In this article, the authors provide an overview of their use of a microaxial flow pump in a patient with transposition of the great arteries (TGA). This device allowed hemodynamic stability during mapping and ablation of the atrial reentrant tachycardia. Introduction Transcatheter ablation of atrial flutter and ventricular tachycardia in patients with structural heart disease has proven effective in eliminating recurrent symptoms and frequent ICD discharges.1-3 However, hemodynamic instability may develop during arrhythmia mapping, particularly in patients with significant ventricular dysfunction.3 Several approaches have been utilized to achieve hemodynamic stability during ablation of unstable ventricular and atrial arrhythmias including the use of antiarrhythmic agents to slow the arrhythmia, single beat noncontact mapping, and substrate-based mapping approaches that do not require arrhythmia initiation.4,5 Hemodynamic stability may also be achieved during ablation of atrial arrhythmias by creating second degree atrioventricular block through pharmacologic manipulation. While substrate-based mapping and ablation can be successful, complete mapping of the clinical arrhythmia circuit, termination during ablation and noninducibility following ablation appear to be better predictors of long-term efficacy.5,6 Considerable progress has been made in the development of devices that provide hemodynamic support during cardiac interventions. Cardiopulmonary support using extracorporeal membrane oxygenation and percutaneous left ventricular assist devices have provided hemodynamic stability during cardiac catheterizations and arrhythmia ablations in pediatric and adult patients.7,8 The Impella device (Abiomed, Danvers, MA) is a microaxial flow pump that was developed as a percutaneous left ventricular assist device. The Impella LP 2.5 device is a catheter-based, miniaturized rotary blood pump that is inserted in the femoral artery and placed via a retrograde approach through the aortic valve into the left ventricle (Figure 1). The microaxial pump continuously aspirates blood from the left ventricle and pumps it into the ascending aorta with a maximal flow of 2.5 l/min.9 It has been used for hemodynamic support during high risk coronary interventions, as a bridge to recovery during fulminant acute myocarditis, and as treatment of cardiogenic shock caused by myocardial infarction.9-11 A modified version of the microaxial blood pump has been developed as a right ventricular assist device; however, this is not placed percutaneously, requiring direct cannulation of the right atrium and pulmonary artery.12 The Impella device can be placed percutaneously into the left ventricle during ventricular tachycardia ablation or into the systemic right ventricle during ablation of atrial flutter in adults with transposition of the great arteries (TGA) that are status post a Mustard or Senning operation.13 Case Presentation The patient is a 35-year-old with TGA who underwent a Mustard operation at 2 weeks of age (Figure 2). He has recurrent atrial flutter and sinus node dysfunction that has been treated with atrial pacing, a number of class 1 and class 3 antiarrhythmic medications, and an attempted catheter ablation in 2005 that was aborted because of bilateral femoral vein occlusion. Despite escalating doses of sotalol, he had recurrent episodes of atrial flutter and was referred for another attempt at catheter ablation in 2009. An echocardiogram prior to the procedure demonstrated moderate right (systemic) ventricular dysfunction. The procedure was performed under general endotracheal anesthesia. Venous access to the heart was achieved with a transhepatic approach. Mapping of an induced atrial flutter at a cycle length of 420 msec with 1:1 atrioventricular conduction was attempted utilizing the EnSite NavX system (St. Jude Medical, St. Paul, MN) to create a three-dimensional electroanatomic map of the tachycardia circuit. Despite the relatively slow rate of atrial tachycardia, the patient was markedly hypotensive and within 2 minutes developed rapid, polymorphic ventricular tachycardia. He required defibrillation, an epinephrine bolus, and chest compressions on 2 occasions because of recurrent atrial flutter and severe hypotension. Due to the inability to map the arrhythmia circuit, empiric lesions were placed on either side of the atrial baffle in the presumed cavotricuspid isthmus with an internally irrigated radiofrequency ablation catheter (Chilli catheter, Boston Scientific, San Jose, CA). Post ablation testing was not attempted because of prior hypotension and ventricular arrhythmias. The following day, because of hemodynamic instability and ventricular arrhythmias associated with recurrent atrial tachycardia, his pacemaker was upgraded to a dual chamber implantable defibrillator (Current DR, St. Jude Medical). The patient was treated with amiodarone, but continued to have frequent breakthrough episodes of atrial flutter. One month later, the patient was referred for another attempt at catheter ablation. Informed consent for use of the Impella device was obtained. The procedure was performed under general endotracheal anesthesia and venous access obtained via a transhepatic approach and cannulation of the right internal jugular vein. The right femoral artery was percutaneously accessed. A Perclose system (Abbott Laboratories, Abbott Park, IL) was used to place sutures around the right femoral percutaneous arteriotomy site though not tied (“preclose” technique). Angiography of the distal descending aorta and iliac arteries was performed through an 8 French (Fr) sheath to document adequate diameter for placement of the Impella LP 2.5 system. A 14 Fr sheath was placed in the right femoral artery, and the Impella pump was advanced over a 0.14” guidewire across the aortic valve into the right ventricle under fluoroscopic guidance (Figure 3). The initial flow rate was 1.25 l/min and adjusted as needed to maintain hemodynamic stability. An 8 Fr Cool Path external irrigation catheter (St. Jude Medical) was used for mapping and ablation of the tachycardia circuit. The EnSite NavX three-dimensional electroanatomic system was utilized for point-to-point circuit mapping. Atrial flutter, at a cycle length of 400 msec, was reproducibly inducible with burst atrial pacing and catheter manipulation. The patient was hemodynamically stable, maintaining a systolic blood pressure of greater than 100 mmHg and did not develop ventricular arrhythmias. Mapping of the systemic venous atrium identified the inferior region of the atria by the cavotricuspid isthmus to be a critical part of the atrial reentry circuit. The pulmonary venous atrium was accessed via a transseptal/transbaffle approach with an 8 Fr Mullins sheath and Brockenbrough needle utilizing the previously established transhepatic route. The ablation catheter was positioned in a corresponding region of the cavotricuspid isthmus on the pulmonary venous side of the baffle. Radiofrequency lesions with a preset power output of 35 watts and a maximum temperature of 40 ºC were administered during atrial flutter. Multiple lesions were placed from the atrial baffle to the tricuspid annulus. The tachycardia terminated during this lesion set, but was reinducible with a slightly longer cycle length of 420 msec. The ablation catheter was removed from the transseptal sheath and placed through the internal jugular sheath into the systemic venous atrium. The inferior region of the atrium, directly across from the lesions placed on the pulmonary venous side, was targeted. Application of radiofrequency energy resulted in termination of atrial flutter that was no longer inducible with extrastimulus and burst pacing protocols. The Impella system and 14 Fr sheath were removed and the previously placed right femoral arteriotomy sutures tied achieving hemostasis. The transhepatic sheath was removed and the tract was coil occluded to ensure hemostasis. The patient was monitored overnight, his amiodarone discontinued, and discharged home the following day. He has had no recurrence of atrial flutter at 15-month follow-up. Discussion The novel use of the Impella microaxial flow pump in an adult with TGA who had a Mustard operation provided hemodynamic stability during mapping and ablation of atrial reentrant tachycardia. The Impella device was placed successfully in the systemic right ventricle via a retrograde aortic approach without difficulty. It resulted in a stable blood pressure and cardiac output, allowing extensive mapping during prolonged periods of atrial flutter without developing, and perhaps preventing, the hemodynamic embarrassment suffered by this patient during a previous ablation attempt. Mapping of cardiac arrhythmias during catheter ablation may result in hemodynamic compromise, particularly in patients with significant ventricular dysfunction. Alternative methods of maintaining hemodynamic stability during transcatheter ablation of significant cardiac arrhythmias are available but were not considered appropriate in this clinical situation. Hemodynamic stability may be achieved during ablation of atrial arrhythmias by creating second degree atrioventricular block through pharmacologic manipulation. Single beat mapping using the EnSite non-contact Array catheter (St. Jude Medical) has been successful in mapping hemodynamically unstable arrhythmias, though the limited access available in this patient precluded this method.4 The percutaneous use of the Impella device has been demonstrated to provide valuable left ventricular support during high risk catheter-based interventions and in patients with severe ventricular dysfunction resulting from fulminant myocarditis or cardiogenic shock.9-11 A recent report described the use of the Impella microaxial blood pump for ablation of hemodynamically unstable ventricular tachycardia in three patients.14 The use of another type of percutaneously placed left ventricular assist device has been reported during mapping and ablation of a hemodynamically unstable ventricular tachycardia.8 Utilizing the Impella pump, hemodynamic support can provide stability during mapping and ablation of atrial tachycardia in a previously unstable patient with a poorly functioning, systemic, right ventricle.13 It should be noted that percutaneous placement of the Impella device across the aortic valve into the right ventricle eliminates retrograde access to the pulmonary venous atrium and tricuspid annulus in patients who have had a Mustard or Senning operation. However, as with our case, a “transseptal” approach through a surgically created baffle has been successful in mapping and ablation of atrial tachycardia and reportedly provides easier access to critical regions of the pulmonary venous atrium.15 Summary The use of the percutaneous Impella microaxial flow pump can be considered during catheter ablation in congenital heart patients with dysfunctional systemic right ventricles when hemodynamic compromise accompanies the arrhythmia. It may also be used for ventricular support during catheter ablation of hemodynamically unstable ventricular tachycardia. The use of this system provides the opportunity to obtain an accurate map of the patient’s reentrant arrhythmia circuit and allows for post-ablation testing to confirm efficacy.