Minimally Invasive Epicardial Ablation of Lone Atrial Fibrillation in Pediatric Patient

We describe a case of epicardial surgical ablation of drug refractory lone atrial fibrillation in a pediatric patient. Minimally invasive radiofrequency equipment was used off-pump through a right mini-thoracotomy. Electrical isolation of the pulmonary veins cuffs was obtained. The preoperative electrophysiological study identified a macro re-entrant circuit around the pulmonary veins orifices as the mechanism of arrhythmia triggering. At follow-up, the patient is in stable sinus rhythm and there is no evidence of pulmonary vein stenosis. The minimally invasive, off-pump ablation of lone atrial fibrillation is feasible and reliable, even in children who may pose incremental technical challenges. This technique may represent an additional tool for the current treatment algorithms to treat lone atrial fibrillation. We describe a case of epicardial surgical ablation of drug refractory lone atrial fibrillation in a pediatric patient. Minimally invasive radiofrequency equipment was used off-pump through a right mini-thoracotomy. Electrical isolation of the pulmonary veins cuffs was obtained. The preoperative electrophysiological study identified a macro re-entrant circuit around the pulmonary veins orifices as the mechanism of arrhythmia triggering. At follow-up, the patient is in stable sinus rhythm and there is no evidence of pulmonary vein stenosis. The minimally invasive, off-pump ablation of lone atrial fibrillation is feasible and reliable, even in children who may pose incremental technical challenges. This technique may represent an additional tool for the current treatment algorithms to treat lone atrial fibrillation. Atrial fibrillation (AF) is a common supraventricular arrhythmia in the adult population. However it is rarely encountered in the children, mainly if in absence concomitant structural heart disease. Whenever present, AF may be difficult to treat definitively. We describe a case of minimally invasive, epicardial ablation for stand-alone AF in a pediatric patient. We discuss the advantages, the pitfalls, and the potential room of this technique in the treatment algorithms for lone AF. A 12-year-old boy was evaluated for paroxysmal, medically refractory AF. He was asymptomatic for dyspnea, cyanosis, and other signs of heart failure. Transthoracic echocardiography and contrast-enhanced computed tomographic and magnetic resonance scans of the heart ruled out any structural abnormality, congenital defect, and cardiomyopathy. The patient was experiencing episodes of paroxysmal AF, with ensuing tachycardia at an average rate of 2 episodes per week. These were associated with palpitation, near-syncope, and severe, general weakness. Pharmacologic therapy was conducted with oral amiodarone (100 mg once a day for 3 months), followed by oral propafenone (150 mg twice a day), and finally with oral flecainide (150 mg twice a day). The drugs failed to obtain a stable regression of the AF. A transcatheter electrophysiological study revealed a re-entrant circuit at the level of the pulmonary veins cuffs. Elective surgery was conducted under general anesthesia by a right anterolateral mini-thoracotomy in the third intercostal space, with a 3-cm incision. The procedure was completely off-pump, and was conducted while applying gentle downward traction to the middle lobe of the left lung. The pericardium was reached with long instruments and it was incised. The oblique and the transverse sinuses were opened by gentle blunt dissection through the pericardial reflections around both vena cavae. Epicardial ablation was conducted with the Cobra Adhere XL system (Estech Inc, San Ramon, CA). A J-shaped introducer straightened with a stainless steel stylet was first pushed beneath the superior vena cava in the transverse sinus. Once advanced beyond the left atrial appendage, the stylet was then removed and the introducer could resume its curved shape. A second introducer was then advanced through the oblique sinus until the tips of the two introducers were joined with a magnetical connector. Thus, the four pulmonary veins and the left atrium were encircled. The ablation probe was then advanced to encircle the left atrium under the guide of the introducers. The probe is suction-assisted to ensure uniform contact with the myocardium and homogeneous energy delivery. After tightening the probe loop, a circular “box” lesion was done. The energy can be automatically titrated by the generator to achieve a stable 80°C tissue temperature. At the end of the procedure the probe was withdrawn and the operative field was inspected (Fig 1). The equipment used herein is designed uniquely for the minimally invasive access. It differs from the corresponding devices to be used by median sternotomy in the following points: long stylet, introducer, and energy delivery system to reach the intrapericardial structures through a mini-thoracotomy; magnetic connection system, and curved, malleable introducers to work in the limited space available. At the boy's 6-month follow-up, he was in stable sinus rhythm (by internal loop recorder tracings) and in drug wash-out, except for acetylsalicylic acid (75 mg/daily); amiodarone and warfarin were withdrawn at the end of postoperative month 3. The patient is asymptomatic and has resumed his activities. No heart block developed, and the mini-thoracotomy scar was almost not visible. There has been no evidence of stenosis of the pulmonary veins. Drug-refractory lone AF represents a common clinical problem. Currently, stand-alone surgery of AF is proposed to patients with contraindication or previous failure of catheter ablation, or to patients who prefer the surgical approach [1Heart Rhythm Society (HRS) Task Force on cathetersurgical ablation of atrial fibrillationExpert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendation for personnel, policy, procedure and follow-up.Europace. 2007; 9: 335-379Crossref PubMed Scopus (557) Google Scholar]. However, such recommendation is based on data obtained with conventional arrhythmia surgery through a sternotomy route. The surgical indication to treat for lone AF may become more liberal if the minimally invasive approaches are proved feasible, effective, and well-tolerated. We believe we have described a successful minimally invasive ablation of lone AF was conducted in a child. Atrial fibrillation in children is most frequently associated with structural heart disease. Thus, arrhythmia surgery in these patients is usually performed during correction of congenital heart disease. The transcatheter radiofrequency (RF) ablation is usually regarded as an extreme option for lone AF in these individuals [2Lee P. Hwang B. Chen S. et al.The results of radiofrequency catheter ablation of supraventricular tachycardia in children.PACE. 2007; 30: 655-661Crossref Scopus (47) Google Scholar]. Our patient had indication to RF ablation on the basis of drug refractory, ongoing symptoms, and the risk of developing secondary cardiomyopathy in time. However, the rates of procedural success and arrhythmia recurrence after transcatheter ablation in the pediatric population are less than optimal [2Lee P. Hwang B. Chen S. et al.The results of radiofrequency catheter ablation of supraventricular tachycardia in children.PACE. 2007; 30: 655-661Crossref Scopus (47) Google Scholar]. Epicardial ablation may be deemed superior when compared to transcatheter ablation, if it entails a minimal incision without the need for cardiopulmonary bypass; in some cases, this technique allows extubation of the patient in the operating room. A reliable achievement of transmurality and the linear continuity of the lesion represent the key technical advantage of the epicardial RF ablation versus the catheter approach, particularly when suction-assisted equipment is being used on the beating heart. However, we routinely confirm the electrical isolation of the pulmonary cuffs in minimally invasive AF ablation surgery. This is done by pacing the left atrial dome and measurement of conductance. A left atrial procedure rather than a bi-atrial ablation is performed with this minimally invasive approach, which represents a theoretical disadvantage. Larger ablation sets are possible, but they require a bilateral mini-thoracotomy and this is a more complex procedure. The electrical isolation is limited to the pulmonary veins, and this may negatively impact the rate of freedom from arrhythmia at the patient's follow-up. Thus, we should clarify which patient subgroups will benefit from pulmonary veins isolation alone, and which will require a larger lesions set to achieve a favorable outcome. The patients having originating pulmonary veins foci as the predominant pro-arrhythmic mechanism will theoretically obtain the maximal benefit from pulmonary veins isolation. These probably represent the majority of cases of adults with lone paroxysmal AF [3Benussi S. Nascimbene S. Agricola E. et al.Surgical ablation of atrial fibrillation using the epicardial radiofrequency approach: mid-term results and risk analysis.Ann Thorac Surg. 2002; 74: 1050-1056Abstract Full Text Full Text PDF PubMed Scopus (83) Google Scholar], although more complex mechanisms often subtend the arrhythmia. In the pediatric patients, AF is most frequently triggered by pulmonary vein foci, as well [4Nanthakumar K. Lau Y. Plumb V. Epstein A. Kay G.N. Electrophysiological findings in adolescents with atrial fibrillation who have structurally normal hearts.Circulation. 2004; 110: 117-123Crossref PubMed Scopus (52) Google Scholar]. The ablation technology used herein achieves interruption of both pulmonary veins foci and macro re-entrant circuits around the pulmonary veins (Fig 1). In patients with originating pulmonary veins foci, the stand-alone epicardial ablation may be reasonable, even as the primary nonpharmacological therapeutic option (Fig 2) in view of expected high success rates. The results of the electrophysiological study represented an adjuvant in our decision making. The minimally invasive procedures are associated with an increased level of technical complexity. This case of epicardial ablation in a child confirms the versatility of the present technique, which can be tailored even to the challenging anatomy of the pediatric patients. In the published experiences of transcatheter RF ablation, it has been suggested that a less extensive ablation around the pulmonary veins in children and adolescents may decrease the risk of late complications (i.e., pulmonary veins stenosis) [2Lee P. Hwang B. Chen S. et al.The results of radiofrequency catheter ablation of supraventricular tachycardia in children.PACE. 2007; 30: 655-661Crossref Scopus (47) Google Scholar]. In our experience of RF ablation of lone AF in adults, a mid-term follow-up in 47 patients disclosed no cases of pulmonary vein stenosis [5Speziale G. Bonifazi R. Nasso G. et al.Minimally invasive ablation of lone atrial fibrillation by monolateral right minithoracotomy Operative and early follow-up results.Ann Thorac Surg. 2010; (in press)Google Scholar]. However, echocardiographic surveillance is recommended in these adult patients and will be mandatory in the pediatric cases. Some groups are developing hybrid “staged” epicardial and endocardial treatment strategies. In these instances, the minimally invasive isolation of the pulmonary veins is completed by additional ablation lines performed through the transcatheter approach [6Choi J.I. Pak H.N. Kim Y.H. Hybrid epicardial and endocardial catheter ablation in a patient with atrial fibrillation and suspicious left atrial thrombus.Circ J. 2009; 73: 384-387Crossref PubMed Scopus (4) Google Scholar]. The major research goal in the future will concern the prompt differentiation among patients requiring different treatment strategies. However, the minimally invasive technique may revolutionize the role of stand-alone epicardial ablation. Electrophysiological study provides useful information for the generation of arrhythmia and may be considered to evaluate the surgical indication.