Ablation of Atypical Atrial Flutter Via Azygous Vein with Remote Magnetic Navigation in Congenital Heart Disease

Congenital heart disease (CHD) has an incidence of nearly 1% of births per year, according to the Centers for Disease Control.^1,2 Due to advances in interventional cardiology and cardiac surgery, there is a growing adult population with congenital heart disease. Additionally, the prevalence of arrhythmias in these patients with congenital heart disease necessitates procedural innovation in cardiac electrophysiology. In patients with surgically corrected congenital disorders such as transposition of the great arteries, total anomalous pulmonary venous connection (TAPVC), and atrial septal defects (ASD), extensive corrective procedures often yield proarrhythmic suture lines and myocardial scarring. Similarly, patients with Fontan and Mustard/Senning procedures can have a high incidence of atrial arrhythmias.^3-6 Despite increasing experience with standard catheter ablation in this patient population, there often exists procedural limitations due to challenging discontinuities in anatomy that require circuitous and complex catheter routes to target the areas of interest. Thus, utilization of a remote magnetic navigation system may afford greater mapping and ablation abilities over traditional manual catheter-based approaches. In this brief case report, we present a challenging case of atrial flutter that was successfully mapped and ablated using the Niobe^® Magnetic Navigation System (Stereotaxis).   

Case Description

The patient is a 51-year-old male with a history of congenital heart disease who presented for newly diagnosed atrial flutter and concern for tachycardia-induced cardiomyopathy. As a child, he was diagnosed with TAPVC, primum ASD, cleft mitral valve, and an under-developed inferior vena cava (IVC) with a large azygous venous system. He previously had undergone a surgical ASD closure and baffle repair of his TAPVC. More recently, he was diagnosed with a nonischemic cardiomyopathy associated with incessant atrial flutter, and continued to have exertional symptoms despite aggressive medical therapy. He was subsequently referred to electrophysiology for a possible curative procedure. His 12-lead ECG revealed an atypical atrial flutter with 2:1 conduction (Figure 1). Given his ongoing symptoms and worsening systolic dysfunction, the decision was made to proceed with electrophysiology study and ablation.

Preprocedural cardiac magnetic resonance imaging revealed a reduced left ventricular function of 36%, without evidence of significant late gadolinium enhancement. There appeared to be two residual defects within the prior ASD repair, with dilated right atrium (RA) and left atrium (LA). Three of the pulmonary veins appeared to drain normally into the LA; however, the right superior pulmonary vein was routed into a confluence entering the LA, presumed to be a baffle. The superior vena cava (SVC) drained normally into the RA, yet the infrahepatic segment of the IVC was completely absent. There was a significantly dilated azygous vein that drained into the SVC, and coronary sinus that drained directly into the LA. (Figure 2) 

The procedure was performed under general anesthesia and after a transesophageal echocardiogram revealed no left atrial or atrial appendage thrombus. Due to his anatomic variants, access was obtained at the right internal jugular (IJ), left subclavian, right femoral vein, and left femoral artery. Ablation in patients with interrupted IVC anatomy has previously been reported, and a similar superior approach is commonly instituted in this clinical scenario.⁷ An SL1 long sheath was advanced from the femoral vein through the azygous vein to just below its communication with the SVC. A HALO duodecapolar catheter (Biosense Webster, Inc., a Johnson & Johnson company) was placed via the right IJ vein for mapping along the tricuspid valve, and a quadripolar catheter was used as a roving catheter. Utilizing the Niobe system (Stereotaxis), the ablation catheter was inserted into the long sheath and advanced via the azygous vein to the SVC and down into the RA. The course of the azygous into the SVC had a 180-degree hairpin turn.

The presenting rhythm was atrial flutter with an atrial cycle length of 286 msec. Three-dimensional electroanatomic activation mapping (CARTO, Biosense Webster, Inc., a Johnson & Johnson company) of the RA demonstrated broad early activation along the posterior atrial septum. Entrainment maneuvers demonstrated that the lateral tricuspid valve annulus was distant from the flutter circuit, while the septal annulus, SVC, and posterior RA were within the circuit (Figure 4). A linear lesion set was applied from the SVC to the IVC with creation of a bicaval line that resulted in termination of the tachycardia (Figure 5A). Rapid atrial pacing induced a second tachycardia with an atrial cycle length of 228 msec, and repeat activation mapping suggested a focal tachycardia. 

With the earliest RA activation occurring at the septum, the decision was made to access the LA via a retrograde aortic approach to allow adequate mapping of the septum. An 8.5 French SR0 long sheath was advanced via the left femoral artery into the descending aorta. The Stereotaxis catheter was steered retrograde through the aorta, to the left ventricle and across the mitral valve for LA mapping. Such a complex route would theoretically be possible, but exceedingly difficult, by a standard manual approach. LA mapping demonstrated fractionated electrograms at the superior left septum. Ablation lesions were initiated at the superior septum, and as the ablator was advanced across the ASD from the LA to RA, there was termination of the tachycardia. (Figure 5B)

At six-month follow-up, the patient had improvement of his functional status without recurrence of atrial arrhythmias. Repeat echocardiogram imaging had revealed near normalization of his LV function (EF 50%), confirming the initial suspicion of tachycardia-induced cardiomyopathy.

Discussion

As a tertiary referral center for complex ablation, our experience with congenital heart patients highlights the value of a magnetic navigation system for mapping and ablation. Given the access challenges and tortuous anatomy in this patient, magnetic navigation proved to be an effective and essential modality. Prior reports have shown the feasibility of magnetic navigation in unique clinical scenarios, such as utilizing a retrograde aortic approach for pulmonary vein ablation.^8,9 Thus, magnetic navigation remains yet another tool in the electrophysiologist’s armamentarium when confronted with challenging cases such as in patients with surgically corrected congenital heart disease.

Disclosures: The authors have no conflicts of interest to report.

References

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