachyarrhythmias developing over time may be caused by different mechanisms. It is most likely that recurrences of atrial tachyarrhythmias are caused by a progressive atrial cardiomyopathy instead of an unsuccessful ablation procedure or arrhythmogenicity of prior ablative lesions.
| Reference | Patients (N) | At Circuits (N) | Acute Success | Follow-Up | Recurrence |
|---|---|---|---|---|---|
| Betts et al. | 5 | 11 | 60% | 6.4 mo | 67% |
| Weipert et al. | 30 | – | 83% | 1.7 y | – a |
| De Groot et al. | 19 | 41 | 78% | 53 mo | 60% |
| Yap et al. | 11 | – | 45% | 2.3 y | 47% |
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