Ablation for unmappable ventricular tachycardia in a patient with complete transposition of the great arteries who underwent Rastelli repair

Abstract

Catheter ablation (CA) of ventricular tachycardia (VT) after repair of congenital heart disease may be difficult because of complex anatomy and sometimes unmappable VT. Here, we report a 41-year-old woman with successful CA of unmappable VT in a patient with complete transposition of the great arteries after Rastelli repair. Clinical VT was induced by programmed electrical stimulation, when the mapping catheter was placed at the high anterior right ventricular outflow tract (RVOT). During VT, the local potential at the high anterior RVOT under the right ventricle (RV) – pulmonary artery (PA) conduit was equal to that at the timing of onset of QRS. The VT was unmappable because the hemodynamics deteriorated. Pace mapping was also tried at the aortic cusp and the left ventricular outflow tract (LVOT). Fractionated potential during sinus rhythm was observed at the noncoronary cusp, and the paced QRS morphology at this site was similar to that of the clinical VT, with a delay of 55 ms from pacing to the onset of QRS. However, mapping at the LVOT was impossible due to the difficulty of catheter manipulation. Radiofrequency energy was successfully applied at the noncoronary cusp and the high anterior RVOT under the RV-PA conduit.

<Learning objective: This report is a rare case of successful catheter ablation of unmappable ventricular tachycardia (VT) in a patient with complete transposition of the great arteries after Rastelli repair. The VT was unmappable because of intolerable hemodynamics. However, we could speculate the exit or isthmus of the VT by pace mapping or local potential and eliminate the VT.>

Introduction

A significant proportion of congenital heart disease (CHD) patients suffer from various arrhythmias, including atrial tachycardias, ventricular tachycardias (VT), and ventricular fibrillation due to the underlying CHD or as a sequela of interventional or surgical treatment [1,2]. Catheter ablation (CA) of VT after repair of CHD may be difficult because of complex anatomy and sometimes unmappable VT. Insights into the relationship between anatomical obstacles identified through substrate mapping techniques and critical re-entry circuit isthmuses might facilitate ablation [3]. Although CA for VT in patients with tetralogy of Fallot has been often reported [3], [4], [5], reports of VT in patients with complete transposition of the great arteries (TGA) who underwent Rastelli repair are rare [6].

Here, we report the case of successful CA of unmappable VT in a patient with complete TGA after Rastelli repair.

Case report

A 41-year-old woman was diagnosed with complete TGA. She underwent a Rastelli-type repair when she was 1-year-old. At the age of 7 years, she underwent a repair of the right ventricular outflow tract (RVOT). Eleven years after the RVOT operation, she underwent RVOT repair, including tricuspid valvuloplasty and closure of the ventricular septal defect (VSD). Cavo-tricuspid isthmus ablation for common atrial flutter was performed when she was 38 years old, followed by pacemaker implantation for sick sinus syndrome at 39 years of age. One year after pacemaker implantation, she visited a hospital owing to palpitations and dizziness. A 12-lead electrocardiogram detected wide QRS tachycardia, which indicated a left bundle branch block with inferior axis morphology (Fig. 1B). The wide QRS tachycardia was terminated with cardioversion. She was prescribed amiodarone and was referred to our hospital for definitive treatment. Transthoracic echocardiography showed that left ventricular contraction was preserved with an end-diastolic volume of 79 ml, end-systolic volume of 29 ml, and ejection fraction of 63%. Transthoracic echocardiography also showed a dilated right atrium and right ventricle (RV), residual muscular type VSD showing a left-to-right shunt, and a RV-pulmonary artery (RV-PA) conduit with severe regurgitation and no stenosis. Cardiac magnetic resonance imaging showed a conduit connecting the RV and PA and no late gadolinium enhancement.

Fig. 1.

(A) Electrocardiogram (ECG) during sinus rhythm (A) shows the complete right bundle branch block. (B) ECG during ventricular tachycardia shows the left bundle branch block, inferior axis.

An electrophysiological study was performed under minimal sedation. The VT was presumed to originate from the RVOT under the RV-PA conduit or the low-voltage area. During the electrophysiology study, a decapolar catheter was inserted into the coronary sinus from the right jugular vein, and a quadrupolar catheter was placed in the His-bundle region from the right femoral vein. Electroanatomical mapping was performed using CARTO-3 (Biosense Webster, Diamond Bar, CA, USA) and decapolar catheter guidance from the right femoral vein. Apparent low-voltage areas and fractionated potentials were not obtained from the RV except under the RV-PA conduit. A pace mapping was undertaken around the RV-PA conduit, VSD patch, tricuspid annulus, and RVOT. The paced QRS morphology at high anterior RVOT under the RV-PA conduit was almost the same as that of clinical VT without latency from the pacing spike to the onset of QRS (Fig. 2B). Clinical VT [tachycardia cycle length (TCL) = 276 ms] was induced by ventricular programmed electrical stimuli (400/290/270 ms), when the mapping catheter was placed at high anterior RVOT. During VT, the local potential at the high anterior RVOT under the RV-PA conduit was equal to that at the timing of onset of the surface QRS (Fig. 2C). These data may indicate that the high anterior RVOT was near the exit of the VT. The VT was unmappable because the hemodynamics immediately deteriorated during VT, then repeated induction of VT was not tried before CA. Pace mapping and electroanatomical mapping were also tried at the aortic cusp and the left ventricular outflow tract (LVOT) from the right femoral artery. Fractionated potential during sinus rhythm was observed at the noncoronary cusp, and the paced QRS morphology at this site was almost the same as that of the clinical VT, with a delay of 55 ms from pacing to the onset of QRS (Fig. 2D and E). Then, these data may indicate that the noncoronary cusp was near the critical circuit of the VT. However, pace mapping and electroanatomical mapping at the LVOT between the RVOT and the noncoronary cusp, which was the original RVOT and speculated to be the critical site of the VT, was impossible due to the difficulty of catheter manipulation (Fig. 3). Furthermore, the area was a thick calcified lesion; therefore, we did not adhere to the manipulation of the catheter in this area to prevent stroke. Radiofrequency energy was applied at the noncoronary cusp and the high anterior RVOT under the RV-PA conduit with an irrigated catheter (Smart touch SF, Biosense Webster) limited to 35 W for 60 s. After CA, repeated programmed electrical stimulation with isoproterenol infusion could not induce any VT. Given the presence of pre-syncope with the clinical VT and complete TGA, an implantable cardioverter-defibrillator was implanted after the right ventricular pacing lead was extracted. At 12 months of follow-up, the patient remained free from VT.

Fig. 2.

Continued

Fig. 2.

(A) Induced ventricular tachycardia (VT) is similar to clinical VT. (B) Pace mapping at the right ventricular outflow tract (RVOT) under the right ventricle-pulmonary artery (RV-PA) conduit. (C) The local potential at the RVOT under the RV-PA conduit does not proceed from the onset of QRS. (D) Pace mapping of the noncoronary cusp. The stimulus to the onset of QRS is 55 ms. (E) The fractionated potential is recorded at the noncoronary cusp during sinus rhythm.

HRA, high right atrium; CS, coronary sinus; MRV, multipolar right ventricle; RVA, right ventricular apex; ABL, ablation catheter; uni, unipolar; STIM, stimulation.

Fig. 3.

(A) Right ventriculography in right anterior oblique (RAO) view. (B) Left ventriculography in the left anterior oblique (LAO) view. The blue dotted line indicates the ventricular septal defect (VSD) patch dividing the native right ventricular outflow tract (RVOT) into the neoleft ventricular outflow tract (LVOT) and the RVOT.

(C, D) Bipolar (C) and unipolar (D) voltage mapping of the Carto system in the LAO view. The yellow area indicated by the yellow arrows shows the LVOT between the RVOT and the noncoronary cusp, which was the previous RVOT. Mapping in this area is impossible due to the difficulty in catheter manipulation. (E, F) Catheter position in RAO and LAO view.

RV, right ventricle; LV, left ventricle; PA, pulmonary artery; Ao, aorta; CS, coronary sinus; RVA, right ventricular apex. [Author: Please define ‘ABL’]. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Discussion

This is a rare case of successful CA for unmappable VT in a patient with complete TGA who underwent Rastelli repair, which has not been previously reported. CA in patients with CHD is difficult due to various limitations, such as limited access site, intracardiac complicated anatomy, difficult catheter manipulation, and deteriorated hemodynamics. In this rare case, we speculated the exit or the circuit of the unmappable VT and could eliminate the VT. Patients with complete TGA may have a risk of sudden cardiac death. A report on outcomes after the Mustard operation found a sudden cardiac death rate of 10% and all-cause mortality of 20% after 15 years of follow-up [7]. Kammeraad et al. [8] studied risk factors after Senning and Mustard operations in 47 sudden cardiac death cases matched to controls. They found that arrhythmia symptoms and a history of atrial tachycardia increased the risk, but there were no electrocardiographic or Holter markers to distinguish the sudden cardiac death group. In accordance with a previous report, symptoms of palpitation and atrial tachyarrhythmia were detected before the occurrence of VT in the present case. However, the rate of sudden cardiac death or the risk factors of sudden cardiac death in patients with complete TGA after Rastelli repair have not been reported.

Koa-Wing et al. [6] reported a patient with complete TGA who underwent Rastelli repair with an aortic homograft conduit. VT with a cycle length of 590 ms was terminated by CA at the RVOT under the RV-PA conduit. The VT was mappable, and the diastolic potential was recorded. In the present case, sufficient activation mapping of VT was impossible because the hemodynamics deteriorated during VT (TCL = 276 ms). During VT, high anterior RVOT under the RV-PA conduit was the early activation site among the RVs, but it did not precede the onset of QRS. Then, we tried to map the LVOT which was the opposite site of the RVOT. The native RVOT was divided into the new LVOT and the RVOT by VSD patch, then, the new LVOT was a continuous series from the RVOT. The catheter maneuver of the LVOT was extremely difficult, and voltage mapping the sites leading from the RVOT was impossible. The pace mapping of the high anterior RVOT and the noncoronary cusp were similar to spontaneous VT. Based on the stimulus-QRS duration, the high anterior RVOT was thought to be the exit of the VT, and the noncoronary cusp was near the critical site of the VT. CA was then applied at the noncoronary cusp and the high anterior RVOT, and the VT was not induced further. The VT was induced only one time, which was terminated by rapid pacing from right ventricular apex. Then, the mechanism was exactly not known, but based on the background, sustainability (clinically more than one hour), and induction, the reentry was suspected as the mechanism of the VT.

Unmappable VTs are often experienced due to short TCL, low inducibility, deteriorated hemodynamics, and poor general condition in patients with CHD. In these cases, it is important to speculate on the VT circuit from pace mapping and limited activation mapping. In the present case, the VT also had a short TCL, and non-tolerable hemodynamics. However, we speculated the part of the circuit from the pace mapping and limited the activation mapping.

Conclusions

To the best of our knowledge, this is a rare case report of unmappable VT successfully treated using CA in a patient with complete TGA after Rastelli repair.