A case of successful catheter ablation for biatrial reentrant tachycardia after a Mustard operation for dextro-transposition of the great arteries

Mustard and Senning operations are atrial switch techniques for dextro-transposition of the great arteries (d-TGA) which have been mainly performed during a period from the 1960s to the mid-1980s. In the Mustard procedure, an artificial patch forming a baffle was used for the purpose to divide the original atria into the following two chambers; a systemic venous atrium (SVA), which directs venous blood from the superior vena cava (SVC) and inferior vena cava (IVC) to the mitral annulus and left ventricle, and a pulmonary venous atrium (PVA), which directs pulmonary blood to the tricuspid annulus and right ventricle.1Mustard W.T. Keith J.D. Trusler G.A. Fowler R. Kidd L. The surgical management of transposition of the great vessels.J Thorac Cardiovasc Surg. 1964; 48: 953-958Abstract Full Text PDF PubMed Google Scholar Despite survival improvement in these populations, complications such as right ventricular failure, arrhythmias, tricuspid valve dysfunction, baffle-related problems over a long period are known.2Moons P. Gewillig M. Sluysmans T. et al.Long term outcome up to 30 years after the Mustard or Senning operation: a nationwide multicentre study in Belgium.Heart. 2004; 90: 307-313Crossref PubMed Scopus (186) Google Scholar Particular an incidence of supraventricular tachycardia (SVT) after the Mustard operation was reported as high as 48% due to the extensive incisions and suture lines in the atria that resulted in intra-atrial conduction delays.3Szili-Torok T. Kornyei L. Jordaens L.J. Transcatheter ablation of arrhythmias associated with congenital heart disease.J Interv Card Electrophysiol. 2008; 22: 161-166Crossref PubMed Scopus (26) Google Scholar Biatrial tachycardia (BiAT) is a rare form of macroreentrant atrial tachycardia that includes two independent interatrial connections and both atria within its circuit, and is often observed in patients with a history of catheter ablation for atrial fibrillation or open heart surgery.4Kitamura T. Martin R. Denis A. Takigawa M. Duparc A. Rollin A. Characteristics of Single-Loop Macroreentrant Biatrial Tachycardia Diagnosed by Ultrahigh-Resolution Mapping System.Circ Arrhythm Electrophysiol. 2018; 11e005558Crossref Scopus (44) Google Scholar Regarding congenital heart disease (CHD) patients, BiAT was reported to occur in approximately 4%, and a few cases after Senning operation were reported but not in cases after Mustard operation.5Moore J.P. Bowman H. Gallotti R.G. Shannon K.M. Mechanisms and outcomes of catheter ablation for biatrial tachycardia in adults with congenital heart disease.Heart Rhythm. 2021; 18: 1833-1841Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar We herein present a case of BiAT utilizing upper and lower interatrial connections around the artificial patch after a Mustard operation. A 41-year-old man who was diagnosed with d-TGA complicated with ventricular septal defect (VSD) underwent an atrial switch procedure by a Mustard operation combined with a patch closure for VSD at the age of three months. He also has a history of pulmonary venous pathway stenosis and bi-femoral vein occlusion, which were identified in his teenage years. He underwent percutaneous transcatheter balloon angioplasty for pulmonary venous pathway stenosis at the age of 40.6Nitta M. Sugano T. Iwata K. Real-time three-dimensional trans-oesophageal echocardiography-guided balloon dilation of pulmonary venous pathway obstruction in a patient with dextro-transposition of the great arteries after atrial switch surgery: a case report.Cardiol Young. 2019; 29: 983-985Crossref PubMed Scopus (0) Google Scholar He developed repetitive palpitation and a 12-lead electrocardiogram showed narrow QRS tachycardia, which suggested atrial tachycardia (AT). The echocardiogram demonstrated a mid-range right ventricular dysfunction with an ejection function of 40% that was responsible for systemic circulation, and a preserved left ventricular function with an ejection function of 53% that was responsible for pulmonary circulation. Because AT was symptomatic and intolerant to antiarrhythmic drugs, catheter ablation was performed under general anesthesia after obtaining written informed consent. A decapolar catheter was placed in the left atrial appendage via the left subclavian vein as a reference catheter, which revealed two-to-one atrioventricular conduction AT with a cycle length of 290ms. Due to the obstruction of both femoral veins, the right jugular vein was selected as venous access to the SVA. An activation map of SVA performed by using a multipolar catheter and three-dimensional mapping system (Pentaray®TM, CARTO3®TM, Biosense Webster, Inc., CA, USA) showed a focal pattern with the earliest activation site of the lower septum, which filled 79% of tachycardia cycle length (TCL) (Figure 1A). Subsequently, the PVA activation map was performed using an irrigated tip ablation catheter (Thermocool Smarttouch®TM, Biosense Webster, Inc., CA, USA) via a retrograde transaortic approach. The map showed a focal pattern with the earliest activation site of the ostium of the right superior pulmonary vein (RSPV), which filled 84% of TCL (Figure 1B, C). The earliest site of PVA structurally faced the superior vena cava (SVC) on the SVA side. The map of left pulmonary vein (LPV) side, which is farther beyond the pulmonary venous pathway stenosis, was omitted because the local activation time on the LPV side during AT was well delayed enough to show a focal pattern of PVA with RSPV ostium as the earliest site. Referring to voltage maps, a wide low voltage area was found in the septum of both atria suggesting an artificial patch. Entrainment pacing studies showed that the site of “post pacing interval (PPI) - TCL interval < 30ms” was confirmed at the earliest site of SVA, the posterior SVC that was adjacent to the earliest site of PVA, the septum of PVA that faced the earliest site of SVA, and the posterolateral site of PVA (Figure 1). The “PPI-TCL < 30ms” sites were located in discrete points in both atria. The biatrial activation map covered the entire TCL. The wavefront commences from the anterior ostium of RSPV, descends through the posterolateral wall to the lower septum of the PVA, then enters the lower septum of the SVA, after which it ascends the SVA to the posterior SVC, and returns to the ostium of RSPV (Figure 2). The earliest activation site of each atrium faced the contralateral atrium chamber. Combined with the entrainment pacing findings, the AT was diagnosed as BiAT. Notably, continuous fractionated potentials bridging double potential were recorded at the earliest site of each atrium (Figure 2 a, f) suggesting slow conduction pathways adjacent to the patch edge. The circuit consisted of the upper and lower interatrial conduction around the patch and both atria. Radiofrequency (RF) applications to the earliest site of PVA resulted in TCL prolongation by 30ms without atrial sequence change. The subsequent application to the earliest site of SVA prolonged TCL by 60ms with a local potential delay by 100ms without obvious atrial sequence change though insertable electrode catheters were limited. The PVA septum facing the earliest site of SVA was a wavefront entrance from PVA to SVA and was the subsequent target. While Pentaray catheter was positioned at the lower septum of SVA as an anatomical marker, RF applications to the target where the local potential preceded the lower septal SVA via a retrograde transaortic approach successfully terminated BiAT. Additional applications in this area were attempted but could not create the lower interatrial conduction block. Based on the SVA activation map during right atrial appendage pace on PVA, both upper and lower interatrial conductions remained, however, non-inducibility of any ATs was achieved. The patient was free from any arrhythmia for more than two years without any antiarrhythmic drugs. SVT is commonly related to increased mortality and morbidity in patients with CHD.7Karbassi A. Nair K. Harris L. Wald R.M. Roche S.L. Atrial tachyarrhythmia in adult congenital heart disease.World J Cardiol. 2017; 9: 496-507Crossref PubMed Google Scholar SVT and impaired ventricular function are associated with risk factors of sudden cardiac death that have been reported at 2%-9% per decade.8Lundqvist C.B. Potpara T.S. Malmborg H. Supraventricular arrhythmias in patients with adult congenital heart disease.Arrhythm Electrophysiol Rev. 2017; 6: 42-49Crossref PubMed Scopus (7) Google Scholar Therefore, rhythm control is an important treatment in this population. It was previously reported that in patients after atrial redirection procedure for TGA, the most common mechanism of SVT was cavotricuspid isthmus (CTI) dependent intra-atrial reentrant tachycardia (IART), followed by incisional or scar-related IART, and focal AT.9Gallotti R.G. Madnawat H. Shannon K.M. Aboulhosn J.A. Nik-Ahd F. Moore J.P. Mechanisms and predictors of recurrent tachycardia after catheter ablation for d-transposition of the great arteries after the Mustard or Senning operation.Heart Rhythm. 2017; 14: 350-356Abstract Full Text Full Text PDF PubMed Scopus (15) Google Scholar In 12 cases of IART after Mustard operation, CTI was also reported to be the most frequent central barrier of IART, but there was no case of BiAT.10Zrenner B. Dong J. Schreieck J. et al.Delineation of intra-atrial reentrant tachycardia circuits after mustard operation for transposition of the great arteries using biatrial electroanatomic mapping and entrainment mapping.J Cardiovasc Electrophysiol. 2003; 14: 1302-1310Crossref PubMed Scopus (59) Google Scholar Kitamura et al. categorized BiAT into three types of reentrant circuits in cases with post-RF catheter ablation for atrial fibrillation (n=7) and open heart surgery for an atrial septal defect (n=1). Type 1 includes two separate interatrial connections and both atria, while Types 2 and 3 include two separate interatrial connections and the right atrial septum.4Kitamura T. Martin R. Denis A. Takigawa M. Duparc A. Rollin A. Characteristics of Single-Loop Macroreentrant Biatrial Tachycardia Diagnosed by Ultrahigh-Resolution Mapping System.Circ Arrhythm Electrophysiol. 2018; 11e005558Crossref Scopus (44) Google Scholar In the present case, types 2 and 3 were excluded because the atrial septum was an artificial patch. For BiAT series in patients with CHD, Moore et al. reported 3 cases of BiAT after Senning operation.5Moore J.P. Bowman H. Gallotti R.G. Shannon K.M. Mechanisms and outcomes of catheter ablation for biatrial tachycardia in adults with congenital heart disease.Heart Rhythm. 2021; 18: 1833-1841Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar In the Senning procedure, self-atrial muscles are used to reconstruct SVA and PVA instead of using an artificial patch. Thereby the biological septa and complex suture lines may form substrates for diverse reentrant circuits, leading several previously reported cases of BiAT. To our knowledge, this is the first case report of BiAT after Mustard operation. Each atrial activation map demonstrated a focal pattern, and the biatrial activation map covered the entire TCL. By entrainment pacing, sites of PPI-TCL less than 30ms were widely dispersed in both atria, including the earliest activation area of SVA and PVA. To diagnose the circuit as BiAT, entrainment pacing studies in both atria and biatrial activation map using a three-dimensional mapping system were needed. In this case, the local potential on the earliest site of each atrium showed continuous fractionated potentials bridging double potential. This electrical feature suggests a conduction delay on the suture line. There should be varying degrees of residual interatrial conduction between the two atria on the patch suture line, including conduction block, conduction delay, and conduction gaps. Based on the voltage map and local potentials, the patch area was estimated as shown in figure 3. The circuit consisted of the upper interatrial connection that formed an entrance of excitation propagation from SVA to PVA (Figure 3A, B), the lower connection that formed an entrance from PVA to SVA (Figure 3C), and both atria. RF applications to the earliest site of each atrium prolonged TCL. Especially, the ablation to the earliest site of SVA resulted in remarkable TCL prolongation and local excitation delay, which suggested that the lower interatrial connection was modified and changed to an alternative pathway in the entry site. The success site on PVA was the contralateral site of the earliest site of SVA, but it was located anterior to the original SVA earliest site two-centimeter apart. Because there could be multiple or wide interatrial connections around the patch, the entrance could have changed from the lower edge of the patch to the anterior one after RF applications to the inferior connection (Figure 3D). Among the previously reported SVT cases after Mustard and Senning operations which were diagnosed as focal AT, there might have been underrecognized cases of BiAT because the activation pattern of one-sided atrium presents a focal pattern. Even in such cases, it would be possible to treat by ablation to the earliest site of the atrium if the critical conduction could be eliminated without elucidating its entire circuit. However, careful electrophysiological mapping with recent advanced mapping systems may improve the identification of these complex circuits. Considering the moderate recurrence rate of 10%-32% in these populations,3Szili-Torok T. Kornyei L. Jordaens L.J. Transcatheter ablation of arrhythmias associated with congenital heart disease.J Interv Card Electrophysiol. 2008; 22: 161-166Crossref PubMed Scopus (26) Google Scholar,9Gallotti R.G. Madnawat H. Shannon K.M. Aboulhosn J.A. Nik-Ahd F. Moore J.P. Mechanisms and predictors of recurrent tachycardia after catheter ablation for d-transposition of the great arteries after the Mustard or Senning operation.Heart Rhythm. 2017; 14: 350-356Abstract Full Text Full Text PDF PubMed Scopus (15) Google Scholar,10Zrenner B. Dong J. Schreieck J. et al.Delineation of intra-atrial reentrant tachycardia circuits after mustard operation for transposition of the great arteries using biatrial electroanatomic mapping and entrainment mapping.J Cardiovasc Electrophysiol. 2003; 14: 1302-1310Crossref PubMed Scopus (59) Google Scholar the present case has had a successful course. This probably supports that the critical conduction on the reentrant circuit was eliminated despite remaining interatrial connections. We describe a rare case of BiAT involving upper and lower interatrial conductions around the artificial patch after Mustard operation. To diagnose, the entrainment pacing in both atria and biatrial activation maps were required. For effective ablation, biatrial approaches were also required.